A Study to Evaluate the Efficacy and Safety of Novel Treatment Combinations in Participants With Ovarian Cancer

Inclusion Criteria: - Participant must be female greater than or equal to (>=)18 years of age, able to understand the study procedures, and agree to participate in the study by providing written informed consent.

• Participants must have the following histologic diagnosis unless otherwise specified in a cohort-specific supplement:
• Phase 2 cohorts: Participant has histologically diagnosed high-grade recurrent epithelial (that is [i.e.], serous, endometrioid, mucinous, clear cell) ovarian, fallopian tube, or primary peritoneal cancer or carcinosarcoma of the ovary. Participant with high-grade mixed histology is also eligible.
• For the Phase 1B components: Participant has histologically diagnosed gynecologic malignancy (i.e., any cancer that started in a woman's reproductive system). Gynecologic malignancies include cervical cancer; endometrial cancer; vaginal cancer; vulvar cancer; high-grade recurrent epithelial (i.e., serous, endometrioid, mucinous, clear cell) ovarian, fallopian tube, or primary peritoneal cancer; or advanced carcinosarcoma of the ovary. Participant with high-grade mixed histology is also eligible.
• The allowed number of prior lines of anticancer therapy for primary cancer will be specified in each cohort-specific supplement. Treatment with hormonal agents alone are not counted in the number of lines of therapy. Treatment with single-agent bevacizumab or PARP inhibitors given as maintenance is not counted as a separate line of therapy. If a therapeutic regimen is modified or changed for a reason other than lack of response or PD (such as allergic reaction, toxicity, or drug availability), this is not counted as a separate line of therapy.
• Phase 2 cohorts: Participant must have measurable disease according to Response Evaluation Criteria in Solid Tumors (RECIST) version (v) 1.1.
• Participant has an Eastern Cooperative Oncology Group (ECOG) performance status of 0 to 2.
• Participant has adequate organ function, defined as follows:
• Absolute neutrophil count >=1500 per microliter (/mcL), without growth factor support (granulocyte colony-stimulating factor or granulocyte-macrophage colony-stimulating factor administration is not permitted within 2 weeks prior to screening).
• Platelets >=100, 000/mcL without platelet transfusion support within 2 weeks prior to screening.
• Hemoglobin >=9 grams/deciliter (g/dL) without transfusion or growth factor (recombinant erythropoietin) within 2 weeks of screening.
• Serum creatinine less than or equal to ( =50 milliliter per minute (mL/min) using Cockcroft-Gault equation.
• Total bilirubin =50% of the prescribed dose of therapy within 5 weeks.
• Participant must not have known contraindication or uncontrolled hypersensitivity to carboplatin and paclitaxel and their excipients and no known pre-existing conditions that would preclude treatment with these agents.
• Participant must not have known contraindication or uncontrolled hypersensitivity to niraparib and its excipients.
• Participant must not have symptomatic ascites or pleural effusions as defined by the following criterion: presence of fluid in the abdominal or pleural cavities requiring removal within 1 week prior to signing the informed consent.
• Participant must agree to complete patient-reported outcomes (PRO) and work productivity questionnaires throughout the study.

Exclusion Criteria

• Participant has not recovered (i.e., to Grade =1.0 at screening or urine dipstick for proteinuria >=2 (Participants discovered to have >=2 proteinuria on dipstick at Baseline should undergo 24-hour urine collection and must demonstrate =350/microliters and viral load )4 weeks prior to study enrollment
• Participant received prior treatment for high-grade non-mucinous epithelial ovarian, fallopian tube, or peritoneal cancer (e.g., prior surgery, immunotherapy, anticancer therapy [with the exception of 1 run-in cycle of carboplatin-paclitaxel], or radiation therapy).
• Participant has an active autoimmune dis