CD274 and biliary tract cancer: For ongoing clinical trials, we searched the ClinicalTrials.gov database for recruiting and active, not recruiting trials, using the following keywords: “biliary tract cancer” OR “intrahepatic cholangiocarcinoma” OR “extrahepatic cholangiocarcinoma” OR “perihilar cholangiocarcinoma” OR “distal cholangiocarcinoma” OR “gallbladder carcinoma” OR “ampulla of Vater” AND “antiangiogenic therapy” AND “immunotherapy” OR “immune checkpoint inhibitors” OR “PD-L1 inhibitors” OR “immunotherapy and antiangiogenic combined therapy” OR “angiogenesis inhibitors and immunotherapy”.