Discovery of Selective Inhibitors of Endoplasmic Reticulum Aminopeptidase 1

ERAP1 is an endoplasmic reticulum-resident zinc aminopeptidase
that plays an important role in the immune system by trimming peptides
for loading onto major histocompatibility complex proteins. Here,
we report discovery of the first inhibitors selective for ERAP1 over
its paralogues ERAP2 and IRAP. Compound 1 (N-(N-(2-(1H-indol-3-yl)­ethyl)­carbamimidoyl)-2,5-difluorobenzenesulfonamide)
and compound 2 (1-(1-(4-acetylpiperazine-1-carbonyl)­cyclohexyl)-3-(p-tolyl)­urea) are competitive inhibitors of ERAP1 aminopeptidase
activity. Compound 3 (4-methoxy-3-(N-(2-(piperidin-1-yl)-5-(trifluoromethyl)­phenyl)­sulfamoyl)­benzoic
acid) allosterically activates ERAP1’s hydrolysis of fluorogenic
and chromogenic amino acid substrates but competitively inhibits its
activity toward a nonamer peptide representative of physiological
substrates. Compounds 2 and 3 inhibit antigen
presentation in a cellular assay. Compound 3 displays
higher potency for an ERAP1 variant associated with increased risk
of autoimmune disease. These inhibitors provide mechanistic insights
into the determinants of specificity for ERAP1, ERAP2, and IRAP and
offer a new therapeutic approach of specifically inhibiting ERAP1
activity in vivo.