...1) Patients who can voluntarily sign an informed consent form; 2) Females aged ≥18 years at the time of signing the informed consent form; 3) ECOG PS performance status score between 0 and 2; 4) Patients histologically diagnosed with HER2-positive metastatic breast cancer, with or without brain metastasis, and with locally recurrent disease that cannot undergo curative surgery or radiation therapy; 5) Patients who experience relapse or metastasis within 1 year during or after (neo)adjuvant pertuzumab-based targeted therapy, or disease progression during first-line pertuzumab-based targeted therapy in advanced stages; 6) Patients who have received ≤1 regimen of previous pertuzumab-based targeted therapy for recurrent or metastatic disease; 7) Brain metastasis patients must meet the following criteria: stable previous brain metastasis treatment, untreated brain metastasis with no immediate need for local treatment, or progressive previous brain metastasis without immediate need for local treatment; 8) Left ventricular ejection fraction (LVEF) ≥50%; 9) Blood routine examination meets the following conditions: ① absolute neutrophil count (ANC) ≥1.5×109/L, ② platelet count ≥100×109/L, ③ hemoglobin ≥90g/L, ④ white blood cell count ≥3.0×109/L; 10) Liver function meets the following conditions: ① serum total bilirubin ≤1.5×ULN, or ≤3×ULN if liver metastasis is present, ② aspartate aminotransferase (AST) or alanine aminotransferase (ALT) ≤3×ULN, or ≤5×ULN if liver metastasis is present; 11) Renal function meets the following conditions: serum creatinine ≤1.5×ULN or creatinine clearance ≥50 mL/min (creatinine clearance calculated according to the Cockcroft-Gault formula); 12) Female patients who meet the following conditions can participate in this study: ① not fertile; ② fertility potential, with a negative pregnancy test result within 7 days before the first administration of the study drug, not breastfeeding, and consistently using highly effective contraceptive measures before study enrollment, throughout the study period, and within 6 months after the last administration of the study drug....