This is a multicenter, Phase 2 clinical trial to evaluate the efficacy and safety, PK and immunogenicity of SHR-A1904 in patients with advanced or metastatic biliary tract cancer (BTC). Patients will treat with SHR-A1904 until unacceptable toxicity or disease progression.

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. CLDN18.2 positive expression;
6. Subjects who failed or intolerance after systemic chemotherapies;
7. According to the RECIST v1.1 standard, the subjects had at least one measurable lesion;
8. The main organ function is normal, in line with the program requirements;
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. Other active malignancies within 5 years or at the same time;
3. Subjects with a history or evidence of brain metastasis or meningeal metastasis;
4. With acute or chronic uncontrolled pancreatitis or Child-Pugh liver function grade C;
5. Severe trauma or major surgery was performed within 4 weeks before the first administration;
6. To study the severe heart disease within 6 months before the first administration;
7. Patients with clinical symptoms and uncontrolled moderate and above pleural effusion, ascites or pericardial effusion, requiring therapeutic puncture drainage;
8. Severe infection symptoms occurred within 2 weeks before the first administration;
9. Known hereditary or acquired bleeding and thrombotic tendency;
10. Congenital or acquired immune defects;
11. The subjects had severe and uncontrollable concomitant diseases;
12. Cerebral infarction, pulmonary embolism or deep vein thrombosis occurred within 6 months before the first administration of the study.