title: Effects of cytochrome P450 3A (CYP3A) and the drug transporters P-glycoprotein (MDR1/ABCB1) and MRP2 (ABCC2) on the pharmacokinetics of lopinavir.
abstract: OBJECTIVE
  Lopinavir is extensively metabolized by cytochrome P450 3A (CYP3A) and is considered to be a substrate for the drug transporters ABCB1 (P-glycoprotein) and ABCC2 (MRP2). Here, we have assessed the individual and combined effects of CYP3A, ABCB1 and ABCC2 on the pharmacokinetics of lopinavir and the relative importance of intestinal and hepatic metabolism. We also evaluated whether ritonavir increases lopinavir oral bioavailability by inhibition of CYP3A, ABCB1 and/or ABCC2.
  
  
  METHODS
  Lopinavir transport was measured in Madin-Darby canine kidney cells expressing ABCB1 or ABCC2. Oral lopinavir kinetics (+/- ritonavir) was studied in mice with genetic deletions of Cyp3a, Abcb1a/b and/or Abcc2, or in transgenic mice expressing human CYP3A4 exclusively in the liver and/or intestine.
  
  
  RESULTS
  Lopinavir was transported by ABCB1 but not by ABCC2 in vitro. Lopinavir area under the plasma concentration - time curve (AUC)(oral) was increased in Abcb1a/b(-/-) mice (approximately ninefold vs. wild-type) but not in Abcc2(-/-) mice. Increased lopinavir AUC(oral) (>2000-fold) was observed in cytochrome P450 3A knockout (Cyp3a(-/-)) mice compared with wild-type mice. No difference in AUC(oral) between Cyp3a(-/-) and Cyp3a/Abcb1a/b/Abcc2(-/-) mice was observed. CYP3A4 activity in intestine or liver, separately, reduced lopinavir AUC(oral) (>100-fold), compared with Cyp3a(-/-) mice. Ritonavir markedly increased lopinavir AUC(oral) in all CYP3A-containing mouse strains.
  
  
  CONCLUSIONS
  CYP3A was the major determinant of lopinavir pharmacokinetics, far more than Abcb1a/b. Both intestinal and hepatic CYP3A activity contributed importantly to low oral bioavailability of lopinavir. Ritonavir increased lopinavir bioavailability primarily by inhibiting CYP3A. Effects of Abcb1a/b were only detectable in the presence of CYP3A, suggesting saturation of Abcb1a/b in the absence of CYP3A activity.
authors.affiliation: Division of Molecular Biology, The Netherlands Cancer Institute, Amsterdam, the Netherlands.
authors.forename: R A B
authors.initials: RA
authors.lastname: van Waterschoot
authors.forename: R
authors.initials: R
authors.lastname: ter Heine
authors.forename: E
authors.initials: E
authors.lastname: Wagenaar
authors.forename: C M M
authors.initials: CM
authors.lastname: van der Kruijssen
authors.forename: R W
authors.initials: RW
authors.lastname: Rooswinkel
authors.forename: A D R
authors.initials: AD
authors.lastname: Huitema
authors.forename: J H
authors.initials: JH
authors.lastname: Beijnen
authors.forename: A H
authors.initials: AH
authors.lastname: Schinkel
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D001682:Biological Availability; D051544:Cytochrome P-450 CYP3A / Q000187:drug effects* / Q000235:genetics; D004285:Dogs; D004347:Drug Interactions; D017320:HIV Protease Inhibitors / Q000493:pharmacokinetics*; D006801:Humans; D007413:Intestinal Mucosa / Q000378:metabolism; D007422:Intestines / Q000201:enzymology; D008099:Liver / Q000201:enzymology / Q000378:metabolism; D061466:Lopinavir; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D008822:Mice, Transgenic; D000089762:Multidrug Resistance-Associated Protein 2; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000235:genetics / Q000378:metabolism*; D011744:Pyrimidinones / Q000493:pharmacokinetics*; D019438:Ritonavir / Q000494:pharmacology
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D051544:Cytochrome P-450 CYP3A; D017320:HIV Protease Inhibitors; D061466:Lopinavir; D000089762:Multidrug Resistance-Associated Protein 2; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D011744:Pyrimidinones; D019438:Ritonavir; C000715087:ABCC2 protein, human; C510163:CYP3A4 protein, human