Association between tacrolimus concentration and genetic polymorphisms of CYP3A5 and ABCB1 during the early stage after liver transplant in an Iranian population.

Abstract Tacrolimus is widely used as an immunosuppressive drug in liver transplant recipients with a narrow therapeutic range and variable individualized pharmacokinetics. Tacrolimus is a substrate of cytochrome P-450 3A enzyme and the drug transporter, P-glycoprotein. We determined the genotypic frequencies of cytochrome P-4503A5 (rs776746), and ABCB1 (rs1045642), single nucleotide polymorphisms in a population of 100 Iranian liver transplant patients, and investigated the influence of the above-mentioned single nucleotide polymorphisms on tacrolimus concentrations. At 7 and 30 days after transplant, tacrolimus dosages (mg/kg/d), trough blood levels (T0), and dose-adjusted concentrations (concentration/dosage ratio) were determined. Polymerase chain reaction, followed by restriction fragment length polymorphism analysis, was used for genotyping cytochrome P-4503A5*3 [6986A>G] as well as ABCB1 [3435C>T]. Ninety-five percent of the population showed a cytochrome P-4503A5*3/*3 genotype. ABCB13435TT genotype was observed in 33 cases (33%); whereas 51 cases (51%) carried 3435CT, and 16 cases (16%) carried 3435CC. With regard to the ABCB1 and cytochrome P-4503A5, they showed no influence on tacrolimus dosing requirements at 1 week or 1 month after transplant. No association of any genetic variant with the acute rejection rate was found. Finally, as the liver donor genotype influences tacrolimus pharmacokinetics with regard to expression of cytochrome P-4503A5, far more than the genotype of the recipient; therefore, it should be considered before recommending any personal immunosuppressive treatment based on pharmacogenetics.