A Phase 2 Open-Label, Single-Arm Study to Evaluate the Efficacy and Safety of the Combination of Niraparib and Dostarlimab (TSR-042) in Patients With Platinum-Resistant Ovarian Cancer (MOONSTONE)

• Participant must be female \>=18 years of age, able to understand the study procedures, and subsequently agreed to participate in the study by providing written informed consent.

• Participants must have recurrent high-grade serous, endometrioid, or clear cell ovarian, fallopian tube, or primary peritoneal cancer.

• Participants must be considered resistant to the last administered platinum therapy.

• Participants must have completed at least 1 but no more than 3 prior lines of therapy for advanced or metastatic ovarian cancer.

• Participants must have been previously treated with platinum-based regimen, taxane agent(s), and bevacizumab.

• Participant has measurable disease according to RECIST v.1.1.

• Participant has an Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1.

• Participant has adequate organ function.

• Females with childbearing potential have a serum pregnancy test that is negative 72 prior first dose and are not breastfeeding. Participant must also agree to abstain from activities that could result in pregnancy from enrollment through 180 days after the last dose of study treatment.

• Participant must provide formalin fixed paraffin embedded (FFPE) tumor tissue block(s) with sufficient tumor content (as confirmed by the Sponsor's designated central laboratory) during screening to enable BRCA testing and PD-L1 testing. The use of slides created from paraffin-embedded tissue as opposed to FFPE blocks must be approved by the Sponsor.

• Participant must agree to complete health-related quality of life (HRQoL) questionnaires throughout the study.