Discovery of a N′-hydroxyphenylformamidine derivative HET0016 as a potent and selective 20-HETE synthase inhibitor

N-(4-Butyl-2-methylphenyl)-N′-hydroxyformamidine (HET0016) was evaluated as the first potent and selective inhibitor of 20-hydroxy-5,8,11,14-eicosatetraenoic acid (20-HETE) synthase. The IC50 value of HET0016 for the production of 20-HETE from arachidonic acid (AA) by human renal microsomes was 8.9±2.7 nM, with over 200 times the selectivity of xenobiotic-metabolizing cytochrome P450 enzymes. An examination of the structure–activity relationship revealed that the unsubstituted hydroxyformamidine moiety and the substituent at the para-position of the N-hydroxyformamidine moiety are necessary for the potent activity of HET0016.