Synthesis Of Novel PD-1/PD-L1-Targeting Small Molecule Covalent Inhibitors As Anticancer Agents

Programmed death protein 1(PD-1)/programmed death protein ligand 1(PD-L1)pathway is currently attracting attention for cancer therapy.However,small molecule covalent inhibitors with powerful therapeutic advantages have been less developed in this field.In a continuation of our research interest in this pathway,we synthesized and evaluated the pharmacological activities of a series of small molecule PD-1/PD-L1 covalent inhibitors GJ1-GJ26 for tumor treatment.Among them,GJ12 showed distinguished inhibitory effect against PD-1/PDL-1 with an IC50 value of 32.06 nM in the HTRF(homogenous time-resolved fluorescence)assay,and the data were smaller than positive drugs BMS-202(IC50=62.1nM)tested in the same batch.The results of SPR experiments showed that GJ12 was tightly bound to PD-L1 protein,and the KD values of human PD-L1 and murine PD-L1 protein were 171 nM and 290 nM.respectively,so it could competitively inhibit the binding of PD-1 to PD-L1.In the antitumor cell proliferation activity experiment,all 6 compounds of the GJ series showed low or no toxicity;Furthermore,GJ12 concentration-dependently promoted HepG2 cell mortality in a co-culture model of HepG2/hPD-Ll and Jurkat T cells.Other mass spectrometry experiments have shown that the molecular weight of GJ12 and lysine are added after co-incubation,and a covalent bond may be formed between the two.In summary,GJ12 has a good inhibitory effect of PD-1/PD-L1,and there may be covalent bonds between GJ12 and PD-L1,which may be a good start for small molecule covalent inhibitors of PD-L1 in tumor treatment.