Inclusion Criteria:  Age ≥18 years Male patients with histologically or cytologically confirmed adenocarcinoma of the prostate with no evidence of small cell or neuroendocrine features Metastatic disease with limited therapeutic options, prior treatment with at least one next-generation hormonal agent (e.g., abiraterone, enzalutamide, apalutamide, darolutamide) and one taxane line of treatment is allowed Progressive disease is defined as rising prostate-specific antigen (PSA) levels ≥2ng/mL and/or radiographic progression according to Prostate Cancer Working Group 3 (PCWG3) criteria at screening Able and willing to comply with all study requirements for the duration of the study Patients must sign an ICF prior to the start of any study-related procedures  Exclusion Criteria:  Anti-tumor therapy (chemotherapy, antibody therapy, molecular targeted therapy) within 28 days prior to starting study treatment Uncontrolled intercurrent illness such as active infection, symptomatic congestive heart failure, unstable angina pectoris, cardiac arrhythmia, uncontrolled hypertension, or psychiatric illness/social situations that would limit compliance with the study protocol Malignancy within the previous 2 years with a ≥30% probability of recurrence within 12 months, with the exception of non-melanoma skin cancer or superficial bladder cancer Patients receiving strong inhibitors or inducers of cytochrome P450 (CYP) 3A4 Chronic use of systemic steroid therapy (>1 month of >10 mg prednisone per day or equivalent, except replacement therapy) Patients for whom biopsies cannot be taken or are not willing to undergo biopsies Positive hepatitis B virus (HBV) surface antigen, hepatitis B core antibody, positive hepatitis C virus (HCV) antibody, and/or HIV-antigen-antibody test at screening