The purpose of this Chinese extension study is to compare how well Rina-S works against platinum-resistant ovarian cancer compared to chemotherapy drugs that are already approved and used for platinum-resistant ovarian cancer.

Treatment in this study could be Rina-S or it could be 1 of 4 indicated chemotherapy agents that are considered standard medical care. There is an equal (50:50) chance of getting Rina-S or an approved chemotherapy agent as treatment in this study. No one will know what treatment they are assigned to until the first dose.

All participants will receive active drug; no one will be given placebo.

This study is an extension study of the protocol GCT1184-02 (NCT06619236).

Key Inclusion Criteria:

• Participants must have histologically or cytologically confirmed high grade serous or endometrioid epithelial ovarian cancer, primary peritoneal cancer, or fallopian tube cancer.

• Participants may be enrolled regardless of FRα expression level.

• Participants must have received 1 to 4 prior lines of therapy. Participants must have progressed radiographically on or after their most recent line of therapy.

• Participants must have received prior treatment with the following therapies:

  • Platinum chemotherapy
  • Prior bevacizumab (or biosimilar) treatment is required, if labeled and available as standard of care per institutional guidelines, unless the participant has a documented contraindication or unless the participant is not eligible for treatment with bevacizumab (or biosimilar) due to precautions/intolerance
  • Participants with known or suspected deleterious germline or somatic breast cancer gene (BRCA) mutations and who achieved a complete or partial response to platinum-based chemotherapy must have been treated with a poly ADP-ribose polymerase (PARP) inhibitor as maintenance treatment unless the participant is not eligible for treatment with PARP inhibitor

• Mirvetuximab soravtansine, if:

  • Mirvetuximab soravtansine is available in the enrollment region, and
  • The participant is eligible, and
  • The participant does not have a documented medical exception, including chronic corneal disorders, history of corneal transplantation, or active ocular conditions requiring ongoing treatment/monitoring, such as uncontrolled glaucoma, wet age-related macular degeneration requiring intravitreal injections, active diabetic retinopathy with macular edema, macular degeneration, presence of papilledema, and /or monocular vision.

• Participants must have platinum-resistant disease:

  • Participants who have only had 1 line of platinum-based therapy must have received at least 4 cycles of platinum therapy, and must have either had a response (CR or PR) or had non-measurable disease at the start of adjuvant platinum-based therapy, and then progressed between > 91 days and ≤ 183 days after the date of the last dose of platinum.
  • Participants who have received a protocol defined number of lines of platinum-based therapy must have progressed on or within 183 days after the date of the last dose of platinum.

Key Exclusion Criteria:

• Prior therapy with an antibody-drug conjugate containing a topoisomerase 1 inhibitor.
• Have primary platinum-refractory disease, defined as ovarian cancer that did not respond (CR or PR) to or progressed ≤ 91 days after the last dose of a first-line platinum-containing regimen.
• History of another malignancy within 3 years before the first dose of study drug, or any evidence of residual disease from a previously diagnosed malignancy. Exceptions are malignancies with a negligible risk of metastasis or death (e.g., 5-year OS ≥90%), including, but not limited to, adequately treated carcinoma in situ of the cervix, non-melanoma skin carcinoma, ductal carcinoma in situ, or Stage I uterine cancer.
• Known active central nervous system metastases or carcinomatous meningitis. Participants with previously treated brain metastases may participate provided they are clinically stable for at least 4 weeks prior to study entry after brain metastasis treatment, they have no new or enlarging brain metastases, and are off corticosteroids and anticonvulsants prescribed for symptoms associated with brain metastases for at least 7 days prior to the first dose of study drug. Participants with suspected brain metastases at screening should undergo a computed tomography (CT)/magnetic resonance imaging (MRI) of the brain prior to study entry.
• Hospitalization or clinical symptoms due to gastrointestinal obstruction within the past 91 days or radiographic evidence of gastrointestinal obstruction at the time of screening. Enrollment of participants who currently require parenteral nutrition must be discussed with the study medical monitor to determine eligibility.
• Participant has clinically significant ascites/pleural effusion. Enrollment of participants with an indwelling catheter flush/drain is not allowed. Note: Clinically significant is defined as (1) symptomatic, or (2) requires therapeutic paracentesis/thoracentesis within 8 weeks of the first dose, or (3) recurrent ascites/pleural effusion that necessitates multiple paracentesis/thoracocentesis procedures more often than approximately every 4 weeks.

NOTE: Other protocol-defined Inclusion/Exclusion criteria may apply.