title: Evaluating the Disposition of a Mixed Aldehyde Oxidase/Cytochrome P450 Substrate in Rats with Attenuated P450 Activity.
abstract: Marketed drugs cleared by aldehyde oxidase (AO) are few, with no known clinically relevant pharmacokinetic drug interactions associated with AO inhibition, whereas cytochrome P450 (P450) inhibition or induction mediates a number of clinical drug interactions. Little attention has been given to the consequences of coadministering a P450 inhibitor with a compound metabolized by both AO and P450. Upon discovering that VU0409106 (1) was metabolized by AO (to M1) and P450 enzymes (to M4-M6), we sought to evaluate the in vivo disposition of 1 and its metabolites in rats with attenuated P450 activity. Male rats were orally pretreated with the pan-P450 inactivator, 1-aminobenzotriazole (ABT), before an i.p. dose of 1. Interestingly, the plasma area under the curve (AUC) of M1 was increased 15-fold in ABT-treated rats, indicating a metabolic shunt toward AO resulted from the drug interaction condition. The AUC of 1 also increased 7.8-fold. Accordingly, plasma clearance of 1 decreased from 53.5 to 15.3 ml/min per kilogram in ABT-pretreated rats receiving an i.v. dose of 1. Consistent with these data, M1 formation in hepatic S9 increased with NADPH-exclusion to eliminate P450 activity (50% over reactions containing NADPH). These studies reflect possible consequences of a drug interaction between P450 inhibitors and compounds cleared by both AO and P450 enzymes. Notably, increased exposure to an AO metabolite may hold clinical relevance for active metabolites or those mediating toxicity at elevated concentrations. The recent rise in clinical drug candidates metabolized by AO underscores the importance of these findings and the need for clinical studies to fully understand these risks.
authors.affiliation: Vanderbilt Center for Neuroscience Drug Discovery (R.D.C., R.D.M., F.W.B., C.W.L., K.A.E., J.S.D.), Departments of Pharmacology (R.D.C., C.W.L, K.A.E., J.S.D.) and Chemistry (C.W.L, K.A.E.), Vanderbilt University School of Medicine, Nashville, Tennessee.
authors.forename: Rachel D
authors.initials: RD
authors.lastname: Crouch
authors.affiliation: Vanderbilt Center for Neuroscience Drug Discovery (R.D.C., R.D.M., F.W.B., C.W.L., K.A.E., J.S.D.), Departments of Pharmacology (R.D.C., C.W.L, K.A.E., J.S.D.) and Chemistry (C.W.L, K.A.E.), Vanderbilt University School of Medicine, Nashville, Tennessee.
authors.forename: Ryan D
authors.initials: RD
authors.lastname: Morrison
authors.affiliation: Vanderbilt Center for Neuroscience Drug Discovery (R.D.C., R.D.M., F.W.B., C.W.L., K.A.E., J.S.D.), Departments of Pharmacology (R.D.C., C.W.L, K.A.E., J.S.D.) and Chemistry (C.W.L, K.A.E.), Vanderbilt University School of Medicine, Nashville, Tennessee.
authors.forename: Frank W
authors.initials: FW
authors.lastname: Byers
authors.affiliation: Vanderbilt Center for Neuroscience Drug Discovery (R.D.C., R.D.M., F.W.B., C.W.L., K.A.E., J.S.D.), Departments of Pharmacology (R.D.C., C.W.L, K.A.E., J.S.D.) and Chemistry (C.W.L, K.A.E.), Vanderbilt University School of Medicine, Nashville, Tennessee.
authors.forename: Craig W
authors.initials: CW
authors.lastname: Lindsley
authors.affiliation: Vanderbilt Center for Neuroscience Drug Discovery (R.D.C., R.D.M., F.W.B., C.W.L., K.A.E., J.S.D.), Departments of Pharmacology (R.D.C., C.W.L, K.A.E., J.S.D.) and Chemistry (C.W.L, K.A.E.), Vanderbilt University School of Medicine, Nashville, Tennessee.
authors.forename: Kyle A
authors.initials: KA
authors.lastname: Emmitte
authors.affiliation: Vanderbilt Center for Neuroscience Drug Discovery (R.D.C., R.D.M., F.W.B., C.W.L., K.A.E., J.S.D.), Departments of Pharmacology (R.D.C., C.W.L, K.A.E., J.S.D.) and Chemistry (C.W.L, K.A.E.), Vanderbilt University School of Medicine, Nashville, Tennessee scott@thinksano.com.
authors.forename: J Scott
authors.initials: JS
authors.lastname: Daniels
mesh_terms: D000284:Administration, Oral; D042931:Aldehyde Oxidase / Q000378:metabolism*; D000818:Animals; D019540:Area Under Curve; D001549:Benzamides / Q000008:administration & dosage / Q000378:metabolism / Q000493:pharmacokinetics*; D001711:Biotransformation; D065607:Cytochrome P-450 Enzyme Inhibitors / Q000008:administration & dosage / Q000494:pharmacology*; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D004347:Drug Interactions; D006801:Humans; D008297:Male; D008657:Metabolic Clearance Rate; D008862:Microsomes, Liver / Q000201:enzymology; D017207:Rats, Sprague-Dawley; D018570:Risk Assessment; D013379:Substrate Specificity; D013844:Thiazoles / Q000008:administration & dosage / Q000378:metabolism / Q000493:pharmacokinetics*; D014230:Triazoles / Q000008:administration & dosage / Q000493:pharmacokinetics*
chemical_list: D001549:Benzamides; D065607:Cytochrome P-450 Enzyme Inhibitors; D013844:Thiazoles; D014230:Triazoles; C577470:VU0409106; C033020:1-aminobenzotriazole; D003577:Cytochrome P-450 Enzyme System; D042931:Aldehyde Oxidase