Discovery of novel N-(1-benzyl-1H-imidazol-2-yl)amide derivatives as melanocortin 1 receptor agonists

Abstract

Melanocortin-1 receptor (MC1R) is primarily activated by α-melanocyte-stimulating hormone (α-MSH) and plays a crucial role, such as keeping homeostasis in the skin against melanogenesis and external stimuli, anti-inflammatory effects, and tissue fibrosis suppression. Afamelanotide, an α-MSH analog MC1R agonist, is clinically used for treating erythroblastic protoporphyria (EPP) by subcutaneous implantation administration. Therefore, we initiated an investigation aimed at orally available small molecule nonpeptide MC1R agonists. Optimization from the internal hit compound 6a finally resulted in the discovery of N-(1-benzyl-1H-imidazol-2-yl)amide derivative 9g bearing isonipecotinic acid moiety, which demonstrated good MC1R agonistic activity and metabolic stability.