Impact of CYP3A5 polymorphism on trough concentrations and outcomes of tacrolimus minimization during the early period after kidney transplantation.

Purpose: The purpose of this study is to determine the impacts of CYP3A5 polymorphism on tacrolimus concentration and the proportion of patients within a target therapeutic range during the first week after transplantation together with the 3-month acute rejection rate in kidney transplant patients receiving a minimized tacrolimus regimen.
Methods: A total of 164 patients participated in the study. All received oral tacrolimus twice daily starting on the day of surgery with the target pre-dose (trough) concentration of 4-8 ng/ml for prevention of allograft rejection. Cytochrome P450 (CYP) 3A5 genotypes were determined. The patients were divided into CYP3A5 expressers (CYP3A5*1 allele carriers) and CYP3A5 nonexpressers (homozygous CYP3A5*3). Whole blood tacrolimus concentrations on days 3 and 7 posttransplantation and the incidence of biopsy-proven acute rejection (BPAR) at 3-month posttransplantation were compared between groups.
Results: On day 3, the median (IQR) dose-and-weight-normalized trough concentration in expressers and nonexpressers were 54.61 (31.98, 78.87) and 91.80 (57.60, 130.20) ng/ml per mg/kg/day, respectively (p < 0.001). Although only 47 and 42% of expressers and nonexpressers were within the target range on day 3, approximately 60% of both groups were within the target range on day 7. Proportions of BPAR among expressers and nonexpressers were 6.0 and 7.4 %, respectively (p = 0.723). The median (IQR) times to the first rejection in CYP3A5 expressers and nonexpressers were 32 (12, 68) and 15 (12, 37) days, respectively (p = 0.410).
Conclusions: Although CYP3A5 polymorphism significantly influenced the tacrolimus dose required to achieve the target concentration, the impact of CYP3A5 polymorphism on BPAR was not observed in this study.