ARX788 in HER2-positive Metastatic Breast Cancer Patients Who Were Previously Treated With T-DXd

Inclusion Criteria: 1. 18 to 75 years old (including upper and lower limits), male or female; 2. Unresectable locally advanced, recurrent or metastatic BC; 3. Tissue samples determined to be HER2 positive (defined as IHC3+ or FISH+); 4. Received T-DXd treatment in the advanced stage; 5. Adequate bone marrow, liver, kidney and coagulation function; 6. Voluntarily sign the informed consent, have good compliance and are willing to comply with the follow-up visit. Exclusion Criteria: 1. With meningeal metastases or disseminated brain metastases or active brain metastases; 2. Has interstitial lung disease requiring steroid therapy, a history of drug-induced interstitial lung disease, a history of radiation pneumonitis, or any evidence indicating clinically active interstitial lung disease; 3. Has any eye disease that require medical intervention such as keratitis, corneal diseases or active eye infection; 4. Has cardiac insufficiency; 5. Has received any systemic anti-tumor therapy (with the exception of endocrine therapy, with an interval of at least 7 days) within 28 days (or at least 5 half-lives) before the first use of the investigational product;