Inclusion Criteria:

          -  Men with histologically or cytologically confirmed adenocarcinoma of the prostate

          -  Prior treatment with one, and only one, NHT (eg, abiraterone, apalutamide,
             darolutamide, or enzalutamide) for castration-sensitive locally advanced (T3 or T4) or
             mCSPC, M0 CRPC, or mCRPC

          -  Surgical or medical castration, with serum testosterone ≤ 50 ng/dL (≤ 1.73 nmol/L) at
             screening

          -  Measurable (extrapelvic soft tissue) metastatic disease per Investigator assessment
             defined by at least one of the following: measurable visceral disease (eg, adrenal,
             kidney, liver, lung, pancreas, spleen) per RECIST 1.1; OR measurable extrapelvic
             adenopathy (ie, adenopathy above the aortic bifurcation)

          -  Progressive disease at study entry as defined by specific criteria for prostate
             specific antigen (PSA) progression OR soft tissue disease progression in the opinion
             of the Investigator (Note: subjects with bone disease progression alone are not
             eligible)

          -  Age ≥ 18 years old or meeting country definition of adult, whichever is older, on the
             day of consent

          -  ECOG performance status of 0 or 1

          -  Recovery to baseline or ≤ Grade 1 per Common Terminology Criteria for Adverse Events
             (CTCAE) v5 from toxicities related to any prior treatments, unless AE(s) are
             clinically nonsignificant and/or stable on supportive therapy in the opinion of the
             Investigator

          -  Adequate organ and marrow function based upon specific laboratory assessments obtained
             within 21 days prior to randomization

          -  Understanding and ability to comply with protocol requirements

        Exclusion Criteria:

          -  Any prior nonhormonal therapy initiated for the treatment of mCRPC

          -  Receipt of abiraterone within 1 week; cyproterone within 10 days; or flutamide,
             nilutamide, bicalutamide, enzalutamide, or other androgen-receptor inhibitors within 2
             weeks before randomization

          -  Radiation therapy within 4 weeks (2 weeks for bone metastases) prior to randomization
             (subjects with clinically relevant ongoing complications from prior radiation therapy
             are not eligible)

          -  Known brain metastases or cranial epidural disease unless adequately treated and
             clinically stable at least 4 weeks prior to randomization

          -  Symptomatic or impending spinal cord compression or cauda equina syndrome

          -  Concomitant anticoagulation with oral anticoagulants (some specific exceptions apply)

          -  Administration of a live, attenuated vaccine within 30 days prior to randomization

          -  Systematic treatment with, or any condition requiring, either corticosteroids (>10 mg
             daily prednisone equivalent) or other immunosuppressive medications within 14 days
             prior to randomization

          -  Uncontrolled, significant intercurrent or recent illness

          -  Major surgery within 4 weeks prior to randomization

          -  Corrected QT interval calculated by the Fridericia formula (QTcF) > 480 ms per ECG
             within 21 days before randomization

          -  Inability or unwillingness to swallow pills or receive IV administration

          -  Previously identified allergy or hypersensitivity to components of the study treatment
             formulations or history of severe infusion-related reactions to monoclonal antibodies

          -  Any other active malignancy at time of randomization or diagnosis of another
             malignancy within 2 years prior to randomization that requires active treatment (some
             exceptions apply such as locally curable cancers that have apparently been cured).