2. HER2 low expression 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. Women of childbearing potential (WOCBP) subjects must agree to use highly effective contraception for 7 months from the start of study screening until the last study medication and agree not to breastfeeding.
7. Patients voluntarily joined the study and signed informed consent, had good compliance and willingness to cooperate with the visit and study related procedures.
You may not be if
1. Have other malignancies within the past 5 years.
2. Presence with uncontrollable third space effusion.
3. Have surgical treatment, radiotherapy, chemotherapy, immunotherapy, molecular targeted therapy, biological therapy or other drug clinical studies within 4 weeks before the first medication.
4. Accepted antibody drug conjugates containing etoisomercan derivative topoisomerase I inhibitor.
