In vitro and in vivo degradation of programmed cell death ligand 1 (PD-L1) by a proteolysis targeting chimera (PROTAC)

Immunotherapy via immune checkpoints blockade has aroused the attention of researchers worldwide. Inhibition of the programmed cell death-1 (PD-1)/programmed cell death-ligand 1 (PD-L1) interaction has been one of the most promising immunotherapy strategies. Several neutralizing antibodies targeting this interaction have been developed, which have already achieved considerable clinical success. Additionally, numerous pharmaceutical companies have been committed to develop small molecules which could block the interaction between PD-1 and PD-L1. In this study, a novel PROTAC molecule 21a was developed, and effectively induced the degradation of PD-L1 protein in various malignant cells in a proteasome-dependent manner. Moreover, compound 21a could significantly reduce PD-L1 protein levels of MC-38 cancer cells in vivo, by which promoted the invasion of CD8+ T cells and inhibited the growth of MC-38 in vivo. This PROTAC molecule could be used as a novel and alternative strategy for cancer immunotherapy.