Selective Fluorescent Nonpeptidic Antagonists For Vasopressin V2 GPCR: Application To Ligand Screening and Oligomerization Assays

A series of fluorescent benzazepine ligands for the arginine-vasopressin V-2 receptor (AVP V2R) was synthesized using Click chemistry. Their in vitro pharmacological profile at AVP V2R, V1aR, V1bR, and oxytocin receptor was measured by binding assay and functional studies. Compound 9p, labeled with Lissamine Rhodamine B using novel solid-phase organic tagging (SPOrT) resin, exhibited a high affinity for V2R (4.0 nM), an excellent selectivity toward V2R and antagonist properties. By changing the nature of the dye, DY647 and Lumi4-Tb probes 44 and 47 still display a high affinity for V2R (5.6 and 5.8 nM, respectively). These antagonists constitute the first high-affinity selective nonpeptidic fluorescent ligands for V2R. They enabled the development of V2R time-resolved FRET-based assay readily amenable to high-throughput screening. Taking advantage of their selectivity, these compounds were also successfully involved in the study of V1aR-V2R dimerization on cell surface.