ImmunoGen's IMGN901 Phase I trial data on multiple myeloma presented at ASCO 2011

ImmunoGen, Inc. (Nasdaq: IMGN), a biotechnology company that develops targeted antibody-based anticancer products using its antibody expertise and Targeted Antibody Payload (TAP) technology, today announced positive clinical data with the Company's IMGN901 (lorvotuzumab mertansine) product candidate as featured in an oral presentation (abstract #8013) at the ASCO 2011 Annual Meeting in Chicago. The data are from an ongoing Phase I trial assessing the compound used as part of a combination regimen for the treatment of multiple myeloma. IMGN901 is in development by ImmunoGen for the treatment of CD56-expressing cancers, which include small-cell lung cancer, multiple myeloma, Merkel cell carcinoma, and ovarian cancer.

The data reported today are from a trial designed to assess alternative doses of IMGN901 used in combination with lenalidomide (Revlimid®) and dexamethasone - a standard treatment regimen for multiple myeloma. Escalating doses of IMGN901, given weekly for three weeks in a 4-week cycle, were evaluated in combination with lenalidomide/dexamethasone at their usual doses in patients with relapsed or relapsed/refractory CD56-expressing multiple myeloma.

Among the sixteen patients enrolled at the time of data cutoff for presentation, all had previously been treated with corticosteroids (100%), and most had previously received bortezomib (94%), alkylating agents (75%), thalidomide (69%), lenalidomide (56%), and/or anthracyclines (56%). About two-thirds of the patients had received three or more prior regimens.

The findings reported for the thirteen efficacy-evaluable patients included:

• Over 60% (8/13) had an objective response to treatment: 39% had a very good partial response (VGPR), and 23% had a partial response (PR). VGPR is a category established by the International Myeloma Working Group for partial responses that have clinical outcomes comparable to complete responses.
• Among the six patients who previously had been treated with lenalidomide, one had a PR, one had a minimal response (MR), and three had stable disease.
• Half of the patients remained on therapy for at least five treatment cycles (approximately 5 months), including all of the patients who had VGPRs.
• Responses, including two of the VGPRs, were seen in patients with chromosomal mutations associated with a poor clinical outcome.

An IMGN901 dose of 75 mg/m²/week (225 mg/m² or 6.1 mg/kg over 3 weeks in a 4-week cycle) will be taken forward for further investigation in the expansion phase of the trial. At higher doses, peripheral neuropathy was reported with the treatment combination.

"This trial is the first to assess IMGN901 used in combination with standard care, an approach we're now also using in our small-cell lung cancer trial," said James O'Leary, Vice President and Chief Medical Officer. "The findings reported today are particularly impressive in light of the other therapies these patients have received. IMGN901 offers not only certain tolerability advantages, but also works by a different mechanism of action than standard multiple myeloma therapies."