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.