Vion Pharmaceuticals to Present Data on Onrigin(TM)at the American Society of Clinical Oncology Annual Meeting

NEW HAVEN, Conn., May 29 /PRNewswire-FirstCall/ -- VION PHARMACEUTICALS, INC. today announced that an analysis of clinical data of its lead anticancer agent Onrigin (laromustine) Injection in acute myeloid leukemia (AML) would be presented in a poster at the 2009 American Society of Clinical Oncology (ASCO) Annual Meeting in Orlando, Florida.

The poster (Abstract #7050) entitled "Comorbidity Description Using the Hematopoietic Cell Transplantation-Specific Comorbidity Index (HCT-CI) in Elderly de novo Poor Risk AML Patients Treated with Laromustine" will be presented at the Orange County Convention Center, Level 2, West Hall C, Board #M4 from 8:00 a.m. to 12:00 p.m. on Saturday, May 30, 2009. A copy of the poster will be available on Vion Pharmaceuticals' website, www.vionpharm.com, on May 30, 2009 at 8:00 a.m. Eastern Time.

In addition, the Company announced that additional data on Onrigin would be presented in a poster from an investigator-sponsored trial of Onrigin in combination with cytarabine in elderly patients with previously untreated AML. The trial is sponsored by the Weill-Cornell Medical College. The poster (Abstract #7054) entitled "Phase I Trial of Laromustine in Combination with Infusional Ara-C in Elderly Patients Over Age 60 with Newly Diagnosed AML or High-Grade MDS" will be presented at the Orange County Convention Center, Level 2, West Hall C, Board #M10 from 8:00 a.m. to 12:00 p.m. on Saturday, May 30, 2009.

About Vion

Vion Pharmaceuticals, Inc. is committed to extending the lives and improving the quality of life of cancer patients worldwide by developing and commercializing innovative oncology therapeutics. Vion has two agents in clinical trials, Onrigin (laromustine) Injection and Triapine(R). The Company has an NDA under review with the FDA for Onrigin for remission induction treatment for patients sixty years of age or older with de novo poor-risk acute myeloid leukemia (AML). Triapine(R), a potent inhibitor of a key step in DNA synthesis, is being evaluated in clinical trials sponsored by the National Cancer Institute. For additional information on Vion and its product development programs, visit the Company's Internet web site at www.vionpharm.com.

This news release contains forward-looking statements. Such statements are subject to certain risk factors which may cause Vion's plans to differ or results to vary from those expected, including Vion's potential inability to obtain regulatory approval for its products, particularly Onrigin (laromustine) Injection, delays in the regulatory approval process, particularly for Onrigin (laromustine) Injection, including possible delays in the FDA's review process beyond our expectation for approval in December 2009, delays or unfavorable results of drug trials, the possibility that favorable results of earlier preclinical studies, clinical trials or interim clinical trial data are not confirmed by safety and efficacy results in later or final clinical trials, the need for additional research and testing, the inability to manufacture product, the potential inability to secure external sources of funding to continue operations, the inability to access capital and funding on favorable terms, continued operating losses and the inability to continue operations as a result, and a variety of other risks set forth from time to time in Vion's filings with the Securities and Exchange Commission, including but not limited to the risks attendant to the forward-looking statements included under Item 1A, "Risk Factors" in Vion's Form 10-K for the year ended December 31, 2008, Vion's Form 10-Q for the quarter ended March 31, 2009, and Vion's Post-Effective Amendments on Form S-1 Registration Statement filed on March 23, 2009. Except in special circumstances in which a duty to update arises under law when prior disclosure becomes materially misleading in light of subsequent events, Vion does not intend to update any of these forward-looking statements to reflect events or circumstances after the date hereof or to reflect the occurrence of unanticipated events.

CONTACT: Alan Kessman, Chief Executive Officer, or Howard B. Johnson,
President & CFO, both at +1-203-498-4210, both of Vion Pharmaceuticals,
Inc.

Web site: http://www.vionpharm.com/