• 1\) Agree to follow the clinical trial protocol, volunteer, and sign the informed consent form (ICF).

• 2\) Women aged ≥ 18 years and ≤ 75 years at the date of signing the ICF. 3) HER2-locally advanced breast cancer diagnosed by histopathology and/or cytology (Unable to receive radical therapy) or metastatic breast cancer, and previous chemotherapeutic line of cytotoxicity for locally advanced or metastatic breast cancer was ≤ 3.

• 4\) Prior platinum therapy is allowed, but the best response to platinum therapy is required to be CR, PR, or persistent ≥ 12 weeks SD. If given as neoadjuvant/adjuvant therapy, the time from the last dose of platinum to relapse is ≥ 6 months.

• 5\) Hormone receptor-positive patients need to have received at least first-line of endocrine therapy for locally advanced or metastatic breast cancer but failed, or unsuitable for endocrine therapy in the judgment of the investigator.

• 6\) In neoadjuvant, adjuvant and/or metastatic stages, the patients who have received antitumor therapy with Taxane ± Anthracycline.

• 7\) Failure of front-line therapy (disease progression or toxicity intolerance), and the investigator judged that it was suitable to receive the systemic monotherapy (including capecitabine tablets, vinorelbine tartrate injection, eribulin mesylate injection).

• 8\) Tested or reviewed by a third-party central laboratory to determine whether there is harmful or suspected harmful gBBRCAm in the blood.

• 9\) At least one measurable (non-lymph node longest diameter ≥ 10 mm, lymph nodes with a minimum diameter of ≥ 15 mm, according to RECIST version 1.1 criteria) of target lesions. Note: Previously irradiated lesions cannot be used as targets lesions unless there is significant progression of the lesion.

• 10\) The physical condition score is 0-1 according to the scale of The Eastern Cooperative Oncology Group (ECOG).

• 11\) Expected survival ≥ 12 weeks. 12) Meet the following criteria (The use of any blood components and cell growth factors is not permitted within 2 weeks prior to initial administration): Bone marrow function: absolute neutrophil count (ANC) ≥ 1.5 × 109/L (1500/mm3); platelets ≥ 100 × 109/L (1 × 105/mm3); Hemoglobin ≥ 90 g/L; Liver function: serum bilirubin ≤ 1.5 × upper limit of normal (ULN), but except for Gilbert's syndrome patients (persistent or recurrent hyperbilirubinemia, unbound bilirubin elevation is present in the absence of evidence of hemolysis or liver pathology); patients without liver metastasis, alanine aminotransferase (ALT) and aspartate aminotransferase (AST) ≤ 2.5×ULN; ALT and AST ≤ 5×ULN for patients with liver metastasis; Renal function: serum creatinine ≤ 1.5 × ULN, or creatinine clearance (Ccr) ≥ 50 mL/min (Calculated according to the Cockcroft-Gault formula); Cockcroft-Gault formula: female Ccr (mL/min) = 0.85 × weight (kg) × (140-age)/ \[72 × creatinine (mg/dL)\] Coagulation function: international normalized ratio (INR) ≤ 1.5 × ULN, activated partial thromboplastin time (APTT) ≤ 1.5 × ULN.

• 13\) Women of childbearing age are willing to take effective contraception from signing the ICF to 6 months after the last administration of the investigational drug. Women of childbearing age must have a negative blood pregnancy test result 7 days before the first dose.