• 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:

‣ serum CA-125 level ≥2 x upper limit of normal (ULN) (in screening, not required for low-grade serous carcinoma)

⁃ 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)

⁃ documented relapse or progression on or after the most recent line of therapy

⁃ no standard therapy options likely to convey clinical benefit

• Adequate organ and bone marrow function as defined in the protocol

• Life expectancy of at least 3 months

• Randomized phase 2 expansion cohort (Ovarian Cancer only): Platinum-resistant ovarian cancer patients who have had 2 to 4 lines of platinum-based therapy as defined in the protocol.

• 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:

‣ MUC16 positivity of tumor cells ≥25% by immunohistochemistry (IHC), as defined in the protocol

⁃ 1-4 prior lines of systemic therapy, as described in the protocol