Sunesis Pharmaceuticals, Inc. to Host Conference Call on June 8th to Discuss Voreloxin Data Presented at American Society of Clinical Oncology 2010 and Upcoming Phase 3 Trial in AML

SOUTH SAN FRANCISCO, CA--(Marketwire - May 24, 2010) - Sunesis Pharmaceuticals, Inc. (NASDAQ: SNSS) today announced that it will host a conference call on Tuesday, June 8, 2010 at 9:00 a.m. Eastern time to review the data from the Phase 2 clinical trials of voreloxin in acute myeloid leukemia (AML) and ovarian cancer, scheduled to be presented at the 2010 American Society of Clinical Oncology (ASCO) Annual Meeting on June 7, 2010 in Chicago, Illinois. The Company will also discuss the plan for the Phase 3 trial of voreloxin in AML, which is expected to begin in the second half of 2010.

The Company also announced that the European Hematology Association (EHA) has published abstracts related to the presentation of data from the two Phase 2 trials of voreloxin in AML at the upcoming 15th Congress of the EHA, which will be held June 10 - 13 in Barcelona, Spain.

Conference Call and Webcast Slide Presentation

The company will host a conference call and webcast slide presentation Tuesday, June 8th at 9:00 a.m. Eastern time. Robert K. Stuart, M.D., Professor of Medicine, Division of Hematology/Oncology, Department of Medicine, Medical University of South Carolina, will join the Sunesis senior management team in a discussion of the new Phase 2 data presented at ASCO and review the plans for the upcoming randomized, pivotal Phase 3 clinical trial evaluating the effect on overall survival of voreloxin in combination with cytarabine for the treatment of first relapsed or primary refractory AML. The call can be accessed by dialing (877) 303-9029 (U.S. and Canada) or (914) 495-8584 (international). To access the live audio webcast, or the subsequent archived recording, visit the "Investors and Media - Calendar of Events" section of the Sunesis website at www.sunesis.com. The webcast will be recorded and available for replay on the company's website for two weeks.

Voreloxin Presentations at ASCO

Details on the ASCO presentations are included below.

Oral Podium Presentation: Final data from the Phase 2 study of voreloxin in women with platinum-resistant ovarian cancer will be presented on Monday, June 7, 2010 during the Gynecologic Cancer Clinical Science Symposium at 9:45 a.m. local time in the E Arie Crown Theater (Abstract #5002).

Poster Presentation and Discussion: Final results from the Phase 1b/2 combination study of voreloxin and cytarabine in patients with relapsed or refractory AML will be presented in Room E450a during the Leukemia, Myelodysplasia, and Transplantation Poster Session on Monday, June 7, 2010 from 2:00 to 6:00 p.m., with a discussion in Room E354a from 5:00 to 6:00 p.m. (Abstract #6526).

Poster Presentation and Discussion: Final results from the Phase 2 REVEAL-1 study of single agent voreloxin in newly diagnosed elderly patients will be presented in Room E450a during the Leukemia, Myelodysplasia, and Transplantation Poster Session on Monday, June 7, 2010 from 2:00 to 6:00 p.m., with a discussion in Room E354a from 5:00 to 6:00 p.m. (Abstract #6525).

EHA Presentations

Data from the Company's two Phase 2 trials in AML will be presented at the 15th Congress of the EHA during the Acute Myeloid Leukemia Clinical Poster Session on Friday, June 11, 2010 from 5:45 to 7:00 p.m. local time in Hall 6. The details of the abstracts are included below.

Abstract Number 0070: Final results from the Phase 2 REVEAL-1 study of single agent voreloxin in newly diagnosed elderly patients.

Abstract Number 0077: Final results from the Phase 1b/2 combination study of voreloxin and cytarabine in patients with relapsed or refractory AML.

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 1b/2 clinical trial combining voreloxin with cytarabine for the treatment of patients with relapsed/refractory AML. A Phase 2 single agent trial in platinum-resistant ovarian cancer has also completed enrollment. Sunesis anticipates initiating a Phase 3 trial of voreloxin in AML in the second half of 2010.

About the Pivotal Phase 3 Trial

Sunesis anticipates initiating a Phase 3, randomized, double-blind, placebo-controlled, pivotal trial in patients with first relapsed or primary refractory AML in the second half of 2010. The trial is designed to evaluate approximately 450 patients, multi-nationally, including leading sites in the U.S. and Europe. Patients are expected to be randomized one to one to receive either voreloxin (90 mg/m2) on days one and four in combination with cytarabine (1 g/m2) daily for five days, or placebo in combination with cytarabine. The study's primary endpoint is overall survival.

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 Ovarian Cancer

In the United States, ovarian cancer remains the leading cause of death from gynecologic malignancies and is the fifth leading cause of cancer death overall in women behind lung, breast, colorectal and pancreatic cancers. According to the American Cancer Society, in 2009 there were an estimated 21,550 new cases and more than 14,000 deaths from ovarian cancer in the U.S. alone. Following frontline treatment, recurrence rates among ovarian cancer patients are high. Treatment options remain limited following relapse, and overall long-term survival has not changed significantly over the past 40 years in women with recurrent disease, with less than 30 percent of patients surviving for more than five years.

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, please visit http://www.sunesis.com.

SUNESIS and the logo are trademarks of Sunesis Pharmaceuticals, Inc.

This press release contains forward-looking statements, including without limitation statements related to the planned commencement of a pivotal trial of voreloxin and its timing. Words such as "anticipates," "upcoming" 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 finance the voreloxin pivotal trial and to continue as a going concern, the risk that Sunesis' drug development activities for voreloxin could be halted or significantly delayed for various reasons, the risk that Sunesis' clinical trials for voreloxin may not demonstrate safety or efficacy or lead to regulatory approval, the risk that preliminary data and trends may not be predictive of future data or results, the risk that Sunesis' nonclinical studies and clinical trials 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' Annual Report on Form 10-K for the year ended December 31, 2009 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.