Vudalimab (XmAb20717) in Combination With Standard of Care Treatment in Patients With Metastatic Castration Sensitive Prostate Cancer

PRIMARY OBJECTIVE: I. To determine the safety and tolerability of vudalimab (XmAb20717) in combination with standard of care treatment in subjects with metastatic castration sensitive prostate cancer (mCSPC) as assessed by frequency and intensity of adverse events. SECONDARY OBJECTIVE: I. To assess the preliminary antitumor activity of vudalimab (XmAb20717) with standard of care treatment. TERTIARY/EXPLORATORY OBJECTIVE: I. To identify factors that may be indicative of response to vudalimab (XmAb20717) in combination with standard of care treatments. OUTLINE: Patients are assigned to 1 of 3 cohorts. COHORT A: Patients receive vudalimab intravenously (IV) on days 1 and 15 plus abiraterone orally (PO) once daily (QD) of 4-week cycles on study. Patients also undergo prostate-specific membrane antigen (PSMA) positron emission tomography (PET) and fludeoxyglucose (FDG) PET scans during screening. Patients also undergo computed tomography (CT) and/or magnetic resonance imaging (MRI) scans, bone scans, and blood sample collection throughout the study. COHORT B: Patients receive vudalimab IV on days 1 and 15 plus enzalutamide PO QD of 4-week cycles on study. Patients also undergo PSMA PET and FDG PET scans during screening. Patients also undergo CT and/or MRI scans, bone scans, and blood sample collection throughout the study. COHORT C: Patients receive vudalimab IV on days 1 and 15, docetaxel IV on days 1 and 22 plus abiraterone PO QD of 6-week cycles on study. Patients also undergo PSMA PET and FDG PET scans during screening. Patients also undergo CT and/or MRI scans, bone scans, and blood sample collection throughout the study.