Bioenvision Signs Master Services Agreement with Penn Pharmaceutical; Update on Clofarabine Clinical Program.

Business Editors

NEW YORK--(BUSINESS WIRE)--May 15, 2003

Bioenvision, Inc. (OTCBB:BIOV) today announced that it has signed a Master Services Agreement with Penn Pharmaceutical for the labeling, packaging, storage and distribution of clofarabine in Europe.

This agreement comes as the Company plans for the imminent enrollment of patients in two pivotal Phase II multi-center trials for clofarabine in centers in the U.K. and Europe.

"We are delighted to have added Penn Pharmaceutical to our operating team for the distribution of clofarabine," said Dr. Christopher B. Wood, Chairman and Chief Executive Officer of Bioenvision. "We believe that, together with the many other experienced professionals supporting clofarabine development from drug substance manufacture through distribution, we now have the experienced and professional team in place to meet our operational and marketing needs in the near and long term."

Clofarabine Program Update

Bioenvision has initiated two pivotal Phase II multi-center trials of clofarabine to evaluate the drug's efficacy in adult patients with Acute Myeloblastic Leukemia (AML) and in children with Acute Lymphocytic Leukemia (ALL). Initial patient enrollment is anticipated within eight weeks.

The adult AML study, to take place at multiple sites in the U.K., will enroll 40 patients over the next two quarters prior to interim analysis. The pediatric ALL study will take place in multiple sites in the U.K. and other E.U. countries. Both trials will be managed by RRD International, LLC and Tessman Technologies Ltd.

"The treatment options for older patients with AML are quite limited; the clinical need is great and we are enthusiastic about the opportunity to advance clofarabine as a potential therapy in this group," said Professor Alan Burnett, principal investigator on the adult AML trial at the University Hospital of Wales in Cardiff.

Clofarabine is currently undergoing Phase II clinical trials in the U.S. for the treatment of acute leukemia in children and adults, and is also being evaluated in solid tumors. Clofarabine has been granted Orphan Drug Status in both Europe and the United States for Acute Lymphocytic Leukemia (ALL) and Acute Myeloblastic Leukemia (AML).

About Penn Pharmaceutical

Penn Pharmaceuticals Services is a U.K.-based pharmaceutical contract manufacturing company offering fully integrated formulation and analytical development services, clinical trial manufacturing, packaging and supply management, and contract manufacturing services. Facilities include extensive development and manufacturing capabilities for tablets, capsules, liquids, dry powders, ointments, creams and gels, and suppositories; FDA approved production and laboratory facilities; comprehensive clinical trial packaging units; and well renowned and acknowledged product and analytical development expertise supported by well-equipped laboratories and plant.

About Clofarabine

Clofarabine (Cl-F-ara-A, CAFdA) is a second generation purine nucleoside antimetabolite. Nucleoside analogs are antimetabolites that affect DNA synthesis. Clofarabine combines many of the favorable properties of the two most commonly used nucleoside analogs, Fludarabine Fludara(R) by Schering AG (NYSE:SHR) and Cladribine, Leustatin(R) by Johnson and Johnson (NYSE:JNJ), but is reported to have greater potency at damaging the DNA of Leukemia cells than these other agents. (Blood, "Mitochondrial Toxity of Deoxyadenoside Analogs", November 15, 2000, Volume 96, Number 10). In a single centre Phase II study of Clofarabine in patients with refractory AML, 42% of the patients had a complete response rate (CR) and a further 13% had a partial response (CRp).

About Bioenvision

Bioenvision's (OTCBB:BIOV.OB) primary focus is the acquisition, development and distribution of compounds and technologies for the treatment of cancer. Bioenvision has a broad pipeline of products for the treatment of cancer, including: clofarabine, Modrenal(R) (for which Bioenvision has obtained regulatory approval for marketing in the United Kingdom for the treatment of post-menopausal breast cancer), and other products in clinical trials. Bioenvision is also developing anti-infective technologies, including the OLIGON technology, an advanced biomaterial that has been approved for certain indications by the FDA in the U.S.

Certain statements contained herein are "forward-looking" statements (as such term is defined in the Private Securities Litigation Reform Act of 1995). Because these statements include risks and uncertainties, actual results may differ materially from those expressed or implied by such forward-looking statements. Specifically, factors that could cause actual results to differ materially from those expressed or implied by such forward-looking statements include, but are not limited to: risks associated with preclinical and clinical developments in the biopharmaceutical industry in general and in Bioenvision's compounds under development in particular; the potential failure of Bioenvision's compounds under development to prove safe and effective for treatment of disease; uncertainties inherent in the early stage of Bioenvision's compounds under development; failure to successfully implement or complete clinical trials; failure to receive marketing clearance from regulatory agencies for our compounds under development; acquisitions, divestitures, mergers, licenses or strategic initiatives that change Bioenvision's business, structure or projections; the development of competing products; uncertainties related to Bioenvision's dependence on third parties and partners; and those risks described in Bioenvision's filings with the SEC. Bioenvision disclaims any obligation to update these forward-looking statements.