Overview

The primary objectives of the study are:

In the Dose Escalation Phase:

• To assess the safety, tolerability, and pharmacokinetics (PK) of REGN5668 alone and in separate combinations with cemiplimab or REGN4018, in order to determine a maximally tolerated dose(s) (MTD) or recommended phase 2 dose(s) (RP2D) of these combinations

In the Dose Expansion Phase:

• To assess the preliminary efficacy of REGN5668 in combination with cemiplimab or REGN4018, (separately by cohort and combination) as determined by the objective response rate (ORR) by Response Evaluation Criteria in Solid Tumors (RECIST) 1.1

The secondary objectives of the study are:

In the Dose Escalation Phase:

• To assess the preliminary efficacy of REGN5668 in combination with cemiplimab or REGN4018 (separately by cohort and combination) as determined by ORR by RECIST 1.1

In the Dose Expansion Phase:

• To characterize the safety profile in each expansion cohort
• To characterize the PK of REGN5668 in combination with cemiplimab or REGN4018 (separately by cohort and combination)

In both the Dose Escalation and Dose Expansion Phases:

• To assess preliminary efficacy of REGN5668 in combination with cemiplimab or REGN4018 (separately by cohort and combination) as measured by ORR based on immune based therapy RECIST (iRECIST), best overall response (BOR), duration of response (DOR), disease control rate (DCR), and progression-free survival (PFS) based on RECIST 1.1 and iRECIST
• To assess changes in CA-125 levels from baseline after treatment with REGN5668 in combinations with cemiplimab or REGN4018 (separately by cohort and combination)
• Immunogenicity of REGN5668, alone and in combinations with cemiplimab or REGN4018

Eligibility

Key Inclusion Criteria:

1. Has histologically or cytologically confirmed diagnosis of advanced epithelial ovarian cancer (except carcinosarcoma), primary peritoneal, or fallopian tube cancer that has received at least 1 line of platinum-based systemic therapy as defined in the protocol
2. Has a serum CA-125 level ≥2x ULN (in screening)
3. Has adequate organ and bone marrow function as defined in the protocol
4. Has an Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1.
5. Has a life expectancy of at least 3 months

Key Exclusion Criteria:

1. Prior anti-cancer immunotherapy as defined in the protocol
2. Recent treatment with anti-Programmed Cell Death (PD-1)/PDL-1 therapy
3. Has had another malignancy within the last 5 years that is progressing, requires active treatment, or has a high likelihood of recurrence as defined in the protocol
4. Prior treatment with a MUC16-targeted therapy
5. Expansion cohorts only: More than 3 prior lines of cytotoxic chemotherapy for platinum-experienced and/or intolerant disease
6. Has any condition that requires ongoing/continuous corticosteroid therapy as defined in the protocol within 1 week prior to the first dose of study drug
7. Has ongoing or recent (within 5 years) evidence of significant autoimmune disease that required treatment with systemic immunosuppressive treatments as defined in the protocol
8. Has untreated or active primary brain tumor, CNS metastases, leptomeningeal disease, or spinal cord compression as defined in the protocol
9. Has history of clinically significant cardiovascular disease as defined in the protocol

Note: Other protocol-defined Inclusion/Exclusion criteria apply