Influence of ABCB1 polymorphisms and haplotypes on tacrolimus nephrotoxicity and dosage requirements in children with liver transplant

AIMS<br/>The aim of this study was to investigate the in?uence of genetic polymorphisms in ABCB1 on the incidence of nephrotoxicity and tacrolimus dosage-requirements in paediatric patients following liver transplantation.<br/>METHODS<br/>Fifty-one paediatric liver transplant recipients receiving tacrolimus were genotyped for ABCB1 C1236>T, G2677>T and C3435>T polymorphisms. Dose-adjusted tacrolimus trough concentrations and estimated glomerular ?ltration rates (EGFR) indicative of renal toxicity were determined and correlated with the corresponding genotypes.<br/>RESULTS<br/>The present study revealed a higher incidence of the ABCB1 variant-alleles examined among patients with renal dysfunction (30% reduction in EGFR) at 6 months post-transplantation (1236T allele: 63.3% vs 37.5% in controls,P = 0.019; 2677T allele: 63.3% vs. 35.9%, p = 0.012; 3435T allele: 60% vs. 39.1%,P = 0.057). Carriers of the G2677->T variant allele also had a signi?cant reduction (%) in EGFR at 12 months post-transplant (mean difference = 22.6%; P = 0.031). Haplotype analysis showed a signi?cant association between T-T-T haplotypes and an increased incidence of nephrotoxicity at 6 months post-transplantation (haplotype-frequency = 52.9% in nephrotoxic patients vs 29.4% in controls; P = 0.029). Furthermore, G2677->T and C3435->T polymorphisms and T-T-T haplotypes were signi?cantly correlated with higher tacrolimus dose-adjusted pre-dose concentrations at various time points examined long after drug initiation.<br/>CONCLUSIONS<br/>These ?ndings suggest that ABCB1 polymorphisms in the native intestine signi?cantly in?uence tacrolimus dosage-requirement in the stable phase after transplantation. In addition, ABCB1 polymorphisms in paediatric liver transplant recipients may predispose them to nephrotoxicity over the ?rst year posttransplantation. Genotyping future transplant recipients for ABCB1 polymorphisms, therefore, could have the potential to individualize better tacrolimus immunosuppressive therapy and enhance drug safety