Study of Abiraterone Acetate Without Exogenous Glucocorticoids in Men With Castration-resistant Prostate Cancer

Inclusion Criteria: * Participants must meet the following criteria on screening examination to be eligible to participate in the study: * Be a male ≥ 18 years of age. * Participants must have histologically or cytologically confirmed adenocarcinoma of the prostate without \>50% neuroendocrine differentiation or small cell histology. * Participants must have progressive disease as defined by one or more of the following: * Castrate resistant disease as defined by Prostate cancer working Group (PCWG).\[30\] Participants must have a rise in PSA on two successive determinations at least one week apart and PSA levels ≥ 2 ng/ml (only the screening PSA needs to be ≥ 2 ng/ml) and testosterone levels \< 50 ng/dL. * Soft tissue progression defined by Response Evaluation Criteria In Solid Tumors (RECIST) 1.1. * Bone disease progression defined by Prostate Cancer Clinical Trials Working Group 2 (PCWG2) with two or more new lesions on bone scan.\[30\] * Castration-resistant prostate cancer (CRPC) with metastatic disease with at least one site of metastatic disease must be amenable to needle biopsy. Soft tissue biopsy sites include: lymph node or visceral metastases. Bone sites include lumbar vertebrae, pelvic bones and long bones. Excluded sites are thoracic, cervical vertebrae, skull and rib lesions. Biopsy site will be selected with guidance of interventional radiologist determining best site to optimize balance of obtaining useful tissue for analysis and minimizing risk. * Participan…