Association Study On Mdr1 And Cyp3a4/5 Genetic Polymorphism And Cyp3a Phenotype With The Pharmacokinetics Of Tacrolimus In Healthy Chinese Volunteers

Purpose This study investigated the effects of MDR1, CYP3A4*18B and CYP3A5*3 genetic polymorphisms on tacrolimus pharmacokinetics and the usefulness of phenotyping CYP3A by midazolam to predict tacrolimus clearance in healthy Chinese.Methods Pharmacokinetic data were obtained from one comparative bioavailability studies of oral tacrolimus formulations (n=22). Blood samples were collected pre-dose and 16 times during post-dose 72-h to obtain a full pharmacokinetic profile after each subject consumed a 5 mg tacrolimus. After a consecutive 20-day observation period, plasma samples were harvested at postdose 4-h after oral administration of 7.5mg midazolam. MDR1 C1236T, G2677T/A, C3435T, CYP3A4*18B, and CYP3A5*3 genotypes were determined by direct sequencing method. The concentration of tacrolimus, midazolam and its hydroxylation metabolite were measured by LC-MS/MS. Non-compartmental pharmacokinetic analysis with one-way analysis of variance (ANOVA) and non-linear mixed-effects modeling (NONMEM) were performed in the analysis. The relationship between tacrolimus clearance and the plasma concentration of midazolam and 1'- hydroxymidazolam, and the 1'- hydroxymidazolam/midazolam plasma concentration ratio was examined by Spearman method.Results1. For CYP3A4*18B SNP, significant differences were observed in Cmax (P=0.004), AUClast (P=0.005) and AUCinf (P=0.005) between the subjects with the CYP3A4*1/*1 genotype (n=15) and those with CYP3A4*1/*18B genotype (n=6) or CYP3A4*18B/*18B genotype(n=1),respectively;TAC geometric mean Cmax and AUCinf for the wild-type subjects with CYP3A4*1/*1 genotype(n=15)was 1.8-fold and 1.9-fold higher respectively,compared with the value seen in those subjects with CYP3A4*18B allele(n=7).2.For CYP3A5*3 SNP,significant differences were observed only in AUCinf(P=0.001), not in Cmax (P=0.062)between the subjects with the CYP3A5*3/*3 genotype(n=13) and those with CYP3A5*1/*3 genotype(n=9),respectively;TAC geometric mean AUCinf for the homozygous-mutation subjects with CYP3A5*3/*3 genotype(n=13)was 2.0-fold higher compared with the value seen in those subjects with CYP3A5*1/*3 genotype(n=9).3.The combined genotypes of CYP3A4*18B and CYP3A5*3 had a greater impact than CYP3A4*18B or CYP3A5*3 alone,and they were estimated to account for 28.4% of the inter-subject variability of apparent clearance by NONMEM,in agreement with the results by the non-population approach.Significant differences were observed in Cmax (P=0.030) and AUCinf (P<0.001) between the subjects with CYP3A4*1/*1-CYP3A5*3/*3 (n=11) and those not carrying CYP3A4*1/1*-CYP3A5/3/*3(n=11);TAC geometric mean Cmax and AUCinf for the subjects with CYP3A4*1/*1-CYP3A5*3/*3 genotypes(n=11)was 1.6-fold and 2.1-fold respectively, compared with the value seen in those not carrying CYP3A4*1/*1-CYP3A5*3/*3(n=11).4.MDR1 SNPs,genotypes and haplotypes were not associated with tacrolimus pharmacokinetics.The midazolam test showed that midazolam may not be a useful probe in the prediction of tacrolimus pharmacokinetics in vivo.Conclusions This study demonstrated that both CYP3A4*18B and CYP3A5*3 polymorphisms affected the pharmacokinetics of tacrolimus and that subjects with a combined genotype of CYP3A4*1/*1-CYP3A5*3/*3 may require lower tacrolimus doses to achieve target concentration levels.This study also found no significant effect of MDR1 genotypes/haplotypes/linked-genotypes derived from C1236T, G2677A/T and C3435T on tacrolimus pharmacokinetics, and that phenotyping CYP3A by using midazolam as a probe may not be useful in the prediction of tacrolimus dosage requirements.