The primary endpoint of the NORTH trial is progression-free survival (PFS). Secondary endpoints include PFS at 6 months, overall survival at 12 months, time to progression, overall survival, and overall response rate.About IMGN901 IMGN901 was developed by ImmunoGen to target and kill CD56-positive cancer cells. CD56 is expressed on virtually all cases of SCLC. It is also expressed on a variety of other cancers including Merkel cell carcinoma and many cases of multiple myeloma. IMGN901 employs the Company’s Targeted Antibody Payload (TAP) technology, which uses a CD56-binding antibody to target one of ImmunoGen’s highly potent cell-killing agents to CD56-positive cancer cells. About SCLC It is estimated that approximately 29,400 new cases of SCLC will be diagnosed in the United States this year. 1 Approximately two-thirds of patients have extensive disease at the time of diagnosis, as SCLC tends to spread broadly through the body quite early in its course. 2 As a result, SCLC is usually treated with chemotherapy rather than with surgery. 3 Median PFS for extensive disease SCLC is approximately 5.5 months, while median overall survival averages 9-11 months. 3,4 About ImmunoGen, Inc. ImmunoGen, Inc. develops targeted anticancer therapeutics. The Company’s TAP technology uses a tumor-targeting monoclonal antibody to deliver one of ImmunoGen's highly potent cancer-killing agents specifically to tumor cells. Ten TAP compounds are now in clinical testing, of which three are wholly owned by the Company. Marketing applications for trastuzumab emtansine (T-DM1), the most advanced compound using ImmunoGen's TAP technology, are under review in the US, Europe and Japan. Roche is developing this compound globally under an agreement between ImmunoGen and Genentech, a member of the Roche Group. More information about ImmunoGen can be found at www.immunogen.com. 1 American Cancer Society, Cancer Facts & Figures 2012. 2 American Cancer Society, Lung Cancer (Small Cell) 2012. 3 National Comprehensive Cancer Network (NCCN) Guidelines. 4Foster, NR, Qi, Y, Krook, JE, et al. (2009). J Clin Oncol, 27(15s). This press release includes forward-looking statements. For these statements, ImmunoGen claims the protection of the safe harbor for forward-looking statements provided by the Private Securities Litigation Reform Act of 1995. It should be noted that there are risks and uncertainties related to the development of novel anticancer products, including IMGN901, including risks related to preclinical and clinical studies, their timings and results. A review of these risks can be found in ImmunoGen’s Annual Report on Form 10-K for the fiscal year ended June 30, 2012 and other reports filed with the Securities and Exchange Commission.