The purpose of this study is to establish the safety profile of oral (by mouth) abiraterone acetate and oral prednisone following short-term administration after standardized low-fat or high-fat meals to patients with metastatic (spreading) castration-resistant prostate cancer (mCRPC).

This is a multicenter, open-label study of 24 (up to a total of 28) men to assess the short-term safety of oral abiraterone acetate 1 g and oral prednisone 5 mg twice daily administered in the modified fasted state and after meals of various fat contents. All patients will take daily abiraterone acetate for the first 7 days in the modified fasted state (no food for 2 hours before and 1 hour after the dose). In Cohort 1, up to 6 evaluable patients will take abiraterone acetate daily for 7 days after a standardized low-fat meal from Cycle 1 Day 8 to Cycle 1 Day 14; or, in Cohort 2, up to 6 evaluable patients will take abiraterone acetate daily for 7 days after a standardized high-fat meal from Cycle 1 Day 8 to Cycle 1 Day 14. All patients will then continue to take abiraterone acetate daily in the modified fasted state starting on Cycle 1 Day 15 until disease progression. Toxicity related to dosing after the low-fat or high-fat meals is defined as Grade 3 or higher AEs of special interest; or Grade 3 or higher serious adverse events (SAEs) that occur during the food safety evaluation period. Cohort 2 may be expanded to a total of 18 evaluable patients if deemed to be safe. Decisions regarding the escalation of cohort or expansion of cohorts will be made by a study evaluation team. Pharmacokinetic evaluation for each cohort will be performed on Cycle 1 Days 7 and 14 at predose and multiple timepoints postdose over 24 hours; Cycle 1 Days 8 and 11 at 2 hours following abiraterone acetate dose administration. Abiraterone acetate, 1 g (four 250-mg tablets) orally (taken by mouth) once daily. Patients may take abiraterone acetate until progression of clinical disease. Prednisone, 5 mg, orally, twice a day.

Inclusion Criteria:

• Adenocarcinoma of the prostate
• Metastatic disease documented by bone, computed tomography (CT) or magnetic resonance imaging (MRI) scan
• Surgical or medical castration with testosterone less than 50 ng/dL (< 2.0 nM)
• Prostate-specific antigen (PSA) or radiographic progression documented by assessments specified in study protocol
• Platelets >100,000/µl
• Hemoglobin >=9.0 g/dL
• Liver function tests (LFTs): Serum bilirubin < 1.5 x ULN; AST or ALT < 2.5 x ULN; Eastern Cooperative Oncology Group (ECOG) status score of <=2

Exclusion Criteria:

• Small cell carcinoma of the prostate
• Known brain metastasis, chronic liver disease with elevated LFTs
• Prior cytotoxic chemotherapy for metastatic prostate cancer
• Treatment of prostate cancer within 30 days of Day 1 Cycle 1 with surgery, radiation, chemotherapy or immunotherapy
• Use of investigational drug within 30 days of Day 1 Cycle 1 or current enrollment in an investigational drug or device study
• Recent history of ischemic heart disease, Electrocardiogram (ECG) abnormalities or atrial fibrillation
• Active infection or other medical condition that would make prednisone (corticosteroid) use contraindicated
• Chronic medical condition requiring a higher dose of corticosteroid than prednisone 5 mg twice daily