Pricing Information Provided Orally by Underwriters [set out key information included in script that will be used by Underwriters to confirm sales] [None.] , 2014 Leerink Partners LLC ▇▇▇▇▇ and Company, LLC As Representatives of the several Underwriters listed in Schedule 1 to the Underwriting Agreement referred to below c/o Leerink Partners LLC ▇▇▇ ▇▇▇▇ ▇▇▇▇▇▇, ▇▇▇▇ ▇▇▇▇▇ ▇▇▇ ▇▇▇▇, ▇▇ ▇▇▇▇▇ c/o Cowen and Company, LLC ▇▇▇ ▇▇▇▇▇▇▇▇▇ ▇▇▇▇▇▇, ▇▇▇▇ ▇▇▇▇▇ ▇▇▇ ▇▇▇▇, ▇▇ ▇▇▇▇▇ Ladies and Gentlemen: The undersigned understands that you, as Representatives of the several Underwriters, propose to enter into an Underwriting Agreement (the “Underwriting Agreement”) with Zafgen, Inc., a Delaware corporation (the “Company”), providing for the public offering (the “Public Offering”) by the several Underwriters named in Schedule 1 to the Underwriting Agreement (the “Underwriters”), of Common Stock, par value $0.001 per share, of the Company (the “Common Stock”). Capitalized terms used herein and not otherwise defined shall have the meanings set forth in the Underwriting Agreement. In consideration of the Underwriters’ agreement to purchase and make the Public Offering of the Common Stock, and for other good and valuable consideration receipt of which is hereby acknowledged, the undersigned hereby agrees that, without the prior written consent of Leerink Partners LLC and ▇▇▇▇▇ and Company, LLC on behalf of the Underwriters, the undersigned will not, during the period ending 180 days after the date of the prospectus relating to the Public Offering (the “Prospectus”), (1) offer, pledge, sell, contract to sell, sell any option or contract to purchase, purchase any option or contract to sell, grant any option, right or warrant to purchase, or otherwise transfer or dispose of, directly or indirectly, any shares of Common Stock or any securities convertible into or exercisable or exchangeable for Common Stock (including without limitation, Common Stock or such other securities which may be deemed to be beneficially owned by the undersigned in accordance with the rules and regulations of the Securities and Exchange Commission and securities which may be issued upon exercise of a stock option or warrant), or publicly disclose the intention to make any offer, sale, pledge or disposition, (2) enter into any swap or other agreement that transfers, in whole or in part, any of the economic consequences of ownership of the Common Stock or such other securities, whether any such transaction described in clause (1) or (2) above is to be settled by delivery of Common Stock or such other securities, in cash or otherwise or (3) make any demand for or exercise any right with respect to the registration of any shares of Common Stock or any security convertible into or exercisable or exchangeable for Common Stock. The foregoing restrictions shall not apply to: (A) sales of securities acquired in open market transactions after the date of the Public Offering; (B) transfers of securities (i) as a bona fide gift or gifts or (ii) by will or intestacy to the legal representative, heir, beneficiary or a member of the immediate family of the undersigned in a transaction not involving a disposition for value; (C) if the undersigned is an individual, transfers of shares of Common Stock or any security directly or indirectly convertible into Common Stock to any trust for the direct or indirect benefit of the undersigned or the immediate family of the undersigned, or limited partnerships the partners of which are the undersigned and/or the immediate family members of the undersigned, in each case for estate planning purposes; (D) if the undersigned is a trust, distributions of shares of Common Stock or any security directly or indirectly convertible into Common Stock to its beneficiaries in a transaction not involving a disposition for value; (E) if the undersigned is a corporation, limited liability company, partnership or other entity, distribution of shares of Common Stock or any security directly or indirectly convertible into Common Stock to members, stockholders, limited partners, subsidiaries or affiliates (as defined in Rule 405 promulgated under the Securities Act of 1933, as amended) of the undersigned or to any investment fund or other entity that controls or manages the undersigned in a transaction not involving a disposition for value; (F) the receipt by the undersigned of shares of Common Stock in connection with the conversion of the outstanding preferred stock of the Company into shares of Common Stock, provided that any such shares of Common Stock received upon such conversion shall be subject to the terms of this agreement (this “Letter Agreement”); (G) transfers to the Company pursuant to agreements under which the Company has the option to repurchase such shares or securities upon termination of service of the undersigned; (H) the receipt by the undersigned from the Company of shares of Common Stock upon the exercise of options, provided that any such shares of Common Stock received upon such exercise shall be subject to the terms of this Letter Agreement; or (I) the establishment of a trading plan that satisfies the requirements of Rule 10b5-1 under the Exchange Act for the transfer of shares of Common Stock, provided that there will be no transfer of shares of the undersigned’s Common Stock during the 180-day period referred to above and such a plan may only be established if no public announcement of the establishment or existence thereof and no filing with the Securities and Exchange Commission or other regulatory authority in respect thereof or transactions thereunder or contemplated thereby, by the undersigned, the Company or any other person, shall be required, and no such announcement or filing is made voluntarily, by the undersigned, the Company or any other person during the 180-day period;
