Age 18-75 years；ECOG performance status 0-1； Histologically or cytologically confirmed HER2-negative metastatic breast cancer； At least one measurable lesion per RECIST v1.1； Eligible for ADC therapy； Adequate organ and bone marrow function； Life expectancy ≥3 months； Willingness to provide tumor tissue and blood samples； Signed informed consent
You may not be if
Prior treatment with ADC targeting the same antigen and payload；History of grade ≥3 immune-related adverse events； Active or untreated CNS metastases； Active autoimmune disease requiring systemic therapy； Clinically significant cardiovascular disease； Active interstitial lung disease； Active infection including tuberculosis, HIV, hepatitis B or C； Pregnancy or breastfeeding；Investigator-determined conditions that may interfere with study participation
