BMS-1166-N-piperidine-COOH, the BMS-1166-based moiety, binds to E3 ligase ligand via a linker to form PROTAC PD-1/PD-L1 degrader-1 (HY-131183) to degrade PD-1/PD-L1. BMS-1166 is a potent PD-1/PD-L1 interaction inhibitor with an IC50 of 1.4 nM. BMS-1166 antagonizes the inhibitory effect of PD-1/PD-L1 immune checkpoint on T cell activation.