Main Inclusion Criteria:

          -  Patient must have histologically confirmed, advanced (FIGO Stage III or IV) high-grade
             predominantly serous or endometrioid ovarian cancer, fallopian tube cancer, or primary
             peritoneal cancer who have completed first line platinum based chemotherapy
             (neoadjuvant or adjuvant)

          -  Patient must have clinical complete response or partial response following completion
             of chemotherapy course.

          -  All Stage IV patients are eligible, irrespective of residual disease, after primary or
             interval debulking. Stage III patients are required to have visible residual disease
             after primary surgery. Patients with inoperable Stage III and IV disease are eligible

          -  Patient must agree to undergo central tumor HRD testing

          -  Patients of childbearing potential must have negative pregnancy serum test within 72
             hours of being dosed

          -  Patient must be randomized within 12 weeks of the first day of the last cycle of
             chemotherapy

        Main Exclusion Criteria:

          -  Patient has mucinous or clear cell subtypes of epithelial ovarian cancer,
             carcinosarcoma or undifferentiated ovarian cancer

          -  Patient has undergone more than 2 debulking surgeries

          -  Patient is to receive bevacizumab as maintenance treatment

          -  Patient is pregnant, breastfeeding, or expecting to conceive children, while receiving
             study treatment and for 180 days after the last dose of study treatment

          -  Patient has had prior treatment with a known PARP inhibitor

          -  Patient has been diagnosed and/or treated for any invasive cancer (other than study
             disease) less than 5 years prior to study enrollment.