A Trial to Find Out if REGN4336 is Safe and How Well it Works Alone and in Combination With Cemiplimab or REGN5678 for Adult Participants With Advanced Prostate Cancer

Key Inclusion Criteria:

   1. Histologically or cytologically confirmed adenocarcinoma of the prostate without pure
   small cell carcinoma

   2. Metastatic, castration-resistant prostate cancer (mCRPC) with PSA value at screening
   ≥4 ng/mL that has progressed within 6 months prior to screening, according to 1 of the
   following:

      1. PSA progression as defined by a rising PSA level confirmed with an interval of ≥1
      week between each assessment

      2. Radiographic disease progression in soft tissue based on Response Evaluation
      Criteria in Solid Tumors (RECIST) version 1.1 criteria with or without PSA
      progression

      3. Radiographic disease progression in bone defined as the appearance of 2 or more
      new bone lesions on bone scan with or without PSA progression NOTE: Measurable
      disease per RECIST version 1.1 per local reading at screening is not an
      eligibility criterion for enrollment

   3. Has progressed upon or intolerant to ≥2 lines prior systemic therapy approved in the
   metastatic and/or castration-resistant setting (in addition to androgen deprivation
   therapy [ADT]) including at least one second-generation anti-androgen therapy (e.g.
   abiraterone, enzalutamide, apalutamide, or darolutamide)

Key Exclusion Criteria:

   1. Has received treatment with an approved systemic therapy within 3 weeks of dosing or
   has not yet recovered (ie, grade ≤1 or baseline) from any acute toxicities

   2. Has received any previous systemic biologic or immune-modulating therapy (except for
   Sipuleucel-T) within 5 half-lives of first dose of study therapy, as described in the
   protocol

   3. Has received prior PSMA-targeting therapy. Exception: Prior therapy with approved
   PSMA-targeted radioligand(s) is permitted

   4. Any condition that requires ongoing/continuous corticosteroid therapy (>10 mg
   prednisone/day or anti-inflammatory equivalent) within 1 week prior to the first dose
   of study therapy

   5. Ongoing or recent (within 5 years) evidence of significant autoimmune disease that
   required treatment with systemic immunosuppressive treatments

   6. Encephalitis, meningitis, neurodegenerative disease (with the exception of mild
   dementia that does not interfere with activities of daily living [ADLs]) or
   uncontrolled seizures in the year prior to first dose of study therapy

   7. Uncontrolled infection with human immunodeficiency virus (HIV), hepatitis B or
   hepatitis C infection; or diagnosis of immunodeficiency, as described in the protocol.

NOTE: Other protocol defined Inclusion/Exclusion Criteria apply