Clofarabine's Excellent Results Confirmed at 6th International Symposium on Leukemia and Lymphoma; Latest Results from Adult and Pediatric Acute Leukemia Studies.

NEW YORK -- Bioenvision (Nasdaq: BIVN) today announced interim results from the ongoing clinical studies of clofarabine in pediatric and adult acute leukemia trials which confirm clofarabine's outstanding profile observed in previous studies. Clofarabine has recently been approved by the FDA in the U.S. for the treatment of relapsed/refractory pediatric Acute Lymphocytic Leukemia (ALL).

Professors Alan K. Burnett and Varsha Ghandhi, world-renowned leukaemia experts, presented data from clofarabine's ongoing clinical development program at the 6th International Symposium and Expert Workshops on Leukemia and Lymphoma in Amsterdam, Netherlands, March 17-19, 2005.

Professor Burnett, Chairman of the U.K. National Cancer Research Institute Hematological Oncology Study Group, presented the first interim analysis of the Phase II multi-center, international study designed to further evaluate clofarabine in older adult patients with Acute Myeloid Leukemia (AML) who are unsuitable for intensive chemotherapy. To date, a total of 23 patients have been enrolled in the study and, of the 12 evaluable patients, a complete response rate of 58% (6 CR and 1 CRp) has been observed by the investigators. An additional 3 patients achieved a partial response giving a combined response rate of 83%. "These data further confirm the 60% complete response rate we achieved in the pilot study of 30 patients conducted last year and validated by an independent response panel," commented Professor Burnett. The initial patients were enrolled mainly in the United Kingdom, but new centers have now been initiated in Ireland, Italy and France and enrollment is expected to increase rapidly.

Professor Ghandhi of the M.D. Anderson Cancer Center, in Houston, Texas, shared the interim results from the European pediatric relapsed/refractory Acute Lymphoblastic Leukemia (ALL) multi-center study. A total of 23 patients have been enrolled and, of the 12 evaluable patients, 42% achieved a complete response (2 CR and 3 CRp), as determined by the investigators.

"This is exciting news for clofarabine and for Bioenvision," said Christopher Wood M.D., Chairman and CEO of Bioenvision. Dr. Wood added, "These clinical results will form an important part of our regulatory strategy in Europe."

Conference Call Information

Bioenvision will host an investor conference call today, March 21st, 2005 at 8:30AM Eastern Time to discuss the subject of this press release. Those parties interested in participating via telephone may join by dialing [phone] or [phone] for calls outside of Canada and the United States.

A telephone replay of the conference call will be available one hour following the conclusion of the call and will be available for replay until March 28, 2005 at midnight Eastern Time. To access the telephone replay, dial [phone] domestically, or [phone] for calls outside of Canada and the United States, and enter pin number 5854514.

The conference call will also be webcast live and may be accessed by visiting Bioenvision's website at www.bioenvision.com. A replay of the audio webcast will be available on the Company's website one hour following the conclusion of the call on March 21st, 2005 and will be available for replay until March 28, 2005 at midnight Eastern Time.

About Clofarabine

The FDA granted marketing approval for clofarabine for the treatment of patients ages 1 to 21 with refractory or relapsed ALL after at least two prior conventional regimens. It is the first new pediatric cancer drug to be introduced in over 10 years.

Clofarabine is a next generation of the drug class, purine nucleoside analogs that inhibit DNA production necessary for cancer cell growth. Bioenvision and Genzyme (Nasdaq: GENZ) are co-developing clofarabine. Bioenvision holds an exclusive worldwide license to clofarabine (outside Japan and Southeast Asia). Bioenvision granted an exclusive sublicense for the US and Canadian cancer markets to Genzyme. Bioenvision holds an exclusive license in the US and Canada to all non-cancer indications and an exclusive, irrevocable option to develop and market clofarabine for all human applications in Japan and Southeast Asia.

Bioenvision originally obtained clofarabine development and commercialization rights under patents held by Southern Research Institute.

Clofarabine has been granted orphan drug designation for the treatment of adult and pediatric ALL and AML in the U.S. and Europe. In the U.S., orphan drug status extends market exclusivity for seven years. The FDA also recently granted an additional six months market exclusivity to clofarabine under the Best Pharmaceuticals for Children Act. In Europe, the designation provides marketing exclusivity for 10 years.

About Bioenvision

Bioenvision's 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 (in co-development with Genzyme Corporation), 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.