News

MIAMI BEACH, Fla., Nov. 1, 2001 /PRNewswire/ -- ImmunoGen, Inc. (Nasdaq: IMGN) today announced that Trastuzumab-DM1 (Herceptin^® conjugated to DM1), a Tumor-Activated Prodrug (TAP), caused complete tumor regression in HER2 positive xenograft models in mice. In addition, Trastuzumab-DM1 demonstrated superior anti-tumor activity when compared to Herceptin (Trastuzumab) alone. Results were presented today at the 2001 American Association for Cancer Research - National Cancer Institute - European Organization for Research and Treatment of Cancer International Conference on Molecular Targets and Cancer Therapeutics (AACR-NCI-EORTC).

Trastuzumab-DM1 is a TAP comprised of the monoclonal antibody, Herceptin, with the potent anti-mitotic agent, DM1. Trastuzumab-DM1 was evaluated in two Herceptin-responsive and one Herceptin-resistant breast tumor models. In the Herceptin-responsive models, Trastuzumab-DM1 caused complete tumor regression in all mice, whereas Herceptin alone slowed tumor growth. In the Herceptin- resistant model, Herceptin alone had no effect on tumor growth. In contrast, Trastuzumab-DM1 caused >90% tumor reduction in all mice. In this Herceptin- resistant model, tumor regrowth was observed after cessation of Trastuzumab- DM1 treatment, yet regression re-occurred when dosing was resumed. The effect was specific for HER2-positive tumors.

"These are the first data presented by one of our partners using our TAP technology with their antibody, illustrating the broad applicability of our proprietary technology platform," said Mitchel Sayare, Ph.D., Chairman and CEO of ImmunoGen, Inc. "We are very enthusiastic about Genentech's preclinical results, and delighted that they have moved Trastuzumab-DM1 onto a clinical development track."

Genentech, Inc. (NYSE: DNA), the U.S. marketer of Herceptin (Trastuzumab), is developing Trastuzumab-DM1. Genentech plans to submit an Investigational New Drug (IND) application for the product candidate to the U.S. Food and Drug Administration (FDA) in 2002. Genentech is conducting preclinical studies in preparation for submitting the IND application. If an IND application is accepted by the FDA, clinical evaluation in humans may begin.

"We are encouraged by these data on Trastuzumab-DM1 which combines our expertise in monoclonal antibodies with ImmunoGen's TAP platform," said Gwen Fyfe, M.D., senior director of Oncology, Medical Affairs. "These preclinical data suggest that Trastuzumab-DM1 is an appropriate clinical candidate and we are conducting additional studies to prepare for an IND filing."

About the ImmunoGen-Genentech Collaboration

In May 2000, Genentech received exclusive worldwide rights to commercialize anti-HER2 targeting products using ImmunoGen's maytansinoid TAP technology. ImmunoGen received an up-front payment of $2 million, and may receive milestone payments potentially up to $40 million, as well as royalties on net sales. Genentech is responsible for manufacturing, product development and marketing of products resulting from the license; ImmunoGen will be reimbursed for any preclinical and clinical materials that it makes under the agreement.

About Breast Cancer

Approximately 1.6 million U.S. women are alive today with breast cancer, with approximately 225,400 new diagnoses annually, according to the National Breast Cancer Coalition. Genentech estimates there are approximately 164,000 women with metastatic breast cancer.

About Herceptin

Herceptin received FDA approval in September 1998 for use in women with HER2 positive metastatic breast cancer. Approximately 25 percent of breast cancer patients are HER2 positive. The genetic alteration in the HER2 gene produces an increased amount of the growth factor receptor protein on the tumor cell surface that can be inhibited with the administration of Herceptin in patients with HER2 positive disease. Herceptin is marketed in the United States by Genentech and internationally by Roche.

About ImmunoGen, Inc.

ImmunoGen, Inc. develops innovative biopharmaceuticals, primarily for cancer treatment. The Company has created potent tumor-activated prodrugs, consisting of drugs coupled to monoclonal antibodies for delivery to and destruction of cancer cells. In addition to Genentech, the Company has collaborative arrangements with GlaxoSmithKline, Abgenix, Millennium, British Biotech, MorphoSys, Avalon Pharmaceuticals, and Raven Biotechnologies.

This press release includes forward-looking statements based on management's current expectations. Factors that could cause future results to differ materially from such expectations include, but are not limited to; the success of the Company's research strategy; the applicability of the discoveries made therein; the difficulties inherent in the development of pharmaceuticals, including uncertainties as to the timing and results of preclinical studies; delayed achievements of milestones; reliance on collaborators; uncertainty as to whether the Company's potential products will succeed in entering human clinical trials and uncertainty as to the results of such trials; uncertainty as to whether adequate reimbursement for these products will exist from the government, private healthcare insurers and third-party payors; and the uncertainties as to the extent of future government regulation of the pharmaceutical business.