Prior hormone therapy is required. Patients must be hormone refractory and have discontinued anti-androgens for at least 4 weeks prior to study entry (at least 6 weeks for bicalutamide). Therapy with LHRH agonist must continue for those prostate cancer patients already receiving this treatment at the time of enrollment. If the patient has discontinued the LHRH agonist, this must be restarted (if not surgically castrated) and the castrate level of testosterone must be present. Prior therapy with CYP17 inhibitors (e.g. abiraterone, ketoconazole) or novel anti-androgens (e.g. MDV3100) is permitted.