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ImmunoGen, Inc. Announces Encouraging Trastuzumab-DM1 Phase II Clinical Findings Presented at ASCO

WALTHAM, Mass. & ORLANDO, Fla.--(BUSINESS WIRE)--May 30, 2009 - ImmunoGen, Inc. (Nasdaq: IMGN), a biopharmaceutical company that develops targeted anticancer therapeutics, today announced the presentation of encouraging trastuzumab-DM1 (T-DM1) clinical data at the 2009 Annual Meeting of the American Society of Clinical Oncology (ASCO) taking place in Orlando, Florida.

T-DM1, an antibody-drug conjugate, consists of ImmunoGen's DM1 cancer-cell killing agent linked to the HER2-targeted antibody, trastuzumab, developed by Genentech, Inc. (a wholly-owned member of the Roche Group). Genentech (US) and Roche (ex-US) are conducting a broad clinical program with T-DM1 in HER2-positive breast cancer.

“These findings are particularly impressive because of the number of patients with advanced breast cancer who responded to treatment with T-DM1, the duration of their response, and the tolerability profile reported,” commented Daniel Junius, President and Chief Executive Officer. “We developed our Targeted Antibody Payload, or TAP, technology to achieve highly effective, well-tolerated cancer treatments, and are very encouraged by the results reported.”

Today's presentation, “A phase II study of trastuzumab-DM1 (T-DM1), a HER2 antibody-drug conjugate (ADC), in patients with HER2+ metastatic breast cancer (MBC): final results” (abstract #1017), features updated data from the first T-DM1 Phase II trial. This non-pivotal trial evaluated T-DM1 in patients with HER2-positive MBC that had progressed on a regimen containing trastuzumab (Herceptin®). Sixty percent of the 112 study patients also had been treated with a regimen containing lapatinib (Tykerb®).

Among the findings presented were:

  • 25 percent of patients had a confirmed objective response as assessed by an independent review facility (IRF), the primary endpoint of the study. Among these 28 patients, 22 were still receiving T-DM1 at the time of data cut-off for presentation;
  • 35 percent of patients had clinical benefit by IRF that consisted of either a confirmed objective response or stable disease lasting for at least 6 months; and
  • The anti-tumor activity seen in patients who had received lapatinib as well as trastuzumab was similar to that seen in the overall study population.

Among the 75 efficacy-evaluable patients who were verified to be HER2-positive by a central laboratory:

  • 32 percent had a confirmed objective response by IRF; and
  • 44 percent had clinical benefit by IRF consisting of either a confirmed objective response or stable disease lasting for at least 6 months.

The most common severe (Grade 3 or 4) adverse events were hypokalemia (lowered potassium levels) in 8 percent of patients and thrombocytopenia (lowered platelet levels) in 7 percent of patients. No severe (Grade 3 or 4) cardiac-specific toxicity was observed. One patient died during the study due to disease progression, unrelated to treatment with T-DM1.

In February 2009, Genentech and Roche initiated the global Phase III EMILIA study evaluating T-DM1 for second-line treatment of advanced HER2-positive breast cancer. Additionally, Genentech recently completed patient enrollment in a Phase II study evaluating T-DM1 for third-line treatment of advanced HER2-positive breast cancer. Genentech has stated that, if the data from this study are compelling, it will discuss an earlier approval path with the US Food and Drug Administration (FDA).

About ImmunoGen, Inc.

ImmunoGen, Inc. develops targeted anticancer therapeutics using its expertise in cancer biology, monoclonal antibodies and the creation and linkage of potent cancer-cell killing agents (CKAs) to such antibodies. The Company's proprietary TAP technology consists of ImmunoGen's highly potent CKAs, which have been designed specifically for delivery by antibodies to cancer cells, and the Company's engineered linkers, which direct the activation of the CKA inside a cancer cell. Compounds utilizing the TAP technology are in clinical testing through ImmunoGen's own programs and its 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.

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 products, including trastuzumab-DM1, by our collaborators, including risks related to uncertainties around clinical trials conducted and 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, 2008 and other reports filed with the Securities and Exchange Commission.

Herceptin® is a registered trademark of Genentech, Inc.

Tykerb® is a registered trademark of GlaxoSmithKline plc.

Contact: ImmunoGen, Inc.
Carol Hausner, 781-895-0600
Executive Director, Investor Relations
and Corporate Communications

Posted: June 2009