title: Multidrug resistance protein 2 genetic polymorphisms influence mycophenolic acid exposure in renal allograft recipients.
abstract: BACKGROUND
  Mycophenolic acid (MPA) is glucuronidated by uridine diphosphate-glucuronosyltransferases (UGTs) to its pharmacologically inactive 7-O-glucuronide metabolite (MPAG). MPAG is excreted into the bile via the multidrug resistance-associated protein 2 (MRP2/ABCC2), which is essential for enterohepatic (re)circulation (EHC) of MPA(G).
  
  
  METHODS
  The objective of this study was to determine the relationship between single nucleotide polymorphisms (SNPs) in the MRP2 (G-1549A, G-1023A, A-1019G, C-24, G1249A, C3972T and G4544A) and UGT1A9 (C-2152T, T-275AandT98C) genes and MPA pharmacokinetics in 95 renal allograft recipients at days 7, 42, 90, and 360 after transplantation. In addition to mycophenolate mofetil, all patients received tacrolimus and corticosteroids as immunosuppression.
  
  
  RESULTS
  At day seven after transplantation, in the absence of the MRP2 C-24T SNP, mild liver dysfunction was associated with significantly lower MPA dose-interval exposure and higher MPA oral clearance, while liver dysfunction did not affect MPA pharmacokinetics in patients with the MRP2 C-24T variant. A similar effect is noted for the C-3972T variant, which is in linkage disequilibrium with C-24T. At later time points after transplantation the MRP2 C-24T SNP was associated with significantly higher dose-corrected MPA trough levels. Patients with the MRP2 C-24T variant had significantly more diarrhea in the first year after transplantation.
  
  
  CONCLUSIONS
  The MRP2 C-24T and C-3972T polymorphisms protect renal transplant recipients from a decrease in MPA exposure associated with mild liver dysfunction. Furthermore, this study suggests that the C-24T SNP is associated with a lower oral clearance of MPA in steady-state conditions.
authors.affiliation: Department of Nephrology and Renal Transplantation, University Hospitals Leuven, Leuven, Belgium.
authors.forename: Maarten
authors.initials: M
authors.lastname: Naesens
authors.forename: Dirk R J
authors.initials: DR
authors.lastname: Kuypers
authors.forename: Kristin
authors.initials: K
authors.lastname: Verbeke
authors.forename: Yves
authors.initials: Y
authors.lastname: Vanrenterghem
mesh_terms: D000305:Adrenal Cortex Hormones / Q000494:pharmacology; D015331:Cohort Studies; D005260:Female; D006801:Humans; D007166:Immunosuppressive Agents / Q000494:pharmacology; D007674:Kidney Diseases / Q000235:genetics* / Q000628:therapy*; D016030:Kidney Transplantation / Q000379:methods*; D015810:Linkage Disequilibrium; D008297:Male; D026901:Membrane Transport Proteins / Q000235:genetics*; D000089762:Multidrug Resistance-Associated Protein 2; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000235:genetics*; D009173:Mycophenolic Acid / Q000031:analogs & derivatives / Q000493:pharmacokinetics* / Q000494:pharmacology; D020641:Polymorphism, Single Nucleotide; D016559:Tacrolimus / Q000494:pharmacology; D013997:Time Factors
chemical_list: D000305:Adrenal Cortex Hormones; D007166:Immunosuppressive Agents; D026901:Membrane Transport Proteins; D000089762:Multidrug Resistance-Associated Protein 2; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D009173:Mycophenolic Acid; D016559:Tacrolimus; C000715087:ABCC2 protein, human