Ipilimumab in Combination With Androgen Suppression Therapy in Treating Patients With Metastatic Hormone-Resistant Prostate Cancer

PRIMARY OBJECTIVES: I. Proportion of patients who achieve an undetectable prostate-specific antigen (PSA) (=\< 0.2 ng/ml) after initiation of ipilimumab therapy. SECONDARY OBJECTIVES: I. Time to PSA progression. II. Time to progression by any measure. III. Maximum percentage of PSA reduction in each patient. IV. Number of patients with immune related adverse events (IRAEs) and correlation of these with complete PSA response, time to progression, and T cell measurements. V. Measures of T cell response to therapy with flow cytometry. VI. Response in measurable disease by modified Response Evaluation Criteria in Solid Tumors (RECIST) criteria. VII. Time to death from any cause. VIII. To examine correlative biomarkers and their relationship to clinical outcomes. Potential biomarkers include, but are not limited to C-reactive protein (CRP), insulin-like growth factor (IGF)-1 and -2, or follicle stimulating hormone (FSH). XV. Bank samples for future molecular correlative studies, biomarker, or other studies. OUTLINE: Patients receive ipilimumab intravenously (IV) over 90 minutes on day 1. Treatment repeats every 21 days for up to 4 courses in the absence of disease progression or unacceptable toxicity. Patients without progression then receive maintenance ipilimumab IV once every 3 months for 4 additional doses. After completion of study treatment, patients are followed up every 6 months for up to 5 years.