Sunesis Pharmaceuticals Presents Updated Clinical Data From Ongoing Phase 2 Trial of Voreloxin (Formerly SNS-595) in Ovarian Cancer Patients at the 44th ASCO Annual Meeting

Positive Interim Safety and Efficacy Data Reported Trial Enrollment Advancing Ahead of Schedule

SOUTH SAN FRANCISCO, Calif., May 31 /PRNewswire-FirstCall/ -- Sunesis Pharmaceuticals, Inc. (NASDAQ:SNSS) today presented an update of interim data from the company's ongoing Phase 2 clinical trial of its lead product candidate, voreloxin (formerly SNS-595), in platinum-resistant ovarian cancer patients at the 44th American Society of Clinical Oncology (ASCO) Annual Meeting in Chicago, Illinois.

"Voreloxin is a promising anti-cancer agent demonstrating encouraging signs of single-agent clinical activity in ovarian cancer patients who have failed prior rounds of treatment," said William McGuire, M.D., Medical Director of the Harry and Jeanette Weinberg Cancer Institute at Franklin Square and principal investigator for the Phase 2 clinical trial. "Importantly, treatment with voreloxin has resulted in disease control among approximately half of patients treated and the drug has been very well tolerated. Taken together, these data support a potentially broad therapeutic window for this product candidate and I look forward to seeing the outcomes of treatment with voreloxin at the higher dose levels for patients now enrolling in this study."

To date, voreloxin administered as a single agent at a dose of 48 mg/m(2) once every 21 days has demonstrated clinical activity in platinum-resistant ovarian cancer patients. Thus far, of 62 women evaluable for best response at that dose, one patient had a complete response, five patients had partial responses (one unconfirmed) and forty-five patients achieved stable disease. Forty-eight percent of these 62 patients achieved disease control, defined as stable disease for 90 days or more or a complete or partial response. The preliminary median Progression Free Survival was 91 days, or 13 weeks, at the 48 mg/m(2) dose; twenty-three patients treated at this dose remained on study as of May 12, 2008.

All patients enrolled in the trial have previously failed treatment with platinum-containing regimens, and 26 patients have also failed prior treatment with doxorubicin HCl liposome injection (Doxil(R)). Both platinum-resistant and Doxil-resistant patients in the Phase 2 clinical trial have responded to voreloxin therapy.

In March, based on the indications of clinical activity and the acceptable tolerability profile demonstrated in this Phase 2 clinical trial, Sunesis increased the dose of voreloxin in this trial to 60 mg/m(2) once every 28 days. Thirty-four patients have been enrolled at the 60 mg/m(2) dose level. To date, with an initial eight patients evaluable for efficacy response, one patient has achieved a partial response.

Voreloxin has been well-tolerated in the platinum-resistant ovarian cancer population. With 65 patients evaluable for safety at the 48 mg/m(2) dose and 20 patients evaluable for safety at the 60 mg/m(2) dose, low rates of febrile neutropenia (<10%) or other Grade 3-4 adverse events (fatigue (12%), vomiting (5%) and infections (5% )) have been observed. Based on voreloxin's safety profile, Sunesis recently announced that the protocol for the ongoing Phase 2 clinical trial was amended to increase the dose by 25 percent to 75 mg/m(2) given once every 28 days. Sunesis expects to enroll approximately 30 patients at this new dose level by the end of this year.

"Voreloxin has demonstrated promising clinical activity and tolerability among platinum-resistant ovarian cancer patients and we are focused on advancing this compound in this indication toward late-stage trials," said Daniel Swisher, Sunesis' Chief Executive Officer. "We are pleased by the rapid progress of enrollment of voreloxin at 60 mg/m(2). We are optimistic that the 75 mg/m(2) cohort of this Phase 2 trial will be fully enrolled by year-end, and we look forward to reporting additional efficacy and safety data later this year."

Data from Sunesis' ongoing Phase 2 clinical trial of voreloxin in ovarian cancer were presented today during the Gynecologic Cancer: Ovarian Cancer session in a poster titled "A Phase 2 Trial of Voreloxin (formerly SNS-595) in Women with Platinum-Resistant Epithelial Ovarian Cancer" (Abstract #5582). A copy of the poster will be available on the Sunesis corporate website at http://www.sunesis.com/.

About Voreloxin (formerly SNS-595)

Sunesis' lead compound, voreloxin (formerly SNS-595), is a novel naphthyridine analog, structurally related to quinolones, a class of compounds which 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, irreversible G2 arrest and rapid apoptosis. In addition to the ongoing Phase 2 single-agent trial in platinum-resistant ovarian cancer, voreloxin is currently being evaluated in a Phase 2 clinical trial (known as the REVEAL-1 trial) in previously untreated elderly acute myeloid leukemia (AML) patients, and in a Phase 1b clinical trial combining voreloxin with cytarabine for the treatment of patients with relapsed/refractory AML. In clinical trials conducted to date, voreloxin has been generally well tolerated and has shown objective responses in both solid and hematologic tumor types.

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. For additional information on Sunesis Pharmaceuticals, please visit http://www.sunesis.com/.

SUNESIS and the logo are trademarks of Sunesis Pharmaceuticals, Inc.
Other trademarks are the property of their respective owners.

Safe Harbor Statement

This press release contains forward-looking statements including without limitation statements related to the potential safety and efficacy and commercial potential of voreloxin (formerly SNS-595), planned additional clinical testing and development efforts, the timing of enrollment in the ongoing Phase 2 clinical trial and the announcement of clinical results. Words such as "promising," "encouraging," "supports," "optimistic," "look forward," "expects" 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, the risk that Sunesis' drug discovery and development activities, including enrollment and reporting of results, could be halted significantly or 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' preclinical 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 and manufacturing of voreloxin and risks related to Sunesis' need for additional funding. 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, 2007 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.

Source: Sunesis Pharmaceuticals, Inc.

CONTACT: Investors, Eric Bjerkholt, SVP, Corp. Development & Finance,
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.

Web site: http://www.sunesis.com/

2008-05-31 09:05:00 0374115 PRNEWSWIRE