Vion Pharmaceuticals Presents Data on Onrigin(TM) Elderly AML Trials at the ASCO(R)...

Vion Pharmaceuticals Presents Data on Onrigin(TM) Elderly AML Trials at the
ASCO(R) Annual Meeting

NEW HAVEN, Conn., June 1 /PRNewswire-FirstCall/ -- VION PHARMACEUTICALS, INC.
(OTC BULLETIN BOARD: VION) today announced that an analysis of clinical data
of its lead anticancer agent Onrigin (laromustine) Injection in patients over
the age of sixty with acute myeloid leukemia (AML) was presented in a poster
at the 2009 American Society of Clinical Oncology (ASCO) Annual Meeting in
Orlando, Florida.

Ann Cahill, Vice President, Clinical Development, commented, "This poster
presents an objective analysis of the co-morbid conditions with which so many
elderly AML patients present. It demonstrates that the patient population
forming the basis of the efficacy claims in Vion's New Drug Application was
indeed a poor-risk population, with multiple risk factors predicting for a
poor prognosis."

In the analysis, 140 AML patients over the age of sixty treated with Onrigin
in two Phase II clinical trials were analyzed for co-morbidity according to
the hematopoetic cell transplantation-specific co-morbidity index (HCT-CI).
The HCT-CI is an adapted version of the Charlson Comorbidity Index (CCI), and
was originally developed to predict outcomes in patients undergoing allogeneic
stem cell transplant. It has since been used to describe outcome for AML
patients receiving induction chemotherapy. HCT-CI scores have been shown to
be predictive of early death and survival in patients over the age of 60
receiving induction therapy for AML.

The 140 patients included all 85 patients from the Company's pivotal trial in
elderly poor-risk AML, and 55 patients in a retrospectively determined subset
from a previous trial in elderly AML. The median age of this population was
74 years. HCT-CI scores were separated into three risk groups for non-relapse
mortality and survival: low (0), intermediate (1-2), and high (3 or greater).
The analysis established that 81% of the patients in the combined population
had an HCT-CI score of 3 or greater and that the median score was 5 (range
0-12), confirming the poor-risk nature of this patient group. Patients with
an HCT-CI score of 3 or greater had an overall response rate of 34%, an
induction death rate (death within 30 days of first induction) of 14%, and a
Kaplan-Meier estimate of survival at twelve months of 21%.

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.

COMPANY CONTACT: Vion Pharmaceuticals, Inc.
Alan Kessman, Chief Executive Officer
Howard B. Johnson, President & CFO
(203) 498-4210

SOURCE Vion Pharmaceuticals, Inc.

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