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 tocomply with the follow-up visit.

Exclusion Criteria:

1. With meningeal metastases or disseminated brain metastases or active brainmetastases;

2. Has interstitial lung disease requiring steroid therapy, a history of drug-inducedinterstitial lung disease, a history of radiation pneumonitis, or any evidenceindicating clinically active interstitial lung disease;

3. Has any eye disease that require medical intervention such as keratitis, cornealdiseases or active eye infection;

4. Has cardiac insufficiency;

5. Has received any systemic anti-tumor therapy (with the exception of endocrinetherapy, with an interval of at least 7 days) within 28 days (or at least 5half-lives) before the first use of the investigational product;