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                           COMPANY CONTACT:   VION PHARMACEUTICALS, INC.
                                              Alan Kessman, CEO
                                              Howard B. Johnson, President & CFO
                                              (203) 498-4210


VION ENTERS INTO AGREEMENTS FOR $32.5 MILLION SALE OF COMMON STOCK



NEW HAVEN, CT, JANUARY 26, 2005 -- VION PHARMACEUTICALS, INC. (NASDAQ SMALLCAP:
VION) today announced that it has agreed to sell up to 10,000,000 shares of its
common stock in a registered direct offering at a price of $3.25 per share to
institutional investors. All of the shares are being sold by Vion
Pharmaceuticals, Inc., and the shares are being offered under the company's
effective shelf registration statement relating to the possible sale from time
to time of the company's securities. CIBC World Markets Corp. and Leerink Swann
& Company are acting as the exclusive placement agents for the offering.

This press release shall not constitute an offer to sell or the solicitation of
an offer to buy, nor shall there be any sale of these securities in any
jurisdiction in which such offer, solicitation or sale would be unlawful prior
to the registration or qualification under the securities laws of any such
jurisdiction. Copies of the prospectus supplement and the accompanying
prospectus related to the offering can be obtained from Vion.

Vion Pharmaceuticals, Inc. is developing novel agents for the treatment of
cancer. Vion has two agents in Phase II clinical trials: CLORETAZINE(TM)
(VNP40101M), a unique sulfonylhydrazine alkylating agent, and Triapine(R), a
potent inhibitor of a key step in DNA synthesis. In preclinical studies, Vion is
also evaluating KS119, a hypoxia-selective compound from the sulfonylhydrazine
class, and heterocyclic hydrazones. The Company is also known for developing
TAPET(R), a modified Salmonella vector used to deliver anticancer agents
directly to tumors. 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 ability to secure external
sources of funding to continue its operations, the inability to access capital
and funding on favorable terms, continued operating losses and the inability to
continue operations as a result, its dependence on regulatory approval for its
products, delayed or unfavorable results of drug trials, the possibility that
favorable results of earlier clinical trials are not predictive of safety and
efficacy results in later clinical trials, the need for additional research and
testing, 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 discussed in Vion's Annual Report on Form 10-K/A for the year ended
December 31, 2003. 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.