title: Stereoselectivity in metabolism of ifosfamide by CYP3A4 and CYP2B6.
abstract: The aim was to identify the hepatic cytochromes P450 (CYPs) responsible for the enantioselective metabolism of ifosfamide (IFA). The 4-hydroxylation, N2- and N3-dechloroethylation of IFA enantiomers were monitored simultaneously in the same metabolic systems using GC/MS and pseudoracemate techniques. In human and rat liver microsomes, (R)-IFA was preferentially metabolized via 4-hydroxylation, whereas its antipode was biotransformed in favour of N-dechloroethylation. CYP3A4 was the major enzyme responsible for metabolism of IFA enantiomers in human liver. The study also revealed that CYP3A (human CYP3A4/5 and rat CYP3A1/2) and CYP2B (human CYP2B6 and rat CYP2B1/2) enantioselectively mediated the 4-hydroxylation, N2- and N3-dechloroethylation of IFA. CYP3A preferentially supported the formation of (R)-4-hydroxyIFA (HOIF), (R)-N2-dechloroethylIFA (N2D) and (R)-N3-dechloroethylIFA (N3D), whereas CYP2B preferentially mediated the generation of (S)-HOIF, (S)-N2D and (S)-N3D. The enantioselective metabolism of IFA by CYP3A4 and CYP2B1 was confirmed in cDNA transfected V79 cells.
authors.affiliation: College of Pharmacy, Comprehensive Cancer Center, Ohio State University, Columbus, OH, USA. hl97578@gsk.com
authors.forename: H
authors.initials: H
authors.lastname: Lu
authors.forename: J J
authors.initials: JJ
authors.lastname: Wang
authors.forename: K K
authors.initials: KK
authors.lastname: Chan
authors.forename: P A
authors.initials: PA
authors.lastname: Philip
mesh_terms: D000818:Animals; D018906:Antineoplastic Agents, Alkylating / Q000493:pharmacokinetics* / Q000494:pharmacology; D001189:Aryl Hydrocarbon Hydroxylases / Q000378:metabolism*; D001711:Biotransformation; D002460:Cell Line; D065702:Cytochrome P-450 CYP2B6; D051544:Cytochrome P-450 CYP3A; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D006801:Humans; D007069:Ifosfamide / Q000493:pharmacokinetics* / Q000494:pharmacology; D008297:Male; D008862:Microsomes, Liver / Q000201:enzymology*; D010089:Oxidoreductases, N-Demethylating / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013237:Stereoisomerism; D013379:Substrate Specificity
chemical_list: D018906:Antineoplastic Agents, Alkylating; D003577:Cytochrome P-450 Enzyme System; D001189:Aryl Hydrocarbon Hydroxylases; C585599:CYP2B6 protein, human; C465260:Cyp3a2 protein, rat; D065702:Cytochrome P-450 CYP2B6; D051544:Cytochrome P-450 CYP3A; C510163:CYP3A4 protein, human; D010089:Oxidoreductases, N-Demethylating; D007069:Ifosfamide