EPI-7386 in Combination with Enzalutamide Compared with Enzalutamide Alone in Subjects with MCRPC

This is a Phase 1/2 study of EPI-7386 orally administered in combination with enzalutamide in subjects with mCRPC. Phase 1 of the study will be a single-arm dose escalation study of EPI-7386 in combination with a fixed dose of enzalutamide. This portion of the study will primarily evaluate the safety and tolerability of the drug combination and establish the RP2CDs for EPI-7386 and enzalutamide when dosed in combination. In addition, blood sampling will be conducted for PK evaluation to assess the potential DDI between the two drugs. Once the RP2CD for each drug has been established, Phase 2 of the study will commence. Phase 2 is a two-arm, randomized (2:1), open-label study. Approximately 120 subjects will be randomized 2:1 to: * Group 1: EPI-7386 at the RP2CD + enzalutamide(depending on the results of the Phase 1) (n=80) * Group 2: Enzalutamide single agent (n=40) The planned dose of enzalutamide and EPI-7386 for the combination arm will be those determined in the Phase 1 of this study based on safety and exposure data. Subjects may remain on study treatment as long as they are tolerating treatment without disease progression based on RECIST v1.1 and/or PCWG3.