Ovarian cancer is the most lethal gynecological cancer and the 5th leading cause of cancer death in women. Platinum chemotherapy has been widely adopted as a standard treatment for advanced ovarian cancer, the response rates in patients with relapsed/refractory ovarian cancer is unacceptably low. PD-1 blockade has been developed to a new class of cancer immunotherapy that could restore an adequate immunosurveillance against the neoplasm and enhance T-cell-mediated anticancer immune responses. Manganese has been confirmed to activate antigen-presenting cells and function as mucosal immunoadjuvants in pre-clinical studies. This two-arm, phase I/II study is designed to assess the safety and efficacy of combined therapy of anti-PD-1 antibody and chemotherapy with or without Manganese priming.

Inclusion Criteria:

1. Subjects must have histologically proven relapsed or refractory ovarian cancer (Refractory was defined as a lack of response to or progression during the frontline treatment; relapsed was defined as progression after the frontline treatment), including patients diagnosed with primary carcinoma of fallopian tube or peritoneum carcinoma.
2. Female.
3. ≥ 18 years old.
4. Life expectancy of at least 6 months.
5. Eastern Cooperative Oncology Group performance status 0-2.
6. Radiographic imaging (CT/MRI/PET-CT) indicated recurrence or metastasis; or cancer cells in ascites are positive; or CA125 concentration in the peripheral blood is more than 2 times the upper limit of normal value.
7. Subjects must have received at least two frontline therapies, at least one of which is platinum-containing.
8. Subjects with Anti-PD-1 antibody treatment history are eligible which must be resistance.
9. Adequate organ function.
10. Female participants of childbearing potential must be willing to use an adequate method of contraception for the course of the study through 120 days after the last dose of study drug.

Exclusion Criteria:

1. Subjects with any autoimmune disease or history of syndrome that requires corticosteroids or immunosuppressive medications.
2. Serious uncontrolled medical disorders or active infections, pulmonary infection especially.
3. Prior organ allograft.
4. Women who are pregnant or breastfeeding.
5. Women with a positive pregnancy test on enrollment or prior to investigational product administration.
6. Subjects who are compulsorily detained for treatment of either a psychiatric or physical (eg, infectious disease) illness.
7. Subjects with previous or concurrent other malignancies.