A Clinical Study of ONCT-534 in Subjects With Metastatic Castration-resistant Prostate Cancer.

This is a Phase 1/2 multi-center study to investigate the safety, tolerability, and anti-tumor acitivity of ONCT-534 in patients with relapsed or refractory metastatic castration-resistant prostate cancer. The study consists of 2 phases: a Phase 1 Dose Escalation and a Phase 2 Dose Expansion. * During the dose escalation in Phase 1 a group of participants will be assigned a certain dose level. Once the dose level is considered safe, the next group will be assigned a higher dose level. The dose level may be raised or lowered depending on any safety events that occur throughout Phase 1. There will be approximately 27 participants enrolled in Phase 1. At the end of Phase 1, two dose levels will be chosen to be tested in Phase 2. * During Phase 2, participants will be randomly assigned to 1 of the 2 dose levels chose in Phase 1. Approximately 16 participants will be enrolled in each of the 2 dose level groups, for a total of 32 participants.