The Cytochrome P450 3A5 Non-Expressor Kidney Allograft as a Risk Factor for Calcineurin Inhibitor Nephrotoxicity.

BACKGROUND: Tacrolimus is mainly metabolized by cytochrome P450 3A5 (CYP3A5), which is expressed in the liver. However, CYP3A5 is also expressed in the kidney tissue and may contribute to local tacrolimus clearance in the kidney allograft. We aimed to evaluate the association between the allograft CYP3A5 genotype and transplant outcomes.

METHODS: We conducted a retrospective cohort study at the King Chulalongkorn Memorial Hospital, Thailand, comparing 2 groups of donor and recipient CYP3A5 genotypes, the expressor (*1/*1 and *1/*3) and the non-expressor (*3/*3). The primary outcomes were allograft complications including calcineurin inhibitor (CNI) nephrotoxicity and acute rejection episode.

RESULTS: Of the 50 enrolled patients, 21 donors were expressors and 29 donors were the non-expressors. Tacrolimus trough concentrations were similar between the 2 genotypes. The incidence of CNI nephrotoxicity was higher in recipients with non-expressor donor genotype compared with the expressor donor genotype (72.4 vs. 33.3%, p = 0.006). CNI nephrotoxicity incidence was not different when recipient's genotypes were compared. Multivariate analysis from Cox-regression showed a hazard ratio of 3.18 (p = 0.026) for CNI nephrotoxicity in the non-expressor compared with the expressor donor. The recipient CYP3A5 genotypes did not significantly contribute to CNI nephrotoxicity. Kaplan-Meier analysis demonstrated the lowest CNI nephrotoxicity-free survival in recipients with the expressor genotype who received allograft from the non-expressor donors (p = 0.005).

CONCLUSION: In conclusion, our results suggest that donor CYP3A5 non-expressor genotype (*3/*3) is a risk for CNI nephrotoxicity.