Design, Synthesis, and Evaluation of a New Chemotype Fluorescent Ligand for the P2Y Receptor.

The P2Y receptor (P2YR) is a target for diseases including cancer, idiopathic pulmonary fibrosis, and atherosclerosis. However, there are insufficient P2YR antagonists available for validating P2YR function and future drug development. Evaluation of how ()-5-(7-chloro-2-((2-ethoxyethyl)amino)-4-benzo[5,6]cyclohepta[1,2-]thiazol-4-yl)-1-methyl-4-thioxo-3,4-dihydropyrimidin-2(1)-one, a previously published thiazole-based analogue of AR-C118925, binds in a P2YR homology model was used to design new P2YR antagonist scaffolds. One P2YR antagonist scaffold retained millimolar affinity for the P2YR and upon further functionalization with terminal carboxylic acid groups affinity was improved over 100-fold. This functionalized P2YR antagonist scaffold was employed to develop new chemotype P2YR fluorescent ligands, that were attainable in a convergent five-step synthesis. One of these fluorescent ligands demonstrated micromolar affinity (p = 6.02 ± 0.12, = 5) for the P2YR in isolated cell membranes and distinct pharmacology from an existing P2YR fluorescent antagonist, suggesting it may occupy a different binding site on the P2YR.