Study of REGN5678 (Anti-PSMAxCD28) With Cemiplimab (Anti-PD-1) in Patients With Metastatic Castration-resistant Prostate Cancer

Key Inclusion Criteria:

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

Metastatic, castration-resistant prostate cancer (mCRPC) with PSA value at screening

≥4 ng/mLthat has progressed within 6 months prior to screening as defined in the protocol

Has received ≥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 (eg, abiraterone, enzalutamide, apalutamide, or darolutamide)

Key Exclusion Criteria:

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
Has received any previous systemic biologic therapy within 5 half-lives of first dose of study therapy
Has received prior PSMA-targeting therapy
Dose Expansion Only: Has had prior anti-cancer immunotherapy
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
Ongoing or recent (within 5 years) evidence of significant autoimmune disease that required treatment with systemic immunosuppressive treatments
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
Uncontrolled infection with human immunodeficiency virus (HIV), hepatitis B or hepatitis C infection; or diagnosis of immunodeficiency

NOTE: Other protocol defined Inclusion/Exclusion Criteria apply