This study is an open-label, multicenter, dose-escalation and cohort expansion phase I clinical study to evaluate the safety, tolerability, pharmacokinetics characteristics or preliminary efficacy and antitumor activity in patients with locally advanced or metastatic breast cancer and other solid tumors.

Inclusion Criteria:

1. Able to understand the informed consent form, voluntarily participate in and sign the informed consent form;
2. Gender is not limited;
3. Age: ≥18 years old and ≤75 years old (stage Ia); ≥18 years old (stage Ib);
4. Locally advanced or metastatic breast cancer and other solid tumors;
5. Must have at least one measurable lesion that meets the RECIST v1.1 definition;
6. Have archived primary or recurrent tumor tissue specimens that can be submitted for central review;
7. ECOG ≤1;
8. The expected survival time as judged by the investigators was ≥3 months;
9. Bone marrow function, renal function and liver function should meet the requirements;
10. Coagulation function: fibrinogen ≥1.5g/L; Activated partial thromboplastin time (APTT) ≤1.5×ULN; Prothrombin time (PT) ≤1.5×ULN;
11. Fertile female subjects or male subjects with fertile partners must use highly effective contraception from 7 days before the first dose until 12 weeks after the last dose. Female subjects of childbearing potential must have a negative serum pregnancy test within 7 days before the first dose;
12. Subjects were able and willing to comply with protocol-specified visits, treatment plans, laboratory tests, and other study-related procedures.

Exclusion Criteria:

1. Chemotherapy, biological therapy, immunotherapy and other anti-tumor therapies have been used within 4 weeks or 5 half-lives before the first dose; Mitomycin and nitrosoureas were administered within 6 weeks before the first dose; Oral drugs such as fluorouracil;
2. Patients with active infection requiring intravenous antibiotics who did not complete treatment within 1 week before enrollment, except prophylactic antibiotics for puncture or biopsy;
3. Positive human immunodeficiency virus antibody, active tuberculosis, active hepatitis B virus infection or hepatitis C virus infection;
4. No reduction in toxicity from previous antineoplastic therapy to grade I as defined in CTCAE, version 5.0, or to the level specified in the inclusion criteria;
5. Patients at risk for active autoimmune disease or with a history of autoimmune disease may have central nervous system involvement;
6. Pulmonary disease defined as ≥ grade 3 according to NCI-CTCAE v5.0; A history of ILD requiring steroid therapy, or current ILD or grade ≥2 radiation pneumonitis;
7. Patients with previous allogeneic hematopoietic stem cell transplantation or organ transplantation;
8. Had a history of severe cardiovascular and cerebrovascular diseases;
9. Patients had or had thrombotic events such as deep vein thrombosis, arterial thrombosis and pulmonary embolism within 6 months before screening;
10. Brain parenchymal metastases and/or meningeal metastases or spinal cord compression, excluding stable and asymptomatic brain parenchymal metastases;
11. Uncontrolled pleural effusion with clinical symptoms who were judged by the investigator to be ineligible for enrollment;
12. Poorly controlled hypertension (systolic blood pressure > 150 mmHg or diastolic blood pressure > 100 mmHg);
13. Who had participated in a clinical trial of an unmarketed drug within 4 weeks before the study dose (counted as the end of the last dose);
14. Had received a live vaccine within 4 weeks before the trial dose;
15. Other circumstances that the investigator deemed inappropriate for participation in the trial.