Discovery and Pharmacology of a Novel Somatostatin Subtype 5 (SSTR5) Antagonist: Synergy with DPP-4 Inhibition

Abstract

We report new SSTR5 antagonists with enhanced potency, subtype selectivity, and minimal off-target activities as compared to previously reported compounds. Starting from the reported SSTR5 antagonist <b>1</b>, we systematically surveyed changes in the central core and head piece while maintaining the diphenyl tail group constant. From this study the azaspirodecanone <b>10</b> emerged as a new highly potent and selective SSTR5 antagonist. Compound <b>10</b> lowered glucose excursion by 94% in an oral glucose tolerance test (OGTT) in mice following a 3 mg/kg oral dose. The compound increased both total and active circulating incretin hormone GLP-1 levels in mice at a dose of 10 mg/kg. A synergistic effect was also demonstrated when compound <b>10</b> was coadministered with a DPP-4 inhibitor, substantially increasing circulating active GLP-1[7-36] amide and insulin in response to a glucose challenge.