Olaparib Maintenance With Pembrolizumab & Bevacizumab in BRCA Non-mutated Patients With Platinum-sensitive Recurrent Ovarian Cancer

Inclusion Criteria: * Participant has histologically confirmed diagnosis of high-grade predominantly serous, endometrioid, carcinosarcoma, mixed mullerian with high-grade serous component, clear cell, or low-grade serous OC, primary peritoneal cancer, or fallopian tube cancer will be enrolled in this study (only up to 8 patients with clear cell carcinoma will be included and mucinous carcinoma will not be included). * Participant has received 2 previous courses of platinum-containing therapy, and has disease that was considered platinum sensitive following the penultimate (next to last) platinum course (more than 6 months' period between penultimate platinum regimen and progression of disease * Participant has responded to last the platinum regimen (complete or partial response), remains in response and is enrolled on study within 8 weeks of completion of the last platinum regimen * Participant is able to provide a newly obtained core or excisional biopsy of a tumor lesion for prospective testing of BRCA 1/2 and PD-L1 status prior to enrollment * Female participants who are at least 20 years of age and Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1 * Participant has adequate organ function as defined in the following: 1. ANC≥1500/µL 2. PLT≥100 000/µL 3. Hemoglobin≥9.0 g/dL or ≥5.6 mmol/L 4. Creatinine≤1.5 × ULN or calculated creatinine clearance≥30 mL/min for participant with creatinine levels \>1.5 × institutional ULN 5. Total bilirubin≤1.5 ×ULN OR direct bilirubin ≤ULN for participants with total bilirubin levels \>1.5 × ULN 6. AST (SGOT) and ALT (SGPT)≤2.5 × ULN (≤5 × ULN for participants with liver metastases) 7. International normalized ratio (INR) OR prothrombin time (PT), Activated partial thromboplastin time (aPTT)≤1.5 × ULN unless participant is receiving anticoagulant therapy as long as PT or aPTT is within therapeutic range of intended use of anticoagulants Exclusion Criteria: * Participant has mucinous, germ cell, or borderline tumor of the ovary * Participant has a known or suspected deleterious mutation (germline or somatic) in either BRCA1 or BRCA2 * Participant has a history of non-infectious pneumonitis that required treatment with steroids or currently has pneumonitis * Participant either has myelodysplastic syndrome (MDS)/ acute myeloid leukemia (AML) or has features suggestive of MDS/AML * Participant has a known additional malignancy that is progressing or has required active treatment within the past 3 years * Participant has known active CNS metastases and/or carcinomatous meningitis * Participant has a known history of active TB (Bacillus Tuberculosis) * Participant has a known history of Hepatitis B (defined as Hepatitis B surface antigen \[HBsAg\] reactive) or known active Hepatitis C virus (defined as HCV RNA \[qualitative\] is detected) infection * Participant has uncontrolled hypertension, defined as systolic \> 140 mmHg or diastolic \> 90 mmHg documented by 2 blood pressure readings taken at least 1 hour apart * Participant has a history of hemorrhage, hemoptysis or active gastrointestinal bleeding within 6 months prior to randomization