• Subjects voluntarily enrolled in this study with good compliance

• Age: 18-75 years old; Eastern Cooperative Oncology Group Performance Status (ECOG PS) score: 0-1

• HER2 positive, recurrent or metastatic invasive breast cancer confirmed by histopathology or cell pathology

• Defined hormone receptor (HR) status

• Has not received systemic anti-tumor therapy during the recurrence/metastasis stage (acceptable ≤ first-line endocrine therapy)

• If receiving (new) adjuvant therapy, it is required that the time interval between the end of systemic therapy (excluding endocrine therapy) and the discovery of recurrence/metastasis be greater than 12 months

• Have at least one measurable lesion according to RECIST 1.1 criteria;

• Good major organ function