D9319C00001- 1L OC Mono Global RCT

Key Inclusion Criteria:

1. Participants must be ≥18 years at the time of (pre-)screening

2. Histological and staging criteria:Female participants who must have histologicallynewly diagnosed high-grade serous or high-grade endometrioid ovarian cancer,fallopian tube cancer, or primary peritoneal cancer that is Stage III or IVaccording to the International FIGO 2014.

3. Participants are eligible if they fulfil any of the following surgical criteria:

• Stage III: primary debulking surgery with macroscopic residual diseasepost-surgery, neoadjuvant chemotherapy, or inoperable.

• Stage IV: primary debulking surgery regardless of residual disease, neoadjuvantchemotherapy, or inoperable.

4. Chemotherapy criteria:

• Participants must have received platinum-based chemotherapy consisting of aminimum of 6 treatment cycles and a maximum of 9, however, if platinum-basedtherapy must be discontinued early as a result of toxicities specificallyrelated to the platinum regimen, participants must have received a minimum of 4cycles of the platinum regimen.

• Participants must have, in the opinion of the investigator, clinical CR or PRas per RECIST 1.1 criteria with no measurable lesion > 2 cm on thepost-treatment scan and have no clinical evidence of disease progression or arising CA-125 level (see inclusion criterion 5), following completion of thischemotherapy course.

• A participant who received interval debulking surgery must have had ≥ 2postoperative cycles of platinum-based therapy.

5. Participants must meet one of the criteria specified below for pre-treatment CA-125measurements as follows:

• CA-125 in the normal range or

• CA-125 decrease by ≥ 90% during their front-line therapy that is stable for atleast 7 days (ie, no increase > 15% from nadir). During screening, if the firstCA-125 value is greater than the upper limit of normal (ULN), a secondassessment must be performed at least 7 days after the first. If the secondassessment is > 15% more than the first value, the participant is noteligible).

6. Participants should not have received bevacizumab with first-line chemotherapy or beplanned to receive bevacizumab maintenance therapy.

7. Participants must be randomised within a maximum of 12 weeks from the last day ofchemotherapy infusion (but no earlier than 3 weeks).

8. ECOG performance status of 0 or 1 with no deterioration over the previous 2 weeksprior to randomisation.

9, Provision, at pre-screening, of a formalin-fixed, paraffin-embedded (FFPE) tumour sample to assess tBRCA status and for HRD testing centrally. The centrally performed tBRCA test results must be available prior to randomisation and must indicate that the participant has a BRCAwt tumour, defined by the absence of a deleterious or suspected deleterious BRCA mutation by central testing.

10, Adequate organ and marrow function.

Key Exclusion Criteria:

• 1, Participants with stable disease or progressive disease on the post-treatmentscan or clinical evidence of progression at the end of the participant's first-linechemotherapy treatment, or any evidence of progressive disease prior torandomization.

2, Participant has mucinous or clear cell subtypes of epithelial ovarian cancer,carcinosarcoma, undifferentiated ovarian cancer, non-epithelial ovarian cancer,borderline tumours or low grade epithelial ovarian tumours (applies to fallopiantube and primary peritoneal tumours where applicable).

3, Participants with Stage III disease who have had complete cytoreduction (ie, nomacroscopic residual disease) at their primary debulking surgery.

4, Participants who have undergone ˃ 2 debulking (cytoreductive) surgeries.

5, History of another primary malignancy except for: malignancy treated withcurative intent with no known active disease ≥ 5 years before the first dose ofstudy intervention and of low potential risk for recurrence; Adequately treatednon-melanoma skin cancer, curatively treated in situ cancer of the cervix, ductalcarcinoma in situ (DCIS), and Stage 1, Grade 1 endometrial carcinoma. Participantswith a history of localised triple negative breast cancer, provided they completedtheir adjuvant chemotherapy more than three years prior to registration, and thatthe participant remains free of recurrent or metastatic disease.

6, Persistent toxicities (CTCAE Grade ≥2) caused by previous anticancer therapy,excluding alopecia and CTCAE Grade 2 peripheral neuropathy. Participants withirreversible toxicity that is not reasonably expected to be exacerbated by studyintervention may be included after consultation with the AstraZeneca studyphysician.

7, Participant is immunocompromised

8, Prior exposure to a PARP inhibitor, including olaparib

9, Any concurrent anticancer treatment

10, Currently pregnant or breast-feeding