REGN15505 (PSMAx4-1BB) Alone or in Combination With Cemiplimab or REGN4336 (PSMAxCD3) in Adult Patients With Metastatic Castration-Resistant Prostate Cancer and Clear Cell Renal Cell Carcinoma

Key Inclusion Criteria:

Participants with mCRPC:

1. Men with histologically or cytologically confirmed adenocarcinoma of the prostate without pure small cell carcinoma
2. mCRPC with PSA value at screening ≥4 ng/mL and that has progressed within 6 months prior to screening as described in the protocol
3. Has received ≥2 lines of prior systemic therapy approved in the metastatic and/or castration-resistant setting as described in the protocol
4. Have had either Orchiectomy or be on Luteinizing Hormone-Releasing Hormone (LHRH) agonist or antagonist therapy with serum testosterone \<50 ng/dL AND agree to stay on LHRH agonist or antagonist therapy during the study

   Participants with ccRCC:
5. Men and women with histologically or cytologically confirmed Renal Cell Carcinoma (RCC) with a clear-cell component
6. Diagnosis of metastatic ccRCC with at least 1 measurable lesion via Response evaluation criteria in solid tumors (RECIST) 1.1 criteria
7. Has progressed on or after ≥1 line of prior systemic therapy approved in the metastatic setting. Prior treatment must include an Anti Program Cell Death 1 (PD-1)/ Program Death Ligand 1 (PD-L1) therapy and either ipilimumab and/or a Tyrosine Kinase Inhibitor (TKI)

Key Exclusion Criteria:

For Both mCRPC and ccRCC Cohorts:

1. Has received treatment with an approved systemic therapy (including sipuleucel-T for mCRPC patients) within 3 weeks of dosing or has not yet recovered (ie, grade ≤1 or baseline) from any acute toxicities except for laboratory changes as described in the protocol

   mCRPC Cohort Only:
2. Has received prior Prostate Specific Membrane Antigen (PSMA)-targeting therapy with the exception of a PSMA-targeting radioligand (eg, 177Lu-PSMA-617)

Note: Other protocol defined inclusion/exclusion criteria apply