Effect of CYP3A4, CYP3A5, MDR1 and POR Genetic Polymorphisms in Immunosuppressive Treatment in Chilean Kidney Transplanted Patients

Pharmacogenomic implications of the differential distribution of CYP3A5 metabolic phenotypes among Latin American populations

This study shows that the distribution of CYP3A5 alleles (*1, *3, *6 and *7) and genotype-predicted CYP3A5 phenotypes vary significantly across Latin American cohorts (Brazilians and the One Thousand Genomes Admixed American superpopulation), as well as among subcohorts comprising individuals with the highest proportions of Native, European or sub-Saharan African ancestry. Differences in biogeographical ancestry across the study groups are the likely explanation for these results. The differential distribution of CYP3A5 phenotypes has major pharmacogenomic implications, affecting the proportion of individuals carrying high risk CYP3A5 phenotypes for the immunosuppressant tacrolimus and the number of patients that would need to be genotyped to prevent acute rejection in kidney transplant recipients under tacrolimus treatment.

Effect of CYP3A4*22, CYP3A5*3 and POR*28 genetic polymorphisms on calcineurin inhibitors dose requirements in early phase renal transplant patients

OBJECTIVE

This study aimed to investigate the combined effect of CYP3A5*3, CYP3A4*22, and POR*28 genetic polymorphisms on tacrolimus and cyclosporine dose requirements.

METHODS

One hundred thirty renal transplant patients placed on either tacrolimus or cyclosporine were recruited, where the effect of CYP3A5*3, CYP3A4*22, and POR*28 genetic polymorphisms on their dose requirements were studied at days 14, 30, and 90 post-transplantations.

RESULTS

The POR*28 allele frequency in the studied population was 29.61%. The tacrolimus dose-adjusted trough concentration ratio (C0/D) was significantly lower in the fast metabolizers group ( CYP3A5*1/POR*28(CT/TT ) carriers) than in the poor metabolizers group ( CYP3A5*3/*3/CYP3A4*22 carriers) throughout the study (14, 30, and 90 days) ( P = 0.001, <0.001, and 0.003, respectively). Meanwhile, there was no significant effect of this gene combination on cyclosporine C0/D.

CONCLUSION

Combining the CYP3A5*3, POR*28 , and CYP3A4*22 genotypes can have a significant effect on early tacrolimus dose requirements determination and adjustments. However, it does not have such influence on cyclosporine dose requirements.

The effect of genetic variants in the transcription factor TSPYL family on the CYP3A4 mediated cyclosporine metabolism in kidney transplant patients

CYP3A4 activity shows considerable interindividual variability. Although studies indicate 60%-80% is heritable, common single nucleotide variants (SNVs) in CYP3A4 together only explain ~10%. Transcriptional factors, such as the testis-specific Y-encoded-like proteins (TSPYLs) family, have been reported to regulate the expression of CYP enzymes including CYP3A4 in vitro. Here, we investigated the effect of genetic variants in TSPYL on CYP3A4 activity using data from a clinical study and a human liver bank. Five SNVs (rs3828743, rs10223646, rs6909133, rs1204807, and rs1204811) in TSPYL were selected because of a reported effect on CYP3A4 expression in vitro or suggested clinical effect. For the clinical study, whole blood concentrations, clinical data, and DNA were available from 295 kidney transplant recipients participating in the prospective MECANO study. A multivariate pharmacokinetic model adjusted for body weight, steroid treatment, and CYP3A4 genotype was used to assess the effect of the genetic variants on cyclosporine clearance. In multivariate analysis, homozygous carriers of rs3828743 had a 18% lower cyclosporin clearance compared to the wild-type and heterozygous patients (28.72 vs. 35.03 L/h, p = 0.018) indicating a lower CYP3A4 activity and an opposite direction of effect compared to the previously reported increased CYP3A4 expression. To validate, we tested associations between rs3828743 and CYP3A4 mRNA and protein expression as well as enzyme activity with data from a liver bank (n = 150). No association with any of these end points was observed. In conclusion, the totality of evidence is not in support of a significant role for TSPYL SNV rs3828743 in explaining variability in CYP3A4 activity.

Evaluation of limited-sampling strategies to calculate AUC(0–24) and the role of CYP3A5 in Chilean pediatric kidney recipients using extended-release tacrolimus

Background: Kidney transplantation (KTx) requires immunosuppressive drugs such as Tacrolimus (TAC) which is mainly metabolized by CYP3A5. TAC is routinely monitored by trough levels (C0) although it has not shown to be a reliable marker. The area-under-curve (AUC) is a more realistic measure of drug exposure, but sampling is challenging in pediatric patients. Limited-sampling strategies (LSS) have been developed to estimate AUC. Herein, we aimed to determine AUC(0–24) and CYP3A5 genotype in Chilean pediatric kidney recipients using extended-release TAC, to evaluate different LSS-AUC(0–24) formulas and dose requirements.

Patients and methods: We analyzed pediatric kidney recipients using different extended-release TAC brands to determine their trapezoidal AUC(0–24) and CYP3A5 genotypes (SNP rs776746). Daily TAC dose (TAC-D mg/kg) and AUC(0–24) normalized by dose were compared between CYP3A5 expressors (*1/*1 and *1/*3) and non-expressors (*3/*3). We evaluated the single and combined time-points to identify the best LSS-AUC(0–24) model. We compared the performance of this model with two pediatric LSS-AUC(0–24) equations for clinical validation.

Results: Fifty-one pharmacokinetic profiles were obtained from kidney recipients (age 13.1 ± 2.9 years). When normalizing AUC(0–24) by TAC-D significant differences were found between CYP3A5 expressors and non-expressors (1701.9 vs. 2718.1 ng*h/mL/mg/kg, p &lt; 0.05). C0 had a poor fit with AUC(0–24) (r2 = 0.5011). The model which included C0, C1 and C4, showed the best performance to predict LSS-AUC(0–24) (r2 = 0.8765) and yielded the lowest precision error (7.1% ± 6.4%) with the lowest fraction (9.8%) of deviated AUC(0–24), in comparison to other LSS equations.

Conclusion: Estimation of LSS-AUC(0–24) with 3 time-points is an advisable and clinically useful option for pediatric kidney recipients using extended-release TAC to provide better guidance of decisions if toxicity or drug inefficacy is suspected. The different CYP3A5 genotypes associated with variable dose requirements reinforce considering genotyping before KTx. Further multi-centric studies with admixed cohorts are needed to determine the short- and long-term clinical benefits.

Functional evaluation of cyclosporine metabolism by CYP3A4 variants and potential drug interactions

The aim of this study is to investigate the effects of CYP3A4 genetic polymorphisms on the metabolism of cyclosporine (CsA) in vitro and identify drugs that interact with CsA. An enzymatic incubation system was developed to evaluate the kinetic parameters of CYP3A4 on CsA catalysis. A total of 132 drugs were screened to identify potential drug-drug interactions. Sprague-Dawley rats were used to determine the interaction between CsA and nimodipine and nisoldipine. The metabolite AM1 was measured by ultra-performance liquid chromatography-tandem mass spectrometry. The results demonstrate that 16 CYP3A4 variants (CYP3A4.7, 8, 9, 12, 13, 14, 16, 18, 19, 23, 24, 28, 31, 32, 33, and 34) have a lower metabolic capacity for CsA, ranging from 7.19% to 72.10%, than CYP3A4.1. In contrast, the relative clearance rate of CYP3A4.5 is significantly higher than that of CYP3A4.1. Moreover, CYP3A4.20 loses its catalytic ability, and five other variants have no significant difference. A total of 12 drugs, especially calcium channel blockers, were found to remarkably inhibit the metabolism of CsA with an inhibitory rate of over 80%. Nimodipine inhibits the activity of CsA in rat liver microsomes with an IC₅₀ of 20.54 ± 0.93 μM, while nisoldipine has an IC₅₀ of 16.16 ± 0.78 μM. In in vivo, three groups of Sprague-Dawley rats were administered CsA with or without nimodipine or nisoldipine; the AUC_(0-t) and AUC_(0-∞) of CsA were significantly increased in the nimodipine group but not obviously in the nisoldipine group. Mechanistically, the inhibition mode of nimodipine on cyclosporine metabolism is a mixed inhibition. Our data show that gene polymorphisms of CYP3A4 and nimodipine remarkably affect the metabolism of CsA, thus providing a reference for the precise administration of CsA.

The Effect of Voriconazole on Tacrolimus in Kidney Transplantation Recipients: A Real-World Study

Tacrolimus is an immunosuppressant with a narrow therapeutic window. Tacrolimus exposure increased significantly during voriconazole co-therapy. The magnitude of this interaction is highly variable, but it is hard to predict quantitatively. We conducted a study on 91 kidney transplantation recipients with voriconazole co-therapy. Furthermore, 1701 tacrolimus concentration data were collected. Standard concentration adjusted by tacrolimus daily dose (C/D) and weight-adjusted standard concentration (CDW) increased to 6 times higher during voriconazole co-therapy. C/D and CDW increased with voriconazole concentration. Patients with the genotype of CYP3A5 *3/*3 and CYP2C19 *2/*2 or *2/*3 were more variable at the same voriconazole concentration level. The final prediction model could explain 54.27% of the variation in C/D and 51.11% of the variation in CDW. In conclusion, voriconazole was the main factor causing C/D and CDW variation, and the effect intensity should be quantitative by its concentration. Kidney transplant recipients with CYP3A5 genotype of *3/*3 and CYP2C19 genotype of *2/*2 and *2/*3 should be given more attention during voriconazole co-therapy. The prediction model established in this study may help to reduce the occurrence of rejection.

Effect of hepar-protecting Wuzhi capsule on Pharmacokinetics and Dose-effect Character of Tacrolimus in Healthy Volunteers

Wuzhi capsule (WZC), a preparation of Fructus Schisandra sphenanthera extract, has been widely used for the treatment of viral and drug-induced hepatitis in China. This study aimed to determine the pharmacokinetic parameters of tacrolimus (TAC) when co-administered with WZC and its dose-effect of WZC on TAC in healthy volunteers. We assessed the effect of increased dosage of WZC (1, 2, 6, and 8 capsules once daily) on the relative oral exposure of TAC to explore the dose-response relationship between WZC and TAC using bioanalysis, pharmacokinetic, genotypical analyses. We elucidate the influence of CYP3A5 and MDR1 genetic polymorphisms on the WZC dose by maintaining C_trough of TAC in Chinese healthy volunteers. When co-administered with WZC, the T_max of TAC was increased significantly while the apparent oral clearance was decreased. The plasma TAC level in volunteers with high CYP3A5 expression was greatly lower than that in those with mutant CYP3A5. However, polymorphisms of MDR1 exon26 C3435T, exon21 G2677T/A and exon12 C1236T were not associated with plasma TAC levels. Our findings provide important information on interactions between modern medications and herbal products, thus facilitating a better usage of TAC in patients receiving WZC. This article is protected by copyright. All rights reserved.