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WALTHAM, Mass.--(BUSINESS WIRE)--Jul. 31, 2009-- ImmunoGen, Inc. (Nasdaq: IMGN), a biopharmaceutical company that develops targeted anticancer therapeutics using its Targeted Antibody Payload (TAP) technology, today announced the presentation of encouraging initial efficacy, safety and tolerability clinical data with its IMGN901 product candidate in the treatment of small-cell lung cancer (SCLC). In two early-stage clinical trials that enrolled patients whose SCLC had recurred following treatment with standard chemotherapies, IMGN901 administration achieved notable tumor shrinkage and/or sustained stable disease. The compound also demonstrated encouraging activity against other CD56-expressing (CD56+) solid tumors. These clinical data are being presented at the 13^th World Conference on Lung Cancer taking place in San Francisco, CA, from July 31 to Aug. 4, 2009.

IMGN901 was created by ImmunoGen to kill tumors that express the CD56 protein targeted by the compound. It consists of a potent cancer-cell killing agent, DM1, attached to a CD56-targeting antibody, huN901, using an engineered linker. IMGN901 currently is in early clinical testing and is a potential treatment for SCLC, Merkel cell carcinomas, ovarian cancers, multiple myeloma, and other CD56+ cancers.

“We are encouraged by the initial efficacy and safety profile of IMGN901 in SCLC and Merkel cell carcinoma, especially as these cancers have proven highly challenging to treat,” stated Professor Penella J. Woll, MD, PhD, Weston Park Hospital, UK. “The data thus far indicate that IMGN901 offers potential for use in a number of indications, including several types of CD56-expressing solid tumors.”

The findings being presented at the 13^th World Conference on Lung Cancer by Professor Woll come from the two IMGN901 trials that included SCLC patients. Study 001 (enrollment has closed) was open to patients with any type of CD56+ solid tumor, including SCLC, during its dose-escalation Phase I leg. In its Phase II leg, enrollment was limited to patients with SCLC or other CD56+ small-cell carcinoma. In this trial, IMGN901 was administered weekly for four weeks every six weeks. Study 002 (enrollment is ongoing) is a dose-escalation trial evaluating IMGN901 in patients with CD56+ solid tumors, including SCLC, when administered daily for three consecutive days every 21 days. In both trials, the SCLC must have recurred following previous treatment with standard therapies for a patient to qualify for enrollment.

SCLC Clinical Data Reported

To date, 68 SCLC patients have been treated with IMGN901. All of these patients had received prior chemotherapy, and most had received at least two previous regimens. Among the findings were:

• The estimated clinical benefit rate was 25%, consisting of patients with an objective response and/or sustained stable disease (non-progression for at least 77 days).
• An objective response was reported in a patient whose SCLC had recurred within four months of treatment with cisplatin, etoposide, and topotecan plus radiation therapy. This patient had a partial response (PR) after his first IMGN901 treatment cycle and reached a 91% reduction in tumor size by the end of his third cycle. His disease progressed after his fourth cycle – 24 weeks after he first received IMGN901.
• Another SCLC patient had an objective response (an unconfirmed PR) and no evidence of disease progression for more than 8 weeks. This patient had previously undergone two other treatment regimens for the cancer.
• 15 patients had sustained stable disease, with an estimated time-to-progression (TTP) ranging from 77 to 168 days (11 to 24 weeks). This is an encouraging finding for an agent used as a second-, third- or later line of therapy in SCLC. For example, in the randomized 200-patient trial that supported the approval of topotecan as a second-line agent for SCLC, the median TTP was 13.3 weeks and 12.3 weeks in the topotecan and cyclophosphamide/doxorubicin/vincristine treatment arms, respectively.¹

Supportive Data in Merkel Cell Carcinoma (MCC)

MCC is typically treated like SCLC as these cancers share biological characteristics, and they generally respond and progress in a similar manner. Both MCC and SCLC express the target of IMGN901 – CD56 – on virtually 100% of cases.

Six patients with MCC had received IMGN901 at the time of data cut-off for presentation. Two of these patients had a confirmed objective response and one had sustained stable disease, for a clinical benefit rate of 50%:

• One patient had a PR after her first IMGN901 treatment cycle and reached a complete response (CR) by the end of her third treatment cycle. This patient has been in remission for more than four years.
• Another patient had a PR after the one treatment cycle she received. This patient’s PR was subsequently confirmed, and - at the time of the data cutoff for the poster - she was continuing to derive clinical benefit at least 15 weeks after withdrawing from the study. It has since been determined that she is still benefiting five months after treatment with IMGN901. This patient declined further treatment with IMGN901 because she experienced reversible posterior leukencephalopathy syndrome during the trial, a reversible condition related to a syndrome (posterior reversible encephalopathy syndrome) that she had previously experienced twice during pregnancies.
• The patient with sustained stable disease had entered the trial with bone metastases. This patient previously had received three other chemotherapy regimens but still had stable disease with IMGN901 that lasted for 79 days.

Supportive Data in Neuroendocrine and Carcinoid Tumors

Twenty-seven patients were treated with IMGN901 who had neuroendocrine or carcinoid tumors. Among these was a patient with small-cell cervical neuroendocrine carcinoma who had an unconfirmed PR; she previously had received two other treatment regimens for her cancer. Among the other 26 patients, half had durable stable disease.

“Based on these clinical data and our findings to date in our lead multiple myeloma trial, we believe IMGN901 may have applications in the treatment of a number of CD56-expressing cancers that have limited therapeutic options today,” remarked James O’Leary, MD, Vice President and Chief Medical Officer of ImmunoGen. “Our plan is to complete Study 002 and use the findings from this trial, together with the findings in multiple myeloma, to determine the next steps in the clinical development of IMGN901 for solid tumors.”

About this Presentation

The IMGN901 findings were accepted by the Conference’s Scientific Committee for presentation as an ePoster and also are to be highlighted in the oral poster discussion session, “Mesothelioma and Small Cell Lung Cancer.” Selection as an ePoster – done with “truly outstanding abstracts” – means the IMGN901 poster presentation will be available to conference participants for viewing and discussion throughout the meeting. The poster presenter is IMGN901 study investigator Professor Penella J. Woll, MD, PhD, Weston Park Hospital, UK.

About Small-Cell Lung Cancer (SCLC)

It is expected that approximately 29,000 new cases of SCLC will be diagnosed in the US in 2009, as these cancers account for an estimated 13% of all US lung cancer cases.^2,3 Newly diagnosed patients generally respond to their first treatment regimen (e.g., cisplatin plus etoposide followed by radiation therapy), but the SCLC then typically recurs. While many patients with recurrent disease could be eligible for additional treatment, survival at this stage is usually less than 6 months.⁴

About Merkel Cell Carcinoma (MCC)

MCC is an aggressive neuroendocrine cancer of the skin that typically occurs on the head/neck, most often in individuals of European ancestry. There are approximately 800 to 1400 new cases of MCC diagnosed in the US each year, with the incidence considered to be increasing.⁵ Medicinal therapy is generally used with patients whose cancer has recurred following surgery and with patients who have metastases at the time of diagnosis. Metastatic disease is associated with a poor outcome, with a median (average) survival time of 6.8 months.

About IMGN901

IMGN901 is a potential treatment for multiple myeloma, SCLCs, MCCs, ovarian cancers, and other solid and hematological cancers that express CD56. This product candidate consists of a CD56-binding antibody, huN901, with a potent cell-killing agent, DM1, attached to it using an engineered linker. IMGN901 is wholly-owned by ImmunoGen, which also developed its huN901, DM1, and linker components.

IMGN901 is being assessed in human clinical trials for the treatment of CD56+ solid tumors and multiple myeloma. Patient enrollment in Study 002 is ongoing and this trial is being used to gain additional safety and activity information with IMGN901 for the treatment of different types of CD56+ solid tumors. Study 003 assesses the compound, used as a single agent, for the treatment of CD56+ multiple myeloma. The Company expects to start Study 005 in September/October 2009 to evaluate IMGN901 for the treatment of CD56+ multiple myeloma when used in combination with lenalidomide plus dexamethasone.

About ImmunoGen, Inc.

ImmunoGen, Inc. develops targeted anticancer therapeutics using its expertise in cancer biology, monoclonal antibodies and the creation and linkage of potent cancer-cell killing agents (CKAs) to such antibodies. The Company’s proprietary TAP technology consists of ImmunoGen’s highly potent CKAs, which have been designed specifically for delivery by antibodies to cancer cells, and the Company’s engineered linkers, which direct the activation of the CKA inside a cancer cell. Compounds utilizing the TAP technology are in clinical testing through ImmunoGen’s own programs and its 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 HealthCare and Amgen.

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, 2008 and other reports filed with the Securities and Exchange Commission.

¹ von Pawel et al., JCO, 1999.
² ACS Cancer Facts & Figures, 2009.
³ Govindan R, 2006.
⁴ Davies A, 2004.
⁵ Based on incidence data from Agelli M, 2003; Hodgson NC, 2006.

Source: ImmunoGen, Inc.

ImmunoGen, Inc.
Carol Hausner, 781-895-0600
Executive Director, Investor Relations
and Corporate Communications
info@immunogen.com