This is an open-label, randomized, controlled, two-part study to evaluate the safety and efficacy of SHR-A1921 with or without carboplatin verus investigator's choice of platinum-based doublet chemotherapy in subjects with recurrent epithelial ovarian cancer.

Inclusion Criteria:

1. Voluntary participation and written informed consent.
2. Be able to provide fresh or archived tumour tissue.
3. Pathologically diagnosed epithelial ovarian cancer, primary peritoneal cancer, or fallopian tube cancer.
4. At least one measurable lesion according to RECIST v1.1.
5. Eastern Cooperative Oncology Group (ECOG) score: 0-1.
6. With a life expectancy ≥ 12 weeks.
7. Adequate bone marrow reserve and organ function.

Exclusion Criteria:

1. Uncontrolled pleural effusion, pericardial effusion, or abdominal effusion with clinical symptoms.
2. Previous or co-existing malignancies.
3. Has a history of non-infectious ILD/pneumonitis that required steroids, or has current ILD/pneumonitis;
4. Subjects with active hepatitis B or active hepatitis C;
5. Subjects who have received systemic anti-tumor treatments 4 weeks prior to the initiation of the study treatment.
6. Subjects who have been treated with TOP1 inhibitors, TROP-2 ADC or ADCs with TOP1 inhibitors as payload.
7. Has unresolved CTCAE ≥grade 2 toxicities from previous anticancer therapy.