ImmunoGen, Inc. 9,000,000 Shares of Common Stock, par value $0.01 per share Underwriting AgreementImmunogen Inc • May 7th, 2010 • Pharmaceutical preparations • New York
ImmunoGen, Inc., a Massachusetts corporation (the “Company”), proposes to issue and sell to the several Underwriters listed in Schedule 1 hereto (the “Underwriters”), for whom you are acting as representative (the “Representative”), an aggregate of 9,000,000 shares of Common Stock, par value $0.01 per share, of the Company (the “Underwritten Shares”) and, at the option of the Underwriters, up to an additional 1,350,000 shares of Common Stock, par value $0.01 per share, of the Company (the “Option Shares”). The Underwritten Shares and the Option Shares are herein referred to as the “Shares”. The shares of Common Stock, par value $0.01 per share, of the Company to be outstanding after giving effect to the sale of the Shares are referred to herein as the “Stock”.
