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)

Following a lead-in period during which all participants receive a single 3-week cycle of carboplatin/paclitaxel*, participants will be randomly assigned in to one of three treatment arms, and will receive carboplatin/paclitaxel* for 5 cycles plus:

* Pembrolizumab + Olaparib
* Pembrolizumab + Placebo for Olaparib
* Placebo for Pembrolizumab + Placebo for Olaparib

* At Investigator's discretion and prior to participant randomization, one of the following carboplatin/paclitaxel regimens is to be selected:

1. up to 5 cycles of carboplatin Area Under the Curve (AUC)5 or AUC6 AND paclitaxel 175 mg/m\^2 on Day 1 of each 3-week cycle
2. up to 5 cycles of carboplatin AUC5 or AUC6 on Day 1 of each 3-week cycle AND paclitaxel 80 mg/m\^2 on Days 1, 8 and 15 of each 3-week cycle; or
3. up to 5 cycles of carboplatin AUC2 or AUC2.7 AND paclitaxel 60 mg/m\^2 on Days 1, 8 and 15 of each 3-week cycle.

Docetaxel may be considered for participants who experience either a severe hypersensitivity reaction to paclitaxel or an AE requiring discontinuation of paclitaxel only after consultation with the Sponsor. The recommended dose as determined by the Scottish Gynaecological Cancer Trials Group is Docetaxel 75 mg/m\^2 Q3W plus carboplatin AUC 5 Q3W.

• Pembrolizumab (Biological), also known as MK-3475, KEYTRUDA®: IV infusion
• Placebo for pembrolizumab (Drug), also known as normal saline or dextrose: IV infusion
• Carboplatin (Drug), also known as PARAPLATIN®: IV infusion
• Paclitaxel (Drug), also known as TAXOL®: IV infusion
• Olaparib (Drug), also known as MK-7339, LYNPARZA®: Oral tablet
• Placebo for olaparib (Drug): Oral tablet
• Bevacizumab (Biological), also known as AVASTIN®: IV infusion
• Docetaxel (Drug): IV infusion

Primary outcomes

• Progression-Free Survival (PFS) Per Response Evaluation Criteria in Solid Tumors Version 1.1 (RECIST 1.1) as Assessed by the Investigator in Participants With Programmed Death-Ligand 1 (PD-L1) Positive Tumors (Combined Positive Score [CPS]≥10) [Up to approximately 67 months]: PFS is defined as the time from randomization to the first documented progressive disease (PD) per RECIST 1.1 based on Investigator assessment or death due to any cause, whichever occurs first. Per RECIST 1.1, PD is defined as ≥20% increase in the sum of diameters of target lesions. In addition to the relative increase of 20%, the sum must also demonstrate an absolute increase of ≥5 mm. Note: The appearance of one or more new lesions and the unequivocal progression of non-target lesions is also considered PD. The PFS per RECIST 1.1 as assessed by the Investigator will be reported for participants with PD-L1 positive tumors (CPS≥10). PFS was calculated using the product-limit (Kaplan-Meier) method for censored data.
• PFS Per RECIST 1.1 as Assessed by the Investigator in All Participants [Up to approximately 67 months]: PFS is defined as the time from randomization to the first documented progressive disease (PD) per RECIST 1.1 based on Investigator assessment or death due to any cause, whichever occurs first. Per RECIST 1.1, PD is defined as ≥20% increase in the sum of diameters of target lesions. In addition to the relative increase of 20%, the sum must also demonstrate an absolute increase of ≥5 mm. Note: The appearance of one or more new lesions and the unequivocal progression of non-target lesions is also considered PD. The PFS per RECIST 1.1 as assessed by the Investigator will be reported for all participants. PFS was calculated using the product-limit (Kaplan-Meier) method for censored data.

Secondary outcomes

• Overall Survival (OS) in Participants With PD-L1 Positive Tumors (CPS ≥ 10) [Up to approximately 67 months]: OS is defined as the time from the date of randomization to death due to any cause. The OS is reported for all participants with PD-L1 positive tumors (CPS≥10). The OS was calculated using the product-limit (Kaplan-Meier) method for censored data.
• OS in All Participants [Up to approximately 67 months]: OS is defined as the time from the date of randomization to death due to any cause. The OS was calculated using the product-limit (Kaplan-Meier) method for censored data.
• PFS Per RECIST 1.1 as Assessed by Blinded Independent Central Review (BICR) in Participants With PD-L1 Positive Tumors (CPS≥10) [Up to approximately 66 months]: PFS is defined as the time from randomization to the first documented disease progression per RECIST 1.1 based on blinded independent central review assessment or death due to any cause, whichever occurs first. Per RECIST 1.1, PD is defined as ≥20% increase in the sum of diameters of target lesions. In addition to the relative increase of 20%, the sum must also demonstrate an absolute increase of ≥5 mm. Note: The appearance of one or more new lesions and the unequivocal progression of non-target lesions is also considered PD. The PFS per RECIST 1.1 as assessed by blinded independent central review will be reported for participants with PD-L1 positive (CPS≥10) tumors (CPS≥10). PFS was calculated using the product-limit (Kaplan-Meier) method for censored data.
• PFS Per RECIST 1.1 as Assessed by BICR in All Participants [Up to approximately 66 months]: PFS is defined as the time from randomization to the first documented disease progression per RECIST 1.1 based on blinded independent central review assessment or death due to any cause, whichever occurs first. Per RECIST 1.1, PD is defined as ≥20% increase in the sum of diameters of target lesions. In addition to the relative increase of 20%, the sum must also demonstrate an absolute increase of ≥5 mm. Note: The appearance of one or more new lesions and the unequivocal progression of non-target lesions is also considered PD. The PFS per RECIST 1.1 as assessed by blinded independent central review will be reported for all participants. PFS was calculated using the product-limit (Kaplan-Meier) method for censored data.
• PFS After Second-line Treatment (PFS2) Following Discontinuation of Study Treatment as Assessed by the Investigator in Participants With PD-L1 Positive Tumors (CPS≥10) [Up to approximately 67 months]: PFS2 is defined as the time from randomization until PD after second-line treatment per RECIST 1.1 based on Investigator assessment, or death due to any cause, whichever occurs first. Per RECIST 1.1, PD is defined as ≥20% increase in the sum of diameters of target lesions. In addition to the relative increase of 20%, the sum must also demonstrate an absolute increase of ≥5 mm. Note: The appearance of one or more new lesions and the unequivocal progression of non-target lesions is also considered PD. The PFS2 per RECIST 1.1 as assessed by the Investigator is reported for participants with PD-L1 positive tumors (CPS≥10). PFS2 was calculated using the product-limit (Kaplan-Meier) method for censored data.
• PFS2 Following Discontinuation of Study Treatment as Assessed by the Investigator in All Participants [Up to approximately 67 months]: PFS2 is defined as the time from randomization until PD after second-line treatment per RECIST 1.1 based on Investigator assessment, or death due to any cause, whichever occurs first. Per RECIST 1.1, PD is defined as ≥20% increase in the sum of diameters of target lesions. In addition to the relative increase of 20%, the sum must also demonstrate an absolute increase of ≥5 mm. Note: The appearance of one or more new lesions and the unequivocal progression of non-target lesions is also considered PD. The PFS2 per RECIST 1.1 as assessed by the Investigator is reported for all participants. PFS2 was calculated using the product-limit (Kaplan-Meier) method for censored data.
• Change From Baseline in European Organisation for Research and Treatment of Cancer Quality of Life Questionnaire-Core 30 (EORTC QLQ-C30) Global Health Status (Item 29) and Quality of Life (Item 30) (GHS/QoL) Combined Score [Baseline and week 45]: The EORTC-QLQ-C30 is a 30-item questionnaire to assess the quality of life of cancer patients. Participant responses to the Global Health Status (GHS) question "How would you rate your overall health during the past week?" (Item 29) and the Quality of Life (QoL) question "How would you rate your overall quality of life during the past week?" (Item 30) were scored on a 7-point scale (1=Very Poor; 7=Excellent). Using linear transformation, raw scores were standardized so scores ranged from 0 to 100; higher score = better outcome. Change from baseline to Week 45 in EORTC QLQ-C30 Items 29 and 30 combined scores was calculated based on a constrained longitudinal data analysis (cLDA) with scores as response variable; covariates for treatment by time interaction and stratification factors (debulking surgery \[planned interval vs R0 following primary vs R1 following primary\], and bevacizumab use \[Yes vs No\], and PD-L1 CPS \[<10 vs ≥10\]).
• Mean Change From Baseline in Abdominal and Gastrointestinal (Abdominal/GI) Symptoms Score Using the EORTC Quality of Life Questionnaire-Ovarian Cancer (QLQ-OV28) Abdominal/GI Symptom Scale [Baseline and week 45]: Participant responses to 6 questions from the EORTC QoL Questionnaire-Ovarian Cancer (QLQ-OV28) abdominal/GI symptom scale about abdominal pain, bloated feeling in abdomen/stomach, changes in clothing fit, changes in bowel habit, flatulence, and stomach fullness when eating (questions 31-36) were scored on a 4-point scale (1=Not at all; 4=Very much); lower score = better abdominal/GI symptoms. Using linear transformation, raw scores were standardized so that scores ranged from 0 to 100; a lower score indicating a better overall outcome. Change from baseline to Week 45 in EORTC QLQ-OV28 Items 31-36 combined scores was calculated based on a constrained longitudinal data analysis (cLDA) model with scores as response variable; covariates for treatment by time interaction and stratification factors (debulking surgery \[planned interval vs R0 following primary vs R1 following primary\], and bevacizumab use \[Yes vs No\], and PD-L1 CPS \[<10 vs ≥10\]).
• Time to Deterioration (TTD) in European Organisation for Research and Treatment of Cancer (EORTC) Quality of Life Questionnaire-Core 30 (QLQ-C30) Global Health Status (Item 29) and Quality of Life (Item 30) Combined Score [Up to approximately 31 months]: The EORTC-QLQ-C30 is a 30-item questionnaire to assess the quality of life of cancer patients. Participant responses to the Global Health Status (GHS) question "How would you rate your overall health during the past week?" (Item 29) and the Quality of Life (QoL) question "How would you rate your overall quality of life during the past week?" (Item 30) were scored on a 7-point scale (1=Very Poor; 7=Excellent). Using linear transformation, raw scores were standardized so scores ranged from 0 to 100; higher score = better outcome. TTD is defined as the time from the first EORTC QLQ-C30 Items 29 and 30 combined scores to deterioration (defined as ≥10-point decrease in GHS/QoL score from baseline with confirmation under right-censoring rule \[the last observation\]) or death, whichever occurs first. TTD was calculated using the product-limit (Kaplan-Meier) method for censored data.
• Time to Deterioration (TTD) of Abdominal/GI Symptoms Using EORTC QLQ-OV28 [Up to approximately 31 months]: Participant responses to 6 questions from the EORTC QoL Questionnaire-Ovarian Cancer (QLQ-OV28) abdominal/GI symptom scale about abdominal pain, bloated feeling in abdomen/stomach, changes in clothing fit, changes in bowel habit, flatulence, and stomach fullness when eating (questions 31-36) were scored on a 4-point scale (1=Not at all; 4=Very much); lower score = better abdominal/GI symptoms. Using linear transformation, raw scores were standardized so that scores ranged from 0 to 100; a lower score indicating a better overall outcome. TTD is defined as the time from the first EORTC QLQ-OV28 questions 31-36 combined scores to deterioration (defined as ≥10-point decrease in abdominal/GI symptoms score from baseline with confirmation under right-censoring rule \[the last observation\]) or death, whichever occurs first. TTD was calculated using the product-limit (Kaplan-Meier) method for censored data.
• Time to First Subsequent Anti-cancer Treatment (TFST) in Participants With PD-L1 Positive Tumors (CPS≥10) [Up to approximately 67 months]: TFST is defined as the time from randomization to initiation of first subsequent anti-cancer treatment or death due to any cause, whichever occurs first. The TFST was determined from the product-limit (Kaplan-Meier) method for censored data.
• Time to First Subsequent Anti-cancer Treatment (TFST) in All Participants [Up to approximately 67 months]: TFST is defined as the time from randomization to initiation of first subsequent anti-cancer treatment or death due to any cause, whichever occurs first. The TFST was determined from the product-limit (Kaplan-Meier) method for censored data.
• Time to Second Subsequent Anti-cancer Treatment (TSST) in Participants With PD-L1 Positive Tumors (CPS≥10) [Up to approximately 67 months]: TSST is defined as the time from randomization to initiation of second subsequent anti-cancer treatment or death due to any cause, whichever occurs first. The TSST was determined from the product-limit (Kaplan-Meier) method for censored data.
• Time to Second Subsequent Anti-cancer Treatment (TSST) in All Participants [Up to approximately 67 months]: TSST is defined as the time from randomization to initiation of second subsequent anti-cancer treatment or death due to any cause, whichever occurs first. The TSST was determined from the product-limit (Kaplan-Meier) method for censored data.
• Time to Discontinuation of Study Treatment or Death (TDT) in Participants With PD-L1 Positive Tumors (CPS≥10) [Up to approximately 67 months]: TDT is defined as the time from the date of randomization to discontinuation of study treatment or death due to any cause, whichever occurs first. The TDT was determined from the product-limit (Kaplan-Meier) method for censored data.
• Time to Discontinuation of Study Treatment or Death (TDT) in All Participants [Up to approximately 67 months]: TDT is defined as the time from the date of randomization to discontinuation of study treatment or death due to any cause, whichever occurs first. The TDT was determined from the product-limit (Kaplan-Meier) method for censored data.
• Pathological Complete Response (pCR) Rate in Participants With PD-L1 Positive Tumors (CPS≥10) [Up to approximately 21 months]: pCR is defined as the disappearance of all known disease noted prior to surgery; all surgical specimens collected during the interval debulking surgery are microscopically negative for malignancy. The percentage of participants who experience pCR was determined based on Miettinen \& Nurminen method stratified by Bevacizumab use (yes versus no).
• Pathological Complete Response (pCR) Rate in All Participants [Up to approximately 26 months]: pCR is defined as the disappearance of all known disease noted prior to surgery; all surgical specimens collected during the interval debulking surgery are microscopically negative for malignancy. The percentage of participants who experience pCR was determined based on Miettinen \& Nurminen method stratified by Bevacizumab use (yes versus no) and PD-L1 status (CPS <10 versus CPS>=10).
• Number of Participants Who Experience an Adverse Event (AE) [Up to approximately 73 months (anticipated)]: An AE is any untoward medical occurrence in a participant, temporally associated with the use of study intervention, whether or not considered related to the study intervention. The number of participants who experience an AE will be reported.
• Number of Participants Who Discontinue Study Treatment Due to an AE [Up to approximately 6 years (anticipated)]: An AE is any untoward medical occurrence in a participant, temporally associated with the use of study intervention, whether or not considered related to the study intervention. The number of participants who discontinue study intervention due to an AE will be reported.

Sex: Female, ages: 18 Years to any

Inclusion Criteria:

* Has histologically confirmed International Federation of Gynecology and Obstetrics (FIGO) Stage III or Stage IV EOC (high-grade predominantly serous, endometrioid (any grade), carcinosarcoma, mixed mullerian with high-grade serous component, clear cell, or low-grade serous OC), primary peritoneal cancer, or fallopian tube cancer
* Has just completed primary debulking surgery or is eligible for primary debulking surgery or is a potential candidate for interval debulking surgery
* Is a candidate for carboplatin and paclitaxel chemotherapy, to be administered in the 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 for prospective testing of BRCA1/2 and Programmed Cell Death-Ligand 1 (PD-L1) tumor markers status prior to randomization
* Has an Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1, as assessed within 7 days prior to initiating chemotherapy in the lead-in period and within 3 days prior to Day 1 of Cycle 1
* Female participants are not pregnant, not breastfeeding, and at least 1 of the following conditions applies: a.) Not a woman of childbearing potential (WOCBP) OR b.) Is a WOCBP and using a contraceptive method that is highly effective, with low user dependency, or be abstinent from heterosexual intercourse as their preferred and usual lifestyle, during the Treatment Period and for at least 120 days following the last dose of pembrolizumab (or pembrolizumab placebo) and bevacizumab (if administered), at least 180 days following the last dose of olaparib (or olaparib placebo), and at least 210 days following the last dose of chemotherapy and agrees not to donate eggs (ova, oocytes) to others or freeze/store for her own use for the purpose of reproduction during this period. The investigator should evaluate the potential for contraceptive method failure in relationship to the first dose of study treatment. A WOCBP must have a negative highly sensitive pregnancy test within either 24 hours (urine) or 72 hours (serum) before the first dose of study treatment. If a urine test cannot be confirmed as negative, a serum pregnancy test is required. The investigator is responsible for review of medical history, menstrual history, and recent sexual activity to decrease the risk for inclusion of a woman with an early undetected pregnancy. Contraceptive use by women should be consistent with local regulations regarding the methods of contraception for those participating 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 BRCA1 or BRCA2
* Has a history of non-infectious pneumonitis that required treatment with steroids or currently has pneumonitis
* Has either myelodysplastic syndrome (MDS)/acute myeloid leukemia (AML) or has features suggestive of MDS/AML
* Has a known additional malignancy that is progressing or has required active treatment in the last 3 years Note: Participants with basal cell carcinoma of the skin, squamous cell carcinoma of the skin, or carcinoma in situ (e.g. ductal carcinoma in situ, cervical carcinoma in situ) that has undergone potentially curative therapy are not excluded.
* Has ongoing Grade 3 or Grade 4 toxicity, excluding alopecia, following chemotherapy administered 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 previously treated (except with chemotherapy) and are radiologically stable, clinically stable, and no steroids were used for the management of symptoms related to brain metastases within 14 days prior to randomization. Stable brain metastases should be established prior 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 of immunosuppressive therapy within 7 days prior to randomization
* Has an active autoimmune disease that has required systemic treatment in the past 2 years (i.e., with use of disease modifying agents, corticosteroids or immunosuppressive drugs) Note: Replacement therapy (e.g. thyroxine, insulin, or physiologic corticosteroid replacement therapy for adrenal or pituitary insufficiency) 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 recombinant erythropoietin) within 4 weeks prior to receiving chemotherapy during the lead-in period
* Is considered to be of poor medical risk due to a serious, uncontrolled medical disorder, non-malignant systemic disease or active, uncontrolled infection
* Has had surgery to treat borderline tumors, early stage EOC, or early stage fallopian 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 \[qualitative\] is detected) infection. Testing for hepatitis B or hepatitis C is required at screening only if mandated by local health authority. Note: Participants with a history of hepatitis 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-occlusive disease), abdominal fistula or GI perforation, related to underlying EOC (for participants receiving bevacizumab)
* Has a history of hemorrhage, hemoptysis or active GI bleeding within 6 months prior to randomization (for participants receiving bevacizumab)
* Is a WOCBP who has a positive urine pregnancy test within 72 hours before the first dose of chemotherapy in the lead-in period and within 72 hours prior to Day 1 of Cycle 1, is pregnant or breastfeeding, or is expecting to conceive children within the projected duration of the study, starting with screening through 120 days following the last dose of pembrolizumab (or pembrolizumab placebo) and bevacizumab (if administered), at least 180 days following the last dose of olaparib (or olaparib placebo), and at least 210 days following the last dose of chemotherapy
* Has received prior treatment for any stage of OC, including radiation or systemic anti-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 or co-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-line therapy
* Has received a live vaccine within 30 days prior to the first dose of study treatment 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 discontinued for the duration of the study
* Is currently participating or has participated in a study of an investigational agent or has used an investigational device within 4 weeks (28 days) of starting chemotherapy in the Lead-in Period
* Has resting electrocardiogram (ECG) indicating uncontrolled, potentially reversible cardiac conditions or participant has congenital long QT syndrome
* Has had an allogenic tissue/solid organ transplant, has received previous allogenic bone-marrow transplant, or has received double umbilical cord transplantation
* Either has had major surgery within 3 weeks of randomization or has not recovered from any effects of any major surgery

Participant flow

Outcome results

• Progression-Free Survival (PFS) Per Response Evaluation Criteria in Solid Tumors Version 1.1 (RECIST 1.1) as Assessed by the Investigator in Participants With Programmed Death-Ligand 1 (PD-L1) Positive Tumors (Combined Positive Score [CPS]≥10) (Primary), Median, Months: Carboplatin + Paclitaxel + Pembrolizumab + Olaparib 23.9 (21.0 to 30.2); Carboplatin + Paclitaxel + Pembrolizumab 17.3 (15.2 to 19.4); Carboplatin + Paclitaxel 15.2 (12.5 to 17.2) (p 0.0002)
• PFS Per RECIST 1.1 as Assessed by the Investigator in All Participants (Primary), Median, Months: Carboplatin + Paclitaxel + Pembrolizumab + Olaparib 22.2 (18.8 to 24.7); Carboplatin + Paclitaxel + Pembrolizumab 15.2 (13.6 to 16.4); Carboplatin + Paclitaxel 14.6 (12.7 to 16.3) (p <0.0001)
• Overall Survival (OS) in Participants With PD-L1 Positive Tumors (CPS ≥ 10) (Secondary), Median, Months: Carboplatin + Paclitaxel + Pembrolizumab + Olaparib 50.2 (43.9 to NA); Carboplatin + Paclitaxel + Pembrolizumab 56.4 (42.4 to NA); Carboplatin + Paclitaxel 51.6 (41.8 to NA) (p 0.4314)
• OS in All Participants (Secondary), Median, Months: Carboplatin + Paclitaxel + Pembrolizumab + Olaparib 47.7 (42.3 to 54.9); Carboplatin + Paclitaxel + Pembrolizumab 44.2 (38.1 to 52.2); Carboplatin + Paclitaxel 47.1 (41.7 to 60.9) (p 0.6716)
• PFS Per RECIST 1.1 as Assessed by Blinded Independent Central Review (BICR) in Participants With PD-L1 Positive Tumors (CPS≥10) (Secondary), Median, Months: Carboplatin + Paclitaxel + Pembrolizumab + Olaparib 42.0 (27.2 to 51.9); Carboplatin + Paclitaxel + Pembrolizumab 20.3 (17.3 to 27.4); Carboplatin + Paclitaxel 22.1 (15.4 to 29.5) (p 0.0012)
• PFS Per RECIST 1.1 as Assessed by BICR in All Participants (Secondary), Median, Months: Carboplatin + Paclitaxel + Pembrolizumab + Olaparib 30.1 (24.0 to 37.3); Carboplatin + Paclitaxel + Pembrolizumab 19.0 (16.6 to 22.2); Carboplatin + Paclitaxel 20.8 (16.9 to 25.3) (p 0.0008)
• PFS After Second-line Treatment (PFS2) Following Discontinuation of Study Treatment as Assessed by the Investigator in Participants With PD-L1 Positive Tumors (CPS≥10) (Secondary), Median, Months: Carboplatin + Paclitaxel + Pembrolizumab + Olaparib 41.1 (32.3 to 52.1); Carboplatin + Paclitaxel + Pembrolizumab 34.1 (29.0 to 41.2); Carboplatin + Paclitaxel 29.9 (25.3 to 37.6) (p 0.0228)
• PFS2 Following Discontinuation of Study Treatment as Assessed by the Investigator in All Participants (Secondary), Median, Months: Carboplatin + Paclitaxel + Pembrolizumab + Olaparib 33.1 (29.9 to 38.5); Carboplatin + Paclitaxel + Pembrolizumab 27.8 (26.0 to 32.5); Carboplatin + Paclitaxel 28.9 (25.4 to 34.2) (p 0.0573)
• Change From Baseline in European Organisation for Research and Treatment of Cancer Quality of Life Questionnaire-Core 30 (EORTC QLQ-C30) Global Health Status (Item 29) and Quality of Life (Item 30) (GHS/QoL) Combined Score (Secondary), Least squares mean, Score on a Scale: Carboplatin + Paclitaxel + Pembrolizumab + Olaparib 0.45 (-1.62 to 2.52); Carboplatin + Paclitaxel + Pembrolizumab ; Carboplatin + Paclitaxel 0.18 (-1.87 to 2.24) (p 0.8481)
• Mean Change From Baseline in Abdominal and Gastrointestinal (Abdominal/GI) Symptoms Score Using the EORTC Quality of Life Questionnaire-Ovarian Cancer (QLQ-OV28) Abdominal/GI Symptom Scale (Secondary), Least squares mean, Score on a Scale: Carboplatin + Paclitaxel + Pembrolizumab + Olaparib -2.63 (-4.40 to -0.85); Carboplatin + Paclitaxel + Pembrolizumab ; Carboplatin + Paclitaxel -2.77 (-4.54 to -1.00) (p 0.9024)
• Time to Deterioration (TTD) in European Organisation for Research and Treatment of Cancer (EORTC) Quality of Life Questionnaire-Core 30 (QLQ-C30) Global Health Status (Item 29) and Quality of Life (Item 30) Combined Score (Secondary), Median, Months: Carboplatin + Paclitaxel + Pembrolizumab + Olaparib NA (NA to NA); Carboplatin + Paclitaxel + Pembrolizumab NA (NA to NA); Carboplatin + Paclitaxel NA (NA to NA) (p 0.2644)
• Time to Deterioration (TTD) of Abdominal/GI Symptoms Using EORTC QLQ-OV28 (Secondary), Median, Months: Carboplatin + Paclitaxel + Pembrolizumab + Olaparib NA (NA to NA); Carboplatin + Paclitaxel + Pembrolizumab NA (NA to NA); Carboplatin + Paclitaxel NA (NA to NA) (p 0.5188)
• Time to First Subsequent Anti-cancer Treatment (TFST) in Participants With PD-L1 Positive Tumors (CPS≥10) (Secondary), Median, Months: Carboplatin + Paclitaxel + Pembrolizumab + Olaparib 29.3 (24.0 to 33.8); Carboplatin + Paclitaxel + Pembrolizumab 22.2 (17.7 to 25.4); Carboplatin + Paclitaxel 17.7 (14.1 to 21.4) (p <0.0001)
• Time to First Subsequent Anti-cancer Treatment (TFST) in All Participants (Secondary), Median, Months: Carboplatin + Paclitaxel + Pembrolizumab + Olaparib 24.9 (22.0 to 29.5); Carboplatin + Paclitaxel + Pembrolizumab 18.2 (16.8 to 21.0); Carboplatin + Paclitaxel 17.2 (15.3 to 19.0) (p <0.0001)
• Time to Second Subsequent Anti-cancer Treatment (TSST) in Participants With PD-L1 Positive Tumors (CPS≥10) (Secondary), Median, Months: Carboplatin + Paclitaxel + Pembrolizumab + Olaparib 43.9 (33.5 to 52.5); Carboplatin + Paclitaxel + Pembrolizumab 36.3 (31.9 to 42.8); Carboplatin + Paclitaxel 32.3 (27.5 to 39.2) (p 0.0316)
• Time to Second Subsequent Anti-cancer Treatment (TSST) in All Participants (Secondary), Median, Months: Carboplatin + Paclitaxel + Pembrolizumab + Olaparib 34.7 (31.3 to 40.4); Carboplatin + Paclitaxel + Pembrolizumab 31.3 (28.1 to 34.2); Carboplatin + Paclitaxel 30.9 (27.2 to 35.1) (p 0.0853)
• Time to Discontinuation of Study Treatment or Death (TDT) in Participants With PD-L1 Positive Tumors (CPS≥10) (Secondary), Median, Months: Carboplatin + Paclitaxel + Pembrolizumab + Olaparib 18.9 (14.9 to 22.4); Carboplatin + Paclitaxel + Pembrolizumab 15.3 (12.6 to 17.3); Carboplatin + Paclitaxel 15.3 (13.0 to 17.3) (p 0.1029)
• Time to Discontinuation of Study Treatment or Death (TDT) in All Participants (Secondary), Median, Months: Carboplatin + Paclitaxel + Pembrolizumab + Olaparib 17.7 (15.7 to 19.5); Carboplatin + Paclitaxel + Pembrolizumab 14.1 (12.4 to 15.4); Carboplatin + Paclitaxel 15.2 (13.6 to 16.6) (p 0.0442)
• Pathological Complete Response (pCR) Rate in Participants With PD-L1 Positive Tumors (CPS≥10) (Secondary), Number, Percentage of Participants: Pooled Carboplatin+Paclitaxel+Pembrolizumab+Olaparib, and Carboplatin+Paclitaxel+Pembrolizumab 9.8 (5.8 to 15.2); Carboplatin + Paclitaxel 4.5 (1.2 to 11.1) (p 0.0644)
• Pathological Complete Response (pCR) Rate in All Participants (Secondary), Number, Percentage of Participants: Pooled Carboplatin+Paclitaxel+Pembrolizumab+Olaparib, and Carboplatin+Paclitaxel+Pembrolizumab 5.9 (3.6 to 9.0); Carboplatin + Paclitaxel 2.3 (0.6 to 5.9) (p 0.0318)
• 2 more outcome measures not shown.

Adverse events

Time frame: Up to approximately 67 months

Serious adverse events by term

279 more terms not shown.

Other adverse events by term

4 more terms not shown.

127 more sites not listed.

• Results publication: Vergote I, Cibula D, Powell M, Laenen A, Nieuwenhuysen EV, Topuz S, Gonzalez-Martin A, Fujiwara K, Safina S, Bagameri A, Oliver M, Lee JY, Salutari V, Korach J, Lu CH, Madry R, Vulsteke C, Colombo N, Sehouli J, Klat J, Ruiz EY, Gilbert L, Pautier P, Pardo B, Kridelka F, Wei J, Toker S, Yamada K, Coleman RL; ENGOT-OV43/GOG-3036/KEYLYNK-001 investigators. Chemotherapy with or without pembrolizumab followed by maintenance pembrolizumab with or without olaparib as first-line treatment of patients with advanced BRCA non-mutated epithelial ovarian cancer (ENGOT-OV43/GOG-3036/KEYLYNK-001): a randomised, double-blind, placebo-controlled, phase 3 trial. Lancet Oncol. 2026 Sep 7:S1470-2045(26)00223-8. doi: 10.1016/S1470-2045(26)00223-8. Online ahead of print. PMID 42705254

• Study Protocol (PDF, 2025-08-19)
• Statistical Analysis Plan (PDF, 2023-01-05)

• Medical Director, Study director, Merck Sharp & Dohme LLC

NIH grants: 2018