In a phase II study in 61 patients with pre-treated BTCs with a PD-L1 combined positive score (CPS, number of PD-L1 staining cells [tumor cells, lymphocytes, macrophages] divided by the total number of viable tumor cells, multiplied by 100) ≥1, pembrolizumab monotherapy yielded ORR of 6.6%, median PFS of 2.0 months, and a favorable toxicity profile. Here, CD274 is linked to neoplasm.