Phase 2 is an open-label, multi-center cohort-expansion study to further determine the efficacy and safety of seviteronel in two CRPC populations with documented rising PSA with or without bone or soft tissue disease progression during treatment with: abiraterone or enzalutamide for ≥ 12 weeks (Group 1) abiraterone and enzalutamide; treatment should be ≥ 12 weeks for at least one agent (Group 2)