Design, Synthesis, and Evaluation of a New Chemotype Fluorescent Ligand for the P2Y 2 Receptor.

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