ImmunoGen, Inc. Announces Favorable Update Provided by Roche Related to Its Trastuzumab-DM1 Regulatory Plans

ImmunoGen, Inc. (Nasdaq: IMGN), a biotechnology company that develops targeted anticancer products, today announced that Roche has provided a favorable update related to its plans to apply for marketing approval of trastuzumab-DM1 (T-DM1) in the US.

T-DM1 comprises ImmunoGen’s DM1 cancer-cell killing agent linked to the HER2-targeting antibody, trastuzumab, developed by Genentech, a wholly owned member of the Roche Group. T-DM1 is in global development by the Roche Group under a collaboration agreement between Genentech and ImmunoGen.

In its quarterly release issued earlier today, Roche disclosed that company representatives have had discussions with the US Food and Drug Administration (FDA) and that, based on these discussions, Genentech/Roche plans to submit a marketing application to the FDA in 2010 for use of T-DM1 in the treatment of advanced HER2-positive metastatic breast cancer. This is cancer that has progressed on multiple prior therapies including trastuzumab- and lapatinib-containing regimens for metastatic disease. The basis for this application is to be the positive Phase II data that were presented at the San Antonio Breast Cancer Symposium in December 2009.

“We’re pleased that Roche has provided this update and look forward to the submission of the US marketing application for T-DM1,” commented Daniel Junius, President and CEO.

About ImmunoGen’s Targeted Antibody Payload (TAP) Technology

The Company’s TAP technology uses antibodies to deliver one of ImmunoGen’s proprietary cancer-cell killing agents (e.g., DM1, DM4) specifically to tumors. ImmunoGen developed these agents specifically for targeted delivery to tumor cells. They are 1,000 – 10,000-fold more potent than standard chemotherapeutics and are designed to be attached to antibodies using one of the Company’s engineered linkers. In addition to T-DM1, five other compounds that make use of ImmunoGen’s TAP technology are in clinical testing.

About ImmunoGen, Inc.

ImmunoGen, Inc. develops targeted anticancer therapeutics using its expertise in cancer biology, monoclonal antibodies and the creation and attachment of potent cell-killing agents. The Company’s TAP technology uses antibodies to deliver one of ImmunoGen’s cancer-cell killing agents specifically to tumor targets. In addition to the Company’s product pipeline, compounds utilizing the TAP technology are in clinical testing through ImmunoGen’s collaborations with Genentech (a wholly owned member of the Roche Group), sanofi-aventis, Biogen Idec and Biotest. The most advanced compound, T-DM1, is in Phase III testing being conducted by Genentech and Roche. Other ImmunoGen collaborative partners include Bayer HealthCare and Amgen. More information about ImmunoGen can be found at www.immunogen.com.

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 T-DM1, including risks related to regulatory submissions and outcomes. A review of these risks can be found in ImmunoGen’s Annual Report on Form 10-K for the fiscal year ended June 30, 2009 and other reports filed with the Securities and Exchange Commission.