A Study of BL-M07D1, BL-M07D1+Pertuzumab and BL-M07D1+Pertuzumab+Docetaxel in Patients With Unresectable Locally Advanced or Metastatic HER2-positive Breast Cancer

Inclusion Criteria: 1. Sign the informed consent form voluntarily and follow the protocol requirements; 2. Gender is not limited; 3. Age ≥18 years old and ≤75 years old; 4. Expected survival time for 3 months or more; 5. Patients with histologically and/or cytologically confirmed unresectable locally advanced or metastatic HER2-positive breast cancer; 6. Consent to provide archived tumor tissue samples or fresh tissue samples from the primary or metastatic lesions; 7. At least one measurable lesion meeting the RECIST v1.1 definition was required; 8. Physical condition score ECOG 0 or 1 ; 9. The toxicity of previous antineoplastic therapy has returned to ≤ grade 1 as defined by NCI-CTCAE v5.0; 10. No severe cardiac dysfunction, left ventricular ejection fraction ≥50%; 11. No blood transfusion, no colony-stimulating factor, and no albumin are allowed within 14 days before the first use of the study drug, and the organ function level must meet the requirements; 12. Blood coagulation function: international standardization ratio (INR) 1.5 or less, and the part activated clotting time (APTT) live enzymes acuities were 1.5 x ULN; 13. Urinary protein ≤2+ or ≤1000mg/24h; 14. Fertile female subjects, or male subjects with fertile partners, must use highly effective contraception from 7 days before the first dose until 7 months after the end of the dose. Female subjects of childbearing potential had to have a negative serum pregnancy test within 7 days before the first dose. Exclusion Criteria: 1. Received chemotherapy with mitomycin C and nitrosourea within 6 weeks before the first dose, received surgery within 4 weeks before the first dose, and received endocrine therapy within 2 weeks before the first dose; 2. Patients with locally advanced or metastatic disease who have received previous systemic therapy; 3. Had received prior ADC drug therapy with camptothecin derivative as toxin; 4. Screening within the first half of the serious heart, cerebrovascular disease; 5. Complicated with pulmonary diseases leading to severe impairment of lung function; 6. A history of ILD/interstitial pneumonia requiring steroid therapy, current ILD/interstitial pneumonia, or suspected ILD; 7. QT prolongation, complete left bundle branch block, III degree atrioventricular block, frequent and uncontrollable arrhythmia; 8. Other primary malignancies diagnosed within 5 years before the first dose; 9. Poorly controlled hypertension; 10. Patients with active central nervous system metastases; 11. Need treatment intervention of unstable thrombotic events, except infusion related thrombosis; 12. Patients with a history of allergy to recombinant humanized antibodies or to any excipients of the trial drug; 13. Had received more than the following cumulative doses of anthracyclines; 14. Systemic corticosteroids or immunosuppressive agents were required within 2 weeks before study dosing; 15. Patients with massive or symptomatic effusions or poorly controlled effusions; 16. Severe systemic infection within 4 weeks before screening; 17. Active autoimmune and inflammatory diseases; 18. Human immunodeficiency virus antibody positive, active hepatitis B virus infection or hepatitis C virus infection; 19. Previous history of allogeneic stem cell, bone marrow or organ transplantation; 20. A history of severe neurological or psychiatric illness; 21. Pregnancy or lactation women; 22. Patients who were deemed by the investigator to be ineligible for participation in the study.