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

Sunesis Pharmaceuticals Reports Second Quarter Financial Results

and Recent Highlights

VALOR Enrollment Exceeds 675 Patients

Cardiff University-Sponsored LI-1

Treatment Arm Evaluated by DMEC

Investigator-Sponsored Phase I/II Trial Evaluating Vosaroxin in Combination with

Decitabine in AML and MDS Initiated at MD Anderson Cancer Center

Sunesis to Host Conference Call Today at 5PM Eastern Time

SOUTH SAN FRANCISCO, Calif., (July 29, 2013) Sunesis Pharmaceuticals, Inc. (NASDAQ: SNSS) today reported financial results for the quarter ended June 30, 2013. Loss from operations for

the three and six months ended June 30, 2013 was $8.6 million and $16.4 million, respectively. As of June 30, 2013, cash, cash equivalents and marketable securities totaled $49.6 million.

We continue to make substantial progress with the VALOR trial, a study with transformational potential in the treatment of AML, said Daniel

Swisher, Chief Executive Officer of Sunesis. With the goal of reaching a final sample size of at least 675 evaluable patients, the trial was designed to over enroll by 5% to 712 patients. As of today, enrollment has exceeded 675 patients, and

we now expect to complete enrollment this quarter, with unblinding of the trial expected in the first half of 2014.

added: As to the Cardiff University-sponsored LI-1 trial in front-line elderly AML, we have been informed that the DMEC will recommend that the monotherapy vosaroxin arm discontinue enrollment. We will be working closely with Cardiff

University to better understand the outcomes in this study arm, and why they differed from our Phase 2 REVEAL-1 trial. We are confident in vosaroxin s broader potential, which we continue to explore through investigator-sponsored studies, such

as the newly initiated MD Anderson Cancer Center trial in previously untreated AML and MDS.

Regarding the MD Anderson Cancer Center-sponsored, Phase I/II trial of vosaroxin and decitabine in AML and

high-risk MDS, Adam R. Craig, M.D., Ph.D., Executive Vice President, Development and Chief Medical Officer of Sunesis, added: This trial allows for the expanded development of vosaroxin in difficult-to-treat AML and MDS populations. Unique and

non-overlapping anti-leukemic activities make vosaroxin and decitabine well suited for frontline combination therapy. We look forward to monitoring the progress of this study and to supporting MD Anderson and others in exploring the full potential

Second Quarter 2013 and Recent Highlights

The primary endpoints of the Phase I trial are to determine the

safety, maximum tolerated dose, and dose limiting toxicity of vosaroxin in combination with decitabine in patients with high-risk MDS or AML who are unable or unwilling to receive standard cytarabine plus anthracycline based chemotherapy. The

primary endpoint of the Phase II trial is to determine the efficacy of the combination based on achievement of complete remission (CR) and CR with incomplete blood count recovery (CRi). Secondary endpoints include safety, CR duration, leukemia-free

survival, and overall survival.

Financial Highlights

Conference Call Information

Sunesis will host an update conference call today, July 29 at 5:00 p.m. Eastern Time. The call can be accessed by dialing (877) 703-6106 (U.S. and Canada) or (857) 244-7305 (international),

and entering passcode 37128110. 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 Sunesis website for two weeks.

VALOR is a Phase 3, randomized, double-blind, placebo-controlled, pivotal trial in patients with first relapsed or refractory AML. The trial s target enrollment is 712 patients at more than 100

leading sites in the U.S., Canada, Europe, South Korea, Australia and New Zealand. The VALOR trial is currently enrolling patients, who are randomized in a ratio of 1:1 to receive either vosaroxin on days one and four in combination with cytarabine

daily for five days, or placebo in combination with cytarabine. The trial s primary endpoint is overall survival. For more information on the VALOR trial, please visit www.valortrial.com.

first-in-class anti-cancer quinolone derivative (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. Both the U.S. Food and Drug Administration (FDA) and European Commission have granted orphan drug designation to vosaroxin for the treatment of AML. Additionally, vosaroxin has been granted fast

track designation by the FDA for the potential treatment of relapsed or refractory acute myeloid leukemia in combination with cytarabine.

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 estimates there will be approximately 14,590 new cases of AML and approximately 10,370 deaths from AML in the

U.S. in 2013. Additionally, it is estimated that the prevalence of AML across major global markets (U.S., France, Germany, Italy, Spain, United Kingdom and Japan) is over 50,000. 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

http://www.sunesis.com.

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

This press release contains forward-looking statements, including statements related to the design, conduct, progress, timing and results of the VALOR

trial, the LI-1 trial and Sunesis other clinical programs discussed in this release. Words such as progress, expect, to occur, will, complete, continue, look forward

to, towards, target, remain, potential, strengthened, 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 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 development and commercialization of vosaroxin, the risk that raising funds through lending arrangements may restrict our operations or produce other adverse results,

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, European Commission 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 Annual Report on Form 10-K for the year ended December 31, 2012, Sunesis Quarterly Report on Form 10-Q for the quarter ended March 31, 2013 and Sunesis other filings with the Securities and Exchange Commission,

including Sunesis Quarterly Report on Form 10-Q for the quarter ended June 30, 2013, 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 Sunesis expectations with regard thereto or any change in events, conditions or circumstances on which any such statements are based.

SUNESIS PHARMACEUTICALS, INC.

CONDENSED CONSOLIDATED BALANCE SHEETS

Note 1: The condensed consolidated balance sheet as of December 31, 2012 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, 2012.

SUNESIS PHARMACEUTICALS, INC.

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS

AND COMPREHENSIVE INCOME (LOSS)

(In thousands, except per share amounts)