MDR1 C3435T polymorphisms correlate with cyclosporine levels in de novo renal recipients

Background. Single nucleotide polymorphisms (SNPs) in the multidrug resistance (MDRI) gene correlate with the intestinal function of P-glycoprotein (PGP). PGP serves as a hydrophobic export pump that extrudes cyclosporine (CsA) across the luminal membrane thus preventing CsA absorption. These genetic variants may predict CsA exposure levels in the early posttransplantation period. Methods. CsA absorption profiles were established in 75 renal transplant patients using total daily dose and body weight adjusted 4-hour area under the time-concentration curve, AUC((0-4))/Mg dose/kg body weight, on posttransplant day 3. These patients were subsequently genotyped for C3435T and G2677T polymorphisms using real-time polymerase chain reaction. An analysis was conducted to assess the independent impact of C3435T and G2677T SNPs on CsA bioavailability. Results. C3435T polymorphisms were found to be an independent predictor of CsA AUC((0-4))/mg dose/kg levels on postoperative day 3. An inverse correlation was found between the number of T alleles and AUC values such that every T allele was associated with an approximate 15% decrement in AUC((0-4))/mg dose/kg (P =.034). A similar nonsignificant trend was observed for G2677T polymorphisms. Conclusions. MDR1 SNPs are correlated with CsA exposure in the early post-transplant period. Polymorphisms, in conjunction with other criteria, may become a useful tool to optimize initial drug dosing in renal transplantation.