A novel hydrophobic tag leads to the efficient degradation of programmed death-ligand 1

The interaction of PD-L1 and PD-1 transmits the inhibitory signal to reduce the proliferation of antigen-specific T-cells in lymph nodes. The expression of PD-L1 confers a potential escaping mechanism of tumors from the host immune system. Blocking the interaction of PD-1 and PD-L1 enables tumor-reactive T cells to overcome regulatory mechanisms and induce an effective antitumor response. The hydrophobic tag tethering degrader (HyTTD) contains a hydrophobic moiety, binding to the protein of interest (POI) to mimic the misfolding state of the POI, thereby inducing the degradation of POI. In this work, using the HyTTD strategy, we selected the diphenylmethyl derivatives as the PD-L1 binding motif for PD-L1 to develop the degraders for PD-L1, and multiple hydrophobic tags were attached. As a result, two HyTTDs Z2d and Z3d efficiently decreased the protein level of PD-L1 in both NCI-H460 and HT-1080 cells with low cytotoxicity. Meanwhile, the reduction of PD-L1 protein levels by Z2d/Z3d was counteracted by MG132, which indicated that Z2d/Z3d degraded PD-L1 through the proteasome pathway. Moreover, the molecular modeling results indicated that the HyT group of Z2d or Z3d extended the surface of the protein to mimic the misfold. Importantly, our work also identified a novel HyT, which could be applied to develop the HyTTD for other target proteins.