This study is an open, multicenter Phase II clinical trial to evaluate the efficacy and safety of the SHR-A1811 combination in HER2 positive patients with locally advanced or metastatic biliary tract cancer.

Inclusion Criteria:

1. Age 18-75 years old (including both ends), male or female;
2. ECOG-PS score: 0 or 1;
3. Expected survival ≥ 12 weeks;
4. Locally advanced or metastatic biliary tract cancer confirmed by histopathology or cytology;
5. Subjects who had not previously received any systemic antitumor therapy were allowed to have previously received radical therapy, and had received the last dose of radical therapy for at least 6 months until disease recurrence;
6. According to the RECIST v1.1 standard, the subjects had at least one measurable lesion;
7. The main organ function is normal, in line with the program requirements;
8. Consent to contraception.

Exclusion Criteria:

1. Other active malignancies within 5 years or at the same time;
2. Local antitumor therapy was received within 4 weeks prior to initiation of treatment;
3. Subjects with biliary obstruction should be excluded;
4. There is active autoimmune disease or a history of autoimmune disease that may recur;
5. Known or suspected history of interstitial pneumonia or interstitial lung disease, or prior history of interstitial pneumonia or interstitial lung disease requiring hormone therapy;
6. Severe infection within 4 weeks prior to initiation of study treatment;
7. Active hepatitis B virus (HBV) infection;
8. Have serious cardiovascular and cerebrovascular diseases.