HER2-positive Breast Cancer Project Initiated by Investigators

Inclusion Criteria: * 1\. Male or female patient ≥ 18 years and ≤ 75 years when signing the informed consent form; 2. Breast cancer patients by histopathology and/or cytology documented, including: a) Participants with unresectable locally advanced or metastatic breast cancer; b) Evaluated or tested as HER2-positive expression. The definition of HER2 positive in this study: immunohistochemistry (IHC) was 2+ and confirmed by fluorescence in situ hybridization (FISH), or IHC was 3+; 3. Have received at least 3 targeted therapies for locally advanced or metastatic disease, including: 1. Disease progression after receiving at least 1 trastuzumab-containing (including a biosimilar of trastuzumab on the market)-based treatment; 2. After receiving at least one anti-HER2 tyrosine kinase inhibitor (lapatinib or pyrrotinib)-based treatment plan, the disease progresses or cannot tolerate toxic and side effects; 3. The disease progresses or cannot tolerate toxic and side effects after receiving treatment with antibody-conjugated drugs targeting HER2 (such as T-DM1 or other ADCs); Note: Adjuvant therapy and anti-HER2 therapy used in the neoadjuvant treatment stage before radical treatment are not counted, but recurrence or metastasis occurs during the last anti-HER2 medication period or within one year after the end, it can be regarded as a plan. 4\. Have previously received taxanes to treat breast cancer; Exclusion Criteria: * 1\. Serious or uncontrollable heart diseases that require treatment, including: 1. Congestive heart failure graded 3 or 4 by the New York College of Cardiology (NYHA); 2. Unstable angina pectoris that cannot be controlled by drugs; 3. Myocardial infarction occurred within 6 months before the first administration of the study treatment; 4. Severe arrhythmia requiring medical treatment (except for atrial fibrillation or paroxysmal supraventricular tachycardia); 2. Baseline measurement, QTc interval, male\> 450 msec, female\> 470 msec; 3. Clinically active interstitial lung disease; 4. Patients with primary central nervous system (CNS) malignant tumors or CNS metastases that have failed local treatment; for asymptomatic brain metastases, or with stable clinical symptoms and no need for steroids and other brain metastases within 4 weeks before the first administration of the trial drug Treated patients can be included in the group; 5. Those who are known to have a history of hypersensitivity to other monoclonal antibodies or allergic to A166 and its components for injection; 6. Those who have permanently discontinued trastuzumab due to any toxicity;