Vion Pharmaceuticals, Inc. has reached agreement on a Special Protocol Assessment with the US FDA for a Phase III clinical trial of Cloretazine (VNP40101M) in combination with Ara-C (cytarabine) in relapsed acute myelogenous leukaemia (AML). The Special Protocol Assessment (SPA) process is a procedure by which the FDA provides official evaluation and guidance on proposed protocols for pivotal Phase III clinical trials.

The trial will be a placebo-controlled double-blind randomized evaluation of Ara-C plus Cloretazine (VNP40101M) versus Ara-C plus placebo. The trial is designed to accrue 420 patients with AML in first relapse with the patients having experienced a first complete remission (CR) of at least three months but not longer than twenty-four months.

The primary endpoint for the trial is the objective response rate defined as CR plus CRp (a complete remission with incomplete recovery of the platelet count). The trial has been designed to demonstrate a 50 per cent difference in the objective response rate between the experimental arm and the control arm. Secondary endpoints include time-to-progression, duration of response, survival and toxicity.

Alan Kessman, CEO, commented, "We are pleased to have successfully concluded our discussions with the FDA related to the design of this pivotal trial for our lead anticancer agent Cloretazine (VNP40101M). We look forward to getting the trial started as soon as possible."

An interim analysis is planned after accrual and adequate follow up for the objective response rate of the first 210 patients. The Company expects the trial to commence in the first quarter of 2005 and estimates that patient accrual will take place over 30 months in multiple centres in the North America and Europe.

Vion Pharmaceuticals, Inc. is developing novel agents for the treatment of cancer. Vion has two agents in Phase II clinical trials: Cloretazine (VNP40101M), a unique sulfonylhydrazine alkylating agent, and Triapine, a potent inhibitor of a key step in DNA synthesis. In preclinical studies, Vion is developing KS119, a hypoxia-selective compound from the sulfonylhydrazine class, and heterocyclic hydrazones.