ImmunoGen, Inc. (Nasdaq: IMGN), a biotechnology company that develops novel anticancer therapeutics using its ADC technology, today announced the start of clinical testing with its EGFR-targeting ADC, IMGN289. “There is a lot of excitement around IMGN289,” commented Dr. Charles Morris, EVP and Chief Development Officer. “It is an antibody-drug conjugate, or ADC, to a well-known target, EGFR, and a potential new treatment for several types of cancers – including squamous cell lung and head and neck cancers – that have very limited treatment options today. We are delighted to now be gaining clinical experience with this promising new agent.” About the First-in-Human IMGN289 Clinical Trial IMGN289 will be evaluated in a multi-center, Phase I trial designed to assess the safety, tolerability, pharmacokinetics, pharmacodynamics and anticancer activity of the compound, administered weekly, in patients with non-small cell lung cancer (NSCLC), squamous cell carcinoma of the head and neck cancer (SCCHN), or other EGFR-positive solid tumors. Once its maximum tolerated dose is defined in the dose-finding part of the trial, the activity of IMGN289 will be evaluated in disease-specific patient cohorts. The ones planned currently include SCCHN, squamous cell NSCLC, and NSCLC resistant to EGFR inhibitors. About IMGN289 IMGN289, an ADC, is designed to bind to and kill cancer cells that highly express EGFR, also known as HER1. It contains an EGFR-targeting antibody developed by ImmunoGen with the Company’s potent cell-killing agent, DM1, attached using its thioether linker. This design is also used in the approved HER2-targeting product, Kadcyla ®. In preclinical testing, the antibody component of IMGN289 was found to be very active against EGFR-positive tumors responsive to EGFR inhibitors. The complete ADC – the antibody with ImmunoGen’s DM1 cell-killing agent attached – was even more active against such tumors and also was effective against EGFR-positive cancer cells not responsive to EGFR inhibition. 1-3 About NSCLC and SCCHN Approximately 194,000 people will be diagnosed with NSCLC in the US in 2013. 4 The most prevalent subtypes are adenocarcinoma (AC), squamous cell carcinoma (SCC), and large cell carcinoma (LCC), accounting for approximately 40%, 25-30%, and 10-15% of NSCLC diagnoses, respectively. 5 Research conducted at ImmunoGen found that approximately 20% of AC cases and about half of SCC and LCC cases strongly express EGFR. 2 More than 51,000 people will be diagnosed with SCCHN in the US in 2013. 4 Research conducted at ImmunoGen found that over 90% of SCCHN cases strongly express EGFR. 3 About ImmunoGen, Inc. ImmunoGen, Inc. develops targeted anticancer therapeutics. The Company’s ADC technology uses a tumor-targeting engineered antibody to deliver one of ImmunoGen's highly potent cancer-cell killing agents specifically to tumor cells. The most advanced compound with ImmunoGen’s ADC technology is Roche’s Kadcyla, which is marketed in the US by Genentech and is also gaining approvals internationally. Additional compounds are in clinical testing by ImmunoGen and the Company’s partnerships with Amgen, Bayer HealthCare, Biotest and Sanofi. More information about ImmunoGen can be found at www.immunogen.com. References 1Setiady et al., AACR 2013, abstract #5463 2Chittenden et al., AACR 2013, abstract #5467 3Ponte et al., AACR 2013, abstract #5483 4American Cancer Society (2013), Cancer Facts & Figures 5American Cancer Society (2013), Lung Cancer Detailed Guide Kadcyla ® is a registered trademark of Genentech, a member of the Roche Group. 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 IMGN289, 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, 2013 and other reports filed with the Securities and Exchange Commission.