ImmunoGen, Inc. Announces Submission of IND for Wholly Owned Product Candidate for Non-Hodgkin's Lymphoma

IMGN529 is the first IND-stage compound for non-Hodgkin's Lymphoma that provides both anticancer antibody activity and small molecule cancer-killing power

WALTHAM, Mass., Sep 22, 2011 -- ImmunoGen, Inc. IMGN +0.30% , a biotechnology company that develops targeted anticancer products using its antibody expertise and Targeted Antibody Payload (TAP) technology, today announced its submission of the Investigational New Drug (IND) application for its IMGN529 product candidate to the U.S. Food and Drug Administration (FDA).

IMGN529 is a potential new treatment for B-cell malignancies including non-Hodgkin's lymphoma (NHL) and chronic lymphocytic leukemia (CLL). Its unique design enables IMGN529 to kill cancerous B cells using multiple, targeted mechanisms. NHL is the most prevalent type of hematological, or "liquid", cancer and is often treated with a therapeutic antibody, Rituxan(R) (rituximab), plus chemotherapy.

IMGN529 contains an antibody that has notable anticancer activity of its own. This antibody demonstrated activity superior to that of Rituxan against human NHL and CLL cell lines in preclinical testing.1,2,3 Attached to this antibody is one of ImmunoGen's highly potent, proprietary cancer-cell killing agents, DM1. In addition to providing its own anticancer effects, the antibody in IMGN529 also serves to deliver DM1 specifically to B cells for targeted killing of the cancerous cells.

"We expect IMGN529 to be the first compound in the clinic for NHL that provides Rituxan-like antibody activity along with targeted cell-killing using a potent small molecule," commented Daniel Junius, President and CEO. "The design of IMGN529 takes advantage of the clinical finding that TAP compounds can be dosed at levels at which their antibody component can have anticancer activity."

About IMGN529

IMGN529 is a TAP compound in development by ImmunoGen for the treatment of B-cell malignancies, including NHL and CLL.

IMGN529 targets CD37, which is expressed at similar stages of the B-cell lineage as CD20, the target for Rituxan. CD37 is highly expressed in key NHL subtypes, such as follicular lymphoma, diffuse large B-cell lymphoma, marginal zone B-cell lymphoma and mantle cell lymphoma, as well as on CLL.1,3

IMGN529 contains a CD37-targeting antibody developed by ImmunoGen that was selected for its anticancer properties.1 The Company's potent DM1 cancer-cell killing agent is attached to this antibody using ImmunoGen's non-cleavable SMCC linker. The antibody serves to deliver the DM1 specifically to B cells to minimize damage to normal tissue. In IMGN529, the antibody also has anticancer activities of its own.

About ImmunoGen, Inc.

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 and a wealth of clinical data reported. ImmunoGen's collaborative partners include Amgen, Bayer HealthCare Pharmaceuticals, Biotest, 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 .

Rituxan(R) is a registered trademark of Biogen Idec.

1Park P. et al., AACR 2011, abstract #2830. 2Deckert J. et al., AACR 2011, abstract #4565. 3Mayo M. et al., AACR 2011, abstract #4581.

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 IMGN529, including risks related to regulatory review processes 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, 2011 and other reports filed with the Securities and Exchange Commission.