Inclusion Criteria:  Male or female, age ≥18 years and ≤75 years. Patients with at least one measurable lesion per RECIST (v1.1) (applicable to the dose-extension stage). Eastern Cooperative Oncology Group (ECOG) performance status score 0 or 1 at screening and no deterioration occurs within two weeks before enrollment. Life expectancy period ≥ 12 weeks. Patients who have sufficient baseline organ function and whose laboratory data meet the following criteria (receiving no treatment of blood transfusions, albumin, recombinant human thrombopoietin, or colony-stimulating factor within 14 days before the first dose of this study). Patients with advanced gastric mucinous adenocarcinoma, advanced ovarian mucinous carcinoma or other dominant tumors participating in the dose-extension stage must provide eligible tumor tissue samples for biomarker detection; if subjects agree, tumor tissue samples should also be provided during the dose-exploration stage.  Exclusion Criteria:  Patients who have received any prior PD-1/PD-L1 antibody therapy (applicable to the dose-exploration stage). Patients with uncontrolled blood pressure (systolic blood pressure ≥ 150 mm Hg and/or diastolic blood pressure ≥ 100 mm Hg) or previous hypertensive crisis or hypertensive encephalopathy. Patients with active peptic ulcer, gastric outlet obstruction or persistent recurrent vomiting. Patients with a history of monoclonal antibody allergic reaction. Patients who are considered ineligible by the investigator due to any other severe, acute or chronic disease or other causes that the investigator considers could affect the patient's participation or assessment in the study.