ImmunoGen, Inc. Initiates Phase I Trial of IMGN853 in Ovarian Cancer and Other Solid Tumors Over-Expressing Its Folate Receptor Target

Folate receptor 1 (FOLR1)-targeting compound is second novel ImmunoGen product candidate to enter clinic this year

ImmunoGen, Inc. Initiates Phase I Trial of IMGN853 in Ovarian Cancer and Other Solid Tumors Over-Expressing Its Folate Receptor Target

<0> For Investors:ImmunoGen, Inc.Carol Hausner, 781-895-0600Executive Director, Investor Relations and Corporate CommunicationsorFor Media:The Yates NetworkBarbara Yates, 781-258-6153 </0>

(Nasdaq: IMGN), a biotechnology company that develops anticancer therapeutics using its antibody expertise and Targeted Antibody Payload (TAP) technology, today announced the start of clinical testing with its IMGN853 product candidate. The Phase I trial initiated evaluates the safety, tolerability, pharmacokinetics, pharmacodynamics and anticancer activity of this TAP compound in patients with ovarian cancer or other solid tumors that over-express FOLR1 (also known as folate receptor alpha), including non-small cell lung cancer (NSCLC). Once the maximum tolerated dose (MTD) of IMGN853 is established, the activity of the compound will be evaluated in disease-specific patient cohorts.

“This trial is expected to provide key information needed to define the registration path for IMGN853,” commented James O’Leary, MD, Vice President and Chief Medical Officer. “The study protocol allows for the use of single-patient cohorts for evaluation of the lower dose levels, which should accelerate the pace of advancement to higher doses and to the trial’s expansion phase. In the expansion phase, IMGN853 will be evaluated as a treatment for specific types of FOLR1-overexpressing tumors. These findings should enable us to make decisions needed to advance IMGN853 into later-stage clinical testing.”

This multi-center, first-in-human US Phase I trial is designed to enroll approximately 64 patients with previously treated ovarian cancer, NSCLC or other epithelial malignancies that over-express FOLR1. Once the MTD is defined in the dose-escalation part of the trial, three expansion cohorts will be opened to evaluate the pharmacodynamics and antitumor activity of IMGN853 at this MTD in patients with specific types of cancers:

More patients die from lung cancer in the US than from any other type of cancer: each year, approximately 226,000 patients in the US are diagnosed with lung cancer and approximately 160,000 die from the disease.About 40% of lung cancers are the adenocarcinoma subtype of NSCLC.

Each year, there are approximately 22,000 new cases of ovarian cancer diagnosed in the US and approximately 15,500 women die from the disease.EOC accounts for approximately 85% to 90% of all cases of ovarian cancer.

The novel agent IMGN853, a TAP compound, contains an ImmunoGen FOLR1-targeting antibody attached to the Company’s potent cell-killing agent, DM4. The antibody enables the compound to bind specifically to cancer cells expressing FOLR1, and the DM4 serves to kill these cells. The DM4 is attached to the antibody using one of ImmunoGen’s engineered linkers. The linker in IMGN853 serves not only to keep the DM4 stably attached to the antibody while the compound is in the bloodstream, but also – once at the tumor site – to counteract the multi-drug resistance that can make previously treated tumors more difficult to kill.

ImmunoGen, Inc. develops targeted anticancer therapeutics using the Company's expertise in tumor biology, monoclonal antibodies, potent cancer-cell killing agents and engineered linkers. The Company's TAP technology uses monoclonal antibodies to deliver one of ImmunoGen's proprietary cancer-cell killing agents specifically to tumor cells. There are now numerous TAP compounds in clinical development with a wealth of clinical data reported. ImmunoGen’s collaborative partners include Amgen, Bayer HealthCare Pharmaceuticals, Biotest, Lilly, Novartis, Roche, and Sanofi. The most advanced compound using ImmunoGen's TAP technology, trastuzumab emtansine (T-DM1), is in Phase III testing through the Company's collaboration with Genentech, a member of the Roche Group. More information about ImmunoGen can be found at .

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