Design, Synthesis, and Antitumor Activity Evaluation of Novel VISTA Small Molecule Inhibitors

Abstract

VISTA (V-domain Ig suppressor of T cell activation) is a novel immune checkpoint protein and represents a promising target for cancer immunotherapy. Here, we report the design, synthesis, and evaluation of a series of methoxy-pyrimidine-based VISTA small molecule inhibitors with potent antitumor activity. By employing molecular docking and microscale thermophoresis (MST) assay, we identified a lead compound <b>A1</b> that binds to VISTA protein with high affinity and optimized its structure. <b>A4</b> was then obtained, which exhibited the strongest binding ability to VISTA protein, with a <i>K</i>_D value of 0.49 ± 0.20 μM. <i>In vitro</i>, <b>A4</b> significantly activated peripheral blood mononuclear cells (PBMCs) induced the release of cytokines such as IFN-γ and enhanced the cytotoxicity of PBMCs against tumor cells. <i>In vivo</i>, <b>A4</b> displayed potent antitumor activity and synergized with PD-L1 antibody to enhance the therapeutic effect against cancer. These results suggest that compound <b>A4</b> is an effective VISTA small molecule inhibitor, providing a basis for the future development of VISTA-targeted drugs.