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Sunesis Pharmaceuticals Initiates Phase 2 Clinical Trial of SNS-595 in Ovarian Cancer

12/21/06

SOUTH SAN FRANCISCO, Calif., Dec 21, 2006 /PRNewswire-FirstCall via COMTEX News Network/ -- Sunesis Pharmaceuticals, Inc. (Nasdaq: SNSS) today announced that dosing has begun in a Phase 2 clinical trial of SNS-595, the company's lead anti-cancer therapeutic, in patients with ovarian cancer. The trial is an open-label, multi-center study designed to examine the safety and efficacy of SNS-595 as a second-line agent in patients with ovarian cancer who have failed first-line platinum therapy. SNS-595 is a first-in-class cell-cycle modulator that (in vitro) kills proliferating cancer cells by inducing apoptosis, or programmed cell death, as cells progress through the S phase of the cell cycle.

"Sunesis continues to progress a number of oncology products through development in multiple solid tumor and hematologic malignancy settings. This Phase 2 clinical study in ovarian cancer -- our third Phase 2 trial for SNS-595 -- is the fifth clinical trial we have initiated in the past twelve months," said Daniel Swisher, Chief Executive Officer and President at Sunesis. "These five trials, together with additional planned trials, will provide significant near-term clinical read-outs as we broadly explore the potential of these programs."

"Ovarian cancer is a leading cause of cancer death among women and, unfortunately, tends to recur even in patients who initially achieve a complete response to therapy," said Daniel Adelman, M.D., Senior Vice President of Research and Development at Sunesis. "For patients who develop platinum-resistant disease, their prognosis is especially poor. We believe that SNS-595 has the potential to provide a meaningful benefit in patients with platinum-resistant disease, as we have observed evidence of SNS-595's activity in ovarian cancer patients in our Phase 1 trials as well as in platinum-resistant xenograft models."

Patients with ovarian cancer who have platinum-resistant disease, defined as progression within six months of completing platinum-based chemotherapy or progression while on platinum-based therapy, will be enrolled at multiple centers in the United States and Canada. Eligible patients will receive SNS- 595 every three weeks at the dose and schedule identified in Sunesis' Phase 1 study of SNS-595 in patients with advanced solid malignancies. The trial design anticipates enrolling approximately 55 patients.

About Ovarian Cancer

In the United States, ovarian cancer remains the leading cause of death from gynecologic malignancies and is fifth leading cause of cancer death overall in women behind lung, breast, colorectal and pancreatic cancer. According to the American Cancer Society, in 2006 there will be an estimated 20,000 new cases and more than 15,000 deaths from ovarian cancer in the U.S. alone. The front-line treatment for ovarian cancer is typically a combination of a taxane and a platinum drug. An initial response rate of approximately 70 percent to this type of chemotherapy regimen can be anticipated. In spite of initial response rates, recurrence rates among ovarian cancer patients are high and overall long-term survival has not changed significantly over the past 40 years, with five-year survival rates at less than 30 percent.

About SNS-595

SNS-595 is a promising first-in-class cancer therapeutic currently in a Phase 1 acute leukemia clinical trial and Phase 2 non-small cell and small cell lung cancer and ovarian 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.

Forward-Looking Statements

This press release may contain 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. For further information on Sunesis Pharmaceuticals, please visit http://www.sunesis.com .

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.
http://www.sunesis.com/

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