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Sunesis Pharmaceuticals Initiates Phase II Clinical Trial of SNS-595 in Small Cell Lung Cancer

03/20/06

SOUTH SAN FRANCISCO, Calif., March 20, 2006 /PRNewswire-FirstCall via COMTEX News Network/ -- Sunesis Pharmaceuticals, Inc. (Nasdaq: SNSS) today announced that patient treatment has commenced in a Phase II clinical trial of SNS-595, the company's lead anti-cancer therapeutic, in patients with small cell lung 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 small cell lung cancer who have failed first-line 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 demonstrate rapid progress in the advancement of multiple oncology products through development. This Phase II study in small cell lung cancer -- our second Phase II trial for SNS-595 -- is the fourth clinical trial we have initiated since last fall," said Daniel N. Swisher, President and Chief Executive Officer at Sunesis. "Through these studies, we are learning more about the promising anticancer activity of our two lead oncology candidates."

"Small cell lung cancer makes up approximately sixteen percent of lung cancers, and is characterized by rapid growth and spread, and commonly relapses within months of treatment," said Daniel Adelman, M.D., Senior Vice President of Research and Development at Sunesis. "First-line treatment for small cell lung cancer typically involves use of a platinum drug such as cisplatin in combination with a second agent, typically etoposide. While these chemotherapies are beneficial, most patients' disease recurs. We believe that SNS-595 has the potential to provide a meaningful benefit in second-line treatment as we have observed evidence of SNS-595's activity in platinum-resistant and etoposide-resistant xenograft models."

Patients with small cell lung cancer who have failed first-line treatment will be enrolled at multiple centers in the United States and Canada. Eligible patients will receive SNS-595 every three weeks at a dose and schedule identified in Sunesis' Phase I study of SNS-595 in patients with advanced solid malignancies. The trial design anticipates enrolling 80 patients -- 40 that are refractory and 40 that are sensitive.

According to the American Cancer Society, in 2006, approximately 160,000 people will die of lung cancer and approximately 174,000 new cases will be diagnosed in the U.S. alone. Of these, approximately sixteen percent will be small cell lung cancer. Small cell lung cancer is estimated to affect approximately 34,000 patients in the U.S. alone with 29,000 new cases diagnosed each year. Characterized by the small round cells that make up small cell lung cancer tumors, this form of lung cancer tends to spread widely through the body as cells multiply quickly, forming large tumors and spreading to the lymph nodes and other organs. Small cell lung cancer is almost always associated with smoking.

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. Sunesis is currently conducting an open-label Phase II clinical study of SNS-595 in patients with non-small cell lung cancer and a Phase I dose escalation safety clinical study in patients with acute leukemias. 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.

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.
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