Investor and Media Inquiries: David Pitts Argot Partners 212-600-1902 Eric Bjerkholt Sunesis Pharmaceuticals Inc. 650-266-3717 Sunesis Pharmaceuticals Reports Second Quarter 2011 Financial Results

Sunesis Pharmaceuticals Reports Second Quarter 2011 Financial Results

SOUTH SAN FRANCISCO, Calif., August 11, 2011 Sunesis Pharmaceuticals, Inc. (Nasdaq: SNSS) today reported financial results for the

second quarter ended June 30, 2011. Net loss for the three and six months ended June 30, 2011 was $8.2 million and $6.4 million, respectively. As of June 30, 2011, cash, cash equivalents and marketable securities totaled $48.8

million, with no debt outstanding.

As vosaroxin s importance within the AML drug development landscape continues to rise, our

focus as a company remains on successfully prosecuting the VALOR trial, our robust, adaptive Phase 3 study, and supporting a successful commercialization strategy, said Daniel Swisher, Chief Executive Officer of Sunesis. The VALOR trial

now has over 60 active sites in 11 countries, and is on track to reach the interim analysis in mid-2012 and the planned unblinding in 2013. In addition to our efforts in advancing vosaroxin during the quarter, we brought to light the significant

potential of our pipeline programs with the announcement of a new oncology kinase inhibitor collaboration with Millennium Pharmaceuticals, which includes a very promising oral, selective pan-Raf kinase inhibitor ready to enter clinical

Second Quarter 2011 and Recent Highlights

The programs were originally part of Sunesis 2004 multi-kinase inhibitor

collaboration with Biogen Idec, Inc. Following Biogen Idec s November 2010 announcement to shift its strategic focus and spin out or outlicense its oncology assets, Millennium acquired two of these oncology assets and intends to continue the

development of these assets in collaboration with Sunesis. Biogen Idec and Sunesis will continue with a more focused collaboration directed towards a unique preclinical kinase inhibitor program involved in immunology.

Financial Highlights

VALOR is a Phase 3, randomized, double-blind, placebo-controlled, pivotal trial in patients with first relapsed or refractory AML. The trial is expected

to enroll 450 evaluable patients at approximately 100 leading sites in the U.S., Canada, Europe, Australia and New Zealand. The VALOR trial is currently open for enrollment and patients will be randomized one to one to receive either vosaroxin on

days one and four in combination with cytarabine daily for five days, or placebo in combination with cytarabine. Additionally, the VALOR trial employs an innovative, adaptive trial design that allows for a one-time sample size adjustment by the DSMB

at the interim analysis to maintain adequate power across a broad range of clinically meaningful and statistically significant survival outcomes. The trial s primary endpoint is overall survival. For more information on the VALOR trial, please

visit www.valortrial.com.

Vosaroxin 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. Vosaroxin both intercalates DNA and inhibits

topoisomerase II, resulting in replication-dependent, site-selective DNA damage, G2 arrest and apoptosis.

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 American Cancer Society estimated that 12,330 cases of AML were diagnosed and approximately 9,000 deaths from AML occurred in the U.S. in 2010. 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, vosaroxin, in multiple indications to improve the lives of people with cancer. For

additional information on Sunesis, please visit www.sunesis.com.

This press release contains forward-looking statements, including

statements related to the design, conduct and results of the VALOR trial, vosaroxin s effects, efficacy and safety profile as a single agent and in combination with cytarabine, the benefits to Sunesis from its collaboration arrangement with

Millennium and the sufficiency of Sunesis currently available and accessible funds to the planned unblinding of the VALOR trial. Words such as focus, on track, planned, potential,

promising, demonstrate, will believes, expected 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 results of these risks and

uncertainties, which include, without limitation, risks related to Sunesis need for substantial additional funding to complete the development and commercialization of vosaroxin, risks related to Sunesis ability to raise the capital that

it believes to be accessible and is required to fully finance the VALOR trial until its planned unblinding in 2013, the risk that Sunesis development activities for vosaroxin could be otherwise halted or significantly delayed for various

reasons, the risk that Sunesis clinical studies for vosaroxin 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 vosaroxin and

supply of the active pharmaceutical ingredients required for the conduct of the VALOR trial, the risk of third party opposition to granted patents related to vosaroxin, and the risk that Sunesis proprietary rights may not adequately protect

vosaroxin. 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, 2011, Sunesis Annual Report on Form 10-K for the year ended

December 31, 2010 and Sunesis other filings with the

Securities and Exchange Commission, including Sunesis Quarterly Report on Form 10-Q for the quarter ended June 30, 2011, when available. 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.

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

SUNESIS PHARMACEUTICALS, INC.

CONDENSED CONSOLIDATED BALANCE SHEETS

Note 1: The condensed consolidated balance sheet as of December 31, 2010 has been derived from the audited financial

statements as of that date included in the Company s Annual Report on Form 10-K for the year ended December 31, 2010.

SUNESIS PHARMACEUTICALS, INC.

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS

(In thousands, except per share amounts)