This is a randomized, open-label, parallel-group multi-center study of Phase 3 study to assess the efficacy and safety of KN035 compared to standard of care (SOC) Gemcitabine-based chemotherapies in the treatment of participants with previously untreated locally advanced or metastatic biliary tract cancer.

The primary hypothesis of this study is that participants will have a longer overall Survival (OS) when treated with combined therapy than SOC.

Inclusion Criteria:

• Eighteen years and older;
• Histological or cytological diagnosis of unresectable or metastatic gallbladder cancer or cholangiocarcinoma;
• Previously untreated with systemic therapy; Subjects who developed recurrent disease >6 months after a sort of adjuvant, neoadjuvant chemotherapy could also be eligible.
• Liver function Child-Pugh A or B;
• Performance status of 0 or 1 on the Eastern Cooperative Oncology Group (ECOG) Performance Status;
• Life expectancy of at least 12 weeks;
• At least one measurable lesion per RECIST 1.1;
• Adequate organ function

Exclusion Criteria:

• Specific anti-tumor treatment prior to 4 weeks;
• more than 50% liver metastasis ;
• Patient with other serious diseases or clinical conditions, including but not limited to uncontrolled active infection etc;
• History of severe hypersensitivity reaction to any monoclonal antibody or chemistry;
• Women who are pregnant or in the period of lactation;
• Patients with an active, known or suspected autoimmune disease. Patients are permitted to enrol if they have vitiligo, type I diabetes mellitus, residual hypothyroidism due to autoimmune condition only requiring hormone replacement;