This Phase 3 study will be conducted in different countries around the world with up to about 528 participants.

The purpose of this study is to evaluate how well Rina-S works against ovarian cancer in combination with available standard of care therapy that is already approved and used for ovarian cancer.

Participants will receive either Rina-S monotherapy (by itself), Rina-S plus bevacizumab, bevacizumab (standard of care) by itself, or no treatment (only monitoring, also standard of care). No participants will be given placebo. Participants will participate in 1 of 2 arms.

The treatment duration will be different for every participant. If a participant's cancer stays the same or gets better, and there are not any serious problems, participants can keep getting study treatment for as long as the study is open.

Participants will be asked to attend 1 to 3 visits at the study clinic for each cycle (duration of cycle is 3 weeks). During visits, there will be various tests (such as blood draws) and procedures (such as recording of heart activity and imaging) to monitor whether the study treatment is safe and effective. The overall study duration (including screening, treatment, and follow-up) for each participant will be different for every participant.

This is a randomized, open-label, Phase 3 study of Rina-S + standard of care (SOC) versus SOC as maintenance treatment after second-line (2L) platinum-based doublet chemotherapy in participants with recurrent PSOC.

Key Inclusion Criteria:

• Must have histologically or cytologically confirmed high-grade serous or endometrioid epithelial ovarian cancer (EOC), primary peritoneal cancer, or fallopian tube cancer.
• Must have PSOC defined as progressive disease > 6 months (ie, 183 days) from the last dose of primary (first-line [1L]) platinum therapy.
• Participants with known breast cancer (BRCA)-mutated (somatic or germline) or homologous recombination deficiency (HRD)-positive ovarian cancer who achieved complete response (CR)/no clinical evidence of disease (NED) or partial response (PR) following 1L platinum-based chemotherapy regimen must have previously received PARPi maintenance therapy as part of their 1L treatment.
• Must have completed platinum-based chemotherapy in the 2L treatment for recurrent PSOC.
• Must be randomized no later than 8 weeks from the last dose of the 2L platinum-based therapy.
• Participants must have achieved a CR/NED, PR; or SD permitted only if bevacizumab was given in 2L in combination with platinum-based chemotherapy, as assessed by the investigator, following completion of 2L platinum-based chemotherapy.

Key Exclusion Criteria:

• Participants with clear cell, mucinous, or sarcomatous histology, mixed tumors containing any of the above histologies, or low-grade/borderline ovarian tumors
• More than 2 prior lines of systemic therapy.
• Progression while on or following 2L platinum-based regimen prior to randomization.
• Participants who receive an intervening systemic anticancer treatment (excluding bevacizumab) after the last dose of 2L platinum-based chemotherapy and prior to randomization.

Note: Other protocol-defined Inclusion and Exclusion criteria may apply.