Rilvegostomig + Chemotherapy as Adjuvant Therapy for Biliary Tract Cancer After Resection (ARTEMIDE-Biliary01)

A global study to assess the efficacy and tolerability of rilvegostomig compared to placebo in combination with investigator's choice of chemotherapy in participants with BTC after surgical resection with curative intent.

Inclusion Criteria: * Histologically confirmed adenocarcinoma of the biliary tract (intrahepatic or extrahepatic cholangiocarcinoma (CCA) or muscle invasive gallbladder cancer (GBC)) after macroscopically complete resection (R0 or R1) * Provision of a tumor sample collected at surgical resection. * Randomization within 12 weeks after resection with adequate healing and removal of drains. * Confirmed to be disease-free by imaging within 28 days prior to randomization. * Eastern Cooperative Oncology Group performance status of 0 or 1 Exclusion Criteria: * Participants with locally-advanced, unresectable, or metastatic disease at initial diagnosis. * Ampullary cancer, neuroendocrine, mixed neuroendocrine and non-neuroendocrine neoplasms and nonepithelial tumors. * Any anti-cancer therapy for BTC prior to surgery * Active or prior documented autoimmune or inflammatory disorders or any severe or uncontrolled systemic disease * Current or prior use of immunosuppressive medication within 14 days before the first dose * Thromboembolic event within 3 months * Active HBV or HCV infection unless treated.