RC48-ADC Combinatioed Envolizumab in Locally Advanced or Metastatic Biliary Tract Cancer With Positive HER-2

Inclusion Criteria: * 18 years; * ECOG 0-1; * patients diagnosed by pathological or cytological diagnosis of locally advanced or metastatic biliary tract cancer (include intrahepatic cholangiocarcinoma, extrahepatic cholangiocarcinoma, gallbladder and ampullary carcinoma); * life expectancy of at least 3 months; * HER2 IHC 2+ or 3+; * At least one measurable objective tumor lesion according to RECIST 1.1; * Not received systemic chemotherapy in the past. Patients who have completed adjuvant therapy or neoadjuvant therapy before the start of the chemotherapy regimen in this trial 6 months ago can be included in this trial. * satisfactory main organ function (laboratory test must meet the following criteria): hemoglobin (HGB) ≥90g/L, neutrophil count (ANC) ≥1.5×109/L, platelet count (PLT) ≥80×109/L, Serum creatinine (CR) ≤1.5 upper normal limitation (UNL), total bilirubin (TBil) ≤1.5 upper normal limitation (UNL), alanine aminotransferase (ALT) and aspartate aminotransferase (AST) ≤ 2.5 UNL (For patients with liver metastasis, the AST/ALT must be ≤5.0 UNL), left ventricular ejection fraction (LVEF) ≥ 50%; * Subjects of childbearing potential must use an appropriate method of contraception during the study period and within 120 days after the end of the study, have a negative serum pregnancy test within 7 days prior to study enrollment, and must be non-lactating subjects; Exclusion Criteria: * Previously received drug therapy against PD-1/PD-L1 inhibitor and other Antibody conjugate drug (Such as T-DM1 and DS8201); * Allergic to the active ingredients or excipients of the study drug; * biliary obstruction were excluded. Unless blockage is treated locally, such as endoscopic stenting, percutaneous hepatic drainage, etc., total bilirubin is reduced below the upper limit of 1.5 UNL; * A history of malignancies other than biliary tract malignancies (other than cured carcinoma in situ of the cervix or basal cell carcinoma of the skin and other malignancies cured for 5 years); * Received major surgical treatment, incisional biopsy, or significant traumatic injury within 28 days prior to the start of study treatment; or had a long-term unhealed wound or fracture; * Unsuitable for the study or other chemotherapy determined by investigator.