title: A humanized UGT1 mouse model expressing the UGT1A1*28 allele for assessing drug clearance by UGT1A1-dependent glucuronidation.
abstract: Humanized mice that express the human UDP-glucuronosyltransferase (UGT) 1 locus have been developed in a Ugt1-null background as a model to improve predictions of human UGT1A-dependent drug clearance. Enzyme kinetic parameters (K(m) and V(max)) and pharmacokinetic properties of three probe drugs were compared using wild-type and humanized UGT1 mice that express the Gilbert's UGT1A1*28 allele [Tg(UGT1(A1*28)) Ugt1(-/-) mice]. The well characterized substrate for UGT1A1, 7-ethyl-10-hydroxy-camptothecin (SN-38), showed the greatest difference in parent drug exposure ( approximately 3-fold increase) and clearance ( approximately 3-fold decrease) in Tg(UGT1(A1*28)) Ugt1(-/-) mice after intravenous administration compared with wild-type and phenobarbital-treated animals. In contrast, the clearance of the UGT2B7 substrate (-)-17-allyl-4, 5alpha-epoxy-3, 14-dihydroxymorphinan-6-one (naloxone) was not altered in Tg(UGT1(A1*28)) Ugt1(-/-) mice. In addition, pharmacokinetic parameters with 1-(4-fluorophenyl)3(R)-[3-(4-fluorophenyl)-3(S)-hydroxypropyl]-4(S)-(4-hydroxyphenyl)-2-azetidinone (ezetimibe, Zetia; Merck & Co., Whitehouse Station, NJ), considered to be a major substrate for UGT1A1, showed small to no dependence on UGT1A1-directed glucuronidation. Enzyme kinetic parameters assessed for SN-38, ezetimibe, and naloxone using liver microsomes prepared from wild-type and Tg(UGT1(A1*28)) Ugt1(-/-) mice showed patterns consistent with the in vivo pharmacokinetic data. For SN-38 glucuronidation, V(max) decreased 5-fold in Tg(UGT1(A1*28)) Ugt1(-/-) mouse liver microsomes compared with microsomes prepared from wild-type mice, and decreased 10-fold compared with phenobarbital-treated Tg(UGT1(A1*28)) Ugt1(-/-) mice. These differences are consistent with SN-38 glucuronidation activities using HLMs isolated from individuals genotyped as UGT1A1*1 or UGT1A1*28. For ezetimibe and naloxone the differences in V(max) were minimal. Thus, Tg(UGT1(A1*28)) Ugt1(-/-) mice can serve as a pharmacokinetic model to further investigate the effects of UGT1A1 expression on drug metabolism.
authors.affiliation: Department of Pharmacokinetics, Dynamics, and Metabolism, St. Louis Laboratories, Pfizer Global Research and Development, Chesterfield, MO 63017, USA.
authors.forename: Hongliang
authors.initials: H
authors.lastname: Cai
authors.forename: Nghia
authors.initials: N
authors.lastname: Nguyen
authors.forename: Vincent
authors.initials: V
authors.lastname: Peterkin
authors.forename: Young-Sun
authors.initials: YS
authors.lastname: Yang
authors.forename: Kathy
authors.initials: K
authors.lastname: Hotz
authors.forename: Deirdre Beaton
authors.initials: DB
authors.lastname: La Placa
authors.forename: Shujuan
authors.initials: S
authors.lastname: Chen
authors.forename: Robert H
authors.initials: RH
authors.lastname: Tukey
authors.forename: Jeffrey C
authors.initials: JC
authors.lastname: Stevens
mesh_terms: D000483:Alleles; D000818:Animals; D000924:Anticholesteremic Agents / Q000378:metabolism / Q000493:pharmacokinetics; D000972:Antineoplastic Agents, Phytogenic / Q000378:metabolism / Q000493:pharmacokinetics; D019540:Area Under Curve; D001384:Azetidines / Q000378:metabolism / Q000493:pharmacokinetics; D055162:Biocatalysis; D002166:Camptothecin / Q000031:analogs & derivatives / Q000378:metabolism / Q000493:pharmacokinetics; D004121:Dimethyl Sulfoxide / Q000494:pharmacology; D004790:Enzyme Induction / Q000187:drug effects / Q000235:genetics; D000069438:Ezetimibe; D015870:Gene Expression / Q000187:drug effects / Q000235:genetics; D020723:Glucuronic Acid / Q000378:metabolism*; D014453:Glucuronosyltransferase / Q000235:genetics* / Q000378:metabolism*; D006801:Humans; D000077146:Irinotecan; D007700:Kinetics; D008099:Liver / Q000187:drug effects / Q000378:metabolism; D008297:Male; D008657:Metabolic Clearance Rate; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008822:Mice, Transgenic; D008862:Microsomes, Liver / Q000187:drug effects / Q000378:metabolism; D023421:Models, Animal; D009270:Naloxone / Q000378:metabolism / Q000493:pharmacokinetics; D004364:Pharmaceutical Preparations / Q000378:metabolism*; D010634:Phenobarbital / Q000494:pharmacology; D000090264:UDP-Glucuronosyltransferase 1A9; D000099148:UGT1A1 Enzyme
chemical_list: D000924:Anticholesteremic Agents; D000972:Antineoplastic Agents, Phytogenic; D001384:Azetidines; D002166:Camptothecin; D004121:Dimethyl Sulfoxide; D000069438:Ezetimibe; D020723:Glucuronic Acid; D014453:Glucuronosyltransferase; D000077146:Irinotecan; D009270:Naloxone; D004364:Pharmaceutical Preparations; D010634:Phenobarbital; D000090264:UDP-Glucuronosyltransferase 1A9; D000099148:UGT1A1 Enzyme; C019787:bilirubin glucuronoside glucuronosyltransferase; C122075:UDP-glucuronosyltransferase, UGT1A3; C110655:UDP-glucuronosyltransferase, UGT1A6