A Phase III Study of SHR-A1811 Injection With or Without Pertuzumab in HER2-Positive Recurrent or Metastatic Breast Cancer

Inclusion Criteria: 1. Women aged 18 to 75 (inclusive) 2. HER2 positive (IHC3+ or ISH+) unresectable or metastatic breast cancer confirmed by histology or cytology. 3. ECOG score is 0 or 1 4. An expected survival of ≥ 12 weeks 5. At least one measurable lesion according to RECIST v1.1 criteria 6. Have adequate renal and hepatic function 7. Patients voluntarily joined the study and signed informed consent Exclusion Criteria: 1. Have other malignancies within the past 5 years 2. Active central nervous system metastasis without surgery or radiotherapy 3. In (neoadjuvant) adjuvant therapy phase, the interval from the end of systemic therapy (excluding endocrine therapy) to the detection of recurrence/metastasis ≤12 months 4. Presence with uncontrollable third space effusion 5. Have undergone other anti-tumor treatment within 4 weeks before the first dose 6. A history of immune deficiency 7. Clinically significant cardiovascular disorders 8. Known or suspected interstitial lung disease 9. The toxicity from previous anti-tumor treatment has not recovered to ≤ grade I 10. Known hereditary or acquired bleeding tendency 11. Active hepatitis and liver cirrhosis 12. Presence of other serious physical or mental diseases or laboratory abnormalities