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Sunesis Pharmaceuticals Presents Clinical Data on SNS-595 at the American Society of Clinical Oncology Annual Meeting

06/05/06

ATLANTA, June 5, 2006 /PRNewswire-FirstCall via COMTEX News Network/ -- Sunesis Pharmaceuticals, Inc. (Nasdaq: SNSS) presented promising clinical data at the 42nd Annual American Society of Clinical Oncology Meeting from two Phase I studies evaluating once-weekly and once-every-three-week dosing schedules of SNS-595 in patients with advanced solid malignancies. In both trials, SNS-595 exhibited clinical activity across a variety of tumor types among end-stage refractory patient populations and was well-tolerated with manageable side effects.

Out of a total of 62 evaluable patients from both Phase I studies, two patients achieved partial responses, another 17 patients achieved stable disease for fifteen weeks or greater, with one patient maintaining stable disease for more than a year. Patients enrolled in both studies had advanced disease in a variety of tumor types including ovarian, lung, colon, pancreatic and renal. All had previously progressive disease at the time of enrollment despite prior treatments. SNS-595 was well tolerated, with a dose-limiting toxicity of reversible non-cumulative neutropenia. In addition, SNS-595 demonstrated consistent and predictable pharmacokinetics across both dosing regimens.

"SNS-595 appears to possess several compelling attributes. SNS-595 has been well tolerated to date, can be dosed on convenient dosing schedules, and has shown evidence of clinical activity across multiple tumor types," said Herbert Hurwitz, M.D. Associate Professor of Medical Oncology and Transplantation at Duke University.

"We continue to be very pleased by the demonstration of activity and safety in our Phase I studies and these data helped in the design of our Phase II program. We are currently conducting Phase II clinical studies of SNS-595 in non-small cell and small-cell lung cancers, with another study currently being planned for patients with ovarian cancer," said Daniel C. Adelman, M.D., Senior Vice President, Research and Development at Sunesis. "In addition, SNS-595's favorable pharmaceutical properties and predictable pharmacokinetics across different dose ranges to date support its potential both as a monotherapy, as well as in combination with other chemotherapeutic agents."

Data were presented in a poster titled "SNS-595 demonstrates clinical activity and dose-proportional pharmacokinetics (PK) in two phase I clinical studies," first authored by Dr. Hurwitz during the Molecular Therapeutics poster session on Sunday, June 4, 2006.

The two Phase I studies were designed to evaluate safety, tolerability, pharmacokinetics and optimal dosing of SNS-595, Sunesis' lead anticancer drug candidate. In the first study, SNS-595 was administered at doses ranging from 3-75 mg/m2 once every three weeks for up to six cycles among 41 patients with advanced solid tumors. In the second Phase I study, 21 patients with advanced cancers received SNS-595 weekly for three weeks with one week off for up to six cycles in doses ranging from 3-24 mg/m2. The maximum-tolerated dose for SNS-595 administered once every three weeks was 48 mg/m2 for heavily pre-treated patients and 60 mg/m2 for minimally pre-treated patients and the maximum-tolerated dose for once-weekly administration of SNS-595 for three weeks was 15 mg/m2.

About SNS-595

SNS-595 is a promising first-in-class cancer therapeutic currently in a Phase I acute leukemia clinical trial and Phase II non-small cell and small cell lung cancer clinical studies. SNS-595, a naphthyridine analog, has a novel mechanism of action that selectively targets and kills proliferating cells during the DNA replication phase of the cell cycle. SNS-595 works through the DNA-protein kinase and p73 dependent pathways to induce apoptosis, or programmed cell death. In clinical trials conducted to date, SNS-595 has been well tolerated and has shown promising signs of clinical activity. In earlier preclinical evaluation, SNS-595 demonstrated broad and potent activity across xenograft, syngeneic and drug-resistant models.

About Sunesis Pharmaceuticals

Sunesis is a clinical-stage biopharmaceutical company focused on the discovery, development and commercialization of novel small molecule therapeutics for oncology and other serious diseases. Sunesis has built a broad product candidate portfolio through internal discovery and in-licensing of novel cancer therapeutics. Sunesis is advancing its product candidates through in-house research and development efforts and strategic collaborations with leading pharmaceutical and biopharmaceutical companies. For additional information on Sunesis Pharmaceuticals, please visit http://www.sunesis.com.

Safe Harbor Statement

This press release contains forward-looking statements that involve substantial risks and uncertainties. Sunesis may not actually achieve the plans, intentions or expectations contained in such forward-looking statements. Actual results or events could differ materially from the plans, intentions and expectations contained in such forward-looking statements. Sunesis does not assume any obligation to update any such forward-looking statements.

SOURCE Sunesis Pharmaceuticals, Inc.

investors, Eric Bjerkholt, CFO of Sunesis Pharmaceuticals, Inc., +1-650-266-3717; or
media, Karen L. Bergman, +1-650-575-1509, or Michelle Corral, +1-415-794-8662, both
of BCC Partners, for Sunesis Pharmaceuticals, Inc.
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