BMS-1166-N-piperidine-COOH is a chemical compound that functions as the BMS-1166-based moiety. It binds to the E3 ligase ligand through a linker, leading to the formation of PROTAC PD-1/PD-L1 degrader-1, which facilitates the degradation of PD-1/PD-L1. BMS-1166 demonstrates potent inhibition of PD-1/PD-L1 interaction, with an IC 50 of 1.4 nM. By antagonizing the inhibitory effect of the PD-1/PD-L1 immune checkpoint on T cell activation, BMS-1166 promotes T cell activation.