British Biotech to Investigate E21R In Rare Childhood Form of Leukemia.

Business Editors

OXFORD, England--(BUSINESS WIRE)--April 4, 2002

British Biotech plc (LSE: BBG, Nasdaq: BBIOY) announced today that the European Commission has designated its novel anti-leukemic drug E21R as an orphan medicinal product in the European Union for the indication of juvenile myelomonocytic leukemia (JMML).

The orphan medicinal product regulation was introduced in Europe in January 2000 in order to encourage development of medicinal products for rare and poorly treated diseases. Orphan designation is based on the rare and serious nature of the disease, the lack of satisfactory therapy for the disease and the product's potential to have significant therapeutic benefit in this disease.

JMML is estimated to affect less than 500 children annually throughout the European Union. More than half the children diagnosed as having JMML are under two years old. As yet, no consistently effective treatment has been developed for the disease. Current treatment involving bone marrow transplantation and chemotherapy has produced limited survival benefits and the overall outlook for JMML sufferers is poor, with a five-year survival in just five percent of cases.

E21R is being developed by British Biotech under a collaboration with the Australian biotechnology company BresaGen Ltd. The drug is currently in a Phase II trial in the UK in patients with acute myeloid leukemia (AML), a more common form of leukemia affecting mainly older adults; and a Phase II trial in Australia in adult patients suffering from chronic myelomonocytic leukemia. Development options in JMML will now be discussed with clinical experts and regulators.

This news release contains forward-looking statements that reflect the Company's current expectations 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 strategies, 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

1. Reference in `Blood'

Evidence of E21R's potential utility in JMML is published in the current issue of the scientific journal, `Blood' (`Transient hematologic and clinical effect of E21R in a child with end-stage juvenile myelomonocytic leukemia', auth. Frederic Bernard, Caroline Thomas, Jean Francois Emile, Timothy Hercus, Bruno Cassinat, Christine Chomienne, and Jean Donadieu; 1 April 2002, Vol. 99, No. 7, pp 2615-2616). Based on their experience with a single patient the authors conclude: "The overall tolerance of E21R appeared to be very good, without the side effects of chemotherapy regimens usually employed in such situations. More studies are necessary to investigate the dose and schedule of administration of the drug and to study its pharmacokinetics, but this novel therapeutic approach clearly deserves further evaluation in JMML."

2. E21R Orphan designation

E21R (GM-CSF receptor antagonist) will be entered in the Community register of Orphan Medicinal Products under the number EU/3/02/089, designation date 18 March 2002.

3. About E21R

E21R is a modified form of granulocyte macrophage stimulating colony factor (GM-CSF), a naturally occurring protein involved in the formation and function of developing blood cells. To regulate these processes in healthy cells, the protein binds to a receptor on the cell surface. This activates the receptor to deliver signals to the cell to promote cell survival, stimulate cell proliferation and to activate various cellular functions.

The same protein has been shown to be necessary for the survival and proliferation of leukemic cells, especially cells from patients with myeloid leukemias such as AML and JMML. Like natural GM-CSF, E21R binds to the surface of these target cells. In this modified form, however, it prevents the receptor from sending its biological signals and the cell dies. In preclinical studies, E21R was shown to be capable of causing `apoptosis', or programmed cell death, in leukemic cells from patients with AML and JMML and to prevent the spread of leukemia. A subsequent Phase I clinical study showed that a 10-day course of treatment with E21R was well tolerated and demonstrated none of the toxic side effects commonly associated with current leukemia treatments.

4. About British Biotech

British Biotech specializes in the research, development and commercialization of new drugs to fight cancer and other diseases with limited treatment options.

The Company currently has four products in active clinical development:

- an Antibiotic Program based on peptide deformylase inhibitors (PDFIs). The
objective is to start the clinical program in patients with serious chest
infections in 2002;

- a research collaboration with Serono SA (Geneva, Switzerland) to identify new

treatments for serious inflammatory diseases, particularly multiple sclerosis;
and

- an exclusive option to take up European development and commercialization
rights over MethylGene's cancer research program in small molecule inhibitors
of DNA methyltransferase.

In research, British Biotech has two ongoing programs and access to a third:

- an Antibiotic Program based on peptide deformylase inhibitors (PDFIs). The
objective is to start the clinical program in patients with serious chest
infections in 2002;

- a research collaboration with Serono SA (Geneva, Switzerland) to identify new
treatments for serious inflammatory diseases, particularly multiple sclerosis;
and

- an exclusive option to take up European development and commercialization
rights over MethylGene's cancer research program in small molecule inhibitors
of DNA methyltransferase.

British Biotech also has collaborations with Schering-Plough Corporation, OSI Pharmaceuticals, Inc., DevCo Pharmaceuticals Ltd and Tanabe Seiyaku.