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CAMBRIDGE, Mass., May 29 /PRNewswire/ -- British Biotech (LSE: BBG; Nasdaq: BBIOY) and ImmunoGen Inc. (Nasdaq: IMGN) today began patient enrollment for the Phase I/II clinical study to evaluate the safety, pharmacokinetic profile and biological activity of the Tumor-Activated Prodrug (TAP), BB-10901/huN901-DM1, in small cell lung cancer (SCLC) patients.

BB-10901 (originally developed by ImmunoGen as huN901-DM1) is an antibody-based treatment derived from ImmunoGen's proprietary TAP technology. It was created by conjugating the powerful chemotherapeutic agent, DM1, a maytansinoid, with the humanized monoclonal antibody, huN901, which binds to a protein found on the surface of SCLC cells.

In preclinical studies, BB-10901 eradicated SCLC tumors. Under the same experimental conditions, other chemotherapies used to treat SCLC, such as cisplatin and etoposide produced only a temporary interruption of tumor growth [Chari, R.V.J., et. al. Proceedings AACR, 2001, Abstract 4405; Liu, C., et.al. Proceedings AACR, 1997, Abstract 190].

British Biotech's Chief Executive Officer, Dr. Elliot Goldstein, commented, "BB-10901 is a potential breakthrough for the treatment of small cell lung cancer, a disease for which there are few treatment options. Having achieved this important progress into patient trials, we are now looking forward to seeing whether the very encouraging results obtained in preclinical studies will be reproduced in patients."

Mitchel Sayare, Ph.D., Chairman and CEO of ImmunoGen, said, "The initiation of clinical trials for our second TAP product with British Biotech marks another important step toward the development of our TAP technology for treating cancer. Initial clinical trial experience gained with our first product has allowed us to define a weekly dosing schedule for BB-10901. We are delighted to collaborate with British Biotech and are confident that its developmental capabilities in cancer will be extremely helpful in the clinical trial program for this product."

Development and commercialization of BB-10901 is being conducted jointly by British Biotech and ImmunoGen under the terms of a collaborative agreement signed by the two companies in May 2000. Under the agreement, British Biotech is responsible for conducting the clinical trials necessary to achieve regulatory approval for BB-10901 in the USA, EU and Japan and has exclusive rights to commercialise BB-10901 in the EU and Japan. ImmunoGen retains similar rights for the USA and the Rest of the World, as well as world-wide manufacturing rights.

Phase I/II Study Design
The open-label, dose-ranging study marks the first use of BB-10901 in cancer patients. The first phase of the study will test increasing doses of BB-10901, to evaluate the safety and maximum tolerated dose of the drug. Once the maximum tolerated dose has been defined, the Phase II part of the study to assess the drug's biological activity will begin. Patients will receive a once-weekly, intravenous dose of BB-10901 for four weeks, followed by two weeks off, which is defined as one cycle of treatment. Patients may be eligible to receive repeat cycles. Approximately 80 patients who have failed other treatment options are expected to participate in this study.

The study is being conducted by Frank V. Fossella, MD, at the University of Texas M. D. Anderson Cancer Center in Houston, and by Anthony W. Tolcher, MD, at the Institute for Drug Development of the Cancer Therapy and Research Center (CTRC) in San Antonio.

Small Cell Lung Cancer (SCLC)
SCLC is a serious and rapidly progressive form of lung cancer, most common in middle-aged and elderly patients, accounting for approximately a quarter of all lung cancer cases. Existing treatments for SCLC comprise chemotherapy and radiotherapy, and although initial responses to therapy are often obtained, patients commonly relapse and most die from their disease. Median survival for such patients is less than a year. Overall 5-year survival rate is less than 5 percent.

British Biotech plc
British Biotech is a research and development stage biopharmaceutical company specializing in the development of new drugs to fight diseases for which there are limited treatment options. The company comprises two distinct businesses: a Product Portfolio of six drugs in development; and an Antibiotic Programme with the potential for multiple product opportunities.

As well as ImmunoGen, British Biotech has collaborative agreements with Tanabe Seiyaku, Schering-Plough Corporation, Serono SA, BresaGen Ltd, Biocompatibles International plc, Devco Ltd, De Novo Pharmaceuticals Ltd, and CareScience Inc.

ImmunoGen, Inc.
ImmunoGen, Inc. develops innovative biopharmaceuticals, primarily in cancer treatment. The company has created potent TAPs, consisting of drugs coupled to monoclonal antibodies for delivery to and destruction of cancer cells. Besides British Biotech plc, the Company has collaborative arrangements with ABGENIX, Inc., Avalon Pharmaceuticals, Inc., Genentech, Inc., GlaxoSmithKline, Millennium Pharmaceuticals, Inc., MorphoSys AG, and Raven Biotechnologies, Inc.

ImmunoGen and GlaxoSmithKline are conducting three Phase I/II dose-ranging studies on its first TAP, SB-408075, to test the safety and pharmacokinetic profile of the TAP. It is in development for the treatment of colorectal, pancreatic, and certain non-small-cell lung cancers.

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 payers; and the uncertainties as to the extent of future government regulation of the pharmaceutical business.

For further information, please contact:

British Biotech plc
Tony Weir, Finance Director
Tel: 01865 781166
Fax: 01865 781047
http://www.britishbiotech.com

ImmunoGen, Inc.
Donna LaVoie, Vice-President,
Corporate Communications & IR
Tel: 617-995-2500
Fax: 617-995-2510
http://www.immunogen.com

Financial Dynamics
David Yates/Sarah Mehanna
Tel: 020 7831 3113
Fax: 020 7242 8695
http://www.fd.com