Astex Pharmaceuticals Announces First Data Showing

DUBLIN, Calif., July 22, 2013 (GLOBE NEWSWIRE) -- Astex Pharmaceuticals, Inc. (Nasdaq: ASTX ), a pharmaceutical company dedicated to the discovery and development of novel small molecule therapeutics, today announced data demonstrating for the first time that early treatment with AT13387, a second generation, fully synthetic HSP90 inhibitor, in combination with targeted therapy delays the emergence of resistance. These results were presented at the 8 ^th World Congress of Melanoma July 17 to 20 in Hamburg, Germany.

In a preclinical model of mutant BRAF melanoma, animals were treated with vemurafenib alone or vemurafenib in combination with AT13387. After 2 to 4 months of continued treatment, tumor-bearing mice treated with vemurafenib alone showed the emergence of resistance and tumor regrowth while animals treated with the combination of vemurafenib and AT13387 did not show such regrowth. In addition, tumors that became resistant to vemurafenib alone were still sensitive to AT13387 treatment.

The poster presentation was among six posters awarded best poster award at the conference. These data support the early use of AT13387 in combination with targeted therapy to delay the emergence of resistance and prolong the duration of response and progression-free time. A clinical study of the combination of AT13387 with both BRAF and MEK inhibitors is being planned.

About AT13387

AT13387 is a small molecule inhibitor of HSP90. HSP90 is believed to support the growth and proliferation of many cancer cells. Acting as a "molecular chaperone," HSP90 stabilizes and prevents the breakdown of key oncogenic proteins.  These client proteins and their association with different tumor types include HER2 (the target for Herceptin® in breast cancer), the androgen receptor (the target for hormone therapy in prostate cancer), mutant B-raf (melanoma), c-kit (the target for Gleevec® in gastrointestinal tumors) and mutant EGFr (the target for Tarceva® and Iressa® in the treatment of non-small cell lung cancers).

Although AT13387 is a targeted inhibitor of HSP90, the functional role of HSP90 means the product has the potential to control the proliferation of multiple solid tumors and hematological malignancies where uncontrolled cell growth is dependent on the interaction between HSP90 and its client proteins. These include tumor types that have become resistant to initial therapy.

AT13387 is currently being studied in two phase 1/2 clinical trials, in ALK+ lung cancer in combination with crizotinib, and in castration resistant prostate cancer (or CRPC) in combination with abiraterone acetate.

In November 2009, Astex Pharmaceuticals entered into a CRADA with the US National Cancer Institute (NCI) to support the further clinical development of AT13387 over the next 5 years with a number of single agent and combination phase 1/2a and phase 2 studies planned.

AT13387 is wholly owned by Astex Pharmaceuticals.

About Astex Pharmaceuticals

Astex Pharmaceuticals is dedicated to the discovery and development of novel small molecule therapeutics with a focus on oncology. The Company is developing a proprietary pipeline of novel therapies and is creating de-risked products for partnership with leading pharmaceutical companies. Astex Pharmaceuticals developed and out-licensed DACOGEN® (decitabine) for Injection and receives significant royalties on global sales.

For more information about Astex Pharmaceuticals, Inc., please visit www.astx.com .

Forward-Looking Statements

This press release contains "forward-looking" statements within the meaning of Section 21A of the Securities Act of 1933, as amended, and Section 21E of the Securities Exchange Act of 1934, as amended, and is subject to the safe harbor created thereby. These statements are typically preceded by words such as "believes," "expects," "anticipates," "intends," "will," "may," "should," or similar expressions. Actual results could differ materially from those projected in the forward-looking statements as a result of a number of risks and uncertainties.  These forward-looking statements include, but are not limited to, expectations regarding the advancement of drug candidates in the clinic; the Company's ability to develop the current and future pipeline into commercially viable drugs; the expectations regarding our clinical trials including the timing of clinical proof of concept data from these trials. Important factors that could cause actual results to differ materially from the expectations reflected in the forward-looking statements include, but are not limited to: the outcomes of the on-going clinical trials; risks and uncertainties related to the research and development of AT13387.  References made to the discussion of risk factors are detailed in the Company's filings with the Securities and Exchange Commission including reports on its most recently filed Form 10-K and Form 10-Q.  These forward-looking statements are made only as of the date hereof, and we disclaim any obligation to update or revise the information contained in any such forward-looking statements, whether as a result of new information, future events or otherwise.

Timothy L. Enns Astex Pharmaceuticals, Inc. Senior Vice President Corporate Communications & Marketing Tel: +1 (925) 560-2810 E-mail: Susanna Chau Astex Pharmaceuticals, Inc. Manager Investor Relations Tel: +1 (925) 560-2845 E-mail: Alan Roemer The Trout Group Managing Director Tel: +1 (646) 378-2945 E-mail: