Design, Synthesis, and Evaluation of a New Chemotype Fluorescent Ligand for the P2Y2 Receptor

Abstract

The P2Y2 receptor (P2Y2R) is a target for diseases including cancer, idiopathic pulmonary fibrosis, and atherosclerosis. However, there are insufficient P2Y2R antagonists available for validating P2Y2R function and future drug development. Evaluation of how (R)-5-(7-chloro-2-((2-ethoxyethyl)amino)-4H-benzo[5,6]cyclohepta[1,2-d]thiazol-4-yl)-1-methyl-4-thioxo-3,4-dihydropyrimidin-2(1H)-one, a previously published thiazole-based analogue of AR-C118925, binds in a P2Y2R homology model was used to design new P2Y2R antagonist scaffolds. One P2Y2R antagonist scaffold retained millimolar affinity for the P2Y2R and upon further functionalization with terminal carboxylic acid groups affinity was improved over 100-fold. This functionalized P2Y2R antagonist scaffold was employed to develop new chemotype P2Y2R fluorescent ligands, that were attainable in a convergent five-step synthesis. One of these fluorescent ligands demonstrated micromolar affinity (pKd = 6.02 ± 0.12, n = 5) for the P2Y2R in isolated cell membranes and distinct pharmacology from an existing P2Y2R fluorescent antagonist, suggesting it may occupy a different binding site on the P2Y2R.