A Study Comparing BL-B01D1 With Chemotherapy of Physician's Choice in Patients With Unresectable Locally Advanced, Recurrent, or Metastatic HR+HER2- Breast Cancer(PANKU-Breast01)

This trial is a registered phase III, randomized, open-label, multicenter study to evaluate the efficacy and safety of BL-B01D1 in patients with unresectable locally advanced, recurrent, or metastatic HR+HER2- breast cancer after failure of at least one prior line of chemotherapy.

Inclusion Criteria: 1. Voluntarily sign the informed consent and follow the requirements of the protocol; 2. No gender limit; 3. Age ≥18 years old; 4. expected survival time ≥3 months; 5. Patients with unresectable locally advanced, recurrent metastatic HR+HER2- breast cancer; 6. The subjects had received 1-2 lines of chemotherapy regimens in the unresectable locally advanced recurrence or metastasis stage, and had been treated with endocrine, CDK4/6 inhibitors, and taxanes; 7. Documented radiographic disease progression; 8. Consent to provide archival tumor tissue samples or fresh tissue samples of primary or metastatic lesions within 3 years; 9. Must have at least one measurable lesion according to RECIST v1.1 definition; 10. ECOG score 0 or 1; 11. Toxicity of previous antineoplastic therapy has returned to ≤ grade 1 defined by NCI-CTCAE v5.0; 12. No severe cardiac dysfunction, left ventricular ejection fraction ≥50%; 13. No blood transfusion, no use of cell growth factors and/or platelet raising drugs within 14 days before screening, and the organ function level must meet the requirements; 14. Urine protein ≤2+ or \< 1000mg/24h; 15. For premenopausal women with childbearing potential, a pregnancy test must be performed within 7 days before the initiation of treatment, serum pregnancy must be negative, and it must be non-lactating; All enrolled patients (male or female) were advised to use adequate barrier contraception throughout the treatment cycle and for 6 months after the end of treatment. Exclusion Criteria: 1. Prior receipt of an ADC drug with a topoisomerase I inhibitor as a toxin; 2. Prior receipt of an ADC or antibody drug targeting EGFR and/or HER3; 3. Chemotherapy, biological therapy, immunotherapy, etc., have been used within 4 weeks or 5 half-lives before the first dose, small molecule targeted therapy has been used within 5 days, palliative radiotherapy, modern Chinese medicine preparations approved by NMPA for anti-tumor therapy, etc., have been used within 2 weeks; 4. anthracycline equivalent cumulative dose of adriamycin \> 360 mg/m2; 5. History of severe cardiovascular or cerebrovascular disease; 6. Unstable deep vein thrombosis, arterial thrombosis, and pulmonary embolism requiring medical intervention within 6 months before screening; Infusion-related thrombosis was excluded; 7. QT prolongation, complete left bundle branch block, III degree atrioventricular block, frequent and uncontrollable arrhythmia; 8. Other malignant tumors diagnosed within 3 years before the first dose; 9. Hypertension poorly controlled by two antihypertensive drugs; Patients with poor glycemic control; 10. A history of interstitial lung disease (ILD) requiring steroid therapy, current ILD or grade ≥2 radiation pneumonitis, or suspicion of such disease on imaging during screening; 11. Complicated pulmonary diseases leading to clinically severe respiratory function impairment; 12. Patients with active central nervous system metastases; 13. Patients with massive or symptomatic effusions or poorly controlled effusions; 14. Imaging examination showed that the tumor had invaded or wrapped around the large blood vessels in the abdomen, chest, neck, and pharynx; 15. Severe infection within 4 weeks before randomization; Evidence of pulmonary infection or active pulmonary inflammation within 2 weeks before randomization; 16. Was receiving \&gt before randomization; Long-term systemic corticosteroid therapy with 10mg/ day prednisone or equivalent anti-inflammatory active drugs or any form of immunosuppressive therapy; 17. Severe unhealed wound, ulcer, or fracture within 4 weeks before signing the informed consent; 18. Subjects with clinically significant bleeding or obvious bleeding tendency within 4 weeks before signing the informed consent; 19. Patients with inflammatory bowel disease, extensive bowel resection history, immune enteritis history, intestinal obstruction or chronic diarrhea; 20. Have a history of allergy to recombinant humanized antibodies or to BL-B01D1 and any excipients; A history of autologous or allogeneic stem cell transplantation; 21. Human immunodeficiency virus antibody positive, active hepatitis B virus infection or hepatitis C virus infection; 22. A history of severe neurological or psychiatric illness; 23. Received other unmarketed investigational drug or treatment within 4 weeks before the first dose; A live vaccine dose within 28 days before the planned dose or the first dose; 24. Any complications or other circumstances deemed by the investigator to preclude participation in the trial.