CD274 and gallbladder adenocarcinoma: KEYNOTE-028 (ClinicalTrials.gov, NCT02054806) is another ongoing, multi-cohort, phase 1b trial of pembrolizumab monotherapy for patients with PD-L1-positive advanced solid tumors, including PD-L1-positive adenocarcinoma of the gallbladder or biliary tree, excluding cancer of the ampulla of Vater.