Additional information about the study can be found online at clinicaltrials.gov: http://clinicaltrials.gov/ct2/show/NCT01712217About AT13387 AT13387 is a small molecule inhibitor of HSP90, a heat shock protein believed to be responsible for supporting the development of cancer in many tumor cells. HSP90 acts as a "molecular chaperone," stabilizing and preventing the breakdown of key oncogenic proteins. These client proteins, including HER2 (the target for Herceptin® in the treatment of breast cancer), androgen (the target for Zytiga® in prostate cancer), mutant B-raf (the target for Zelboraf® in melanoma), ALK (the target for Xalkori® in lung cancer), 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) are associated with different tumor types. Although AT13387 is a targeted inhibitor of HSP90, it 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. Astex Pharmaceuticals has an ongoing Phase 2 study in patients with refractory gastrointestinal stromal tumors (GIST) and a Phase 2 trial in patients with castration-resistant prostate cancer (CRPC) who are no longer responding to treatment with the standard of care therapies, abiraterone acetate and steroids. 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. The CRADA will enable a number of single agent and combination Phase 1/2a and Phase 2 studies. AT13387, a proprietary compound, 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 Dacogen® (decitabine) for Injection and receives significant royalties on global sales.