Common use of The Offer Clause in Contracts

The Offer. (a) As promptly as practicable after the date hereof, but in no event later than ten Business Days after the date hereof, Acquisition Sub shall commence an offer (the "OFFER") to purchase for cash 14,392,003 Shares (which shall include, for purposes of this Agreement, (i) all Shares issuable in respect of exercisable, in-the-money Company Options which have been "conditionally exercised" by the holder thereof for purposes of participating in the Offer, and (ii) all Shares issued prior to the expiration of the Offer upon the conversion of any convertible securities or upon the exercise of any options or warrants) (such number of Shares, the "MAXIMUM NUMBER") at a price of $70.00 per Share, net to the seller in cash (such price, as may hereafter be increased, the "OFFER PRICE"). The obligation of Acquisition Sub to accept for payment any Shares tendered pursuant to the Offer shall be subject only to the conditions set forth in Annex I hereto. The initial expiration date of the Offer shall be the twentieth Business Day following the commencement of the Offer (determined under Rule 14d-1(g)(3) promulgated under the 1934 Act). Acquisition Sub expressly reserves the right to waive any of the conditions to the Offer, modify the terms of the Offer, and increase the Offer Price; PROVIDED that, without the consent of the Company, Acquisition Sub shall not (i) increase or reduce the Maximum Number, (ii) reduce the price per Share to be paid pursuant to the Offer, (iii) add to the conditions set forth in Annex I or modify any condition set forth in Annex I, (iv) change the form of consideration payable in the Offer, or (v) otherwise amend the Offer in any manner adverse to the holders of Shares. Acquisition Sub shall extend the Offer for any period required by any rule, regulation, interpretation or position of the SEC or the staff thereof applicable to the Offer or any period required by applicable law. If any of the conditions to the Offer is not satisfied or waived on any scheduled expiration date of the Offer, Acquisition Sub shall extend the Offer from time to time until such conditions are satisfied or waived; PROVIDED that (i) each such extension of the Offer shall be for a period of not more than ten Business Days, and (ii) Acquisition Sub shall not, without the prior written consent of the Company, extend the Offer beyond the Termination Date. Subject to the foregoing and upon the terms and subject to the conditions of the Offer, Acquisition Sub shall accept for payment and pay for, as promptly as practicable after the expiration of the Offer, all Shares validly tendered and not withdrawn (including if no Shares are validly tendered and not withdrawn), but not in excess of the Maximum Number. (b) As soon as practicable on the date of commencement of the Offer, BMS and Acquisition Sub shall file with the SEC a Tender Offer Statement on Schedule TO (the "SCHEDULE TO") with respect to the Offer (such Schedule TO and such documents included therein pursuant to which the Offer will be made, together with any supplements or amendments thereto, the "OFFER DOCUMENTS"). BMS, Acquisition Sub and the Company each agrees promptly to correct any information provided by it for use in the Offer Documents if and to the extent that such information shall have become false or misleading in any material respect. BMS and Acquisition Sub agree to take all steps necessary to cause the Schedule TO as so corrected to be filed with the SEC. BMS and Acquisition Sub shall deliver or cause to be delivered to the Company, or such other Person as the Company shall designate, the Offer Documents (and any amendments thereto) as so corrected, in such quantities as shall be necessary for dissemination to all holders of Shares and Company Options. The Company shall, at its expense, cause the Offer Documents (and any amendments thereto) to be disseminated to holders of Shares and Company Options, in each case as and to the extent required by applicable federal securities laws. The Company and its counsel shall be given an opportunity to review and comment on the Offer Documents prior to their being filed with the SEC or disseminated to the holders of Shares and Company Options. BMS and Acquisition Sub shall provide the Company and its counsel with any comments or other communications, whether written or oral, that BMS, Acquisition Sub or its counsel may receive from time to time from the SEC or its staff with respect to the Offer Documents promptly after receipt of such comments or other communications. (c) Each certificate for Shares issued to Acquisition Sub representing Shares accepted for purchase and paid for by Acquisition Sub in the Offer shall bear a legend in substantially the following form: THE SECURITIES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO RESTRICTIONS ON TRANSFER AS SET FORTH IN THE STOCKHOLDER AGREEMENT, DATED SEPTEMBER 19, 2001, AMONG IMCLONE SYSTEMS INCORPORATED, ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB COMPANY AND ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB BIOLOGICS COMPANY, A COPY OF WHICH MAY BE OBTAINED FROM THE CORPORATE SECRETARY OF IMCLONE SYSTEMS INCORPORATED.

The Offer. (a) As promptly as practicable after the date hereof, but Provided that this Agreement shall not have been terminated in accordance with Article IX hereof and no event later than ten Business Days after shall have occurred which would result in a failure to satisfy any of the date hereof, Acquisition Sub shall commence an offer conditions set forth in Annex A hereto (the "OFFEROffer Conditions") to purchase for cash 14,392,003 Shares within a reasonable time (which shall include, for purposes but not more than ten business days) after the public announcement of the execution of this Agreement, (i) all Shares issuable in respect of exercisablethe Purchaser shall, in-the-money Company Options which have been "conditionally exercised" by and the holder thereof for purposes of participating in Parent shall cause the Purchaser to, commence the Offer, . The Offer shall be made by means of an offer to purchase (the "Offer to Purchase") containing the terms set forth in this Agreement and (ii) all Shares issued prior to the expiration conditions set forth in Annex A hereto. The obligations of the Purchaser and the Parent to consummate the Offer upon the conversion of any convertible securities or upon the exercise of any options or warrants) (such number of Shares, the "MAXIMUM NUMBER") at a price of $70.00 per Share, net to the seller in cash (such price, as may hereafter be increased, the "OFFER PRICE"). The obligation of Acquisition Sub and to accept for payment any and pur chase the Shares tendered pursuant to the Offer shall be subject only to the conditions set forth in Annex I heretoOffer Conditions. The initial expiration date of the Offer shall be the twentieth Business Day 20th business day following the commencement of the Offer (determined under Rule 14d-1(g)(3) promulgated under the 1934 Act)Offer. Acquisition Sub The Purchaser expressly reserves the right to waive any of the conditions to the Offer, modify the terms of the Offer, and increase the Offer Price; PROVIDED thatPROVIDED, HOWEVER, that without the consent of the Company, Acquisition Sub the Purchaser shall not, and the Parent shall not permit the Purchaser to (i) increase or reduce the Maximum Number, (iiI) reduce the price per Share number of shares of Company Common Stock to be paid pursuant to purchased in the Offer, (iiiII) reduce the Offer Price, (III) materially modify or add to the conditions set forth Offer Conditions, including any change to the Minimum Condition (as defined in Annex I or modify any condition set forth in Annex IA), (ivIV) change the form of consideration payable in the Offer, (V) except as provided below, or (v) otherwise amend the Offer in any manner adverse to the holders of Shares. Acquisition Sub shall extend the Offer for any period as may be required by any rule, regulation, interpretation or position of the SEC or United States Securities and Exchange Commission (the staff thereof applicable to "SEC"), change the expiration date of the Offer or (VI) amend any period required by applicable lawother condition of the Offer in any material respect in a manner adverse to the holders of the Shares. If Notwithstanding anything in this Agreement to the contrary, the Purchaser shall have the right, without the prior consent of the Company, to extend the offer beyond its scheduled expiration date in the following events: (X) if at any expiration date, any of the conditions to the Offer is shall not have been satisfied or waived on any scheduled expiration date of the Offerwaived, Acquisition Sub shall extend the Offer from time to time until such conditions are satisfied or waived; PROVIDED that (iY) each such extension for any period required by applicable law; and (Z) if all of the Offer shall be for a period of not more than ten Business Days, and (ii) Acquisition Sub shall not, without the prior written consent of the Company, extend conditions to the Offer beyond are satisfied or waived, but the Termination Date. Subject to the foregoing and upon the terms and subject to the conditions number of the Offer, Acquisition Sub shall accept for payment and pay for, as promptly as practicable after the expiration of the Offer, all Shares validly tendered and not withdrawn (including if no is less than the amount necessary to effect a parent-subsidiary merger pursuant to Section 252 of the Delaware General Corporation, for a period not to exceed twenty days following the initial expiration date of the Offer. The Offer Conditions are for the sole benefit of the Parent and the Purchaser and may be asserted by the Parent and the Purchaser regardless of the circumstances giving rise to any such Offer Conditions and, subject to the preceding sentence, may be waived by the Purchaser in whole or in part. Subject only to the Offer Conditions, the Purchaser shall, and the Parent shall cause the Purchaser to, pay for all of the Shares are validly tendered and not withdrawnwithdrawn pursuant to the Offer (including any subsequent offering period) as soon as legally permissible. In the event that (i) the Minimum Condition (as defined in Annex A) has not been satisfied or (ii) any condition set forth in paragraph (a), but (d) or (e) of Annex A is not in excess satisfied or waived at the scheduled expiration date of the Maximum NumberOffer, at the reasonable request of the Company, Purchaser shall, and Parent shall cause Purchaser to, extend the expiration date of the Offer in increments of five business days each until the earliest to occur of (1) the satisfaction or waiver of such condition, (2) Parent reasonably determining that such condition to the Offer is not capable of being satisfied on or prior to the thirtieth day following the initial expiration date of the Offer, (3) the termination of this Agreement in accordance with its terms and (4) the thirtieth day following the initial expiration date of the Offer. (b) As Provided that this Agreement shall not have been terminated in accordance with Article IX hereof and no event shall have occurred which would result in a failure to satisfy any of the Offer Conditions, the Parent and the Purchaser will file with the SEC, as soon as practicable on after the date of commencement of the Offerhereof, BMS and Acquisition Sub shall file with the SEC a Tender Offer Statement on Schedule Sched ule TO (the "SCHEDULE TO") with respect to the Offer (such Schedule TO and such documents included therein pursuant to which the Offer will be made, together with any all supplements or amendments thereto, and including all exhibits, the "OFFER DOCUMENTSOffer Documents"). BMSEach of Parent, Acquisition Sub Purchaser and the Company each agrees shall promptly to correct any information provided by it for use use, or incorporated by reference, in the Offer Documents if and to the extent that such information shall have become false or misleading in any material respect. BMS , and Acquisition Sub agree to each of Parent and Purchaser shall take all steps necessary to amend or supplement the Offer Documents and to cause the Schedule TO Offer Documents as so corrected amended or supplemented to be filed with the SEC. BMS SEC and Acquisition Sub shall deliver or cause to be delivered to the Company, or such other Person as the Company shall designate, the Offer Documents (and any amendments thereto) as so corrected, in such quantities as shall be necessary for dissemination to all holders of Shares and Company Options. The Company shall, at its expense, cause the Offer Documents (and any amendments thereto) to be disseminated to holders of Shares and Company Optionsthe Company's shareholders, in each case as and to the extent required by applicable federal Federal securities laws. The Parent and the Purchaser shall give the Company and its counsel shall be given an a reasonable opportunity to review and comment on the Offer Documents prior to their being filed with the SEC or disseminated to the holders stockholders of Shares the Company. The Parent and Company Options. BMS and Acquisition Sub shall provide the Purchaser will furnish the Company and its counsel in writing with any comments that the Parent, the Purchaser or other communications, whether written or oral, that BMS, Acquisition Sub or its their counsel may receive from time to time from the SEC or its staff with respect to the Offer Documents Documents, promptly after receipt of such comments or other communications. (c) Each certificate for Shares issued and shall provide the Company and its counsel with a reasonable opportunity to Acquisition Sub representing Shares accepted for purchase and paid for by Acquisition Sub participate in the Offer shall bear a legend in substantially response of the following form: THE SECURITIES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO RESTRICTIONS ON TRANSFER AS SET FORTH IN THE STOCKHOLDER AGREEMENT, DATED SEPTEMBER 19, 2001, AMONG IMCLONE SYSTEMS INCORPORATED, ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB COMPANY AND ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB BIOLOGICS COMPANY, A COPY OF WHICH MAY BE OBTAINED FROM THE CORPORATE SECRETARY OF IMCLONE SYSTEMS INCORPORATEDParent or the Purchaser to such comments.

The Offer. (a) As promptly as practicable after Subject to the date hereof, but in no event later than ten Business Days after the date hereof, Acquisition Sub shall commence an offer (the "OFFER") to purchase for cash 14,392,003 Shares (which shall include, for purposes provisions of this Agreement, as promptly as practicable, and in any event no more than seven (i7) all Shares issuable in respect Business Days, after the date of exercisablethis Agreement, in-the-money Company Options which have been "conditionally exercised" by Merger Subsidiary shall, and Parent shall cause Merger Subsidiary to, commence, within the holder thereof for purposes meaning of participating in Rule l4d-2 under the Exchange Act, the Offer, and (ii) all Shares issued prior to the expiration of the Offer upon the conversion of any convertible securities or upon the exercise of any options or warrants) (such number of Shares, the "MAXIMUM NUMBER") at a price of $70.00 per Share, net to the seller in cash (such price, as may hereafter be increased, the "OFFER PRICE"). The obligation of Acquisition Sub Merger Subsidiary to, and of Parent to cause Merger Subsidiary to, accept for payment and pay for any Shares tendered pursuant to the Offer shall be subject only to the satisfaction of the conditions set forth in Annex I hereto. The initial expiration date A and to the terms and conditions of the Offer shall be the twentieth Business Day following the commencement of the Offer (determined under Rule 14d-1(g)(3) promulgated under the 1934 Act). Acquisition Sub expressly reserves the right to this Agreement; provided that Parent and Merger Subsidiary may waive any of the conditions to the Offer, modify Offer (except for the Minimum Tender Condition which may not be waived without the prior written consent of the Company) and may make changes in the terms and conditions of the Offer, and increase the Offer Price; PROVIDED except that, without the prior written consent of the Company, Acquisition Sub shall not (i) increase or reduce no change may be made to the Maximum Numberform of consideration to be paid, (ii) reduce no decrease in the price per Share to Offer Price or the number of Shares sought in the Offer may be paid pursuant to the Offermade, (iii) add no change which imposes additional conditions to the Offer or modifies any of the conditions set forth in Annex I or modify any condition set forth in Annex I, (iv) change the form of consideration payable in the Offer, or (v) otherwise amend the Offer A in any manner adverse to the holders of the Shares may be made and (iv) neither Parent nor Merger Subsidiary may extend the Offer, except in accordance with Section 2.1(c) or 2.1(e). (b) On the date of commencement of the Offer, Parent and Merger Subsidiary shall file with the SEC a Tender Offer Statement on Schedule TO (as amended and supplemented from time to time, the “Schedule TO”), which shall comply in all material respects with the provisions of applicable federal securities Laws, and shall contain the offer to purchase relating to the Offer and forms of the related letter of transmittal and other appropriate documents (which documents, as amended or supplemented from time to time, are referred to herein collectively as the “Offer Documents”). Parent and the Merger Subsidiary further agree to disseminate the Offer Documents to holders of Shares as and to the extent required by applicable federal securities Laws. In conducting the Offer, Parent and the Merger Subsidiary shall comply in all material respects with the provisions of the Exchange Act and any other applicable Laws necessary to be complied with in connection with the Offer. The Company shall promptly furnish to Parent and Merger Subsidiary all information concerning the Company and its Subsidiaries and the Company’s stockholders that may be required or reasonably requested in connection with any action contemplated by this Section 2.1. The Company and its counsel shall be given a reasonable opportunity to review and comment on the Offer Documents prior to their filing with the SEC, and Parent and Merger Subsidiary shall give reasonable and good faith consideration to any comments made by the Company and its counsel. Parent and Merger Subsidiary agree to provide the Company (i) any comments that may be received from the SEC or its staff (whether written or oral) with respect to the Offer Documents promptly after receipt thereof and prior to responding thereto and (ii) a reasonable opportunity to participate in the response of Parent and Merger Subsidiary to these comments and to provide comments on that response (to which reasonable and good faith consideration shall be given), including by participating with Parent and Merger Subsidiary or their counsel in any discussions or meetings with the SEC. Each of Parent, Merger Subsidiary and the Company agrees promptly to correct any information provided by it for use in the Offer Documents if and to the extent that it shall have become false or misleading in any material respect, and Parent and Merger Subsidiary further agree to take all steps necessary to cause the Offer Documents as so corrected to be filed with the SEC and be disseminated to holders of Shares. Acquisition Sub , in each case, as and to the extent required by Law. (c) The initial scheduled expiration date of the Offer shall be midnight, New York City time, on the twentieth Business Day after (for this purpose calculated in accordance with Rule 14d-1(g)(3) under the Exchange Act) the date of its commencement (such initial date, or if and only if the expiration time and date is extended as authorized in this Agreement, such date as so extended, the “Expiration Date”); provided, however, that Merger Subsidiary shall: (i) from time to time extend the Offer for one or more periods of up to 10 Business Days each, the length of each such period to be determined by Merger Subsidiary in its sole discretion, if at the scheduled Expiration Date any of the conditions of the Offer, including the Minimum Tender Condition and the conditions and requirements set forth on Annex A (other than conditions which by their nature are to be satisfied at the closing of the Offer), shall not have been satisfied or waived, until such time as such conditions are satisfied or waived to the extent permitted by this Agreement or (ii) extend the Offer for any period required by any rule, regulation, interpretation or position of the SEC or the staff thereof applicable to the Offer or any period required by applicable lawOffer. If any Subject to the terms and conditions of the conditions Offer and this Agreement, Merger Subsidiary shall, and Parent shall cause Merger Subsidiary to, accept for payment and pay for Shares validly tendered and not withdrawn pursuant to the Offer is not satisfied or waived on any scheduled expiration date as soon as possible after the Expiration Date. (d) If fewer than 90% of the Offer, Acquisition Sub shall extend issued and outstanding Shares are accepted for payment pursuant to the Offer from time to time until such conditions are satisfied or waived; PROVIDED that (i) each such extension of by the Offer shall be for a period of not more than ten Business DaysExpiration Date, then Merger Subsidiary may, and (ii) Acquisition Sub shall not, without at the prior written consent request of the Company, shall, and upon any such request of the Company, Parent shall cause Merger Subsidiary to, provide for one or more subsequent offering periods of up to an additional twenty (20) Business Days in the aggregate (collectively, the “Subsequent Period”) pursuant to Rule 14d-11 of the Exchange Act; provided that Merger Subsidiary shall immediately accept and promptly pay for all Shares as they are tendered during any Subsequent Period. (e) Notwithstanding the above, in no event shall Merger Subsidiary be required to, or shall Parent be required to cause Merger Subsidiary to, extend the Offer beyond the Termination DateEnd Date (as defined in Section 8.1(b)(i)). Subject to In no event shall Merger Subsidiary extend the foregoing and upon Offer beyond the terms and subject to End Date without the conditions consent of the Offer, Acquisition Sub shall accept for payment and pay for, Company. The Offer may not be terminated prior to its scheduled Expiration Date (as promptly as practicable after the expiration of the Offer, all Shares validly tendered and not withdrawn (including if no Shares are validly tendered and not withdrawn), but not it may be extended in excess of the Maximum Numberaccordance with this Agreement) unless this Agreement is terminated in accordance with Section 8.1. (bf) As soon as practicable on the date of commencement of the Offer, BMS and Acquisition Sub Parent shall file with the SEC a Tender Offer Statement on Schedule TO (the "SCHEDULE TO") with respect to the Offer (such Schedule TO and such documents included therein pursuant to which the Offer will be made, together with any supplements or amendments thereto, the "OFFER DOCUMENTS"). BMS, Acquisition Sub and the Company each agrees promptly to correct any information provided by it for use in the Offer Documents if and to the extent that such information shall have become false or misleading in any material respect. BMS and Acquisition Sub agree to take all steps necessary to cause the Schedule TO as so corrected to be filed with the SEC. BMS and Acquisition Sub shall deliver provide or cause to be delivered provided to Merger Subsidiary on a timely basis the funds necessary to purchase any Shares that Merger Subsidiary becomes obligated to purchase pursuant to the Company, or such other Person as the Company shall designate, the Offer Documents (and any amendments thereto) as so corrected, in such quantities as shall be necessary for dissemination to all holders of Shares and Company Options. The Company shall, at its expense, cause the Offer Documents (and any amendments thereto) to be disseminated to holders of Shares and Company Options, in each case as and to the extent required by applicable federal securities laws. The Company and its counsel shall be given an opportunity to review and comment on the Offer Documents prior to their being filed with the SEC or disseminated to the holders of Shares and Company Options. BMS and Acquisition Sub shall provide the Company and its counsel with any comments or other communications, whether written or oral, that BMS, Acquisition Sub or its counsel may receive from time to time from the SEC or its staff with respect to the Offer Documents promptly after receipt of such comments or other communicationsOffer. (c) Each certificate for Shares issued to Acquisition Sub representing Shares accepted for purchase and paid for by Acquisition Sub in the Offer shall bear a legend in substantially the following form: THE SECURITIES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO RESTRICTIONS ON TRANSFER AS SET FORTH IN THE STOCKHOLDER AGREEMENT, DATED SEPTEMBER 19, 2001, AMONG IMCLONE SYSTEMS INCORPORATED, ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB COMPANY AND ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB BIOLOGICS COMPANY, A COPY OF WHICH MAY BE OBTAINED FROM THE CORPORATE SECRETARY OF IMCLONE SYSTEMS INCORPORATED.

The Offer. (a) As promptly as practicable after Subject to the date hereof, but in no event later than ten Business Days after the date hereof, Acquisition Sub shall commence an offer (the "OFFER") to purchase for cash 14,392,003 Shares (which shall include, for purposes conditions of this Agreement, (i) all Shares issuable in respect of exercisable, in-the-money Company Options which have been "conditionally exercised" by the holder thereof for purposes of participating in the OfferMerger Sub shall, and Parent shall cause Merger Sub to, use commercially reasonable efforts to commence within three (ii3) all Shares issued prior to Business Days (and in any event Merger Sub shall, and Parent shall cause Merger Sub to, commence within ten (10) Business Days), the expiration Offer within the meaning of the Offer upon applicable rules and regulations of the conversion of any convertible securities or upon Securities and Exchange Commission (the exercise of any options or warrants) (such number of Shares, the "MAXIMUM NUMBER") at a price of $70.00 per Share, net to the seller in cash (such price, as may hereafter be increased, the "OFFER PRICE"“SEC”). The obligation obligations of Acquisition Merger Sub to, and of Parent to cause Merger Sub to, accept for payment payment, and pay for, any Shares shares of the Company Common Stock tendered pursuant to the Offer shall be are subject only to the conditions set forth in Annex I heretoExhibit C as such conditions may be modified in accordance with the express terms of this Agreement. The initial expiration date of the Offer shall be midnight (New York City time) on the twentieth Business Day (20th) business day following the commencement of the Offer (determined under using Rule 14d-1(g)(3) of the Securities Exchange Act of 1934, as amended (together with the rules and regulations promulgated under thereunder, the 1934 “Exchange Act”)). Acquisition Merger Sub expressly reserves the right in its sole discretion to waive waive, in whole or in part, any of the conditions condition to the Offer, Offer or modify the terms of the Offer, and increase the Offer Price; PROVIDED except that, without the written consent of the Company, Acquisition Merger Sub shall not (i) increase or reduce the Maximum Numbernumber of shares of the Company Common Stock subject to the Offer, (ii) reduce the price per Share to be paid pursuant to the OfferOffer Price, (iii) waive or amend the Minimum Tender Condition, (iv) add to the conditions set forth in Annex I Exhibit C or modify any condition set forth in Annex IExhibit C in any manner adverse to the holders of the Company Common Stock, (ivv) except as otherwise provided in this Section 1.01(a), extend the Offer, (vi) change the form of consideration payable in the Offer, Offer or (vvii) otherwise amend the Offer in any manner adverse to the holders of Sharesthe Company Common Stock. Acquisition The parties hereto agree to cooperate in good faith to modify the terms of the Offer as and if required by the SEC. Notwithstanding any provision of this Agreement to the contrary, Merger Sub shall extend the Offer for any the minimum period required by any rule, regulation, interpretation or position of the SEC or the staff thereof applicable to the Offer); provided, however, that Merger Sub shall not be required to, and Parent shall not be required to cause Merger Sub to, extend the Offer or any period required by applicable lawbeyond the Outside Date. If any In addition, unless this Agreement has been terminated in accordance with its terms, if at the otherwise scheduled expiration date of the conditions Offer any condition to the Offer is not satisfied satisfied, Merger Sub shall, and Parent shall cause Merger Sub to, extend the Offer for one (1) or waived on any scheduled expiration date more consecutive increments of not more than ten (10) Business Days each (or for such longer period as may be agreed by the Company); provided, however, that Merger Sub shall not be required to, and Parent shall not be required to cause Merger Sub to, extend the Offer beyond the Outside Date. Upon the mutual written consent of the Offerparties hereto, Acquisition each in its sole discretion, Merger Sub shall extend the Offer from time to time until such conditions are satisfied on one or waived; PROVIDED that (i) each such extension of the Offer shall be more occasions for a an aggregate period of not more than ten (10) Business DaysDays each to the extent that, on such expiration date, all conditions to the Offer are satisfied but the shares of Company Common Stock that have been validly tendered and not validly withdrawn pursuant to the Offer, considered together with all other shares of Company Common Stock owned by Parent and its subsidiaries, shall constitute less than ninety percent (ii90%) Acquisition Sub shall not, without the prior written consent of the Company, extend outstanding shares of Company Common Stock. If all of the conditions set forth in Exhibit C are satisfied but the number of shares of the Company Common Stock that have been validly tendered and not withdrawn in the Offer beyond and accepted for payment, together with any shares of the Termination DateCompany Common Stock then owned by Parent or Merger Sub, is less than ninety percent (90%) of the outstanding shares of the Company Common Stock, Merger Sub may in its sole discretion make available one (1) or more “subsequent offering periods”, in accordance with Rule 14d-11 of the Exchange Act, of not less than ten (10) Business Days and not more than twenty (20) Business Days in the aggregate for all subsequent offering periods. Subject to the foregoing and upon On the terms and subject to the conditions of the OfferOffer and this Agreement, Acquisition Merger Sub shall, and Parent shall cause Merger Sub to, accept for payment and pay for, as for (subject to any withholding of Tax pursuant to Section 2.02(h)) all shares of the Company Common Stock validly tendered and not validly withdrawn pursuant to the Offer that Merger Sub becomes obligated to purchase pursuant to the Offer promptly as practicable after the expiration of the Offer, all Shares validly tendered Offer (as it may be extended and not withdrawn (including if no Shares are validly tendered and not withdrawnre-extended in accordance with this Section 1.01(a), but not ). Nothing contained in excess of the Maximum Numberthis Section 1.01(a) shall affect any termination rights in Article VIII. (b) As soon as practicable on On the date of commencement of the Offer, BMS Parent and Acquisition Merger Sub shall file with the SEC SEC, pursuant to and in accordance with Rule 14d-3 and Regulation M-A under the Exchange Act, a Tender Offer Statement on Schedule TO (the "SCHEDULE TO") with respect to the Offer Offer, which shall contain an offer to purchase and a related letter of transmittal and summary advertisement (such Schedule TO and such the documents included therein pursuant to which the Offer will shall be made, together with any supplements or amendments thereto, the "OFFER DOCUMENTS"“Offer Documents”). BMSParent and Merger Sub agree to take all steps necessary to cause the Offer Documents to be disseminated to holders of shares of the Company Common Stock as and to the extent required by the Exchange Act. The Company shall promptly furnish to Parent and Merger Sub all information concerning the Company required by the Exchange Act to be set forth in the Offer Documents or reasonably requested by Parent and Merger Sub for inclusion therein. Each of Parent, Acquisition Merger Sub and the Company each agrees shall promptly to correct any information provided by it for use in the Offer Documents if and to the extent that such information shall have become false or misleading in any material respect. BMS respect and Acquisition to correct any material omissions therein; and each of Parent and Merger Sub agree to shall take all steps necessary to amend or supplement the Offer Documents and to cause the Schedule TO Offer Documents, as so corrected amended or supplemented, to be filed with the SEC. BMS SEC and Acquisition Sub shall deliver or cause to be delivered to the Company, or such other Person as the Company shall designate, the Offer Documents (and any amendments thereto) Documents, as so correctedamended or supplemented, in such quantities as shall be necessary for dissemination to all holders of Shares and Company Options. The Company shall, at its expense, cause the Offer Documents (and any amendments thereto) to be disseminated to holders of Shares and Company Optionsthe Company’s stockholders, in each case as and to the extent required by applicable federal Federal securities laws. The Company Parent and its counsel shall be given an opportunity to review and comment on the Offer Documents prior to their being filed with the SEC or disseminated to the holders of Shares and Company Options. BMS and Acquisition Merger Sub shall provide the Company and its counsel with copies of any written comments, and shall inform the Company and its counsel of any oral comments or other communications, whether written or oraldiscussions, that BMSParent, Acquisition Merger Sub or its their counsel may receive from time to time from or engage in with the SEC or its staff with respect to the Offer Documents promptly after the receipt of such comments or other communicationsthe commencement or occurrence of any such discussions. Prior to the filing of the Offer Documents (including any amendment or supplement thereto) with the SEC or the dissemination thereof to the stockholders of the Company, or responding to any comments of the SEC with respect to the Offer Documents, Parent and Merger Sub shall provide the Company and its counsel a reasonable opportunity to review and comment on such Offer Documents or response (including the proposed final version thereof), and Parent and Merger Sub shall give reasonable and good faith consideration to any comments made by the Company or its counsel. (c) Each certificate for Shares issued Parent shall provide or cause to Acquisition be provided to Merger Sub representing Shares accepted for on a timely basis the funds necessary to purchase and paid for by Acquisition any shares of the Company Common Stock that Merger Sub becomes obligated to purchase pursuant to the Offer. (d) Merger Sub shall not terminate the Offer prior to any scheduled expiration thereof without the prior written consent of the Company, except in the event that this Agreement is terminated pursuant to Article VIII. In the event that this Agreement is terminated pursuant to Article VIII prior to any scheduled expiration thereof, Merger Sub shall (and Parent shall cause Merger Sub to) promptly (and in any event within twenty-four (24) hours of such termination), irrevocably and unconditionally terminate the Offer. If the Offer is terminated or withdrawn by Merger Sub, or this Agreement is terminated prior to the purchase of shares of the Company Common Stock in the Offer, Merger Sub shall bear a legend in substantially promptly return, and shall cause any depository acting on behalf of Merger Sub to return, all tendered shares of the following form: THE SECURITIES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO RESTRICTIONS ON TRANSFER AS SET FORTH IN THE STOCKHOLDER AGREEMENT, DATED SEPTEMBER 19, 2001, AMONG IMCLONE SYSTEMS INCORPORATED, ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB COMPANY AND ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB BIOLOGICS COMPANY, A COPY OF WHICH MAY BE OBTAINED FROM THE CORPORATE SECRETARY OF IMCLONE SYSTEMS INCORPORATEDCompany Common Stock to the registered holders thereof.

The Offer. (a) As Provided that this Agreement shall not have been terminated in accordance with Section 9.1 and no event set forth in paragraphs (a) through (h) in Annex A hereto shall have occurred and be continuing, Merger Sub shall, and Parent shall cause Merger Sub to, commence (within the meaning of Rule 14d-2 under the Exchange Act) the Offer as promptly as practicable after the date hereof, but and in any event no event later than ten Business Days after the date hereofJanuary 18, Acquisition Sub 2008. The Offer Price shall commence an offer (the "OFFER") to purchase for cash 14,392,003 Shares (which shall include, for purposes of this Agreement, (i) all Shares issuable in respect of exercisable, in-the-money Company Options which have been "conditionally exercised" by the holder thereof for purposes of participating in the Offer, and (ii) all Shares issued prior to the expiration of the Offer upon the conversion of any convertible securities or upon the exercise of any options or warrants) (such number of Shares, the "MAXIMUM NUMBER") at a price of $70.00 per Share, be net to the seller of shares of Common Stock in cash the Offer in cash, without interest, subject to reduction for applicable amounts withheld pursuant to paragraph (such price, as may hereafter f) below. The Company agrees that no shares of Common Stock held by the Company or any of its Subsidiaries will be increased, tendered pursuant to the "OFFER PRICE")Offer. The obligation of Acquisition Merger Sub to accept for payment and to pay for any Shares shares of Common Stock tendered pursuant to the Offer shall be subject only to the those conditions set forth in Annex I hereto. The initial expiration date of A hereto (as they may be amended in accordance with this Agreement, the “Offer shall be the twentieth Business Day following the commencement of the Offer Conditions”). (determined under Rule 14d-1(g)(3b) promulgated under the 1934 Act). Acquisition Merger Sub expressly reserves the right right, in its sole discretion, to waive any of the conditions to the Offer, modify Offer Conditions and make any other changes in the terms and conditions of the Offer, and increase the Offer Price; PROVIDED provided that, without the prior written consent of the Company, Acquisition Merger Sub shall not (i) increase decrease the Offer Price or reduce the Maximum Number, (ii) reduce the price per Share to be paid pursuant to the Offer, (iii) add to the conditions set forth in Annex I or modify any condition set forth in Annex I, (iv) change the form of consideration payable in the Offer, (ii) decrease the number of shares of Common Stock sought to be purchased in the Offer, (iii) amend the number of shares of Common Stock required to satisfy the Minimum Condition except in accordance with Section 7.2(e) hereof or waive satisfaction of the Minimum Condition, (iv) impose additional conditions on the Offer or (v) otherwise amend any other term of the Offer in any manner adverse in any material respect to the holders of Shares. Acquisition Sub shall extend the Offer for any period required by any rule, regulation, interpretation or position shares of the SEC or the staff thereof applicable to the Offer or any period required by applicable law. If any of the conditions to the Offer is not satisfied or waived on any scheduled expiration date of the Offer, Acquisition Sub shall extend the Offer from time to time until such conditions are satisfied or waived; PROVIDED that (i) each such extension of the Offer shall be for a period of not more than ten Business Days, and (ii) Acquisition Sub shall not, without the prior written consent of the Company, extend the Offer beyond the Termination Date. Subject to the foregoing and upon the terms and subject to the conditions of the Offer, Acquisition Sub shall accept for payment and pay for, as promptly as practicable after the expiration of the Offer, all Shares validly tendered and not withdrawn (including if no Shares are validly tendered and not withdrawn), but not in excess of the Maximum NumberCommon Stock. (bc) As soon as practicable on On the date of commencement of the Offer, BMS Parent and Acquisition Merger Sub shall (i) file or cause to be filed with the SEC a combined Schedule 13E-3 and Tender Offer Statement on Schedule TO (the "SCHEDULE TO") with respect to the Offer (such filed under cover of Schedule TO (together with all amendments and such supplements thereto, the “Schedule TO”) and related offer to purchase, letter of transmittal and summary advertisement and other ancillary Offer documents included therein and instruments pursuant to which the Offer will be mademade (collectively, together with and including any supplements or amendments thereto, the "OFFER DOCUMENTS")“Offer Documents”) and (ii) cause the Offer Documents to be disseminated to the holders of Common Stock as and to the extent required by applicable Law. BMSThe Company agrees to furnish to Parent and Merger Sub all information concerning the Company required by applicable Law to be set forth in the Offer Documents. Parent, Acquisition Merger Sub and the Company each agrees promptly to correct any information provided by it for use in the Offer Documents if and to the extent that such information it shall have become false or misleading in any material respect. BMS , and Acquisition Merger Sub agree to shall take all steps necessary to cause the Schedule TO TO, as so corrected or supplemented, to be filed with the SEC. BMS SEC and Acquisition Sub shall deliver or cause to be delivered to the Company, or such other Person as the Company shall designate, the Offer Documents (and any amendments thereto) Documents, as so correctedcorrected or supplemented, in such quantities as shall be necessary for dissemination to all holders of Shares and Company Options. The Company shall, at its expense, cause the Offer Documents (and any amendments thereto) to be disseminated to holders of Shares and Company OptionsCommon Stock, in each case as and to the extent required by applicable federal Federal securities laws. The Parent will provide the Company and its counsel shall be given an a reasonable opportunity to review and comment on the Offer Documents prior to their being Documents, and any amendments thereto, before they are filed with the SEC or disseminated to the holders of Shares Common Stock. Parent and Company Options. BMS and Acquisition Merger Sub shall provide the Company and its counsel with respond as promptly as reasonably practicable to any comments or other communications, whether written or oral, that BMS, Acquisition Sub or its counsel may receive from time to time received from the SEC or its staff with respect to the Offer Documents promptly after receipt and provide copies of such comments to the Company promptly upon receipt and copies of proposed responses to the Company a reasonable time prior to filing or other communicationsdisseminating to allow meaningful comment. (cd) Each certificate The Offer shall remain open until that date that is twenty (20) Business Days following (and including the day of) the commencement of the Offer (such date, or such subsequent date to which the expiration of the Offer is extended pursuant to and in accordance with the terms of this Agreement, the “Expiration Date”). Unless this Agreement has been terminated in accordance with Section 9.1, if at any scheduled Expiration Date, any of the Offer Conditions shall not have been satisfied or earlier waived by Merger Sub, or, even if all of the Offer Conditions shall have been satisfied or waived, if the Financing Documentation Deadline shall not have occurred, then Merger Sub shall extend the Offer and the Expiration Date on one or more occasions for Shares issued periods of up to Acquisition twenty (20) Business Days as Merger Sub representing Shares accepted shall determine; provided, however, that (i) if all of the Offer Conditions have been satisfied or waived by Merger Sub for purchase at least ten (10) Business Days other than the Minimum Condition, then Merger Sub shall not be required to extend the Expiration Date beyond the four (4) month anniversary of the day of the commencement of the Offer and (ii) in no event shall Merger Sub be required to extend the Offer or the Expiration Date beyond the Outside Date. Merger Sub may, in its sole discretion, elect to provide a subsequent offering period for the Offer in accordance with Rule 14d-11 promulgated under the Exchange Act (“Subsequent Offering Period”) if as of the commencement of the Subsequent Offering Period, there shall not have been validly tendered and not withdrawn pursuant to the Offer that number of shares of Common Stock necessary to permit the Merger to be effected without a meeting of stockholders of the Company, in accordance with Section 253 of the Act. Nothing contained in this Section 1.1(d) shall be construed to affect any termination rights set forth in Article IX hereof. (e) Subject to the terms of the Offer and this Agreement and the satisfaction or waiver by Merger Sub of the Offer Conditions as of the Expiration Date, following the occurrence of the Financing Documentation Deadline and in accordance with Rule 14d-11, Merger Sub shall (i) accept for payment (“Acceptance” and the time and date of such Acceptance, the “Acceptance Date”) and pay for shares of Common Stock validly tendered and not validly withdrawn pursuant to the Offer promptly after the Expiration Date and (ii) as promptly as practicable, accept for payment and pay for all shares of Common Stock validly tendered into any Subsequent Offering Period. (f) Merger Sub shall be entitled to deduct and withhold from the consideration otherwise payable pursuant to the Offer to any holder of shares of Common Stock such amounts as Merger Sub is required to deduct and withhold with respect to the making of such payment under the Code, or any provision of state, local or foreign Tax Law. To the extent that amounts are so withheld and paid over to the appropriate Tax authority by Merger Sub, such withheld amounts shall be treated for all purposes of the Agreement as having been paid to the holder of the shares of Common Stock in respect of which such deduction and withholding were made by Acquisition Merger Sub. (g) Merger Sub shall not terminate the Offer prior to any next scheduled Expiration Date without the prior written consent of the Company except in the Offer shall bear a legend event the Agreement is terminated in substantially the following form: THE SECURITIES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO RESTRICTIONS ON TRANSFER AS SET FORTH IN THE STOCKHOLDER AGREEMENT, DATED SEPTEMBER 19, 2001, AMONG IMCLONE SYSTEMS INCORPORATED, ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB COMPANY AND ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB BIOLOGICS COMPANY, A COPY OF WHICH MAY BE OBTAINED FROM THE CORPORATE SECRETARY OF IMCLONE SYSTEMS INCORPORATEDaccordance with Section 9.1.

The Offer. (a) As Provided that this Agreement shall not have been terminated in accordance with Section 8.1 and that none of the events set forth in Paragraph (2) of Annex I hereto shall exist or have occurred and be continuing, as promptly as practicable after the date hereof, but in no event later than ten Business Days after March 2, 2007, Merger Sub shall, and Parent shall cause Merger Sub to, commence (within the date hereof, Acquisition Sub shall commence an offer (meaning of Rule 14d-2 under the "OFFER"Exchange Act) the Offer to purchase for cash 14,392,003 Shares (which shall include, for purposes any and all of this Agreement, (i) all Shares issuable in respect the outstanding shares of exercisable, in-the-money Company Options which have been "conditionally exercised" by Common Stock at the holder thereof for purposes Offer Price. The obligations of participating in the OfferMerger Sub to, and (ii) all Shares issued prior of Parent to the expiration of the Offer upon the conversion of any convertible securities or upon the exercise of any options or warrants) (such number of Sharescause Merger Sub to, the "MAXIMUM NUMBER") at a price of $70.00 per Share, net to the seller in cash (such price, as may hereafter be increased, the "OFFER PRICE"). The obligation of Acquisition Sub to accept for payment any Shares and pay for shares of Company Common Stock tendered pursuant to the Offer shall be subject only to the conditions set forth in Annex I hereto. The initial expiration date of hereto (the “Offer shall be the twentieth Business Day following the commencement of the Offer (determined under Rule 14d-1(g)(3) promulgated under the 1934 ActConditions”). Acquisition Merger Sub expressly reserves the right to waive any of the conditions Offer Conditions and to the Offer, modify make any change in the terms of the Offer, and increase except that without the prior written consent of the Company, Merger Sub shall not (A) decrease the Offer Price; PROVIDED thatPrice or change the form of the consideration payable in the Offer, (B) decrease the number of shares of Company Common Stock sought pursuant to the Offer, (C) amend or waive the condition set forth in paragraph 1(a) of Annex I, (D) add to the conditions set forth on Annex I, (E) modify the conditions set forth in Annex I in a manner adverse to the holders of shares of Company Common Stock, (F) extend the Expiration Date (as defined in Annex I) except as required or permitted by this Section 1.1(a), or (G) make any other change in the terms or conditions of the Offer which is adverse to the holders of shares of Company Common Stock. The initial Expiration Date shall be the twentieth business day following (and including the day of) the commencement of the Offer. If any of the Offer Conditions is not satisfied or waived on any scheduled Expiration Date, if such Offer Condition(s) could reasonably be expected to be satisfied, Merger Sub shall extend the Offer from time to time until such Offer Condition(s) are satisfied or waived. Any individual extension of the Offer pursuant to the preceding sentence shall not exceed 10 business days and in no event shall the Offer extend beyond the Walk-Away Date without the mutual written consent of the Company and Parent. Notwithstanding the foregoing, without the consent of the Company, Acquisition Merger Sub shall not (i) increase or reduce have the Maximum Number, (ii) reduce the price per Share right to be paid pursuant to the Offer, (iii) add to the conditions set forth in Annex I or modify any condition set forth in Annex I, (iv) change the form of consideration payable in the Offer, or (v) otherwise amend the Offer in any manner adverse to the holders of Shares. Acquisition Sub shall extend the Offer for any period required by any rule, regulation, interpretation or position of the SEC or the staff thereof applicable to the Offer or any period required by applicable lawLaw. If any of the conditions to the Offer is not satisfied or waived on any scheduled Following expiration date of the Offer, Acquisition Merger Sub shall extend may, in its sole discretion, provide a subsequent offering period (the Offer from time to time until such conditions are satisfied or waived; PROVIDED that (i“Subsequent Offering Period”) each such extension in accordance with Rule 14d-11 of the Offer shall be for a period of not more than ten Business Days, and (ii) Acquisition Sub shall not, without the prior written consent of the Company, extend the Offer beyond the Termination DateExchange Act. Subject to the foregoing foregoing, and upon the terms and subject to the conditions satisfaction, or waiver by Merger Sub, of the Offer Conditions as of the time of any scheduled expiration of the Offer, Acquisition Merger Sub shall, and Parent shall cause it to, accept for payment payment, as promptly as permitted under applicable securities laws, and pay for, as promptly as practicable after the expiration date on which Merger Sub first accepts shares of Company Common Stock for payment pursuant to the OfferOffer (the “Acceptance Date”), all Shares shares of Company Common Stock (i) validly tendered and not withdrawn pursuant to the Offer and (including if no Shares are ii) validly tendered in the Subsequent Offering Period. Parent shall provide or cause to be provided to Merger Sub on a timely basis funds necessary to purchase all shares of Company Common Stock that Merger Sub becomes obligated to purchase pursuant to the Offer and not withdrawn), but not in excess of the Maximum NumberMerger Sub shall maintain such funds exclusively for such purpose. (b) As soon as practicable on On the date of commencement of the Offer, BMS Parent and Acquisition Merger Sub shall file with the SEC a Tender Offer Statement on Schedule TO (the "SCHEDULE TO") with respect to the Offer (such together with all amendments and supplements thereto and including exhibits thereto, the “Schedule TO and such documents included therein pursuant to which TO”) that shall include the summary term sheet required thereby and, as exhibits, the Offer will be madeto Purchase and a form of letter of transmittal (and appropriate ancillary documents) and summary advertisement (collectively, together with any amendments or supplements or amendments thereto, the "OFFER DOCUMENTS")“Offer Documents”) and (ii) cause the appropriate Offer Documents to be disseminated to holders of shares of Company Common Stock. BMSEach of Parent, Acquisition Merger Sub and the Company each agrees promptly to correct any information provided by it for use inclusion in the Schedule TO and the Offer Documents if and to the extent that such information shall have become false or misleading in any material respect. BMS Parent and Acquisition Merger Sub agree to take all steps necessary use reasonable best efforts to cause the Schedule TO as so corrected to be filed with the SEC. BMS SEC and Acquisition Sub shall deliver or cause to be delivered to the Company, or such other Person as the Company shall designate, the Offer Documents (and any amendments thereto) as so corrected, in such quantities as shall be necessary for dissemination to all holders of Shares and Company Options. The Company shall, at its expense, cause the Offer Documents (and any amendments thereto) to be disseminated to holders of Shares and shares of Company OptionsCommon Stock, in each case case, as and to the extent required by applicable U.S. federal securities lawslaws or the rules or regulations of Nasdaq. Without limiting the generality of the foregoing, the Company will furnish to Parent the information relating to the Company required by the Exchange Act to be set forth in the Offer Documents. The Company and its counsel shall be given an a reasonable opportunity to review and comment on the Schedule TO and the Offer Documents prior to their being each time before any such document is filed with the SEC or disseminated SEC, and Parent and Merger Sub shall give reasonable and good faith consideration to any comments made by the holders of Shares Company and Company Optionsits counsel. BMS Parent and Acquisition Merger Sub shall provide the Company and its counsel with (i) any comments or other communications, whether written or oral, that BMSParent, Acquisition Merger Sub or its their counsel may receive from time to time from the SEC or its staff with respect to the Schedule TO or Offer Documents promptly after receipt of such those comments or other communications. communications and (cii) Each certificate for Shares issued a reasonable opportunity to Acquisition Sub representing Shares accepted for purchase and paid for by Acquisition Sub participate in the Offer response of Parent and Merger Sub to those comments and to provide comments on that response (to which reasonable and good faith consideration shall bear a legend be given), including by participating with Parent and Merger Sub or their counsel in substantially any discussions or meetings with the following form: THE SECURITIES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO RESTRICTIONS ON TRANSFER AS SET FORTH IN THE STOCKHOLDER AGREEMENT, DATED SEPTEMBER 19, 2001, AMONG IMCLONE SYSTEMS INCORPORATED, ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB COMPANY AND ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB BIOLOGICS COMPANY, A COPY OF WHICH MAY BE OBTAINED FROM THE CORPORATE SECRETARY OF IMCLONE SYSTEMS INCORPORATEDSEC.

The Offer. (a) As Provided that this Agreement shall not have been terminated in accordance with Section 7.1 hereof and none of the events set forth in Annex I hereto shall have occurred and be existing, Parent shall cause Purchaser to commence and Purchaser shall commence (within the meaning of Rule 14d-2 under the Securities Exchange Act of 1934 (the "Exchange Act") the Offer as promptly as practicable after the date hereofpracticable, but in no event later than ten Business Days after five business days following the date hereof, Acquisition Sub shall commence an offer (the "OFFER") to purchase for cash 14,392,003 Shares (which shall include, for purposes execution of this Agreement, (i) all Shares issuable in respect . Upon the satisfaction of exercisable, in-the-money Company Options which have been "conditionally exercised" by the holder thereof for purposes of participating in the Offer, and (ii) all Shares issued prior to the expiration of the Offer upon the conversion of any convertible securities or upon the exercise of any options or warrants) (such number of Shares, the "MAXIMUM NUMBER") at a price of $70.00 per Share, net to the seller in cash (such price, as may hereafter be increased, the "OFFER PRICE"). The obligation of Acquisition Sub to accept for payment any Shares tendered pursuant to the Offer shall be subject only to the conditions set forth in Annex I hereto. The initial expiration date , subject to any extension of the Offer shall permitted by Section 1.1(d) hereof, Parent and Purchaser will be the twentieth Business Day following the commencement of the Offer (determined under Rule 14d-1(g)(3) promulgated under the 1934 Act)obligated to accept for payment any Shares validly tendered and not withdrawn. Acquisition Sub Parent expressly reserves the right from time to time, subject to Sections 1.1 (b) and 1.1(d) hereof, to waive any such condition, to increase the Per Share Amount, or to make any other changes in the terms and conditions of the conditions Offer. The Per Share Amount shall be net to the seller in cash, subject to reduction only for any applicable Federal back-up withholding or stock transfer taxes payable by the seller. The Company agrees that no Shares held by the Company or any of its Subsidiaries (as hereinafter defined) will be tendered pursuant to the Offer, modify . (b) Without the terms of the Offer, and increase the Offer Price; PROVIDED that, without the prior written consent of the Company, Acquisition Sub Parent shall not (i) increase decrease the Per Share Amount or reduce the Maximum Number, (ii) reduce the price per Share to be paid pursuant to the Offer, (iii) add to the conditions set forth in Annex I or modify any condition set forth in Annex I, (iv) change the form of consideration payable in the Offer, (ii) decrease the number of Shares sought, (iii) amend or waive satisfaction of the Minimum Condition (as defined in Annex I) to permit the purchase of Shares constituting less than a majority of the number of Shares outstanding, (iv) impose additional conditions to the Offer, (v) otherwise amend any one or more of the conditions set forth in Annex I to broaden the scope of such condition or conditions or (vi) amend any other term of the Offer in any manner adverse to the holders of Shares. Acquisition Sub shall extend the Offer for any period required by any rule, regulation, interpretation or position of the SEC or the staff thereof applicable to the Offer or any period required by applicable law. If any of the conditions to the Offer is not satisfied or waived on any scheduled expiration date of the Offer, Acquisition Sub shall extend the Offer from time to time until such conditions are satisfied or waived; PROVIDED that (i) each such extension of the Offer shall be for a period of not more than ten Business Days, and (ii) Acquisition Sub shall not, without the prior written consent of the Company, extend the Offer beyond the Termination Date. Subject to the foregoing and upon Upon the terms and subject to the conditions of the Offer, Acquisition Sub shall Purchaser will accept for payment and pay forpurchase, as promptly soon as practicable after permitted under the expiration terms of the Offer, all Shares validly tendered and not withdrawn (including if no Shares are validly tendered and not withdrawn), but not in excess prior to the expiration of the Maximum NumberOffer. (bc) The Offer shall be made by means of an offer to purchase (the "Offer to Purchase") having only the conditions set forth in Annex I hereto. As soon as practicable on the date of commencement of the OfferOffer is commenced, BMS Parent and Acquisition Sub Purchaser shall file with the SEC Securities and Exchange Commission (the "SEC") a Tender Offer Statement on Schedule TO 14D-1 (together with all amendments and supplements thereto, the "SCHEDULE TOSchedule 14D-1") with respect to the Offer (that will comply in all material respects with the provisions of such Schedule TO 14D-1 and such documents included therein pursuant to which all applicable Federal securities laws, and will include or incorporate by reference the Offer will be madeto Purchase and forms of the related letter of transmittal and summary advertisement (which documents, together with any supplements or amendments thereto, and any other SEC schedule or form which is filed in connection with the Offer and related transactions, are referred to collectively herein as the "OFFER DOCUMENTSOffer Documents"). BMS, Acquisition Sub Parent and the Company each agrees Purchaser agree promptly to correct any information provided by it for use in the Schedule 14D-1 or the Offer Documents if and to the extent that such information any of them shall have become false or misleading in any material respect. BMS respect (and Acquisition Sub the Company, with respect to written information supplied by it specifically for use in the Schedule 14D-1 or the Offer Documents, shall promptly notify Parent of any required corrections of such information and shall cooperate with Parent and Purchaser with respect to correcting such information) and to supplement the information provided by it specifically for use in the Schedule 14D-1 or the Offer Documents to include any information that shall become necessary in order to make the statements therein, in light of the circumstances under which they were made, not misleading, and Parent and Purchaser further agree to take all steps necessary to cause the Schedule TO 14D-1, as so corrected or supplemented, to be filed with the SEC. BMS SEC and Acquisition Sub shall deliver or cause to be delivered to the Company, or such other Person as the Company shall designate, the Offer Documents (and any amendments thereto) Documents, as so correctedcorrected or supplemented, in such quantities as shall be necessary for dissemination to all holders of Shares and Company Options. The Company shall, at its expense, cause the Offer Documents (and any amendments thereto) to be disseminated to holders of Shares and Company OptionsShares, in each case as and to the extent required by applicable federal Federal securities laws. The Company and its counsel shall be given an a reasonable opportunity to review and comment on the any Offer Documents prior to their being before they are filed with the SEC or disseminated to the holders of Shares SEC. Parent and Company Options. BMS and Acquisition Sub Purchaser shall provide the Company and its counsel in writing with any comments Parent, Purchaser or other communications, whether written or oral, that BMS, Acquisition Sub or its their counsel may receive from time to time from the SEC or its staff with respect to the Offer Documents promptly after receipt of such comments or other communicationscomments. (cd) Each certificate The Offer to Purchase shall provide for an initial expiration date of 20 business days (as defined in Rule 14d-1 under the Exchange Act) from the date of commencement. Purchaser agrees that it shall not terminate or withdraw the Offer or extend the expiration date of the Offer unless at the expiration date of the Offer the conditions to the Offer described in Annex I hereto shall not have been satisfied or earlier waived. If at the expiration date of the Offer, the conditions to the Offer described in Annex I hereto shall not have been satisfied or earlier waived, Parent may, from time to time extend the expiration date of the Offer until the date such conditions are satisfied or earlier waived and Parent becomes obligated to accept for payment and pay for Shares issued tendered pursuant to Acquisition Sub representing Shares accepted the Offer; provided, however, that the expiration date of the Offer may not be extended beyond September 30, 1999 without the consent of the Company. Notwithstanding the foregoing, Purchaser may, without the consent of the Company, (i) extend the expiration date of the Offer (as it may be extended) for purchase any period required by applicable rules and paid for by Acquisition Sub regulations of the SEC in connection with an increase in the consideration to be paid pursuant to the Offer or any other material development affecting the Offer and (ii) extend the expiration date of the Offer (as it may be extended) for up to ten business days, if on such expiration date the conditions for the Offer described on Annex I hereto shall bear have been satisfied or earlier waived, but the number of Shares that have been validly tendered and not withdrawn represents less than 90 percent of the then issued and outstanding Shares on a legend in substantially fully diluted basis; provided, however, that the following form: THE SECURITIES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO RESTRICTIONS ON TRANSFER AS SET FORTH IN THE STOCKHOLDER AGREEMENTexpiration date of the Offer may not be extended beyond September 30, DATED SEPTEMBER 191999 without the consent of the Company. Parent and Purchaser agree that if all of the conditions to the Offer set forth on Annex A are not satisfied on any scheduled expiration date, 2001then if all such conditions are reasonably capable of being satisfied prior to September 30, AMONG IMCLONE SYSTEMS INCORPORATED1999, ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB COMPANY AND ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB BIOLOGICS COMPANYPurchaser shall extend the Offer from time to time (each such individual extension not to exceed 10 Business Days after the previously scheduled expiration date) until such conditions are satisfied or waived; provided, A COPY OF WHICH MAY BE OBTAINED FROM THE CORPORATE SECRETARY OF IMCLONE SYSTEMS INCORPORATEDhowever, that Purchaser shall not be required to extend the Offer beyond August 30, 1999 if, as of such date, the Minimum Condition shall not have been satisfied.

The Offer. (a) As Purchaser shall, and Parent shall cause Purchaser to, (i) commence (within the meaning of Rule 14d-2 under the Exchange Act) the Offer as promptly as reasonably practicable after the date hereof, but in no event later than ten Business Days 10 business days after the date hereof, Acquisition Sub shall commence an offer (the "OFFER") to purchase for cash 14,392,003 Shares (which shall include, for purposes execution of this Agreement, (i) all Shares issuable in respect of exercisable, in-the-money Company Options which have been "conditionally exercised" by the holder thereof for purposes of participating in the Offer, Agreement and (ii) all Shares issued prior cause the Offer to remain open until the expiration twentieth business day after such commencement of the Offer upon the conversion of any convertible securities or upon the exercise of any options or warrants) (such number of Shares, the "MAXIMUM NUMBER") at a price of $70.00 per Share, net to the seller in cash (such price, as may hereafter be increased, the "OFFER PRICEInitial Expiration Date"). The obligation of Acquisition Sub Purchaser shall be obligated, and Parent shall cause Purchaser, to accept for payment any and pay for Shares tendered pursuant to the Offer shall be Offer, subject only to the satisfaction of each of the conditions set forth in Annex I heretoA hereto (the "Offer Conditions"). The initial expiration date At the Company's request, Purchaser will, and Parent shall cause Purchaser to, extend the Offer after the Initial Expiration Date for one or more periods not to exceed an aggregate of 15 business days if the Offer Conditions have not been satisfied at the Initial Expiration Date. Subject to the prior satisfaction of the Offer Conditions, Purchaser shall, and Parent shall be cause Purchaser to, consummate the twentieth Business Day following Offer in accordance with its terms and accept for payment all Shares tendered and not withdrawn by 9:00 a.m. Eastern time on the commencement next business day after the expiration of the Offer (determined under Rule 14d-1(g)(3) promulgated under the 1934 Act)Offer. Acquisition Sub Purchaser expressly reserves the right to waive any of Offer Condition, or increase the conditions Per Share Amount payable in the Offer and to the Offer, modify make any other changes in the terms and conditions of the Offer; provided, and increase the Offer Price; PROVIDED however, that, without the consent of the Company, Acquisition Sub Purchaser shall not, and Parent shall not permit Purchaser to, (i) increase decrease the Per Share Amount or reduce the Maximum Number, (ii) reduce the price per Share to be paid pursuant to the Offer, (iii) add to the conditions set forth in Annex I or modify any condition set forth in Annex I, (iv) change the form of consideration payable in the Offer, (ii) reduce the number of Shares subject to the Offer, (iii) impose conditions to the Offer in addition to the Offer Conditions, (iv) reduce or waive the Minimum Condition (as such term is defined in Annex A hereto), or (v) otherwise amend change the Offer in any a manner adverse to the holders of the Shares. Acquisition Sub Notwithstanding the foregoing, Purchaser may, without the consent of the Company, (i) extend the Offer for one or more periods of not more than 5 business days each beyond the Initial Expiration Date, if, at any scheduled expiration of the Offer, any of the Offer Conditions shall not be satisfied or waived or (ii) extend the Offer for any period required by any rule, regulationregulation or interpretation of the Securities and Exchange Commission (the "SEC"), interpretation or position the staff thereof, applicable to the Offer (provided that Purchaser shall keep the Company reasonably informed of Purchaser's or Parent's contact with the SEC or the staff thereof applicable with respect to the Offer). In addition, if, on the Initial Expiration Date, the sole Offer Condition(s) remaining unsatisfied is/are the failure of any waiting period under the ▇▇▇▇-▇▇▇▇▇-▇▇▇▇▇▇ Antitrust Improvements Act of 1976, as amended (the "HSR Act"), to have expired or any period required by applicable law. If any been terminated and/or the suspensive effect under Section 41 of the conditions German Act Against Restraints on Competition (GWB) (the "German Regulation") to the Offer is not satisfied or waived on any scheduled expiration date of the Offerno longer apply, Acquisition Sub then Purchaser shall, and Parent shall cause Purchaser to, extend the Offer from time to time until such conditions are satisfied or waived; PROVIDED that the earlier to occur of (i) each such extension of the Offer shall be for a period of not more than ten Business DaysSeptember 30, 2005 and (ii) Acquisition Sub shall not, without the prior written consent fifth business day after the later to occur of (A) the expiration or termination of the Companyapplicable waiting period under the HSR Act and (B) the date that the suspensive effect of the German Regulation shall no longer apply. The Per Share Amount shall, extend the Offer beyond the Termination Date. Subject subject to applicable withholding of taxes, be net to the foregoing and seller in cash, upon the terms and subject to the conditions of the Offer. Purchaser shall, Acquisition Sub and Parent shall accept cause Purchaser to, pay for payment and pay for, as promptly as practicable after the expiration of the Offer, all Shares validly tendered and not withdrawn promptly following the acceptance of Shares for payment pursuant to the Offer. Notwithstanding the immediately preceding sentence and subject to the applicable rules of the SEC and the terms and conditions of the Offer, Purchaser expressly reserves the right to delay payment for Shares in order to comply in whole or in part with applicable Laws. Any such delay shall be effected in compliance with Rule 14e-1(c) under the Securities Exchange Act of 1934, as amended (including if no the "Exchange Act"). Purchaser may extend the Offer after the acceptance of Shares are thereunder for a further period of time by means of a subsequent offering period under Rule 14d-11 promulgated under the Exchange Act of not more than 20 business days to meet the objective that there be validly tendered tendered, in accordance with the terms of the Offer, prior to the expiration of the Offer (as so extended), and not withdrawn)withdrawn a number of Shares which, but not in excess together with Shares then beneficially owned by Parent and Purchaser and their direct and indirect subsidiaries, represents at least 90% of the Maximum Numberthen outstanding Shares on a Fully Diluted Basis. If the payment equal to the Per Share Amount in cash (the "Merger Consideration") is to be made to a person other than the person in whose name the surrendered certificate formerly evidencing Shares is registered on the stock transfer books of the Company, it shall be a condition of payment that the certificate so surrendered shall be endorsed properly or otherwise be in proper form for transfer and that the person requesting such payment shall have paid all transfer and other Taxes required by reason of the payment of the Merger Consideration to a person other than the registered holder of the certificate surrendered, or shall have established to the satisfaction of Purchaser that such Taxes either have been paid or are not applicable. (b) As soon as practicable on On the date of commencement of the Offer, BMS Purchaser and Acquisition Sub Parent shall file with the SEC a Tender Offer Statement on Schedule TO (together with all exhibits, amendments and supplements thereto, the "SCHEDULE Schedule TO") with respect to the Offer. The Schedule TO shall comply in all material respects with the provisions of the Exchange Act, the rules and regulations promulgated thereunder and all other applicable Laws, and shall contain or shall incorporate by reference an offer to purchase relating to the Offer (such the "Offer to Purchase") and forms of the related letter of transmittal and any related summary advertisement (the Schedule TO TO, the Offer to Purchase and such documents included therein pursuant to which the Offer will be madeother documents, together with any all exhibits, supplements or and amendments thereto, being referred to herein collectively as the "OFFER DOCUMENTSOffer Documents"). BMSEach of Parent, Acquisition Sub Purchaser and the Company each agrees promptly to correct promptly any information provided by it for use in the Offer Documents if and to the extent that such information shall have become false or misleading in any material respect. BMS , and Acquisition Sub Parent and Purchaser further agree to take all steps necessary to cause the Schedule TO TO, as so corrected corrected, to be filed with the SEC. BMS , and Acquisition Sub shall deliver or cause to be delivered to the Companyother Offer Documents, or such other Person as the Company shall designate, the Offer Documents (and any amendments thereto) as so corrected, in such quantities as shall be necessary for dissemination to all holders of Shares and Company Options. The Company shall, at its expense, cause the Offer Documents (and any amendments thereto) to be disseminated to holders of Shares and Company OptionsShares, in each case as and to the extent required by applicable federal securities laws. The Parent and Purchaser shall give the Company and its counsel shall be given an a reasonable opportunity to review and comment on the Offer Documents prior to their such documents being filed with the SEC or disseminated to the holders of Shares Shares. Parent and Company Options. BMS and Acquisition Sub Purchaser shall provide the Company and its counsel with any comments that Parent, Purchaser or other communications, whether written or oral, that BMS, Acquisition Sub or its their counsel may receive from time to time from the SEC or its staff with respect to the Offer Documents promptly after the receipt of such comments or other communications. (c) Each certificate for Shares issued and shall provide the Company and its counsel with a reasonable opportunity to Acquisition Sub representing Shares accepted for purchase and paid for by Acquisition Sub participate in the Offer shall bear a legend in substantially response of the following form: THE SECURITIES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO RESTRICTIONS ON TRANSFER AS SET FORTH IN THE STOCKHOLDER AGREEMENT, DATED SEPTEMBER 19, 2001, AMONG IMCLONE SYSTEMS INCORPORATED, ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB COMPANY AND ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB BIOLOGICS COMPANY, A COPY OF WHICH MAY BE OBTAINED FROM THE CORPORATE SECRETARY OF IMCLONE SYSTEMS INCORPORATEDParent and Purchaser to such comments.

The Offer. (a) As Provided that this Agreement shall not have been terminated in accordance with Section 8.1 hereof and none of the events set forth in Annex I hereto shall have occurred and be existing, Parent shall cause Purchaser to commence and Purchaser shall commence (within the meaning of Rule 14d-2 under the Securities Exchange Act of 1934 (the "Exchange Act") the Offer as promptly as practicable after the date hereofreasonably practicable, but in no event later than ten Business Days after seven (7) business days (as defined in Rule 14d-1 under the date Exchange Act) following the initial public announcement of the execution of this Agreement (treating the business day on which such public announcement occurs as the first business day). The obligation of Parent and Purchaser to accept for payment any of the Shares tendered shall be subject to the satisfaction of those conditions set forth in Annex I. Parent expressly reserves the right from time to time, subject to Sections 1(b) and 1(d) hereof, Acquisition Sub shall commence an offer (to waive any such condition, to increase the "OFFER") Per Share Amount, or to purchase for cash 14,392,003 Shares (which shall include, for purposes of this Agreement, (i) all Shares issuable in respect of exercisable, in-the-money Company Options which have been "conditionally exercised" by the holder thereof for purposes of participating make any other changes in the Offer, terms and (ii) all Shares issued prior to the expiration conditions of the Offer upon the conversion of any convertible securities or upon the exercise of any options or warrants) (such number of Shares, the "MAXIMUM NUMBER") at a price of $70.00 per Share, Offer. The Per Share Amount shall be net to the seller in cash (such pricecash, as may hereafter be increased, subject to reduction only for any applicable Federal back-up withholding or stock transfer taxes payable by the "OFFER PRICE")seller. The obligation Company agrees that none of Acquisition Sub to accept for payment the Shares held by the Company or any Shares of its Subsidiaries (as hereinafter defined) will be tendered pursuant to the Offer shall be subject only to Offer. (b) Without the conditions set forth in Annex I hereto. The initial expiration date of the Offer shall be the twentieth Business Day following the commencement of the Offer (determined under Rule 14d-1(g)(3) promulgated under the 1934 Act). Acquisition Sub expressly reserves the right to waive any of the conditions to the Offer, modify the terms of the Offer, and increase the Offer Price; PROVIDED that, without the prior written consent of the Company, Acquisition Sub Parent shall not (i) increase decrease the Per Share Amount or reduce the Maximum Number, (ii) reduce the price per Share to be paid pursuant to the Offer, (iii) add to the conditions set forth in Annex I or modify any condition set forth in Annex I, (iv) change the form of consideration payable in the Offer (other than to increase the Per Share Amount), (ii) decrease the number of Shares sought, (iii) amend or waive satisfaction of the Minimum Condition (as defined in Annex I), (iv) impose additional conditions to the Offer, (v) amend any one or more of the conditions set forth in Annex I to broaden the scope of such condition or conditions or otherwise in any manner adverse to the holders of the Shares, or (vvi) otherwise amend any other term of the Offer in any manner adverse to the holders of the Shares. Acquisition Sub shall extend the Offer for any period required by any rule, regulation, interpretation or position of the SEC or the staff thereof applicable to the Offer or any period required by applicable law. If any of the conditions to the Offer is not satisfied or waived on any scheduled expiration date of the Offer, Acquisition Sub shall extend the Offer from time to time until such conditions are satisfied or waived; PROVIDED that (i) each such extension of the Offer shall be for a period of not more than ten Business Days, and (ii) Acquisition Sub shall not, without the prior written consent of the Company, extend the Offer beyond the Termination Date. Subject to the foregoing and upon Upon the terms and subject to the conditions of the Offer, Acquisition Sub shall Purchaser will accept for payment and pay forpurchase, as promptly soon as practicable after permitted under the expiration terms of the Offer, all of the Shares validly tendered and not withdrawn (including if no Shares are validly tendered and not withdrawn), but not in excess prior to the expiration of the Maximum NumberOffer. (bc) The Offer shall be made by means of an offer to purchase (the "Offer to Purchase") having only the conditions set forth in Annex I hereto. As soon as practicable on the date of commencement of the OfferOffer is commenced, BMS Parent and Acquisition Sub Purchaser shall file with the SEC Securities and Exchange Commission (the "SEC") a Tender Offer Statement on Schedule TO (together with all amendments and supplements thereto, the "SCHEDULE Schedule TO") with respect to the Offer (such that will comply in all material respects with the provisions of Schedule TO and such documents included therein pursuant to which all applicable Federal securities laws, and will contain (including as an exhibit) or incorporate by reference the Offer will be madeto Purchase and forms of the related letter of transmittal and summary advertisement (which documents, together with any supplements or amendments thereto, and any other SEC schedule or form which is filed in connection with the Offer and related transactions, are referred to collectively herein as the "OFFER DOCUMENTSOffer Documents"). BMS, Acquisition Sub Parent and the Company each agrees Purchaser agree promptly to correct any information provided by it for use in the Schedule TO or the Offer Documents if and to the extent that such information it shall have become false or misleading in any material respect. BMS respect (and Acquisition Sub the Company, with respect to written information supplied by it specifically for use in the Schedule TO or the Offer Documents, shall promptly notify Parent of any required corrections of such information and shall cooperate with Parent and Purchaser with respect to correcting such information) and to supplement the information provided by it specifically for use in the Schedule TO or the Offer Documents to include any information that shall become necessary in order to make the statements therein, in light of the circumstances under which they were made, not misleading, and Parent and Purchaser further agree to take all steps necessary to cause the Schedule TO TO, as so corrected or supplemented, to be filed with the SEC. BMS SEC and Acquisition Sub shall deliver or cause to be delivered to the Company, or such other Person as the Company shall designate, the Offer Documents (and any amendments thereto) Documents, as so correctedcorrected or supplemented, in such quantities as shall be necessary for dissemination to all holders of Shares and Company Options. The Company shall, at its expense, cause the Offer Documents (and any amendments thereto) to be disseminated to holders of Shares and Company Optionsthe Shares, in each case as and to the extent required by applicable federal Federal securities laws. The Company and its counsel shall be given an a reasonable opportunity to review and comment on the Schedule TO or any Offer Documents prior to their being before they are filed with the SEC or disseminated to the holders of Shares SEC. Parent and Company Options. BMS and Acquisition Sub Purchaser shall provide the Company and its counsel in writing with any comments Parent, Purchaser or other communications, whether written or oral, that BMS, Acquisition Sub or its their counsel may receive from time to time from the SEC or its staff with respect to the Schedule TO or the Offer Documents promptly after receipt of such comments or other communicationscomments. (cd) Each certificate The Offer to Purchase shall provide for an initial expiration date of twenty (20) business days from the date of commencement. Purchaser agrees that it shall not terminate or withdraw the Offer or extend the expiration date of the Offer unless at the expiration date of the Offer the conditions to the Offer described in Annex I hereto shall not have been satisfied or earlier waived. If at the expiration date of the Offer, the conditions to the Offer described in Annex I hereto shall not have been satisfied or earlier waived, Parent may, from time to time extend the expiration date of the Offer until the date such conditions are satisfied or earlier waived and Parent becomes obligated to accept for payment and pay for Shares tendered pursuant to the Offer; provided, however, that the expiration date of the Offer may not be extended beyond February 28, 2001 without the consent of the Company. Notwithstanding the foregoing, Purchaser may, without the consent of the Company, (i) extend the expiration date of the Offer (as it may be extended) for any period required by applicable rules and regulations of the SEC in connection with an increase in the consideration to be paid pursuant to the Offer, (ii) extend the expiration date of the Offer (as it may be extended) for up to ten (10) business days, if on such expiration date the conditions for the Offer described on Annex I hereto shall have been satisfied or earlier waived, but the number of Shares that have been validly tendered and not withdrawn represents less than 90 percent of the then issued and outstanding Shares on a fully diluted basis, provided, that if Purchaser elects to Acquisition Sub representing Shares accepted extend the expiration date of the Offer as set forth in this clause (ii), the obligation of Purchaser, and of Parent to cause Purchaser, to accept for payment, purchase and paid pay for by Acquisition Sub in all of the Shares tendered pursuant to the Offer and not withdrawn shall bear be subject only to the Minimum Condition and the conditions set forth in Section (a) of Annex I hereto, and (iii) provide for a legend subsequent offering period with respect to the Offer pursuant to Rule 14d-11; provided, however, that in substantially any case specified above the following form: THE SECURITIES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO RESTRICTIONS ON TRANSFER AS SET FORTH IN THE STOCKHOLDER AGREEMENTexpiration date of the Offer may not be extended beyond February 28, DATED SEPTEMBER 192001 without the consent of the Company. Parent and Purchaser agree that if all of the conditions to the Offer set forth on Annex I are not satisfied on any scheduled expiration date, then if all such conditions are reasonably capable of being satisfied prior to, February 28, 2001, AMONG IMCLONE SYSTEMS INCORPORATEDPurchaser shall extend the Offer from time to time (each such individual extension not to exceed ten (10) business days after the previously scheduled expiration date) until such conditions are satisfied or waived; provided, ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB COMPANY AND ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB BIOLOGICS COMPANYhowever, A COPY OF WHICH MAY BE OBTAINED FROM THE CORPORATE SECRETARY OF IMCLONE SYSTEMS INCORPORATEDthat Purchaser shall not be required to, and shall not without the consent of the Company, extend the Offer beyond February 28, 2001.

The Offer. (a) As Provided this Agreement shall not have been terminated in accordance with Section 7.1, as promptly as practicable and in any event within seven business days after the date hereof, but Parent or Sub shall, and Parent shall cause Sub to, as the first step in no event later than ten Business Days after completing the date hereofMerger, Acquisition Sub shall commence (within the meaning of Rule 14d-2 under the Securities Exchange Act of 1934, as amended (the "Exchange Act")), an offer (the "OFFEROffer") to purchase all of the issued and outstanding Shares, together with the associated rights issued pursuant to the Company's Rights Plan (as defined herein) (the "Company Rights") for cash 14,392,003 Shares the Offer Price, subject to the conditions set forth in Exhibit A hereto; provided, however, that Parent may designate itself or another wholly owned Subsidiary of Parent as the bidder (which shall include, for purposes within the meaning of this Agreement, (iRule 14d-1(g)(2) all Shares issuable in respect of exercisable, in-the-money Company Options which have been "conditionally exercised" by under the holder thereof for purposes of participating Exchange Act) in the Offer, in which case reference herein to Sub shall be deemed to apply to Parent or such Subsidiary, as appropriate. Except where the context otherwise requires, all references herein to Shares or the Company's common stock shall include the associated Company Rights. The Company shall not tender Shares held by it or by any of its Subsidiaries pursuant to the Offer. Parent or Sub shall, and (ii) all Parent shall cause Sub to, on the terms and subject to the prior satisfaction or waiver of the conditions of the Offer set forth in Exhibit A hereto, accept for payment and pay for Shares issued tendered and not validly withdrawn within three business days of the Acceptance Date. The obligations of Parent or Sub to consummate the Offer and to accept for payment and to pay for any Shares validly tendered on or prior to the expiration of the Offer upon the conversion of any convertible securities or upon the exercise of any options or warrants) (such number of Shares, the "MAXIMUM NUMBER") at a price of $70.00 per Share, net to the seller in cash (such price, as may hereafter be increased, the "OFFER PRICE"). The obligation of Acquisition Sub to accept for payment any Shares tendered pursuant to the Offer and not validly withdrawn shall be subject only to the conditions set forth in Annex I Exhibit A hereto. . (b) The Offer shall be made by means of an offer to purchase (the "Offer to Purchase") containing the terms set forth in this Agreement and the conditions set forth in Exhibit A hereto and providing for an initial expiration date (as may be extended as provided in this clause (b), the "Expiration Date") of twenty business days (as defined in Rule 14d-1(g)(3) under the Exchange Act) from the date of commencement (including the date of commencement) of the Offer. Without the prior written consent of the Company, Parent and Sub shall not, and Parent shall cause Sub not to, decrease the Offer Price, change the form of consideration to be paid, decrease the number of Shares sought, impose conditions to the Offer in addition to those set forth in Exhibit A, change or waive the Minimum Condition, or otherwise amend any other material term or condition of the Offer shall be the twentieth Business Day following the commencement of the Offer (determined under Rule 14d-1(g)(3) promulgated under the 1934 Act). Acquisition Sub expressly reserves the right to waive any of the conditions in a manner adverse to the Offer, modify holders of Shares. Notwithstanding the terms of the Offer, and increase the Offer Price; PROVIDED thatforegoing, without the consent of the Company, Acquisition Parent or Sub shall not be entitled (i) increase or reduce the Maximum Numberand, (ii) reduce the price per Share to be paid pursuant to the Offer, (iii) add to the conditions set forth in Annex I or modify if any condition set forth in Annex Iclause (i), clause (ii), or subclauses (a), (iv) change the form of consideration payable in the Offerb), (c), or (vd) otherwise amend the Offer of clause (iii), of Exhibit A shall exist Parent or Sub shall be required in any manner adverse case where it is reasonably possible that such condition could be remedied by the Final Date (as hereinafter defined)) to the holders of Shares. Acquisition Sub shall extend the Offer at any time for any period required by any rulesuch time periods that it reasonably believes are necessary, regulationif at the initial Expiration Date, interpretation or position of the SEC or the staff thereof applicable to the Offer or any period required by applicable law. If extension thereof, any of the conditions condition to the Offer is not satisfied or waived on any scheduled expiration date of the Offer, Acquisition waived. In no event shall Parent or Sub shall be required to extend the Offer from time to time until such conditions are satisfied or waived; PROVIDED that (i) each such extension beyond the Final Date. In addition, if the Minimum Condition has been met but less than 90% of the outstanding Shares on a fully-diluted basis (as defined in Exhibit A) shall have been validly tendered pursuant to the Offer shall be for a period and not validly withdrawn as of not more than ten Business Daysthe scheduled or extended expiration date, and (ii) Acquisition Parent or Sub shall notmay, without the prior written consent of the Company, extend the Offer beyond after the Termination Dateacceptance of Shares thereunder for a further period of time, not to exceed an aggregate of ten business days, by means of a subsequent offering period under Rule 14d-11 promulgated under the Exchange Act. Subject In addition, the Offer Price may be increased and the Offer may be extended to the foregoing extent required by law or the United States Securities and upon Exchange Commission (the terms and subject to "SEC") in connection with such increase in each case without the conditions consent of the Offer, Acquisition Sub shall accept for payment and pay for, as promptly as practicable after the expiration of the Offer, all Shares validly tendered and not withdrawn (including if no Shares are validly tendered and not withdrawn), but not in excess of the Maximum NumberCompany. (bc) As soon as practicable on after the date of commencement of hereof and in any event within seven business days after the Offerdate hereof, BMS and Acquisition Sub Parent shall (i) file with the SEC SEC, a Tender Offer Statement on Schedule TO (the "SCHEDULE Schedule TO") with respect to the Offer (Offer, which will comply in all material respects with the provisions of, and satisfy in all material respects the requirements of, such Schedule TO and all applicable federal securities laws, and will contain or incorporate by reference all or part of the form of the related letter of transmittal (such documents included therein pursuant to which the Offer will be madedocuments, together with any supplements or amendments thereto, collectively the "OFFER DOCUMENTSOffer Documents")) and (ii) cause the Offer Documents to be disseminated to holders of Shares to the extent required by applicable securities laws. BMSOn the date filed with the SEC and on the date first published, Acquisition sent or given to the holders of Shares, the Offer Documents shall not contain any untrue statement of a material fact or omit to state any material fact required to be stated therein or necessary in order to make the statements therein, in light of the circumstances under which they were made, not misleading, except that neither Parent nor Sub is responsible for information supplied by the Company for inclusion in the Offer Documents. The Company shall provide Parent and Sub all information reasonably requested by Parent or Sub for inclusion in the Offer Documents and any exhibits or annexes thereto. Parent and the Company each agrees promptly to correct any information provided by it for use in the Offer Documents if and to the extent that such information it shall be, or shall have become become, false or misleading in any material respect. BMS and Acquisition Sub agree Parent agrees to take all steps necessary to cause the Schedule TO Offer Documents as so corrected to be filed with the SEC. BMS SEC and Acquisition Sub shall deliver or cause to be delivered to the Company, or such other Person as the Company shall designate, the Offer Documents (and any amendments thereto) as so corrected, in such quantities as shall be necessary for dissemination to all holders of Shares and Company Options. The Company shall, at its expense, cause the Offer Documents (and any amendments thereto) to be disseminated to holders of Shares and Company OptionsShares, in each case as and to the extent required by applicable federal securities laws. The Company . (d) No filing of, or amendment or supplement to, or correspondence to the SEC or its staff with respect to, the Schedule TO or the Offer Documents will be made by the Company, Parent or Sub, without providing the other party and its counsel shall be given an a reasonable opportunity to review and comment on the Offer Documents prior to their being filed with the SEC or disseminated to the holders of Shares thereon. In addition, Parent shall, and Company Options. BMS and Acquisition shall cause Sub shall to, provide the Company and its counsel in writing with any comments or other communicationsthat Parent, whether written or oral, that BMS, Acquisition Sub or its their counsel may receive from time to time from the SEC or its staff with respect to the Offer Documents promptly after receipt of such comments and with copies of any written responses and telephonic notification of any verbal responses by Parent, Sub or other communicationstheir counsel. (c) Each certificate for Shares issued to Acquisition Sub representing Shares accepted for purchase and paid for by Acquisition Sub in the Offer shall bear a legend in substantially the following form: THE SECURITIES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO RESTRICTIONS ON TRANSFER AS SET FORTH IN THE STOCKHOLDER AGREEMENT, DATED SEPTEMBER 19, 2001, AMONG IMCLONE SYSTEMS INCORPORATED, ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB COMPANY AND ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB BIOLOGICS COMPANY, A COPY OF WHICH MAY BE OBTAINED FROM THE CORPORATE SECRETARY OF IMCLONE SYSTEMS INCORPORATED.

The Offer. (a) As Provided that this Agreement shall not have been terminated pursuant to Article VI, Offeror shall use its reasonable best efforts to commence (within the meaning of Rule 14d-2 under the Securities Exchange Act of 1934, as amended, and the rules and regulations promulgated thereunder (the “Exchange Act”)) the Offer as promptly as practicable (but in any event within ten (10) Business Days) after the date hereof, but in no event later than ten Business Days after the date hereof, Acquisition Sub shall commence an offer . (the "OFFER"b) to purchase for cash 14,392,003 Shares (which shall include, for purposes of this Agreement, (i) all Shares issuable in respect of exercisable, in-the-money Company Options which have been "conditionally exercised" by the holder thereof for purposes of participating in the Offer, and (ii) all Shares issued prior to the expiration of the Offer upon the conversion of any convertible securities or upon the exercise of any options or warrants) (such number of Shares, the "MAXIMUM NUMBER") at a price of $70.00 per Share, net to the seller in cash (such price, as may hereafter be increased, the "OFFER PRICE"). The obligation of Acquisition Sub Offeror to accept for payment and pay for any Shares shares of Company Common Stock validly tendered and not validly withdrawn pursuant to the Offer shall be subject only to the satisfaction, or waiver by Offeror in accordance with the terms hereof, of the other conditions and requirements set forth in Exhibit A, as such conditions may be modified in accordance with this Agreement ( the “Offer Conditions”). Subject to the prior satisfaction, or waiver by Offeror in accordance with the terms hereof, of the Offer Conditions as of the Expiration Time, Offeror shall consummate the Offer in accordance with its terms and accept for payment and pay for all shares of Company Common Stock validly tendered and not validly withdrawn pursuant to the Offer as promptly as practicable after the Expiration Time, subject to the Offer Cap and Section 1.01(f). The Offer Price payable in respect of each share of Company Common Stock validly tendered and not validly withdrawn pursuant to the Offer shall be paid to the sellers in cash, without interest (subject to any withholding of tax pursuant to Section 1.05), on the terms and subject to the conditions set forth in Annex I hereto. this Agreement as soon as practicable after the Expiration Time (as the same may be extended or required to be extended). (c) The initial expiration date Offer shall be made by means of an offer to purchase (the “Offer to Purchase”) that describes the terms and conditions of the Offer shall be the twentieth Business Day following the commencement of as set forth in this Agreement, including the Offer (determined under Rule 14d-1(g)(3) promulgated under the 1934 Act)Conditions. Acquisition Sub Offeror expressly reserves the right (in its sole discretion) to waive waive, in whole or in part, any of Offer Condition or to increase the conditions Offer Price or to the Offer, modify make any other changes in the terms and conditions of the Offer; provided, and increase the Offer Price; PROVIDED thathowever, without the consent of that unless otherwise provided by this Agreement or as previously approved in writing by the Company, Acquisition Sub Offeror shall not (i) increase or reduce the Maximum Number, (ii) reduce the price per Share to be paid pursuant to the Offer, (iii) add to the conditions set forth in Annex I Offer Price or modify any condition set forth in Annex I, (iv) change the form of consideration payable in the OfferOffer (other than by adding consideration), (ii) change or modify the Offer Cap, (iii) add to the Offer Conditions, (iv) waive, modify or change the Offer Conditions set forth in paragraphs (a), (b), (d) or (f) of Exhibit A, (v) otherwise amend the waive, modify or change any other Offer Condition in any manner adverse to the holders of Shares. Acquisition Sub shall extend the Offer for any period required by any rule, regulation, interpretation or position shareholders of the SEC Company, (vi) except as otherwise provided in this Section 1.01, extend or otherwise change the staff thereof applicable to the Offer or any period required by applicable law. If any of the conditions to the Offer is not satisfied or waived on any scheduled expiration date of the OfferOffer or (vii) otherwise amend, Acquisition Sub shall extend the Offer from time to time until such conditions are satisfied modify or waived; PROVIDED that (i) each such extension supplement any of the Offer shall be for a period of not more than ten Business Days, and (ii) Acquisition Sub shall not, without the prior written consent of the Company, extend the Offer beyond the Termination Date. Subject to the foregoing and upon the other terms and subject to the conditions of the Offer, Acquisition Sub shall accept for payment and pay for, as promptly as practicable after the expiration of the Offer, all Shares validly tendered and not withdrawn (including if no Shares are validly tendered and not withdrawn), but not in excess of the Maximum Number. (b) As soon as practicable on the date of commencement of the Offer, BMS and Acquisition Sub shall file with the SEC a Tender Offer Statement on Schedule TO (the "SCHEDULE TO") with respect to the Offer (such Schedule TO and such documents included therein pursuant to which the Offer will be made, together with any supplements or amendments thereto, the "OFFER DOCUMENTS"). BMS, Acquisition Sub and the Company each agrees promptly to correct any information provided by it for use in the Offer Documents if and to the extent that such information shall have become false or misleading in any material respect. BMS and Acquisition Sub agree to take all steps necessary to cause the Schedule TO as so corrected to be filed with the SEC. BMS and Acquisition Sub shall deliver or cause to be delivered to the Company, or such other Person as the Company shall designate, the Offer Documents (and any amendments thereto) as so corrected, in such quantities as shall be necessary for dissemination to all holders of Shares and Company Options. The Company shall, at its expense, cause the Offer Documents (and any amendments thereto) to be disseminated to holders of Shares and Company Options, in each case as and to the extent required by applicable federal securities laws. The Company and its counsel shall be given an opportunity to review and comment on the Offer Documents prior to their being filed with the SEC or disseminated to the holders of Shares and Company Options. BMS and Acquisition Sub shall provide the Company and its counsel with any comments or other communications, whether written or oral, that BMS, Acquisition Sub or its counsel may receive from time to time from the SEC or its staff with respect to the Offer Documents promptly after receipt of such comments or other communications. (c) Each certificate for Shares issued to Acquisition Sub representing Shares accepted for purchase and paid for by Acquisition Sub in the Offer shall bear a legend in substantially the following form: THE SECURITIES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO RESTRICTIONS ON TRANSFER AS SET FORTH IN THE STOCKHOLDER AGREEMENT, DATED SEPTEMBER 19, 2001, AMONG IMCLONE SYSTEMS INCORPORATED, ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB COMPANY AND ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB BIOLOGICS COMPANY, A COPY OF WHICH MAY BE OBTAINED FROM THE CORPORATE SECRETARY OF IMCLONE SYSTEMS INCORPORATED.

The Offer. (a) As Provided that this Agreement shall not have been terminated in accordance with Section 10.1, as promptly as practicable after the date hereofpracticable, but in no event later than ten Business Days after November 15, 2012 (or such other date as the date hereofParties may mutually agree to in writing), Acquisition Merger Sub shall, and Parent shall cause Merger Sub to, commence an offer (within the "OFFER"meaning of Rule 14d-2 under the Exchange Act) to purchase for cash 14,392,003 Shares (which shall include, for purposes of this Agreement, (i) all Shares issuable in respect of exercisable, in-the-money Company Options which have been "conditionally exercised" by the holder thereof for purposes of participating in the Offer. The obligations of Merger Sub to, and (ii) all Shares issued prior of Parent to the expiration of the Offer upon the conversion of any convertible securities or upon the exercise of any options or warrants) (such number of Sharescause Merger Sub to, the "MAXIMUM NUMBER") at a price of $70.00 per Share, net to the seller in cash (such price, as may hereafter be increased, the "OFFER PRICE"). The obligation of Acquisition Sub to accept for payment payment, and pay for, any Shares shares of Company Common Stock validly tendered and not validly withdrawn pursuant to the Offer shall be are subject only to the satisfaction or waiver of the conditions set forth in Annex I heretoA (the “Offer Conditions”). The initial expiration date of on which Merger Sub commences the Offer shall be is referred to herein as the twentieth Business Day following “Offer Commencement Date”. The Company agrees that no shares of Company Common Stock held by the commencement of the Offer (determined under Rule 14d-1(g)(3) promulgated under the 1934 Act). Acquisition Sub expressly reserves the right to waive Company or any of the conditions to the Offer, modify the terms its Subsidiaries (other than any such shares held on behalf of the Offer, and increase the Offer Price; PROVIDED that, without the consent of the Company, Acquisition Sub shall not (ithird parties) increase or reduce the Maximum Number, (ii) reduce the price per Share to will be paid tendered pursuant to the Offer, (iii) add to the conditions set forth in Annex I or modify any condition set forth in Annex I, (iv) change the form of consideration payable in the Offer, or (v) otherwise amend the Offer in any manner adverse to the holders of Shares. Acquisition Sub shall extend the Offer for any period required by any rule, regulation, interpretation or position of the SEC or the staff thereof applicable to the Offer or any period required by applicable law. If any of the conditions to the Offer is not satisfied or waived on any scheduled expiration date of the Offer, Acquisition Sub shall extend the Offer from time to time until such conditions are satisfied or waived; PROVIDED that (i) each such extension of the Offer shall be for a period of not more than ten Business Days, and (ii) Acquisition Sub shall not, without the prior written consent of the Company, extend the Offer beyond the Termination Date. Subject to the foregoing and upon the terms and subject to the conditions of the Offer, Acquisition Sub shall accept for payment and pay for, as promptly as practicable after the expiration of the Offer, all Shares validly tendered and not withdrawn (including if no Shares are validly tendered and not withdrawn), but not in excess of the Maximum Number. (b) As soon as practicable on On the date of commencement of the OfferOffer Commencement Date, BMS Parent and Acquisition Merger Sub shall (i) file with the SEC a Tender Offer Statement on Schedule TO (the "SCHEDULE TO") with respect to the Offer (such together with all amendments and supplements thereto and including exhibits thereto, the “Schedule TO TO”) that shall include the summary term sheet required thereby and, as exhibits, the offer to purchase, form of letter of transmittal, form of notice of guaranteed delivery, summary advertisement and such other ancillary documents included therein pursuant to which the Offer will be mademade (collectively, together with any amendments or supplements or amendments thereto, the "OFFER DOCUMENTS"“Offer Documents”); and (ii) cause the Offer Documents to be disseminated to holders of Shares as required by applicable Law. BMSThe Company shall promptly (and in no event later than three (3) Business Days following Merger Sub’s or Parent’s request) furnish to Parent and Merger Sub all information concerning the Company and its Subsidiaries or any of their respective Representatives that may be required by the Exchange Act and other applicable securities Laws or as reasonably requested by Parent or Merger Sub to be set forth in the Offer Documents. Subject to Section 8.6, Acquisition the Company hereby consents to the inclusion of the Company Recommendation in the Offer Documents. Each of Parent, Merger Sub and the Company each agrees promptly to correct any information provided by it for use in the Schedule TO and the Offer Documents if and to the extent that such information shall have become (or shall have become known to be) false or misleading in any material respect. BMS Parent and Acquisition Merger Sub agree to shall take all steps reasonably necessary to amend or supplement the Schedule TO to correct such information and to cause the Schedule TO TO, as so corrected corrected, to be filed with the SEC. BMS SEC and Acquisition Sub shall deliver or cause to be delivered to the Company, or such other Person as the Company shall designate, the Offer Documents (and any amendments thereto) Documents, as so corrected, in such quantities as shall be necessary for dissemination to all holders of Shares and Company Options. The Company shall, at its expense, cause the Offer Documents (and any amendments thereto) to be disseminated to holders of Shares and Company OptionsShares, in each case as and to the extent required by applicable federal securities lawsLaw. The Company and its counsel shall be given an a reasonable opportunity to review and comment on the Schedule TO and the Offer Documents prior to their being (or any amendment or supplement thereto), including the proposed final version thereof, before any such document is filed with the SEC or disseminated to the holders of Shares Shares, and Parent and Merger Sub shall give reasonable and good faith consideration to any comments made by the Company Optionsand its counsel. BMS Parent and Acquisition Merger Sub shall provide the Company and its counsel with (i) any comments or other communications, whether written or oral, that BMSParent, Acquisition Merger Sub or its their counsel or other representatives may receive from time to time from the SEC or its staff with respect to the Schedule TO or Offer Documents promptly after receipt of such those comments or other communicationscommunications and (ii) a reasonable opportunity to participate in the response of Parent and Merger Sub to those comments, and to provide comments on that response (to which Parent and Merger Sub shall give reasonable and good faith consideration), including by participating with Parent and Merger Sub or their counsel in any discussions or meetings with the SEC. (c) Each certificate The Offer Conditions are for the sole benefit of Parent and Merger Sub and Parent and Merger Sub expressly reserve the right to waive, in whole or in part, any of the Offer Conditions and to make any change in the terms of or conditions to the Offer; provided that, without the prior written consent of the Company, neither Parent nor Merger Sub shall: (i) waive or change the Minimum Condition or the Termination Condition; (ii) decrease the Offer Price; (iii) change the form of consideration to be paid in the Offer; (iv) decrease the number of Shares issued subject to Acquisition Sub representing Shares accepted for purchase and paid for by Acquisition Sub the Offer; (v) terminate, extend or otherwise change the expiration date of the Offer, except as otherwise provided in this Agreement; (vi) provide any “subsequent offering period” with the meaning of Rule 14d-11 under the Exchange Act; or (vii) impose additional conditions to the Offer or otherwise amend, modify or supplement any of the Offer Conditions or the other terms of the Offer in any manner adverse to the holders of the Shares. (d) Unless extended as provided in this Agreement, the Offer shall bear expire at 11:59 p.m. New York time on the date that is twenty Business Days (calculated as set forth in Rule 14d-1(g)(3) under the Exchange Act) after the Offer Commencement Date (the “Initial Offer Expiration Date”). If as of 11:59 p.m. New York time on the Initial Offer Expiration Date or any subsequent date as of which the Offer is scheduled to expire, (i) any of the Offer Conditions shall not have been satisfied or waived by Merger Sub, then, unless Parent and the Company otherwise agree, and subject to the rights and remedies of the Parties under this Agreement, Merger Sub shall (and Parent shall cause Merger Sub to), extend the Offer for one or more consecutive increments of not more than five Business Days each, the length of each such period to be determined by Parent in its sole discretion (or for such longer period as Parent and the Company may mutually agree) until such Offer Condition(s) are satisfied or waived, or (ii) the Offer is required to be extended by any rule, regulation, interpretation or position of the U.S. Securities and Exchange Commission (“SEC”) or the staff thereof applicable to the Offer, then Merger Sub shall, and Parent shall cause Merger Sub to, extend the Offer for the minimum period required by such rule, regulation or interpretation or position; provided, however, that Merger Sub shall not be required to extend the Offer pursuant to the immediately preceding clauses (i) or (ii) beyond the End Date unless Parent or Merger Sub is not then permitted to terminate this Agreement pursuant to Section 10.1(c), in which case Merger Sub shall be required to extend the Offer beyond the End Date. In addition, if requested by the Company, Merger Sub shall, and Parent shall cause Merger Sub to, extend the Offer beyond any then scheduled Offer Expiration Date (i) for one or more consecutive increments designated by the Company in its sole discretion (which designation shall be made by the Company in writing to Parent not later than the date that is one Business Day prior to the then scheduled Offer Expiration Date); provided, however, that Merger Sub shall not be required to extend the Offer pursuant to this clause (i) beyond 5 p.m. (New York City time) on December 12, 2012 and (ii) if the Company has delivered a legend notice pursuant to clause (w) of the last sentence of Section 8.6(d) prior to the then scheduled Offer Expiration Date, three Business Days after such notice; provided, however, that Merger Sub shall not be required to extend the Offer pursuant to this clause (ii) more than once (the date on which the Offer finally expires taking into account any extensions pursuant to and in substantially accordance with this Section 2.1(d) is referred to herein as the “Offer Expiration Date”). In addition, Merger Sub shall have the right in its sole discretion to extend the Offer beyond any then-scheduled expiration of the Offer for one or more consecutive increments of up to five Business Days each, the length of each such period to be determined by Parent in its sole discretion (or such longer period as Parent and the Company may mutually agree) to the extent (x) Parent and Merger Sub shall have waived the Financing Proceeds Condition, (y) all of the Offer Conditions other than the Financing Proceeds Condition have been satisfied or waived and (z) the Debt Financing (or any alternative financing contemplated by Section 8.11 (such alternative financing, “Alternative Financing”)) has not actually been received by Merger Sub or Parent, and the lenders party to the Debt Financing Commitment (or to the commitments with respect to any Alternative Financing (such commitments, “Alternative Financing Commitments”)) have not definitively and irrevocably confirmed in writing to Parent and Merger Sub that the Debt Financing (or Alternative Financing) in an amount sufficient (together with the Equity Financing and cash available to the Company) to consummate the Offer and the Merger will be available at the Offer Closing on the terms set forth in the Debt Financing Commitment (or Alternative Financing Commitments) and subject only to the satisfaction of the Offer Conditions (and contribution by Parent or Merger Sub of the proceeds of the Equity Financing). If (x) the Financing Proceeds Condition has been satisfied less than five Business Days prior to the then-scheduled expiration of the Offer (including the then-scheduled expiration date of the Offer) and (y) all of the other Offer Conditions have been satisfied or waived at the then scheduled expiration of the Offer, then Merger Sub and Parent shall have a one-time right to extend the Offer pursuant to this sentence and such extension shall be for a period of up to five Business Days. (e) Subject to the terms and conditions set forth in this Agreement and to the satisfaction, or waiver by Merger Sub, of the Offer Conditions, Merger Sub shall, and Parent shall cause Merger Sub to, accept for payment and pay for, as promptly as practicable (which shall, in any event, be no more than three Business Days) after the Offer Expiration Date, all Shares validly tendered and not validly withdrawn pursuant to the Offer that Merger Sub becomes obligated to purchase pursuant to the Offer (such acceptance, the “Offer Closing”, the time on which the Offer Closing occurs, the “Acceptance Time”, and the date on which the Offer Closing occurs, the “Offer Closing Date”). Parent shall provide, or cause to be provided, to Merger Sub on a timely basis the funds necessary to purchase all Shares that Merger Sub becomes obligated to purchase pursuant to the Offer. (f) The Offer may not be terminated prior to the Offer Expiration Date unless this Agreement is validly terminated in accordance with Section 10.1; provided, however, that if at any date on which the Offer is scheduled to expire, (i) the Marketing Period shall have ended and any Offer Condition (other than the Financing Proceeds Condition) shall not have been satisfied or waived and (ii) the Proxy Statement Clearance Date shall have occurred at least three Business Days prior to such scheduled expiration of the Offer, then (x) notwithstanding the provisions of subclause (i) of Section 2.1(d), Merger Sub may irrevocably and unconditionally terminate the Offer (provided that prior to so terminating the Offer, Merger Sub shall, and Parent shall cause Merger Sub to, notify the Company in writing at least one Business Day in advance of such termination and the Company shall have a one-time right (exercisable in the Company’s sole discretion) to cause Merger Sub to extend, rather than terminate, the Offer for one consecutive increment of five Business Days, in which case Merger Sub shall, and Parent shall cause Merger Sub to, extend the Offer for such period) and (y) if the Financing Outside Date has occurred, the Company shall have the right, exercisable by delivering written notice to Parent and Merger Sub, to cause Merger Sub to, and upon receipt of such written notice, Merger Sub shall, and Parent shall cause Merger Sub to, irrevocably and unconditionally terminate the Offer at the then-scheduled expiration date following form: THE SECURITIES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO RESTRICTIONS ON TRANSFER AS SET FORTH IN THE STOCKHOLDER AGREEMENTthe receipt of such notice sent by the Company. The termination of the Offer pursuant to the immediately preceding sentence is referred to in this Agreement as the “Offer Termination” and the date on which the Offer Termination occurs is referred to in this Agreement as the “Offer Termination Date”. If the Offer Termination occurs, DATED SEPTEMBER 19Merger Sub shall promptly (but in no event later than three Business Days after the Offer Termination Date) return, 2001and shall cause any depository acting on behalf of Merger Sub to return, AMONG IMCLONE SYSTEMS INCORPORATEDall tendered shares of Company Common Stock to the registered holders thereof. The Parties hereto acknowledge and agree that the Offer Termination shall not give rise to a right of termination of this Agreement unless to the extent expressly provided for in Section 10.1 and that, ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB COMPANY AND ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB BIOLOGICS COMPANYabsent such any termination of this Agreement, A COPY OF WHICH MAY BE OBTAINED FROM THE CORPORATE SECRETARY OF IMCLONE SYSTEMS INCORPORATEDthe obligations of the Parties hereunder other than those related to the Offer shall continue to remain in effect notwithstanding the Offer Termination, including those obligations with respect to the Merger. The Parties hereto also acknowledge and agree that the occurrence of the Offer Termination shall not limit or affect the right of the Company to terminate this Agreement pursuant to Section 10.1(h).

The Offer. (a) As promptly as practicable Provided this Agreement shall not have been terminated in accordance with Section 7.1, on the tenth business day after the date initial public announcement of the execution hereof, but in no event later than ten Business Days after the date hereofPurchaser shall, Acquisition Sub and Parent shall cause Purchaser to, commence (within the meaning of Rule 14d-2 under the Securities Exchange Act of 1934, as amended (the "Exchange Act") ) an offer (the "OFFEROffer") to purchase for cash 14,392,003 Shares (which shall include, for purposes of this Agreement, (i) all Shares issuable in respect of exercisable, in-the-money Company Options which have been "conditionally exercised" by the holder thereof for purposes of participating in the Offer, and (ii) all Shares issued prior to the expiration of the Offer upon the conversion of any convertible securities or upon the exercise of any options or warrants) (such number of Shares, the "MAXIMUM NUMBER") Shares at a price of $70.00 55.00 per Share, net to the seller in cash (such price, or such higher price per Share as may hereafter be increasedpaid in the Offer, being referred to herein as the "OFFER PRICEOffer Price"). The obligation of Acquisition Sub to accept for payment any Shares tendered pursuant to the Offer shall be , subject only to the conditions set forth in Annex I A hereto; provided, however, that Parent -------- ------- may designate another wholly owned, direct or indirect subsidiary of Parent as the bidder (within the meaning of Rule 14d-1(g) under the Exchange Act) in the Offer, in which case reference herein to Purchaser shall be deemed to apply to such subsidiary, as appropriate. The initial expiration date Company shall not tender Shares held by it or by any of its subsidiaries pursuant to the Offer Offer. The Purchaser shall, and Parent shall be cause the twentieth Business Day following Purchaser to, on the commencement of terms and subject to the Offer (determined under Rule 14d-1(g)(3) promulgated under the 1934 Act). Acquisition Sub expressly reserves the right to waive any prior satisfaction or waiver of the conditions to the Offer, modify accept for payment and pay for Shares tendered as soon as it is legally permitted to do so under applicable law. (b) The Offer shall be made by means of an offer to purchase (the "Offer to Purchase") containing the terms of the Offer, set forth in this Agreement and increase the Offer Price; PROVIDED that, without the consent of the Company, Acquisition Sub shall not (i) increase or reduce the Maximum Number, (ii) reduce the price per Share to be paid pursuant to the Offer, (iii) add to only the conditions set forth in Annex I or modify any condition set forth A hereto and providing for an expiration date (the "Expiration Date") initially of twenty (20) business days (as defined in Annex IRule 14d-1 under the Exchange Act) from the date of commencement. The Purchaser shall not, (iv) change and Parent shall cause the form of consideration payable in the OfferPurchaser not to, or (v) otherwise amend decrease the Offer in any manner adverse to Price or decrease the holders number of Shares. Acquisition Sub shall extend the Offer for any period required by any ruleShares sought, regulation, interpretation or position of the SEC or the staff thereof applicable to the Offer or any period required by applicable law. If any of amend the conditions to the Offer is not satisfied set forth in Annex A or waived on any scheduled expiration date of the Offer, Acquisition Sub shall extend impose conditions to the Offer from time in addition to time until such conditions are satisfied or waived; PROVIDED that (i) each such extension of the Offer shall be for a period of not more than ten Business Days, and (ii) Acquisition Sub shall notthose set forth in Annex A, without the prior written consent of the Company. The Purchaser may, without the consent of the Company, (i) extend the Offer beyond for the Termination Date. Subject shortest time periods which it reasonably believes are necessary, but in no event more than an additional forty (40) days, in one or more periods of not more than ten (10) business days, if Parent and Purchaser are not in material breach of this Agreement and if any condition to the foregoing Offer is not satisfied or waived and upon such condition is reasonably capable of being satisfied and (ii) if, on the terms and subject to Expiration Date, the conditions of the Offer, Acquisition Sub shall accept for payment and pay for, as promptly as practicable after the expiration of the Offer, all Shares validly tendered and not withdrawn pursuant to the Offer equal at least seventy percent (including if no 70%) of the outstanding Shares are validly tendered and not withdrawnbut less than ninety percent (90%) of the outstanding Shares (on a fully diluted basis, as such term is defined in Annex A), but not (A) extend the Offer on one occasion for up to ten (10) business days, or (B) provide for a subsequent offering period of up to ten (10) business days in excess accordance with Rule 14d-11 under the Exchange Act, in each case (x) notwithstanding that all the conditions to the Offer have been satisfied as of the Maximum Numberdate such extension or subsequent offering period, as the case may be, is announced, and (y) in the case of an extension, so long as Purchaser irrevocably waives the satisfaction of any of the conditions to the Offer (other than in the case of paragraph (iii)(a) of Annex A hereto with respect to any statute, rule, regulation, judgment or injunction arising after the date such extension is announced) that may subsequently become unsatisfied during any such extension. In addition, the Offer Price may be increased and the Offer may be extended to the extent required by law in connection with such increase, in each case without the consent of the Company. If, as of the Expiration Date, (i) the condition set forth in paragraph (iii)(b) of Annex A has not been satisfied or waived, and the Company shall have cooperated with Parent in using all reasonable efforts to cause such condition to be satisfied, or (ii) the condition set forth in clause (1) of paragraph (iii)(c) of Annex A has not been satisfied or waived, and the failure of such condition to be satisfied is not the result of the Company's breach of or failure in any material respect to perform or comply with its material obligations, agreements and covenants herein to be performed by it through the Expiration Date, then, at the written request of the Company, Purchaser shall, and Parent shall cause Purchaser to, extend the Offer in increments of five (5) business days each until the earliest to occur of (w) the satisfaction or waiver of such condition, (x) Parent determines that such condition could not reasonably be expected to be satisfied on or prior to September 30, 2001, (y) the termination of this Agreement in accordance with its terms, and (z) September 30, 2001. (bc) As soon as practicable on On the date of commencement of the OfferOffer is commenced, BMS Parent and Acquisition Sub Purchaser shall file with the SEC United States Securities and Exchange Commission (the "SEC") a Tender Offer Statement on Schedule TO (the "SCHEDULE TO") with respect to the Offer (such together with all amendments and supplements thereto and including the exhibits thereto, the "Schedule TO"). The Schedule TO and such documents included therein pursuant to which shall contain or shall incorporate by reference the Offer will be madeto Purchase and a form of letter of transmittal and summary advertisement (the Schedule TO, the Offer to Purchase and related letter of transmittal and related summary advertisement, together with any amendments and supplements or amendments thereto, collectively the "OFFER DOCUMENTSOffer Documents"). BMSThe Offer Documents shall comply in all material respects with the provisions of applicable federal securities laws and, Acquisition Sub on the date filed with the SEC and on the date first published, sent or given to the Company's stockholders, shall not contain any untrue statement of a material fact or omit to state any material fact required to be stated therein or necessary in order to make the statements therein, in light of the circumstances under which they were made, not misleading, except that no representation is made by Parent or the Purchaser with respect to information supplied by the Company for inclusion in the Offer Documents. Each of Parent and Purchaser shall further take all steps necessary to cause the Offer Documents to be filed with the SEC and to be disseminated to holders of Shares, in each case as and to the extent required by applicable federal securities laws. Each of Parent and Purchaser, on the one hand, and the Company each agrees Company, on the other hand, shall promptly to correct any information provided by it for use in the Offer Documents if and to the extent that such information it shall have become false or and misleading in any material respect. BMS respect and Acquisition Sub agree to the Purchaser further shall take all steps necessary to cause the Schedule TO Offer Documents as so corrected to be filed with the SEC. BMS SEC and Acquisition Sub shall deliver or cause to be delivered to the Company, or such other Person as the Company shall designate, the Offer Documents (and any amendments thereto) as so corrected, in such quantities as shall be necessary for dissemination to all holders of Shares and Company Options. The Company shall, at its expense, cause the Offer Documents (and any amendments thereto) to be disseminated to holders of Shares and Company OptionsShares, in each case as and to the extent required by applicable federal securities laws. The Company and its counsel shall be given an a reasonable opportunity to review and comment on upon the Offer Documents Schedule TO (and shall provide any comments thereon as soon as practicable) prior to their being filed the filing thereof with the SEC or disseminated to SEC. In addition, Parent shall, and shall cause the holders of Shares and Company Options. BMS and Acquisition Sub shall Purchaser to, provide the Company and its counsel in writing with any comments that Parent, Purchaser or other communications, whether written or oral, that BMS, Acquisition Sub or its their counsel may receive from time to time from the SEC or its staff with respect to the Offer Documents promptly after receipt of such comments and with a reasonable opportunity to participate in the preparation of any responses thereto by Parent, Purchaser or other communicationstheir counsel, including copies of any written responses and telephonic notification of any verbal responses. (cd) Each certificate for Parent shall provide or cause to be provided to Purchaser all of the funds necessary to purchase any Shares issued that Purchaser becomes obligated to Acquisition Sub representing Shares accepted for purchase and paid for by Acquisition Sub in pursuant to the Offer shall bear a legend in substantially the following form: THE SECURITIES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO RESTRICTIONS ON TRANSFER AS SET FORTH IN THE STOCKHOLDER AGREEMENT, DATED SEPTEMBER 19, 2001, AMONG IMCLONE SYSTEMS INCORPORATED, ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB COMPANY AND ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB BIOLOGICS COMPANY, A COPY OF WHICH MAY BE OBTAINED FROM THE CORPORATE SECRETARY OF IMCLONE SYSTEMS INCORPORATEDOffer.

The Offer. (a) As Provided that this Agreement shall not have been terminated pursuant to Article XI and nothing shall have occurred that, had the Offer been commenced, would give rise to a right to terminate the Offer pursuant to any of the conditions set forth in paragraph (b) of Annex I, as promptly as practicable after the date hereof, but hereof and in no any event later than within ten (10) Business Days after the date hereofhereof (or such later date as the parties may mutually agree in writing), Acquisition Merger Sub shall, and Parent shall cause Merger Sub to, commence an offer (within the "OFFER"meaning of Rule 14d-2 under the ▇▇▇▇ ▇▇▇) the Offer to purchase for cash 14,392,003 Shares (which shall include, for purposes of this Agreement, (i) any and all Shares issuable in respect of exercisable, in-the-money Company Options which have been "conditionally exercised" by the holder thereof for purposes of participating in the Offer, and (ii) all Shares issued prior to the expiration of the outstanding Shares at the Offer upon the conversion of Price, less any convertible securities or upon the exercise of any options or warrants) (such number of Shares, the "MAXIMUM NUMBER") at a price of $70.00 per Share, net to the seller in cash (such price, as may hereafter be increased, the "OFFER PRICE")withholding Taxes. The Merger Sub’s obligation of Acquisition Sub to accept for payment and pay for any Shares tendered pursuant to in the Offer shall be subject only to the condition that there shall be validly tendered in accordance with the terms of the Offer, immediately prior to the expiration date of the Offer and not withdrawn, a number of Shares that, together with the Shares then owned by Parent and/or Merger Sub, represents at least a majority of the total number of Shares outstanding on a fully diluted basis (assuming conversion or exercise of all derivative securities or other rights to acquire Company Common Stock regardless of the conversion or exercise price, the vesting schedule or other terms and conditions thereof) (the “Minimum Condition”) and to the other conditions set forth in Annex I hereto. The initial expiration date of the Offer shall be the twentieth Business Day following the commencement of the Offer (determined under Rule 14d-1(g)(3) promulgated under the 1934 Act). Acquisition I. Merger Sub expressly reserves the right to waive any of the conditions to the Offer, modify Offer and to make any change in the terms of or conditions to the Offer, and increase the Offer Price; PROVIDED provided that, without the prior consent of the Company, Acquisition Sub shall not (i) increase the Minimum Condition may not be waived or reduce the Maximum Number, amended and (ii) reduce no change may be made that changes the price per Share form of consideration to be paid pursuant to the Offer, (iii) add decreases the Offer Price or the number of Shares sought in the Offer, imposes conditions to the Offer in addition to those set forth in Annex I or modifies the conditions set forth in Annex I or modify any condition set forth in Annex I, (iv) change the form of consideration payable in the Offer, or (v) otherwise amend the Offer in any manner materially adverse to the holders of Shares. Acquisition The initial expiration date of the Offer shall be the twentieth (20th) Business Day after commencement of the Offer (determined in accordance with Rule 14d-1(g)(3) under the ▇▇▇▇ ▇▇▇) (such date, or such subsequent date to which the expiration of the Offer is extended pursuant to and in accordance with the terms of this Agreement, the “Expiration Date”). Notwithstanding the foregoing, (x) without the consent of the Company, Merger Sub shall have the right to extend the Offer for any period required by any rule, regulation, interpretation or position of the SEC or the staff thereof applicable to the Offer or any period required by applicable law. If Applicable Law and (y) if any of the conditions condition to the Offer is not satisfied or waived on any scheduled expiration date Expiration Date of the Offer, Acquisition Merger Sub shall shall, subject to the rights of the parties in Article XI, extend the Offer from for one or more periods (each in the reasonable judgment of Merger Sub for the minimum period of time reasonably expected by the Merger Sub to time be required to satisfy such conditions but in any event not in excess of twenty (20) Business Days each) until such conditions are satisfied or waived; PROVIDED that provided, in each case, (iA) each such extension if, at the initial Expiration Date all of the conditions to the Offer, except for the Minimum Condition, are satisfied or have been waived, Merger Sub shall only be required to extend the Offer shall be and its expiration date beyond the initial Expiration Date for a period one or more additional periods not to exceed an aggregate of not more than ten twenty (20) Business Days, and (iiB) Acquisition in no event shall Merger Sub shall not, without the prior written consent of the Company, be required to extend the Offer beyond the Termination End Date. Following expiration of the Offer, Merger Sub may, in its sole discretion, provide a subsequent offering period (“Subsequent Offering Period”) in accordance with Rule 14d-11 of the 1934 Act. Merger Sub shall not terminate or withdraw the Offer prior to its Expiration Date, unless this Agreement is terminated in accordance with Article XI hereof. If this Agreement is terminated pursuant to Article XI, Merger Sub shall, and Parent shall cause Merger Sub to, promptly terminate the Offer and shall not acquire Shares pursuant thereto. If the Offer is terminated by Merger Sub, or this Agreement is terminated pursuant to Article XI prior to the acquisition of Shares in the Offer, Merger Sub shall promptly return, and shall cause any depositary acting on behalf of Merger Sub to return, in accordance with Applicable Law, all tendered Shares that have not then been purchased in the Offer to the registered holders thereof. Subject to the foregoing foregoing, including the requirements of Rule 14d-11, and upon the terms and subject to the conditions of the Offer, Acquisition Merger Sub shall, and Parent shall cause it to, accept for payment and pay for, as promptly as practicable after the expiration of the Offer, all Shares (i) validly tendered and not withdrawn pursuant to the Offer and (including if no ii) validly tendered in the Subsequent Offering Period (the time at which Shares are validly tendered and not withdrawnfirst accepted for payment under the Offer, the “Acceptance Time”), but not in excess of the Maximum Number. (b) As soon as practicable on On the date of commencement of the Offer, BMS Parent and Acquisition Merger Sub shall file with the SEC a Tender Offer Statement on Schedule TO (the "SCHEDULE TO") with respect to the Offer (such together with all amendments and supplements thereto and including exhibits thereto, the “Schedule TO and such documents included therein pursuant to which TO”) that shall include the summary term sheet required thereby and, as exhibits, the Offer will be madeto Purchase and a form of letter of transmittal and summary advertisement and other appropriate ancillary Offer documents (collectively, together with any amendments or supplements or amendments thereto, the "OFFER DOCUMENTS"“Offer Documents”). BMSThe Company shall promptly upon request of Parent and Merger Sub provide Parent with all information concerning the Company that may be required by applicable securities laws or reasonably requested by Parent or Merger Sub for inclusion in the Schedule TO or the Offer Documents. Each of Parent, Acquisition Merger Sub and the Company each agrees promptly to correct any information provided by it for use in the Schedule TO or the Offer Documents if and to the extent that such information shall have become (or shall become known to be) false or misleading in any material respect. BMS Parent and Acquisition Merger Sub agree to take all steps necessary shall use their reasonable best efforts to cause the Schedule TO as so corrected to be filed with the SEC. BMS SEC and Acquisition Sub shall deliver or cause to be delivered to the Company, or such other Person as the Company shall designate, the Offer Documents (and any amendments thereto) as so corrected, in such quantities as shall be necessary for dissemination to all holders of Shares and Company Options. The Company shall, at its expense, cause the Offer Documents (and any amendments thereto) corrected to be disseminated to holders of Shares and Company OptionsShares, in each case case, as and to the extent required by applicable U.S. federal securities laws. The Company and its counsel shall be given an a reasonable opportunity to review and comment on the Schedule TO and the Offer Documents prior to their being each time before any such document is filed with the SEC or disseminated SEC, and Parent and Merger Sub shall give reasonable and good faith consideration to any comments made by the holders of Shares Company and Company Optionsits counsel. BMS Parent and Acquisition Merger Sub shall provide the Company and its counsel with (i) any comments or other communications, whether written or oral, that BMSParent, Acquisition Merger Sub or its their counsel may receive from time to time from the SEC or its staff with respect to the Schedule TO or Offer Documents promptly after receipt of such those comments or other communicationscommunications and (ii) a reasonable opportunity to participate in the response of Parent and Merger Sub to those comments and to provide comments on that response (to which reasonable and good faith consideration shall be given). (c) Each certificate for Shares issued to Acquisition Sub representing Shares accepted for purchase and paid for by Acquisition Sub Nothing in the Offer this Section 2.01 shall bear a legend affect any termination rights in substantially the following form: THE SECURITIES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO RESTRICTIONS ON TRANSFER AS SET FORTH IN THE STOCKHOLDER AGREEMENT, DATED SEPTEMBER 19, 2001, AMONG IMCLONE SYSTEMS INCORPORATED, ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB COMPANY AND ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB BIOLOGICS COMPANY, A COPY OF WHICH MAY BE OBTAINED FROM THE CORPORATE SECRETARY OF IMCLONE SYSTEMS INCORPORATEDArticle XI.

The Offer. (a) As Subject to the provisions of this Agreement, as promptly as practicable after the date hereof, but in no event later than ten Business Days five business days after the date hereof, Acquisition Sub shall commence an offer (of the "OFFER") to purchase for cash 14,392,003 Shares (which shall include, for purposes public announcement by Parent and the Company of this Agreement, (i) all Shares issuable in respect of exercisableSub shall, in-the-money Company Options which have been "conditionally exercised" by the holder thereof for purposes of participating in and Parent shall cause Sub to, commence the Offer, and (ii) all Shares issued prior to the expiration of the Offer upon the conversion of any convertible securities or upon the exercise of any options or warrants) (such number of Shares, the "MAXIMUM NUMBER") at a price of $70.00 per Share, net to the seller in cash (such price, as may hereafter be increased, the "OFFER PRICE"). The obligation of Acquisition Sub to, and of Parent to cause Sub to, commence the Offer and accept for payment payment, and pay for, any Shares tendered pursuant to the Offer shall be subject only to the conditions set forth in Annex I hereto. The initial expiration date of Exhibit A (the "Offer shall be the twentieth Business Day following the commencement of the Offer Conditions") (determined under Rule 14d-1(g)(3) promulgated under the 1934 Act). Acquisition Sub expressly reserves the right to waive any of the conditions to the Offerwhich may be waived in whole or in part by Sub in its sole discretion, modify the terms of the Offer, and increase the Offer Price; PROVIDED provided that, without the consent of the Company, Acquisition Sub shall not waive the Minimum Condition (as defined in Exhibit A)) and to the terms and conditions of this Agreement. Sub expressly reserves the right to modify the terms of the Offer, except that, without the consent of the Company, Sub shall not (i) increase or reduce the Maximum Numbernumber of Shares subject to the Offer, (ii) reduce the price per Share Offer Price, (iii) amend or add to be paid pursuant to the Offer Conditions, (iv) except as provided in the next sentence, extend the Offer, (iii) add to the conditions set forth in Annex I or modify any condition set forth in Annex I, (ivv) change the form of consideration payable in the Offer, Offer or (vvi) otherwise amend any other term of the Offer in any manner adverse to the holders of the Shares. Acquisition Notwithstanding the foregoing, Sub may, without the consent of the Company, (i) extend the Offer, if at the scheduled or extended expiration date of the Offer any of the Offer Conditions shall not be satisfied or waived, until such time as such conditions are satisfied or waived, (ii) extend the Offer for any period required by any rule, regulation, interpretation or position of the SEC Securities and Exchange Commission (the "SEC") or the staff thereof applicable to the Offer or any period required by applicable law. If any of the conditions to the Offer is not satisfied or waived on any scheduled expiration date of the Offer, Acquisition Sub shall and (iii) extend the Offer from time to time until such conditions are satisfied for any reason on one or waived; PROVIDED that (i) each such extension of the Offer shall be more occasions for a an aggregate period of not more than ten Business Days, and 25 business days beyond the latest expiration date that would otherwise be permitted under clause (i) or (ii) Acquisition Sub shall not, without the prior written consent of the Company, extend the Offer beyond the Termination Datethis sentence. Subject to the foregoing and upon the terms and subject to the conditions of the OfferOffer and this Agreement, Acquisition Sub shall, and Parent shall cause Sub to, accept for payment payment, and pay for, all Shares validly tendered and not withdrawn pursuant to the Offer that Sub becomes obligated to accept for payment, and pay for, pursuant to the Offer as promptly as practicable after the expiration of the Offer, all Shares validly tendered and not withdrawn (including if no Shares are validly tendered and not withdrawn), but not in excess of the Maximum Number. (b) As soon as practicable on On the date of commencement of the Offer, BMS Parent and Acquisition Sub shall file with the SEC a Tender Offer Statement on Schedule TO 14D-1 (the "SCHEDULE TOSchedule 14D-1") with respect to the Offer Offer, which shall contain an offer to purchase and a related letter of transmittal and summary advertisement (such Schedule TO 14D-1 and such the documents included therein pursuant to which the Offer will be made, together with any supplements or amendments thereto, the "OFFER DOCUMENTSOffer Documents"). BMSParent and Sub agree that the Offer Documents shall comply as to form in all material respects with the Securities Exchange Act of 1934, Acquisition as amended (the "Exchange Act"), and the rules and regulations promulgated thereunder and the Offer Documents, on the date first published, sent or given to the Company's shareholders, shall not contain any untrue statement of a material fact or omit to state any material fact required to be stated therein or necessary in order to make the statements therein, in light of the circumstances under which they were made, not misleading, except that no representation or warranty is made by Parent or Sub with respect to information supplied by the Company or any of its shareholders specifically for inclusion or incorporation by reference in the Offer Documents. Each of Parent, Sub and the Company each agrees agree promptly to correct any information provided by it for use in the Offer Documents if and to the extent that such information shall have become false or misleading in any material respect. BMS , and Acquisition Parent and Sub further agree to take all steps necessary to cause the Schedule TO 14D-1 as so corrected to be filed with the SEC. BMS SEC and Acquisition Sub shall deliver or cause to be delivered to the Company, or such other Person as the Company shall designate, the Offer Documents (and any amendments thereto) as so corrected, in such quantities as shall be necessary for dissemination to all holders of Shares and Company Options. The Company shall, at its expense, cause the Offer Documents (and any amendments thereto) corrected to be disseminated to holders of Shares and Company Optionsthe Company's shareholders, in each case as and to the extent required by applicable federal securities laws. The Company and its counsel shall be given an reasonable opportunity to review and comment on upon the Offer Documents prior to their being filed filing with the SEC or disseminated dissemination to the holders shareholders of Shares the Company. Parent and Company Options. BMS and Acquisition Sub shall agree to provide the Company and its counsel with any comments or other communicationsParent, whether written or oral, that BMS, Acquisition Sub or its their counsel may receive from time to time from the SEC or its staff with respect to the Offer Documents promptly after the receipt of such comments or other communicationscomments. (c) Each certificate Parent shall provide or cause to be provided to Sub on a timely basis the funds necessary to accept for payment, and pay for, any Shares issued that Sub becomes obligated to Acquisition Sub representing Shares accepted accept for purchase payment, and paid for by Acquisition Sub in pay for, pursuant to the Offer shall bear a legend in substantially the following form: THE SECURITIES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO RESTRICTIONS ON TRANSFER AS SET FORTH IN THE STOCKHOLDER AGREEMENT, DATED SEPTEMBER 19, 2001, AMONG IMCLONE SYSTEMS INCORPORATED, ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB COMPANY AND ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB BIOLOGICS COMPANY, A COPY OF WHICH MAY BE OBTAINED FROM THE CORPORATE SECRETARY OF IMCLONE SYSTEMS INCORPORATEDOffer.

The Offer. (a) As Provided that this Agreement shall not have been terminated in accordance with Section 9.01 and none of the events set forth in Annex A hereto shall have occurred and be continuing, as promptly as practicable after the date hereofpracticable, but in no event later than ten Business Days eight business days, after the date hereof, Acquisition Parent shall cause Sub shall to, and Sub shall, commence an (within the meaning of Rule 14d-2 under the Securities Exchange Act of 1934, as amended (such Act and the rules and regulations promulgated thereunder being referred to herein as the "Exchange Act")) a tender offer (the "OFFEROffer") to purchase all of the issued and outstanding shares of Class A Common Stock for cash 14,392,003 Shares $5.20 per share (which shall includesuch amount, for purposes of this Agreement, (i) all Shares issuable in respect of exercisable, in-the-money Company Options which have been "conditionally exercised" by the holder thereof for purposes of participating in or any greater amount per share paid pursuant to the Offer, and (ii) all Shares issued prior to the expiration of the Offer upon the conversion of any convertible securities or upon the exercise of any options or warrants) (such number of Shares, the "MAXIMUM NUMBERPer Share Amount") at a price of $70.00 per Share, net to the seller in cash (such price, as may hereafter be increased, the "OFFER PRICE")cash. The obligation of Acquisition Sub to consummate the Offer and to accept for payment and to pay for any Shares shares of Class A Common Stock tendered pursuant to the Offer shall be subject only to the conditions set forth in Annex I A hereto. The initial expiration date of the Offer shall be the twentieth Business Day following the commencement of the Offer (determined under Rule 14d-1(g)(3) promulgated under the 1934 Act). Acquisition Sub expressly reserves the right to waive any of such condition, to increase the conditions Per Share Amount and to the Offer, modify make any other changes in the terms and conditions of the Offer. Notwithstanding the foregoing, and increase the Offer Price; PROVIDED that, without the consent of the Company, Acquisition Sub shall not no change may be made which (i) increase or reduce decreases the Maximum NumberPer Share Amount, (ii) reduce changes the price per Share form of consideration to be paid pursuant to in the Offer, (iii) add reduces the number of shares of Class A Common Stock sought to be purchased in the Offer, (iv) imposes conditions to the conditions Offer in addition to those set forth in Annex I or modify any condition set forth in Annex IA hereto, (iv) change the form of consideration payable in the Offer, or (v) extends the expiration date of the Offer (which shall initially be the minimum period that the Offer must remain open under the applicable rules and regulations of the Securities and Exchange Commission (the "SEC")) or (vi) otherwise amend alters or amends any term of the Offer in any manner adverse to the holders of Shares. Acquisition Sub shall extend shares of Class A Common Stock; provided, however, that (subject to the right of the parties to terminate this Agreement in accordance with Section 9.01) the Offer may be extended (1) for any period to the extent required by law or by any rule, regulation, interpretation or position of the SEC or the staff thereof applicable to the Offer, (2) on one or more occasions (each such extension period not to exceed 10 business days at one time) if at the then scheduled expiration date of the Offer or any period required by applicable law. If any of the conditions to the Offer is Sub's obligations to accept for payment and pay for Class A Common Stock set forth in Annex A hereto shall not satisfied or waived on any scheduled expiration date of the Offer, Acquisition Sub shall extend the Offer from time to time until such conditions are be satisfied or waived; PROVIDED that , (i3) each such extension of the Offer shall be on one or more occasions for a an aggregate period of not more than ten Business Days10 business days if the Minimum Condition (as defined in Annex A hereto) has been satisfied but less than 90% of the then outstanding shares of Class A Common Stock have been validly tendered and not properly withdrawn, and (ii4) Acquisition to provide for a subsequent offering period in accordance with Rule 14d-11 under the Exchange Act. Parent and Sub shall notagree that, without in the event Sub is unable to consummate the Offer on or prior written consent to the expiration date of the CompanyOffer due to the failure of any conditions set forth in Annex A hereto to be satisfied, but subject to the right of the parties to terminate this Agreement in accordance with Section 9.01 and to the right of Parent to exercise the Merger Trigger, Parent shall cause Sub to, and Sub shall, extend the Offer beyond until the Termination Dateearlier of (i) July 31, 2000 or (ii) such time as each such condition has been satisfied or waived. Subject to Assuming the foregoing and upon prior satisfaction or waiver of the terms conditions of the Offer and subject to the conditions of foregoing right to extend the Offer, Acquisition Sub shall accept pay for payment any and pay for, as promptly as practicable after the expiration all shares of the Offer, all Shares Class A Common Stock validly tendered and not withdrawn (including if no Shares are validly tendered and not withdrawn), but not in excess of pursuant to the Maximum Number. (b) As Offer as soon as practicable on the date of commencement of the Offer, BMS and Acquisition Sub shall file with the SEC a Tender Offer Statement on Schedule TO (the "SCHEDULE TO") with respect to the Offer (such Schedule TO and such documents included therein pursuant to which the Offer will be made, together with any supplements or amendments thereto, the "OFFER DOCUMENTS"). BMS, Acquisition Sub and the Company each agrees promptly to correct any information provided by it for use in the Offer Documents if and to the extent that such information shall have become false or misleading in any material respect. BMS and Acquisition Sub agree to take all steps necessary to cause the Schedule TO as so corrected to be filed with the SEC. BMS and Acquisition Sub shall deliver or cause to be delivered to the Company, or such other Person as the Company shall designate, the Offer Documents (and any amendments thereto) as so corrected, in such quantities as shall be necessary for dissemination to all holders of Shares and Company Options. The Company shall, at its expense, cause the Offer Documents (and any amendments thereto) to be disseminated to holders of Shares and Company Options, in each case as and to the extent required by applicable federal securities laws. The Company and its counsel shall be given an opportunity to review and comment on the Offer Documents prior to their being filed with the SEC or disseminated to the holders of Shares and Company Options. BMS and Acquisition Sub shall provide the Company and its counsel with any comments or other communications, whether written or oral, that BMS, Acquisition Sub or its counsel may receive from time to time from the SEC or its staff with respect to the Offer Documents promptly after receipt of such comments or other communicationstermination thereof. (c) Each certificate for Shares issued to Acquisition Sub representing Shares accepted for purchase and paid for by Acquisition Sub in the Offer shall bear a legend in substantially the following form: THE SECURITIES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO RESTRICTIONS ON TRANSFER AS SET FORTH IN THE STOCKHOLDER AGREEMENT, DATED SEPTEMBER 19, 2001, AMONG IMCLONE SYSTEMS INCORPORATED, ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB COMPANY AND ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB BIOLOGICS COMPANY, A COPY OF WHICH MAY BE OBTAINED FROM THE CORPORATE SECRETARY OF IMCLONE SYSTEMS INCORPORATED.

The Offer. (a) As promptly as practicable after the date hereof, but in no event later than ten Business Days after the date hereof, Acquisition Sub shall commence an offer (the "OFFER") to purchase for cash 14,392,003 Shares (which shall include, for purposes of this Agreement, (i) Provided that Parent and Purchaser shall not have delivered (and been entitled to deliver) a notice of the Company’s breach with respect to the Company’s obligations under Section 6.3 (unless all Shares issuable in respect of exercisable, in-the-money Company Options which such breaches set forth therein shall have been "conditionally exercised" by the holder thereof for purposes of participating in the Offercured) Purchaser shall, and Parent shall cause Purchaser to commence (iiwithin the meaning of Rule 14d-2 under the Securities Exchange Act of 1934, as amended (the “Exchange Act”)), not later than July 2, 2008 (provided that the Company shall be prepared to disseminate to its stockholders its Schedule 14d-9 and Schedule 14f-1 within such time period) all Shares issued prior to the expiration of the Offer upon to purchase all outstanding Shares at the conversion of any convertible securities or upon the exercise of any options or warrants) (such number of Shares, the "MAXIMUM NUMBER") at a price of $70.00 per Share, net to the seller in cash (such price, as may hereafter be increased, the "OFFER PRICE")Offer Price. The obligation obligations of Acquisition Sub Purchaser (and of Parent to cause Purchaser) to accept for payment and to pay for any Shares validly tendered (and not withdrawn) pursuant to the Offer shall be subject only to the satisfaction or waiver of those conditions set forth in Annex I heretoExhibit A (the “Offer Conditions”). The initial expiration date of the Offer shall be July 30, 2008 (the twentieth Business Day following “Expiration Date”, unless Purchaser shall have extended the commencement period of time for which the Offer (determined under Rule 14d-1(g)(3) promulgated under is open pursuant to, and in accordance with, Section 1.1(a)(iii), in which event the 1934 Actterm “Expiration Date” shall mean the latest time and date as the Offer, as so extended, may expire). Acquisition Sub Purchaser expressly reserves the right (but shall not be obligated) at any time or from time to time in its sole discretion to waive any of the conditions to the Offer, Offer Condition or modify or amend the terms of the Offer, and increase the Offer Price; PROVIDED except that, without the consent of the Company, Acquisition Sub shall not (i) increase or reduce the Maximum Number, (ii) reduce the price per Share to be paid pursuant to the Offer, (iii) add to the conditions set forth in Annex I or modify any condition set forth in Annex I, (iv) change the form of consideration payable in the Offer, or (v) otherwise amend the Offer in any manner adverse to the holders of Shares. Acquisition Sub shall extend the Offer for any period required by any rule, regulation, interpretation or position of the SEC or the staff thereof applicable to the Offer or any period required by applicable law. If any of the conditions to the Offer is not satisfied or waived on any scheduled expiration date of the Offer, Acquisition Sub shall extend the Offer from time to time until such conditions are satisfied or waived; PROVIDED that (i) each such extension of the Offer shall be for a period of not more than ten Business Days, and (ii) Acquisition Sub shall not, without the prior written consent of the Company, extend Purchaser shall not (A) decrease the Offer beyond Price or change the Termination Date. Subject form of the consideration payable in the Offer, (B) decrease the number of Shares sought pursuant to the foregoing and upon Offer, (C) amend or waive the terms and subject Minimum Tender Condition (as defined in Exhibit A), (D) add to the conditions of set forth on Exhibit A, (E) modify the Offer, Acquisition Sub shall accept for payment and pay for, as promptly as practicable after the expiration of the Offer, all Shares validly tendered and not withdrawn (including if no Shares are validly tendered and not withdrawn), but not conditions set forth on Exhibit A in excess of the Maximum Number. (b) As soon as practicable on the date of commencement of the Offer, BMS and Acquisition Sub shall file with the SEC a Tender Offer Statement on Schedule TO (the "SCHEDULE TO") with respect to the Offer (such Schedule TO and such documents included therein pursuant to which the Offer will be made, together with any supplements or amendments thereto, the "OFFER DOCUMENTS"). BMS, Acquisition Sub and the Company each agrees promptly to correct any information provided by it for use in the Offer Documents if and to the extent that such information shall have become false or misleading in any material respect. BMS and Acquisition Sub agree to take all steps necessary to cause the Schedule TO as so corrected to be filed with the SEC. BMS and Acquisition Sub shall deliver or cause to be delivered to the Company, or such other Person as the Company shall designate, the Offer Documents (and any amendments thereto) as so corrected, in such quantities as shall be necessary for dissemination to all holders of Shares and Company Options. The Company shall, at its expense, cause the Offer Documents (and any amendments thereto) to be disseminated to holders of Shares and Company Options, in each case as and to the extent required by applicable federal securities laws. The Company and its counsel shall be given an opportunity to review and comment on the Offer Documents prior to their being filed with the SEC or disseminated manner adverse to the holders of Shares and Company Options. BMS and Acquisition Sub shall provide or in a manner that would delay consummation of the Company and its counsel with any comments or other communicationsOffer, whether written or oral, that BMS, Acquisition Sub or its counsel may receive from (F) reduce the time to time from the SEC or its staff with respect to the Offer Documents promptly after receipt of such comments or other communications. (c) Each certificate for Shares issued to Acquisition Sub representing Shares accepted for purchase and paid for by Acquisition Sub in period during which the Offer shall bear a legend remain open, or (G) extend the Expiration Date except as required or permitted by Section 1.1(a)(iii) . If, prior to the Purchase Time, this Agreement is terminated in substantially accordance with Article VIII, Purchaser shall (notwithstanding clause (F) of the following form: THE SECURITIES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO RESTRICTIONS ON TRANSFER AS SET FORTH IN THE STOCKHOLDER AGREEMENT, DATED SEPTEMBER 19, 2001, AMONG IMCLONE SYSTEMS INCORPORATED, ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB COMPANY AND ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB BIOLOGICS COMPANY, A COPY OF WHICH MAY BE OBTAINED FROM THE CORPORATE SECRETARY OF IMCLONE SYSTEMS INCORPORATEDprevious sentence) promptly terminate the Offer without accepting any Shares for payment and shall return the Shares tendered promptly after such termination.

The Offer. (a) As Provided that this Agreement shall not have been terminated in accordance with Section 7.1 and none of the events set forth in paragraphs (a) through (g) of Annex A hereto shall have occurred or be existing (and shall not have been waived by the Purchaser), the Purchaser shall commence (within the meaning of Rule 14d-2 under the Securities Exchange Act of 1934, as amended (the "Exchange Act")) the Offer as promptly as reasonably practicable after the date hereof, but in no any event later than ten Business Days within five business days after the date hereof, Acquisition Sub shall commence an offer (public announcement of the "OFFER") to purchase for cash 14,392,003 Shares (which shall include, for purposes execution of this Agreement, (i) all Shares issuable in respect of exercisable, in-the-money Company Options which have been "conditionally exercised" by the holder thereof for purposes of participating in the Offer, and (ii) all Shares issued prior to the expiration of the Offer upon the conversion of any convertible securities or upon the exercise of any options or warrants) (such number of Shares, the "MAXIMUM NUMBER") at a price of $70.00 per Share, net to the seller in cash (such price, as may hereafter be increased, the "OFFER PRICE"). The obligation of Acquisition Sub the Purchaser to accept for payment any and pay for Shares tendered pursuant to the Offer shall be subject only to the satisfaction of the condition that there be validly tendered and not withdrawn prior to the expiration of the Offer that number of Shares when taken together with the Shares then beneficially owned by the Parent or any of its Subsidiaries which represents at least two-thirds of the then outstanding Shares (the "Minimum Condition") and to the satisfaction or waiver by the Purchaser of the other conditions set forth in Annex I A hereto. The initial expiration date Company agrees that no Shares held by the Company or any of its Subsidiaries will be tendered to the Offer shall be Purchaser pursuant to the twentieth Business Day following the commencement of the Offer (determined under Rule 14d-1(g)(3) promulgated under the 1934 Act)Offer. Acquisition Sub The Purchaser expressly reserves the right to waive any of such conditions (other than the conditions Minimum Condition), to increase the Offer, modify price per Share payable in the Offer and to make any other changes in the terms of the Offer; provided, and increase the Offer Price; PROVIDED thathowever, that no change may be made without the prior written consent of the Company, Acquisition Sub shall not (i) increase or reduce the Maximum Number, (ii) reduce Company which decreases the price per Share payable in the Offer, reduces the maximum number of Shares to be purchased in the Offer, changes the form of consideration to be paid pursuant in the Offer or amends any of the conditions set forth in Annex A hereto, imposes conditions to the Offer, (iii) add Offer in addition to the conditions set forth in Annex I A hereto, waives the Minimum Condition or modify any condition set forth in Annex I, (iv) change the form of consideration payable makes other changes in the Offer, or (v) otherwise amend terms of the Offer that are in any manner adverse to the holders of SharesShares or, except as provided below, extends the Offer. Acquisition Sub Subject to the terms of the Offer and this Agreement and the satisfaction or earlier waiver of all the conditions of the Offer set forth in Annex A hereto as of any expiration date of the Offer, the Purchaser will accept for payment and pay for all Shares validly tendered and not withdrawn pursuant to the Offer as soon as it is permitted to do so under applicable law. Notwithstanding the foregoing, the Purchaser shall, until the Drop Dead Date, (i) extend the Offer beyond the scheduled expiration date, which shall be 20 business days following the date of commencement of the Offer, if, at the scheduled expiration of the Offer, any of the conditions to the Purchaser's obligation to accept for payment and to pay for the Shares shall not be satisfied or, to the extent permitted by this Agreement, waived; provided, however, the Purchaser shall not be required to extend the Offer if any such condition is incapable of being satisfied and the Parent simultaneously terminates the Agreement in accordance with the provisions of Article VII or (ii) extend the Offer for any period required by any rule, regulation, regulation or interpretation or position of the SEC or the staff thereof applicable to the Offer or any period required by applicable lawOffer. If any of the conditions to the Offer is not satisfied or waived on any scheduled expiration date of the Offer, Acquisition Sub shall extend the Offer from time to time until such conditions are satisfied or waived; PROVIDED that (i) each such Any extension of the Offer shall be for a period of not more than ten Business Days, and pursuant to clause (iii) Acquisition Sub shall not, without the prior written consent of the Company, extend preceding sentence or this Section 1.1 shall not exceed the Offer beyond lesser often business days or such fewer number of days that the Termination Date. Subject Purchaser reasonably believes are necessary to the foregoing and upon the terms and subject to cause the conditions of the Offer set forth in Annex A hereto to be satisfied. The Purchaser shall provide a "subsequent offering period" (as contemplated by Rule 14d-11 under the Exchange Act) of not less than three business days following its acceptance for payment of Shares in the Offer, Acquisition Sub shall . On or prior to the date that the Purchaser becomes obligated to accept for payment and pay for, as promptly as practicable after the expiration of for Shares pursuant to the Offer, all Shares validly tendered and not withdrawn (including if no Shares are validly tendered and not withdrawn), but not in excess of the Maximum Number. (b) As soon as practicable on the date of commencement of the Offer, BMS and Acquisition Sub Parent shall file with the SEC a Tender Offer Statement on Schedule TO (the "SCHEDULE TO") with respect to the Offer (such Schedule TO and such documents included therein pursuant to which the Offer will be made, together with any supplements or amendments thereto, the "OFFER DOCUMENTS"). BMS, Acquisition Sub and the Company each agrees promptly to correct any information provided by it for use in the Offer Documents if and to the extent that such information shall have become false or misleading in any material respect. BMS and Acquisition Sub agree to take all steps necessary to cause the Schedule TO as so corrected to be filed with the SEC. BMS and Acquisition Sub shall deliver provide or cause to be delivered provided to the Company, or such other Person as Purchaser the Company shall designate, funds necessary to pay for all Shares that the Offer Documents (Purchaser becomes so obligated to accept for payment and any amendments thereto) as so corrected, in such quantities as shall be necessary pay for dissemination pursuant to all holders of Shares and Company Options. The Company shall, at its expense, cause the Offer Documents (and any amendments thereto) to be disseminated to holders of Shares and Company Options, in each case as and to the extent required by applicable federal securities laws. The Company and its counsel shall be given an opportunity to review and comment on the Offer Documents prior to their being filed with the SEC or disseminated to the holders of Shares and Company Options. BMS and Acquisition Sub shall provide the Company and its counsel with any comments or other communications, whether written or oral, that BMS, Acquisition Sub or its counsel may receive from time to time from the SEC or its staff with respect to the Offer Documents promptly after receipt of such comments or other communications. (c) Each certificate for Shares issued to Acquisition Sub representing Shares accepted for purchase and paid for by Acquisition Sub in the Offer shall bear a legend in substantially the following form: THE SECURITIES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO RESTRICTIONS ON TRANSFER AS SET FORTH IN THE STOCKHOLDER AGREEMENT, DATED SEPTEMBER 19, 2001, AMONG IMCLONE SYSTEMS INCORPORATED, ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB COMPANY AND ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB BIOLOGICS COMPANY, A COPY OF WHICH MAY BE OBTAINED FROM THE CORPORATE SECRETARY OF IMCLONE SYSTEMS INCORPORATED.the

The Offer. (a) As promptly as practicable after Subject to the date hereof, but in no event later than ten Business Days after the date hereof, Acquisition Sub shall commence an offer (the "OFFER") to purchase for cash 14,392,003 Shares (which shall include, for purposes provisions of this Agreement, as promptly as practicable, and in any event no more than ten Business Days, after the date of this Agreement, Merger Subsidiary shall, and Parent shall cause Merger Subsidiary to, commence, within the meaning of Rule l4d-2 under the Securities Exchange Act of 1934, as amended (i) all Shares issuable in respect of exercisabletogether with the rules and regulations thereunder (the “Exchange Act”)), in-the-money Company Options which have been "conditionally exercised" by the holder thereof for purposes of participating in the Offer, and (ii) all Shares issued prior to the expiration of the Offer upon the conversion of any convertible securities or upon the exercise of any options or warrants) (such number of Shares, the "MAXIMUM NUMBER") at a price of $70.00 per Share, net to the seller in cash (such price, as may hereafter be increased, the "OFFER PRICE"). The obligation of Acquisition Sub Merger Subsidiary to, and of Parent to cause Merger Subsidiary to, accept for payment and pay for any Shares tendered pursuant to the Offer shall be subject only to the satisfaction of the conditions set forth in Annex I heretoA and to the terms and conditions of this Agreement. The initial expiration date of the Offer shall be the twentieth Business Day following the commencement of the Offer (determined under Rule 14d-1(g)(3) promulgated under the 1934 Act). Acquisition Sub Parent and Merger Subsidiary expressly reserves reserve the right to waive any of the conditions to the OfferOffer to the extent legally permissible (other than the Minimum Condition (as defined in Annex A), modify which may not be waived without the prior written consent of the Company), to increase the price per Share payable in the Offer and to make any other changes in the terms and conditions of the Offer, and increase the Offer Price; PROVIDED except that, without the prior written consent of the Company, Acquisition Sub shall not (i) increase or reduce no change may be made to the Maximum Number, (ii) reduce the price per Share Offer that would alter form of consideration to be paid pursuant paid, no decrease in the Offer Price or the number of Shares sought in the Offer may be made, no change which imposes additional conditions to the Offer, (iii) add to Offer or modifies any of the conditions set forth in Annex I or modify any condition set forth in Annex I, (iv) change the form of consideration payable in the Offer, or (v) otherwise amend the Offer A in any manner adverse to the holders of the Shares may be made and neither Parent nor Merger Subsidiary may extend the Offer, except in accordance with Section 1.01(c). (b) On the date of commencement of the Offer, Parent and Merger Subsidiary shall file with the Securities and Exchange Commission (“SEC”) a Tender Offer Statement on Schedule TO (as amended and supplemented from time to time, the “Schedule TO”), which shall comply in all material respects with the provisions of applicable federal securities laws, and shall contain (including as an exhibit) or incorporate by reference the offer to purchase relating to the Offer and forms of the related letter of transmittal and other appropriate documents (which documents, as amended or supplemented from time to time, are referred to herein collectively as the “Offer Documents”). The Parent and the Merger Subsidiary further agree to disseminate the Offer Documents to holders of Shares as and to the extent required by applicable federal securities laws. In conducting the Offer, the Parent and the Merger Subsidiary shall comply in all material respects with the provisions of the Exchange Act and any other applicable laws necessary to be complied with in connection with the Offer. The Company shall promptly furnish to Parent and Merger Subsidiary all information concerning the Company and its Subsidiaries and the Company’s stockholders that may be reasonably required or requested in connection with any action contemplated by this Section 1.01. The Company and its counsel shall be given a reasonable opportunity to review and comment on the Offer Documents prior to their filing with the SEC. Parent and Merger Subsidiary agree to provide the Company, and to consult with the Company and its counsel regarding, any comments that may be received from the SEC or its staff (whether written or oral) with respect to the Offer Documents promptly after receipt thereof and any responses thereto. Each of Parent, Merger Subsidiary and the Company agrees promptly to correct any information provided by it for use in the Offer Documents if and to the extent that it shall have become false or misleading in any material respect, and Parent and Merger Subsidiary further agree to take all steps necessary to cause the Offer Documents as so corrected to be filed with the SEC and be disseminated to holders of Shares. Acquisition Sub , in each case, as and to the extent required by law. (c) Subject to the terms and conditions hereof, the Offer shall remain open until midnight, New York City time, on the date that is 20 Business Days after the date the Offer is commenced; provided, however, that without the consent of the Company, Parent and Merger Subsidiary shall have the right to extend the Offer (i) from time to time if, at any scheduled expiration date of the Offer, any of the conditions to the Offer set forth in Annex A shall not have been satisfied or earlier waived, until such conditions are satisfied or earlier waived; provided that if only the condition set forth in clause (y) of the first sentence of Annex A hereto is not satisfied or earlier waived, Parent and Merger Subsidiary shall extend the Offer at the request of the Company (but in no event shall Parent and Merger Subsidiary be obligated to extend expiration of the Offer pursuant to this clause (i) beyond September 30, 2004); and provided further that Parent and Merger Subsidiary shall, upon the written request of the Company, extend the Offer for one or more periods not to exceed an aggregate of fifteen Business Days if, as of any expiration date, all of the conditions set forth in clause (z) are not satisfied, but such conditions are reasonably capable of being satisfied in such period, (ii) for any period required by any rule, regulation, interpretation or position of the SEC or the staff thereof applicable to the Offer or any period required by applicable law. If any of the conditions to the Offer is not satisfied , (iii) on one or waived on any scheduled expiration date of the Offer, Acquisition Sub shall extend the Offer from time to time until more occasions (all such conditions are satisfied or waived; PROVIDED that (i) each such extension of the Offer shall be for a period of occasions aggregating not more than ten Business Days, and ) beyond the latest expiration that would otherwise be permitted under clause (i) or (ii) Acquisition Sub of this sentence, if, on such expiration date, all of the conditions to Merger Subsidiary’s obligations to accept for payment Shares are satisfied or earlier waived, but the number of Shares validly tendered (and not withdrawn) pursuant to the Offer, together with Shares then owned by Parent, represents less than 90% of the outstanding Shares on a fully diluted basis; provided, however, that Parent’s decision to extend the Offer in the case of this clause (iii) shall not, without constitute a waiver of the prior written consent conditions set forth in clauses (d) and (f) (excluding any willful or intentional breach of any material obligation of the Company) on Annex A and of its right to terminate the Agreement under Sections 7.01(b), (d), (k) or (l) and (iv) for one or more subsequent offering periods of up to an additional 20 Business Days in the aggregate (collectively, the “Subsequent Period”) pursuant to Rule 14d-11 of the Exchange Act. Notwithstanding the foregoing, Parent and Merger Subsidiary shall also have the right to extend the Offer beyond the Termination Date. in accordance with Section 7.01(f). (d) Subject to the foregoing and upon the terms and subject to the conditions of the OfferOffer and this Agreement, Acquisition Sub Merger Subsidiary shall, and Parent shall cause Merger Subsidiary to, accept for payment and pay for, as promptly as practicable after the expiration of the Offer, all for Shares validly tendered and not withdrawn (including if no Shares are validly tendered and not withdrawn), but not in excess of pursuant to the Maximum Number. (b) As Offer as soon as practicable on after the date of commencement of the Offer, BMS and Acquisition Sub shall file with the SEC a Tender Offer Statement on Schedule TO expiration thereof (the "SCHEDULE TO") with respect to the Offer (such Schedule TO and such documents included therein pursuant to which the Offer will be made, together with any supplements or amendments thereto, the "OFFER DOCUMENTS"). BMS, Acquisition Sub and the Company each agrees promptly to correct any information provided by it for use in the Offer Documents if and to the extent that such information shall have become false or misleading but in any material respectevent within three Business Days); provided that Merger Subsidiary shall immediately accept and promptly pay for all Shares as they are tendered during any Subsequent Period. BMS and Acquisition Sub agree to take all steps necessary to cause the Schedule TO as so corrected to be filed with the SEC. BMS and Acquisition Sub Parent shall deliver provide or cause to be delivered provided to Merger Subsidiary on a timely basis the funds necessary to purchase any Shares that Merger Subsidiary becomes obligated to purchase pursuant to the Company, or such other Person as the Company shall designate, the Offer Documents (and any amendments thereto) as so corrected, in such quantities as shall be necessary for dissemination to all holders of Shares and Company Options. The Company shall, at its expense, cause the Offer Documents (and any amendments thereto) to be disseminated to holders of Shares and Company Options, in each case as and to the extent required by applicable federal securities laws. The Company and its counsel shall be given an opportunity to review and comment on the Offer Documents prior to their being filed with the SEC or disseminated to the holders of Shares and Company Options. BMS and Acquisition Sub shall provide the Company and its counsel with any comments or other communications, whether written or oral, that BMS, Acquisition Sub or its counsel may receive from time to time from the SEC or its staff with respect to the Offer Documents promptly after receipt of such comments or other communicationsOffer. (c) Each certificate for Shares issued to Acquisition Sub representing Shares accepted for purchase and paid for by Acquisition Sub in the Offer shall bear a legend in substantially the following form: THE SECURITIES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO RESTRICTIONS ON TRANSFER AS SET FORTH IN THE STOCKHOLDER AGREEMENT, DATED SEPTEMBER 19, 2001, AMONG IMCLONE SYSTEMS INCORPORATED, ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB COMPANY AND ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB BIOLOGICS COMPANY, A COPY OF WHICH MAY BE OBTAINED FROM THE CORPORATE SECRETARY OF IMCLONE SYSTEMS INCORPORATED.

The Offer. (a) As Provided that this Agreement shall not have been terminated in accordance with Article Eight hereof as promptly as practicable after the date hereofreasonably practicable, but and in no any event later than ten within seven (7) Business Days after the date hereofDays, Acquisition Sub shall commence an offer (the "OFFER") to purchase for cash 14,392,003 Shares (which shall include, for purposes following execution of this Agreement, Parent (i) shall cause the Purchaser to commence (within the meaning of Rule 14d-2 under the Securities Exchange Act of 1934, as amended (including the rules and regulations promulgated thereunder, the “Exchange Act”)) an offer to purchase all of the outstanding Common Shares issuable at the Offer Price; (ii) shall, upon commencement of the Offer but after affording the Company a reasonable opportunity to review and comment thereon, file a Tender Offer Statement on Schedule TO and all other necessary documents with the Securities and Exchange Commission (the “SEC”) and make all deliveries, mailings and telephonic notices required by Rule 14d-3 under the Exchange Act, in respect of exercisable, in-the-money Company Options which have been "conditionally exercised" by each case in connection with the holder thereof for purposes of participating in Offer (the “Offer Documents”); and (iii) shall use its reasonable best efforts to consummate the Offer, and (ii) all Shares issued prior subject to the expiration of the Offer upon the conversion of any convertible securities or upon the exercise of any options or warrants) (such number of Shares, the "MAXIMUM NUMBER") at a price of $70.00 per Share, net to the seller in cash (such price, as may hereafter be increased, the "OFFER PRICE")terms and conditions thereof. The obligation of Acquisition Sub the Purchaser to accept for payment or pay for any Common Shares validly tendered and not validly withdrawn pursuant to the Offer shall will be subject only to the satisfaction or waiver of the conditions set forth in Annex I hereto. The initial expiration date . (b) Parent on behalf of the Offer shall be the twentieth Business Day following the commencement of the Offer (determined under Rule 14d-1(g)(3) promulgated under the 1934 Act). Acquisition Sub Purchaser expressly reserves the right from time to time, subject to Section 1.1(c), to waive any of the conditions Tender Offer Conditions (other than the Minimum Condition (as defined in Annex I hereto)) or to increase the Offer, modify Offer Price or to make any other changes in the terms and conditions of the Offer, and increase the Offer Price; PROVIDED provided that, without the prior written consent of the Company, Acquisition Sub the Purchaser shall not (i) increase or reduce decrease the Maximum NumberOffer Price, (ii) reduce the price per Share to be paid pursuant to the Offer, (iii) add to the conditions set forth in Annex I or modify any condition set forth in Annex I, (iv) change the form of consideration payable in the Offer, decrease the number of Common Shares sought to be purchased in the Offer, impose additional conditions to the Offer or (v) otherwise amend any other term of the Offer in any manner adverse to the holders of Common Shares. Acquisition Sub The Offer shall extend remain open until the date that is twenty (20) Business Days (as such term is defined in Rule 14d-1(g)(3) under the Exchange Act) after (and including the day of) the commencement of the Offer (the “Expiration Date”), unless the Purchaser shall have extended the period of time for any period required by any rulewhich the Offer is open pursuant to, regulationand in accordance with, interpretation or position the terms of the SEC succeeding two sentences or the staff thereof applicable to the Offer or any period as may be required by applicable lawLaw, in which event the term “Expiration Date” shall mean the latest time and date as the Offer, as so extended, may expire; provided, however, that the Purchaser may provide a subsequent offering period after the Expiration Date, in accordance with Rule 14d-11 under the Exchange Act. If at any Expiration Date, any of the conditions to set forth in Annex I hereto (the “Tender Offer Conditions”) is not satisfied or waived on any scheduled expiration by the Purchaser, (i) the Purchaser shall extend the Offer from time to time for periods of not more than five (5) Business Days each until the date that is twenty (20) Business Days after the initial Expiration Date (for the avoidance of doubt, the initial Expiration Date is the twentieth Business Day after the commencement of the Offer) (as long as the Company Board continues to recommend the Offer), Acquisition Sub and (ii) the Purchaser may extend the Offer from time to time for periods of not more than ten (10) Business Days each until the earlier of (x) the date on which all of the Tender Offer Conditions are satisfied or waived or (y) the date on which this Agreement is terminated in accordance with Article Eight hereof; provided, however, that, on the Expiration Date, if the waiting period under the HSR Act or under any material applicable foreign statutes or regulations applicable to the Merger shall have not expired or been terminated, the Purchaser shall extend the Offer from time to time until such conditions are satisfied expiration or waived; PROVIDED that termination under the HSR Act or such other material applicable foreign statutes or regulations. Notwithstanding the foregoing, the Purchaser and Parent may, without receiving the consent of the Company, extend the Expiration Date for any period required by the applicable rules and regulations of the SEC, New York Stock Exchange (i“NYSE”) each such extension or any other stock exchange or automated quotation system applicable to the Offer. Subject to the terms of the Offer shall be and this Agreement and the satisfaction of all the Tender Offer Conditions as of the Expiration Date, the Purchaser will accept for a period of payment and pay for all Common Shares validly tendered and not more than ten Business Days, and (ii) Acquisition Sub shall not, without validly withdrawn pursuant to the Offer promptly after the Expiration Date. Without the prior written consent of the Company, extend the Offer beyond the Termination Date. Subject to the foregoing and upon the terms and subject to the conditions of the Offer, Acquisition Sub Purchaser shall not accept for payment and or pay forfor any Common Shares in the Offer if, as promptly as practicable after a result, the expiration Purchaser would acquire less than the number of Common Shares necessary to satisfy the Offer, all Shares validly tendered and not withdrawn (including if no Shares are validly tendered and not withdrawn), but not in excess of the Maximum NumberMinimum Condition. (bc) As soon as practicable Parent and the Purchaser represent that the Offer Documents will comply in all material respects with the provisions of applicable federal securities laws and, on the date of commencement of the Offer, BMS and Acquisition Sub shall file filed with the SEC and on the date first published, sent or given to the Company’s shareholders, shall not contain any untrue statement of a Tender Offer Statement on Schedule TO (material fact or omit to state any material fact required to be stated therein or necessary in order to make the "SCHEDULE TO") statements made therein, in light of the circumstances under which they were made, not misleading, except that no representation is made by Parent or the Purchaser with respect to information supplied by the Company or the dealer-manager in writing for inclusion in the Offer (such Schedule TO and such documents included therein pursuant to which Documents. The Company represents that the information supplied by the Company in writing for inclusion in the Offer Documents will comply in all material respects with the provisions of applicable federal securities laws and, on the date filed with the SEC and on the date first published, sent or given to the Company’s shareholders, shall not contain any untrue statement of a material fact or omit to state any material fact required to be stated therein or necessary in order to make the statements made therein, in light of the circumstances under which they were made, together with any supplements or amendments thereto, the "OFFER DOCUMENTS")not misleading. BMS, Acquisition Sub Each of Parent and the Company each Purchaser, on the one hand, and the Company, on the other hand, agrees promptly to correct any information provided by it for use in the Offer Documents if and to the extent that such information it shall have become false or misleading in any material respect. BMS , and Acquisition Sub agree the Purchaser further agrees to take all steps necessary to cause the Schedule TO Offer Documents as so corrected to be filed with the SEC. BMS SEC and Acquisition Sub shall deliver or cause to be delivered to the Company, or such other Person as the Company shall designate, the Offer Documents (and any amendments thereto) as so corrected, in such quantities as shall be necessary for dissemination to all holders of Shares and Company Options. The Company shall, at its expense, cause the Offer Documents (and any amendments thereto) to be disseminated to holders shareholders of Shares and Company Optionsthe Company, in each case case, as and to the extent required by applicable federal securities laws. The Company and its counsel shall be given an opportunity to review and comment on the Offer Documents prior to their being filed with the SEC or disseminated to the holders of Shares and Company Options. BMS and Acquisition Sub shall provide the Company and its counsel with any comments or other communications, whether written or oral, that BMS, Acquisition Sub or its counsel may receive from time to time from the SEC or its staff with respect to the Offer Documents promptly after receipt of such comments or other communications. (c) Each certificate for Shares issued to Acquisition Sub representing Shares accepted for purchase and paid for by Acquisition Sub in the Offer shall bear a legend in substantially the following form: THE SECURITIES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO RESTRICTIONS ON TRANSFER AS SET FORTH IN THE STOCKHOLDER AGREEMENT, DATED SEPTEMBER 19, 2001, AMONG IMCLONE SYSTEMS INCORPORATED, ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB COMPANY AND ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB BIOLOGICS COMPANY, A COPY OF WHICH MAY BE OBTAINED FROM THE CORPORATE SECRETARY OF IMCLONE SYSTEMS INCORPORATED.

The Offer. (a) As Subject to the conditions of this Agreement, as promptly as practicable after the date hereof, but in no event later than ten Business Days five business days after the date hereof, Acquisition Sub shall commence an offer (of the "OFFER") to purchase for cash 14,392,003 Shares (which shall include, for purposes public announcement of this Agreement, (i) all Shares issuable in respect of exercisable, in-the-money Company Options which have been "conditionally exercised" by the holder thereof for purposes of participating in the OfferSub shall, and (ii) all Shares issued prior to Parent shall cause Sub to, commence the expiration Offer within the meaning of the Offer upon applicable rules and regulations of the conversion of any convertible securities or upon the exercise of any options or warrants) Securities and Exchange Commission (such number of Shares, the "MAXIMUM NUMBER") at a price of $70.00 per Share, net to the seller in cash (such price, as may hereafter be increased, the "OFFER PRICESEC"). The obligation obligations of Acquisition Sub to, and of Parent to cause Sub to, commence the Offer and accept for payment payment, and pay for, any Shares shares of Target Common Stock tendered pursuant to the Offer shall be are subject only to the conditions set forth in Annex I hereto. The initial expiration date of the Offer shall be the twentieth Business Day following the commencement of the Offer (determined under Rule 14d-1(g)(3) promulgated under the 1934 Act). Acquisition Exhibit A. Sub expressly reserves the right to waive any of the conditions condition to the Offer, Offer or amend or modify the terms of the Offer, and increase the Offer Price; PROVIDED except that, without the consent of the CompanyTarget, Acquisition Sub shall not (i) increase or reduce the Maximum Numbernumber of shares of Target Common Stock subject to the Offer, (ii) reduce the price per Share share of Target Common Stock to be paid pursuant to the Offer, (iii) waive the Minimum Tender Condition, add to the conditions set forth in Annex I Exhibit A or modify any condition set forth in Annex IExhibit A in any manner adverse to the holders of Target Common Stock, (iv) except as provided in the next sentence, extend the Offer, (v) change the form of consideration payable in the Offer, Offer or (vvi) otherwise amend the Offer in any manner adverse to the holders of SharesTarget Common Stock. Acquisition Notwithstanding the foregoing, Sub shall may, without the consent of Target, (A) extend the Offer, if at the scheduled expiration date of the Offer any of the conditions to Sub's obligation to purchase shares of Target Common Stock are not satisfied, until such time as such conditions are satisfied or waived, (B) extend the Offer for any period required by any rule, regulation, interpretation or position of the SEC or the staff thereof applicable to the Offer and (C) extend the Offer for any reason on one or any more occasions for a period required by applicable lawof not more than five business days beyond the latest expiration date that would otherwise be permitted under clause (A) or (B) of this sentence. If any Parent and Sub agree that if all of the conditions to the Offer is are not satisfied or waived on any scheduled expiration date of the OfferOffer then, Acquisition PROVIDED that all such conditions are reasonably capable of being satisfied, Sub shall extend the Offer from time to time until such conditions are satisfied or waived; , PROVIDED that (i) each such extension of the Offer shall be for a period of not more than ten Business Days, and (ii) Acquisition Sub shall not, without the prior written consent of the Company, not be required to extend the Offer beyond the Termination Outside Date. Subject to the foregoing and upon On the terms and subject to the conditions of the OfferOffer and this Agreement, Acquisition Sub shall, and Parent shall accept cause Sub to, pay for payment all shares of Target Common Stock validly tendered and pay for, not withdrawn pursuant to the Offer that Sub becomes obligated to purchase pursuant to the Offer as promptly soon as practicable after the expiration of the Offer, all Shares validly tendered and not withdrawn (including if no Shares are validly tendered and not withdrawn), but not in excess of the Maximum Number. (b) As soon as practicable on On the date of commencement of the Offer, BMS Parent and Acquisition Sub shall file with the SEC a Tender Offer Statement on Schedule TO (the "SCHEDULE TO") with respect to the Offer Offer, which shall contain an offer to purchase and a related letter of transmittal and summary advertisement (such Schedule TO and such the documents included therein pursuant to which the Offer will be made, together with any supplements or amendments thereto, the "OFFER DOCUMENTSOffer Documents"). BMSParent and Sub agree that the Offer Documents shall comply as to form in all material respects with the Securities Exchange Act of 1934 (the "Exchange Act"), Acquisition and the rules and regulations promulgated thereunder and the Offer Documents, on the date first published, sent or given to Target's stockholders, shall not contain any untrue statement of a material fact or omit to state any material fact required to be stated therein or necessary in order to make the statements therein, in light of the circumstances under which they were made, not misleading, except that no representation or warranty is made by Parent or Sub with respect to information supplied by Target or any of its stockholders specifically for inclusion or incorporation by reference in the Offer Documents. Each of Parent, Sub and the Company each agrees Target shall promptly to correct any information provided by it for use in the Offer Documents if and to the extent that such information shall have become false or misleading in any material respect. BMS , and Acquisition each of Parent and Sub agree to shall take all steps necessary to amend or supplement the Offer Documents and to cause the Schedule TO Offer Documents as so corrected amended or supplemented to be filed with the SEC. BMS SEC and Acquisition Sub shall deliver or cause to be delivered to the Company, or such other Person as the Company shall designate, the Offer Documents (and any amendments thereto) as so corrected, in such quantities as shall be necessary for dissemination to all holders of Shares and Company Options. The Company shall, at its expense, cause the Offer Documents (and any amendments thereto) amended or supplemented to be disseminated to holders of Shares and Company OptionsTarget's stockholders, in each case as and to the extent required by applicable federal Federal securities laws. The Company Target and its counsel shall be given an reasonable opportunity to review and comment on upon the Offer Documents prior to their being filed filing with the SEC or disseminated dissemination to the holders stockholders of Shares Target. Parent and Company Options. BMS and Acquisition Sub shall provide the Company Target and its counsel in writing with any comments or other communicationsParent, whether written or oral, that BMS, Acquisition Sub or its their counsel may receive from time to time from the SEC or its staff with respect to the Offer Documents promptly after the receipt of such comments or other communicationscomments. (c) Each certificate for Shares issued Parent shall provide or cause to Acquisition be provided to Sub representing Shares accepted for on a timely basis the funds necessary to purchase and paid for by Acquisition any shares of Target Common Stock that Sub in becomes obligated to purchase pursuant to the Offer shall bear a legend in substantially the following form: THE SECURITIES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO RESTRICTIONS ON TRANSFER AS SET FORTH IN THE STOCKHOLDER AGREEMENT, DATED SEPTEMBER 19, 2001, AMONG IMCLONE SYSTEMS INCORPORATED, ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB COMPANY AND ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB BIOLOGICS COMPANY, A COPY OF WHICH MAY BE OBTAINED FROM THE CORPORATE SECRETARY OF IMCLONE SYSTEMS INCORPORATEDOffer.

The Offer. (a) As Provided that this Agreement shall not have been terminated in accordance with Section 11.01 and nothing shall have occurred that, had the Offer been commenced, would give rise to a right to terminate the Offer pursuant to any of the conditions set forth in Annex I hereto (the "Offer Conditions") (other than the conditions set forth in clause (i) and subclause (E) of clause (ii)), as promptly as practicable after the date hereof, but in no event later than ten 10 Business Days after following the date hereof, Acquisition Sub shall commence an offer (the "OFFER") to purchase for cash 14,392,003 Shares (which shall include, for purposes of this Agreement, (i) all Shares issuable in respect of exercisable, in-the-money Company Options which have been "conditionally exercised" by the holder thereof for purposes of participating in the OfferMerger Subsidiary shall, and Parent shall cause it to, commence (iiwithin the meaning of Rule 14d-2 under the ▇▇▇▇ ▇▇▇) the Offer , to purchase any and all Shares outstanding shares of Company Common Stock, including the associated preferred stock purchase rights (the "Company Rights") issued prior pursuant to the expiration Amended and Restated Rights Agreement dated as of May 9, 2007 between the Offer upon Company and Computershare Investor Services, LLC, as rights agent (the conversion "Company Rights Agreement"), for so long as such Company Rights are outstanding (each such share of any convertible securities or upon the exercise of any options or warrants) (such number of SharesCompany Common Stock, together with its associated Company Right, a "Share", and collectively, the "MAXIMUM NUMBERShares") at a price of $70.00 per Share, net share equal to the seller Offer Price. The Offer shall be subject to the Offer Conditions. The date on which Merger Subsidiary commences the Offer within the meaning of Rule 14d-2 under the 1934 Act is referred to as the "Offer Commencement Date". (b) Subject to the terms and conditions set forth in cash this Agreement and to the satisfaction or waiver of the Offer Conditions, Merger Subsidiary shall, and Parent shall cause it to, promptly after the expiration of the Offer, accept for payment all Shares validly tendered and not withdrawn pursuant to the Offer (such price, as may hereafter be increasedthe time at which Shares are first accepted for payment under the Offer, the "OFFER PRICEAcceptance Time"). The obligation of Acquisition Sub Merger Subsidiary to accept for payment any Shares tendered pursuant to the Offer shall be subject only to the conditions set forth in Annex I hereto. The initial expiration date satisfaction or waiver of each of the Offer Conditions (and shall not be subject to any other conditions). Promptly after the twentieth Business Day following the commencement of Acceptance Time, Merger Subsidiary shall pay the Offer Price for such Shares. (determined under Rule 14d-1(g)(3c) promulgated under the 1934 Act). Acquisition Sub Parent and Merger Subsidiary expressly reserves reserve the right to waive any of the Offer Conditions and to make any change in the terms of or conditions to the Offer, modify the terms of the Offer, and increase including raising the Offer Price; PROVIDED provided that, without the prior written consent of the Company, Acquisition Sub shall not neither Parent nor Merger Subsidiary shall: (i) increase waive or reduce change the Maximum Number, Minimum Condition (as defined in Annex I); (ii) reduce decrease the price per Share to be paid pursuant to the Offer, Offer Price; (iii) add to the conditions set forth in Annex I or modify any condition set forth in Annex I, (iv) change the form of consideration payable to be paid in the Offer, or ; (iv) decrease the number of shares of Company Common Stock sought to be purchased by Merger Subsidiary in the Offer; (v) extend or otherwise amend change the expiration date of the Offer except as otherwise provided herein; or (vi) otherwise amend, modify or supplement any of the Offer Conditions or terms of the Offer in any a manner adverse that adversely affects, or would reasonably be expected to adversely affect, the holders of Shares. (d) Unless extended as provided in this Agreement, the Offer shall expire on the date that is 20 Business Days (calculated as set forth in Rule 14d-1(g)(3) under the ▇▇▇▇ ▇▇▇) after the Offer Commencement Date. Acquisition Sub Notwithstanding the foregoing, (i) Merger Subsidiary shall, and Parent shall cause it to, extend the Offer for any period required by any rule, regulation, interpretation or position of the SEC or the staff thereof or Nasdaq applicable to the Offer or for any period otherwise required by applicable law. If any of the conditions to the Offer is not satisfied or waived on any scheduled expiration date of the Offer, Acquisition Sub shall extend the Offer from time to time until such conditions are satisfied or waived; PROVIDED that (i) each such extension of the Offer shall be for a period of not more than ten Business Days, Applicable Law and (ii) Acquisition Sub if, on the initial expiration date or any subsequent date as of which the Offer is scheduled to expire, any Offer Condition is not satisfied and has not been waived, then Merger Subsidiary shall, and Parent shall not, without the prior written consent of the Companycause it to, extend the Offer beyond for one or more periods ending no later than the Termination Date. Subject End Date to permit such Offer Condition to be satisfied (provided, however, that, if all of the Offer Conditions other than the Minimum Tender Condition and those that by their nature are to be satisfied at the expiration of the Offer have been satisfied or waived, Merger Subsidiary shall have the right, but not the obligation, to terminate the Offer 60 days after the date on which all of the Offer Conditions other than the Minimum Tender Condition and those that by their nature are to be satisfied at the expiration of the Offer have been satisfied or, to the foregoing and upon the terms and subject to the conditions of the Offerextent permissible, Acquisition Sub shall accept for payment and pay for, as promptly as practicable after the have been waived by Merger Subsidiary). Following expiration of the Offer, all Merger Subsidiary may, in its sole discretion, provide a subsequent offering period ("Subsequent Offering Period") in accordance with Rule 14d-11 of the 1934 Act if, immediately following the Acceptance Time, Parent, Merger Subsidiary and their respective Subsidiaries and Affiliates beneficially own less than 90% of the Shares validly outstanding at that time (which Shares beneficially owned shall include Shares tendered and not withdrawn (including if no Shares are validly tendered in the Offer and not withdrawn). Merger Subsidiary shall, and Parent shall cause it to, immediately accept for payment and promptly pay for all Shares as they are validly tendered during such Subsequent Offering Period and in any event in compliance with Rule 14d-11 and Rule 14e-1(c) promulgated under the 1934 Act. The Offer may be terminated prior to its expiration date (as such expiration date may be extended and re-extended in accordance with this Section 2.01(d)), but not only if this Agreement is validly terminated in excess of the Maximum Numberaccordance with Article 11. (be) As soon as practicable on the date of commencement of the OfferOffer Commencement Date, BMS Parent and Acquisition Sub Merger Subsidiary shall (i) file with the SEC a Tender Offer Statement on Schedule TO (the "SCHEDULE TO") with respect to the Offer (such together with all amendments and supplements thereto and including exhibits thereto, the "Schedule TO") that shall include the summary term sheet required thereby and, as exhibits, the Offer to Purchase, a form of letter of transmittal, a form of summary advertisement and any schedule or form required to be filed pursuant to the instructions to Schedule TO and such documents included therein pursuant to which the Offer will be made(collectively, together with any amendments or supplements or amendments thereto, the "OFFER DOCUMENTSOffer Documents"); (ii) timely file with the Commissioner of Commerce of the State of Minnesota any registration statement relating to the Offer required to be filed pursuant to Chapter 80B of the Minnesota Statutes (the "Minnesota Registration Statement"); and (iii) cause the Offer Documents to be disseminated to holders of Shares to the extent required by Applicable Law (including the ▇▇▇▇ ▇▇▇) and, by means of inclusion in the Offer Documents, shall disseminate to the holders of Shares the information set forth in the Minnesota Registration Statement to the extent required by Chapter 80B of the Minnesota Statutes. BMSThe Offer shall be conducted in compliance with the 1934 Act. (f) Parent and Merger Subsidiary shall cause the Offer Documents to (i) comply with the applicable requirements of the 1934 Act and (ii) not contain any untrue statement of a material fact or omit to state any material fact required to be stated therein or necessary in order to make the statements therein, Acquisition Sub in light of the circumstances under which they were made, not misleading; provided, however, no covenant is made by Parent or Merger Subsidiary with respect to information supplied by the Company for inclusion in the Offer Documents. Parent and Merger Subsidiary shall cause the information supplied by Parent and its Affiliates specifically for inclusion in the Company's Solicitation/Recommendation Statement on Schedule 14D-9 (together with any amendments or supplements thereto, the "Schedule 14D-9") or the information statement containing the information required by Section 14(f) of the 1934 Act and Rule 14(f)-1 promulgated thereunder (together with any amendments or supplements thereto, the "Information Statement"), at the respective times the Schedule 14D-9 or the Information Statement are filed with the SEC not to contain any untrue statement of a material fact or omit to state any material fact required to be stated therein or necessary in order to make the statements therein, in light of the circumstances under which they were made, not misleading. Each of Parent, Merger Subsidiary and the Company each agrees promptly to correct any information provided by it for use in the Schedule TO and the Offer Documents if and to the extent that such information shall have become (or shall have become known to be) false or misleading in any material respect. BMS Parent and Acquisition Sub agree to take all steps necessary to Merger Subsidiary shall cause the Schedule TO as so corrected to be filed with the SEC. BMS SEC and Acquisition Sub shall deliver or cause to be delivered to the Company, or such other Person as the Company shall designate, the Offer Documents (and any amendments thereto) as so corrected, in such quantities as shall be necessary for dissemination to all holders of Shares and Company Options. The Company shall, at its expense, cause the Offer Documents (and any amendments thereto) corrected to be disseminated to holders of Shares and Company OptionsShares, in each case as and to the extent required by applicable federal securities lawsApplicable Law (including the 1934 Act). The Company and its counsel shall be given an a reasonable opportunity to review and comment on the Schedule TO and the Offer Documents prior to their being each time before any such document is filed with the SEC or disseminated SEC, and Parent and Merger Subsidiary shall give reasonable and good faith consideration to any comments made by the holders of Shares Company and Company Optionsits counsel. BMS Parent and Acquisition Sub Merger Subsidiary shall provide the Company and its counsel with (i) any comments or other communications, whether written or oral, that BMSParent, Acquisition Sub Merger Subsidiary or its their counsel may receive from time to time from the SEC or its staff with respect to the Schedule TO or Offer Documents promptly after receipt of such those comments or other communicationscommunications and (ii) a reasonable opportunity to participate in the response of Parent and Merger Subsidiary to those comments and to provide comments on that response (to which reasonable and good faith consideration shall be given), including by participating with Parent and Merger Subsidiary or their counsel in any discussions or meetings with the SEC. Each of Parent and Merger Subsidiary shall respond as promptly as practicable to any comments of the SEC or its staff with respect to the Offer Documents or the Offer. (cg) Each certificate for Parent shall cause to be provided to Merger Subsidiary all of the funds necessary to purchase any Shares issued that Merger Subsidiary becomes obligated to Acquisition Sub representing Shares accepted for purchase and paid for by Acquisition Sub in pursuant to the Offer (including pursuant to any Subsequent Offering Period), and shall bear cause Merger Subsidiary to perform, on a legend timely basis, all of Merger Subsidiary's obligations under this Agreement. (h) Parent and Merger Subsidiary shall promptly file with the Commissioner of Commerce of the State of Minnesota all materials referred to in substantially Section 80B.04 of the following form: THE SECURITIES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO RESTRICTIONS ON TRANSFER AS SET FORTH IN THE STOCKHOLDER AGREEMENT, DATED SEPTEMBER 19, 2001, AMONG IMCLONE SYSTEMS INCORPORATED, ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB COMPANY AND ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB BIOLOGICS COMPANY, A COPY OF WHICH MAY BE OBTAINED FROM THE CORPORATE SECRETARY OF IMCLONE SYSTEMS INCORPORATEDMinnesota Statutes.

The Offer. (a) As promptly as practicable after Provided that this Agreement shall not have been terminated in accordance with Section 8.1 and none of the date hereofevents set forth in Appendix A to this Agreement shall have occurred and be existing, but in no event later than within ten Business Days after the date hereof, Acquisition Sub shall commence an offer (public announcement of the "OFFER") to purchase for cash 14,392,003 Shares (which shall include, for purposes execution and delivery of this Agreement, Purchaser shall commence (iwithin the meaning of Rule 14d-2 under the Exchange Act) a cash tender offer to acquire any and all Shares issuable in respect of exercisable, in-the-money Company Options which have been "conditionally exercised" by (including the holder thereof for purposes of participating in related Stock Purchase Rights) at the Offer, and (ii) all Shares issued prior Offer Price. Subject to the expiration of Minimum Condition and subject to the other conditions set forth in Appendix A to this Agreement, Purchaser shall consummate the Offer upon the conversion of any convertible securities or upon the exercise of any options or warrants) (such number of Shares, the "MAXIMUM NUMBER") at a price of $70.00 per Share, net to the seller in cash (such price, as may hereafter be increased, the "OFFER PRICE"). The obligation of Acquisition Sub to accordance with its terms and accept for payment any and pay for Shares tendered pursuant to the Offer as soon as Purchaser is legally permitted to do so under applicable law. The Offer shall be made by means of the Offer to Purchase and shall be subject only to the Minimum Condition and the other conditions set forth in Annex I heretoAppendix A to this Agreement and shall reflect the other terms set forth in this Agreement. The initial Purchaser shall not amend or waive the Minimum Condition and shall not decrease the number of Shares sought in the Offer, change the form of or decrease the amount of consideration to be paid, impose conditions to the Offer in addition to those set forth in Appendix A, make any other change in the Offer which is materially adverse to the Company's stockholders or extend the Offer (except as provided in this Agreement), without the written consent of the Company. If on the expiration date of the Offer (the "Expiration Date") as initially scheduled, which shall be twenty Business Days after the twentieth Business Day following the commencement of date the Offer (determined under Rule 14d-1(g)(3) promulgated under the 1934 Act). Acquisition Sub expressly reserves the right to waive any of the conditions to the Offeris commenced, modify the terms of the Offer, and increase the Offer Price; PROVIDED that, without the consent of the Company, Acquisition Sub shall not (i) increase or reduce the Maximum Number, (ii) reduce the price per Share to be paid pursuant to the Offer, (iii) add to the conditions set forth in Annex I or modify any condition set forth in Annex I, (iv) change the form of consideration payable in the Offer, or (v) otherwise amend the Offer in any manner adverse to the holders of Shares. Acquisition Sub shall extend the Offer for any period required by any rule, regulation, interpretation or position of the SEC or the staff thereof applicable to the Offer or any period required by applicable law. If any of the all conditions to the Offer is are not then satisfied or waived on any scheduled expiration date of waived, Purchaser may, from time to time, in its sole discretion, extend the OfferExpiration Date. Notwithstanding the foregoing, Acquisition Sub Purchaser shall extend the Offer from time to time until such December 31, 2000 if, and to the extent that, at the Expiration Date as initially scheduled, or any extension thereof, the conditions are to the Offer set forth in Appendix A to this Agreement have not been satisfied or waived; PROVIDED that (i) each such extension . Furthermore, if at December 31, 2000, the termination of the Offer waiting period under the HSR Act shall be the only condition to the Offer which is not then satisfied or waived, Purchaser shall extend the Expiration Date from time to time until February 28, 2001. In addition, Purchaser may increase the amount it offers to pay per Share in the Offer, and the Offer may be extended to the extent required by law in connection with such increase, in each case without the consent of the Company. In addition, Purchaser may extend the Offer after the acceptance of Shares thereunder for a further period of time by means of a subsequent offering period under Rule 14d-11 under the Exchange Act, of not more than ten twenty Business Days, and Days to meet the objective (ii) Acquisition Sub shall not, without the prior written consent of the Company, extend the Offer beyond the Termination Date. Subject which is not a condition to the foregoing and upon Offer) that there be validly tendered, in accordance with the terms and subject to the conditions of the Offer, Acquisition Sub shall accept for payment and pay for, as promptly as practicable after the expiration of the Offer, all Shares validly tendered and not withdrawn prior to the Expiration Date (including if no as so extended) a number of Shares are validly tendered which, together with Shares then owned by Parent and not withdrawn)Purchaser, but not in excess represents at least ninety percent of the Maximum Numberoutstanding Shares. (b) As soon as practicable on On the date of commencement of the OfferOffer is commenced, BMS Parent and Acquisition Sub Purchaser shall file with the SEC a Tender Offer Statement tender offer statement on Schedule TO (the "SCHEDULE TO") with respect to the Offer (such Offer. The Schedule TO and such documents included therein pursuant to which will include, as exhibits, the Offer to Purchase and a form of letter of transmittal and summary advertisement. (c) Parent and Purchaser will take all steps necessary to cause the Offer Documents to be madefiled with the SEC and to be disseminated to holders of the Shares, together with any supplements or amendments theretoin each case as and to the extent required by applicable federal securities laws. Parent and Purchaser, on the "OFFER DOCUMENTS"). BMSone hand, Acquisition Sub and the Company each agrees Company, on the other hand, will promptly to correct any information provided by it for use in the Offer Documents if and to the extent that such information it shall have become false or misleading in any material respect. BMS and Acquisition Sub agree to Purchaser will take all steps necessary to cause the Schedule TO Offer Documents as so corrected to be filed with the SEC. BMS SEC and Acquisition Sub shall deliver or cause to be delivered to the Company, or such other Person as the Company shall designate, the Offer Documents (and any amendments thereto) as so corrected, in such quantities as shall be necessary for dissemination to all holders of Shares and Company Options. The Company shall, at its expense, cause the Offer Documents (and any amendments thereto) to be disseminated to holders of Shares and Company Optionsthe Shares, in each case as and to the extent required by applicable federal securities laws. The Company and its counsel shall be given an the opportunity to review and comment on the Offer Documents prior to their being initial Schedule TO before it is filed with the SEC or disseminated to the holders of Shares SEC. Parent and Company Options. BMS and Acquisition Sub shall Purchaser will provide the Company and its counsel in writing with any comments or other communications, whether written or oral, that BMSParent, Acquisition Sub Purchaser or its their counsel may receive from time to time from the SEC or its staff with respect to the Offer Documents Documents, promptly after the receipt of such comments or other communications. (c) Each certificate for Shares issued to Acquisition Sub representing Shares accepted for purchase and paid for by Acquisition Sub in the Offer shall bear a legend in substantially the following form: THE SECURITIES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO RESTRICTIONS ON TRANSFER AS SET FORTH IN THE STOCKHOLDER AGREEMENT, DATED SEPTEMBER 19, 2001, AMONG IMCLONE SYSTEMS INCORPORATED, ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB COMPANY AND ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB BIOLOGICS COMPANY, A COPY OF WHICH MAY BE OBTAINED FROM THE CORPORATE SECRETARY OF IMCLONE SYSTEMS INCORPORATED.

The Offer. (a) As Provided that this Agreement shall not have been terminated in accordance with Section 8.01 and that none of the events set forth in Exhibit A shall have occurred or be existing, or any such occurrence or existence shall have been waived in writing by Purchaser, Purchaser shall, and Parent shall cause Purchaser to, as promptly as practicable after the date hereof, (but in no event later than ten (10) Business Days after following the date hereof, Acquisition Sub shall commence an offer (public announcement of the "OFFER") to purchase for cash 14,392,003 Shares (which shall include, for purposes execution of this Agreement) commence (within the meaning of Rule 14d-2 under the Exchange Act), an offer to purchase all outstanding Common Shares (i) all including those Common Shares issuable in respect of exercisable, in-the-money Company Existing Stock Options which that have been "conditionally exercised" by the holder thereof for purposes of participating in the Offer), and (ii) all Shares issued prior to the expiration of the Offer upon the conversion of any convertible securities or upon the exercise of any options or warrants) (such number of Shares, the "MAXIMUM NUMBER") at a price of $70.00 per Share, net to the seller in cash (such price, or any higher price as may hereafter be increasedpaid in the Offer, the "OFFER PRICE") of $12.00 per Share, in cash (such tender offer, as it may be amended and supplemented from time to time as permitted under this Agreement, the "OFFER"). The obligation of Acquisition Sub Purchaser to consummate the Offer and to accept for payment and pay for any Shares tendered pursuant to the Offer thereto shall be subject only to the terms and conditions set forth in Annex I heretothis Agreement and to those conditions set forth in Exhibit A (the "OFFER CONDITIONS"), any of which may be waived by Purchaser in its sole discretion and without any consent of the Company. The initial expiration date of the Offer shall be the twentieth US Business Day following the commencement of the Offer (determined under Rule 14d-1(g)(3) promulgated under the 1934 Act)Offer. Acquisition Sub Purchaser expressly reserves the right to waive any of the conditions to the Offer, modify the terms of the Offer, and increase the Offer Price; PROVIDED except that, without the prior written consent of the Company, Acquisition Sub Purchaser shall not (iA) increase decrease the Offer Price or reduce change the Maximum Numberform of the consideration payable in the Offer, (iiB) reduce decrease the price per Share to be paid number of Shares sought pursuant to the Offer, (iiiC) add impose additional conditions to the conditions set forth in Annex I or modify any condition set forth in Annex IOffer, (ivD) change the form of consideration payable conditions to the Offer (other than a reduction in the Offer, Minimum Tender Condition) or (vE) otherwise amend make any other change in the terms or conditions of the Offer in any manner which is adverse to the holders of Common Shares. (b) Subject to the terms and conditions of this Agreement and to the satisfaction or waiver of the Offer Conditions as of any scheduled expiration of the initial offering period of the Offer, Purchaser shall accept for payment Shares validly tendered and not withdrawn pursuant to the Offer and pay for such Shares promptly after such scheduled expiration. Acquisition Sub Notwithstanding the foregoing, Purchaser and Parent shall have the right to (i) extend the Offer, from time to time, if at the expiration date of the Offer (with respect to either the initial offering period or an extended offering period, as the case may be) any of the conditions to the Offer have not been satisfied or waived, (ii) extend the Offer for any period required by any rule, regulation, interpretation or position of the SEC or the staff thereof applicable to the Offer or any period (iii) elect to provide one or more subsequent offering periods pursuant to Rule 14d-11 of the Exchange Act (collectively, the "SUBSEQUENT PERIOD"). In addition, the Offer Price may be increased and the Offer may be extended to the extent required by applicable law. If any of the conditions to the Offer is not satisfied or waived on any scheduled expiration date of the Offer, Acquisition Sub shall extend the Offer from time to time until law in connection with such conditions are satisfied or waived; PROVIDED that (i) increase in each such extension of the Offer shall be for a period of not more than ten Business Days, and (ii) Acquisition Sub shall not, case without the prior written consent of the Company, extend the Offer beyond the Termination Date. Subject to the foregoing and upon the terms and subject to the conditions of the Offer, Acquisition Sub shall accept for payment and pay for, as promptly as practicable after the expiration of the Offer, all Shares validly tendered and not withdrawn (including if no Shares are validly tendered and not withdrawn), but not in excess of the Maximum Number. (bc) As soon as practicable on On the date of commencement of the Offer, BMS and Acquisition Sub Purchaser shall file or cause to be filed with the SEC a Tender Offer Statement on Schedule TO (the "SCHEDULE TO") with respect to the Offer (which will comply in all material respects with the provisions of, and satisfy in all material respects the requirements of, such Schedule TO and such all applicable US federal securities laws and shall contain the offer to purchase and related letter of transmittal and other ancillary Offer documents included therein and instruments pursuant to which the Offer will be made, together made (collectively with any supplements or amendments thereto, the "OFFER DOCUMENTS"). BMSThe Company and its counsel shall be given a reasonable opportunity to review and comment on the Offer Documents prior to their filing with the SEC. Purchaser agrees to provide the Company with, Acquisition Sub and to consult with the Company regarding, any comments that may be received from the SEC or its staff or any other regulatory authority with respect to the Offer Documents promptly after receipt thereof. Parent, Purchaser and the Company each agrees agree promptly to correct any information provided by it for use in the Offer Documents if and to the extent that such information it shall have become false or misleading in any material respect. BMS respect and Acquisition Sub agree Purchaser further agrees to take all steps necessary to cause the Schedule TO Offer Documents as so corrected to be filed with the SEC. BMS SEC and Acquisition Sub shall deliver or cause to be delivered to the Company, or such other Person as the Company shall designate, the Offer Documents (and any amendments thereto) as so corrected, in such quantities as shall be necessary for dissemination to all holders of Shares and Company Options. The Company shall, at its expense, cause the Offer Documents (and any amendments thereto) to be disseminated to holders of Common Shares and Company Existing Stock Options, in each case as and to the extent required by applicable federal securities laws. The Company and its counsel shall be given an opportunity to review and comment on the Offer Documents prior to their being filed with the SEC or disseminated to the holders of Shares and Company Options. BMS and Acquisition Sub shall provide the Company and its counsel with any comments or other communications, whether written or oral, that BMS, Acquisition Sub or its counsel may receive from time to time from the SEC or its staff with respect to the Offer Documents promptly after receipt of such comments or other communicationslaw. (c) Each certificate for Shares issued to Acquisition Sub representing Shares accepted for purchase and paid for by Acquisition Sub in the Offer shall bear a legend in substantially the following form: THE SECURITIES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO RESTRICTIONS ON TRANSFER AS SET FORTH IN THE STOCKHOLDER AGREEMENT, DATED SEPTEMBER 19, 2001, AMONG IMCLONE SYSTEMS INCORPORATED, ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB COMPANY AND ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB BIOLOGICS COMPANY, A COPY OF WHICH MAY BE OBTAINED FROM THE CORPORATE SECRETARY OF IMCLONE SYSTEMS INCORPORATED.

The Offer. (a) As Subject to the terms and conditions of this Agreement, Merger Sub shall, and Parent shall cause Merger Sub to, as promptly as practicable after the date hereof, but and in any event no event later than ten fifteen Business Days after the date hereof, Acquisition Sub shall commence an offer (within the meaning of Rule 14d-2 under the Securities Exchange Act of 1934, as amended (the "OFFER"“Exchange Act”)) to purchase for cash 14,392,003 Shares (which shall include, for purposes of this Agreement, (i) all Shares issuable in respect of exercisable, in-the-money Company Options which have been "conditionally exercised" by the holder thereof for purposes of participating in the Offer, and (ii) all Shares issued prior to the expiration of the Offer upon the conversion of any convertible securities or upon the exercise of any options or warrants) (such number of Shares, the "MAXIMUM NUMBER") at a purchase price of $70.00 26.55 per Share, net to the seller in cash (such price, or any higher price offered and paid by Merger Sub in its sole discretion in the Offer, as any such price may hereafter be increasedadjusted pursuant to Section 1.01(g), the "OFFER PRICE"“Offer Price”). . (b) The initial expiration date of the Offer shall be 11:59 p.m., New York City time, on the date that is twenty Business Days following the date on which the Offer is commenced (the “Initial Expiration Date”) (the Initial Expiration Date or such later time and date to which the Offer has been extended in accordance with the terms and conditions set forth herein, the “Expiration Date”). (c) The obligation of Acquisition Merger Sub to commence the Offer and to accept for payment any and pay for Shares tendered pursuant to the Offer shall be subject only to (i) the non-waivable condition that pursuant to the Offer, prior to the Expiration Date, there shall have been validly tendered and not properly withdrawn a number of Shares which constitutes at least a majority of the outstanding Shares (excluding from such calculation any shares held by the Parent Group, Loews Corporation, a Delaware corporation and the owner of approximately 90% of the outstanding shares of common stock of Parent (“Loews”), and the directors and executive officers of each of the Company, Merger Sub, Parent and Loews, as of the Acceptance Time) (the “Minimum Condition”) and (ii) the other conditions set forth in Annex I heretohereto (together with the Minimum Condition, the “Offer Conditions”). The initial expiration date For purposes of determining whether the Minimum Condition has been satisfied, Parent and Merger Sub shall have the right to include or exclude for purposes of its determination thereof Shares tendered in the Offer pursuant to guaranteed delivery procedures (provided that if the Company notifies Parent that it reasonably believes that Shares that are subject to guaranteed delivery procedures may not be delivered to Merger Sub in accordance with such guaranteed delivery procedures, then Parent and Merger Sub will not include any such Shares in its determination of whether the Minimum Condition has been satisfied without the prior consent of the Offer shall be Company (acting pursuant to the twentieth Business Day following the commencement direction of the Offer Special Committee)). (determined under Rule 14d-1(g)(3d) promulgated under the 1934 Act). Acquisition Merger Sub expressly reserves the right to (i) increase the Offer Price and (ii) waive any of the conditions to the Offer, Offer Conditions or modify the terms of the OfferOffer (other than the Minimum Condition which shall be non-waivable), and increase the Offer Price; PROVIDED except that, without the prior written consent of the CompanyCompany (provided that such consent has been approved by the Special Committee), Acquisition Merger Sub shall not, and Parent shall not permit Merger Sub to, do any of the following: (iA) increase or reduce decrease the Maximum NumberOffer Price, (ii) reduce change the price per Share form of consideration to be paid pursuant in the Offer or decrease the number of Shares subject to the Offer, (iiiB) add impose any conditions to the conditions Offer other than the Offer Conditions set forth in Annex I hereto or modify any condition of the Offer Conditions set forth in Annex I, (iv) change the form of consideration payable in the Offer, or (v) otherwise amend the Offer I hereto in any manner adverse to the holders of Shares, (C) otherwise amend or modify the Offer in a manner that would materially and adversely affect the holders of Shares, or (D) except as otherwise provided in this Section 1.01(d), extend the Offer. Acquisition Notwithstanding the foregoing, unless this Agreement has been terminated in accordance with Section 8.01, Merger Sub may, without the consent of the Company (or the Special Committee), and upon the request of the Company, Merger Sub shall (I) extend the Offer for one or more consecutive increments of not more than ten Business Days each (or such longer period as the parties may agree in writing), if at any otherwise scheduled Expiration Date any of the Offer Conditions shall not have been satisfied or, if permissible, waived; (II) extend the Offer for any minimum period required by any rule, regulation, interpretation or position of the SEC U.S. Securities and Exchange Commission (the “SEC”) or the staff thereof applicable to the Offer Offer; or any period required (III) if Shares have been accepted for payment but the number of shares of Common Stock collectively owned by applicable law. If any the Parent Group is less than 90% of the conditions shares of Common Stock on a fully-diluted basis (without regard to Shares tendered pursuant to guaranteed delivery procedures that have not yet been delivered in settlement or satisfaction of such guarantee), provide a “subsequent offering period” (as such term is defined in Rule 14d-1(g)(8) under the Exchange Act) in accordance with Rule 14d-11 of the Exchange Act; provided that Merger Sub may, but shall not be required to, make available a “subsequent offering period” if Merger Sub has exercised the Top Up Option; provided further that in no event shall Merger Sub be required to extend the Offer is not beyond the Outside Date (as such date may be extended pursuant to Section 8.01(b)(i)). Notwithstanding the foregoing, in the event that all of the Offer Conditions (other than the condition set forth in clause (a) of Annex I hereto) are satisfied or waived on as of any otherwise scheduled expiration date of the OfferExpiration Date, Acquisition Sub shall extend the Offer from time to time until such conditions are satisfied or waived; PROVIDED that (i) each such extension of the Offer shall be for a period of not more than ten Business Days, and (ii) Acquisition Sub shall notMerger Sub, without the prior written consent of the CompanyCompany (provided that such consent has been approved by the Special Committee), may not extend the Offer beyond for more than ten Business Days. (e) Promptly following the Termination Date. Subject expiration of the Offer (and any subsequent offering period), subject to the foregoing and upon the terms and subject to the conditions of the OfferOffer and this Agreement, Acquisition Merger Sub shall, and Parent shall cause Merger Sub to, accept for payment and pay for, as promptly as practicable after the expiration practicable, all of the Offer, all Shares (i) validly tendered and not properly withdrawn pursuant to the Offer and (including if no Shares are ii) validly tendered and not withdrawn), but not in excess of any subsequent offering period. The time that Merger Sub accepts for payment the Maximum NumberShares tendered pursuant to the Offer is referred to herein as the “Acceptance Time”. (bf) As soon as practicable Subject to the terms and conditions of this Agreement, including the Offer Conditions, Parent shall provide or cause to be provided to Merger Sub on a timely basis all funds necessary to purchase any Shares that Merger Sub is obligated to purchase pursuant to Section 1.01(e). (g) The Offer Price shall be adjusted appropriately to reflect the effect of any stock split, reverse stock split, stock dividend (including any dividend or distribution of securities convertible into shares of Common Stock), reorganization, recapitalization, reclassification, combination, exchange of shares or other like change with respect to Common Stock occurring on or after the date of commencement this Agreement and prior to the Acceptance Time to provide each holder of Shares with the economic effect of the OfferOffer Price per Share. (h) Notwithstanding anything in this Agreement to the contrary, BMS Parent and Acquisition Merger Sub shall file with be entitled to deduct and withhold from the SEC a Tender consideration otherwise payable for Shares accepted for payment in the Offer Statement on Schedule TO (the "SCHEDULE TO"or any subsequent offering period) such amounts as Parent or Merger Sub are required to deduct and withhold with respect to the Offer making of such payment under the Internal Revenue Code of 1986, as amended (such Schedule TO and such documents included therein pursuant to which the Offer will be made, together with “Code”) or any supplements or amendments thereto, the "OFFER DOCUMENTS")other applicable provision of tax Law. BMS, Acquisition Sub and the Company each agrees promptly to correct any information provided by it for use in the Offer Documents if and to To the extent that such information shall have become false or misleading in any material respect. BMS amounts are so withheld and Acquisition Sub agree to take all steps necessary to cause the Schedule TO as so corrected to be filed with the SEC. BMS and Acquisition Sub shall deliver or cause to be delivered paid over to the Companyappropriate taxing authority by Parent or Merger Sub, or such other Person as the Company shall designate, the Offer Documents (and any amendments thereto) as so corrected, in such quantities as withheld amounts shall be necessary treated for dissemination to all holders purposes of Shares and Company Options. The Company shall, at its expense, cause the Offer Documents (and any amendments thereto) to be disseminated to holders of Shares and Company Options, in each case this Agreement as and having been paid to the extent required Person in respect of which such deduction and withholding was made by applicable federal securities laws. The Company and its counsel shall be given an opportunity to review and comment on the Offer Documents prior to their being filed with the SEC Parent or disseminated to the holders of Shares and Company Options. BMS and Acquisition Sub shall provide the Company and its counsel with any comments or other communications, whether written or oral, that BMS, Acquisition Sub or its counsel may receive from time to time from the SEC or its staff with respect to the Offer Documents promptly after receipt of such comments or other communicationsMerger Sub. (c) Each certificate for Shares issued to Acquisition Sub representing Shares accepted for purchase and paid for by Acquisition Sub in the Offer shall bear a legend in substantially the following form: THE SECURITIES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO RESTRICTIONS ON TRANSFER AS SET FORTH IN THE STOCKHOLDER AGREEMENT, DATED SEPTEMBER 19, 2001, AMONG IMCLONE SYSTEMS INCORPORATED, ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB COMPANY AND ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB BIOLOGICS COMPANY, A COPY OF WHICH MAY BE OBTAINED FROM THE CORPORATE SECRETARY OF IMCLONE SYSTEMS INCORPORATED.

The Offer. (a) As Provided that this Agreement shall not have been terminated in accordance with Section 8.1 hereof and none of the events set forth in Annex I hereto shall have occurred and be existing, Purchaser shall commence (within the meaning of Rule 14d-2 under the Securities Exchange Act of 1934, as amended (the "Exchange Act")) the Offer as promptly as practicable after the date hereofreasonably practicable, but in no event later than ten Business Days after seven business days following the date hereof, Acquisition Sub shall commence an offer (public announcement by Parent and the "OFFER") to purchase for cash 14,392,003 Shares (which shall include, for purposes Company of the execution of this Agreement, (i) all Shares issuable in respect of exercisable, in-the-money Company Options which have been "conditionally exercised" by the holder thereof for purposes of participating in the Offer, and (ii) all Shares issued prior to the expiration of the Offer upon the conversion of any convertible securities or upon the exercise of any options or warrants) (such number of Shares, the "MAXIMUM NUMBER") at a price of $70.00 per Share, net to the seller in cash (such price, as may hereafter be increased, the "OFFER PRICE"). The obligation of Acquisition Sub Purchaser to accept for payment and pay for any Shares tendered pursuant to the Offer shall be subject only to the satisfaction of the conditions set forth in Annex I hereto. The initial expiration date of the Offer shall be the twentieth Business Day following the commencement of the Offer (determined under Rule 14d-1(g)(3) promulgated under the 1934 Act). Acquisition Sub I. Purchaser expressly reserves the right from time to waive any of the conditions time, subject to the Offer, modify the terms of the Offer, Sections 1.1(b) and increase the Offer Price; PROVIDED that1.1(d) hereof, without the consent of the Company to waive any such condition, to increase the Per Share Amount, or to make any other changes in the terms and conditions of the Offer. The Per Share Amount shall be net to the seller in cash, without interest, subject to reduction only for any applicable withholding taxes or stock transfer taxes payable by the seller. The Company agrees that no Shares held by the Company or any Subsidiary (as hereinafter defined) will be tendered pursuant to the Offer. (b) Without the prior written consent of the Company, Acquisition Sub Purchaser shall not (i) increase decrease the Per Share Amount or reduce the Maximum Number, (ii) reduce the price per Share to be paid pursuant to the Offer, (iii) add to the conditions set forth in Annex I or modify any condition set forth in Annex I, (iv) change the form of consideration payable in the Offer, (ii) seek to purchase less than all outstanding Shares, (iii) amend or waive satisfaction of the Minimum Condition (as defined in Annex I) or (viv) otherwise impose conditions to the Offer in addition to those set forth in Annex I hereto, or amend any other term or condition of the Offer in any manner materially adverse to the holders of Shares. Acquisition Sub Upon the terms and subject to the conditions of the Offer and this Agreement, Purchaser will accept for payment and purchase, as soon as permitted under the terms of the Offer and applicable law (subject to the first proviso to Section 8.1(c)(i)) (the "Share Purchase Date") all Shares validly tendered and not withdrawn prior to the expiration of the Offer. On or prior to the Share Purchase Date, Parent shall provide or cause to be provided to Purchaser the funds necessary to pay for Shares that Purchaser becomes obligated to accept for payment, and pay for, pursuant to the Offer. Purchaser shall not provide for a subsequent offering period in accordance with Rule 14d-11 under the Exchange Act. (c) The Offer shall be made by means of an offer to purchase (the "Offer to Purchase") having only the conditions set forth in Annex I hereto. As soon as reasonably practicable on the date the Offer is commenced, Purchaser shall file with the Securities and Exchange Commission (the "SEC") a Tender Offer Statement on Schedule TO (together with all amendments and supplements thereto, the "Schedule TO") with respect to the Offer that will comply in all material respects with the provisions of all applicable Federal securities laws, and will contain (including as an exhibit) or incorporate by reference the Offer to Purchase and forms of the related letter of transmittal and summary advertisement (which documents, together with any supplements or amendments thereto, are referred to collectively herein as the "Offer Documents"). Parent and Purchaser agree promptly to correct the Schedule TO or the Offer Documents if and to the extent that it or they shall have become false or misleading in any material respect (and the Company, with respect to written information supplied by it specifically for use in the Schedule TO or the Offer Documents, shall promptly notify Parent of any required corrections of such information and shall cooperate with Parent and Purchaser with respect to correcting such information) and to supplement the Schedule TO or the Offer Documents to include any information that shall become necessary in order to make the statements therein, in light of the circumstances under which they were made, not misleading (and the Company shall supplement the information provided by it specifically for use in the Schedule TO or the Offer Documents to include any information that shall become necessary in order to make the statements therein that are based on such provided information, in light of the circumstances under which they were made, not misleading), and Parent and Purchaser further agree to take all steps necessary to cause the Schedule TO, as so corrected or supplemented, to be filed with the SEC and the Offer Documents, as so corrected or supplemented, to be disseminated to holders of Shares, in each case to the extent required by applicable Federal securities laws. The Company and its counsel shall be given a reasonable opportunity to review and comment on the Schedule TO and any Offer Documents before they are filed with the SEC. (d) The Offer to Purchase shall provide (i) for an initial expiration date of 20 business days (as defined in Rule 14d-1 under the Exchange Act) from and including the date of commencement of the Offer (the "Initial Expiration Date"). Purchaser shall extend the expiration date of the Offer until 5:00 p.m., Eastern time, on the earlier of (i) the thirtieth (30th) business day following the public announcement by Parent and the Company of the execution of this Agreement (which thirty business days shall for this purpose include the date of such public announcement) and (ii) if a tender offer (other than the Offer) shall have been commenced for all or a portion of the Shares, the business day immediately preceding the initial expiration date of such tender offer (such earlier date, the "Extended Expiration Date"). Unless this Agreement shall have been terminated pursuant to Section 8.1 hereof, Purchaser agrees that it shall not, without the consent of the Company, terminate or withdraw the Offer or (except as provided in this Section 1.1(d)) extend the expiration date of the Offer; provided, however, that, subject to the immediately following sentence, without the consent of the Company, Purchaser shall have the right to terminate or withdraw the Offer or extend the Offer from time to time if at the then-scheduled expiration date of the Offer the conditions to the Offer described in Annex I hereto shall not have been satisfied or earlier waived. Unless this Agreement shall have been terminated pursuant to Section 8.1, if at the then-scheduled expiration date of the Offer, the conditions to the Offer described in Annex I hereto (other than the Minimum Condition) shall not have been satisfied or earlier waived, upon the request of the Company, Purchaser shall from time to time extend the expiration date of the Offer for up to a maximum of 20 business days in the aggregate (it being understood and agreed that the period from the Initial Expiration Date to and including the Extended Expiration Date shall be counted in such 20-business-day period) for all such extensions (the period of each such extension to be determined by Purchaser), provided that at the time of such extension any such condition is reasonably capable of being satisfied and provided further that the failure of any such condition to be satisfied shall not result from a willful breach by the Company of any of its covenants and agreements contained in this Agreement, until the date Purchaser becomes obligated, pursuant to the terms of the Offer and this Agreement, to accept for payment and pay for Shares tendered pursuant to the Offer. Notwithstanding the foregoing, Purchaser may, without the consent of the Company, extend the expiration date of the Offer (as it may be extended) for any period required by any ruleapplicable rules, regulationregulations, interpretation interpretations or position positions of the SEC or the staff thereof applicable to the Offer or for any period required by applicable law. If any of the conditions to the Offer is not satisfied or waived on any scheduled expiration date of the Offer, Acquisition Sub shall extend the Offer from time to time until such conditions are satisfied or waived; PROVIDED that (i) each such extension of the Offer shall be for a period of not more than ten Business Days, and (ii) Acquisition Sub shall not, without the prior written consent of the Company, extend the Offer beyond the Termination Date. Subject to the foregoing and upon the terms and subject to the conditions of the Offer, Acquisition Sub shall accept for payment and pay for, as promptly as practicable after the expiration of the Offer, all Shares validly tendered and not withdrawn (including if no Shares are validly tendered and not withdrawn), but not in excess of the Maximum Number. (b) As soon as practicable on the date of commencement of the Offer, BMS and Acquisition Sub shall file with the SEC a Tender Offer Statement on Schedule TO (the "SCHEDULE TO") with respect to the Offer (such Schedule TO and such documents included therein pursuant to which the Offer will be made, together with any supplements or amendments thereto, the "OFFER DOCUMENTS"). BMS, Acquisition Sub and the Company each agrees promptly to correct any information provided by it for use in the Offer Documents if and to the extent that such information shall have become false or misleading in any material respect. BMS and Acquisition Sub agree to take all steps necessary to cause the Schedule TO as so corrected to be filed with the SEC. BMS and Acquisition Sub shall deliver or cause to be delivered to the Company, or such other Person as the Company shall designate, the Offer Documents (and any amendments thereto) as so corrected, in such quantities as shall be necessary for dissemination to all holders of Shares and Company Options. The Company shall, at its expense, cause the Offer Documents (and any amendments thereto) to be disseminated to holders of Shares and Company Options, in each case as and to the extent required by applicable federal securities laws. The Company and its counsel shall be given an opportunity to review and comment on the Offer Documents prior to their being filed with the SEC or disseminated to the holders of Shares and Company Options. BMS and Acquisition Sub shall provide the Company and its counsel with any comments or other communications, whether written or oral, that BMS, Acquisition Sub or its counsel may receive from time to time from the SEC or its staff with respect to the Offer Documents promptly after receipt of such comments or other communications. (c) Each certificate for Shares issued to Acquisition Sub representing Shares accepted for purchase and paid for by Acquisition Sub in the Offer shall bear a legend in substantially the following form: THE SECURITIES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO RESTRICTIONS ON TRANSFER AS SET FORTH IN THE STOCKHOLDER AGREEMENT, DATED SEPTEMBER 19, 2001, AMONG IMCLONE SYSTEMS INCORPORATED, ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB COMPANY AND ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB BIOLOGICS COMPANY, A COPY OF WHICH MAY BE OBTAINED FROM THE CORPORATE SECRETARY OF IMCLONE SYSTEMS INCORPORATED.

The Offer. (a) As promptly as practicable after the date hereof, of this Agreement but in no event later than ten Business Days after the date hereofDecember 29, Acquisition 2020, Merger Sub shall (and Parent shall cause Merger Sub to) commence an offer (within the "OFFER"meaning of Rule 14d-2 under the Exchange Act) to purchase for cash 14,392,003 Shares the Offer. (which shall include, for purposes b) In accordance with the terms and conditions of this Agreement, (i) all Shares issuable in respect of exercisable, in-the-money Company Options which have been "conditionally exercised" by the holder thereof for purposes of participating in the Offer, and (ii) all Shares issued prior to the expiration of the Offer upon the conversion of any convertible securities or upon the exercise of any options or warrants) (such number of Shares, the "MAXIMUM NUMBER") at a price of $70.00 per Share, net to the seller in cash (such price, as may hereafter be increased, the "OFFER PRICE"). The obligation of Acquisition Sub to accept for payment any Shares tendered pursuant to the Offer shall be subject only to the satisfaction or waiver (to the extent such waiver is permitted by applicable Law) of the conditions set forth in Annex I hereto(collectively, the “Offer Conditions”), Merger Sub shall (and Parent shall cause Merger Sub to), at or as promptly as practicable following the Expiration Time, irrevocably accept for payment (the time of acceptance for payment, the “Offer Acceptance Time”) and, at or as promptly as practicable following the Offer Acceptance Time (but in any event within three Business Days (calculated as set forth in Rule 14d-1(g)(3) under the Exchange Act) thereafter) pay for all Shares validly tendered and not properly withdrawn pursuant to the Offer. Parent shall provide or cause to be provided to Merger Sub, at the Offer Acceptance Time and on a timely basis at all times thereafter, the funds necessary to purchase any Shares that Merger Sub becomes obligated to purchase pursuant to the Offer. (c) The initial expiration date of the Offer shall be made by means of an offer to purchase (the twentieth Business Day following “Offer to Purchase”) in accordance with the commencement of terms set forth in this Agreement and subject only to the Minimum Condition and the other Offer (determined under Rule 14d-1(g)(3) promulgated under the 1934 Act)Conditions. Acquisition Merger Sub expressly reserves the right to waive any of the conditions to the Offer, modify the terms of the Offer, and (i) increase the Offer Price, (ii) waive any Offer Condition other than the Minimum Condition and (iii) make any other changes to the terms and conditions of the Offer not inconsistent with the terms of this Agreement; PROVIDED thatprovided, however, that unless otherwise expressly provided by this Agreement, without the prior written consent of the Company, Acquisition Merger Sub shall not, and Parent shall cause Merger Sub not (i) increase or reduce the Maximum Numberto, (iiA) reduce decrease the price per Share to be paid pursuant to the OfferOffer Price, (iii) add to the conditions set forth in Annex I or modify any condition set forth in Annex I, (ivB) change the form of consideration payable in the Offer, (C) decrease the maximum number of Shares sought to be purchased in the Offer, (D) impose any conditions to the Offer other than the Offer Conditions, (E) amend, modify or supplement any of the Offer Conditions in a manner that makes such Offer Condition more difficult to satisfy, (F) amend, modify or waive the Minimum Condition, (G) except as otherwise required or expressly permitted by Section 2.01(e), extend or otherwise change the Expiration Time, (H) provide for any “subsequent offering period” within the meaning of Rule 14d-11 under the Exchange Act, or (vI) otherwise amend amend, modify or supplement any of the other material terms of the Offer in a manner that makes the Offer Conditions more difficult to satisfy, except for actions described in any manner adverse of clauses (A) through (I) that are (1) expressly required by this Agreement, (2) required by Law or (3) taken in response to written comments or questions received from the SEC. The Offer may not be terminated prior to its scheduled Expiration Time, unless this Agreement is terminated in accordance with Article VIII. (d) The Offer shall expire at midnight (New York time) (i.e., one minute after 11:59 p.m. (New York time)) on the date that is 30 Business Days (calculated in accordance with Rule 14d-1(g)(3) under the Exchange Act) following the commencement (within the meaning of Rule 14d-2 under the Exchange Act) of the Offer (such initial expiration date and time of the Offer, the “Initial Expiration Time”) or, if the Offer has been extended pursuant to and in accordance with Section 2.01(e), the date and time to which the Offer has been so extended (the Initial Expiration Time, or such later expiration date and time to which the Offer has been so extended, the “Expiration Time”). (e) Merger Sub shall, and Parent shall cause Merger Sub to, extend the Offer from time to time as follows: (i) If, at the then-scheduled Expiration Time, any of the Offer Conditions has not been satisfied or waived by Parent and Merger Sub (to the holders extent such waiver is permitted under this Agreement and applicable Law), then Merger Sub shall, and Parent shall cause Merger Sub to, extend the Offer on one or more occasions in consecutive increments of Shares. Acquisition up to 10 Business Days each (each such increment to end at 5:00 p.m., New York time, on the last Business Day of such increment) in order to permit the satisfaction of such Offer Condition(s); and (ii) Merger Sub shall extend the Offer for any the minimum period required by any rule, regulationapplicable Law, interpretation or position of the SEC or the its staff thereof applicable or NASDAQ or its staff; provided, however, that, in each case, in no event shall Merger Sub be required to the Offer or any period required by applicable law. If any of the conditions to the Offer is not satisfied or waived on any scheduled expiration date of the Offer, Acquisition Sub shall extend the Offer from time to time until such conditions are satisfied or waived; PROVIDED that (i) each such extension of the Offer shall be for a period of not more than ten Business Days, and (ii) Acquisition Sub shall not, without the prior written consent of the Company, extend the Offer beyond the Termination earliest to occur of (x) the termination of this Agreement pursuant to Article VIII and (y) the End Date. Subject . (f) The Offer Price shall be adjusted appropriately and proportionately to reflect the effect of any stock split, reverse stock split, stock dividend (including any dividend or other distribution of securities convertible into Shares), reorganization, recapitalization, reclassification, combination, exchange of shares or other like change with respect to the foregoing Shares occurring on or after the date hereof and upon at or prior to the Offer Acceptance Time, and such adjustment to the Offer Price shall provide to the holders of Shares the same economic effect as contemplated by this Agreement prior to such action; provided that nothing in this Section 2.01(f) shall be construed to permit the Company or any other Person to take any action except to the extent consistent with, and not otherwise limited or prohibited by, the terms and subject to the conditions of this Agreement (g) In the Offerevent that this Agreement is terminated in accordance with Article VIII, Acquisition Merger Sub shall accept for payment (and pay for, Parent shall cause Merger Sub to) as promptly as practicable after the expiration (and in any event within 24 hours of such termination) irrevocably and unconditionally terminate the Offer, shall not acquire any Shares pursuant to the Offer and shall cause any depositary acting on behalf of Parent or Merger Sub to return, in accordance with applicable Law, all tendered Shares validly tendered and not withdrawn (including if no Shares are validly tendered and not withdrawn), but not in excess of to the Maximum Numberregistered holders thereof. (bh) As soon promptly as practicable on the date of commencement of the OfferOffer (within the meaning of Rule 14d-2 under the Exchange Act), BMS Parent and Acquisition Merger Sub shall (i) file with the SEC a Tender Offer Statement on Schedule TO (the "SCHEDULE TO") with respect to the Offer (such together with all exhibits, amendments and supplements thereto, the “Schedule TO TO”) that will contain or incorporate by reference the Offer to Purchase and such form of the related letter of transmittal (the Schedule TO, together with all documents included therein pursuant to which the Offer will be made, together with any supplements or amendments theretothe “Offer Documents”) and (ii) cause the Offer Documents to be disseminated to holders of Shares. Each of Parent, the "OFFER DOCUMENTS"). BMS, Acquisition Merger Sub and the Company each agrees shall promptly to correct any information provided by it for use in the Offer Documents if and to the extent that such information shall have become false or misleading in any material respect. BMS , and Acquisition Sub agree Parent shall use reasonable efforts to take all steps necessary to promptly cause the Schedule TO Offer Documents as so corrected to be filed with the SEC. BMS SEC and Acquisition Sub shall deliver or cause to be delivered to the Company, or such other Person as the Company shall designate, the Offer Documents (and any amendments thereto) as so corrected, in such quantities as shall be necessary for dissemination to all holders of Shares and Company Options. The Company shall, at its expense, cause the Offer Documents (and any amendments thereto) to promptly be disseminated to holders of Shares and Company OptionsShares, in each case as and to the extent required by applicable federal securities lawsLaw. The Company shall promptly furnish or otherwise make available to Parent, Merger Sub or Parent’s counsel any information concerning the Company and the Company’s Subsidiaries that is required by the Exchange Act to be set forth in the Offer Documents. The Company and its counsel shall be given an reasonable opportunity to review and comment on the Offer Documents prior to their being filed the filing thereof with the SEC or disseminated SEC. Parent and Merger Sub agree to the holders of Shares and Company Options. BMS and Acquisition Sub shall provide the Company and its counsel with any comments or other communications(including a summary of any oral comments) that Parent, whether written or oral, that BMS, Acquisition Merger Sub or its their counsel may receive from time to time from the SEC or its staff with respect to the Offer Documents promptly after receipt of such comments. Each of Parent and Merger Sub shall give the Company and its counsel a reasonable opportunity to participate in the response to any comments of the SEC or other communicationsits staff with respect to the Offer Documents and shall respond promptly to any such comments. (ci) Each certificate for Shares issued Parent, Merger Sub and the Paying Agent with respect to Acquisition Sub representing Shares accepted for purchase and paid for by Acquisition Sub in the Offer shall bear a legend be entitled to deduct and withhold from the Offer Price payable pursuant to the Offer such amounts as are required to be deducted and withheld with respect to the making of such payment under the Code, the U.S. Treasury Regulations promulgated thereunder, or any provision of state, local or non-U.S. Tax Law. To the extent amounts are so withheld and paid over to the appropriate Taxing Authority, the withheld amounts shall be treated for all purposes of this Agreement as having been paid to the person in substantially the following form: THE SECURITIES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO RESTRICTIONS ON TRANSFER AS SET FORTH IN THE STOCKHOLDER AGREEMENT, DATED SEPTEMBER 19, 2001, AMONG IMCLONE SYSTEMS INCORPORATED, ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB COMPANY AND ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB BIOLOGICS COMPANY, A COPY OF WHICH MAY BE OBTAINED FROM THE CORPORATE SECRETARY OF IMCLONE SYSTEMS INCORPORATEDrespect of which such deduction and withholding was made.

The Offer. (a) As promptly as practicable after the date hereof, but in no event later than ten Business Days after the date hereof, Acquisition Sub shall commence an offer (the "OFFER") to purchase for cash 14,392,003 Shares (which shall include, for purposes of this Agreement, (i) Provided that Parent and Purchaser shall not have delivered (and been entitled to deliver) a notice of the Company’s breach with respect to the Company’s obligations under Section 6.3 (unless all Shares issuable in respect of exercisable, in-the-money Company Options which such breaches set forth therein shall have been "conditionally exercised" by the holder thereof for purposes of participating in the Offercured) Purchaser shall, and Parent shall cause Purchaser to commence (iiwithin the meaning of Rule 14d-2 under the Securities Exchange Act of 1934, as amended (the “Exchange Act”)), not later than July 2, 2008 (provided that the Company shall be prepared to disseminate to its stockholders its Schedule 14d-9 and Schedule 14f-1 within such time period) all Shares issued prior to the expiration of the Offer upon to purchase all outstanding Shares at the conversion of any convertible securities or upon the exercise of any options or warrants) (such number of Shares, the "MAXIMUM NUMBER") at a price of $70.00 per Share, net to the seller in cash (such price, as may hereafter be increased, the "OFFER PRICE")Offer Price. The obligation obligations of Acquisition Sub Purchaser (and of Parent to cause Purchaser) to accept for payment and to pay for any Shares validly tendered (and not withdrawn) pursuant to the Offer shall be subject only to the satisfaction or waiver of those conditions set forth in Annex I heretoExhibit A (the “Offer Conditions”). The initial expiration date of the Offer shall be July 30, 2008 (the twentieth Business Day following “Expiration Date”, unless Purchaser shall have extended the commencement period of time for which the Offer (determined under Rule 14d-1(g)(3) promulgated under is open pursuant to, and in accordance with, Section 1.1(a)(iii), in which event the 1934 Actterm “Expiration Date” shall mean the latest time and date as the Offer, as so extended, may expire). Acquisition Sub Purchaser expressly reserves the right (but shall not be obligated) at any time or from time to time in its sole discretion to waive any of the conditions to the Offer, Offer Condition or modify or amend the terms of the Offer, and increase the Offer Price; PROVIDED except that, without the consent of the Company, Acquisition Sub shall not (i) increase or reduce the Maximum Number, (ii) reduce the price per Share to be paid pursuant to the Offer, (iii) add to the conditions set forth in Annex I or modify any condition set forth in Annex I, (iv) change the form of consideration payable in the Offer, or (v) otherwise amend the Offer in any manner adverse to the holders of Shares. Acquisition Sub shall extend the Offer for any period required by any rule, regulation, interpretation or position of the SEC or the staff thereof applicable to the Offer or any period required by applicable law. If any of the conditions to the Offer is not satisfied or waived on any scheduled expiration date of the Offer, Acquisition Sub shall extend the Offer from time to time until such conditions are satisfied or waived; PROVIDED that (i) each such extension of the Offer shall be for a period of not more than ten Business Days, and (ii) Acquisition Sub shall not, without the prior written consent of the Company, extend Purchaser shall not (A) decrease the Offer beyond Price or change the Termination Date. Subject form of the consideration payable in the Offer, (B) decrease the number of Shares sought pursuant to the foregoing and upon Offer, (C) amend or waive the terms and subject Minimum Tender Condition (as defined in Exhibit A), (D) add to the conditions of set forth on Exhibit A, (E) modify the Offer, Acquisition Sub shall accept for payment and pay for, as promptly as practicable after the expiration of the Offer, all Shares validly tendered and not withdrawn (including if no Shares are validly tendered and not withdrawn), but not conditions set forth on Exhibit A in excess of the Maximum Number. (b) As soon as practicable on the date of commencement of the Offer, BMS and Acquisition Sub shall file with the SEC a Tender Offer Statement on Schedule TO (the "SCHEDULE TO") with respect to the Offer (such Schedule TO and such documents included therein pursuant to which the Offer will be made, together with any supplements or amendments thereto, the "OFFER DOCUMENTS"). BMS, Acquisition Sub and the Company each agrees promptly to correct any information provided by it for use in the Offer Documents if and to the extent that such information shall have become false or misleading in any material respect. BMS and Acquisition Sub agree to take all steps necessary to cause the Schedule TO as so corrected to be filed with the SEC. BMS and Acquisition Sub shall deliver or cause to be delivered to the Company, or such other Person as the Company shall designate, the Offer Documents (and any amendments thereto) as so corrected, in such quantities as shall be necessary for dissemination to all holders of Shares and Company Options. The Company shall, at its expense, cause the Offer Documents (and any amendments thereto) to be disseminated to holders of Shares and Company Options, in each case as and to the extent required by applicable federal securities laws. The Company and its counsel shall be given an opportunity to review and comment on the Offer Documents prior to their being filed with the SEC or disseminated manner adverse to the holders of Shares and Company Options. BMS and Acquisition Sub shall provide or in a manner that would delay consummation of the Company and its counsel with any comments or other communicationsOffer, whether written or oral, that BMS, Acquisition Sub or its counsel may receive from (F) reduce the time to time from the SEC or its staff with respect to the Offer Documents promptly after receipt of such comments or other communications. (c) Each certificate for Shares issued to Acquisition Sub representing Shares accepted for purchase and paid for by Acquisition Sub in period during which the Offer shall bear a legend remain open, or (G) extend the Expiration Date except as required or permitted by Section 1.1(a)(iii). If, prior to the Purchase Time, this Agreement is terminated in substantially accordance with Article VIII, Purchaser shall (notwithstanding clause (F) of the following form: THE SECURITIES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO RESTRICTIONS ON TRANSFER AS SET FORTH IN THE STOCKHOLDER AGREEMENT, DATED SEPTEMBER 19, 2001, AMONG IMCLONE SYSTEMS INCORPORATED, ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB COMPANY AND ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB BIOLOGICS COMPANY, A COPY OF WHICH MAY BE OBTAINED FROM THE CORPORATE SECRETARY OF IMCLONE SYSTEMS INCORPORATEDprevious sentence) promptly terminate the Offer without accepting any Shares for payment and shall return the Shares tendered promptly after such termination.

The Offer. (a) As promptly as practicable after the date hereof, of this Agreement but in no event later than ten Business Days after the date hereofApril 26, Acquisition 2021, Merger Sub shall (and Parent shall cause Merger Sub to) commence an offer (within the "OFFER"meaning of Rule 14d-2 under the Exchange Act) to purchase for cash 14,392,003 Shares the Offer. (which shall include, for purposes b) In accordance with the terms and conditions of this Agreement, (i) all Shares issuable in respect of exercisable, in-the-money Company Options which have been "conditionally exercised" by the holder thereof for purposes of participating in the Offer, and (ii) all Shares issued prior to the expiration of the Offer upon the conversion of any convertible securities or upon the exercise of any options or warrants) (such number of Shares, the "MAXIMUM NUMBER") at a price of $70.00 per Share, net to the seller in cash (such price, as may hereafter be increased, the "OFFER PRICE"). The obligation of Acquisition Sub to accept for payment any Shares tendered pursuant to the Offer shall be subject only to the satisfaction or waiver (to the extent such waiver is permitted by applicable Law) of the conditions set forth in Annex I hereto(collectively, the “Offer Conditions”), Merger Sub shall (and Parent shall cause Merger Sub to), at or as promptly as practicable following the Expiration Time, irrevocably accept for payment (the time of acceptance for payment, the “Offer Acceptance Time”) and, at or as promptly as practicable following the Offer Acceptance Time (but in any event within two Business Days (calculated as set forth in Rule 14d-1(g)(3) under the Exchange Act) thereafter) pay for all Shares validly tendered and not properly withdrawn pursuant to the Offer. Parent shall provide or cause to be provided to Merger Sub, at the Offer Acceptance Time and on a timely basis at all times thereafter, the funds necessary to purchase any Shares that Merger Sub becomes obligated to purchase pursuant to the Offer. (c) The initial expiration date of the Offer shall be made by means of an offer to purchase (the twentieth Business Day following “Offer to Purchase”) in accordance with the commencement of terms set forth in this Agreement and subject only to the Minimum Condition and the other Offer (determined under Rule 14d-1(g)(3) promulgated under the 1934 Act)Conditions. Acquisition Merger Sub expressly reserves the right to waive any of the conditions to the Offer, modify the terms of the Offer, and (i) increase the Offer Price, (ii) waive any Offer Condition other than the Minimum Condition and (iii) make any other changes to the terms and conditions of the Offer not inconsistent with the terms of this Agreement; PROVIDED provided, however, that, without the prior written consent of the Company, Acquisition Merger Sub shall not, and Parent shall cause Merger Sub not (i) increase or reduce the Maximum Numberto, (iiA) reduce decrease the price per Share to be paid pursuant to the OfferOffer Price, (iii) add to the conditions set forth in Annex I or modify any condition set forth in Annex I, (ivB) change the form of consideration payable in the Offer, (C) decrease the maximum number of Shares sought to be purchased in the Offer, (D) impose any conditions to the Offer other than the Offer Conditions, (E) amend, modify or supplement any of the Offer Conditions in a manner that makes such Offer Condition more difficult to satisfy, (F) amend, modify or waive the Minimum Condition, (G) except as otherwise required or expressly permitted by Section 2.01(e), extend or otherwise change the Expiration Time, (H) provide for any “subsequent offering period” within the meaning of Rule 14d-11 under the Exchange Act, or (vI) otherwise amend amend, modify or supplement any of the other terms of the Offer in any a manner adverse to the holders of Shares. Acquisition The Offer may not be terminated prior to its scheduled Expiration Time, unless this Agreement is terminated in accordance with Article VIII. (d) The Offer shall expire at midnight (New York time) (i.e., one minute after 11:59 p.m. (New York time)) on the date that is 20 Business Days (calculated in accordance with Rule 14d-1(g)(3) under the Exchange Act) following the commencement (within the meaning of Rule 14d-2 under the Exchange Act) of the Offer (such initial expiration date and time of the Offer, the “Initial Expiration Time”) or, if the Offer has been extended pursuant to and in accordance with Section 2.01(e), the date and time to which the Offer has been so extended (the Initial Expiration Time, or such later expiration date and time to which the Offer has been so extended, the “Expiration Time”). (e) Merger Sub shall, and Parent shall cause Merger Sub to, extend the Offer from time to time as follows: (i) If, at the then-scheduled Expiration Time, any of the Offer Conditions has not been satisfied or waived by Parent and Merger Sub (to the extent such waiver is permitted under this Agreement and applicable Law), then Merger Sub shall, and Parent shall cause Merger Sub to, extend the Offer on one or more occasions in consecutive increments of up to 5 Business Days (or such longer period with the prior consent of the Company (not to be unreasonably withheld, conditioned or delayed)) each (each such increment to end at 5:00 p.m., New York time, on the last Business Day of such increment) in order to permit the satisfaction of such Offer Condition(s); and (ii) Merger Sub shall, and Parent shall cause Merger Sub to, extend the Offer for any the minimum period required by any rule, regulationapplicable Law, interpretation or position of the SEC or the its staff thereof applicable or NASDAQ or its staff; provided, however, that, in each case, in no event shall Merger Sub be required to the Offer or any period required by applicable law. If any of the conditions to the Offer is not satisfied or waived on any scheduled expiration date of the Offer, Acquisition Sub shall extend the Offer from time to time until such conditions are satisfied or waived; PROVIDED that (i) each such extension of the Offer shall be for a period of not more than ten Business Days, and (ii) Acquisition Sub shall notor, without the prior written consent of the CompanyCompany (not to be unreasonably withheld, conditioned or delayed), be permitted to extend the Offer beyond the Termination earliest to occur of (x) the termination of this Agreement pursuant to Article VIII and (y) the End Date. Subject . (f) The Offer Price shall be adjusted appropriately and proportionately to reflect the effect of any stock split, reverse stock split, stock dividend (including any dividend or other distribution of securities convertible into Shares), reorganization, recapitalization, reclassification, combination, exchange of shares or other like change with respect to the foregoing Shares occurring on or after the date hereof and upon at or prior to the Offer Acceptance Time, and such adjustment to the Offer Price shall provide to the holders of Shares the same economic effect as contemplated by this Agreement prior to such action; provided that nothing in this Section 2.01(f) shall be construed to permit the Company or any other Person to take any action except to the extent consistent with, and not otherwise limited or prohibited by, the terms and subject to the conditions of this Agreement (g) In the Offerevent that this Agreement is terminated in accordance with Article VIII, Acquisition Merger Sub shall accept for payment (and pay for, Parent shall cause Merger Sub to) as promptly as practicable after the expiration (and in any event within 24 hours of such termination) irrevocably and unconditionally terminate the Offer, shall not acquire any Shares pursuant to the Offer and shall cause any depositary acting on behalf of Parent or Merger Sub to return, in accordance with applicable Law, all tendered Shares validly tendered and not withdrawn (including if no Shares are validly tendered and not withdrawn), but not in excess of to the Maximum Numberregistered holders thereof. (bh) As soon promptly as practicable on the date of commencement of the OfferOffer (within the meaning of Rule 14d-2 under the Exchange Act), BMS Parent and Acquisition Merger Sub shall (i) file with the SEC a Tender Offer Statement on Schedule TO (the "SCHEDULE TO") with respect to the Offer (such together with all exhibits, amendments and supplements thereto, the “Schedule TO TO”) that will contain or incorporate by reference the Offer to Purchase and such form of the related letter of transmittal (the Schedule TO, together with all documents included therein pursuant to which the Offer will be made, together with any supplements or amendments theretothe “Offer Documents”) and (ii) cause the Offer Documents to be disseminated to holders of Shares. Each of Parent, the "OFFER DOCUMENTS"). BMS, Acquisition Merger Sub and the Company each agrees shall promptly to correct any information provided by it for use in the Offer Documents if and to the extent that such information shall have become false or misleading in any material respect. BMS , and Acquisition Sub agree Parent shall use reasonable efforts to take all steps necessary to promptly cause the Schedule TO Offer Documents as so corrected to be filed with the SEC. BMS SEC and Acquisition Sub shall deliver or cause to be delivered to the Company, or such other Person as the Company shall designate, the Offer Documents (and any amendments thereto) as so corrected, in such quantities as shall be necessary for dissemination to all holders of Shares and Company Options. The Company shall, at its expense, cause the Offer Documents (and any amendments thereto) to promptly be disseminated to holders of Shares and Company OptionsShares, in each case as and to the extent required by applicable federal securities lawsLaw. The Company shall promptly furnish or otherwise make available to Parent, Merger Sub or Parent’s counsel any information concerning the Company and the Company’s Subsidiaries that is required by the Exchange Act or advisable to be set forth in the Offer Documents. The Company and its counsel shall be given an reasonable opportunity to review and comment on the Offer Documents prior to their being filed the filing thereof with the SEC or disseminated SEC. Parent and Merger Sub agree to the holders of Shares and Company Options. BMS and Acquisition Sub shall provide the Company and its counsel with any comments or other communications(including a summary of any oral comments) that Parent, whether written or oral, that BMS, Acquisition Merger Sub or its their counsel may receive from time to time from the SEC or its staff with respect to the Offer Documents promptly after receipt of such comments. Each of Parent and Merger Sub shall give the Company and its counsel a reasonable opportunity to participate in the response to any comments of the SEC or other communicationsits staff with respect to the Offer Documents and shall respond promptly to any such comments. (ci) Each certificate for Shares issued Parent, Merger Sub and the Paying Agent with respect to Acquisition Sub representing Shares accepted for purchase and paid for by Acquisition Sub in the Offer shall bear a legend be entitled to deduct and withhold from the Offer Price payable pursuant to the Offer such amounts as are required to be deducted and withheld with respect to the making of such payment under the Code, the U.S. Treasury Regulations promulgated thereunder, or any provision of state, local or non-U.S. Tax Law. To the extent amounts are so withheld and paid over to the appropriate Taxing Authority, the withheld amounts shall be treated for all purposes of this Agreement as having been paid to the person in substantially the following form: THE SECURITIES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO RESTRICTIONS ON TRANSFER AS SET FORTH IN THE STOCKHOLDER AGREEMENT, DATED SEPTEMBER 19, 2001, AMONG IMCLONE SYSTEMS INCORPORATED, ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB COMPANY AND ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB BIOLOGICS COMPANY, A COPY OF WHICH MAY BE OBTAINED FROM THE CORPORATE SECRETARY OF IMCLONE SYSTEMS INCORPORATEDrespect of which such deduction and withholding was made.

The Offer. (a) As promptly as practicable after the date hereof, but Provided that this Agreement has not been validly terminated in no event later than ten Business Days after the date hereof, Acquisition Sub shall commence an offer (the "OFFER") to purchase for cash 14,392,003 Shares (which shall include, for purposes accordance with Section 8 of this Agreement, (i) all Shares issuable in respect of exercisable, in-the-money Company Options which have been "conditionally exercised" by the holder thereof for purposes of participating in the OfferMerger Sub will, and Parent will cause Merger Sub to, commence (iiwithin the meaning of Rule 14d-2 promulgated under the Securities Exchange Act of 1934, as amended (together with the rules and regulations promulgated thereunder, the “Exchange Act”)), the Offer no later than the tenth (10th) all business day following the date of this Agreement. The obligations of Merger Sub to accept for payment and to pay for any Shares issued validly tendered and not withdrawn prior to the expiration of the Offer upon the conversion of any convertible securities or upon the exercise of any options or warrants(as it may be extended in accordance with this Section 1.1(a)) (such number of Shares, the "MAXIMUM NUMBER") at a price of $70.00 per Share, net to the seller in cash (such price, as may hereafter be increased, the "OFFER PRICE"). The obligation of Acquisition Sub to accept for payment any Shares tendered pursuant to the Offer shall will be subject only to the conditions set forth in Annex I heretoII (each such condition, an “Offer Condition”). The initial expiration date Subject to the prior satisfaction or waiver by Parent and Merger Sub of the Offer shall be Conditions, Merger Sub will consummate the twentieth Business Day Offer in accordance with the terms of such Offer, and accept for payment and pay for all Shares tendered and not withdrawn promptly following the commencement acceptance of Shares for payment in accordance with the Offer. The Offer will be made by an offer to purchase (the “Offer to Purchase”) that contains the terms set forth in this Agreement and the Offer (determined under Rule 14d-1(g)(3) promulgated under Conditions. Parent and Merger Sub shall cause the 1934 Act)Acceptance Time to be 12:01 AM ET on the business day that immediately follows the Expiration Date. Acquisition Parent and Merger Sub expressly reserves reserve the right to waive any of the conditions such conditions, to the Offer, modify the terms of the Offer, and increase the Offer Price; PROVIDED that, without the consent of the Company, Acquisition Sub shall not (i) increase or reduce the Maximum Number, (ii) reduce the price per Share Price and to be paid pursuant to make any other changes in the Offer. Merger Sub will not, (iii) add to and Parent will cause Merger Sub not to, decrease the conditions set forth in Annex I or modify any condition set forth in Annex IOffer Price, (iv) change the form of consideration payable in the Offer, decrease the number of Shares sought in the Offer, amend, modify or (v) otherwise amend waive the Offer Minimum Condition, impose additional conditions to, or amend, modify or waive the conditions in any a manner adverse to the holders any holder of Shares. Acquisition Sub shall extend the Offer for any period required by any rule, regulation, interpretation or position of the SEC or the staff thereof applicable to the Offer or any period required by applicable law. If any of the conditions to the Offer is not satisfied or waived on any scheduled expiration date of the Offer, Acquisition Sub shall extend the Offer from time to time until such conditions are satisfied or waived; PROVIDED that (i) each such extension of the Offer shall be provide for a period of not more than ten Business Days“subsequent offering period” in accordance with Rule 14d-11 promulgated under the Exchange Act, and (ii) Acquisition Sub shall notexcept as set forth below, in each case, without the prior written consent of the Company. Notwithstanding anything to the contrary contained in this Agreement, but subject to the parties’ respective termination rights under Section 8: (i) Merger Sub shall extend the Offer (A) for any extension period required by any rule, regulation or interpretation of the U.S. Securities and Exchange Commission (the “SEC”), its staff or the New York Stock Exchange (the “NYSE”), the Nasdaq Stock Market or their respective staffs, (B) for one or more extension periods of up to ten (10) business days per extension period (or a longer extension period approved by the Company), if, as of the applicable Expiration Date, either (I) any waiting period (and any extensions thereof) or any approvals or clearances applicable to the Offer or the consummation of the Merger in accordance with the HSR Act have not expired, been terminated or been obtained, as applicable or (II) any of the Offer Conditions set forth in Section 1 or Section 2 of Annex II hereof is not satisfied; and (C) for up to two (2) successive extension periods of ten (10) business days per extension period, if, at the applicable Expiration Date, (I) there has not been a Company Adverse Recommendation Change, (II) each Offer Condition other than the Minimum Condition is capable of being satisfied, and (III) the Minimum Condition is not satisfied; and (ii) Merger Sub, without the consent of the Company, may extend the Offer if, as of any Expiration Date, any Offer Condition is not satisfied and has not been irrevocably waived by Parent and Merger Sub in writing, for additional periods of up to ten (10) business days per extension period (or a longer extension period as may be approved in advance by the Company), to permit all of the Offer Conditions to be satisfied; provided, however, that in no event will Merger Sub be required to extend the Offer beyond the Termination Datevalid termination of this Agreement in compliance with Section 8. Subject Merger Sub will not terminate the Offer prior to any scheduled Expiration Date without the foregoing and upon prior written consent of the Company except in the event that this Agreement is terminated pursuant to Section 8. In addition, in the event this Agreement is terminated in accordance with the terms of Section 8, Merger Sub will at such time irrevocably and subject to the conditions of unconditionally terminate the Offer, Acquisition Sub shall accept for payment and pay for, as promptly as practicable after the expiration of the Offer, all Shares validly tendered and not withdrawn (including if no Shares are validly tendered and not withdrawn), but not in excess of the Maximum Number. (b) As soon as practicable on On the date of commencement of the Offer, BMS Parent and Acquisition Merger Sub shall will file with the SEC SEC, in accordance with Regulation M-A promulgated under the Exchange Act, a Tender Offer Statement on Schedule TO (the "SCHEDULE TO") with respect to the Offer (such together with all amendments, supplements and exhibits thereto, the “Schedule TO”). The Schedule TO and such documents included therein pursuant to which will include, as exhibits, the Offer will be madeto Purchase and a form of letter of transmittal and summary advertisement and all information required by applicable Law (collectively, together with any amendments and supplements or amendments thereto, the "OFFER DOCUMENTS"“Offer Documents”). BMSSubject to Section 5.2, Acquisition Sub the Company hereby consents to the inclusion in the Offer Documents of the recommendation and the approval of the Company Board of Directors referenced in Section 3.3(b). Subject to the Company’s compliance in all material respects with Section 1.2(c), Parent and Merger Sub will take all actions necessary to cause the Offer Documents to be filed with the SEC and disseminated to holders of the Shares, in each agrees case, as and to the extent required by Law. Parent, on the one hand, and the Company, on the other hand, will promptly to correct any information provided by it for use in the Offer Documents if and to the extent that such information shall will have become false or misleading in any material respectrespect or as otherwise required by Law. BMS Parent and Acquisition Merger Sub agree to will take all steps actions necessary to cause the Schedule TO Offer Documents as so corrected to be filed with the SEC. BMS SEC and Acquisition Sub shall deliver or cause to be delivered to the Company, or such other Person as the Company shall designate, the Offer Documents (and any amendments thereto) as so corrected, in such quantities as shall be necessary for dissemination to all holders of Shares and Company Options. The Company shall, at its expense, cause the Offer Documents (and any amendments thereto) to be disseminated to holders of Shares and Company Optionsthe Shares, in each case case, as and to the extent required by applicable federal securities lawsLaw. The Company and its counsel shall will be given an a reasonable opportunity to review and comment on the Offer Documents prior to their being Schedule TO and any amendment thereto before it is filed with the SEC or disseminated to the holders of Shares SEC, and Company OptionsParent and Merger Sub will consider any such comments in good faith. BMS In addition, Parent and Acquisition Merger Sub shall will provide the Company and its counsel with any comments or other communicationscomments, whether written or oral, that BMSParent, Acquisition Merger Sub or its their counsel may receive from time to time prior to the expiration or termination of the Offer, from the SEC or its staff with respect to the Offer Documents Documents, promptly after receipt of such comments comments, and any written or other communicationsoral responses thereto, and the Company will have the right to consult with Parent, Merger Sub and their counsel prior to responding to any such comments, either in written or oral form. (c) Each certificate for Shares issued Subject to Acquisition Sub representing Shares accepted for purchase the terms and paid for by Acquisition Sub conditions of this Agreement, unless extended in accordance with the terms of this Agreement, the Offer shall bear a legend expire at 12:00 midnight Eastern Time on the twentieth (20th) business day (calculated in substantially accordance with Rule 14d-1(g)(3) and 14d-2 under the Exchange Act) following form: THE SECURITIES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO RESTRICTIONS ON TRANSFER AS SET FORTH IN THE STOCKHOLDER AGREEMENTthe commencement of the Offer (the “Initial Expiration Date”) or, DATED SEPTEMBER 19if the Offer has been extended in accordance with this Agreement, 2001at the time and date to which the Offer has been so extended (the Initial Expiration Date, AMONG IMCLONE SYSTEMS INCORPORATEDor such later time and date to which the Offer has been extended in accordance with this Agreement, ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB COMPANY AND ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB BIOLOGICS COMPANYthe “Expiration Date”). (d) Parent will provide, A COPY OF WHICH MAY BE OBTAINED FROM THE CORPORATE SECRETARY OF IMCLONE SYSTEMS INCORPORATEDor cause to be provided, to Merger Sub promptly following the Acceptance Time, all funds necessary to pay the aggregate Offer Price with respect to Shares that have been validly tendered and not withdrawn in accordance with the Offer and that Merger Sub is obligated to accept for payment in accordance with the Offer and permitted to accept for payment in accordance with Law.

The Offer. (a) As Provided that nothing shall have occurred that, had the Offer referred to below been commenced, would give rise to a right to terminate the Offer pursuant to any of the conditions set forth in Annex A hereto, subject to the last sentence of this Section 1.1(a), as promptly as practicable after the date hereof, (but in no any event not later than ten Business Days after March 6, 2000), Parent will cause Purchaser to commence (within the date hereofmeaning of Rule 14d-2 under the Securities Exchange Act of 1934, Acquisition Sub shall commence an offer as amended (the "OFFERExchange Act") )), the Offer, whereby Purchaser will offer to purchase for cash 14,392,003 Shares (which shall include, for purposes of this Agreement, (i) all Shares issuable in respect of exercisable, in-the-money Company Options which have been "conditionally exercised" by the holder thereof for purposes of participating in the Offer, and (ii) all Shares issued prior to the expiration of the Offer upon Shares at the conversion of any convertible securities or upon the exercise of any options or warrants) (such number of Shares, the "MAXIMUM NUMBER") at a price of $70.00 per SharePer Share Amount, net to the seller in cash cash, without interest (subject to reduction for any stock transfer taxes payable by the seller, if payment is to be made to a Person other than the Person in whose name the certificate for such priceShares is registered, or for any applicable withholding tax), provided, however, that Parent may designate another direct or indirect subsidiary of Parent as the bidder in the Offer (within the meaning of Rule 14d-1(g) under the Exchange Act, in which case references herein to Purchaser will be deemed to apply to such subsidiary, as may hereafter be increased, the "OFFER PRICE"applicable). The obligation of Acquisition Sub Parent to cause Purchaser to consummate the Offer and to accept for payment any and to promptly pay for Shares validly tendered pursuant to in the Offer shall and not validly withdrawn in accordance therewith will be subject to, and only to the to, those conditions set forth in Annex I hereto. The initial expiration date A hereto (the "Offer Conditions"). (b) Subject to the requirements of the Offer shall be the twentieth Business Day following the commencement of the Offer (determined under Rule 14d-1(g)(3) promulgated under the 1934 Act). Acquisition Sub applicable Law, Purchaser expressly reserves the right to waive any of the conditions to the Offer, modify Offer and to make any changes in the terms or conditions of the Offer; provided, and increase the Offer Price; PROVIDED that, without the consent of the Company, Acquisition Sub shall not (i) increase or reduce the Maximum Number, (ii) reduce the price per Share to be paid pursuant to the Offer, (iii) add to the conditions set forth in Annex I or modify any condition set forth in Annex I, (iv) change the form of consideration payable in the Offer, or (v) otherwise amend the Offer in any manner adverse to the holders of Shares. Acquisition Sub shall extend the Offer for any period required by any rule, regulation, interpretation or position of the SEC or the staff thereof applicable to the Offer or any period required by applicable law. If any of the conditions to the Offer is not satisfied or waived on any scheduled expiration date of the Offer, Acquisition Sub shall extend the Offer from time to time until such conditions are satisfied or waived; PROVIDED however that (i) each such extension of the Offer shall be for a period of not more than ten Business Days, and (ii) Acquisition Sub shall not, without the prior written consent of the Company, Purchaser will not, and Parent will cause Purchaser not to, (i) decrease or change the form of the Per Share Amount, (ii) decrease the number of Shares sought in the Offer, or (iii) amend or waive the Minimum Condition (as defined in Annex A hereto) or impose conditions other than the Offer Conditions on the Offer. In the event that any Offer Condition is not satisfied or waived at the time that the expiration date of the Offer (as such date may from time to time be extended, the "Expiration Date") would otherwise occur, Purchaser may from time to time extend the Offer Expiration Date (but not beyond the Termination Outside Date. Subject ), or amend any term of the Offer in any manner not materially adverse to the foregoing Stockholders. In the event that at least a majority but less than 90% of the Voting Securities, calculated on a fully diluted basis, have been validly tendered and upon not withdrawn on the terms and subject to the conditions scheduled or extended expiration date of the Offer, Acquisition Sub shall Purchaser shall, unless otherwise notified by the Company in writing, accept and purchase all of the Shares tendered in the initial offer period and may notify Stockholders of Purchaser's intent to provide a "subsequent offering period" for tender of at least 90% of the Shares pursuant to Rule 14d-11 of the Exchange Act. The Offer may be extended in connection with an increase in the consideration to be paid pursuant to the Offer so as to comply with applicable rules and regulations of the Securities and Exchange Commission (the "SEC"). Assuming the prior satisfaction or waiver of the Offer Conditions, Parent will cause Purchaser to accept for payment payment, and pay for, as promptly as practicable after in accordance with the expiration terms of the Offer, all Shares validly tendered and not withdrawn (including if no Shares are validly tendered and not withdrawn), but not in excess of pursuant to the Maximum Number. (b) As Offer as soon as practicable on after the date of commencement of the Offer, BMS and Acquisition Sub shall file with the SEC a Tender Offer Statement on Schedule TO (the "SCHEDULE TO") with respect to the Offer (such Schedule TO and such documents included therein pursuant to which the Offer will be made, together with Expiration Date or any supplements or amendments thereto, the "OFFER DOCUMENTS"). BMS, Acquisition Sub and the Company each agrees promptly to correct any information provided by it for use in the Offer Documents if and to the extent that such information shall have become false or misleading in any material respect. BMS and Acquisition Sub agree to take all steps necessary to cause the Schedule TO as so corrected to be filed with the SEC. BMS and Acquisition Sub shall deliver or cause to be delivered to the Company, or such other Person as the Company shall designate, the Offer Documents (and any amendments thereto) as so corrected, in such quantities as shall be necessary for dissemination to all holders of Shares and Company Options. The Company shall, at its expense, cause the Offer Documents (and any amendments thereto) to be disseminated to holders of Shares and Company Options, in each case as and to the extent required by applicable federal securities laws. The Company and its counsel shall be given an opportunity to review and comment on the Offer Documents prior to their being filed with the SEC or disseminated to the holders of Shares and Company Options. BMS and Acquisition Sub shall provide the Company and its counsel with any comments or other communications, whether written or oral, that BMS, Acquisition Sub or its counsel may receive from time to time from the SEC or its staff with respect to the Offer Documents promptly after receipt of such comments or other communicationsextension thereof. (c) Each certificate for Shares issued to Acquisition Sub representing Shares accepted for purchase and paid for by Acquisition Sub in the Offer shall bear a legend in substantially the following form: THE SECURITIES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO RESTRICTIONS ON TRANSFER AS SET FORTH IN THE STOCKHOLDER AGREEMENT, DATED SEPTEMBER 19, 2001, AMONG IMCLONE SYSTEMS INCORPORATED, ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB COMPANY AND ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB BIOLOGICS COMPANY, A COPY OF WHICH MAY BE OBTAINED FROM THE CORPORATE SECRETARY OF IMCLONE SYSTEMS INCORPORATED.

The Offer. (a) As Provided that this Agreement shall not have previously been validly terminated in accordance with Section 10.01 and that none of the events set forth in Paragraph (2) (excluding Paragraph (2)(c)) of Annex I hereto shall exist or have occurred and be continuing, as promptly as practicable after the date hereof, but in no any event later than within ten Business Days (10) business days after the date hereof, Acquisition Sub shall commence an offer (the "OFFER") to purchase for cash 14,392,003 Shares (which shall include, for purposes of this Agreement, Parent shall cause Purchaser to, and Purchaser shall, commence (within the meaning of Rule 14d−2 under the Exchange Act) the Offer for all of the outstanding Company Common Shares (other than Company Common Shares described in Section 4.01(a)) for a price per Company Common Share equal to the Offer Price (as adjusted as provided in Section 2.01(f)). The date on which Purchaser commences the Offer, within the meaning of Rule 14d−2 under the Exchange Act, is referred to in this Agreement as the “Offer Commencement Date”. (b) As promptly as practicable on the later of: (i) all the earliest date as of which Purchaser is permitted under applicable Law to accept for payment Company Common Shares issuable in respect of exercisable, in-the-money Company Options which have been "conditionally exercised" by tendered pursuant to the holder thereof for purposes of participating in the Offer, Offer and (ii) the earliest date as of which each of the conditions set forth in Annex I (the “Offer Conditions”) shall have been satisfied or waived, Purchaser shall (and Parent shall cause Purchaser to) accept for payment all Company Common Shares issued prior tendered pursuant to the expiration of the Offer upon the conversion of any convertible securities or upon the exercise of any options or warrants) (such number of Shares, the "MAXIMUM NUMBER") at a price of $70.00 per Share, net to the seller in cash (such price, as may hereafter be increased, the "OFFER PRICE"and not validly withdrawn). The obligation of Acquisition Sub Purchaser to accept for payment any Company Common Shares tendered pursuant to the Offer shall be subject only to the conditions set forth in Annex I hereto. The initial expiration date satisfaction or waiver of each of the Offer Conditions (and shall not be subject to any other conditions). As promptly as practicable after the twentieth Business Day following the commencement acceptance for payment of any Company Common Shares validly tendered pursuant to the Offer (determined under Rule 14d-1(g)(3and not properly withdrawn), Purchaser shall pay for such Company Common Shares. (c) promulgated under Parent and Purchaser expressly reserve the 1934 Act). Acquisition Sub expressly reserves right to increase the Offer Price, and subject to the immediately succeeding sentence, reserve the right to waive any of the conditions Offer Conditions and to the Offer, modify make any change in the terms of the Offer. Notwithstanding anything to the contrary contained in this Agreement, and increase the Offer Price; PROVIDED that, neither Parent nor Purchaser shall (without the prior written consent of the Company, Acquisition Sub shall not ): (i) increase change or reduce waive the Maximum Number, Minimum Condition (as defined in Annex I); (ii) reduce decrease the price per Share number of Company Common Shares sought to be paid pursuant to purchased by Purchaser in the Offer, ; (iii) add reduce the Offer Price; (iv) extend or otherwise change the expiration date of the Offer (except to the conditions set forth in Annex I extent required or modify any condition set forth in Annex I, permitted pursuant to Section 2.01(d)); (ivv) change the form of consideration payable in the Offer; or (vi) amend, modify or (v) otherwise amend supplement any of the Offer Conditions or terms of the Offer in any a manner adverse that adversely affects, or would reasonably be expected to adversely affect, the holders of Company Common Shares. (d) Unless extended as provided in this Agreement, the Offer shall expire on the date (the “Initial Expiration Date”) that is twenty (20) business days (calculated as set forth in Rule 14d-1(g)(3) under the Exchange Act) after the Offer Commencement Date. Acquisition Sub Notwithstanding the foregoing, (i) Purchaser shall extend the Offer for any period required by any rule, regulation, interpretation or position of the SEC or the its staff thereof or Nasdaq that is applicable to the Offer; provided, that in no event shall Purchaser be required to extend the Offer beyond the Outside Date, (ii) if, on the Initial Expiration Date or any period required by applicable law. If any subsequent date as of the conditions to which the Offer is scheduled to expire, any Offer Condition is not satisfied or waived on any scheduled expiration date and has not been waived, then, (A) Purchaser may in its discretion, without the consent of the OfferCompany and (B) Purchaser shall to the extent such Offer Condition could reasonably be satisfied and such extension is requested in writing by the Company no less than two (2) business days prior to the applicable expiration date, Acquisition Sub shall extend the Offer from time for one or more periods ending no later than the Outside Date to time until permit such conditions are satisfied or waivedOffer Condition to be satisfied; PROVIDED provided, however, that (i) each such no individual extension of the Offer shall be for a period of not more than ten Business Days, (10) business days; and (iiiii) Acquisition Sub Purchaser may, in its discretion, elect to provide for a subsequent offering period (and one or more extensions thereof) in accordance with Rule 14d-11 under the Exchange Act following the Acceptance Time, and, if immediately following the Acceptance Time (as defined in Section 2.04(a)), Parent, Purchaser and their respective subsidiaries and Affiliates own more than 80% but less than 90% of the Company Common Shares outstanding at that time (which shares beneficially owned shall notinclude shares tendered in the Offer and not withdrawn), without to the prior written consent of extent requested by the Company, extend the Offer beyond the Termination DatePurchaser shall provide for a subsequent offering period of at least ten (10) business days. Subject to the foregoing and upon the terms and subject to the conditions of set forth in this Agreement and the Offer, Acquisition Sub Parent shall cause Purchaser to, and Purchaser shall, accept for payment and pay for, as promptly as practicable after the expiration of the Offer, for all Company Common Shares validly tendered and not withdrawn (including if no during such subsequent offering period as promptly as practicable after any such Company Common Shares are validly tendered during such subsequent offering period and not withdrawnin any event in compliance with Rule 14d-11(c) promulgated under the Exchange Act. (e) The Offer may be terminated prior to its expiration date (as such expiration date may be extended and re-extended in accordance with this Agreement), but not only if this Agreement is validly terminated in excess of the Maximum Numberaccordance with Section 10.01. (bf) As soon as practicable The Offer Price shall be adjusted to the extent appropriate to reflect the effect of any stock split, division or subdivision of shares, stock dividend, reverse stock split, consolidation of shares, reclassification, recapitalization or other similar transaction with respect to Company Common Shares occurring or having a record date on or after the date of commencement of the Offer, BMS this Agreement and Acquisition Sub shall file with the SEC a Tender Offer Statement on Schedule TO (the "SCHEDULE TO") with respect prior to the Offer (such Schedule TO and such documents included therein pursuant to which the Offer will be made, together with any supplements or amendments thereto, the "OFFER DOCUMENTS"). BMS, Acquisition Sub and payment by Purchaser for the Company each agrees promptly to correct any information provided by it for use in the Offer Documents if and to the extent that such information shall have become false or misleading in any material respect. BMS and Acquisition Sub agree to take all steps necessary to cause the Schedule TO as so corrected to be filed with the SEC. BMS and Acquisition Sub shall deliver or cause to be delivered to the Company, or such other Person as the Company shall designate, the Offer Documents (and any amendments thereto) as so corrected, in such quantities as shall be necessary for dissemination to all holders of Shares and Company Options. The Company shall, at its expense, cause the Offer Documents (and any amendments thereto) to be disseminated to holders of Shares and Company Options, in each case as and to the extent required by applicable federal securities laws. The Company and its counsel shall be given an opportunity to review and comment on the Offer Documents prior to their being filed with the SEC or disseminated to the holders of Shares and Company Options. BMS and Acquisition Sub shall provide the Company and its counsel with any comments or other communications, whether written or oral, that BMS, Acquisition Sub or its counsel may receive from time to time from the SEC or its staff with respect to the Offer Documents promptly after receipt of such comments or other communicationsCommon Shares. (c) Each certificate for Shares issued to Acquisition Sub representing Shares accepted for purchase and paid for by Acquisition Sub in the Offer shall bear a legend in substantially the following form: THE SECURITIES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO RESTRICTIONS ON TRANSFER AS SET FORTH IN THE STOCKHOLDER AGREEMENT, DATED SEPTEMBER 19, 2001, AMONG IMCLONE SYSTEMS INCORPORATED, ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB COMPANY AND ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB BIOLOGICS COMPANY, A COPY OF WHICH MAY BE OBTAINED FROM THE CORPORATE SECRETARY OF IMCLONE SYSTEMS INCORPORATED.

The Offer. (a) As Subject to the terms and conditions set forth in this Agreement, as promptly as reasonably practicable after the date hereofof this Agreement, but in no event later than ten (10) Business Days after the date hereof, Acquisition Sub shall commence an offer (the "OFFER") to purchase for cash 14,392,003 Shares (which shall include, for purposes of this Agreement, Merger Sub shall (iand Parent shall cause Merger Sub to) all Shares issuable in respect commence (within the meaning of exercisable, in-the-money Company Options which have been "conditionally exercised" by Rule 14d-2 under the holder thereof for purposes of participating in the Offer, and (iiExchange Act) all Shares issued prior to the expiration of the Offer upon the conversion of to purchase any convertible securities or upon the exercise of any options or warrants) (such number of Shares, the "MAXIMUM NUMBER") and all outstanding Shares at a price of $70.00 per Share, net Share equal to the seller in cash (such price, as may hereafter be increased, the "OFFER PRICE")Offer Price. The obligation obligations of Acquisition Merger Sub to, and of Parent to cause Merger Sub to, purchase, accept for payment any payment, and pay for, Shares tendered pursuant to the Offer shall be are subject only to the satisfaction or waiver of each of the conditions set forth in Annex I hereto. A (the “Offer Conditions”). (b) The initial expiration date of the Offer shall be the twentieth (20th) Business Day following the commencement of the Offer (determined under Rule using Exchange Act Rules 14d-1(g)(3) promulgated under and 14d-2) (such date being the 1934 Actinitial “Expiration Date,” and any expiration time and date established pursuant to an authorized extension of the Offer as so extended, also an “Expiration Date”). Acquisition Sub expressly reserves Notwithstanding the right to waive foregoing, if, on the initial Expiration Date or any subsequent Expiration Date, all of the conditions to Offer Conditions have not been satisfied or waived (other than any Offer Conditions that by their nature cannot be satisfied until the Offer, modify the terms closing of the Offer, which shall be required to be satisfied or waived at the closing of the Offer), then Merger Sub shall, and increase Parent shall cause Merger Sub to, subject to the rights of the parties under Article 8, extend (and re-extend) the Offer Priceand its Expiration Date beyond the initial Expiration Date or such subsequent Expiration Date until the date all of the Offer Conditions are satisfied or waived (other than any Offer Conditions that by their nature cannot be satisfied until the closing of the Offer, which shall be required to be satisfied or waived at the closing of the Offer); PROVIDED thatprovided that any such extension (i) shall be in increments determined by Merger Sub of not more than ten (10) Business Days and (ii) shall not extend beyond the Walk Away Date. The Offer may not be terminated prior to its Expiration Date (as such Expiration Date may be extended and re-extended in accordance with this Agreement), unless this Agreement is validly terminated in accordance with Article 8. In no event shall Merger Sub extend the Offer beyond the date that is five (5) Business Days prior to the Walk Away Date without the prior written consent of the CompanyCompany in its sole discretion. Notwithstanding the foregoing, Acquisition Sub shall not (i) increase or reduce the Maximum Number, (ii) reduce the price per Share to be paid pursuant subject to the Offerrights of the parties under Article 8, (iii) add to the conditions set forth in Annex I or modify any condition set forth in Annex I, (iv) change the form of consideration payable in the Offer, or (v) otherwise amend the Offer in any manner adverse to the holders of Shares. Acquisition Merger Sub shall extend the Offer Offer, and Parent shall cause Merger Sub to extend the Offer, for any period required by any rule, regulation, interpretation or position of the SEC or the staff thereof applicable to the Offer or any period required by any other Law. (c) Parent shall provide or cause to be provided to Merger Sub on a timely basis the funds necessary to purchase any Shares that Merger Sub becomes obligated to purchase pursuant to the Offer. Merger Sub shall, and Parent shall cause Merger Sub to, comply with the obligations respecting prompt payment and announcement under the Exchange Act, and, without limiting the foregoing, Merger Sub shall (and Parent shall cause Merger Sub to) accept for payment and pay for all Shares validly tendered and not properly withdrawn pursuant to the Offer as promptly as practicable following the later of: (i) the earliest date as of which Merger Sub is permitted under applicable law. If Law to accept for payment Shares tendered pursuant to the Offer and (ii) the earliest date as of which each of the Offer Conditions shall have been satisfied or waived. (d) Merger Sub may, in its sole discretion (and without any required consent of the Company, but subject to the terms set forth in this Section 1.1(d)), elect to provide for a subsequent offering period (and one or more extensions thereof) in accordance with Rule 14d-11 under the Exchange Act (each a “Subsequent Offering Period”) following the Acceptance Time if (i) Merger Sub shall have complied with all of the conditions of Rule 14d-11 under the Exchange Act and (ii) at the commencement of any Subsequent Offering Period (or extension thereof) the number of Shares owned by Parent, Merger Sub and their respective Subsidiaries (including any Shares beneficially owned by any of the conditions to foregoing and including all Shares validly tendered and not properly withdrawn at the Offer is not satisfied or waived on any scheduled expiration date Acceptance Time) represent less than 90% of the Offerthen outstanding number of Shares; provided, Acquisition however, that if Merger Sub is required to exercise the Top-Up Option pursuant to Section 1.4(c), Merger Sub shall extend not be permitted to provide for a Subsequent Offering Period. If immediately following the Offer from Acceptance Time, Parent, Merger Sub and their respective Subsidiaries own more than 70% but less than 90% of the Shares outstanding at that time to time until such conditions are satisfied or waived; PROVIDED that (which shall include (i) each such extension shares beneficially owned by Parent, Merger Sub and their respective Subsidiaries, which Shares shall be converted into direct ownership at or prior to the expiration of the Offer shall be for a period of not more than ten Business Daysby Parent, Merger Sub or their respective Subsidiaries, as the case may be, and (ii) Acquisition shares validly tendered in the Offer and not properly withdrawn at the Acceptance Time), to the extent requested by the Company, Merger Sub shall notprovide for, and Parent shall cause Merger Sub to provide for, a Subsequent Offering Period of ten (10) Business Days; provided, however, that if Merger Sub is required to exercise the Top-Up Option pursuant to Section 1.4(c), the Company shall not have the right to request a Subsequent Offering Period; provided, further that the Company shall not have the right to request a Subsequent Offering Period if such Subsequent Offering Period would extend beyond the date that is five (5) Business Days prior to the Walk Away Date without the prior written consent of Parent (which consent may be withheld in its sole discretion). Subject to the terms and conditions set forth in this Agreement and the Offer, Parent shall cause Merger Sub to, and Merger Sub shall, accept for payment and pay for all Shares validly tendered and not properly withdrawn during such Subsequent Offering Period as promptly as practicable after any such Shares are tendered during any Subsequent Offering Period and in any event in compliance with Rule 14d-11(c) promulgated under the Exchange Act. (e) Parent and Merger Sub expressly reserve the right to waive any of the Offer Conditions, to increase the Offer Price and/or to modify the other terms of the Offer, except that, without the prior written consent of the Company, extend Merger Sub shall not, and Parent shall not permit Merger Sub to, do any of the Offer beyond following: (i) reduce the Termination Date. Subject to the foregoing and upon the terms and number of Shares subject to the conditions Offer; (ii) reduce the Offer Price; (iii) amend, change or waive the Minimum Tender Condition; (iv) except as expressly provided in Section 1.1(b), extend or otherwise change the Expiration Date, except (A) as required by applicable Law (including for any period required by any rule, regulation, interpretation or position of the SEC or the staff thereof) or (B) in connection with an increase of the Offer Price; (v) change the form of consideration payable in the Offer; (vi) impose any condition to the Offer other than the Offer Conditions; or (vii) otherwise amend, modify or supplement any of the Offer Conditions or the terms of the Offer in any manner adverse to holders of Shares or that would, individually or in the aggregate, reasonably be expected to prevent or materially delay the consummation of the Offer or prevent, materially delay or impair the ability of the Parent or Merger Sub to consummate the Offer, Acquisition Sub shall accept for payment and pay for, as promptly as practicable after the expiration of Merger or the Offer, all Shares validly tendered and not withdrawn (including if no Shares are validly tendered and not withdrawn), but not in excess of the Maximum Numberother Transactions. (bf) As soon as practicable on On the date of commencement of the Offer, BMS Parent and Acquisition Merger Sub shall file with the SEC a Tender Offer Statement on Schedule TO (the "SCHEDULE TO") with respect to the Offer, which Tender Offer Statement shall (i) contain or incorporate by reference an offer to purchase and a related letter of transmittal and summary advertisement and such other information or documents as required by Law (such Schedule TO and such the documents included therein pursuant to which the Offer will be made, together with any supplements or amendments thereto, being referred to as the "OFFER DOCUMENTS")“Offer Documents”) and (ii) be in form reasonably satisfactory to the Company. BMSThe Company shall as promptly as practicable upon request of Parent, Acquisition provide Parent and Merger Sub with all information concerning the Company that is required to be included in the Offer Documents. Parent and Merger Sub shall cause the Offer Documents to comply in all material respects with the requirements of applicable U.S. federal securities Laws and, on the date first filed with the SEC and on the date first published, sent or given to the holders of Shares, not to contain any untrue statement of a material fact or omit to state any material fact required to be stated therein or necessary in order to make the statements therein, in light of the circumstances under which they were made, not misleading, except that no covenant is made by Parent or Merger Sub with respect to information supplied by the Company in writing specifically for inclusion or incorporation by reference in the Offer Documents. Each of Parent, Merger Sub and the Company each agrees shall promptly to correct any information provided by it for use in the Offer Documents if and to the extent necessary such that such information shall have become false the Offer Documents do not contain an untrue statement of a material fact or misleading in omit to state any material respectfact required to be stated therein or necessary in order to make the statements therein, in light of the circumstances under which they are made, not misleading. BMS Each of Parent and Acquisition Merger Sub agree to shall take all steps necessary to amend or supplement the Offer Documents and to cause the Schedule TO Offer Documents as so corrected amended or supplemented to be filed with the SEC. BMS SEC and Acquisition Sub shall deliver or cause to be delivered disseminated to the Company, or such other Person as the Company shall designate, the Offer Documents (and any amendments thereto) as so corrected, in such quantities as shall be necessary for dissemination to all holders of Shares and Company Options. The Company shall, at its expense, cause the Offer Documents (and any amendments thereto) to be disseminated to holders of Shares and Company OptionsShares, in each case as and to the extent required by applicable U.S. federal securities lawsLaws. The Company and its counsel shall be given an afforded a reasonable opportunity to review and comment on upon the Offer Documents prior to their being each time before they are filed with the SEC or and/or disseminated to the holders of Shares (and Company Options. BMS and Acquisition Sub shall provide the Company and its counsel with shall provide any comments thereon as soon as reasonably practicable, and Parent and Merger Sub shall give reasonable and good faith consideration to any comments made by the Company and its counsel). Parent and Merger Sub shall provide to the Company and its counsel copies of any written comments or telephonic notification of any oral comments or other communicationscommunications Parent, whether written or oral, that BMS, Acquisition Merger Sub or its their counsel may receive from time to time from the SEC or its staff with respect to the Offer Documents promptly after the receipt of such comments or other communications, shall consult with the Company and its counsel prior to responding to any such comments or other communications, and shall provide the Company with copies of all written responses and telephonic notification of any oral responses thereto of Parent or Merger Sub or their counsel, provided that Parent and Merger Sub shall provide the Company and its counsel a reasonable opportunity to participate in the response of Parent and Merger Sub to any such comments or other communications and to provide comments on that response (to which reasonable and good faith consideration shall be given by Parent and Merger Sub). (cg) Each certificate for Shares issued Unless this Agreement is terminated pursuant to Acquisition Section 8.1, neither Parent nor Merger Sub representing Shares accepted for purchase and paid for by Acquisition Sub shall terminate or withdraw the Offer without the prior written consent of the Company in its sole discretion, except that in the event this Agreement is terminated pursuant to Section 8.1, Merger Sub shall promptly (and in any event within one (1) Business Day) following such termination irrevocably and unconditionally terminate the Offer and shall bear not acquire any Shares pursuant thereto. If the Offer is terminated in accordance with this Agreement prior to the purchase of Shares in the Offer, Merger Sub shall promptly return, or cause any depositary acting on behalf of Merger Sub to return, all tendered Shares to the tendering stockholders. (h) The Offer Price shall be adjusted to reflect fully the effect of any reclassification, stock split, reverse split, stock dividend (including any dividend or distribution of securities convertible into Company Common Stock), reorganization, recapitalization or other like change with respect to Company Common Stock effected by the Company in accordance with the terms and conditions of this Agreement and occurring (or for which a legend record date is established) after the date of this Agreement and prior to the payment by Merger Sub for the Shares validly tendered and not properly withdrawn in substantially connection with the following form: THE SECURITIES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO RESTRICTIONS ON TRANSFER AS SET FORTH IN THE STOCKHOLDER AGREEMENT, DATED SEPTEMBER 19, 2001, AMONG IMCLONE SYSTEMS INCORPORATED, ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB COMPANY AND ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB BIOLOGICS COMPANY, A COPY OF WHICH MAY BE OBTAINED FROM THE CORPORATE SECRETARY OF IMCLONE SYSTEMS INCORPORATEDOffer.

The Offer. Section 1.1 The Offer. (a) As promptly as practicable after Provided that (i) this Agreement shall not have been terminated in accordance with Section 10.1 and (ii) none of the date hereofevents set forth in Annex I hereto shall have occurred or be existing and not have been waived, but in no event Merger Subsidiary shall, not later than ten Business Days after five business days from the date hereof, Acquisition Sub shall commence an offer (first public announcement of the "OFFER") to purchase for cash 14,392,003 Shares (which shall include, for purposes execution of this Agreement, (i) all Shares issuable in respect of exercisable, in-the-money Company Options which have been "conditionally exercised" by the holder thereof for purposes of participating in commence the Offer, and . Each Share (iiincluding the associated Right) all Shares issued prior to the expiration of accepted by Merger Subsidiary in accordance with the Offer upon the conversion of any convertible securities or upon the exercise of any options or warrants) (such number of Shares, the "MAXIMUM NUMBER") at a price of shall be purchased for $70.00 per Share1.80, net to the seller in cash (such pricecash, as may hereafter be increased, the "OFFER PRICE")without interest. The obligation of Acquisition Sub to accept for payment any Shares tendered pursuant to the Offer shall be subject only to the conditions (i) that there shall be validly tendered in accordance with the terms of the Offer prior to the expiration date of the Offer and not withdrawn a number of Shares which, together with the Shares then owned by Parent and Merger Subsidiary, represents at least two-thirds of the total number of outstanding Shares, assuming the exercise of all outstanding warrants, options, rights and convertible securities (if any) (other than the Rights, Parent's option to acquire Company Common Stock pursuant to the Stock Option Agreement, to the extent not then exercised and options cancelled pursuant to Section 3.4(a) hereof) and the issuance of all Shares that the Company is obligated to issue pursuant thereto (such total number of outstanding Shares being hereinafter referred to as the "Fully Diluted Shares") (the "Minimum Stock Condition"), (ii) that Parent shall have simultaneously accepted for payment Notes in each of the Notes Tender Offers, and (iii) that the other conditions set forth in Annex I heretohereto shall have been satisfied or waived. The initial expiration date of the Offer shall be the twentieth Business Day following the commencement of the Offer (determined under Rule 14d-1(g)(3) promulgated under the 1934 Act). Acquisition Sub Parent and Merger Subsidiary expressly reserves reserve the right to waive any of the conditions to the Offer, modify Offer and to make any change in the terms or conditions of the Offer, and increase the Offer Price; PROVIDED provided that, without the written consent of the Company, Acquisition Sub shall not (i) increase no change may be made which changes the form or reduce the Maximum Number, (ii) reduce the price per Share amount of consideration to be paid pursuant (other than by adding consideration), imposes conditions to the Offer, (iii) add Offer in addition to the conditions those set forth in Annex I or modify changes or waives the Minimum Stock Condition or amends any condition set forth in Annex I, (iv) change the form other term of consideration payable in the Offer, or (v) otherwise amend the Offer in any a manner materially adverse to the holders of Shares. Acquisition Sub shall extend If on the Offer for any period required by any rule, regulation, interpretation or position of the SEC or the staff thereof applicable to the Offer or any period required by applicable law. If any of the conditions to the Offer is not satisfied or waived on any initial scheduled expiration date of the Offer, Acquisition Sub which shall extend be no earlier than 20 business days after the date the Offer is commenced, all conditions to the Offer shall not have been satisfied or waived, Merger Subsidiary may, from time to time until such conditions are satisfied or waivedtime, in its sole discretion, extend the expiration date; PROVIDED provided that (i) each such extension of the Offer shall be for a period of not more than ten Business Days, and (ii) Acquisition Sub shall not, without the prior written consent of the Company, Merger Subsidiary may not extend the Offer beyond December 28, 2001 (except that Parent may extend the Termination Dateexpiration date of the Offer after December 28, 2001 as required to comply with any rule, regulation or interpretation of the SEC). Subject to the foregoing and upon the terms and subject to the conditions of the Offer, Acquisition Sub Parent shall cause Merger Subsidiary to accept for payment and pay for, as promptly as practicable after the expiration of the Offer, all Shares validly tendered and not withdrawn pursuant to the Offer. In addition, Merger Subsidiary may extend the Offer after the acceptance of Shares thereunder for a further period of time by means of a subsequent offering period under Rule 14d-11 promulgated under the Securities Exchange Act of 1934, as amended (including if no Shares are the "Exchange Act"), of not more than 20 business days to meet the objective (which is not a condition to the Offer) that there be validly tendered tendered, in accordance with the terms of the Offer, prior to the expiration date of the Offer (as so extended) and not withdrawn)withdrawn a number of Shares, but not in excess which together with Shares then owned by Parent and Merger Subsidiary, represents at least 90% of the Maximum NumberFully Diluted Shares. (b) As soon as practicable on after the date of commencement this Agreement, and not later than five business days from the first public announcement of the Offerexecution of this Agreement, BMS Parent shall, and Acquisition Sub Parent shall cause Merger Subsidiary to, file with the SEC Securities and Exchange Commission (the "SEC") a Tender Offer Statement on Schedule TO (the "SCHEDULE TO") together with respect to the Offer (such Schedule TO any amendments or supplements thereto and such documents included therein any other filings pursuant to which the Offer will be made, together with any supplements or amendments thereto, the "OFFER DOCUMENTSOffer Documents"). BMSParent, Acquisition Sub Merger Subsidiary and the Company each agrees agree promptly to correct any information provided by it for use in the Offer Documents if and to the extent that such information it shall have become false or misleading in any material respect. BMS Parent and Acquisition Sub Merger Subsidiary agree to take all steps necessary to cause the Schedule TO Offer Documents as so corrected to be filed with the SEC. BMS SEC and Acquisition Sub shall deliver or cause to be delivered to the Company, or such other Person as the Company shall designate, the Offer Documents (and any amendments thereto) as so corrected, in such quantities as shall be necessary for dissemination to all holders of Shares and Company Options. The Company shall, at its expense, cause the Offer Documents (and any amendments thereto) to be disseminated to holders of Shares and Company OptionsShares, in each case as and to the extent required by applicable federal Federal securities laws. The Company and its counsel shall be given an a reasonable opportunity to review and comment on the Offer Documents prior to their being filed with the SEC or disseminated SEC. In addition, Parent and Merger Subsidiary agree to the holders of Shares and Company Options. BMS and Acquisition Sub shall provide the Company and its counsel with any comments or other communicationscomments, whether written or oral, that BMS, Acquisition Sub Parent or its Merger Subsidiary or their counsel may receive from time to time from the SEC or its staff with respect to the Offer Documents promptly after the receipt of such comments or other communications. (c) Each certificate for Shares issued to Acquisition Sub representing Shares accepted for purchase and paid for by Acquisition Sub in the Offer shall bear a legend in substantially the following form: THE SECURITIES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO RESTRICTIONS ON TRANSFER AS SET FORTH IN THE STOCKHOLDER AGREEMENT, DATED SEPTEMBER 19, 2001, AMONG IMCLONE SYSTEMS INCORPORATED, ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB COMPANY AND ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB BIOLOGICS COMPANY, A COPY OF WHICH MAY BE OBTAINED FROM THE CORPORATE SECRETARY OF IMCLONE SYSTEMS INCORPORATED.

The Offer. (a) As promptly as practicable after the date hereof, (but in no event later than ten Business Days five business days after the date hereof, Acquisition Sub shall commence an offer (of the "OFFER") to purchase for cash 14,392,003 Shares (which shall include, for purposes initial public announcement of the execution and delivery of this Agreement), Newco shall, and Parent shall cause Newco to, commence (i) all Shares issuable in respect within the meaning of exercisableRule 14d-2 under the United States Securities Exchange Act of 1934, in-the-money Company Options which have been as amended (collectively with the rules and regulations promulgated thereunder, the "conditionally exercised" by Exchange Act")), the holder thereof for purposes Offer and, subject to the conditions of participating in the Offer, and (ii) all Shares issued prior shall use commercially reasonable efforts to the expiration of consummate the Offer upon the conversion of any convertible securities or upon the exercise of any options or warrants) (such number of Shares, the "MAXIMUM NUMBER") at a price of $70.00 per Share, net to the seller in cash (such price, as may hereafter be increased, the "OFFER PRICE")promptly as permitted by law. The obligation of Acquisition Sub Parent and Newco to consummate the Offer, to accept for payment and to pay for any Shares tendered pursuant to the Offer (i) shall be subject only to the condition that the number of Shares validly tendered and not withdrawn prior to the expiration date of the Offer (the "Expiration Date"), together with all Shares beneficially owned by Parent or any of its subsidiaries on such date (the "Parent Owned Shares"), shall be not less than 75% of the Shares then outstanding, calculated on a fully diluted basis (the "Minimum Condition"), and (ii) shall be subject to the other conditions set forth in Annex I hereto. The initial expiration date of the Offer shall be the twentieth Business Day following the commencement of the Offer A. (determined under Rule 14d-1(g)(3b) promulgated under the 1934 Act). Acquisition Sub Parent and Newco expressly reserves reserve the right to waive increase the price per Share payable in the Offer or to make any other changes in the terms and conditions of the Offer; provided, however, that neither Parent nor Newco will, without the prior written consent of Company, decrease the consideration payable in the Offer, reduce the number of Shares subject to the Offer, impose any additional conditions to the Offer, modify the terms of the Offer, and increase the Offer Price; PROVIDED that, without the consent of the Company, Acquisition Sub shall not (i) increase or reduce the Maximum Number, (ii) reduce the price per Share to be paid pursuant to the Offer, (iii) add to the conditions set forth in Annex I or modify any condition set forth in Annex I, (iv) change the form of consideration payable in the Offer, Offer or (v) otherwise amend or alter any other term of the Offer in any manner materially adverse to the holders of Shares. Acquisition Sub shall extend Company agrees that no Shares held by Company or any of its subsidiaries will be tendered pursuant to the Offer. Notwithstanding any other provision of this Agreement, the conditions of the Offer are for any period required the sole benefit of Parent and Newco and may be asserted by any rule, regulation, interpretation or position Parent and Newco regardless of the SEC circumstances giving rise to any such conditions or the staff thereof applicable to the Offer may be waived by Parent and Newco in whole at any time or any period required by applicable law. If any of the conditions to the Offer is not satisfied or waived on any scheduled expiration date of the Offer, Acquisition Sub shall extend the Offer in part from time to time until such conditions are satisfied or waived; PROVIDED that in their sole and absolute discretion (i) each such extension except that, without Company's consent, Newco may not reduce the percentage amount of the Offer shall be for a period of not more Minimum Condition to less than ten Business Days, and (ii) Acquisition Sub shall not, without the prior written consent of the Company, extend the Offer beyond the Termination Date. Subject to the foregoing and upon the terms and subject to the conditions of the Offer, Acquisition Sub shall accept for payment and pay for, as promptly as practicable after the expiration of the Offer, all Shares validly tendered and not withdrawn (including if no Shares are validly tendered and not withdrawnmajority), but not in excess of the Maximum Number. (bc) As soon as practicable on the date of commencement of the Offer, BMS Parent and Acquisition Sub Newco shall file with the SEC United States Securities and Exchange Commission (the "SEC") a Tender Offer Statement on Schedule TO (the "SCHEDULE TO") 14D-1 with respect to the Offer which will contain the offer to purchase and form of the related letter of transmittal (such Schedule TO and such documents included therein pursuant to which the Offer will be made, together with any supplements or amendments thereto, collectively referred to herein as the "OFFER DOCUMENTSOffer Documents"). BMS, Acquisition Sub Parent and the Company each agrees promptly to correct any information provided by it for use in the Offer Documents if and to the extent that such information Newco shall have become false or misleading in any material respect. BMS and Acquisition Sub agree to take all steps necessary to cause the Schedule TO as so corrected to be filed with the SEC. BMS and Acquisition Sub shall deliver or cause to be delivered to the Company, or such other Person as the Company shall designate, the Offer Documents (and any amendments thereto) as so corrected, in such quantities as shall be necessary for dissemination to all holders of Shares and Company Options. The Company shall, at its expense, cause the Offer Documents (and any amendments thereto) to be disseminated to holders of Shares and Company Options, in each case as and to the extent required by applicable federal securities laws. The give Company and its counsel shall be given an a reasonable opportunity to review and comment on the Offer Documents prior to their being filed with the SEC or disseminated to the holders shareholders of Shares Company. Parent and Company Options. BMS and Acquisition Sub shall provide the Newco will furnish Company and its counsel with in writing any comments that Parent, Newco or other communications, whether written or oral, that BMS, Acquisition Sub or its their counsel may receive from time to time from the SEC or its staff with respect to the Offer Documents Documents, promptly after receipt of such comments comments, and the proposed responses thereto. Each of Parent and Newco (and Company with respect to information supplied by it specifically for use in the Offer Documents) agrees to promptly correct the Offer Documents if and to the extent that they shall have become false or other communicationsmisleading in any material respect, and Parent and Newco shall take all steps reasonably necessary to cause the Offer Documents as so corrected to be filed with the SEC and to be disseminated to Company's shareholders, in each case as and to the extent required by applicable United States federal securities laws. (cd) Each certificate Parent shall provide or cause to be provided to Newco on a timely basis the funds sufficient to accept for payment, and Parent shall cause Newco to pay for, any and all Shares issued that Newco becomes obligated to Acquisition Sub representing Shares accepted accept for purchase and paid for by Acquisition Sub in payment pursuant to the Offer shall bear a legend in substantially the following form: THE SECURITIES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO RESTRICTIONS ON TRANSFER AS SET FORTH IN THE STOCKHOLDER AGREEMENT, DATED SEPTEMBER 19, 2001, AMONG IMCLONE SYSTEMS INCORPORATED, ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB COMPANY AND ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB BIOLOGICS COMPANY, A COPY OF WHICH MAY BE OBTAINED FROM THE CORPORATE SECRETARY OF IMCLONE SYSTEMS INCORPORATEDOffer.

The Offer. (a) As Provided that this Agreement shall not have been terminated in accordance with Section 7.1, as promptly as practicable (and in any event within ten (10) Business Days) after the date hereof, but in no event later than ten Business Days after Purchaser shall (and Parent shall cause Purchaser to) commence (within the date hereof, Acquisition Sub shall commence an offer (meaning of Rule 14d-2 under the "OFFER"Exchange Act) the Offer to purchase for cash 14,392,003 Shares (which shall include, for purposes of this Agreement, (i) all Shares issuable in respect of exercisable, in-the-money Company Options which have been "conditionally exercised" by the holder thereof for purposes of participating in the Offer, and (ii) all Shares issued prior to the expiration of the Offer upon the conversion of any convertible securities or upon the exercise of any options or warrants) (such number of Shares, the "MAXIMUM NUMBER") Shares at a price of $70.00 per Share, net share equal to the seller in cash Offer Price. (such price, as may hereafter be increased, the "OFFER PRICE"). b) The obligation of Acquisition Sub Purchaser to, and of Parent to cause Purchaser to, accept for payment and pay for any Shares validly tendered and not validly withdrawn pursuant to the Offer shall be subject only to the satisfaction, or waiver by Purchaser or Parent, of the conditions set forth in Annex I heretoA (the “Offer Conditions”). Subject to the satisfaction, or waiver by Purchaser or Parent, of the Offer Conditions, Purchaser shall (and Parent shall cause Purchaser to) consummate the Offer in accordance with its terms and accept for payment and thereafter pay for all Shares validly tendered and not validly withdrawn pursuant to the Offer as promptly as practicable (and in any event within three (3) Business Days) after the Expiration Date and in any event in compliance with Rule 14e-1(c) under the Exchange Act (the time of such acceptance for payment, the “Acceptance Time”). The initial expiration date Offer Price payable in respect of each Share validly tendered and not validly withdrawn pursuant to the Offer shall be the twentieth Business Day following the commencement of the Offer (determined under Rule 14d-1(g)(3) promulgated under the 1934 Act). Acquisition Sub expressly reserves the right to waive any of the conditions paid net to the Offerseller of such Share in cash, modify without interest, subject to the deduction or withholding of any Taxes as contemplated in Section 2.9, on the terms of the Offer, and increase the Offer Price; PROVIDED that, without the consent of the Company, Acquisition Sub shall not (i) increase or reduce the Maximum Number, (ii) reduce the price per Share to be paid pursuant to the Offer, (iii) add subject to the conditions set forth in Annex I or modify any condition this Agreement. The time scheduled for payment for shares of Company Common Stock accepted for payment pursuant to and subject to the conditions of the Offer is referred to in this Agreement as the “Offer Closing”, and the date on which the Offer Closing occurs is referred to in this Agreement as the “Offer Closing Date.” (c) The Offer shall be made by means of an offer to purchase that describes the terms and conditions of the Offer as set forth in Annex Ithis Agreement. Purchaser and Parent expressly reserve the right to waive (in whole or in part) any Offer Condition at any time and from time to time, to increase the Offer Price or to make any other changes in the terms and conditions of the Offer; provided, however, that without the prior written consent of the Company (which may be granted or withheld in the Company’s sole discretion), Purchaser shall not (i) decrease the Offer Price (other than in connection with Section 1.1(g) hereof), (ivii) change the form of consideration payable in the Offer, or (viii) otherwise amend reduce the number of Shares to be purchased in the Offer (other than in connection with Section 1.1(g) hereof), (iv) amend or modify any of the Offer Conditions in a manner that is adverse to the holders of SharesShares or impose conditions to the Offer in addition to the Offer Conditions, (v) amend, modify or waive the Minimum Condition, (vi) extend or otherwise change any time period for the performance of any obligation of Purchaser or Parent (including the Expiration Date) in a manner that is adverse to the holders of Shares other than pursuant to and in accordance with this Agreement, or (vii) take any action (or fail to take any action) that would result in the Merger not being permitted to be effected pursuant to Section 251(h) of the DGCL. (d) Unless extended as provided in this Agreement, the Offer shall initially be scheduled to expire at midnight, New York City time, on the date that is twenty (20) Business Days (calculated as set forth in Rule 14d-1(g)(3) and Rule 14e-1(a) under the Exchange Act) after the commencement (within the meaning of Rule 14d-2 under the Exchange Act) of the Offer (such later date being the “Initial Expiration Date”). Acquisition Sub Notwithstanding the foregoing, if, at midnight, New York City time, on the Initial Expiration Date or any subsequent date as of which the Offer is scheduled to expire, any Offer Condition is not satisfied or, to the extent waivable in accordance with the terms hereof, has not been waived by Purchaser or Parent, Purchaser shall (subject to the rights or remedies of the parties hereto hereunder, including under Article VII), extend (and re-extend) the Offer and its expiration date beyond the Initial Expiration Date (the Initial Expiration Date as it may be extended herein is referred to as the “Expiration Date”) for one or more periods, in consecutive increments of up to ten (10) Business Days each, the length of each such period to be determined by Parent in its sole discretion (or such longer period as Parent and the Company may mutually agree) to permit such Offer Condition to be satisfied (it being understood, for the avoidance of doubt, that the Offer shall not be extended pursuant to this sentence if all Offer Conditions have been satisfied or waived); provided, however, that in no event shall Purchaser (i) be required to extend the Offer beyond the Outside Date or (ii) be permitted to extend the Offer beyond the Outside Date without the prior written consent of the Company. Notwithstanding anything herein to the contrary, Purchaser shall, without the written consent of the Company, extend the Offer for any period required by any rule, regulation, interpretation or position of the SEC or its staff, any rule or regulation of the staff thereof NASDAQ, or any other applicable Law, in each case, applicable to the Offer or any period required by applicable law. If any of the conditions to Offer. (e) Purchaser shall not terminate the Offer is not satisfied or waived on prior to any scheduled expiration date of the Offer, Acquisition Sub shall extend the Offer from time to time until such conditions are satisfied or waived; PROVIDED that (i) each such extension of the Offer shall be for a period of not more than ten Business Days, and (ii) Acquisition Sub shall not, Expiration Date without the prior written consent of the Company, extend except for a termination of this Agreement permitted in accordance with the Offer beyond terms of Section 7.1. In the Termination Date. Subject event that this Agreement is terminated pursuant to Section 7.1, Purchaser shall (and Parent shall cause Purchaser to) promptly (and in any event within twenty-four (24) hours of such termination), irrevocably and unconditionally terminate the Offer, not acquire any Shares pursuant thereto, and cause any depositary acting on its behalf to promptly return in accordance with applicable Law all tendered Shares to the foregoing and upon registered holders thereof. (f) On the terms and subject to the conditions commencement date of the Offer, Acquisition Sub Purchaser and Parent shall accept for payment and pay for, as promptly as practicable after the expiration of the Offer, all Shares validly tendered and not withdrawn (including if no Shares are validly tendered and not withdrawn), but not in excess of the Maximum Number. (bi) As soon as practicable on the date of commencement of the Offer, BMS and Acquisition Sub shall file or cause to be filed with the SEC SEC, in accordance with Rule 14d-3 under the Exchange Act, a Tender Offer Statement on Schedule TO (the "SCHEDULE TO") with respect to the Offer (such together with all amendments, supplements and exhibits thereto, the “Schedule TO TO”) that will contain or incorporate by reference the related offer to purchase the Shares pursuant to the Offer, the form of the related letter of transmittal, the summary advertisement and such other ancillary Offer documents included therein pursuant to which the Offer will be mademade and instruments pursuant to which the Offer will be made (collectively, and together with any all exhibits, amendments and supplements or amendments thereto, the "OFFER DOCUMENTS"“Offer Documents”); and (ii) cause the Schedule TO and related Offer Documents to be disseminated to holders of Shares in accordance with applicable federal securities Laws. The Company shall promptly furnish to Purchaser and Parent in writing all information concerning the Company and its stockholders that may be required by applicable Law to be set forth in the Offer Documents or reasonably requested in connection with any action contemplated by this Section 1.1(f). BMSThe Company and its counsel shall be given reasonable opportunity to review and comment on the Offer Documents prior to the filing thereof with the SEC, Acquisition Sub and Purchaser and Parent shall give reasonable and good faith consideration to any comments made by the Company and its counsel. Each of Purchaser, Parent and the Company each agrees to promptly to correct any information provided by it for use in the Offer Documents if and to the extent that such information shall have become false or misleading in any material respectrespect or as otherwise required by applicable Law. BMS Purchaser and Acquisition Sub Parent further agree to take all steps necessary to cause the Schedule TO Offer Documents as so corrected (if applicable) to be filed with the SEC. BMS SEC and Acquisition Sub shall deliver or cause to be delivered to the Company, or such other Person as the Company shall designate, the Offer Documents (and any amendments thereto) as so corrected, in such quantities as shall be necessary for dissemination to all holders of Shares and Company Options. The Company shall, at its expense, cause the Offer Documents (and any amendments thereto) to be disseminated to holders of Shares and Company OptionsShares, in each case as and to the extent required by applicable federal securities lawsLaws. The Company and its counsel shall be given an opportunity to review and comment on the Offer Documents prior to their being filed with the SEC or disseminated to the holders Upon receipt of Shares and Company Options. BMS and Acquisition Sub shall provide the Company and its counsel with any comments or other communications, whether written or oraloral comments by Purchaser, that BMS, Acquisition Sub Parent or its their counsel may receive from time to time from the SEC or its staff with respect to the Offer Documents Documents, or any request from the SEC or its staff for amendments or supplements to the Offer Documents, Purchaser and Parent agree to (i) promptly after receipt provide the Company and its counsel with a copy of any such written comments or requests (or a description of any such oral comments or requests); (ii) provide the Company and its counsel a reasonable opportunity to comment on any proposed response thereto, and to give reasonable and good faith consideration to any such comments made by the Company and its counsel; (iii) provide the Company and its counsel an opportunity to participate with Purchaser, Parent or other communicationstheir counsel in any material discussions or meetings with the SEC or its staff; and (iv) provide the Company with copies of any written comments or responses submitted by Purchaser and Parent in response thereto. (cg) Each certificate for Shares issued to Acquisition Sub representing Shares accepted for purchase If, during the period commencing on the Agreement Date and paid for by Acquisition Sub in ending at the Offer Closing Date, the outstanding shares of Company Common Stock are changed into a different number or class of shares by reason of any stock split, division or subdivision of shares, stock dividend, reverse stock split, consolidation of shares, reclassification, recapitalization or other similar transaction, then the Offer Price shall bear be appropriately adjusted; provided, however, that nothing in this Section 1.1(g) shall be construed to permit the Company to take any action with respect to the Company Common Stock that is prohibited by the terms of this Agreement. (h) Subject in all respects to the other terms and conditions of this Agreement and the Offer Conditions, Parent shall provide or cause to be provided to Purchaser on a legend in substantially timely basis the funds necessary to purchase any shares of Company Common Stock that Purchaser becomes obligated to purchase pursuant to the Offer. (i) This Agreement and the transactions contemplated hereby shall be effected under Section 251(h) of the DGCL and Parent and Purchaser shall cause the Merger to be effected as soon as practicable following form: THE SECURITIES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO RESTRICTIONS ON TRANSFER AS SET FORTH IN THE STOCKHOLDER AGREEMENT, DATED SEPTEMBER 19, 2001, AMONG IMCLONE SYSTEMS INCORPORATED, ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB COMPANY AND ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB BIOLOGICS COMPANY, A COPY OF WHICH MAY BE OBTAINED FROM THE CORPORATE SECRETARY OF IMCLONE SYSTEMS INCORPORATEDthe consummation of the Offer.

The Offer. (a) As promptly as practicable Provided that this Agreement shall not have been terminated in accordance with Section 7.1, within seven business days after the date hereofof this Agreement, but in no event later than ten Business Days after Purchaser shall (and Parent shall cause Purchaser to) commence (within the date hereofmeaning of Rule 14d-2 under the Securities Exchange Act of 1934, Acquisition Sub shall commence an offer as amended (the "OFFER"“Exchange Act”)) the Offer to purchase for cash 14,392,003 all Shares at the Offer Price (which shall includeas adjusted as provided in this Agreement, for purposes if applicable) and in compliance with Section 14(d) of the Exchange Act and all other provisions of applicable securities laws. (b) Subject to the terms and conditions of this Agreement, including the prior satisfaction or waiver of the conditions set forth in Annex I (the “Offer Conditions”), promptly after the latest of (i) all the earliest date as of which Purchaser is permitted under applicable Law to accept for payment Shares issuable in respect of exercisable, in-the-money Company Options which have been "conditionally exercised" by the holder thereof for purposes of participating in tendered pursuant to the Offer, and (ii) all Shares issued prior to the expiration earliest date as of which each of the Offer upon Conditions has been satisfied, or waived by Parent or Purchaser, and (iii) the conversion of any convertible securities or upon Expiration Date, Purchaser shall (and Parent shall cause Purchaser to) consummate the exercise of any options or warrants) (such number of Shares, the "MAXIMUM NUMBER") at a price of $70.00 per Share, net Offer in accordance with its terms and accept for payment each Share validly tendered and not properly withdrawn pursuant to the seller in cash Offer and promptly following the acceptance of Shares for payment pursuant to the Offer pay the Offer Price (such price, as may hereafter be increased, without interest) for each Share validly tendered and not properly withdrawn pursuant to the "OFFER PRICE")Offer. The obligation of Acquisition Sub Purchaser (and of Parent to cause Purchaser) to accept for payment any Shares payment, and pay the Offer Price (without interest) for, each Share validly tendered and not properly withdrawn pursuant to the Offer shall be subject only to the satisfaction, or waiver by Parent or Purchaser, of each of the Offer Conditions. (c) The Offer shall be made by means of an offer to purchase (the “Offer to Purchase”) that contains the terms set forth in this Agreement, the Minimum Condition (as defined in Annex I) and the other conditions set forth in Annex I hereto. The initial expiration date of the Offer shall be the twentieth Business Day following the commencement of the Offer (determined under Rule 14d-1(g)(3) promulgated under the 1934 Act). Acquisition Sub I. Purchaser expressly reserves the right to (x) increase the Offer Price and (y) waive any of the conditions to the Offer, modify Offer Condition and make any other changes in the terms and conditions of the Offer; provided, and increase the Offer Price; PROVIDED thathowever, that unless otherwise provided by this Agreement, without the prior written consent of the Company, Acquisition Sub Purchaser shall not (i) increase or reduce decrease the Maximum NumberOffer Price, (ii) reduce the price per Share to be paid pursuant to the Offer, (iii) add to the conditions set forth in Annex I or modify any condition set forth in Annex I, (iv) change the form of consideration payable in the Offer, (iii) decrease the maximum number of Shares sought to be purchased in the Offer, (iv) impose conditions or requirements to the Offer in addition to the Offer Conditions, (v) amend or modify any of the Offer Conditions in a manner that adversely affects, or reasonably could adversely affect, the holder of Shares, (vi) change or waive the Minimum Condition, or (vii) extend or otherwise amend change the expiration date of the Offer in a manner other than as required or permitted by this Agreement. (d) Unless extended pursuant to and in accordance with the terms of this Agreement, the Offer shall expire at midnight (New York City time) on the date that is 20 business days (for this purpose calculated in accordance with Rule 14d-1(g)(3) under the Exchange Act) following the commencement (within the meaning of Rule 14d-2 under the Exchange Act) of the Offer (the “Initial Expiration Date”) or, in the event the Initial Expiration Date has been extended pursuant to and in accordance with this Agreement, the date to which the Offer has been so extended (the Initial Expiration Date, or such later date to which the Initial Expiration Date has been extended pursuant to and in accordance with this Agreement, is referred to as the “Expiration Date”). (e) The Offer shall be extended from time to time as follows: (i) If on or prior to any manner adverse then scheduled Expiration Date, any of the Offer Conditions have not been satisfied (other than conditions which by their nature are to be satisfied at the Acceptance Time), or waived by Parent or Purchaser if permitted hereunder, then Purchaser may (or at the request of the Company, Purchaser shall) extend the Offer for one or more successive periods of 10 business days (or such other number of business days as may be jointly determined by Purchaser and the Company) each in order to permit the satisfaction of such conditions (subject to the holders right of Shares. Acquisition Sub the Purchaser to waive any condition (other than the Minimum Condition) in accordance with this Agreement), provided such extension of the Offer period does not extend past the earlier of (x) the termination of this Agreement pursuant to Section 7.1 and (y) the date, as applicable, that is (A) 90 days after commencement of the Offer (the “Initial Outside Date”), or (B) 120 days after commencement of the Offer in the event that the HSR Condition or the Banking Moratorium Condition shall not have been satisfied, or waived by Parent or Purchaser if permitted hereunder, by the Initial Outside Date (the “Extended Outside Date”); and (ii) Purchaser shall extend the Offer for any period or periods required by any applicable law, rule, regulation, interpretation or position of the SEC Securities and Exchange Commission (“SEC”) or its staff or The NASDAQ Stock Market LLC (the staff thereof applicable “NASDAQ”) or its staff. (f) If fewer than 90% of the number of outstanding Shares are accepted for payment pursuant to the Offer or any period required by applicable law. If any acquired through the Offer and exercise of the conditions Top-Up-Option, Purchaser may, in its sole discretion, provide for one “subsequent offering period” (and one or more extensions thereof) in accordance with Rule 14d-11 under the Exchange Act. Additionally, in the event that more than 80% of the then outstanding Shares have been validly tendered and not properly withdrawn pursuant to the Offer is not satisfied following the Expiration Date, Purchaser shall (and Parent shall cause Purchaser to), at the request of the Company, provide for one “subsequent offering period” in accordance with Rule 14d-11 under the Exchange Act of at least 10 business days immediately following the Expiration Date unless (i) Parent and Purchaser exercise the Top-Up Option or waived on any scheduled expiration date (ii) Parent, Purchaser and their respective Subsidiaries, in the aggregate, own more than 90% of the outstanding Shares. Subject to the terms and conditions of this Agreement and the Offer, Acquisition Sub Purchaser shall extend (and Parent shall cause Purchaser to) accept for payment, and pay the Offer from time Price (without interest) for, each Share that is validly tendered and not properly withdrawn pursuant to time until such conditions are satisfied or waived; PROVIDED that (i) each such extension of the Offer during such “subsequent offering period” promptly after any such Share is tendered during such “subsequent offering period.” The Offer Documents will provide for the possibility of a “subsequent offering period” in a manner consistent with the terms of this Section 1.1(f). (g) Purchaser shall be for a period of not more than ten Business Days, and (ii) Acquisition Sub shall not, terminate the Offer prior to any scheduled Expiration Date without the prior written consent of the Company, extend Company except in the Offer beyond the Termination Date. Subject event that this Agreement is terminated pursuant to the foregoing and upon the terms and subject to the conditions of the Offer, Acquisition Sub shall accept for payment and pay for, as promptly as practicable after the expiration of the Offer, all Shares validly tendered and not withdrawn (including if no Shares are validly tendered and not withdrawn), but not in excess of the Maximum NumberSection 7.1. (bh) In the event that this Agreement is terminated pursuant to Section 7.1, Purchaser shall (and Parent shall cause Purchaser to) promptly (and in any event within 24 hours of such termination), irrevocably and unconditionally terminate the Offer and shall not acquire any shares pursuant to the Offer. (i) As soon as practicable on the date of commencement of the OfferOffer (within the meaning of Rule 14d-2 under the Exchange Act), BMS Parent and Acquisition Sub Purchaser shall file with the SEC SEC, pursuant to Regulation M-A under the Exchange Act (“Regulation M-A”), a Tender Offer Statement on Schedule TO (the "SCHEDULE TO") with respect to the Offer (such together with all amendments, supplements and exhibits thereto, the “Schedule TO”). The Schedule TO shall include, as exhibits, the Offer to Purchase and such a form of letter of transmittal and summary advertisement, and ancillary documents included therein and instruments pursuant to which the Offer will be mademade (collectively, together with any amendments and supplements or thereto, and together with the Schedule TO and any amendments and supplements thereto, the "OFFER DOCUMENTS"“Offer Documents”). BMSThe Company will provide to Parent and Purchaser any information with respect to itself and its officers, Acquisition Sub directors and Affiliates required to be provided in the Offer Documents under applicable Laws or as reasonably requested by Parent and Purchaser. Parent and Purchaser agree to take all steps necessary to cause the Offer Documents to be filed with the SEC and disseminated to holders of Shares, in each case as and to the extent required by the Exchange Act. Parent and Purchaser shall use commercially reasonable efforts to cause the Offer Documents to comply in all material respects with the Exchange Act and all other applicable Laws. Parent and Purchaser, on the one hand, and the Company each agrees Company, on the other hand, agree to promptly to correct any information provided by it for use in the Offer Documents if and to the extent that such information it shall have become false or misleading in any material respectrespect or as otherwise required by applicable Law. BMS Parent and Acquisition Sub Purchaser further agree to take all steps necessary to cause the Schedule TO Offer Documents, as so corrected (if applicable), to be filed with the SEC. BMS SEC and Acquisition Sub shall deliver or cause to be delivered to the Company, or such other Person as the Company shall designate, the Offer Documents (and any amendments thereto) as so corrected, in such quantities as shall be necessary for dissemination to all holders of Shares and Company Options. The Company shall, at its expense, cause the Offer Documents (and any amendments thereto) to be disseminated to holders of Shares and Company OptionsShares, in each case as and to the extent required by applicable federal securities lawsthe Exchange Act. The Company and its counsel shall be given an a reasonable opportunity to review and comment on upon the Offer Documents prior to their being before they are filed with the SEC or disseminated to the holders of Shares Shares, and Parent and Purchaser shall give due consideration to all the reasonable additions, deletions or changes suggested thereto by the Company Optionsand its counsel. BMS In addition, Parent and Acquisition Sub Purchaser shall provide the Company and its counsel with copies of any comments or other communicationswritten comments, whether written or oraland shall inform them of any oral comments, that BMSParent, Acquisition Sub Purchaser or its their counsel may receive from time to time from the SEC or its staff with respect to the Offer Documents promptly after receipt of such comments, and any written or oral responses thereto. The Company and its counsel shall be given a reasonable opportunity to review and comment on any such written responses before they are submitted to the SEC or its staff, and Parent and Purchaser shall give due consideration to all reasonable additions, deletions or changes suggested thereto by the Company and its counsel. Each of Parent and Purchaser shall respond promptly to any comments of the SEC or other communicationsits staff with respect to the Offer Documents or the Offer. The Company hereby consents to the inclusion in the Offer Documents of the Company Board Recommendation, as such Company Board Recommendation may be amended and for so long as such Company Board Recommendation is not withdrawn (in each case as permitted by this Agreement). If the Offer is terminated or withdrawn by Purchaser, or this Agreement is terminated prior to the purchase of Shares in the Offer, Purchaser shall promptly return, and shall cause any depository, acting on behalf of Purchaser to return, all tendered Shares to the registered holders thereof. (cj) Each certificate The Offer Price shall be adjusted appropriately to reflect the effect of any stock split, reverse stock split, stock dividend (including any dividend or distribution of securities convertible into Common Stock), cash dividend, reorganization, recapitalization, reclassification, combination, exchange of shares or other like change with respect to Common Stock occurring on or after the date hereof and prior to Purchaser’s acceptance for payment of, and payment for, Shares issued pursuant to Acquisition Sub representing the Offer. (k) Parent shall cause to be provided to Purchaser all of the funds necessary to purchase any Shares accepted for that Purchaser becomes obligated to purchase pursuant to the Offer, and paid for by Acquisition Sub in the Offer shall bear cause Purchaser to perform, on a legend in substantially the following form: THE SECURITIES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO RESTRICTIONS ON TRANSFER AS SET FORTH IN THE STOCKHOLDER AGREEMENTtimely basis, DATED SEPTEMBER 19, 2001, AMONG IMCLONE SYSTEMS INCORPORATED, ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB COMPANY AND ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB BIOLOGICS COMPANY, A COPY OF WHICH MAY BE OBTAINED FROM THE CORPORATE SECRETARY OF IMCLONE SYSTEMS INCORPORATEDall of Purchaser’s obligations under this Agreement.

The Offer. (a) As Provided that this Agreement shall not have been terminated in accordance with Section 7.1, as promptly as practicable after (and in any event within ten (10) Business Days from the date hereof), but in no event later than ten Business Days after Purchaser shall (and Parent shall cause Purchaser to) commence (within the date hereofmeaning of Rule 14d-2 under the Securities Exchange Act of 1934, Acquisition Sub shall commence an offer as amended, and the rules and regulations promulgated thereunder (the "OFFER"“Exchange Act”)) the Offer to purchase for cash 14,392,003 Shares (which shall include, for purposes of this Agreement, (i) all Shares issuable at the Offer Price, subject to the satisfaction, or waiver by Parent or Purchaser, of the other conditions and requirements set forth in Annex I. (b) Subject to Section 1.1(a), Purchaser shall (and Parent shall cause Purchaser to) consummate the Offer in accordance with its terms and accept for payment and pay for all Shares validly tendered and not withdrawn pursuant to the Offer as promptly as practicable. The Offer Price payable in respect of exercisable, in-the-money Company Options which have been "conditionally exercised" by the holder thereof for purposes of participating in the Offer, each Share validly tendered and (ii) all Shares issued prior to the expiration of the Offer upon the conversion of any convertible securities or upon the exercise of any options or warrants) (such number of Shares, the "MAXIMUM NUMBER") at a price of $70.00 per Share, net to the seller in cash (such price, as may hereafter be increased, the "OFFER PRICE"). The obligation of Acquisition Sub to accept for payment any Shares tendered not withdrawn pursuant to the Offer shall be subject only paid net to the Seller in cash subject to withholding as provided in Section 2.2(e). (c) The Offer shall be made by means of an offer to purchase (the “Offer to Purchase”) that contains the terms set forth in this Agreement and the other conditions and requirements set forth in Annex I hereto. The initial expiration date of the Offer shall be the twentieth Business Day following the commencement of the Offer (determined under Rule 14d-1(g)(3) promulgated under the 1934 Act). Acquisition Sub I. Parent and Purchaser expressly reserves reserve the right to waive any of the conditions to the Offer, modify the terms of the Offer, and increase the Offer Price; PROVIDED that, without Price or to make any other changes in the consent terms and conditions of the Companyoffer; provided, Acquisition Sub however, that unless otherwise provided by this Agreement or as previously approved by the Company in writing, Parent and Purchaser shall not (i) increase or reduce decrease the Maximum NumberOffer Price, (ii) reduce the price per Share to be paid pursuant to the Offer, (iii) add to the conditions set forth in Annex I or modify any condition set forth in Annex I, (iv) change the form of consideration payable in the Offer, (iii) reduce the maximum number of Shares to be purchased in the Offer, (iv) impose conditions to the Offer that are different from, or in addition to, the conditions set forth in Annex I, (v) otherwise waive the Minimum Condition as defined in Annex I, (vi) amend the Offer in any manner adverse to the holders of Shares. Acquisition Sub shall extend the Offer for any period required by any rule, regulation, interpretation or position of the SEC or the staff thereof applicable to the Offer or any period required by applicable law. If any of the conditions to the Offer is not satisfied or waived on any scheduled expiration date set forth in Annex I in a manner adverse to the holders of the Offer, Acquisition Sub shall Shares or (vii) extend the expiration of the Offer in a manner other than as required by this Agreement. (d) Unless extended pursuant to and in accordance with the terms of this Agreement, the Offer shall expire at midnight (New York City time) on the date that is twenty (20) Business Days (for this purpose calculated in accordance with Rule 14d-1(g)(3) under the Exchange Act) following the commencement (within the meaning of Rule 14d-2 under the Exchange Act) of the Offer (the “Initial Expiration Date”) or, in the event the Initial Expiration Date has been extended pursuant to, and in accordance with this Agreement, the date to which the Offer has been so extended (the Initial Expiration Date, or such later date to which the Initial Expiration Date has been extended pursuant to and in accordance with this Agreement, is referred to as the “Expiration Date”). (e) The Offer shall be extended from time to time until such conditions are satisfied or waived; PROVIDED that (i) each such extension of the Offer shall be for a period of not more than ten Business Days, and (ii) Acquisition Sub shall not, without the prior written consent of the Company, extend the Offer beyond the Termination Date. Subject to the foregoing and upon the terms and subject to the conditions of the Offer, Acquisition Sub shall accept for payment and pay for, as promptly as practicable after the expiration of the Offer, all Shares validly tendered and not withdrawn (including if no Shares are validly tendered and not withdrawn), but not in excess of the Maximum Number. (b) As soon as practicable on the date of commencement of the Offer, BMS and Acquisition Sub shall file with the SEC a Tender Offer Statement on Schedule TO (the "SCHEDULE TO") with respect to the Offer (such Schedule TO and such documents included therein pursuant to which the Offer will be made, together with any supplements or amendments thereto, the "OFFER DOCUMENTS"). BMS, Acquisition Sub and the Company each agrees promptly to correct any information provided by it for use in the Offer Documents if and to the extent that such information shall have become false or misleading in any material respect. BMS and Acquisition Sub agree to take all steps necessary to cause the Schedule TO as so corrected to be filed with the SEC. BMS and Acquisition Sub shall deliver or cause to be delivered to the Company, or such other Person as the Company shall designate, the Offer Documents (and any amendments thereto) as so corrected, in such quantities as shall be necessary for dissemination to all holders of Shares and Company Options. The Company shall, at its expense, cause the Offer Documents (and any amendments thereto) to be disseminated to holders of Shares and Company Options, in each case as and to the extent required by applicable federal securities laws. The Company and its counsel shall be given an opportunity to review and comment on the Offer Documents prior to their being filed with the SEC or disseminated to the holders of Shares and Company Options. BMS and Acquisition Sub shall provide the Company and its counsel with any comments or other communications, whether written or oral, that BMS, Acquisition Sub or its counsel may receive from time to time from the SEC or its staff with respect to the Offer Documents promptly after receipt of such comments or other communications. (c) Each certificate for Shares issued to Acquisition Sub representing Shares accepted for purchase and paid for by Acquisition Sub in the Offer shall bear a legend in substantially the following form: THE SECURITIES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO RESTRICTIONS ON TRANSFER AS SET FORTH IN THE STOCKHOLDER AGREEMENT, DATED SEPTEMBER 19, 2001, AMONG IMCLONE SYSTEMS INCORPORATED, ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB COMPANY AND ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB BIOLOGICS COMPANY, A COPY OF WHICH MAY BE OBTAINED FROM THE CORPORATE SECRETARY OF IMCLONE SYSTEMS INCORPORATED.follows:

The Offer. (a) As Provided that this Agreement shall not have been terminated in accordance with Article VII and none of the events specified in clause (iii) of Annex I shall have occurred and then be continuing, as promptly as practicable practical after the date hereof, but in no event later than ten Business Days the sixth business day after the date hereof, Acquisition Sub Parent shall cause Purchaser to commence an offer (within the "OFFER"meaning of Rule 14d-2 under the Exchange Act) to purchase for cash 14,392,003 Shares (which shall include, for purposes of this Agreement, (i) all Shares issuable in respect of exercisable, in-the-money Company Options which have been "conditionally exercised" by the holder thereof for purposes of participating in the Offer, and (ii) all Shares issued prior to the expiration of the Offer upon at the conversion of any convertible securities or upon the exercise of any options or warrants) (such number of Shares, the "MAXIMUM NUMBER") at a price of $70.00 per Share, net to the seller in cash (such price, as may hereafter be increased, the "OFFER PRICE")Offer Price. The obligation of Acquisition Sub Purchaser to consummate the Offer, to accept for payment and to pay for any Shares tendered pursuant to the Offer shall be subject only to the satisfaction of the conditions set forth in Annex I hereto. I. The initial expiration date of the Offer shall be the twentieth Business Day business day following commencement (within the commencement meaning of Rule 14d-2 under the Exchange Act) of the Offer. Parent shall cause Purchaser to, and Purchaser shall, subject to the conditions provided in Annex I, accept for payment and pay for all Shares validly tendered and not withdrawn pursuant to the Offer (determined under as soon as practicable after such expiration date and in any event in compliance with the obligations respecting prompt payment pursuant to Rule 14d-1(g)(314e-1(c) promulgated under the 1934 Exchange Act). Acquisition Sub expressly On or prior to the dates that the Purchaser becomes obligated to accept for payment and pay for Shares pursuant to the Offer, Parent shall provide or cause to be provided to the Purchaser the funds necessary to pay for all Shares that Purchaser becomes so obligated to accept for payment and pay for pursuant to the Offer. The Offer Price shall be net to the seller in cash, without interest, subject to any applicable withholding taxes. (b) Purchaser reserves the right to (i) waive any of the conditions set forth in Annex I (other than the Minimum Condition and the condition relating to the expiration of the waiting period under the HSR Act), (ii) increase the price per Share payable in the Offer, modify and (iii) make any other changes in the terms of the Offer; provided, and increase however, unless previously approved by the Offer Price; PROVIDED that, without Company in writing no change may be made which (a) reduces the consent maximum number of the Company, Acquisition Sub shall not (i) increase or reduce the Maximum Number, (ii) reduce the price per Share Shares to be paid purchased pursuant to the Offer, (iiib) add decreases the price per Share payable pursuant to the Offer, (c) changes the form of consideration to be paid for the Shares pursuant to the Offer, (d) imposes conditions to the Offer in addition to the conditions set forth in Annex I or modify any condition set forth in Annex I, (ive) change waives the form Minimum Condition or waives the condition relating to the expiration of consideration payable the waiting period under the HSR Act or (f) makes other changes in the Offer, or (v) otherwise amend terms and conditions of the Offer that are in any manner adverse to the holders of Shares. Acquisition Sub shall extend the Offer for any period required by any rule, regulation, interpretation or position of the SEC or the staff thereof applicable to the Offer or any period required by applicable law. If any of the conditions to the Offer is not satisfied or waived on any scheduled expiration date of the Offer, Acquisition Sub shall extend the Offer from time to time until such conditions are satisfied or waived; PROVIDED that (i) each such extension of the Offer shall be for a period of not more than ten Business Days, and (ii) Acquisition Sub shall not, without Without the prior written consent of the Company, Purchaser shall not extend the expiration date of the Offer beyond the Termination Date. Subject to the foregoing and upon the terms and subject to the conditions initial expiration date of the Offer, Acquisition Sub shall accept for payment except (x) as required by applicable law including applicable rules and pay forregulations of the SEC or any interpretation or position of the SEC staff, as promptly as practicable after (y) that if, immediately prior to the expiration date of the OfferOffer (as it may be extended), all the Shares validly tendered and not withdrawn pursuant to the Offer constitute less than 90% of the outstanding Shares, Purchaser may, in its sole discretion, extend the Offer for one or more periods not to exceed an aggregate of ten business days, notwithstanding that all conditions to the Offer are satisfied as of such expiration date of the Offer; provided that after the initial expiration date, the Offer shall not be subject to any conditions that are at the time of such extension satisfied other than the Minimum Condition and the conditions set forth in paragraph (including a) of Annex I, or (z) that if no Shares are validly tendered and any condition to the Offer has not withdrawn)been satisfied or waived, Purchaser shall extend the expiration date of the Offer for one or more periods, but not in excess no event later than the Outside Date. In addition, the Offer Price may be increased and the Offer may be extended to the extent required by law in connection with such increase without the consent of the Maximum NumberCompany. (bc) The Offer shall be made by means of an offer to purchase (the "Offer to Purchase") subject only to the conditions set forth in Annex I. As soon as reasonably practicable on the date of commencement of the OfferOffer is commenced, BMS Parent and Acquisition Sub Purchaser shall file with the SEC a Tender Offer Statement on Schedule TO (together with all amendments and supplements thereto, the "SCHEDULE Schedule TO") with respect to the Offer that (such Schedule TO i) will comply in all material respects with the provisions of all applicable federal securities laws and such documents included therein pursuant to which (ii) will contain (including as an exhibit) or incorporate by reference the Offer will be madeto Purchase, a form of the related letter of transmittal and a summary advertisement (which documents, together with any supplements or amendments thereto, are referred to collectively herein as the "OFFER DOCUMENTSOffer Documents"). BMSEach of the Company, Acquisition Sub on the one hand, and Parent and Purchaser, on the Company each other hand, agrees promptly to correct any information provided by it in writing for use in the Schedule TO or the Offer Documents if and to the extent that such information the Schedule TO or the Offer Documents shall be, or have become become, false or misleading in any material respect. BMS , and Acquisition Sub Parent and Purchaser further agree to take all steps necessary to cause the Schedule TO TO, as so corrected corrected, to be filed with the SEC. BMS SEC and Acquisition Sub shall deliver or cause to be delivered to the Company, or such other Person as the Company shall designate, the Offer Documents (and any amendments thereto) Documents, as so corrected, in such quantities as shall be necessary for dissemination to all holders of Shares and Company Options. The Company shall, at its expense, cause the Offer Documents (and any amendments thereto) to be disseminated to holders of Shares and any other holder of securities issued by the Company Options(if any), in each case as and to the extent required by applicable federal securities laws. The Company Parent and its counsel shall be given an opportunity to review and comment on the Offer Documents prior to their being filed with the SEC or disseminated to the holders of Shares and Company Options. BMS and Acquisition Sub Purchaser shall provide the Company and its counsel with a reasonable opportunity to review and comment on the Schedule TO and any Offer Documents before they are filed with the SEC. Parent and Purchaser shall promptly provide the Company and its counsel in writing with, and consult with the Company and its counsel regarding, any comments Parent, Purchaser or other communications, whether written or oral, that BMS, Acquisition Sub or its their counsel may receive from time to time from the SEC or its staff with respect to the Offer Documents promptly after receipt of such comments Schedule TO or other communications. (c) Each certificate for Shares issued to Acquisition Sub representing Shares accepted for purchase and paid for by Acquisition Sub in the Offer shall bear a legend in substantially the following form: THE SECURITIES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO RESTRICTIONS ON TRANSFER AS SET FORTH IN THE STOCKHOLDER AGREEMENT, DATED SEPTEMBER 19, 2001, AMONG IMCLONE SYSTEMS INCORPORATED, ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB COMPANY AND ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB BIOLOGICS COMPANY, A COPY OF WHICH MAY BE OBTAINED FROM THE CORPORATE SECRETARY OF IMCLONE SYSTEMS INCORPORATEDDocuments.

The Offer. (a) As Provided that this Agreement shall not have been terminated in accordance with Section 8.1 hereof and none of the events set forth in Annex I hereto shall have occurred and be existing, Purchaser shall commence (within the meaning of Rule 14d-2 under the Securities Exchange Act of 1934, as amended (the "Exchange Act")) the Offer as promptly as practicable after the date hereofreasonably practicable, but in no event later than ten Business Days after seven business days following the date hereof, Acquisition Sub shall commence an offer (public announcement by Parent and the "OFFER") to purchase for cash 14,392,003 Shares (which shall include, for purposes Company of the execution of this Agreement, (i) all Shares issuable in respect of exercisable, in-the-money Company Options which have been "conditionally exercised" by the holder thereof for purposes of participating in the Offer, and (ii) all Shares issued prior to the expiration of the Offer upon the conversion of any convertible securities or upon the exercise of any options or warrants) (such number of Shares, the "MAXIMUM NUMBER") at a price of $70.00 per Share, net to the seller in cash (such price, as may hereafter be increased, the "OFFER PRICE"). The obligation of Acquisition Sub Purchaser to accept for payment and pay for any Shares tendered pursuant to the Offer shall be subject only to the satisfaction of the conditions set forth in Annex I hereto. The initial expiration date of the Offer shall be the twentieth Business Day following the commencement of the Offer (determined under Rule 14d-1(g)(3) promulgated under the 1934 Act). Acquisition Sub I. Purchaser expressly reserves the right from time to waive any of the conditions time, subject to the Offer, modify the terms of the Offer, Sections 1.1(b) and increase the Offer Price; PROVIDED that1.1(d) hereof, without the consent of the Company to waive any such condition, to increase the Per Share Amount, or to make any other changes in the terms and conditions of the Offer. The Per Share Amount shall be net to the seller in cash, without interest, subject to reduction only for any applicable withholding taxes or stock transfer taxes payable by the seller. The Company agrees that no Shares held by the Company or any Subsidiary (as hereinafter defined) will be tendered pursuant to the Offer. (b) Without the prior written consent of the Company, Acquisition Sub Purchaser shall not (i) increase decrease the Per Share Amount or reduce the Maximum Number, (ii) reduce the price per Share to be paid pursuant to the Offer, (iii) add to the conditions set forth in Annex I or modify any condition set forth in Annex I, (iv) change the form of consideration payable in the Offer, (ii) seek to purchase less than all outstanding Shares, (iii) amend or waive satisfaction of the Minimum Condition (as defined in Annex I) or (viv) otherwise impose conditions to the Offer in addition to those set forth in Annex I hereto, or amend any other term or condition of the Offer in any manner materially adverse to the holders of Shares. Acquisition Sub shall extend the Offer for any period required by any rule, regulation, interpretation or position of the SEC or the staff thereof applicable to the Offer or any period required by applicable law. If any of the conditions to the Offer is not satisfied or waived on any scheduled expiration date of the Offer, Acquisition Sub shall extend the Offer from time to time until such conditions are satisfied or waived; PROVIDED that (i) each such extension of the Offer shall be for a period of not more than ten Business Days, and (ii) Acquisition Sub shall not, without the prior written consent of the Company, extend the Offer beyond the Termination Date. Subject to the foregoing and upon Upon the terms and subject to the conditions of the OfferOffer and this Agreement, Acquisition Sub shall Purchaser will accept for payment and pay forpurchase, as promptly soon as practicable after permitted under the expiration terms of the Offer, Offer and applicable law (subject to the first proviso to Section 8.1(c)(i)) (the "Share Purchase Date") all Shares validly tendered and not withdrawn (including if no Shares are validly tendered and not withdrawn), but not in excess prior to the expiration of the Maximum NumberOffer. On or prior to the Share Purchase Date, Parent shall provide or cause to be provided to Purchaser the funds necessary to pay for Shares that Purchaser becomes obligated to accept for payment, and pay for, pursuant to the Offer. Purchaser shall not provide for a subsequent offering period in accordance with Rule 14d-11 under the Exchange Act. (bc) The Offer shall be made by means of an offer to purchase (the "Offer to Purchase") having only the conditions set forth in Annex I hereto. As soon as reasonably practicable on the date the Offer is commenced, Purchaser shall file with the Securities and Exchange Commission (the "SEC") a Tender Offer (d) The Offer to Purchase shall provide (i) for an initial expiration date of 20 business days (as defined in Rule 14d-1 under the Exchange Act) from and including the date of commencement of the Offer, BMS and Acquisition Sub shall file with the SEC a Tender Offer Statement on Schedule TO (the "SCHEDULE TOInitial Expiration Date") with respect to ). Purchaser shall extend the expiration date of the Offer until 5:00 p.m., Eastern time, on the earlier of (i) the thirtieth (30th) business day following the public announcement by Parent and the Company of the execution of this Agreement (which thirty business days shall for this purpose include the date of such public announcement) and (ii) if a tender offer (other than the Offer) shall have been commenced for all or a portion of the Shares, the business day immediately preceding the initial expiration date of such tender offer (such Schedule TO and such documents included therein pursuant to which the Offer will be made, together with any supplements or amendments theretoearlier date, the "OFFER DOCUMENTSExtended Expiration Date"). BMS, Acquisition Sub and the Company each agrees promptly to correct any information provided by it for use in the Offer Documents if and to the extent that such information Unless this Agreement shall have become false or misleading in any material respect. BMS and Acquisition Sub agree been terminated pursuant to take all steps necessary to cause Section 8.1 hereof, Purchaser agrees that it shall not, without the Schedule TO as so corrected to be filed with the SEC. BMS and Acquisition Sub shall deliver or cause to be delivered to consent of the Company, terminate or such other Person as the Company shall designate, withdraw the Offer Documents or (and any amendments theretoexcept as provided in this Section 1.1(d)) as so correctedextend the expiration date of the Offer; provided, in such quantities as shall be necessary for dissemination to all holders of Shares and Company Options. The Company shallhowever, at its expensethat, cause the Offer Documents (and any amendments thereto) to be disseminated to holders of Shares and Company Options, in each case as and subject to the extent required by applicable federal securities laws. The Company and its counsel shall be given an opportunity to review and comment on the Offer Documents prior to their being filed with the SEC or disseminated to the holders of Shares and Company Options. BMS and Acquisition Sub shall provide the Company and its counsel with any comments or other communications, whether written or oral, that BMS, Acquisition Sub or its counsel may receive from time to time from the SEC or its staff with respect to the Offer Documents promptly after receipt of such comments or other communications. (c) Each certificate for Shares issued to Acquisition Sub representing Shares accepted for purchase and paid for by Acquisition Sub in the Offer shall bear a legend in substantially the immediately following form: THE SECURITIES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO RESTRICTIONS ON TRANSFER AS SET FORTH IN THE STOCKHOLDER AGREEMENT, DATED SEPTEMBER 19, 2001, AMONG IMCLONE SYSTEMS INCORPORATED, ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB COMPANY AND ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB BIOLOGICS COMPANY, A COPY OF WHICH MAY BE OBTAINED FROM THE CORPORATE SECRETARY OF IMCLONE SYSTEMS INCORPORATED.sentence,

The Offer. (a) As Provided that this Agreement shall not have been terminated in accordance with Article VII and none of the events specified in clause (iii) of ----------- ------------ Annex I shall have occurred and then be continuing, as promptly as practicable practical ------- after the date hereof, but in no event later than ten Business Days the sixth business day after the date hereof, Acquisition Sub Parent shall cause Purchaser to commence an offer (within the "OFFER"meaning of Rule 14d-2 under the Exchange Act) to purchase for cash 14,392,003 Shares (which shall include, for purposes of this Agreement, (i) all Shares issuable in respect of exercisable, in-the-money Company Options which have been "conditionally exercised" by the holder thereof for purposes of participating in the Offer, and (ii) all Shares issued prior to the expiration of the Offer upon at the conversion of any convertible securities or upon the exercise of any options or warrants) (such number of Shares, the "MAXIMUM NUMBER") at a price of $70.00 per Share, net to the seller in cash (such price, as may hereafter be increased, the "OFFER PRICE")Offer Price. The obligation of Acquisition Sub Purchaser to consummate the Offer, to accept for payment and to pay for any Shares tendered pursuant to the Offer shall be subject only to the satisfaction of the conditions set forth in Annex I. The initial expiration date of the Offer ------- shall be the twentieth business day following commencement (within the meaning of Rule 14d-2 under the Exchange Act) of the Offer. Parent shall cause Purchaser to, and Purchaser shall, subject to the conditions provided in Annex I, accept ------- for payment and pay for all Shares validly tendered and not withdrawn pursuant to the Offer as soon as practicable after such expiration date and in any event in compliance with the obligations respecting prompt payment pursuant to Rule 14e-1(c) under the Exchange Act. On or prior to the dates that the Purchaser becomes obligated to accept for payment and pay for Shares pursuant to the Offer, Parent shall provide or cause to be provided to the Purchaser the funds necessary to pay for all Shares that Purchaser becomes so obligated to accept for payment and pay for pursuant to the Offer. The Offer Price shall be net to the seller in cash, without interest, subject to any applicable withholding taxes. (b) Purchaser reserves the right to (i) waive any of the conditions set forth in Annex I (other than the Minimum Condition and the condition relating to ------- the expiration of the waiting period under the HSR Act), (ii) increase the price per Share payable in the Offer, and (iii) make any other changes in the terms of the Offer; provided, however, unless previously approved by the Company in writing no change may be made which (a) reduces the maximum number of Shares to be purchased pursuant to the Offer, (b) decreases the price per Share payable pursuant to the Offer, (c) changes the form of consideration to be paid for the Shares pursuant to the Offer, (d) imposes conditions to the Offer in addition to the conditions set forth in Annex I hereto. The initial I, (e) waives the Minimum Condition or waives ------- the condition relating to the expiration date of the waiting period under the HSR Act or (f) makes other changes in the terms and conditions of the Offer shall be the twentieth Business Day following the commencement of the Offer (determined under Rule 14d-1(g)(3) promulgated under the 1934 Act). Acquisition Sub expressly reserves the right to waive any of the conditions to the Offer, modify the terms of the Offer, and increase the Offer Price; PROVIDED that, without the consent of the Company, Acquisition Sub shall not (i) increase or reduce the Maximum Number, (ii) reduce the price per Share to be paid pursuant to the Offer, (iii) add to the conditions set forth in Annex I or modify any condition set forth in Annex I, (iv) change the form of consideration payable in the Offer, or (v) otherwise amend the Offer that are in any manner adverse to the holders of Shares. Acquisition Sub shall extend the Offer for any period required by any rule, regulation, interpretation or position of the SEC or the staff thereof applicable to the Offer or any period required by applicable law. If any of the conditions to the Offer is not satisfied or waived on any scheduled expiration date of the Offer, Acquisition Sub shall extend the Offer from time to time until such conditions are satisfied or waived; PROVIDED that (i) each such extension of the Offer shall be for a period of not more than ten Business Days, and (ii) Acquisition Sub shall not, without Without the prior written consent of the Company, Purchaser shall not extend the expiration date of the Offer beyond the Termination Date. Subject to the foregoing and upon the terms and subject to the conditions initial expiration date of the Offer, Acquisition Sub shall accept for payment except (x) as required by applicable law including applicable rules and pay forregulations of the SEC or any interpretation or position of the SEC staff, as promptly as practicable after (y) that if, immediately prior to the expiration date of the OfferOffer (as it may be extended), all the Shares validly tendered and not withdrawn pursuant to the Offer constitute less than 90% of the outstanding Shares, Purchaser may, in its sole discretion, extend the Offer for one or more periods not to exceed an aggregate of ten business days, notwithstanding that all conditions to the Offer are satisfied as of such expiration date of the Offer; provided that after the initial expiration date, the Offer shall not be subject to any conditions that are at the time of such extension satisfied other than the Minimum Condition and the conditions set forth in paragraph (including a) of Annex I, or (z) that if no Shares are validly tendered and any condition to the Offer has ------- not withdrawn)been satisfied or waived, Purchaser shall extend the expiration date of the Offer for one or more periods, but not in excess no event later than the Outside Date. In addition, the Offer Price may be increased and the Offer may be extended to the extent required by law in connection with such increase without the consent of the Maximum NumberCompany. (bc) The Offer shall be made by means of an offer to purchase (the "Offer ----- to Purchase") subject only to the conditions set forth in Annex I. As soon as ----------- ------- reasonably practicable on the date of commencement of the OfferOffer is commenced, BMS Parent and Acquisition Sub Purchaser shall file with the SEC a Tender Offer Statement on Schedule TO (together with all amendments and supplements thereto, the "SCHEDULE Schedule TO") with respect to the ----------- Offer that (such Schedule TO i) will comply in all material respects with the provisions of all applicable federal securities laws and such documents included therein pursuant to which (ii) will contain (including as an exhibit) or incorporate by reference the Offer will be madeto Purchase, a form of the related letter of transmittal and a summary advertisement (which documents, together with any supplements or amendments thereto, are referred to collectively herein as the "OFFER DOCUMENTSOffer Documents"). BMSEach of the Company, Acquisition Sub on the one --------------- hand, and Parent and Purchaser, on the Company each other hand, agrees promptly to correct any information provided by it in writing for use in the Schedule TO or the Offer Documents if and to the extent that such information the Schedule TO or the Offer Documents shall be, or have become become, false or misleading in any material respect. BMS , and Acquisition Sub Parent and Purchaser further agree to take all steps necessary to cause the Schedule TO TO, as so corrected corrected, to be filed with the SEC. BMS SEC and Acquisition Sub shall deliver or cause to be delivered to the Company, or such other Person as the Company shall designate, the Offer Documents (and any amendments thereto) Documents, as so corrected, in such quantities as shall be necessary for dissemination to all holders of Shares and Company Options. The Company shall, at its expense, cause the Offer Documents (and any amendments thereto) to be disseminated to holders of Shares and any other holder of securities issued by the Company Options(if any), in each case as and to the extent required by applicable federal securities laws. The Company Parent and its counsel shall be given an opportunity to review and comment on the Offer Documents prior to their being filed with the SEC or disseminated to the holders of Shares and Company Options. BMS and Acquisition Sub Purchaser shall provide the Company and its counsel with a reasonable opportunity to review and comment on the Schedule TO and any Offer Documents before they are filed with the SEC. Parent and Purchaser shall promptly provide the Company and its counsel in writing with, and consult with the Company and its counsel regarding, any comments Parent, Purchaser or other communications, whether written or oral, that BMS, Acquisition Sub or its their counsel may receive from time to time from the SEC or its staff with respect to the Offer Documents promptly after receipt of such comments Schedule TO or other communications. (c) Each certificate for Shares issued to Acquisition Sub representing Shares accepted for purchase and paid for by Acquisition Sub in the Offer shall bear a legend in substantially the following form: THE SECURITIES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO RESTRICTIONS ON TRANSFER AS SET FORTH IN THE STOCKHOLDER AGREEMENT, DATED SEPTEMBER 19, 2001, AMONG IMCLONE SYSTEMS INCORPORATED, ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB COMPANY AND ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB BIOLOGICS COMPANY, A COPY OF WHICH MAY BE OBTAINED FROM THE CORPORATE SECRETARY OF IMCLONE SYSTEMS INCORPORATEDDocuments.

The Offer. (a) As (i) Provided that this Agreement has not been terminated in accordance with ARTICLE VIII hereto, Purchaser will, and Parent will cause Purchaser to, promptly as practicable after the date hereof, (but in no event later than ten the tenth (10th) Business Days Day after (but not including) the date hereof, Acquisition Sub shall commence an offer (the "OFFER") to purchase for cash 14,392,003 Shares (which shall include, for purposes of this Agreement) commence (within the meaning of Rule 14d-2 under the Securities Exchange Act of 1934, as amended (the “Exchange Act”)) the Offer to purchase all Shares at the Offer Price; provided, however, that Purchaser shall not be required to commence the Offer (and the ten (10) Business Day period referred to above shall be accordingly extended) if (i) the Company shall not have provided to Parent on a timely basis all Shares issuable information reasonably requested by Parent in respect connection with the preparation of exercisablethe Offer Documents or the Company shall not have reviewed and provided comments to Parent on the Offer Documents on a timely basis, in-the-money Company Options which have been "conditionally exercised" by the holder thereof for purposes of participating in the Offer, and or (ii) all the Company is not prepared to, concurrently with such commencement, file with the SEC and disseminate to holders of Shares issued prior to the expiration of the Offer upon the conversion of any convertible securities or upon the exercise of any options or warrants) (such number of Shares, the "MAXIMUM NUMBER") at a price of $70.00 per Share, net to the seller in cash (such price, as may hereafter be increased, the "OFFER PRICE")Schedule 14D-9. The obligation obligations of Acquisition Sub Purchaser (and of Parent to cause Purchaser) to accept for payment and to pay for any Shares tendered pursuant to the Offer shall will be subject only to the satisfaction or waiver of those conditions set forth in Annex ANNEX I hereto(the “Offer Conditions”). The initial expiration date of the Offer shall will be the twentieth (20th) Business Day following (and including the day of) the commencement of the Offer (determined under Rule 14d-1(g)(3) promulgated under the 1934 Act)Offer. Acquisition Sub Purchaser expressly reserves the right (but will not be obligated) at any time or from time to time in its sole discretion to waive any of the conditions to the Offer, Offer Condition or modify or amend the terms of the Offer, and increase the Offer Price; PROVIDED except that, without the consent of the Company, Acquisition Sub shall not (i) increase or reduce the Maximum Number, (ii) reduce the price per Share to be paid pursuant to the Offer, (iii) add to the conditions set forth in Annex I or modify any condition set forth in Annex I, (iv) change the form of consideration payable in the Offer, or (v) otherwise amend the Offer in any manner adverse to the holders of Shares. Acquisition Sub shall extend the Offer for any period required by any rule, regulation, interpretation or position of the SEC or the staff thereof applicable to the Offer or any period required by applicable law. If any of the conditions to the Offer is not satisfied or waived on any scheduled expiration date of the Offer, Acquisition Sub shall extend the Offer from time to time until such conditions are satisfied or waived; PROVIDED that (i) each such extension of the Offer shall be for a period of not more than ten Business Days, and (ii) Acquisition Sub shall not, without the prior written consent of the Company, extend Purchaser will not (1) decrease the Offer beyond Price or change the Termination Date. Subject form of the consideration payable in the Offer, (2) decrease the number of Shares sought pursuant to the foregoing and upon Offer, (3) amend or waive the terms and subject Minimum Tender Condition (as defined in ANNEX I), (4) add to the conditions of set forth on ANNEX I, (5) modify the Offer, Acquisition Sub shall accept for payment and pay for, as promptly as practicable after the expiration of the Offer, all Shares validly tendered and not withdrawn (including if no Shares are validly tendered and not withdrawn), but not conditions set forth on ANNEX I in excess of the Maximum Number. (b) As soon as practicable on the date of commencement of the Offer, BMS and Acquisition Sub shall file with the SEC a Tender Offer Statement on Schedule TO (the "SCHEDULE TO") with respect to the Offer (such Schedule TO and such documents included therein pursuant to which the Offer will be made, together with any supplements or amendments thereto, the "OFFER DOCUMENTS"). BMS, Acquisition Sub and the Company each agrees promptly to correct any information provided by it for use in the Offer Documents if and to the extent that such information shall have become false or misleading in any material respect. BMS and Acquisition Sub agree to take all steps necessary to cause the Schedule TO as so corrected to be filed with the SEC. BMS and Acquisition Sub shall deliver or cause to be delivered to the Company, or such other Person as the Company shall designate, the Offer Documents (and any amendments thereto) as so corrected, in such quantities as shall be necessary for dissemination to all holders of Shares and Company Options. The Company shall, at its expense, cause the Offer Documents (and any amendments thereto) to be disseminated to holders of Shares and Company Options, in each case as and to the extent required by applicable federal securities laws. The Company and its counsel shall be given an opportunity to review and comment on the Offer Documents prior to their being filed with the SEC or disseminated manner adverse to the holders of Shares and Company Options. BMS and Acquisition Sub shall provide Shares, (6) extend the Company and its counsel with expiration date of the Offer except as required or permitted by Section 1.1(a)(iii) or (7) make any comments other change in the terms or other communications, whether written or oral, conditions of the Offer that BMS, Acquisition Sub or its counsel may receive from time to time from the SEC or its staff with respect is materially adverse to the Offer Documents promptly after receipt holders of such comments or other communicationsShares. (c) Each certificate for Shares issued to Acquisition Sub representing Shares accepted for purchase and paid for by Acquisition Sub in the Offer shall bear a legend in substantially the following form: THE SECURITIES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO RESTRICTIONS ON TRANSFER AS SET FORTH IN THE STOCKHOLDER AGREEMENT, DATED SEPTEMBER 19, 2001, AMONG IMCLONE SYSTEMS INCORPORATED, ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB COMPANY AND ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB BIOLOGICS COMPANY, A COPY OF WHICH MAY BE OBTAINED FROM THE CORPORATE SECRETARY OF IMCLONE SYSTEMS INCORPORATED.

The Offer. (a) As Provided that (i) this Agreement shall not have been terminated in accordance with Article VIII hereof, (ii) nothing shall have occurred that would render any of the conditions set forth in Section 1 of Annex B incapable of being satisfied and (iii) none of the conditions set forth in Section 2 of Annex B hereto shall have occurred and be continuing, Parent shall cause Purchaser (and the Company shall cooperate with Parent and Purchaser subject to Section 6.02(e)) to commence (within the meaning of Rule 14d-2 of the Exchange Act), as promptly as reasonably practicable after the date hereof, of this Agreement but in no event later more than ten (10) Business Days after the date hereofthereafter, Acquisition Sub shall commence an offer to purchase all outstanding shares of Company Common Stock (including the associated rights to purchase shares of capital stock of the Company (“Rights”) issued pursuant to that certain Shareholder Rights Plan dated as of December 23, 2006, by and between the Company and W▇▇▇▇ Fargo Bank, National Association, as Rights Agent (the "OFFER") to purchase for cash 14,392,003 Shares (which shall include, for purposes of this Agreement, (i) all Shares issuable in respect of exercisable, in-the-money Company Options which have been "conditionally exercised" by the holder thereof for purposes of participating in the Offer, and (ii) all Shares issued prior to the expiration of the Offer upon the conversion of any convertible securities or upon the exercise of any options or warrants“Rights Plan”)) (each such number share of Company Common Stock, together with the associated Rights, a “Share” and collectively, “Shares, the "MAXIMUM NUMBER"”) at a price of $70.00 19.50 per Share, net to the seller sellers in cash (such priceamount, as may hereafter be increasedor any greater amount per Share paid pursuant to the Offer, the "OFFER PRICE"“Offer Price”). The obligation Promptly after the later of: (i) the earliest date as of Acquisition Sub which Parent is permitted under applicable Law to accept for payment any Shares tendered pursuant to the Offer and (ii) the earliest date as of which each of the Tender Offer Conditions shall have been satisfied or waived (and in any event in compliance with Rule 14e-1(c)), Purchaser shall, and Parent shall cause it to, accept for payment, and pay for (after giving effect to any required withholding Tax), all Shares validly tendered pursuant to the Offer and not withdrawn (the time and date of acceptance for payment, the “Acceptance Date”). (b) Purchaser expressly reserves the right, in its sole discretion, to waive, in whole or in part, any Tender Offer Condition or modify the terms of the Offer; provided, however, that without the prior written consent of the Company, Purchaser shall not (i) decrease the Offer Price, (ii) decrease the number of Shares sought to be subject only purchased in the Offer, (iii) change the form of consideration payable in the Offer (other than by increasing the Offer Price, in the sole discretion of Purchaser), (iv) add to the Tender Offer Conditions, (v) waive or amend the Minimum Condition (as defined in Annex B), (vi) extend or otherwise change the expiration date of the Offer, other than in accordance with Section 1.01(c) or (vii) make any other change in the terms or conditions of the Offer which is or would reasonably be expected to be materially adverse to any holder of Shares, it being agreed that a waiver by Purchaser of any of the conditions set forth in Annex I hereto. B (other than the Minimum Condition) in whole or in part at any time and from time to time in its discretion shall not be deemed to be materially adverse to any holder of Shares. (c) The initial expiration date of the Offer (the “Expiration Date”) shall be the twentieth 20th Business Day following the commencement of the Offer (determined under using Rule 14d-1(g)(3) promulgated 14d-2 under the 1934 Exchange Act). Acquisition Sub expressly reserves Without the right to waive prior written consent of the Company, Purchaser may extend the Expiration Date (which extended date shall thereupon be the Expiration Date for purposes of this Agreement) in increments of not more than ten (10) Business Days each, if at the scheduled Expiration Date any of the conditions to Purchaser’s obligation to purchase Shares are not satisfied, until such time as such conditions are satisfied or waived, provided that the Expiration Date shall not be later than the Outside Date as a result of such extension. Without limiting the right of Purchaser to extend the Offer, modify the terms of the Offer, and increase the Offer Price; PROVIDED that, without the consent of the Company, Acquisition Sub provided that this Agreement shall not (i) increase or reduce the Maximum Numberhave been terminated in accordance with Article VIII hereof, (ii1) reduce the price per Share to be paid pursuant to the Offer, (iii) add to the conditions set forth in Annex I or modify any condition set forth in Annex I, (iv) change the form of consideration payable in the Offer, or (v) otherwise amend the Offer in any manner adverse to the holders of Shares. Acquisition Sub Purchaser shall extend the Offer Expiration Date for any period required by any rule, regulation, interpretation or position of the SEC or the staff thereof applicable to the Offer or and (2) Purchaser shall extend the Expiration Date if the conditions set forth in clauses (ii) and (iii) of Section 1 of Annex B are not satisfied as of any period required by applicable lawscheduled Expiration Date, until such time as the conditions set forth in clauses (ii) and (iii) of Section 1 of Annex B are satisfied, provided that the Expiration Date shall not be later than the Outside Date as a result of such extension. If Further, provided that this Agreement shall not have been terminated in accordance with Article VIII hereof, if any of the conditions set forth in Annex B (other than the conditions set forth in clauses (ii) and (iii) of Section 1 of Annex B) are not satisfied as of any scheduled Expiration Date, then, except to the extent that such conditions are incapable of being satisfied, at the request of the Company, Purchaser shall extend the Expiration Date for a period requested by the Company of not more than ten (10) Business Days in order to permit the satisfaction of such conditions to the Offer; provided, however, that Purchaser shall not be required to so extend the Expiration Date pursuant to this sentence on more than two occasions or if the failure to meet any of such conditions set forth in Annex B was caused by or resulted from the failure of the Company to perform in any material respect any covenant or agreement of the Company contained herein, or the material breach by the Company of any representation or warranty contained herein. In addition, Purchaser shall have the right, without the consent of the Company, to make available a subsequent offering period (within the meaning of Rule 14d-11 under the Exchange Act) if, on the then-applicable Expiration Date, the conditions to the Offer is not set forth in Annex B have been satisfied or waived on any scheduled expiration date but there shall not have been tendered that number of Shares which would equal at least ninety percent (90%) of the Offer, Acquisition Sub shall extend the Offer from time to time until such conditions are satisfied issued and then outstanding Shares on a “fully diluted basis” (which assumes conversion or waived; PROVIDED that (i) each such extension exercise of all derivative securities regardless of the Offer shall be for a period of not more than ten Business Daysconversion or exercise price, the vesting schedule or other terms and (ii) Acquisition Sub shall not, without the prior written consent of the Company, extend the Offer beyond the Termination Dateconditions thereof). Subject to the foregoing and upon the terms and subject to the conditions of set forth in the Offer, Acquisition Sub Purchaser shall, and Parent shall cause it to, accept for payment and pay for, as promptly as practicable after the expiration of the Offer, for all Shares validly tendered and not withdrawn (including if no during such subsequent offering period promptly after any such Shares are validly tendered during such subsequent offering period and not withdrawnin any event in compliance with Rule 14d-11 and Rule 14e-1(c) promulgated under the Exchange Act. The Offer may be terminated prior to its Expiration Date (as such expiration date may be extended and re-extended in accordance with this Agreement), but not only if this Agreement is validly terminated in excess of accordance with Section 8.01. In no event shall Purchaser extend the Maximum NumberOffer beyond the Outside Date. (bd) As soon as practicable on On the date of commencement of the Offer, BMS Parent and Acquisition Sub Purchaser shall (i) file or cause to be filed with the SEC a Tender Offer Statement on Schedule TO (together with all amendments and supplements thereto, the "SCHEDULE “Schedule TO"”) with respect to the Offer (such Schedule TO which shall contain the offer to purchase and such related letter of transmittal and summary advertisement and other ancillary documents included therein and instruments required thereby pursuant to which the Offer will be made, together made (collectively with any supplements or amendments thereto, the "OFFER DOCUMENTS"“Offer Documents”). BMS, Acquisition Sub and the Company each agrees promptly to correct any information provided by it for use in the Offer Documents if and to the extent that such information shall have become false or misleading in any material respect. BMS and Acquisition Sub agree to take all steps necessary to cause the Schedule TO as so corrected to be filed with the SEC. BMS and Acquisition Sub shall deliver or cause to be delivered to the Company, or such other Person as the Company shall designate, the Offer Documents ; (and any amendments theretoii) as so corrected, in such quantities as shall be necessary for dissemination to all holders of Shares and Company Options. The Company shall, at its expense, cause the Offer Documents (and any amendments thereto) to be disseminated to holders of Shares as required by applicable Law; and (iii) timely file with the Commissioner of Commerce of the State of Minnesota any registration statement relating to the Offer required to be filed pursuant to Chapter 80B of the Minnesota Statutes and shall disseminate to the holders of Company Options, Common Stock via the Offer Documents the information set forth in each case as and any such registration statement to the extent and within the time period required by applicable federal securities lawsChapter 80B of the Minnesota Statutes. The Company and its counsel shall be given an a reasonable opportunity to review and comment on the Offer Documents prior to their being filing with the SEC and Parent and Purchaser shall give reasonable and good faith consideration to any comments made by the Company and its counsel. (e) Parent and Purchaser shall cause the Offer Documents and any amendments or supplements thereto to (i) comply in all material respects with the Exchange Act, and (ii) not contain any untrue statement of a material fact or omit to state any material fact required to be stated therein or necessary in order to make the statements therein, in light of the circumstances under which they were made, not misleading, except that no covenant is made by Parent with respect to information supplied by the Company specifically for inclusion in the Offer Documents. Parent and Purchaser shall cause the information supplied by Parent and its affiliates specifically for inclusion in the Schedule 14D-9, the Information Statement or the Proxy Statement, at the respective times the Schedule 14D-9, the Information Statement or the Proxy Statement are filed with the SEC or, in the case of the Proxy Statement, at the time of the Special Meeting, not to contain any untrue statement of a material fact or omit to state any material fact required to be stated therein or necessary in order to make the statements therein, in light of the circumstances under which they were made, not misleading. Parent and Purchaser shall cause the Offer to be conducted in compliance in all material respects with the Exchange Act. (f) If at any time prior to the Effective Time, any information relating to the Offer, the Merger, the Company, Parent, Purchaser or any of their respective Affiliates, directors or officers, should be discovered by the Company or Purchaser which should be set forth in an amendment or supplement to the Offer Documents so that the Offer Documents shall not contain any untrue statement of a material fact or omit to state any material fact required to be stated therein or necessary in order to make the statements therein, in light of the circumstances under which they are made, not misleading, the party which discovers such information shall promptly notify the other parties, and an appropriate amendment or supplement describing such information shall be filed with the SEC and disseminated to the holders Company Shareholders, as and to the extent required by applicable Law or any applicable rule or regulation of Shares any stock exchange. Parent and Company Options. BMS and Acquisition Sub shall Purchaser agree to provide the Company and its counsel with (i) any comments or other communications, whether written or oral, that BMS, Acquisition Sub or its counsel may receive from time to time be received from the SEC or its staff with respect to the Offer Documents promptly after receipt of such thereof and prior to responding thereto and (ii) a reasonable opportunity to provide comments or other communicationson that response (to which reasonable and good faith consideration shall be given). (cg) Each certificate for Purchaser shall be entitled to deduct and withhold from the consideration otherwise payable pursuant to the Offer to any holder of Shares issued such amounts as Purchaser is required to Acquisition Sub representing Shares accepted for purchase deduct and withhold with respect to the making of such payment under the Code, or any provision of state, local or foreign Tax Law. To the extent that amounts are so withheld and paid over to the appropriate Taxing authority by Purchaser, such withheld amounts shall be treated for all purposes of this Agreement as having been paid to the holder of the Shares in respect of which such deduction and withholding was made by Acquisition Sub in Purchaser. (h) Parent shall cause to be provided to Purchaser all of the Offer funds necessary to purchase any Shares that Purchaser becomes obligated to purchase pursuant to the Offer, and shall bear cause Purchaser to perform, on a legend in substantially the following form: THE SECURITIES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO RESTRICTIONS ON TRANSFER AS SET FORTH IN THE STOCKHOLDER AGREEMENTtimely basis, DATED SEPTEMBER 19, 2001, AMONG IMCLONE SYSTEMS INCORPORATED, ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB COMPANY AND ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB BIOLOGICS COMPANY, A COPY OF WHICH MAY BE OBTAINED FROM THE CORPORATE SECRETARY OF IMCLONE SYSTEMS INCORPORATEDall of Purchaser’s obligations under this Agreement.

The Offer. (a) As Provided that this Agreement shall not have been terminated in accordance with Section 7.1, as promptly as practicable (and in any event within 10 business days) after the date hereofof this Agreement, but in no event later than ten Business Days after Purchaser shall (and Parent shall cause Purchaser to) commence (within the date hereofmeaning of Rule 14d-2 under the Securities Exchange Act of 1934, Acquisition Sub shall commence an offer as amended (the "OFFER"“Exchange Act”)) the Offer to purchase for cash 14,392,003 all Shares at the Offer Price. (which shall include, for purposes b) Subject to the terms and conditions of this Agreement, (i) all Shares issuable in respect including the prior satisfaction or waiver of exercisable, in-the-money Company Options which have been "conditionally exercised" by the holder thereof for purposes of participating in the Offer, and (ii) all Shares issued prior to the expiration of the Offer upon the conversion of any convertible securities or upon the exercise of any options or warrants) (such number of Shares, the "MAXIMUM NUMBER") at a price of $70.00 per Share, net to the seller in cash (such price, as may hereafter be increased, the "OFFER PRICE"). The obligation of Acquisition Sub to accept for payment any Shares tendered pursuant to the Offer shall be subject only to the conditions set forth in Annex I hereto. The initial expiration date (the “Offer Conditions”), promptly after the latest of the Offer shall be the twentieth Business Day following the commencement of the Offer (determined under Rule 14d-1(g)(3) promulgated under the 1934 Act). Acquisition Sub expressly reserves the right to waive any of the conditions to the Offer, modify the terms of the Offer, and increase the Offer Price; PROVIDED that, without the consent of the Company, Acquisition Sub shall not (i) increase or reduce the Maximum Number, (ii) reduce the price per Share earliest date as of which Purchaser is permitted under applicable Law to be paid accept for payment Shares tendered pursuant to the Offer, (ii) the earliest date as of which each of the Offer Conditions has been satisfied, or waived by Parent or Purchaser, and (iii) add the Expiration Date, Purchaser shall (and Parent shall cause Purchaser to) consummate the Offer in accordance with its terms, accept for payment each Share validly tendered and not properly withdrawn pursuant to the Offer, and promptly following the acceptance of Shares for payment pursuant to the Offer, pay the Offer Price (without interest) for, each Share validly tendered and not properly withdrawn pursuant to the Offer. The obligation of Purchaser (and of Parent to cause Purchaser) to accept for payment, and pay the Offer Price (without interest) for, each Share validly tendered and not properly withdrawn pursuant to the Offer is subject to, and only to, the satisfaction, or waiver by Parent or Purchaser, of each of the Offer Conditions. (c) The Offer shall be made by means of an offer to purchase (the “Offer to Purchase”) that contains the terms set forth in this Agreement, the Minimum Condition (as defined in Annex I) and the other conditions set forth in Annex I or modify I. Purchaser expressly reserves the right to (x) increase the Offer Price and (y) waive any condition set forth Offer Condition and make any other changes in Annex Ithe terms and conditions of the Offer; provided, however, that unless otherwise provided by this Agreement, without the prior written consent of the Company, Purchaser shall not (i) decrease the Offer Price, (ivii) change the form of consideration payable in the Offer, (iii) decrease the maximum number of Shares sought to be purchased in the Offer, (iv) impose conditions or (v) otherwise amend requirements to the Offer in addition to the Offer Conditions or amend or modify any of the Offer Conditions in a manner adverse to that adversely affects, or reasonably could adversely affect, the holders of Shares. Acquisition Sub , (vi) change or waive the Minimum Condition, or (vii) extend or otherwise change the expiration date of the Offer in a manner other than as required or permitted by this Agreement. (d) Unless extended pursuant to and in accordance with the terms of this Agreement, the Offer shall expire at 5:00 p.m. (New York City time) on the date that is 21 business days (for this purpose calculated in accordance with Rule 14d-1(g)(3) under the Exchange Act) following the commencement (within the meaning of Rule 14d-2 under the Exchange Act) of the Offer (the “Initial Expiration Date”) or, in the event the Initial Expiration Date has been extended pursuant to and in accordance with this Agreement, the date to which the Offer has been so extended (the Initial Expiration Date, or such later date to which the Initial Expiration Date has been extended pursuant to and in accordance with this Agreement, is referred to as the “Expiration Date”). (e) The Offer shall be extended from time to time as follows: (i) If on or prior to any then scheduled Expiration Date, the only Offer Conditions that have not been satisfied, or waived by Parent or Purchaser if permitted hereunder, are the Minimum Condition, the HSR Condition (as defined in Annex I), and/or the Trading Suspension Condition (as defined in Annex I), then Purchaser shall (and Parent shall cause Purchaser to), at the request of the Company, extend the Offer for one or more successive periods of not more than 10 business days each in order to permit the satisfaction of such conditions, provided such extension of the Offer period does not extend past the earlier of (x) the termination of this Agreement pursuant to Section 7.1 and (y) the date, as applicable, that is (A) 120 days after commencement of the Offer (the “Initial Outside Date”), or (B) 210 days after commencement of the Offer in the event that the HSR Condition shall not have been satisfied, or waived by Parent or Purchaser if permitted hereunder, by the Initial Outside Date (the “Extended Outside Date”); (ii) Purchaser may, in its sole discretion, extend the Offer for one or more successive periods of not more than 10 business days each, if at any otherwise scheduled Expiration Date any of the Offer Conditions shall not have been satisfied, or waived by Parent or Purchaser if permitted hereunder, until the termination of this Agreement pursuant to Section 7.1; and (iii) Purchaser shall extend the Offer for any period or periods required by any applicable law, rule, regulation, interpretation or position of the SEC Securities and Exchange Commission (“SEC”) or its staff or The NASDAQ Stock Market LLC (the staff thereof applicable “NASDAQ”) or its staff, until the termination of this Agreement pursuant to Section 7.1. (f) Purchaser may, in its sole discretion, provide for one “subsequent offering period” (and one or more extensions thereof) in accordance with Rule 14d-11 under the Exchange Act. Additionally, in the event that more than 80% of the then outstanding Shares have been validly tendered and not properly withdrawn pursuant to the Offer or any period required by applicable law. If any following the Expiration Date, Purchaser shall (and Parent shall cause Purchaser to), at the request of the Company, provide for one “subsequent offering period” in accordance with Rule 14d-11 under the Exchange Act of at least 10 business days immediately following the Expiration Date unless (i) Parent and Purchaser exercise the Top-Up Option or (ii) Parent, Purchaser and their respective Subsidiaries, in the aggregate, own more than 90% of the outstanding Shares. Subject to the terms and conditions of this Agreement and the Offer, Purchaser shall (and Parent shall cause Purchaser to) accept for payment, and pay the Offer Price (without interest) for, each Share that is validly tendered pursuant to the Offer during such “subsequent offering period” promptly after each such Share is tendered during such “subsequent offering period.” The Offer Documents will provide for the possibility of a “subsequent offering period” in a manner consistent with the terms of this Section 1.1(f). (g) Purchaser shall not satisfied or waived on terminate the Offer prior to any scheduled expiration date of the Offer, Acquisition Sub shall extend the Offer from time to time until such conditions are satisfied or waived; PROVIDED that (i) each such extension of the Offer shall be for a period of not more than ten Business Days, and (ii) Acquisition Sub shall not, Expiration Date without the prior written consent of the Company, extend Company except in the Offer beyond the Termination Date. Subject event that this Agreement is terminated pursuant to the foregoing and upon the terms and subject to the conditions of the Offer, Acquisition Sub shall accept for payment and pay for, as promptly as practicable after the expiration of the Offer, all Shares validly tendered and not withdrawn (including if no Shares are validly tendered and not withdrawn), but not in excess of the Maximum NumberSection 7.1. (bh) In the event that this Agreement is terminated pursuant to Section 7.1 prior to the Acceptance Time, Purchaser shall (and Parent shall cause Purchaser to) promptly (and in any event within 24 hours of such termination), irrevocably and unconditionally terminate the Offer and shall not acquire any Shares pursuant to the Offer. (i) As soon as practicable on after the date of commencement of the OfferOffer (within the meaning of Rule 14d-2 under the Exchange Act), BMS Parent and Acquisition Sub Purchaser shall file with the SEC SEC, pursuant to Rule 14d-3 and Regulation M-A under the Exchange Act (“Regulation M-A”), a Tender Offer Statement on Schedule TO (the "SCHEDULE TO") with respect to the Offer (such together with all amendments, supplements and exhibits thereto, the “Schedule TO”). The Schedule TO shall include, as exhibits, the Offer to Purchase, a form of letter of transmittal and such summary advertisement, and other ancillary documents included therein and instruments pursuant to which the Offer will be mademade (collectively, together with any amendments and supplements or thereto, and together with the Schedule TO and any amendments and supplements thereto, the "OFFER DOCUMENTS"“Offer Documents”). BMSThe Company will provide to Parent and Purchaser any information with respect to itself and its officers, Acquisition Sub directors and Affiliates required to be provided in the Offer Documents under applicable Laws or as reasonably requested by Parent and Purchaser. Parent and Purchaser agree to take all steps necessary to cause the Offer Documents to be filed with the SEC and disseminated to holders of Shares, in each case as and to the extent required by the Exchange Act. Parent and Purchaser, on the one hand, and the Company each agrees Company, on the other hand, agree to promptly to correct any information provided by it for use in the Offer Documents if and to the extent that such information it shall have become false or misleading in any material respectrespect or as otherwise required by applicable Law. BMS Parent and Acquisition Sub Purchaser further agree to take all steps necessary to cause the Schedule TO Offer Documents, as so corrected (if applicable), to be filed with the SEC. BMS SEC and Acquisition Sub shall deliver or cause to be delivered to the Company, or such other Person as the Company shall designate, the Offer Documents (and any amendments thereto) as so corrected, in such quantities as shall be necessary for dissemination to all holders of Shares and Company Options. The Company shall, at its expense, cause the Offer Documents (and any amendments thereto) to be disseminated to holders of Shares and Company OptionsShares, in each case as and to the extent required by applicable federal securities lawsthe Exchange Act. The Company and its counsel shall be given an a reasonable opportunity to review and comment on the Offer Documents prior to their being before they are filed with the SEC SEC, and Parent and Purchaser shall give due consideration to all the reasonable additions, deletions or disseminated to changes suggested thereto by the holders of Shares Company and Company Optionsits counsel. BMS In addition, Parent and Acquisition Sub Purchaser shall provide the Company and its counsel with copies of any comments or other communicationswritten comments, whether written or oraland shall inform them of any oral comments, that BMSParent, Acquisition Sub Purchaser or its their counsel may receive from time to time from the SEC or its staff with respect to the Offer Documents promptly after receipt of such comments, and any written or oral responses thereto. The Company and its counsel shall be given a reasonable opportunity to review any such written responses before they are submitted to the SEC or its staff, and Parent and Purchaser shall give due consideration to all reasonable additions, deletions or changes suggested thereto by the Company and its counsel. Parent and Purchaser shall respond promptly to any comments of the SEC or other communicationsits staff with respect to the Offer Documents. The Company hereby consents to the inclusion in the Offer Documents of the Company Board Recommendation, as such Company Board Recommendation may be amended and for so long as such Company Board Recommendation is not withdrawn (in each case as permitted by this Agreement). If the Offer is terminated or withdrawn by Purchaser, or this Agreement is terminated prior to the purchase of Shares in the Offer, Purchaser shall promptly return, and shall cause any depository, acting on behalf of Purchaser to return, all tendered Shares to the registered holders thereof. (cj) Each certificate The Offer Price shall be adjusted appropriately to reflect the effect of any stock split, reverse stock split, stock dividend (including any dividend or distribution of securities convertible into Common Stock), cash dividend, reorganization, recapitalization, reclassification, combination, exchange of shares or other like change with respect to Common Stock occurring on or after the date hereof and prior to Purchaser’s acceptance for payment of, and payment for, Shares issued pursuant to Acquisition Sub representing the Offer. (k) Parent shall cause to be provided to Purchaser all of the funds necessary to purchase any Shares accepted for that Purchaser becomes obligated to purchase pursuant to the Offer, and paid for by Acquisition Sub in the Offer shall bear cause Purchaser to perform, on a legend in substantially the following form: THE SECURITIES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO RESTRICTIONS ON TRANSFER AS SET FORTH IN THE STOCKHOLDER AGREEMENTtimely basis, DATED SEPTEMBER 19, 2001, AMONG IMCLONE SYSTEMS INCORPORATED, ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB COMPANY AND ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB BIOLOGICS COMPANY, A COPY OF WHICH MAY BE OBTAINED FROM THE CORPORATE SECRETARY OF IMCLONE SYSTEMS INCORPORATEDall of Purchaser’s obligations under this Agreement.

The Offer. (a) As Purchaser shall commence the Offer as promptly as reasonably practicable after the date hereof, but in no event later than ten Business Days after the date hereofDecember 5, Acquisition Sub shall commence an offer (the "OFFER") to purchase for cash 14,392,003 Shares (which shall include, for purposes of this Agreement, (i) all Shares issuable in respect of exercisable, in-the-money Company Options which have been "conditionally exercised" by the holder thereof for purposes of participating in the Offer, and (ii) all Shares issued prior to the expiration of the Offer upon the conversion of any convertible securities or upon the exercise of any options or warrants) (such number of Shares, the "MAXIMUM NUMBER") at a price of $70.00 per Share, net to the seller in cash (such price, as may hereafter be increased, the "OFFER PRICE")2003. The obligation of Acquisition Sub Purchaser to accept for payment any Common Shares tendered pursuant to the Offer shall be subject only to the conditions set forth in Annex I A hereto. The initial expiration date of the Offer shall be the twentieth Business Day following the commencement of the Offer (determined under Rule 14d-1(g)(3) promulgated under the 1934 Act). Acquisition Sub Purchaser expressly reserves the right to waive any of such condition, to increase the conditions to price per share payable in the Offer, modify to extend the offer to provide for "subsequent offering periods," as such term is defined in, and in accordance with, Rule 14d-11 under the Exchange Act and to make any other changes in the terms and conditions of the Offer; provided, and increase the Offer Price; PROVIDED however, that, without the prior written consent of the Company, Acquisition Sub Purchaser shall not (i) increase or reduce decrease the Maximum Numberprice per share payable in the Offer, (ii) reduce the price per Share maximum number of Common Shares to be paid pursuant to purchased in the Offer, (iii) add impose conditions to the conditions Offer in addition to those set forth in Annex I or modify any condition set forth in Annex IA hereto, (iv) change the form of consideration payable in the Offer, Offer or (v) otherwise amend amend, add to or waive any other term of the Offer in any manner that would be, in any significant respect, adverse to the holders of Shares. Acquisition Sub shall extend the Offer for any period required by any rule, regulation, interpretation or position of the SEC Company or the staff thereof Shareholders. The Per Share Amount shall, subject to applicable withholding of taxes, be net to the Offer or any period required seller in cash, and shall be reduced by applicable law. If any of the conditions per share distributions, if any, declared and payable by the Company to Shareholders from and after the Offer is not satisfied or waived on any scheduled date hereof until the expiration date of the Offer, Acquisition Sub shall extend the Offer from time to time until such conditions are satisfied or waived; PROVIDED that (i) each such extension of the Offer shall be for a period of not more than ten Business Days, and (ii) Acquisition Sub shall not, without the prior written consent of the Company, extend the Offer beyond the Termination Date. Subject to the foregoing and upon the terms and subject to the conditions of the Offer, Acquisition Sub shall accept for payment and pay for, as promptly as practicable after the . Upon expiration of the Offer, all Shares Purchaser shall, accept for payment shares validly tendered and not withdrawn (including if no Shares are validly tendered pursuant to the Offer and not withdrawn)pay for all such shares promptly following the acceptance of shares for payment in accordance with applicable Law and any rule, but not in excess regulation or interpretation of the Maximum NumberSecurities and Exchange Commission (the "SEC"). Notwithstanding the immediately preceding sentence and subject to the applicable rules of the SEC and the terms and conditions of the Offer, Purchaser expressly reserves the right to delay payment for shares to the extent required for compliance in whole or in part with applicable Laws. Any such delay shall be effected in compliance with Rule 14e-1(c) under the Securities Exchange Act of 1934, as amended (the "Exchange Act"). (ba) As soon promptly as reasonably practicable on the date of commencement of the Offer, BMS and Acquisition Sub Purchaser shall file with the SEC a Tender Offer Statement on Schedule TO (together with all amendments and supplements thereto, the "SCHEDULE Schedule TO") with respect to the Offer (such Offer. The Schedule TO shall contain or shall incorporate by reference an offer to purchase (the "Offer to Purchase") and forms of the related letter of transmittal and any related summary advertisement (the Schedule TO, the Offer to Purchase and such documents included therein pursuant to which the Offer will be madeother documents, together with any all supplements or and amendments thereto, being referred to herein collectively as the "OFFER DOCUMENTSOffer Documents"). BMS, Acquisition Sub Purchaser and the Company each agrees promptly agree to correct promptly any information provided by it any of them for use in the Offer Documents if and to the extent that such information shall have become false or misleading in any material respect. BMS misleading, and Acquisition Sub agree Purchaser further agrees to take all steps necessary to cause the Schedule TO TO, as so corrected corrected, to be filed with the SEC. BMS , and Acquisition Sub shall deliver or cause to be delivered to the Companyother Offer Documents, or such other Person as the Company shall designate, the Offer Documents (and any amendments thereto) as so corrected, in such quantities as shall be necessary for dissemination to all holders of Shares and Company Options. The Company shall, at its expense, cause the Offer Documents (and any amendments thereto) to be disseminated to holders of Shares and Company OptionsShareholders, in each case as and to the extent required by applicable federal securities laws. The Company and its counsel shall be given an opportunity to review and comment on the Offer Documents prior to their being filed with the SEC or disseminated to the holders of Shares and Company Options. BMS and Acquisition Sub shall provide the Company and its counsel with any comments or other communications, whether written or oral, that BMS, Acquisition Sub or its counsel may receive from time to time from the SEC or its staff with respect to the Offer Documents promptly after receipt of such comments or other communications. (c) Each certificate for Shares issued to Acquisition Sub representing Shares accepted for purchase and paid for by Acquisition Sub in the Offer shall bear a legend in substantially the following form: THE SECURITIES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO RESTRICTIONS ON TRANSFER AS SET FORTH IN THE STOCKHOLDER AGREEMENT, DATED SEPTEMBER 19, 2001, AMONG IMCLONE SYSTEMS INCORPORATED, ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB COMPANY AND ▇▇▇▇▇▇▇-▇▇▇▇▇ SQUIBB BIOLOGICS COMPANY, A COPY OF WHICH MAY BE OBTAINED FROM THE CORPORATE SECRETARY OF IMCLONE SYSTEMS INCORPORATED.