 The regulation of expression of AO is still not completely known, though some studies have shown that the AOX1 gene is regulated by the Nrf2 pathway.Some known inhibitors of AO are sterol and phenol compounds, like estradiol.Others include amsacrine, 6,6'-azopurine, chlorpromazine, cimetidine, cyanide, diethylstilbestrol, genestein, isovanillin, and methadone.