News

WALTHAM, Mass., Dec 06, 2009 (BUSINESS WIRE) -- ImmunoGen, Inc. (Nasdaq: IMGN), a biopharmaceutical company that develops targeted anticancer therapeutics, today reported encouraging clinical data with its IMGN901 product candidate in the treatment of relapsed and relapsed/refractory multiple myeloma (MM), including prolonged benefit in patients whose disease had progressed on multiple prior treatment regimens. These findings were reported at the American Society of Hematology (ASH) 51th Annual Meeting and Exposition being held in New Orleans, MA.

IMGN901 is an investigational agent designed to kill cancer cells that express CD56, a protein. It consists of a CD56-binding antibody with a potent cancer-cell killing agent, DM1, attached to it using an engineered linker. IMGN901 is in Phase I testing for the treatment of CD56-expressing solid tumors and multiple myeloma. It is wholly-owned by ImmunoGen.

In the trial reported today, new cohorts of patients received increasingly greater amounts of IMGN901 - used as a single agent - until the maximum tolerated dose was established. All of the patients had CD56-expressing MM that had progressed on multiple therapies, and most had previously been treated with at least six chemotherapy regimens.

"What was particularly impressive was the duration of benefit seen with IMGN901 in a number of these heavily pre-treated patients," commented Asher Chanan-Khan, MD, of the Roswell Park Cancer Institute. "IMGN901 demonstrated encouraging activity as a single agent in a disease often treated with combination therapy, and the tolerability findings to date support evaluating it used together with other active agents."

Among the twenty-six patients treated with IMGN901 at any dose level:

• One patient had a partial response (PR) while receiving IMGN901. This patient has continued on treatment for more than a year.
• Three patients had a minimal response (MR) while receiving IMGN901, and two of these patients remained on treatment for at least 45 weeks. The third patient withdrew from the study due to a broken leg while continuing to show disease improvement.
• Eleven patients had stable disease (SD), with eight of these patients remaining on treatment for at least 12 weeks at the time of data cut-off for presentation. These include four patients who have received IMGN901 for at least 24 weeks and two other patients still undergoing treatment.
• The overall clinical benefit rate (objective responses plus sustained stable disease) was 46%.

Ten patients remained on IMGN901 longer than on regimens received earlier in the course of their disease, and eight of these patients were on IMGN901 longer than on their last regimen with approved therapies. Typically in the treatment of cancer, patients have their best treatment responses early in the course of their disease and respond less well to later therapies.

IMGN901 was found to be generally well tolerated and was not associated with significant myelosuppression or other side effects that would limit its ability to be administered in combination with other active agents. The most common side effects were mild-to-moderate headache, fatigue and neuropathy. Grade 3 fatigue was reported in two patients and was the only grade 3 side effect reported in more than one patient; no more severe (grade 4 or 5) side effects were associated with use of the agent. The maximum tolerated dose was established to be 112 mg/m²/week.

"This trial - Study 003 - has provided us with important information on the safety of IMGN901 when used alone to treat multiple myeloma that has progressed on numerous prior therapies," noted James O'Leary, MD, Vice President and Chief Medical Officer of ImmunoGen. "The expansion phase of this trial, which is now underway, provides for patients with less heavily pretreated multiple myeloma to receive IMGN901 at the maximum tolerated dose, enabling us to better assess its activity when used as a single agent."

Dr. O'Leary continued, "Multiple myeloma is often treated with a combination of therapies with different mechanisms of action. Thus, we feel it's important to also assess IMGN901 as part of a multi-agent regimen. The profile of IMGN901 suggests that it's particularly well suited to use in combination, as it works by a novel mechanism and has not been associated with side effects that would limit its ability to be used with other agents. We expect patient dosing in our Study 005 combination trial to begin shortly."

About the Presentation

The poster, "Phase I Study of IMGN901, Used as Monotherapy, in Patients with Heavily Pre-Treated CD56-Positive Multiple Myeloma - A Preliminary Safety and Efficacy Analysis" is being presented at ASH between 6:00 - 8:00 pm (CT). Dr. Chanan-Khan is the lead investigator in the study.

About Study 003

This Phase I trial evaluates IMGN901 in patients with CD56+ multiple myeloma that has progressed on prior treatments (relapsed disease) and may no longer respond to these agents (refractory disease). In Study 003, IMGN901 is administered weekly for two consecutive weeks every three weeks (one treatment cycle). During the dose-escalation portion of the trial, no limit was placed on the number of prior therapies a patient may have received. In the expansion phase now underway, patients must have received at least one but no more than three prior treatment regimens to be eligible for enrollment. In this leg of the trial, progression-free survival and overall survival data will be captured as well as objective response information.

Other IMGN901 Studies

Study 005 is a Phase I trial designed to evaluate IMGN901 in CD56+ multiple myeloma when used in combination with lenalidomide (Revlimid^®) and dexamethasone. It is expected to start in late 2009. Study 002 evaluates IMGN901 in the treatment of CD56+ solid tumors, which include small-cell lung cancer, Merkel cell carcinoma and ovarian cancers. Patient enrollment is underway in the expansion portion of this trial.

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 Targeted Antibody Payload (TAP) technology uses antibodies to deliver one of ImmunoGen's proprietary 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, trastuzumab-DM1 (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 http://cts.businesswire.com/ct/CT?id=smartlink&url=http%3A%2F%2Fwww.immunogen.com%2Fwt%2Fhome%2Fhome&esheet=6114194&lan=en_US&anchor=www.immunogen.com&index=2&md5=943c33a67f514a7e88cb9b68c20baf75.

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 IMGN901, 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, 2009 and other reports filed with the Securities and Exchange Commission.

Revlimid^® is a registered trademark of Celgene Corporation.

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