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Sunesis Commences Phase I Clinical Trial of SNS-032 for Cancer

01/31/06

SOUTH SAN FRANCISCO, California, January 31, 2006 -Sunesis Pharmaceuticals, Inc. announced today that patient treatment has commenced in a Phase I clinical trial of SNS-032. SNS-032 is a novel small molecule inhibitor of cyclin-dependent kinases (CDK) 2, 7 and 9. This is the company's second anti-cancer cell-cycle inhibitor to enter clinical trials.

The trial is an open-label, multi-center study designed to examine the safety and preliminary anti-tumor activity of SNS-032 and will enroll patients with advanced solid tumor cancers. Once a maximum-tolerated dose has been identified, enrollment will expand by 24 patients with lung cancer, breast cancer or melanoma. Patients will be enrolled at three centers in the United States.

"With the commencement of this trial, Sunesis continues to advance its portfolio of distinctive cell-cycle inhibitors with two product candidates now in clinical trials," said Dan Swisher, Chief Executive Officer of Sunesis. "In preclinical studies, SNS-032 demonstrated anti-tumor activity in multiple solid and hematological tumor models. We believe that CDKs 2, 7 and 9 are promising therapeutic targets for cancer therapy and we are hopeful that SNS-032 will prove to be a safe an efficacious novel cancer treatment."

About SNS-032

SNS-032 is a novel aminothiazole small molecule cell-cycle modulator that targets CDK2, CDK7 and CDK9, thus halting the uncontrolled cell division characteristic of cancer. Preclinical studies have shown that SNS-032 induces cell-cycle arrest and apoptosis (or cell death) across multiple cell lines. SNS-032 is a small molecule that is currently administered by IV infusion, but also has the potential to be developed as an oral formulation. In addition, the compound has the promise to be used as either a single agent or as part of a combination drug regimen. SNS-032 was in-licensed from Bristol-Myers Squibb (BMS) in April 2005

About Sunesis' Oncology Programs

Sunesis has built a portfolio of preclinical- and development-stage product candidates in oncology focused on novel pathways and targets, including inhibiting cell-cycle and survival signaling. In addition to SNS-032, Sunesis is currently conducting Phase II and Phase I clinical trials for its lead compound, SNS-595, a cell-cycle modulator that acts on proliferating cancer cells by inducing cell-cycle arrest and apoptosis. In addition, Sunesis' Aurora kinase inhibitor program is undergoing preclinical evaluation and, in cooperation with Biogen Idec, Sunesis is developing novel small molecule inhibitors of Raf kinase and other oncology kinases.

About Sunesis Pharmaceuticals

Sunesis is a clinical-stage biopharmaceutical company focused on the discovery, development and commercialization of small molecule therapeutics for oncology, inflammatory diseases and other unmet medical needs. Sunesis has built a product candidate portfolio through internal discovery and acquisition 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 further information, visit www.sunesis.com.

Forward-Looking Statements

This press release contains forward-looking statements concerning Sunesis Pharmaceuticals' and its product development plans, including plans to commence and conduct preclinical studies and clinical trials. Sunesis may not be successful in such plans.

Statements in this press release regarding Sunesis Pharmaceuticals' business which are not historical facts are "forward-looking statements" that involve risks and uncertainties. Forward-looking statements can be identified by, among other things, the use of forward-looking language, such as "anticipate," "believe," "could," "estimate," "expect," "future," "intends," "may," "plans," "should," "seeks," "potential," "will," or the negative of those terms, or other variations of those terms of comparable language, or by discussions of strategy or intentions. A number of important factors could cause actual results to differ materially from those projected or suggested in the forward-looking statements including, but not limited to, the ability of Sunesis to: (i) discover product candidates, (ii) successfully conduct preclinical studies and clinical trials of product candidates, (iii) obtain regulatory approval of any product candidates and (iv) obtain and enforce intellectual property rights. These statements speak only as of the date of this press release and the company assumes no obligation or responsibility to update or revise the statements.

SOURCE Sunesis Pharmaceuticals, Inc.  

investors, Eric Bjerkholt, CFO of Sunesis Pharmaceuticals, Inc., +1-650-266-3717; or
media, Karen L. Bergman or Michelle Corral, both of BCC Partners, +1-650-575-1509, or
+1-415-794-8662, for Sunesis Pharmaceuticals, Inc.