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Sunesis Pharmaceuticals Presents SNS-314 Aurora Kinase Inhibitor Data Showing Broad Anti-Tumor Activity, Dosing Flexibility

03/20/07

Research from Non-clinical Studies Presented at the Targeted Anticancer Therapies (TAT 2007) and the Keystone Symposia Molecular Targets for Cancer Meetings Support Phase 1 Trial Design

SOUTH SAN FRANCISCO, Calif., March 20, 2007 /PRNewswire-FirstCall via COMTEX News Network/ -- Sunesis Pharmaceuticals, Inc. (Nasdaq: SNSS), presented non-clinical data on its development-stage compound, SNS-314, at two leading scientific meetings focused on targeted anticancer medicines. Findings from in vitro and in vivo studies demonstrate that SNS-314 is a selective inhibitor of Aurora kinases with consistently potent anti-tumor activity across a number of cancer types.

"Based on the data presented at TAT 2007 and the Keystone Symposia 'Molecular Targets for Cancer' meetings, we believe that SNS-314 has a compelling preclinical profile and merits full clinical development. In diverse xenograft models, this anticancer agent demonstrates good activity that is linked to mechanistic markers of Aurora inhibition," said Daniel C. Adelman, M.D., Senior Vice President, Research and Development at Sunesis. "The results reported from our non-clinical studies of SNS-314 are impressive, and we are looking forward to starting the Phase 1 dose-escalating clinical study of SNS-314 in patients with advanced solid tumors in the second quarter. In this trial, patients will receive three weekly doses of SNS-314 in a four-week dosing regimen."

In an oral presentation delivered on March 10 at the 5th International Symposium on Targeted Anticancer Therapies (TAT 2007) meeting held in Amsterdam, Sunesis researchers presented results showing SNS-314's anti-tumor activity across a number of cancer models. SNS-314 demonstrated potent and sustained activity in xenograft models of colon, breast, prostate, lung, ovarian and skin cancers, where intermittent dosing caused up to 96 percent tumor growth inhibition. These results suggest that weekly administration may provide an optimal regimen for treating tumors in the clinic.

At the Keystone Symposia "Molecular Targets for Cancer" meeting in Whistler, British Columbia, Canada, results from studies of SNS-314's mechanism of action and activity in tumor cell lines were presented in a poster. Data presented at both the Keystone and TAT scientific meetings reported that SNS-314 is a selective and potent (IC50s in the low nanomolar range) inhibitor of Aurora kinases A, B, and C in vitro. In addition, SNS-314 was shown to have sustained exposure in tumor tissue, further supporting the compound's potential to differentiate its anti-tumor effects from effects on other proliferating tissues.

Discovered by Sunesis, SNS-314 is targeted to inhibit Aurora kinases thus halting cell division at the mitotic phase of the cell cycle and blocking the uncontrolled cellular proliferation associated with tumor growth. Aurora kinases have been detected at high levels in tumors from several cancer types, including colon, breast, ovarian, bladder, esophageal, gastric and pancreatic. Sunesis recently filed an Investigational New Drug Application with the U.S. Food and Drug Administration (FDA) for SNS-314 and the company expects to initiate a Phase 1 single-agent clinical trial in patients with advanced solid tumor malignancies in the first half of this year.

About Sunesis' Oncology Programs

Sunesis has built a rich portfolio of product candidates in oncology focused on novel pathways and targets, including inhibition of the cell-cycle and survival signaling. Sunesis is currently conducting Phase 2 clinical trials in lung and ovarian cancer and a Phase 1 clinical trial in acute myeloid leukemia for its lead compound, SNS-595. SNS-032, Sunesis' CDK inhibitor compound, is being evaluated in Phase 1 clinical trials in B-cell malignancies and in advanced solid tumors. SNS-314 is expected to begin Phase 1 clinical trials in the first half of 2007. In addition, Sunesis is developing novel small molecule inhibitors of Raf kinase and other oncology kinases in collaboration with Biogen Idec.

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 targeted cancer therapeutics. Sunesis is advancing its product candidates through in-house research and development efforts and strategic collaborations with leading pharmaceutical and biopharmaceutical companies.

Forward-Looking Statements

This press release may contain forward-looking statements that involve substantial risks and uncertainties. Sunesis may not actually achieve the plans, intentions or expectations contained in such forward-looking statements. Actual results or events could differ materially from the plans, intentions and expectations contained in such forward-looking statements. Sunesis does not assume any obligation to update any such forward-looking statements. For further information on Sunesis Pharmaceuticals, please visit http://www.sunesis.com.

SOURCE Sunesis Pharmaceuticals, Inc.

Eric Bjerkholt, SVP, Corp. Development & Finance of 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.
http://www.sunesis.com/

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