Structure―activity relationships of trans-substituted-propenoic acid derivatives on the nicotinic acid receptor HCA2 (GPR109A)

Abstract Nicotinic acid (niacin) has been used for decades as an antidyslipidemic drug in man. Its main target is the hydroxy-carboxylic acid receptor HCA2 (GPR109A), a G protein-coupled receptor. Other acids and esters such as methyl fumarate also interact with the receptor, which constituted the basis for the current study. We synthesized a novel series of substituted propenoic acids, such as fumaric acid esters, fumaric acid amides and cinnamic acid derivatives, and determined their affinities for the HCA2 receptor. We observed a rather restricted binding pocket on the receptor with trans -cinnamic acid being the largest planar ligand in our series with appreciable affinity for the receptor. Molecular modeling and analysis of the structure–activity relationships in the series suggest a planar trans -propenoic acid pharmacophore with a maximum length of 8 A and out-of-plane orientation of the larger substituents.