Ikeda M, et al. - The safety and effectiveness of the immune checkpoint inhibitor nivolumab, as monotherapy or combined with chemotherapy, were investigated in Japanese patients with biliary tract cancer (BTC). In the monotherapy cohort (N = 30), they administered nivolumab monotherapy (240 mg, 2-week intervals) to patients with unresectable/recurrent BTC that was refractory or intolerant to gemcitabine-based treatment regimens. In the combined therapy cohort (N = 30), nivolumab (240 mg, 2-week intervals) plus cisplatin-gemcitabine chemotherapy was administered to chemonaïve patients with unresectable/recurrent BTC. In this phase 1 study, patients were able to tolerate nivolumab, which also exhibited a manageable safety profile and signs of clinical activity. Clinical activity of nivolumab in advanced BTC might be predicted by programmed death-ligand 1 (PD-L1). In the monotherapy cohort, patients with PD-L1 ≥ 1% displayed longer median overall survival (OS) and median progression-free survival (PFS) vs those with PD-L1 < 1%. In the combined therapy cohort, patients with PD-L1 ≥ 1% had higher objective response rate, but lower median OS and median PFS vs those with PD-L1 < 1%. These findings suggest the predictive value of PD-L1 expression status for clinical activity of nivolumab in advanced BTC.