A Study Comparing BL-M07D1 With T-DM1 in Patients With Unresectable Locally Advanced or Metastatic HER2-positive Breast Cancer

Inclusion Criteria:

1. Voluntarily sign the informed consent and follow the requirements of the protocol;

2. No gender limit;

3. Age ≥18 years old and ≤75 years old at the time of signing the informed consent;

4. expected survival time ≥3 months;

5. Patients with histologically or cytologically confirmed, unresectable, locallyadvanced or metastatic HER2-positive breast cancer;

6. Provide the latest tumor tissues to the central laboratory for HER2 and HRdetection;

7. Must have at least one measurable target lesion that meets the RECIST v1.1definition;

8. ECOG 0 or 1;

9. Toxicity of previous antineoplastic therapy has returned to ≤ grade 1 defined byNCI-CTCAE v5.0;

10. No severe cardiac dysfunction, left ventricular ejection fraction ≥50%;

11. Blood transfusion is not allowed within 14 days before the first use of the studydrug, and no cell growth factor is allowed;

12. Coagulation function: international normalized ratio (INR) ≤1.5 and activatedpartial thromboplastin time (APTT)≤1.5×ULN;

≤2+ or < 1000mg/24h;

14. For premenopausal women with childbearing potential, a pregnancy test must beperformed within 7 days before the initiation of treatment, serum pregnancy must benegative, and must be non-lactating; All enrolled patients (male or female) wereadvised to use adequate barrier contraception throughout the treatment cycle and for 7 months after the end of treatment.

Exclusion Criteria:

1. Received chemotherapy with mitomycin C and nitrosourea within 6 weeks before thefirst dose, received surgery, chemotherapy, immunotherapy, etc. Within 4 weeksbefore the first dose, received endocrine therapy, palliative radiotherapy, andanti-tumor therapy approved by NMPA within 2 weeks before the first dose;

2. Previous use of HER2-ADC in the metastatic background;

3. Prior treatment with an ADC drug containing a camptothecin derivative (topoisomeraseI inhibitor) as a toxin;

4. The history of severe cardiovascular and cerebrovascular diseases in the past sixmonths was screened;

5. Complicated with pulmonary diseases leading to severe impairment of lung function;

6. History of ILD/interstitial pneumonia, current ILD/interstitial pneumonia, orsuspected ILD/interstitial pneumonia; According to CTCAE v5.0 was defined as ≥ grade 3 pulmonary disease and ≥ grade 2 radiation pneumonitis;

7. QT prolongation, complete left bundle branch block, III degree atrioventricularblock, frequent and uncontrollable arrhythmia;

8. Other primary malignancies diagnosed within 5 years before the first dose;

9. Poorly controlled hypertension (systolic blood pressure &gt; 150 mmHg or diastolicblood pressure &gt; 100 mmHg);

10. Patients with active central nervous system metastases;

11. Patients with a history of allergy to recombinant humanized antibody or to any ofthe excipents of BL-M07D1;

12. Patients with known hypersensitivity or delayed hypersensitivity to certaincomponents of T-DM1 or similar drugs, or known contraindications to T-DM1;

13. History of autologous or allogeneic stem cell transplantation or organtransplantation;

14. Anthracycline-equivalent cumulative dose of adriamycin > 360 mg/m2;

15. Human immunodeficiency virus antibody positive, active hepatitis B virus infection,cirrhosis, or hepatitis C virus infection;

16. Serious infection within 4 weeks before the first dose of study drug; There wasactive pulmonary inflammation at the time of screening;

17. Patients with massive or symptomatic effusions or poorly controlled effusions;

18. Receiving active antiinflammatory drugs or any form of immunosuppressive therapybefore randomization;

19. A history of severe neurological or psychiatric illness;

20. Subjects with clinically significant bleeding or obvious bleeding tendency within 4weeks before signing the informed consent;

21. Intestinal obstruction, Crohn's disease, ulcerative colitis or chronic diarrhea;

22. Subjects who are scheduled to receive live vaccine or receive live vaccine within 28days before the first dose;

23. Patients who were deemed by the investigator to be ineligible for the study.