Phase II Clinical Study of SHR-A1811 in Patients With HER2 Expression / Amplification of Locally Advanced Unresectable or Recurrent 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. 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;