Discovery of N -Acetyltransferase 8-Like (NAT8L) Inhibitors Based on a N -Acylated (Piperidin-3-ylmethyl)-1,2,4-Oxadiazole Scaffold

Canavan disease (CD) is an autosomal recessive genetic disorder caused by mutations in the ASPA gene, which encodes the enzyme aspartoacylase. These mutations lead to a deficient enzymatic activity and increased concentrations of its substrate, N-acetylaspartate (NAA), in the brain and other tissues. Aspartate N-acetyltransferase, encoded by the N-acetyltransferase 8-like (NAT8L) gene, catalyzes the biosynthesis of NAA from aspartate and acetyl-CoA. Therefore, inhibition of NAT8L has been implicated as a promising therapeutic strategy for CD by normalizing NAA levels in the brain. Our high throughput screening campaign followed by a rigorous hit validation process identified 2-(2-fluorophenoxy)-1-(3-((3-(thiophen-3-yl)-1,2,4-oxadiazol-5-yl)methyl)piperidin-1-yl)ethan-1-one (4a) as a low micromolar, noncarboxylic acid inhibitor of NAT8L. Subsequent structural optimization led to the discovery of two submicromolar NAT8L inhibitors. Although these inhibitors displayed high clearance in liver microsomes, the new scaffold, devoid of a carboxylic acid moiety, could potentially lead to potent and brain-penetrant NAT8L inhibitors through further molecular refinement.