title: Genetic polymorphisms of the CYP3A4, CYP3A5, and MDR-1 genes and pharmacokinetics of the calcineurin inhibitors cyclosporine and tacrolimus.
abstract: BACKGROUND
  The calcineurin inhibitors cyclosporine (INN, cyclosporin) and tacrolimus have a narrow therapeutic index and show considerable interindividual variability in their pharmacokinetics. The low oral bioavailability of calcineurin inhibitors is thought to result from the actions of the metabolizing enzymes cytochrome P450 (CYP) 3A4 and CYP3A5 and the multidrug efflux pump P-glycoprotein, encoded by MDR-1.
  
  
  OBJECTIVE
  Our objective was to determine the role of genetic polymorphisms in CYP3A4, CYP3A5, and MDR-1 with respect to interindividual variability in cyclosporine and tacrolimus pharmacokinetics.
  
  
  METHODS
  Kidney transplant recipients receiving cyclosporine (n = 110) or tacrolimus (n = 64) were genotyped for CYP3A4*1B and *3, CYP3A5*3 and *6, and MDR-1 C3435T. Dose-adjusted trough levels were determined and correlated with the corresponding genotype.
  
  
  RESULTS
  Tacrolimus dose-adjusted trough levels were higher in CYP3A5*3/*3 patients (n = 45) than in *1/*3 plus *1/*1 patients (n = 17), as follows: median and range, 94 (34-398) ng/mL per mg/kg versus 61 (37-163) ng/mL per mg/kg (P <.0001, Mann-Whitney test). CYP3A4*1B allele carriers (n = 10) had lower tacrolimus dose-adjusted trough levels compared with those in patients with the wild-type (*1/*1) genotype (n = 54): median and range, 57 (40-163) ng/mL per mg/kg versus 89 (34-398) ng/mL per mg/kg) (P =.003, Mann-Whitney test). No evidence was found supporting a role for the MDR-1 C3435T polymorphism in tacrolimus dose requirement. None of the polymorphisms studied correlated with cyclosporine dose-adjusted predose concentrations.
  
  
  CONCLUSIONS
  As a group, patients with the CYP3A5*3/*3 genotype require less tacrolimus to reach target predose concentrations compared with CYP3A5*1 allele carriers, whereas CYP3A4*1B carriers require more tacrolimus to reach target trough concentrations compared with CYP3A4*1 homozygotes.
authors.affiliation: Department of Internal Medicine, Renal Tranplant Unit, Erasmus Medical Center, Rotterdam, The Netherlands. d.a.hesselink@erasmusmc.nl
authors.forename: Dennis A
authors.initials: DA
authors.lastname: Hesselink
authors.forename: Ron H N
authors.initials: RH
authors.lastname: van Schaik
authors.forename: Ilse P
authors.initials: IP
authors.lastname: van der Heiden
authors.forename: Marloes
authors.initials: M
authors.lastname: van der Werf
authors.forename: Peter J H Smak
authors.initials: PJ
authors.lastname: Gregoor
authors.forename: Jan
authors.initials: J
authors.lastname: Lindemans
authors.forename: Willem
authors.initials: W
authors.lastname: Weimar
authors.forename: Teun
authors.initials: T
authors.lastname: van Gelder
mesh_terms: D065095:Calcineurin Inhibitors; D016572:Cyclosporine / Q000008:administration & dosage / Q000493:pharmacokinetics*; D051544:Cytochrome P-450 CYP3A; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics*; D004247:DNA / Q000235:genetics; D004305:Dose-Response Relationship, Drug; D005260:Female; D019450:Genes, MDR / Q000235:genetics*; D006801:Humans; D007166:Immunosuppressive Agents / Q000008:administration & dosage / Q000493:pharmacokinetics*; D016030:Kidney Transplantation / Q000276:immunology; D008297:Male; D011110:Polymorphism, Genetic / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016559:Tacrolimus / Q000008:administration & dosage / Q000493:pharmacokinetics*
chemical_list: D065095:Calcineurin Inhibitors; D007166:Immunosuppressive Agents; D016572:Cyclosporine; D004247:DNA; D003577:Cytochrome P-450 Enzyme System; C104464:CYP3A protein, human; C510164:CYP3A5 protein, human; D051544:Cytochrome P-450 CYP3A; C510163:CYP3A4 protein, human; D016559:Tacrolimus