This study aimed to evaluate the efficacy and safety of the combination of cadonilimab with liposomal irinotecan plus fluorouracil and leucovorin for the treatment of advanced biliary tract cancer.

Inclusion Criteria:

1. Diagnosed with pathologically confirmed locally advanced unresectable or metastatic adenocarcinoma of the bile ducts, gallbladder, or cholangiocellular carcinoma, with primary tumors located in the intrahepatic bile ducts, hilar bile ducts, distal bile ducts, or gallbladder;
2. Progression after prior gemcitabine-based systemic chemotherapy and refused or were intolerable to initial treatment with gemcitabine-based chemotherapy regimens;
3. At least one measurable objective lesion of the tumor according to the RECIST version 1.1 criteria, which must have a maximum diameter of ≥1 cm for spiral CT or ≥2 cm for plain CT or MRI; and should be performed within 28 days prior to enrollment;
4. Aged 18 to 75 years old;
5. Eastern Cooperative Oncology Group performance status (ECOG PS) ≤ 1;
6. Life expectancy of greater than 3 months;
7. Must be able to participate the study voluntarily and sign the informed consent document;
8. Adequate organ and bone marrow function as below:

Absolute neutrophil count ≥1.5*109/L , platelet count ≥75*109/L , hemoglobin ≥90g/L; Alanine aminotransferase, and aspartate aminotransferase ≤2.5 × upper limit of normal; Total bilirubin and serum creatinine ≤1.5 × upper limit of normal.

Exclusion Criteria:

1. Disease-free survival within 5 years due to other malignancies (except for adequately treated basal cell carcinoma of the skin and carcinoma in situ of the cervix);
2. Serious or uncontrolled infectious disease (HIV, HBV DNA > 500IU/ml);
3. Severe uncontrolled acute infection (infection causing a fever of 38℃ or higher)；
4. Severe hepatic or renal insufficiency; or recent history of myocardial infarction (within 3 months)；
5. Current or past autoimmune disease and susceptibility to its reoccurrence;
6. Serious or uncontrolled pleural effusion or ascites;
7. Subjects with a history of active tuberculosis infection within 1 year prior to the first administration of study drug. If in the judgment of the investigator, subjects with more than 1 year prior to the first administration of study drug were considered suitable for enrollment; Subjects with a long history of chronic diarrhea or the presence of complete intestinal obstruction;
8. Subjects requiring systemic therapy with corticosteroids (> 10 mg/day prednisone equivalent dose) or other immunosuppressive drugs within 14 days prior to administration of study drug.
9. Combined with other serious medical and surgical conditions that affected organ function;
10. Participated in other clinical trial within 4 weeks;
11. Pregnant or breastfeeding women or subjects of childbearing potential (males or females with less than 1 year of menopause) who were unwilling to use contraception;
12. Subjects with a history of allergic or hypersensitivity reactions to components of the study drug;