Phase 1/2 Study of REGN4336 (a PSMAxCD3 Bispecific Antibody) Administered Alone or in Combination with Cemiplimab in Patients with Metastatic Castration-Resistant 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