Adenosine A 2A Receptor (A 2A AR) Ligand Screening Using the 19 F-NMR Probe FPPA.

The binding affinity of G protein-coupled receptor (GPCR) ligands is customarily measured by radio-ligand competition experiments. As an alternative approach, 19 F nuclear magnetic resonance spectroscopy (19 F-NMR) is used for the screening of small-molecule lead compounds in drug discovery; the two methods are complementary in that the measurements are performed with widely different experimental conditions. Here, we used the structure of the A2A adenosine receptor (A2A AR) complex with V-2006 (3-(4-amino-3-methylbenzyl)-7-(furan-2-yl)-3 H -[1,2,3]triazolo[4,5- d ]pyrimidin-5-amine) as the basis for the design of a fluorine-containing probe molecule, FPPA (4-(furan-2-yl)-7-(4-(trifluoromethyl)benzyl)-7 H -pyrrolo[2,3- d ]pyramidin-2-amine), for binding studies with A2A AR. A protocol of experimental conditions for drug screening and measurements of drug binding affinities using 1D 19 F-NMR observation of FPPA is validated with studies of known A2A AR ligands. 19 F-NMR with FPPA is thus found to be a robust approach for the discovery of ligands with new core structures, which will expand the libraries of A2A AR-targeting drug candidates.