REGN4018: This phase I/II trial is trying to understand how safe a type of targeted drug therapy is in order to determine an appropriate amount to use alone or in combination with other drugs in the treatment of recurrent ovarian, fallopian tube or primary peritoneal cancerA Phase 1/2 Study of REGN4018 (A MUC16xCD3 Bispecific Antibody) Administered Alone or in Combination With Cemiplimab in Patients With Recurrent Ovarian Cancer

Inclusion

1. Ovarian Cancer Cohorts Only: Patients with histologically or cytologically confirmed diagnosis of advanced, epithelial ovarian cancer (except carcinosarcoma), primary peritoneal, or fallopian tube cancer who have all of the following:

   1. serum CA-125 level ≥2 x upper limit of normal (ULN) (in screening)
   2. has received at least 1 line of platinum-containing therapy or must be platinum-intolerant (applicable for dose escalation and non-randomized dose expansion cohorts)
   3. documented relapse or progression on or after the most recent line of therapy
   4. no standard therapy options likely to convey clinical benefit
2. Adequate organ and bone marrow function as defined in the protocol
3. Life expectancy of at least 3 months
4. Randomized phase 2 expansion cohort (Ovarian Cancer only): Platinum-resistant ovarian cancer patients who have had 1 to 3 lines of platinum-based therapy as defined in the protocol.

5. Endometrial Cancer Cohorts Only: histologically confirmed endometrial cancer that has progressed or recurrent after prior anti-Programmed Cell Death Ligand 1 (PD-1) therapy and platinum-based chemotherapy:

   1. MUC16 positivity of tumor cells ≥25% by immunohistochemistry (IHC)
   2. 1-2 prior lines of systemic therapy