The purpose of this study is to evaluate the efficacy, safety, and pharmacokinetics of RC88 monotherapy in subjects with Platinum-Resistant Recurrent Epithelial Ovarian, Fallopian Tube and Primary Peritoneal Cancer.

Inclusion Criteria:

1. Agree to participate in the study and sign an Informed Consent Form;
2. Female subjects aged 18 years or older at the time of signing the Informed Consent Form;
3. Histology confirmed high grade serous ovarian, fallopian tube or primary peritoneal cancer;
4. Must be newly developed platinum-resistant (Must not have received systemic therapy after developing platinum resistance status);
5. Received at least 3 prior lines of systemic therapies；
6. Imaging evidence of disease progression during or at the end of last-line therapy;
7. Eastern Cooperative Oncology Group (ECOG) Performance Status of 0 or 1;
8. Life expectancy of at least 12 weeks;
9. Subjects are willing to provide archival tumor tissue samples or accept a low-risk routine medical procedure to collect the fresh biopsy sample for immunohistochemical (IHC) MSLN testing;
10. Measurable lesion according to RECIST v1.1；
11. The interval between previous focal radiotherapy and the first dose should be at least 2 weeks；
12. Have laboratory tests that meet the relevant requirements to demonstrate adequate organ function;
13. Subjects of childbearing potential are required to use effective contraception from the time of informed consent and continuing through 6 months after the final dose of study intervention; Fertile subjects included those who were not menopausal or had been menopausal for less than 2 years and had not undergone bilateral adnexectomy or hysterectomy；Subjects of childbearing potential must have a negative pregnancy test within 7 days prior to the first dose of study intervention.

Exclusion Criteria:

1. The presence of clinically uncontrollable third-space fluids, such as massive pleural effusion or pericardial effusion accompanied by clinical symptoms or requiring symptomatic management; and ascites that cannot be effectively controlled with treatment;

2. Subjects with asymptomatic brain metastases who have received prior treatment may participate in this study if they meet all the following criteria:

   • Only supratentorial and/or cerebellar metastases are present.
   • Corticosteroids should be discontinued for at least 7 days prior to the first dose;
   • No disease progression is observed on imaging from completion of brain-directed therapy until randomization compared to pre-treatment imaging (at least 4 weeks interval).
   • Subjects must undergo radiotherapy and/or surgery for brain metastases if new asymptomatic brain metastases are detected during screening period.

3. Subjects with a history of other invasive malignancies within 3 years prior to the first dose, except for adequately treated papillary thyroid carcinoma, basal cell or squamous cell skin cancers without evidence of recurrence, and other adequately treated carcinoma in situ without evidence of disease recurrence；

4. Subjects with ongoing clinically significant toxicity associated with prior treatment that has not resolved to Grade 0 or 1 by NCI CTCAE 5.0;

5. Subjects who have received systemic anti-tumor therapy (including chemotherapy, targeted therapy, biologic therapy, hormonal therapy, etc.) within 28 days or 5 half-lives of prior therapy (whichever is shorter) prior to first dose;

6. Subjects who have received herbal or proprietary Chinese medicines for tumor control within 14 days prior to the first dose;

7. Subjects who have received previous mesothelin target-related drugs or MMAE, MMAF, DM1, DM4 and other microtubule inhibitor ADCs；

8. Subjects with clinical symptoms or signs of gastrointestinal obstruction;

9. History of cirrhotic liver disease (Child-Pugh Class B or C);

10. Subjects with immunodeficiency diseases, currently receiving systemic glucocorticoid therapy (dose>10 mg/d of prednisone or equivalent dose among drugs in the same class), or receiving immune suppressant therapy within 7 days prior to the first dose；

11. Major surgery within 4 weeks and no fully recovered prior to the first dose or anticipation of surgery；

12. Patients with active or progressive infection that requiring systemic therapy within 14 days prior to first dose, such as active tuberculosis;

13. serum virological testing (based on study center normal values)

    • Positive results of Hepatitis B virus surface antigen (HBsAg) should be further tested for HBV DNA, HBV DNA > 200IU/ml or 2000 copies /ml cannot be enrolled. However, if subjects received nucleotide-based antiviral therapy and test result below the criteria above, they could be enrolled;
    • Positive results of Hepatitis C antibody (HCVAb) (HCV RNA>103 copies/ml) cannot be enrolled. However, if subjects received nucleotide-based antiviral therapy and the test result below the criteria above, they could be enrolled;
    • Positive results for human immunodeficiency virus antibody (HIVAb).

14. Subjects with prior allogeneic haematopoietic stem cell transplantation or solid organ transplantation, or those who are waiting for organ transplantation;

15. Uncontrolled or significant cardiovascular and cerebrovascular diseases;

16. A history of interstitial lung disease requiring treatment or currently having a severe pulmonary disease, including but not limited to interstitial lung disease;

17. In the investigator's opinion, any other diseases, metabolic dysfunction, physical examination finding, or clinical laboratory findings, that raise reasonable suspicion of a disease or condition affecting the interpretation of the study results or placing the patient at high risk of participating in the study；

18. Subjects with active corneal disease and those who, in the judgement of the ophthalmologist, are unsuitable for inclusion by funduscopic examination and other ocular related examinations；

19. Subjects with known allergies to RC88 or its excipients or have had a history of severe allergic reactions to the other monoclonal antibodies or chemotherapies;

20. Subjects who have received a live or live-attenuated vaccine within 4 weeks prior to the first dose or plan to receive the above vaccines during the study；

21. Known psychiatric or substance abuse disorders that may have an impact on compliance with the study requirements.

22. Pregnant and/or breast-feeding women；

23. The subject's compliance are estimated to be insufficient to participate in this study, or other factors that, in the investigator's opinion, make the subjects unsuitable for participation of this study.