CYP3A5 polymorphism effect on cyclosporine pharmacokinetics in living donor renal transplant recipients: analysis by population pharmacokinetics

Initial dosage optimisation of cyclosporine in Chinese paediatric patients undergoing allogeneic haematopoietic stem cell transplantation based on population pharmacokinetics: a retrospective study

OBJECTIVE

Improved understanding of cyclosporine A (CsA) pharmacokinetics in children undergoing allogeneic haematopoietic stem cell transplantation (allo-HSCT) is crucial for effective prevention of acute graft-versus-host disease and medication safety. The aim of this study was to establish a population pharmacokinetic (Pop-PK) model that could be used for individualised therapy to paediatric patients undergoing allo-HSCT in China.

DESIGN, SETTING AND PARTICIPANTS

A retrospective analysis of 251 paediatric HSCT patients who received CsA intravenously in the early post transplantation period at Women and Children's Medical Center in Guangzhou was conducted.

ANALYSIS MEASURES

The model building dataset from 176 children was used to develop and analyse the CsA Pop-Pk model by using the nonlinear mixed effect model method. The basic information was collected by the electronic medical record system. Genotype was analysed by matrix-assisted time-of-flight mass spectrometry. The stability and predictability of the final model were verified internally, and a validation dataset of 75 children was used for external validation. Monte Carlo simulation is used to adjust and optimise the initial dose of CsA in paediatric allo-HSCT patients.

RESULTS

The typical values for clearance (CL) and volume of distribution ([Formula: see text]) were 14.47 L/hour and 2033.53 L, respectively. The body weight and haematocrit were identified as significant variables for V, while only body weight had an impact on CL. The simulation based on the final model suggests that paediatrics with HSCT required an appropriate intravenous dose of 5 mg/kg/day to reach the therapeutic trough concentration.

CONCLUSIONS

The CsA Pop-PK model established in this study can quantitatively describe the factors influencing pharmacokinetic parameters and precisely predict the intrinsic exposure to CsA in children. In addition, our dosage simulation results can provide evidence for the personalised medications TRIAL REGISTRATION NUMBER: ChiCTR2000040561.

Significance of Ethnic Factors in Immunosuppressive Therapy Management After Organ Transplantation

Clinical outcomes after organ transplantation have greatly improved in the past 2 decades with the discovery and development of immunosuppressive drugs such as calcineurin inhibitors, antiproliferative agents, and mammalian target of rapamycin inhibitors. However, individualized dosage regimens have not yet been fully established for these drugs except for therapeutic drug monitoring-based dosage modification because of extensive interindividual variations in immunosuppressive drug pharmacokinetics. The variations in immunosuppressive drug pharmacokinetics are attributed to interindividual variations in the functional activity of cytochrome P450 enzymes, UDP-glucuronosyltransferases, and ATP-binding cassette subfamily B member 1 (known as P-glycoprotein or multidrug resistance 1) in the liver and small intestine. Some genetic variations have been found to be involved to at least some degree in pharmacokinetic variations in post-transplant immunosuppressive therapy. It is well known that the frequencies and effect size of minor alleles vary greatly between different races. Thus, ethnic considerations might provide useful information for optimizing individualized immunosuppressive therapy after organ transplantation. Here, we review ethnic factors affecting the pharmacokinetics of immunosuppressive drugs requiring therapeutic drug monitoring, including tacrolimus, cyclosporine, mycophenolate mofetil, sirolimus, and everolimus.

Population Pharmacokinetic Modeling of Cyclosporine Among Malaysian Renal Transplant Patients: An Evaluation of Methods to Handle Missing Doses in Conventional Drug-Monitoring Data

Cyclosporine is a primary drug in transplant immunosuppression regimens. It has a narrow therapeutic index and variable pharmacokinetic behavior. This study aimed to develop a population pharmacokinetic model of cyclosporine in Malaysian renal transplant recipients as well as to evaluate the performances of different methodsfor handling missing doses. A total of 2804 concentrationts predose and 2 hours after doses were collected retrospectively from 113 renal transplant patients on cyclosporine in Penang General Hospital. Model structure and pharmacokinetic parameters were estimated using nonlinear mixed-effects modeling software. Missing doses were handled using different methods to evaluate their performance. Covariate analysis was performed using stepwise forward addition (P < .05) followed by backward elimination (P < .001). Prediction-corrected visual predictive check and sampling-importance resampling methods were used to validate the final model. A 1-compartment model with first-order absorption and elimination best fitted the data. All methods to handle missing doses performed well with the missing dose method being superior to other methods and thus was applied in the final model. Cyclosporine clearance (CL/F) was estimated as 15.1 L/h, and volume of distribution (V/F) was 108 L. Postoperative time, sex, and calcium channel blockers were identified as significant covariates on CL/F, whereas sex and cholesterol level were identified as significant covariates on V/F. This is the first population pharmacokinetic model developed in Malaysian renal transplant patients using a large sample with an evaluation of different methods to handle missing doses in less informative conventional therapeutic drug-monitoring data.

Population pharmacokinetics of cyclosporine in Chinese children receiving hematopoietic stem cell transplantation

Cyclosporine (CsA) is characterized by a narrow therapeutic window and high interindividual pharmacokinetic variability, particularly in juvenile patients. The aims of this study were to build a population pharmacokinetic model of CsA in Chinese children with hematopathy who received allogeneic hematopoietic stem cell transplantation (allo-HSCT) and to identify covariates affecting CsA pharmacokinetics. A total of 86 Chinese children aged 8.4 ± 3.8 years (range 1.1–16.8 years) who received allo-HSCT were enrolled. Whole blood samples were collected before allo-HSCT. Genotyping was performed using an Agena MassARRAY system. A total of 1010 trough plasma concentration values of CsA and clinical data were collected. The population pharmacokinetic model of CsA was constructed using nonlinear mixed-effects modeling (NONMEM) software. The stability and performance of the final model were validated using bootstrapping and normalized prediction distribution errors. We showed that a one-compartment model with first-order elimination adequately described the pharmacokinetics of CsA. The typical values for clearance (CL) and volume of distribution (V) were 42.3 L/h and 3100 L, respectively. Body weight, postoperative days, CYP3A4*1 G genotype, estimated glomerular filtration rate and coadministration of triazole antifungal drugs were identified as significant covariates for CL. Weight and postoperative days were significant covariates for the V of CsA. Our model can be adopted to optimize the CsA dosing regimen for Chinese children with hematopathy receiving allo-HSCT.

A Single Dose of Baicalin Has No Clinically Significant Effect on the Pharmacokinetics of Cyclosporine A in Healthy Chinese Volunteers

Despite its narrow therapeutic window and large interindividual variability, cyclosporine A (CsA) is the first-line therapy following organ transplantation. Metabolized mainly by CYP3A and being a substrate of P-glycoprotein (P-gp), CsA is susceptible to drug–drug interactions. Baicalin (BG) is a drug used for adjuvant therapy of hepatitis in traditional Chinese medicine. Since its aglycone baicalein (B) inhibits CYP3A and P-gP, co-administration might affect CsA pharmacokinetics. This study investigated the effect of BG on CsA pharmacokinetics. In a two-period study, 16 healthy volunteers received a single 200 mg oral CsA dose alone (reference period) or in combination with 500 mg BG (test period). Pharmacokinetic evaluation of CsA was carried out using non-compartmental analysis (NCA) and population pharmacokinetics (popPK). Treatments were compared using the standard bioequivalence method. Based on NCA, 90% CIs of AUC and C_max test-to-reference ratios were within bioequivalence boundaries. In the popPK analysis, a two-compartment model (clearance/F 62.8 L/h, central and peripheral volume of distribution/F 254 L and 388 L) with transit compartments for absorption appropriately described CsA concentrations. No clinically relevant effect of 500 mg BG co-administration on CsA pharmacokinetics was identified and both treatments were well tolerated.

External evaluation of population pharmacokinetic models for ciclosporin in adult renal transplant recipients

AIMS

Several population pharmacokinetic (popPK) models for ciclosporin (CsA) in adult renal transplant recipients have been constructed to optimize the therapeutic regimen of CsA. However, little is known about their predictabilities when extrapolated to different clinical centres. Therefore, this study aimed to externally evaluate the predictive ability of CsA popPK models and determine the potential influencing factors.

METHODS

A literature search was conducted and the predictive performance was determined for each selected model using an independent data set of 62 patients (471 predose and 500 2-h postdose concentrations) from our hospital. Prediction-based diagnostics and simulation-based normalized prediction distribution error were used to evaluate model predictability. The influence of prior information was assessed using Bayesian forecasting. Additionally, potential factors influencing model predictability were investigated.

RESULTS

Seventeen models extracted from 17 published popPK studies were assessed. Prediction-based diagnostics showed that ethnicity potentially influenced model transferability. Simulation-based normalized prediction distribution error analyses indicated misspecification in most of the models, especially regarding variance. Bayesian forecasting demonstrated that the predictive performance of the models substantially improved with 2-3 prior observations. The predictability of nonlinear Michaelis-Menten models was superior to that of linear compartmental models when evaluating the impact of structural models, indicating the underlying nonlinear kinetics of CsA. Structural model, ethnicity, covariates and prior observations potentially affected model predictability.

CONCLUSIONS

Structural model is the predominant factor influencing model predictability. Incorporation of nonlinear kinetics in CsA popPK modelling should be considered. Moreover, Bayesian forecasting substantially improved model predictability.

Tacrolimus dose requirement based on the CYP3A5 genotype in renal transplant patients

Tacrolimus (FK506) and cyclosporine A (CsA) are widely used to protect graft function after renal transplantation. The aim of the present study is to determine whether the single nucleotide polymorphism of CYP3A5 is a predictive index of FK506 dose requirement, and also the selection yardstick of FK506 or CsA treatment.We tested archival peripheral blood of 218 kidney recipients for CYP3A5 genotyping with PCR-SSP. Meanwhile, the dose of FK506 and CsA was recorded, blood concentration of the drugs was measured, and graft outcome was monitored.These results indicate that CYP3A5*AA/AG carriers need higher FK506 dose than CYP3A5*GG homozygote to achieve the target blood concentration. For CYP3A5*GG carriers, taking FK506 or CsA are both advisable. CYP3A5*AA/AG carriers preferred to CsA treatment depending on the graft outcomes and drug costs. CYP3A5 genotyping is a new approach to detecting FK506 dose requirement and a predictive index for the FK506 or CsA treatment selection in kidney recipients.

Immunosuppressive serum levels in allogeneic hematopoietic stem cell transplantation: pharmaceutical care contribution

BACKGROUND

Cyclosporine and tacrolimus are limited by a narrow therapeutic window. Maintaining immunosuppressive drugs at desired levels may be difficult. Pharmaceutical care emerges as a philosophy of practice that enhances medication use and leads to a better control of serum concentration.

OBJECTIVE

This study aims to evaluate the impact of pharmaceutical care in the maintaining of proper serum levels of immunosuppressive medications in patients who have undergone allo-HSCT.

METHODS

The study had a quasi-experimental design that included a comparison group. The service model used was pharmacotherapy follow-up, according to an adaptation of the Dader method. The pharmacist consultation was carried out at a day-hospital or at the outpatient hematology clinic as needed. The intervention group consisted of 22 patients seen by a clinical pharmacist. The control group consisted of 44 patients that received standard care. This study aims to evaluate the impact of pharmaceutical care on keeping patient serum levels of cyclosporine and tacrolimus within the desired range.

RESULTS

Control group displayed 65% of the proper serum levels of immunosuppressive agents. While In intervention group, the figure was 82% (p = 0.004).

CONCLUSION

The role of the pharmacist in the multidisciplinary team may contribute to a greater success in attaining the patients' therapeutic targets with regard to the use of immunosuppressant.

Population pharmacokinetics of cyclosporine in hematopoietic stem cell transplant patients: consideration of genetic polymorphisms

BACKGROUND

Cyclosporine (CsA), which is used for graft-versus-host disease prophylaxis in allogeneic hematopoietic stem cell transplant (allo-HSCT), has a narrow therapeutic range and large interindividual and intraindividual pharmacokinetic variability. Nevertheless, population pharmacokinetic (PopPK) studies of CsA in allo-HSCT are scarce.

OBJECTIVE

The goal of our study was to build a PopPK model of CsA in allo-HSCT in consideration of demographic, clinical, and genetic polymorphisms data.

METHODS

A total of 34 adult allo-HSCT patients who received CsA were enrolled prospectively. Demographic, clinical, and CYP3A5 *1/*3, CYP2C19 *1/*2/*3, ABCB1 3435C>T, 1236C>T, 2677G>T/A, ABCC2 -24C>T, 1249G>A, VDR Bsml, Apal polymorphisms data were collected. A PopPK modeling was conducted with NONMEM program.

RESULTS

A 1-compartment model with a 2-transit absorption compartment model was developed. After the stepwise covariate model building process, weight was incorporated into clearance (CL) as a power function model with the exponent value of 0.419. The final typical estimate of CL was 21.2 L/h; volume of distribution was 430 L; logit-transformed bioavailability was 1.49 (bioavailability: 81%); and transit compartment rate was 2.87/h. None of the genetic polymorphisms in CYP3A5, CYP2C19, ABCB1, ABCC2, and VDR were significant covariates in the pharmacokinetics of CsA.

CONCLUSIONS

In our study, it was observed that weight had a significant effect on CL. Genetic polymorphisms did not affect CsA pharmacokinetics. Prospective studies with a larger number of participants is needed to validate the results of this study.

Pharmacogenetics and drug-induced nephrotoxicity in renal transplant recipients

INTRODUCTION

The advent of calcineurin inhibitors (CNIs), as the leading immunosuppressive agents, not only has revolutionized the transplant medicine but also made it a better therapeutic intervention that guarantees the graft outcome and improves the survival rate of patients. However, genetic polymorphism(s) in the CNIs metabolic substrates genes (CYP3A4, CYP3A5) and their transporter such as P-glycoprotein (P-gp) can influence the CNIs metabolism and elicit some possible systemic and intra-renal exposures to drugs and/or metabolites with differential risk of nephrotoxicity, jeopardizing the transplantation.

METHODS

In the current study, we review the recent literatures to evaluate the effects of genetic polymorphisms of the genes involved in development of chronic calcineurin nephrotoxicity and progression of chronic allograft dysfunction (CAD) providing an extensive overview on their clinical impacts.

RESULTS

Identifying the inherited genetic basis for the inter-individual differences in terms of drug responses and determining the risk of calcineurin-mediated nephrotoxicity and CAD allow optimized personalized administration of these agents whith minimal adverse effects.

CONCLUSION

Pharmacogenetics characteristics of CYP isoforms (CYP3A) and efflux transporters (P-gp and MRP), involved in metabolism and extracellular transportation of the immunosuppressive CNIs, can be of pivotal information in the pharmacotherapy of the renal-transplant recipients. Such information can be used for the successes clinical interventions to attain an improved drug administration strategy with reduced rates of rejection and toxicity.

Population pharmacokinetics of cyclosporine in transplant recipients

A number of classical pharmacokinetic studies have been conducted in transplant patients. However, they suffer from some limitations, for example, (1) the study design was limited to intense blood sampling in small groups of patients during a certain posttransplant period, (2) patient factors were evaluated one at a time to identify their association with the pharmacokinetic parameters, and (3) mean pharmacokinetic parameters often cannot be precisely estimated due to large intraindividual variability. Population pharmacokinetics provides a potential means of addressing these limitations and is a powerful tool to evaluate the magnitude and consistency of drug exposure. Population pharmacokinetic studies of cyclosporine focused solely on developing limited sampling strategies and Bayesian estimators to estimate drug exposure, have been summarized before, and are, therefore, not a subject of this review. The major focus of this review is to describe factors (demographic factors, hepatic and gastrointestinal functions, drug-drug interactions, genetic polymorphisms of drug metabolizing enzymes and transporters) that have been identified to contribute to the large portion of observed variability in the pharmacokinetics of cyclosporine in transplant patients. This review summarizes and interprets the conclusions as well as the nonlinear mixed-effects modeling methodologies used in such studies. A highly diversified collection of structural models, variability models, and covariate submodels have been evaluated and validated using internal or external validation methods. This review also highlights areas where additional research is warranted to improve the models since a portion of model variability still remains unexplained.

Associations of ABCB1, NFKB1, CYP3A, and NR1I2 polymorphisms with cyclosporine trough concentrations in Chinese renal transplant recipients

AIM

Cyclosporine requires close therapeutic drug monitoring because of its narrow therapeutic index and marked inter-individual pharmacokinetic variation. In this study, we investigated the associations of CYP3A4, CYP3A5, ABCB1, NFKB1, and NR1I2 polymorphisms with cyclosporine concentrations in Chinese renal transplant recipients in the early period after renal transplantation.

METHODS

A total of 101 renal transplant recipients receiving cyclosporine were genotyped for CYP3A4(*)1G, CYP3A5(*)3, ABCB1 C1236T, G2677T/A, C3435T, NFKB1 -94 ins/del ATTG, and NR1I2 polymorphisms. Cyclosporine whole blood levels were measured by a fluorescence polarization immunoassay. Trough concentrations of cyclosporine were determined for days 7-18 following transplantation.

RESULTS

The dose-adjusted trough concentration (C0) of cyclosporine in ABCB1 2677 TT carriers was significantly higher than that in GG carriers together with GT carriers [90.4±24.5 vs 67.8±26.8 (ng/mL)/(mg/kg), P=0.001]. ABCB1 3435 TT carriers had a significantly higher dose-adjusted C0 of cyclosporine than CC carriers together with CT carriers [92.0±24.0 vs 68.4±26.5 (ng/mL)/(mg/kg), P=0.002]. Carriers of the ABCB1 1236TT-2677TT-3435TT haplotype had a considerably higher CsA C0/D than carriers of other genotypes [97.2±21.8 vs 68.7±26.9 (ng/mL)/(mg/kg), P=0.001]. Among non-carriers of the ABCB1 2677 TT and 3435 TT genotypes, patients with the NFKB1 -94 ATTG ins/ins genotype had a significantly higher dose-adjusted C0 than those with the -94 ATTG del/del genotype [75.9±32.9 vs 55.1±15.1 (ng/mL)/(mg/kg), P=0.026].

CONCLUSION

These results illustrate that the ABCB1 and NFKB1 genotypes are closely correlated with cyclosporine trough concentrations, suggesting that these SNPs are useful for determining the appropriate dose of cyclosporine.