British Biotech plc 'British Biotech' British Biotech and ImmunoGen to Begin Phase I/II trial of BB-10901/huN901-DM1 in Small Cell Lung Cancer.

Business Editors

OXFORD, U.K & CAMBRIDGE, Mass.--(BUSINESS WIRE)--May 29, 2001

British Biotech (LSE: BBG; Nasdaq: BBIOY) and ImmunoGen Inc. (Nasdaq: IMGN) today announced the start of patient enrollment for a Phase I/II 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.

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 defines 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.

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 a powerful chemotherapeutic agent, the cytotoxic maytansinoid DM1, with the humanized monoclonal antibody, huN901, which binds to a particular protein found on the surface of SCLC cells.

In pre-clinical 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, 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 pre-clinical studies will be reproduced in patients."

Mitchel Sayare, PhD., 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 validation of our TAP technology for 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 running the clinical trials necessary to achieve regulatory approval for BB-10901 in the USA, EU and Japan and has exclusive rights to commercialize BB-10901 in the EU and Japan. ImmunoGen retains similar rights for the USA and rest of the world, as well as worldwide manufacturing rights.

Ends

This news release contains forward-looking statements that reflect the Company's current expectation regarding future events. Forward-looking statements involve risks and uncertainties. Actual events could differ materially from those projected herein and depend on a number of factors including the success of the Company's research strategy, the applicability of the discoveries made therein, the successful and timely completion of clinical studies and the uncertainties related to the regulatory process.

Background Notes

Small cell lung cancer

SCLC is a serious and rapidly progressive form of lung cancer, most common in middle-aged and elderly patients and accounting for around 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. The overall five-year survival rate is less than five per cent

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 Program 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 GlaxoSmithKline, Genentech Inc., Abgenix Inc., Millennium Pharmaceuticals Inc., Avalon Pharmaceuticals Inc., MorphoSys AG, and Raven Biotechnologies Inc.

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