This study was to evaluate the efficacy and safety of SHR-A1811 in patients with locally advanced unresectable or recurrent metastatic BTC with HER2 expression / amplification who failed first-line or second-line systemic treatment.

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. Subjects with locally advanced or recurrent metastatic biliary tract cancer diagnosed by histopathology or cytology are not suitable for surgical resection, transplantation or ablation;
5. Subjects who failed or intolerance after systemic chemotherapies;
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. If the patient has active hepatitis B virus ( HBV ) infection : HBV-DNA must be < 500 IU / mL；
9. Consent to contraception.

Exclusion Criteria:

1. Received anti-tumor treatment such as chemotherapy, radiotherapy, immunotherapy, biotherapy or other clinical research drugs within 4 weeks before the first administration;
2. Subjects with a history or evidence of brain metastasis or meningeal metastasis ;
3. With acute or chronic uncontrolled pancreatitis or Child-Pugh liver function grade C ;
4. Severe trauma or major surgery was performed within 4 weeks before the first administration;
5. To study the severe heart disease within 6 months before the first administration ;
6. Patients with clinical symptoms and uncontrolled moderate and above pleural effusion, ascites or pericardial effusion, requiring therapeutic puncture drainage ;
7. Severe infection symptoms occurred within 2 weeks before the first administration;
8. Known hereditary or acquired bleeding and thrombotic tendency ;
9. Congenital or acquired immune defects;
10. The subjects had severe and uncontrollable concomitant diseases;
11. Cerebral infarction, pulmonary embolism or deep vein thrombosis occurred within 6 months before the first administration of the study;