title: Cyp3A4, Cyp3A5, and MDR-1 genetic influences on tacrolimus pharmacokinetics in renal transplant recipients.
abstract: OBJECTIVE
  The immunosuppressive drug tacrolimus requires strict therapeutic monitoring due to its narrow therapeutic index and great inter-individual variability. Cytochrome P450 3A4 (Cyp3A4) and Cyp3A5 are the most important contributors to tacrolimus metabolism while the P-glycoprotein pump (MDR-1) modulates its bioavailability. The objective was to investigate the association between Cyp3A4, Cyp3A5, and MDR-1 polymorphisms and tacrolimus pharmacokinetics in the early period after renal transplantation.
  
  
  METHODS
  Forty-four renal transplant recipients were genotyped for 8 Cyp3A4, 7 Cyp3A5, and 5 MDR-1 genetic variants affecting the proteins' expression and/or function. Dose-adjusted tacrolimus though levels were determined during the first week after transplantation and correlated with corresponding genotype.
  
  
  RESULTS
  We found no correlation between Cyp3A4 polymorphism and tacrolimus pharmacokinetics. Patients who do not carry both Cyp3A5*3 alleles achieved lower mean dose-adjusted tacrolimus blood concentrations (p<0.001) and needed a longer time to reach the target concentration (10-12 ng/ml; p<0.001) compared to Cyp3A5*3 homozygotes. Patients with less than three copies of MDR-1 (T-129C, C3435T and G2677T) polymorphisms, associated with reduced expression of P-glycoprotein, had also lower dose-adjusted tacrolimus blood concentrations compared to patients having equal to or greater than three copies of MDR-1 genetic variants (P=0.003). There was no difference in the rate of biopsy-confirmed acute rejection among groups during the first 3 months after transplantation.
  
  
  CONCLUSIONS
  The complete absence of Cyp3A5*3 allele and the accumulation of less than three copies of MDR-1 (T-129C, C3435T and G2677T) polymorphisms are associated with lower tacrolimus blood levels identifying these genotypes as markers for patients requiring higher tacrolimus doses.
authors.affiliation: Laboratoire d'immunogénétique, Centre hospitalier de l'Université de Montréal (CHUM)-Hôpital Notre-Dame, Montreal, Quebec, Canada.
authors.forename: Jean Nicholas
authors.initials: JN
authors.lastname: Roy
authors.forename: Azemi
authors.initials: A
authors.lastname: Barama
authors.forename: Charles
authors.initials: C
authors.lastname: Poirier
authors.forename: Bernard
authors.initials: B
authors.lastname: Vinet
authors.forename: Michel
authors.initials: M
authors.lastname: Roger
mesh_terms: D000328:Adult; D001682:Biological Availability; D051544:Cytochrome P-450 CYP3A; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics*; D004305:Dose-Response Relationship, Drug; D004334:Drug Administration Schedule; D005260:Female; D005787:Gene Frequency; D019450:Genes, MDR / Q000235:genetics*; D008040:Genetic Linkage; D005838:Genotype; D006801:Humans; D016867:Immunocompromised Host / Q000235:genetics*; D007166:Immunosuppressive Agents / Q000097:blood / Q000493:pharmacokinetics; D016030:Kidney Transplantation / Q000276:immunology; D008297:Male; D008875:Middle Aged; D021141:Nucleic Acid Amplification Techniques; D012150:Polymorphism, Restriction Fragment Length; D016559:Tacrolimus / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics*; D014180:Transplantation / Q000502:physiology
chemical_list: D007166:Immunosuppressive Agents; D003577:Cytochrome P-450 Enzyme System; C510164:CYP3A5 protein, human; D051544:Cytochrome P-450 CYP3A; C510163:CYP3A4 protein, human; D016559:Tacrolimus