Influence of CYP3A5 genetic polymorphism on cyclosporine A metabolism and elimination in Chinese renal transplant recipients

Aim: To investigate whether the CYP3A5*3 polymorphism would affect cyclosporine A (CsA) metabolism in Chinese renal transplant patients. Methods: The CYP3A5*3 genotype was determined in Chinese renal transplant recipients using polymerase chain reaction and amplification of specific alleles (PCR-ASA). The concentrations of CsA and metabolites were separately measured by fluorescence polarization immunoassay and dose-adjusted trough concentrations and metabolic ratio (MR) values were calculated. Results: The trough concentrations adjusted with the dose was significantly higher in the wild allele carriers compared to both the homozygous (*3*3) and heterozygous variants (*1 *3). However, no significant difference was found for the dose-adjusted metabolite concentrations. The MR values for the 3 genotype groups were as follows: 0.92±0.62 for CYP3A5*3/*3 (n=14), 0.99±0.51 for CYP3A5*1/*3 (n=15), and 1.45±0.62 for CYP3A5*1/*1 (n=9), respectively. Post hoc comparisons showed that only the MR values between the CYP3A5*3/*3 group and the CYP3A5*1/*1 group were significantly different. Conclusion: The CYP3A5*3 polymorphism exerted little effect on cyclosporine metabolism. The MR may be a more accurate indicator for therapeutic drug monitoring, considering its integrated information on body exposure of both parent drugs and metabolites.