Findings from First Combination Trial Support Tolerability of Compounds Utilizing ImmunoGen’s TAP Technology

WALTHAM, MA, USA | June 5, 2010 | ImmunoGen, Inc. (Nasdaq: IMGN – News), a biopharmaceutical company that develops targeted anticancer therapeutics, today announced the presentation of clinical data from a Phase Ib/II trial conducted by Roche and Genentech to investigate the safety and preliminary efficacy of trastuzumab-DM1 (T-DM1) used in combination with Roche’s investigational antibody, pertuzumab. The findings were reported at the 2010 Annual Meeting of the American Society of Clinical Oncology (ASCO) being held in Chicago, IL (abstract #1012).

The data reported provide further support for the tolerability profile of compounds made with ImmunoGen’s Targeted Antibody Payload (TAP) technology. T-DM1 utilizes ImmunoGen’s TAP technology and is in global development by Roche.

“The tolerability seen with TAP compounds when used as single agents supports assessing them as part of combination regimens,” commented Daniel Junius, President and Chief Executive Officer. “In addition to assessment with pertuzumab, Roche has trials underway that assess – separately – T-DM1 in combination with two taxane compounds and another of its investigational agents, GDC-0941. Similarly, we’re assessing our lorvotuzumab mertansine TAP compound in combination with lenalidomide and dexamethasone, and we plan to start a second combination trial with this product candidate later this year. There’s been substantial growth in the number of clinical trials evaluating TAP compounds as single agents and in combination, and we expect this growth to continue to accelerate.”

Clinical Data Reported

The data reported today are from a Roche and Genentech Phase Ib/II trial assessing the combination of T-DM1 and pertuzumab in patients with HER2+ locally-advanced or metastatic breast cancer (MBC). Safety data were reported for the 44 patients enrolled who received the agents as a 2nd-line or later treatment for HER2+ MBC. Efficacy data were reported for the subset of these patients who had been on study at least 12 weeks or were off study at the time of the data cut-off for analysis.

The most common side effects reported – regardless of grade or relationship to study drugs – in the 44 relapsed patients were fatigue (52.3%), nausea (50.0%) and decreased appetite (36.4%). Two patients had grade 4 toxicity, both thrombocytopenia, resulting in dose reduction in one of these two patients. Preliminary efficacy data included an objective response rate (ORR) of 35.7% (10/28); stable disease was reported for 46.4% (13/28) patients, including two patients with unconfirmed responses.

The authors concluded that:

* The two agents have an encouraging safety profile when used together; and
* The preliminary efficacy of this combination is promising.

About T-DM1

T-DM1 comprises ImmunoGen’s DM1 cancer-cell killing agent attached to the HER2-targeting antibody, trastuzumab, developed by Genentech, a wholly owned member of the Roche Group, using ImmunoGen’s linker and methods of attachment. T-DM1 is in global development by Roche for the treatment of HER2+ MBC:

* For 3rd-line (and later) use – Roche plans to submit a marketing application to the FDA in 2010 based on the positive Phase II study reported at the San Antonio Breast Cancer Symposium in December 2009.
* For 2nd-line use – A Phase III trial (EMILIA) is underway that compares T-DM1 (used alone) to lapatinib plus capecitabine in patients whose HER2+ MBC was previously treated with trastuzumab and a taxane.
* For 1st-line use – Roche expects preliminary data to be reported at a medical meeting in October 2010 from a Phase II trial comparing T-DM1 (used alone) vs. trastuzumab plus docetaxel for newly diagnosed HER2+ MBC. A Phase III trial (MARIANNE) is scheduled to start in 2010 that compares T-DM1 (used alone) vs. trastuzumab plus a taxane for 1st-line use. This trial will also include a treatment arm comparing T-DM1 plus pertuzumab against the trastuzumab plus taxane treatment arm.

About this Clinical Trial

The Phase Ib/II trial (TDM4373g) reported today was designed to assess the safety and preliminary efficacy of T-DM1 used with pertuzumab and to establish the dose of T-DM1 to be used in further assessment of this combination. During the dose-escalation phase of the study, enrollment was limited to patients with relapsed disease. Target enrollment in its expansion phase was 20 newly diagnosed patients (1st-line use) and 40 relapsed patients (2nd-line or later use). At the time of data cut-off for analysis, 67 patients had been enrolled: 45 with relapsed disease and 22 with newly diagnosed HER2+ MBC. Only the findings in the relapsed patients were reported today (excluding one relapsed patient for whom safety data was unavailable).

About ImmunoGen’s Targeted Antibody Payload (TAP) Technology

The Company’s TAP technology uses manufactured antibodies to deliver one of ImmunoGen’s highly potent cancer-cell killing agents (e.g., DM1, DM4) specifically to tumors. The Company’s cancer-cell killing agents are many-fold more potent than standard chemotherapeutics and were developed by ImmunoGen scientists specifically for targeted delivery to tumors. ImmunoGen also has engineered linkage technology that keeps the cancer-cell killing agent attached to the antibody until it reaches the cancer cell and then controls the release of the agent inside the cell. 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 cancer-cell killing agents. The Company’s TAP technology uses antibodies to deliver one of ImmunoGen’s highly potent cancer-cell killing agents specifically to tumors. 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 Schering Pharma and Amgen. More information about ImmunoGen can be found at www.immunogen.com.

SOURCE: ImmunoGen, Inc.