In vitro characterization of a small molecule PD-1 inhibitor that targets the PD-l/PD-L1 interaction

Chun-Hao Tsai,Ju-Chien Cheng,Huey-En Tzeng,Chih-Hao Lu,Kai-Cheng Hsu,Wei-Min Chung

doi:10.1038/s41598-021-03590-4

Abstract

Targeting the programmed cell death protein 1/programmed cell death ligand 1 (PD-1/PD-L1) axis with monoclonal antibodies (mAbs) represents a crucial breakthrough in anticancer therapy, but mAbs are limited by their poor oral bioavailability, adverse events in multiple organ systems, and primary, adaptive, and acquired resistance, amongst other issues. More recently, the advent of small molecule inhibitors that target the PD-1/PD-L1 axis have shown promising cellular inhibitory activity and the potential to counteract the disadvantages of mAbs. In this study, structure-based virtual screening identified small molecule inhibitors that effectively inhibited the PD-1/PD-L1 interaction. Six of those small molecule inhibitors were applied to cell-based experiments targeting PD-1: CH-1, CH-2, CH-3, CH-4, CH-5, and CH-6. Of all 6, CH-4 displayed the lowest cytotoxicity and strongest inhibitory activity towards the PD-1/PD-L1 interaction. The experiments revealed that CH-4 inhibited the interaction of soluble form PD-L1 (sPD-L1) with PD-1 surface protein expressed by KG-1 cells. Investigations into CH-4 analogs revealed that CH-4.7 effectively blocked the PD-1/sPD-L1 interaction, but sustained the secretion of interleukin-2 and interferon-γ by Jurkat cells. Our experiments revealed a novel small molecule inhibitor that blocks the interaction of PD-1/sPD-L1 and potentially offers an alternative PD-1 target for immune checkpoint therapy.

Highlights

Targeting the programmed cell death protein 1/programmed cell death ligand 1 (PD-1/PD-L1) axis with monoclonal antibodies represents a crucial breakthrough in anticancer therapy, but mAbs are limited by their poor oral bioavailability, adverse events in multiple organ systems, and primary, adaptive, and acquired resistance, amongst other issues
Many countries, including the United States, Japan and Europe, have approved several anti-PD-1/PD-L1 therapies for treating multiple tumors, including head and neck cancer, melanoma, lung cancer, and ovarian cancer[11,12,13]. The benefits of such treatment are not limited to cancer, with evidence suggesting that regulating the immune response via the PD-1/PD-L1 interaction can apply to infectious diseases such as tuberculosis, human immunodeficiency virus (HIV) infection, hepatitis and m alaria[14,15,16,17]
The six available compounds were quantified for cytotoxicity and inhibitory capacities, using an in vitro cell cytotoxicity assay and a cell-based PD-1/PD-L1 inhibitor screening assay

Summary

Introduction

Targeting the programmed cell death protein 1/programmed cell death ligand 1 (PD-1/PD-L1) axis with monoclonal antibodies (mAbs) represents a crucial breakthrough in anticancer therapy, but mAbs are limited by their poor oral bioavailability, adverse events in multiple organ systems, and primary, adaptive, and acquired resistance, amongst other issues. By negatively regulating the immune system, programmed cell death protein 1 (PD-1) helps to prevent the development of autoimmune d isease[1,2] When this immune checkpoint binds to its ligand, programmed cell death ligand 1 (PD-L1), the resulting interaction inhibits immune responses, stimulates the release of cytokines and triggers cytotoxic reactions[3], suppressing T cell functions[4]. Many countries, including the United States, Japan and Europe, have approved several anti-PD-1/PD-L1 therapies for treating multiple tumors, including head and neck cancer, melanoma, lung cancer, and ovarian cancer[11,12,13] The benefits of such treatment are not limited to cancer, with evidence suggesting that regulating the immune response via the PD-1/PD-L1 interaction can apply to infectious diseases such as tuberculosis, human immunodeficiency virus (HIV) infection, hepatitis and m alaria[14,15,16,17]

Methods

Results

Conclusion