Study of Chemotherapy With Pembrolizumab (MK-3475) Followed by Maintenance With Olaparib (MK-7339) for the First-Line Treatment of Women With BRCA Non-mutated Advanced Epithelial Ovarian Cancer (EOC) (MK-7339-001/KEYLYNK-001/ENGOT-ov43/GOG-3036)

Inclusion Criteria:

• Has histologically confirmed International Federation of Gynecology and Obstetrics (FIGO) Stage III or Stage IV EOC (high-grade predominantly serous, endometrioid (anygrade), carcinosarcoma, mixed mullerian with high-grade serous component, clearcell, or low-grade serous OC), primary peritoneal cancer, or fallopian tube cancer

• Has just completed primary debulking surgery or is eligible for primary debulkingsurgery or is a potential candidate for interval debulking surgery

• Is a candidate for carboplatin and paclitaxel chemotherapy, to be administered inthe adjuvant or neoadjuvant setting

• Candidates for neoadjuvant chemotherapy, has a cancer antigen 125 (CA-125) (kilounits/L):carcinoembryonic antigen (CEA; ng/mL) ratio greater than or equal to 25

• Is able to provide a newly obtained core or excisional biopsy of a tumor lesion forprospective testing of BRCA1/2 and Programmed Cell Death-Ligand 1 (PD-L1) tumormarkers status prior to randomization

• Has an Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1, asassessed within 7 days prior to initiating chemotherapy in the lead-in period andwithin 3 days prior to Day 1 of Cycle 1

• Female participants are not pregnant, not breastfeeding, and at least 1 of thefollowing conditions applies: a.) Not a woman of childbearing potential (WOCBP) ORb.) Is a WOCBP and using a contraceptive method that is highly effective, with lowuser dependency, or be abstinent from heterosexual intercourse as their preferredand usual lifestyle, during the Treatment Period and for at least 120 days followingthe last dose of pembrolizumab (or pembrolizumab placebo) and bevacizumab (ifadministered), at least 180 days following the last dose of olaparib (or olaparibplacebo), and at least 210 days following the last dose of chemotherapy and agreesnot to donate eggs (ova, oocytes) to others or freeze/store for her own use for thepurpose of reproduction during this period. The investigator should evaluate thepotential for contraceptive method failure in relationship to the first dose ofstudy treatment. A WOCBP must have a negative highly sensitive pregnancy test withineither 24 hours (urine) or 72 hours (serum) before the first dose of studytreatment. If a urine test cannot be confirmed as negative, a serum pregnancy testis required. The investigator is responsible for review of medical history,menstrual history, and recent sexual activity to decrease the risk for inclusion ofa woman with an early undetected pregnancy. Contraceptive use by women should beconsistent with local regulations regarding the methods of contraception for thoseparticipating in clinical studies

• Has adequate organ function

Exclusion Criteria:

• Has mucinous, germ cell, or borderline tumor of the ovary

• Has a known or suspected deleterious mutation (germline or somatic) in either BRCA1or BRCA2

• Has a history of non-infectious pneumonitis that required treatment with steroids orcurrently has pneumonitis

• Has either myelodysplastic syndrome (MDS)/acute myeloid leukemia (AML) or hasfeatures suggestive of MDS/AML

• Has a known additional malignancy that is progressing or has required activetreatment in the last 3 years Note: Participants with basal cell carcinoma of theskin, squamous cell carcinoma of the skin, or carcinoma in situ (e.g. ductalcarcinoma in situ, cervical carcinoma in situ) that has undergone potentiallycurative therapy are not excluded.

• Has ongoing Grade 3 or Grade 4 toxicity, excluding alopecia, following chemotherapyadministered during the lead-in period

• Has known active central nervous system metastases and/or carcinomatous meningitis.Participants with brain metastases may participate provided they were previouslytreated (except with chemotherapy) and are radiologically stable, clinically stable,and no steroids were used for the management of symptoms related to brain metastaseswithin 14 days prior to randomization. Stable brain metastases should be establishedprior to the first dose of study medication lead-in chemotherapy

• Has a diagnosis of immunodeficiency or is receiving chronic systemic steroid therapy (dosing >10 mg daily of prednisone equivalent) or any other form ofimmunosuppressive therapy within 7 days prior to randomization

• Has an active autoimmune disease that has required systemic treatment in the past 2years (i.e., with use of disease modifying agents, corticosteroids orimmunosuppressive drugs) Note: Replacement therapy (e.g. thyroxine, insulin, orphysiologic corticosteroid replacement therapy for adrenal or pituitaryinsufficiency) is not considered a form of systemic treatment and is allowed.

• Has a known history of active tuberculosis (TB; Bacillus Tuberculosis)

• Has an active infection requiring systemic therapy

• Has received colony-stimulating factors (eg, granulocyte colony stimulating factor [G-CSF], granulocyte macrophage colony-stimulating factor [GM-CSF] or recombinanterythropoietin) within 4 weeks prior to receiving chemotherapy during the lead-inperiod

• Is considered to be of poor medical risk due to a serious, uncontrolled medicaldisorder, non-malignant systemic disease or active, uncontrolled infection

• Has had surgery to treat borderline tumors, early stage EOC, or early stagefallopian tube cancer <6 months prior to screening

• Has a known history of human immunodeficiency virus (HIV) infection

• 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] isdetected) infection. Testing for hepatitis B or hepatitis C is required at screeningonly if mandated by local health authority. Note: Participants with a history ofhepatitis B but who are HBsAg negative are eligible for the study

• Is either unable to swallow orally administered medication or has a gastrointestinal (GI) disorder affecting absorption (e.g. gastrectomy, partial bowel obstruction,malabsorption)

• Has uncontrolled hypertension

• Has current, clinically relevant bowel obstruction (including sub-occlusivedisease), abdominal fistula or GI perforation, related to underlying EOC (forparticipants receiving bevacizumab)

• Has a history of hemorrhage, hemoptysis or active GI bleeding within 6 months priorto randomization (for participants receiving bevacizumab)

• Is a WOCBP who has a positive urine pregnancy test within 72 hours before the firstdose of chemotherapy in the lead-in period and within 72 hours prior to Day 1 ofCycle 1, is pregnant or breastfeeding, or is expecting to conceive children withinthe projected duration of the study, starting with screening through 120 daysfollowing the last dose of pembrolizumab (or pembrolizumab placebo) and bevacizumab (if administered), at least 180 days following the last dose of olaparib (orolaparib placebo), and at least 210 days following the last dose of chemotherapy

• Has received prior treatment for any stage of OC, including radiation or systemicanti-cancer therapy (e.g. chemotherapy, hormonal therapy, immunotherapy,investigational therapy)

• Has received prior therapy with an anti-Programmed Cell Death-1 (anti-PD-1),anti-PD-L1, or anti-PD-L2 agent or with an agent directed to another stimulatory orco-inhibitory T-cell receptor (e.g. cytotoxic T lymphocyte antigen-4 [CTLA-4], OX 40, CD137)

• Has received prior therapy with either olaparib or any other poly(adenosine-ribose)polymerase (PARP) inhibitor

• Has intraperitoneal chemotherapy planned or has been administered as first-linetherapy

• Has received a live vaccine within 30 days prior to the first dose of studytreatment on Day 1 of Cycle 1

• Has severe hypersensitivity (≥Grade 3) to pembrolizumab, olaparib, carboplatin,paclitaxel or bevacizumab (if using) and/or any of their excipients

• Is currently receiving either strong (e.g. itraconazole, telithromycin,clarithromycin, protease inhibitors boosted with ritonavir or cobicistat, indinavir,saquinavir, nelfinavir, boceprevir, telaprevir) or moderate (eg, ciprofloxacin,erythromycin, diltiazem, fluconazole, verapamil) inhibitors of cytochrome P450 (CYP)3A4 that cannot be discontinued for the duration of the study

• Is currently receiving either strong (e.g. phenobarbital, phenytoin, rifampicin,rifabutin, rifapentine, carbamazepine, nevirapine, and St John's Wort) or moderate (e.g. bosentan, efavirenz, modafinil) inducers of CYP3A4 that cannot be discontinuedfor the duration of the study

• Is currently participating or has participated in a study of an investigationalagent or has used an investigational device within 4 weeks (28 days) of startingchemotherapy in the Lead-in Period

• Has resting electrocardiogram (ECG) indicating uncontrolled, potentially reversiblecardiac conditions or participant has congenital long QT syndrome

• Has had an allogenic tissue/solid organ transplant, has received previous allogenicbone-marrow transplant, or has received double umbilical cord transplantation

• Either has had major surgery within 3 weeks of randomization or has not recoveredfrom any effects of any major surgery