 - Rising Prostate-specific antigen PSA after initial response to enzalutamide or abiraterone without radiographic or symptomatic evidence of progression per Prostate Cancer Working Group 2 criteria: Most recent enzalutamide dose received is 160 milligram mg once daily with no change in dose for at least 4 weeks prior to Cycle 1, Day 1. Most recent abiraterone dose received is 1000 mg once daily with prednisone 5 mg twice daily BID, with no change in dose for at least 2 weeks prior to Cycle 1, Day 1. 