• Subjects voluntarily participate in this study and sign the informed consent form;

• Age: 18-75 years (at time of signing Informed Consent Form (ICF); Eastern Cooperative Oncology Group (ECOG) performance status ≤1; estimated life expectancy \>3 months;

• Cytologically or histologically confirmed Human Epidermal Growth Factor Receptor 2 (HER2)-positive recurrent or metastatic breast cancer;

• Received ≥2 prior lines of anti-HER2 targeted therapy in the advanced setting;

• At least one measurable lesion meeting Response Evaluation Criteria in Solid Tumors, Version 1.1 (RECIST 1.1) criteria (excluding brain lesions);

• Willing to receive one of the investigator-selected chemotherapy regimens;

• Adequate organ function;

• Female subjects of childbearing potential must agree to use effective contraception (e.g., Intrauterine Device (IUD), oral contraceptives, or condoms) during the study and for 6 months after study completion.