title: The effect of CYP3A5 and ABCB1 single nucleotide polymorphisms on tacrolimus dose requirements in Caucasian liver transplant patients.
abstract: BACKGROUND
  Tacrolimus is a substrate of cytochrome P-450 (CYP) 3A enzyme and of the drug transporter ABCB1. We have investigated the effects of possible relevant CYP3A5 and ABCB1 single nucleotide polymorphisms (SNPs) present in both donors and recipients on tacrolimus blood levels achieved in a population of 32 Caucasian liver transplant patients.
  
  
  METHODS
  At 1, 3 and 6 months after transplantation, tacrolimus doses (mg/kg/day) and trough blood levels (C(0)) were determined. Polymerase chain reaction followed by restriction fragment length polymorphism analysis was used for genotyping CYP3A5*3 [6986A>G] as well as ABCB1 at exons 21 [2677G>T] and 26 [3435C>T].
  
  
  RESULTS
  87.5% of the population showed a CYP3A5*3/*3 genotype. For the ABCB1 SNPs, in the case of 3435C>T the total frequency observed for the allelic variant was 50%. For the 2677G>T, the total frequency of the allelic variant was 12.5%, lower than in other Caucasian populations and without any significant linkage with 3435C>T. At 3 and 6 months after transplantation, tacrolimus dose requirements were significantly higher in patients receiving a liver with one copy of the *1 allele compared to those homozygous for the *3 allele (0.111+/-0.057 vs. 0.057+/-0.030 [P<0.05] at 3 month and 0.086+/-0.051 vs. 0.044+/-0.025 [P<0.05] at 6 month). For the recipients' genotypes, the presence of at least one *1 copy tended, though not statistically significantly, to increase tacrolimus doses. With regard to the ABCB1 SNPs, they did not show any influence on tacrolimus dosing requirements.
  
  
  CONCLUSIONS
  Pharmacogenetic analysis of CYP3A5 in the donor could contribute to determine the appropriate initial dosage of tacrolimus in liver transplant patients.
authors.affiliation: Department of Clinical Pharmacy, ISMETT, Palermo, Italy. aprovenzani@ismett.edu
authors.forename: Alessio
authors.initials: A
authors.lastname: Provenzani
authors.forename: Monica
authors.initials: M
authors.lastname: Notarbartolo
authors.forename: Manuela
authors.initials: M
authors.lastname: Labbozzetta
authors.forename: Paola
authors.initials: P
authors.lastname: Poma
authors.forename: Filippo
authors.initials: F
authors.lastname: Biondi
authors.forename: Rosario
authors.initials: R
authors.lastname: Sanguedolce
authors.forename: Giovanni
authors.initials: G
authors.lastname: Vizzini
authors.forename: Ugo
authors.initials: U
authors.lastname: Palazzo
authors.forename: Piera
authors.initials: P
authors.lastname: Polidori
authors.forename: Fabio
authors.initials: F
authors.lastname: Triolo
authors.forename: Bruno
authors.initials: B
authors.lastname: Gridelli
authors.forename: Natale
authors.initials: N
authors.lastname: D'Alessandro
mesh_terms: D018435:ATP Binding Cassette Transporter, Subfamily B; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000235:genetics*; D051544:Cytochrome P-450 CYP3A / Q000235:genetics*; D005260:Female; D005838:Genotype; D006720:Homozygote; D006801:Humans; D007166:Immunosuppressive Agents / Q000008:administration & dosage* / Q000097:blood; D016031:Liver Transplantation / Q000276:immunology*; D008297:Male; D010597:Pharmacogenetics; D020641:Polymorphism, Single Nucleotide; D016559:Tacrolimus / Q000008:administration & dosage* / Q000097:blood; D044465:White People / Q000235:genetics
chemical_list: C513055:ABCB1 protein, human; D018435:ATP Binding Cassette Transporter, Subfamily B; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D007166:Immunosuppressive Agents; C510164:CYP3A5 protein, human; D051544:Cytochrome P-450 CYP3A; D016559:Tacrolimus