News

CAMBRIDGE, Mass.--(BUSINESS WIRE)--Dec. 8, 2007--ImmunoGen, Inc. (Nasdaq: IMGN), a biopharmaceutical company that develops targeted anticancer therapeutics using its Tumor-Activated Prodrug (TAP) technology, announced that encouraging clinical findings were reported today at the American Society of Hematology (ASH) 49th Annual Meeting and Exposition with IMGN901 (huN901-DM1) and AVE1642.

Highlights of the findings reported today include:

• 2 patients with multiple myeloma that had failed treatment with a number of prior therapies had an objective response to treatment with IMGN901 (abstract #1174). IMGN901 has been found to be well tolerated in this patient population, and dose escalation in the trial reported is ongoing.
• AVE1642 was successfully evaluated as monotherapy for multiple myeloma in its first Phase I study and is now being tested in combination with Velcade^® (bortezomib) (abstract #1166).

"We are pleased with the results reported today," commented Mitchel Sayare, Chairman and CEO. "Both of these compounds can have an important role to play in the treatment of patients with multiple myeloma as well as other cancers. We believe development of IMGN901 for multiple myeloma is the fastest pathway to approval for this compound, and expect to announce our next steps in its clinical development in early 2008. Sanofi-aventis has implemented an aggressive Phase I program for AVE1642, and we look forward to additional clinical findings being reported with the compound, including data on its clinical activity when used in combination with Velcade."

IMGN901 Clinical Findings Reported

IMGN901 is in development for the treatment of cancers that express the CD56 antigen targeted by the compound. The findings reported today are from a Phase I trial evaluating IMGN901 for the treatment of CD56-expressing multiple myeloma that has failed multiple prior therapies. The primary objective of this trial is to establish the dose-limiting toxicities (DLT) and maximum tolerated dose (MTD) of IMGN901 in this patient population when administered weekly for two weeks in a three-week cycle; evidence of biological activity also is identified.

In this dose-escalation trial, new cohorts of patients are given increasing doses of IMGN901 until DLT is observed. To date, four dose levels - 40, 60, 75, and 90 mg/m2/week - have been evaluated in cohorts of three patients each. DLT has not been reported, and dose escalation is ongoing - two patients are receiving IMGN901 at the next dose level (112 mg/m2/week).

No evidence of biological activity was reported among the patients who received the lowest dose evaluated (40 mg/m2/week). In contrast, 2 of the 9 patients who received either 60, 75, or 90 mg/m2/week had an objective response to treatment.

• A patient treated with IMGN901 at 60 mg/m2/week had a minimal objective response, characterized by a reduction in serum M component by 39%, the disappearance of urine M component, and no evidence of progressive disease in skeleton or bone marrow. This patient previously had been treated with a number of multiple myeloma therapies, including Thalomid^® (thalidomide) and Revlimid^® (lenalidomide). She received fifteen cycles of IMGN901 over 45 weeks.
• A patient treated with IMGN901 at 90 mg/m2/week was responding to treatment until she needed to drop out of the study due to a broken leg. She was experiencing a marked drop in serum M component while she was in the study, and already had a minimal objective response at the time she had to drop out. This patient's multiple myeloma also had relapsed after treatment with a number of prior therapies, including Thalomid, Revlimid, and Velcade. She received a total of four cycles of treatment.

"We are encouraged by the findings to date with IMGN901 in these patients with relapsed/refractory multiple myeloma," commented Asher Chanan-Khan, M.D., of the Roswell Park Cancer Institute. "The compound has been well tolerated to date, with no clinically significant myelosuppression or infusion reactions. Additionally, it has demonstrated compelling evidence of biological activity in patients whose multiple myeloma has relapsed after treatment with well accepted prior therapies."

IMGN901, a TAP compound, is wholly owned by ImmunoGen. It consists of ImmunoGen's highly potent cell-killing agent, DM1, attached to the Company's CD56-binding antibody, huN901. The antibody serves to deliver IMGN901 specifically to its target cancer cells. Once the compound has bound to and entered the cancer cells, the DM1 is released to kill the cells.

AVE1642 Clinical Findings Reported

AVE1642 is a "naked" (non-conjugated) antibody that binds to IGF-1R. It is designed to block a pathway that is used by cancer cells to survive chemotherapy treatments. AVE1642 was initially developed by ImmunoGen and was licensed to sanofi-aventis as part of a broader collaboration between the companies.

The findings reported today are from a Phase I study in which AVE1642 is administered as monotherapy to patients with advanced multiple myeloma. As the compound is designed to be used in combination with chemotherapy, the purpose of this study was to determine the "selected dose" - the AVE1642 dose to be used in further evaluation of the compound. Three dose levels were evaluated, and the highest dose - 12 mg/kg given every three weeks - was chosen as the selected dose based on pharmacokinetic and pharmacodynamic parameters.

AVE1642 was well tolerated and DLT was not observed. Two diabetic patients in the study had Grade 3 hyperglycemia, which was readily reversible. While this study was not designed to assess the activity of AVE1642, the investigators noted that a patient with Bence-Jones multiple myeloma experienced a decrease in proteinuria and relief of bone pain following treatment with AVE1642.

Once the selected dose was established for AVE1642, sanofi-aventis initiated two additional Phase I trials with the compound.

• Sanofi-aventis began evaluation of AVE1642 for the treatment of solid tumors. The compound is administered as monotherapy in the Phase I trial currently underway.
• Sanofi-aventis also advanced the evaluation of the compound for the treatment of hematological or "liquid" tumors by starting a Phase I study that assesses AVE1642 when used in combination with Velcade in patients with relapsed/refractory multiple myeloma. In this trial, AVE1642 is administered at 12 mg/kg every three weeks and Velcade is administered at its approved dosing schedule (1.3 mg/m2 given on Days 1, 4, 8, and 11 every three weeks). AVE1642 has been shown to have synergistic activity when given in combination with Velcade in preclinical studies.

"These data are highly promising and show the synergistic combination of our clinical development expertise and ImmunoGen's antibody expertise," stated Sylvain Durrleman, MD, Vice President, Clinical Development, sanofi-aventis. "We are enthusiastic about the anticancer potential offered by AVE1642."

About ImmunoGen, Inc.

ImmunoGen, Inc. develops targeted anticancer biopharmaceuticals. The Company's proprietary TAP technology uses tumor-targeting antibodies to deliver a potent cell-killing agent specifically to cancer cells. Two TAP compounds wholly owned by ImmunoGen are in clinical testing - IMGN901 and IMGN242 (huC242-DM4). Three TAP compounds are in clinical testing through ImmunoGen's collaborations with other companies - AVE9633 and SAR3419, in development by sanofi-aventis, and T-DM1 (trastuzumab-DM1), in development by Genentech. Additionally, the naked antibody compound, AVE1642, is in development through the Company's collaboration with sanofi-aventis. Multiple compounds are in research/preclinical development through ImmunoGen's collaborations and internal programs.

This press release includes forward-looking statements based on management's current expectations. The statements include, but are not limited to, the statements that ImmunoGen believes both IMGN901 and AVE1642 can have an important role to play in the treatment of patients with multiple myeloma as well as other cancers; that the development of IMGN901 for multiple myeloma is the fastest pathway to approval for IMGN901; that ImmunoGen expects to announce the next steps in the clinical development of IMGN901 in early 2008; and that ImmunoGen expects additional clinical findings to be reported with AVE1642, including data on the compound's clinical activity when used in combination with Velcade. 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. Various factors could cause ImmunoGen's actual results to differ materially from those discussed or implied in the forward-looking statements and you are cautioned not to place undue reliance on these forward-looking statements, which are current only as of the date of this release. Factors that could cause future results to differ materially from such expectations include, but are not limited to the difficulties inherent in the development of novel pharmaceuticals, including uncertainties as to the timing, expense and results of preclinical and clinical studies, and other factors more fully described in ImmunoGen's Annual Report on Form 10-K for the fiscal year ended June 30, 2007 and other reports filed with the Securities and Exchange Commission.

Velcade^® is a registered trademark of Millennium Pharmaceuticals, Inc.

Thalomid^® and Revlimid^® are registered trademarks of Celgene Corporation.

CONTACT:
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ImmunoGen, Inc.
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info@immunogen.com

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