An Open-label Dose Escalation and Expansion, Followed by a Phase II Study of Tulmimetostat (DZR123) and JSB462 (Luxdegalutamide) in Patients With Progressive Metastatic Castrate Resistant Prostate Cancer (mCRPC) (TulmiSTAR-01)

Key Inclusion Criteria: * Participant is an adult man ≥ 18 years of age. * Participant must have histologically and/or cytologically confirmed adenocarcinoma of the prostate without neuroendocrine or small cell features (current or prior biopsy of the prostate and/or metastatic site). * Participant must have ≥ 1 metastatic lesion that is present on screening/baseline CT, MRI, or bone scan imaging obtained ≤ 28 days prior to start of treatment (Part 1a dose escalation) or randomization (Part 1b dose expansion and Part 2). * Participant must have progressive mCRPC. * Participant must have a castrate level of serum/plasma testosterone (\< 50 ng/dL or \< 1.7 nmol/L). * Prior ARPI therapy: * Part 1a and 1b only: must have progressed on at least one prior second generation ARPI (abiraterone, enzalutamide, darolutamide, or apalutamide). * Part 2 only: must have progressed on one prior second generation ARPI (abiraterone, enzalutamide, darolutamide, or apalutamide). * Prior chemotherapy: * Part 1a dose escalation only: may have received ≤ 2 prior lines of chemotherapy in CRPC setting. Note: Prior chemotherapy is permitted in the HSPC setting. * Part 1b dose expansion/optimization only: may have received up to one prior line of chemotherapy in CRPC setting. Note: Prior chemotherapy is permitted in the HSPC setting. * Part 2 only: Participants must be taxane-naïve in mCRPC setting; prior chemotherapy permitted in HSPC setting only Key Exclusion Criteria: * Previous treat…