DUBLIN, Calif., Sept. 10, 2012 (GLOBE NEWSWIRE) -- Astex Pharmaceuticals, Inc. (Nasdaq:ASTX), a pharmaceutical company dedicated to the discovery and development of novel small molecule therapeutics, announced that it has initiated a clinical trial with HSP90 inhibitor AT13387 in prostate cancer patients. The AT13387-04 study is a Phase 1-2, open label, randomized study in patients with castration-resistant prostate cancer (CRPC) who are no longer responding to treatment with standard of care therapies abiraterone acetate and steroids. CRPC patients who do not respond to abiraterone acetate and steroids currently have limited treatment options. In Part A (Phase 1) of the study, patients will continue to receive the same doses of abiraterone acetate and steroids received prior to entering the trial, and will be randomized to receive one of two different treatment regimens of AT13387 in combination with abiraterone acetate. Part A will enroll up to 52 patients and will establish safety of the combination, clinical activity, and confirm biological activity by monitoring depletion of androgen receptors in tumor and Circulating Tumor Cells (CTCs) samples following treatment with AT13387. The best combination regimen in Part A will then move forward to Part B (Phase 2) where patients will be randomized to receive either the selected treatment regimen and dose of AT13387 in combination with abiraterone acetate or AT13387 alone. Part B will enroll up to 112 patients. "We are extremely pleased with the initiation of our HSP90 inhibitor study in prostate cancer patients. With the incidence of prostate cancer in the U.S. at 215,000, and 28,000 deaths annually, this is a disease which is the second leading cause of cancer death among American men," said James S.J. Manuso, PhD, chairman & chief executive officer. "Despite developments in the treatment landscape, prostate cancer patients will continue to need new products, particularly ones that might be used in combination with other therapies, during the course of their disease."