Positive initial clinical data of IMGN901 used in combination regimen for multiple myeloma presented at ASH Annual Meeting

ImmunoGen, Inc.Dec 6 2010

ImmunoGen, Inc. (Nasdaq: IMGN), a biotechnology company that develops antibody-based anticancer products, today announced the presentation of positive initial clinical data with the Company's IMGN901 anticancer compound when used as part of a standard combination regimen to treat relapsed multiple myeloma. Encouraging updated data also were reported for the compound when used as monotherapy in patients with extensively pre-treated multiple myeloma. These findings were reported at the 52^nd ASH Annual Meeting and Exposition taking place in Orlando, Florida.

“We anticipate that inclusion of IMGN901 in this standard combination regimen will not only increase the number of objective responses achieved, but also extend their durability. When used alone, IMGN901 provided prolonged benefit for a number of patients with heavily pre-treated disease.”

ImmunoGen's IMGN901 product candidate is designed to target and kill cancer cells that express the CD56 antigen. The compound is wholly owned by the Company and is in development for the treatment of CD56-expressing tumors, including multiple myeloma.

"The early findings with IMGN901 used together with lenalidomide and dexamethasone indicate this combination therapy can rapidly achieve objective responses," commented James O'Leary, MD, Vice President and Chief Medical Officer. "We anticipate that inclusion of IMGN901 in this standard combination regimen will not only increase the number of objective responses achieved, but also extend their durability. When used alone, IMGN901 provided prolonged benefit for a number of patients with heavily pre-treated disease."

IMGN901 Used in a Combination Regimen

Positive initial findings were reported from a dose-finding portion of a Phase I trial (Study 005) in which increasing doses of IMGN901 are administered in combination with lenalidomide (Revlimid®) and dexamethasone given at their standard doses. All patients had multiple myeloma that had recurred after treatment with other therapies.

At the time of data cut-off for analysis, two dose cohorts (75 and 90 mg/m²) had completed patient enrollment. Evidence of activity was reported in 6 of the 7 patients treated:

• Two of the three patients receiving 75 mg/m² of IMGN901 had a very good partial response (VGPR). A VGPR is a new response category in multiple myeloma introduced as part of the International Myeloma Working Group Criteria. It was established to enable distinction of excellent objective responses that have outcomes similar to complete responses (CRs). These patients were in their sixth and seventh treatment cycles. The third patient received not only the study therapy, but also a lenalidomide-based regimen one month before starting combination treatment with IMGN901. This patient had progressive disease (PD).
• The four patients receiving 90 mg/m² were enrolled more recently than those receiving 75 mg/m², and thus the data for these patients were less mature. The first patient enrolled had a partial response (PR) and was in her third treatment cycle. Two other patients were in earlier stages of treatment, but had already achieved PRs by investigator assessment at the time of the data cut-off for presentation. The fourth patient has stable disease (SD). These patients all remain on study.

Enrollment was underway in a third dose cohort (112 mg/m²) at the time of data cut-off. The therapy has been well tolerated to date, and the maximum tolerated dose of IMGN901 in combination with lenalidomide and dexamethasone has not yet been defined.

IMGN901 Single Agent Therapy

Updated data also were reported from a trial (Study 003) assessing IMGN901 when used as a single agent in patients who had received multiple prior therapies for their disease. Among the 37 patients enrolled in either the dose-finding phase of the trial or its expansion phase, 6 had objective responses (2 partial responses and 4 minimal responses by EBMT criteria). Fifteen patients (41%) had durable clinical benefit (objective responses and/or stable disease for at least three months). Of note, nine patients were treated with IMGN901 for at least 20 weeks (5 months), including two patients who have been receiving the therapy for over one year. IMGN901 was found to be well tolerated, with no clinically significant myelosuppression.

Clinical Trial Information

In Study 005, new cohorts of patients receive increasing doses of IMGN901 to establish its maximum tolerated dose (MTD) when administered with lenalidomide (25 mg once daily for 21 days) and dexamethasone (40 mg weekly for four weeks). In this trial, IMGN901 is administered weekly for three weeks in a 4-week cycle. Once the MTD has been established, up to 40 patients are to be enrolled in the expansion phase of the trial.

In Study 003, IMGN901 is administered weekly for two weeks in a 3-week cycle. In the dose-escalation phase of this trial, the MTD of the compound was defined to be 112 mg/m². Nineteen study patients have received IMGN901 at its MTD.

IMGN901 is also in clinical testing for the treatment of CD56+ solid tumors, which include small-cell lung cancer, Merkel cell carcinoma, and ovarian cancer.