Sunesis Pharmaceuticals, Inc. Issued European Patent Covering Voreloxin Combination

SOUTH SAN FRANCISCO, CA--(Marketwire - July 15, 2010) - Sunesis Pharmaceuticals, Inc. (NASDAQ: SNSS) today announced that the European Patent Office (EPO) has granted a European patent covering combinations of the Company’s lead drug candidate, voreloxin, with cytarabine. Cytarabine is the standard-of-care treatment for Acute Myeloid Leukemia (AML), and the therapy used in combination with voreloxin in a fully enrolled Phase 2 trial in patients with relapsed and/or refractory AML. Sunesis has also announced plans to initiate a multinational, randomized, double-blind, placebo-controlled, pivotal Phase 3 clinical trial of voreloxin in combination with cytarabine in a relapsed/refractory AML patient population in the second half of this year. European Patent No. 1 729 770 B1, titled “SNS-595 [voreloxin] and Methods of Using the Same,” following completion of the patent validation process, will provide patent coverage for such combination products in 30 member states of the European Patent Convention, including the major European markets, through 2025. Corresponding patent applications are pending in major markets throughout the world including Australia, Canada, Japan and the United States.

“This patent is an important new addition to our intellectual property estate, as it covers the combination of voreloxin and cytarabine, the contemplated initial market application,” stated Daniel Swisher, Chief Executive Officer of Sunesis. “We are pursuing a sophisticated and deliberate strategy to provide exclusive coverage in the voreloxin patent estate out to 2030. Beyond our granted patents, we have filed patent applications covering formulations, combination uses, dosing, manufacturing processes and composition of matter claims. We look forward to the successful prosecution of these patent applications in multiple territories around the world.”

About Voreloxin

Voreloxin is a first-in-class anticancer quinolone derivative, or AQD, a class of compounds that has not been used previously for the treatment of cancer. Voreloxin both intercalates DNA and inhibits topoisomerase II, resulting in replication-dependent, site-selective DNA damage, G2 arrest and apoptosis. Voreloxin is currently being evaluated in a fully enrolled single agent Phase 2 clinical trial (known as the REVEAL-1 trial) in previously untreated elderly AML patients and in a fully enrolled Phase 2 clinical trial combining voreloxin with cytarabine for the treatment of patients with relapsed/refractory AML. A Phase 2 single agent clinical trial in platinum-resistant ovarian cancer has also completed enrollment. Sunesis plans to initiate a multinational, randomized, double-blind, placebo-controlled, pivotal Phase 3 clinical trial of voreloxin in combination with cytarabine in a relapsed/refractory AML patient population in the second half of this year.

About Acute Myeloid Leukemia

AML is a rapidly progressing cancer of the blood characterized by the uncontrolled proliferation of immature blast cells in the bone marrow. The National Cancer Institute estimated that nearly 13,000 new cases of AML were diagnosed and approximately 9,000 deaths from AML occurred in the U.S. in 2009. Additionally, it is estimated that prevalence of AML is approximately 25,000 in the U.S. AML is generally a disease of older adults, and the median age of a patient diagnosed with AML is about 67 years. AML patients with relapsed or refractory disease and newly diagnosed AML patients over 60 years of age with poor prognostic risk factors typically die within one year, resulting in an acute need for new treatment options for these patients.

About Sunesis Pharmaceuticals

Sunesis is a biopharmaceutical company focused on the development and commercialization of new oncology therapeutics for the treatment of solid and hematologic cancers. Sunesis has built a highly experienced cancer drug development organization committed to advancing its lead product candidate, voreloxin, in multiple indications to improve the lives of people with cancer. For additional information on Sunesis Pharmaceuticals, please visit http://www.sunesis.com.

This press release contains forward-looking statements, including without limitation statements related to the prosecution of patent applications and Sunesis’ plans to initiate a pivotal Phase 3 clinical trial of voreloxin in the second half of this year. Words such as “evaluate,” “planned,” “will,” “look forward” and similar expressions are intended to identify forward-looking statements. These forward-looking statements are based upon Sunesis’ current expectations. Forward-looking statements involve risks and uncertainties. Sunesis’ actual results and the timing of events could differ materially from those anticipated in such forward-looking statements as a result of these risks and uncertainties, which include without limitation, risks related to Sunesis’ need for additional funding to fully finance the planned voreloxin pivotal trial, the risk that Sunesis’ development activities for voreloxin could be halted or significantly delayed for various reasons, the risk that Sunesis’ clinical studies for voreloxin may not demonstrate safety or efficacy or lead to regulatory approval, the risk that data to date and trends may not be predictive of future data or results, the risk that Sunesis’ nonclinical studies and clinical studies may not satisfy the requirements of the FDA or other regulatory agencies, risks related to the conduct of Sunesis’ clinical trials, risks related to the manufacturing of voreloxin, and the risk that Sunesis’ proprietary rights may not adequately protect voreloxin. These and other risk factors are discussed under “Risk Factors” and elsewhere in Sunesis’ Quarterly Report on Form 10-Q for the quarter ended March 31, 2010 and other filings with the Securities and Exchange Commission. Sunesis expressly disclaims any obligation or undertaking to release publicly any updates or revisions to any forward-looking statements contained herein to reflect any change in the company’s expectations with regard thereto or any change in events, conditions or circumstances on which any such statements are based.

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