Genetic polymorphisms of CYP3A5 genes and concentration of the cyclosporine and tacrolimus

Objective. CYP3A is the major enzyme responsible for metabolism of the calcineurin inhibitors cyclosporine (CsA) and tacrolimus. Our objective was to determine the relationship between genetic polymorphisms of CYP3A5 with respect to interindividual variability in CsA and tacrolimus pharmacokinetics. Methods. Kidney transplant recipients receiving CsA (n = 137) or tacrolimus (n = 30) were genotyped for CYP3A5*3 and *6 by a PCR/RFLP method. The patients were grouped according to the CYP3A5 genotype. Dose-adjusted trough levels were correlated with the corresponding genotype. Results. At 3, 6, and 12 months, the tacrolimus dose-adjusted trough levels (dose-adjusted CO) showed a statistically significant difference between the group of CYP3A5 *3/*3 (n = 19) and the group of CYP3A5*1 allele carriers. The former was higher than the latter. The CsA dose-adjusted CO and the actual CO did not display a significant relation (P < .05) between the group of CYP3A5*3/*3 and the group of CYP3A5*1 allele carriers. Conclusion. Patients with the CYP3A5*3/*3 genotype require less tacrolimus to reach target concentrations compared to those with the CYP3A5*1 allele.