PD-1-IN-2898 (2989 is the last four digits of the CAS #), a [1,2,4]triazolo[4,3- a]pyridine analog, is a novel and potent programmed cell death-1 (PD-1)/programmed cell death-ligand 1 (PD-L1) interaction inhibitor with an IC50 of 92.3 nM. Inhibition of the programmed cell death-1 (PD-1)/programmed cell death-ligand 1 (PD-L1) interaction using small-molecule inhibitors is an emerging immunotherapeutic approach.