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Human arylacetamide deacetylase (AADAC) plays a role in the detoxification or activation of drugs and is sometimes involved in the incidence of toxicity by catalyzing hydrolysis reactions. AADAC prefers compounds with relatively small acyl groups, such as acetyl groups. Eslicarbazepine acetate, an antiepileptic drug, is a prodrug rapidly hydrolyzed to eslicarbazepine. We sought to clarify whether AADAC might be responsible for the hydrolysis of eslicarbazepine acetate. Eslicarbazepine acetate was efficiently hydrolyzed by human intestinal and liver microsomes and recombinant human AADAC. The hydrolase activities in human intestinal and liver microsomes were inhibited by epigallocatechin gallate, a specific inhibitor of AADAC, by 82% and 88% of the control, respectively. The hydrolase activities in liver microsomes from 25 human livers were significantly correlated (r = 0.87, P < 0.001) with AADAC protein levels, suggesting that the enzyme AADAC is responsible for the hydrolysis of eslicarbazepine acetate. The effects of genetic polymorphisms of AADAC on eslicarbazepine acetate hydrolysis were examined by using the constructed recombinant AADAC variants with T74A, V172I, R248S, V281I, N366K, or X400Q. AADAC variants with R248S or X400Q showed lower activity than wild type (5% or 21%, respectively), whereas those with V172I showed higher activity than wild type (174%). Similar tendencies were observed in the other 4 substrates of AADAC; that is, p-nitrophenyl acetate, ketoconazole, phenacetin, and rifampicin. Collectively, we found that eslicarbazepine acetate is specifically and efficiently hydrolyzed by human AADAC, and several AADAC polymorphic alleles would be a factor affecting the enzyme activity and drug response.

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Background and Purpose Orally administered ketoconazole rarely induces liver injury and adrenal dysfunction. In cellulo studies showed that a metabolite formed by arylacetamide deacetylase (AADAC)-mediated hydrolysis is relevant to ketoconazole-induced cytotoxicity. This study tried to examine the significance of AADAC in ketoconazole-induced toxicity in vivo using Aadac knockout mice. Experimental Approach Wild-type and Aadac knockout mice orally received 150 or 300 mg/kg/day ketoconazole, and plasma parameters, the concentrations of ketoconazole and N-deacetylketoconazole in plasma and tissues, and hepatic mRNA levels of immune- and inflammatory-related factors were measured. The effects of pretreatment with corticosterone (40 mg/kg, s.c.) on ketoconazole-induced liver injury were also examined. Key Results In a study of a single oral administration of 150 mg/kg ketoconazole, the area under the plasma concentration curve values of ketoconazole and N-deacetylketoconazole in Aadac knockout mice were significantly higher and lower than those in wild-type mice, respectively. With the administration of ketoconazole (300 mg/kg/day) for 7 days, Aadac knockout mice showed higher mortality (100%) than wild-type mice (42.9%), with significantly higher plasma alanine transaminase and lower corticosterone levels, representing liver injury and adrenal dysfunction, respectively. In Aadac knockout mice, hepatic mRNA levels of immune- and inflammatory-related factors were increased by the administration of ketoconazole, and the increase was restored by the replenishment of corticosterone, which shows anti-inflammatory effects. Conclusion and Implications Aadac defects exacerbated ketoconazole-induced liver injury by inhibiting glucocorticoid synthesis and enhancing the inflammatory response. This in vivo study revealed that the hydrolysis of ketoconazole by AADAC can mitigate ketoconazole-induced toxicities.