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 withoutpure 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 ofthe following:

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

4. Radiographic disease progression in soft tissue based on Response EvaluationCriteria in Solid Tumors (RECIST) version 1.1 criteria with or without PSAprogression

5. Radiographic disease progression in bone defined as the appearance of 2 or morenew bone lesions on bone scan with or without PSA progression NOTE: Measurabledisease per RECIST version 1.1 per local reading at screening is not aneligibility criterion for enrollment

6. Has progressed upon or intolerant to ≥2 lines prior systemic therapy approved in themetastatic and/or castration-resistant setting (in addition to androgen deprivationtherapy [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 orhas not yet recovered (ie, grade ≤1 or baseline) from any acute toxicities

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

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

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

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

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

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

NOTE: Other protocol defined Inclusion/Exclusion Criteria apply