Discovery and structure-activity relationship study of 4-phenoxythiazol-5-carboxamides as highly potent TGR5 agonists

Abstract

A novel therapy that stimulates endogenous glucagon-like peptide-1 (GLP-1) secretion by Takeda G-protein-coupled receptor 5 (TGR5) agonists might be a superior alternative for the treatment of type 2 diabetes mellitus. A series of 4-phenoxythiazol-5-carboxamides were developed as highly potent TGR5 agonists using a bioisosteric replacement strategy based on the scaffold of 4-phenoxynicotinamides. The structure−activity relationship on the bottom phenyl ring and the thiazole ring was extensively studied, and the 2-methyl-thiazole derivatives 30c and 30e displayed the best in vitro potency toward human TGR5, with EC₅₀ values of approximately 1 nM. While endowed with excellent in vitro potency, the 2-methyl-thiazoles were flawed with high microsomal clearance.