Superagonism at the Human Somatostatin Receptor Subtype 4

Abstract

We have discovered a novel compound, J-2156 [(1S, 2S)-4-amino-N-(1-carbamoyl-2-phenylethyl)-2-(4-methyl-1-naph-thalenesulfonylamino)butanamide], that belongs to a new class of somatostatin receptor ligands. J-2156 binds with nanomolar affinity to the human somatostatin receptor subtype 4 and is over 400-fold subtype-selective against the other somatostatin receptors. When evaluated in a [35S]guanosine-5-O-(3-thio) triphosphate binding assay, J-2156 elicited a response 2 to 3 times as large as that of somatostatin-28 and somatostatin-14. That somatostatin-14 is clearly not a maximally efficacious agonist could be verified by demonstrating that it displays the typical behavior of a partial agonist when tested against J-2156. Increasing concentrations of somatostatin-14 cause a concentration-dependent rightward shift of the dose-respons