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Sunesis Pharmaceuticals Presents Promising Results of Phase I Clinical Trial of SNS-595 at the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics

11/17/05

PHILADELPHIA, Nov 17, 2005 /PRNewswire-FirstCall via COMTEX News Network/ -- Sunesis Pharmaceuticals, Inc. (Nasdaq: SNSS), a clinical-stage biopharmaceutical company focused on the discovery, development and commercialization of novel small molecule therapeutics, announced positive results from the company's Phase I clinical trial of SNS-595 in patients with advanced solid tumor malignancies. Data were presented in a poster titled "Results of a Phase I Trial of SNS-595 in Patients with Advanced Solid Malignancies" during the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics in Philadelphia, PA.

The Phase I clinical trial of SNS-595 treated 41 patients with advanced solid tumors and was designed to examine the safety, tolerability, and pharmacokinetics of escalating doses of SNS-595. Results from the study demonstrate evidence of sustained disease control using SNS-595 among a variety of tumor types, with one confirmed partial response as well as 12 patients (29 percent) achieving stable disease for more than twelve weeks.

"We are very pleased to have observed such promising signals of clinical activity in a variety of tumor types from a Phase I safety study of patients with significantly advanced disease," said Daniel Adelman, M.D., Senior Vice President of Research and Development at Sunesis. "This anti-tumor response, combined with SNS-595's tolerability, predictable pharmacokinetics and unique mechanism of action provide strong support for this drug's continued development. We are initiating several Phase II clinical trials of SNS-595 in separate tumor settings to determine the optimal therapeutic applications and regulatory strategy for this product."

The Phase I clinical trial was an open-label multi-center study in which patients received increasing doses of SNS-595 by intravenous (IV) injection every three weeks for up to six cycles. In the study, SNS-595 was well- tolerated; the dose-limiting effect was a reversible decrease in the white- blood cell count, while non-hematologic side effects observed were mild and easily managed. Pharmacokinetics were highly reproducible and consistent across patients. In addition, a maximum-tolerated dose of 48mg/m squared was established through this study.

This afternoon at the AACR-NCI-EORTC meeting, Sunesis will also present preclinical data on how SNS-595 is metabolized and its potential for use in combination with other drugs in a poster titled "CYP450 Inhibition, Induction, Metabolism and Routes of Elimination of SNS-595, a Novel Cell Cycle Inhibitor Currently in Phase I Clinical Trials." In addition, during the Thursday afternoon seminar Structural Approaches to Drug Discovery session, Robert McDowell, Ph.D., Sunesis' Vice President of Chemistry will discuss the company's drug-discovery programs, focusing on protein kinase inhibitors.

About SNS-595

SNS-595 is a first-in-class cytotoxic with a novel mechanism of action. SNS-595 acts during the S phase of the cell cycle to induce rapid apoptosis of cells that are actively synthesizing DNA. In clinical trials conducted to date, SNS-595 has been well tolerated and has shown promising signs of clinical activity. In addition, SNS-595 has exhibited broad activity in xenograft studies and drug-resistant tumor models. SNS-595 is currently being evaluated in Phase I clinical studies and will soon be entering Phase II clinical trials in lung cancer.

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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