December 4, 2003

News Release: First Patient Enters Pivotal European Phase II Pediatric Leukemia Study for Bioenvision's Clofarabine

Bioenvision (AMEX:BIV) today announced the first patient has received treatment in a pivotal European Phase II pediatric study in acute lymphoblastic leukemia (ALL), with its lead compound, clofarabine. The child was treated at a leading London hospital and a further 64 patients will be enrolled in the study from five additional European countries.

The children to be entered into the study have a poor prognosis since all prior treatments will have failed. This clinical trial could be one of the most important childhood leukemia studies to be conducted in this group of patients in recent times. Approximately 500 children are diagnosed with leukemia per year in the U.K. and the disease remains the biggest cause of cancer deaths in children. Additional studies with clofarabine in adults with acute leukemias are already underway in Europe and in the U.S.

This new study will build on an already impressive database for clofarabine. The highlights of the Phase I study were published online in October 2003 in Blood, the journal of the American Society of Hematology(1). An overall response rate of 32% was observed in a population of 25 children with multiple relapsed or refractory acute leukemias.

Commenting on the significance of the first patient entering the new study, Professor Vaskar Saha, Head of Cancer Research U.K's Children's Cancer Group, said, 'The first patient enrolled into this pivotal study is an important milestone in the development of new treatments for children with high risk leukemias. Clofarabine has already performed strongly in clinical studies in patients for whom previous chemotherapy regimens have failed, and we are therefore very excited about these new studies. We are seeing the prospect of introducing a new treatment for patients who have very few options remaining.'

Christopher B. Wood, M.D., Chairman and CEO of Bioenvision commented, 'We are delighted that this important study has commenced and we believe clofarabine can make a real difference to the lives of seriously ill children and their families.'

A number of important regulatory milestones have already been achieved for clofarabine. 'Orphan Medicinal Product'designation has been granted by the European Agency for the Evaluation of Medicinal Products (EMEA) as a treatment for ALL and acute myeloid leukemia (AML). In the U.S., clofarabine has been granted 'fast track' designation by the Food and Drug Administration. On October 22, 2003, the first part of a New Drug Application (NDA) for clofarabine was filed with the FDA, for the treatment of refractory or relapsed pediatric acute leukemias.

References

1. Jeha S et al, Blood First Edition Paper, prepublished online October, 2003; DOI 10.1182/blood-2003-06-2122.). The article is available on line at www.bloodjournal.org.

About Clofarabine

Bioenvision's partner in North America, ILEX Oncology Inc. (Nasdaq:ILXO), has submitted the first part of a New Drug Application (NDA) with the U.S. Food and Drug Administration (FDA) for clofarabine for the treatment of refractory or relapsed pediatric acute leukemia. It is anticipated that the remainder of the NDA will be submitted on a 'rolling'basis and is expected to be completed in the first half of 2004.

Bioenvision granted ILEX the right to develop clofarabine in the United States and Canada. Bioenvision is entitled to milestone payments tied to the development of the compound and is entitled to royalties on North American sales. Bioenvision is developing clofarabine exclusively in the rest of the world. Bioenvision originally obtained clofarabine development and commercialization rights under patents held by Southern Research Institute.

Clofarabine is a second-generation purine nucleoside antimetabolite. Nucleoside analogues are antimetabolites that affect DNA synthesis. Clofarabine was rationally designed to combine many of the favorable properties of the two most commonly used nucleoside analogs, fludarabine and cladribine, but is reported to have greater potency at damaging the DNA of Leukemia cells than these other agents. (Blood, 'Mitochondrial Toxicity of Deoxyadenoside Analogs', November 15, 2000, Volume 96, Number 10). In a single center 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 (Amex:BIV), a New York based biopharmaceutical company, is primarily focused on 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 (in co-development with ILEX Oncology, Inc.), Modrenal(R) (for which Bioenvision has obtained regulatory approval for marketing in the United Kingdom for the treatment of post-menopausal breast cancer following relapse to initial hormone therapy), and other products in clinical trials. Bioenvision is also developing anti-infective technologies, including the OLIGON technology; an advanced biomaterial that has been incorporated into various FDA approved medical devices. For more information on Bioenvision please visit our Web site at www.bioenvision.com.

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.

SOURCE: Bioenvision Ltd

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