A model based on machine learning for the prediction of cyclosporin A trough concentration in Chinese allo-HSCT patients

BACKGROUND

Cyclosporin A is a calcineurin inhibitor which has a narrow therapeutic window and high interindividual variability. Various population pharmacokinetic models have been reported; however, professional software and technical personnel were needed and the variables of the models were limited. Therefore, the aim of this study was to establish a model based on machine learning to predict CsA trough concentrations in Chinese allo-HSCT patients.

METHODS

A total of 7874 cases of CsA therapeutic drug monitoring data from 2069 allo-HSCT patients were retrospectively included. Sequential forward selection was used to select variable subsets, and eight different algorithms were applied to establish the prediction model.

RESULTS

XGBoost exhibited the highest prediction ability. Except for the variables that were identified by previous studies, some rarely reported variables were found, such as norethindrone, WBC, PAB, and hCRP. The prediction accuracy within ±30% of the actual trough concentration was above 0.80, and the predictive ability of the models was demonstrated to be effective in external validation.

CONCLUSION

In this study, models based on machine learning technology were established to predict CsA levels 3-4 days in advance during the early inpatient phase after HSCT. A new perspective for CsA clinical application is provided.

Effect of polymorphisms in drug metabolism and transportation on plasma concentration of atorvastatin and its metabolites in patients with chronic kidney disease

Dyslipidemia due to renal insufficiency is a common complication in patients with chronic kidney diseases (CKD), and a major risk factor for the development of cardiovascular events. Atorvastatin (AT) is mainly used in the treatment of dyslipidemia in patients with CKD. However, response to the atorvastatin varies inter-individually in clinical applications. We examined the association between polymorphisms in genes involved in drug metabolism and transport, and plasma concentrations of atorvastatin and its metabolites (2-hydroxy atorvastatin (2-AT), 2-hydroxy atorvastatin lactone (2-ATL), 4-hydroxy atorvastatin (4-AT), 4-hydroxy atorvastatin lactone (4-ATL), atorvastatin lactone (ATL)) in kidney diseases patients. Genotypes were determined using TaqMan real time PCR in 212 CKD patients, treated with 20 mg of atorvastatin daily for 6 weeks. The steady state plasma concentrations of atorvastatin and its metabolites were quantified using ultraperformance liquid chromatography in combination with triple quadrupole mass spectrometry (UPLC-MS/MS). Univariate and multivariate analyses showed the variant in ABCC4 (rs3742106) was associated with decreased concentrations of AT and its metabolites (2-AT+2-ATL: β = -0.162, p = 0.028 in the dominant model; AT+2-AT+4-AT: β = -0.212, p = 0.028 in the genotype model), while patients carrying the variant allele ABCC4-rs868853 (β = 0.177, p = 0.011) or NR1I2-rs6785049 (β = 0.123, p = 0.044) had higher concentrations of 2-AT+2-ATL in plasma compared with homozygous wildtype carriers. Luciferase activity was enhanced in HepG2 cells harboring a construct expressing the rs3742106-T allele or the rs868853-G allele (p < 0.05 for each) compared with a construct expressing the rs3742106G or the rs868853-A allele. These findings suggest that two functional polymorphisms in the ABCC4 gene may affect transcriptional activity, thereby directly or indirectly affecting release of AT and its metabolites from hepatocytes into the circulation.

Factors Affecting Time-Varying Clearance of Cyclosporine in Adult Renal Transplant Recipients: A Population Pharmacokinetic Perspective

AIM

The pharmacokinetic (PK) properties of cyclosporine (CsA) in renal transplant recipients are patient- and time-dependent. Knowledge of this time-related variability is necessary to maintain or achieve CsA target exposure. Here, we aimed to identify factors explaining variabilities in CsA PK properties and characterize time-varying clearance (CL/F) by performing a comprehensive analysis of CsA PK factors using population PK (popPK) modeling of long-term follow-up data from our institution.

METHODS

In total, 3674 whole-blood CsA concentrations from 183 patients who underwent initial renal transplantation were analyzed using nonlinear mixed-effects modeling. The effects of potential covariates were selected according to a previous study and well-accepted theoretical mechanisms. Model-informed individualized therapeutic regimens were also evaluated.

RESULTS

A two-compartment model adequately described the data and the estimated mean CsA CL/F was 32.6 L h^-1 (relative standard error: 5%). Allometrically scaled body size, hematocrit (HCT) level, CGC haplotype carrier status, and postoperative time may contribute to CsA PK variability. The CsA bioavailability in patients receiving a prednisolone dose (PD) of 80 mg was 20.6% lower than that in patients receiving 20 mg. A significant decrease (52.6%) in CL/F was observed as the HCT increased from 10.5% to 60.5%. The CL/F of the non-CGC haplotype carrier was 14.4% lower than that of the CGC haplotype carrier at 3 months post operation.

CONCLUSIONS

By monitoring body size, HCT, PD, and CGC haplotype, changes in CsA CL/F over time could be predicted. Such information could be used to optimize CsA therapy. CsA dose adjustments should be considered in different postoperative periods.

Incorporating nonlinear kinetics to improve predictive performance of population pharmacokinetic models for ciclosporin in adult renal transplant recipients: A comparison of modelling strategies

BACKGROUND

Ciclosporin has been shown to follow nonlinear pharmacokinetics (PK) in renal transplant recipients who received ciclosporin (Neoral^Ⓡ, Novartis)-based triple immunosuppressive therapy. Some of these nonlinear properties have not been fully considered in population PK (popPK) analysis. Therefore, the aim of this study was to determine the potential influence of nonlinearity and the functional forms of covariates on model predictability as well as to analyse multiple nonlinear factors in the in vivo process.

METHODS

A total of 2969 ciclosporin whole-blood measurements, including 1328 pre-dose and 1641 2-h post-dose concentrations, were collected from 173 patients who underwent their first renal transplantation. Four popPK models based on different modelling strategies were developed to investigate the discrepancy between empirical and theory-based, linear and nonlinear compartmental kinetic models and empirical formulae on model predictability. Prediction and simulation-based diagnostics (prediction-corrected visual predictive checks) were performed to determine the stability and predictive performance of these four models.

RESULTS

Model predictability improved when nonlinearity was considered. The theory-based nonlinear model which incorporated nonlinear property based on known theoretical relationships performed better than the other two compartmental models. The nonlinear Michaelis-Menten model showed a remarkable improvement in predictive performance compared to the other three compartmental models. The saturated binding of ciclosporin to erythrocytes, auto-inhibition induced by the inhibitory effects of ciclosporin on cytochrome P450 3A4/P-glycoprotein may have contributed to the nonlinearity. Ciclosporin-prednisolone drug interaction should be given serious consideration in clinical settings.

CONCLUSIONS

Incorporation of nonlinear properties is likely to be a promising approach for improving ciclosporin model predictability. Theory-based modelling is helpful to improve model predictability. However, ciclosporin nonlinear kinetics resources need further investigation.

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.

Metabolic Pathway of Cyclosporine A and Its Correlation with Nephrotoxicity

Background:

Cyclosporine A (CsA) is widely used for organ transplantation and autoimmune disorders. However, CsA nephrotoxicity is a serious side effect that limits the clinical use of CsA. The metabolism of CsA has a close relationship with this disease in renal-transplant patients. However, the metabolic pathways of CsA and its metabolizing enzymes have rarely been comprehensively reviewed. In this review, we have summarized the specific metabolic profiles of CsA in humans, especially renal-transplant patients. Moreover, the specific metabolizing enzymes and the potential roles that CsA metabolism plays in CsA nephrotoxicity were summarized and discussed.

Methods:

Electronic databases including PubMed, Web of Science, and Scifinder were searched with the keywords "Cyclosporine A and metabolism", and "Cyclosporine A and nephrotoxicity", "Cyclosporine A metabolism and nephrotoxicity". All these studies published until 2018 were included in this review.

Results:

The major metabolic pathways of CsA in humans are hydroxylation and N-demethylation. Normally, these metabolites are relatively less toxic than CsA. However, the metabolism of CsA in the kidneys is much weaker than that in the liver, which explains why CsA is so toxic to the kidneys. CYP3A families, especially CYP3A4 and CYP3A5, play an important role in the biotransformation of CsA. Moreover, increased lines of evidence show that some metabolites (including AM19) associate directly with nephrotoxicity in CsA-treated organ-transplant patients.

Conclusion:

The findings of this review help to further understand the metabolic activities of CsA in renal-transplant patients and cast some light on the mechanisms of CsA nephrotoxicity.

Genetic variations of the xenoreceptors NR1I2 and NR1I3 and their effect on drug disposition and response variability

NR1I2 (PXR) and NR1I3 (CAR) are nuclear receptors that are classified as xenoreceptors. Upon activation by various xenobiotics, including marketed drugs, they regulate the transcription level of major drug-metabolizing enzymes and transporters and facilitate the elimination of xenobiotics from the body. The modulation of the activity of these two xenoreceptors by various ligands is a major source of pharmacokinetic variability of environmental origin. NR1I2 and NR1I3 genetic polymorphisms can affect the pharmacokinetics and therapeutic response to many drugs, such as irinotecan, tacrolimus and atazanavir. This review provides an overview of NR1I2 and NR1I3 pharmacogenetic studies in various therapeutic fields (oncology, immunomodulation and infectiology) and discusses the implementation of NR1I2 and NR1I3 genetic polymorphism testing in the clinical routine.

Effects of Polymorphisms in NR1H4, NR1I2, SLCO1B1, and ABCG2 on the Pharmacokinetics of Rosuvastatin in Healthy Chinese Volunteers

The nuclear receptors (NR)-farnesoid X receptor (FXR, NR1H4) and pregnane X receptor (PXR, NR1I2)-have important effects on the expression of genes related to the pharmacokinetics (PKs) of rosuvastatin. This study was designed to investigate whether the genetic variants in drug disposition genes (SLCO1B1 and ABCG2) combined with their upstream regulators (NR1H4 and NR1I2) would affect the PKs of rosuvastatin in a Chinese population. Sixty-one healthy male volunteers were enrolled and the plasma concentrations of rosuvastatin were measured using the liquid chromatographic-tandem mass spectrometry/MS method. All subjects were analyzed and grouped according to the genotypes of NR1H4, NR1I2, SLCO1B1, and ABCG2. The exposure of rosuvastatin was higher in subjects carrying the SLCO1B1 521C or ABCG2 421A allele compared with noncarriers. No association was observed of single-nucleotide polymorphisms in NR1H4 or NR1I2 genes with the PKs of rosuvastatin. After adjusting for the 421C>A and 521T>C variants, the Cmax in subjects with NR1I2 63396TT wild type were about 2-fold of those of NR1I2 mutant type (63396CC and CT) (10.7 vs. 20.4 ng/mL, P = 0.023), whereas no significant differences were observed for other parameters. Polymorphisms investigated in the genes of NR1H4 and NR1I2 seemed to play no significant role in the disposition of rosuvastatin.

Immunosuppression in pediatric liver transplant recipients: Unique aspects

Pediatric liver transplantation has experienced improved outcomes over the last 50 years. This can be attributed in part to establishing optimal use of immunosuppressive agents to achieve a balance between minimizing the risks of allograft rejection and infection. The management of immunosuppression in children is generally more complex and can be challenging when compared with the use of these agents in adult liver transplant patients. Physiologic differences in children alter the pharmacokinetics of immunosuppressive agents, which affects absorption, distribution, metabolism, and drug excretion. Children also have a longer expected period of exposure to immunosuppression, which can impact growth, risk of infection (bacterial, viral, and fungal), carcinogenesis, and likelihood of nonadherence. This review discusses immunosuppressive options for pediatric liver transplant recipients and the unique issues that must be addressed when managing this population. Further advances in the field of tolerance and accommodation are needed to relieve the acute and cumulative burden of chronic immunosuppression in children. Liver Transplantation 23 244-256 2017 AASLD.

A time-to-event model for acute rejections in paediatric renal transplant recipients treated with ciclosporin A

AIMS

Ciclosporin A (CsA) dosing in immunosuppression after paediatric kidney transplantation remains challenging, and appropriate target CsA exposures (AUCs) are controversial. This study aimed to develop a time-to-first-acute rejection (AR) model and to explore predictive factors for therapy outcome.

METHODS

Patient records at the Children's Hospital in Helsinki, Finland, were analysed. A parametric survival model in NONMEM was used to describe the time to first AR. The influences of AUC and other covariates were explored using stepwise covariate modelling, bootstrap-stepwise covariate modelling and cross-validated stepwise covariate modelling. The clinical relevance of the effects was assessed with the time at which 90% of the patients were AR free (t90).

RESULTS

Data from 87 patients (0.7-19.8 years old, 54 experiencing an AR) were analysed. The baseline hazard was described with a function changing in steps over time. No statistically significant covariate effects were identified, a finding substantiated by all methods used. Thus, within the observed AUC range (90% interval 1.13-8.40 h mg l⁻¹), a rise in AUC was not found to increase protection from AR. Dialysis time, sex and baseline weight were potential covariates, but the predicted clinical relevance of their effects was low. For the strongest covariate, dialysis time, median t90 was 5.8 days (90% confidence interval 5.1-6.8) for long dialysis times (90th percentile) and 7.4 days (6.4-11.7) for short dialysis times (10th percentile).

CONCLUSIONS

A survival model with discrete time-varying hazards described the data. Within the observed range, AUC was not identified as a covariate. This feedback on clinical practice may help to avoid unnecessarily high CsA dosing in children.

Long-term effects of ABCB1 and SXR SNPs on the systemic exposure to cyclosporine in pediatric kidney transplant patients

Aim: Cyclosporine is characterized by a wide interindividual variability in its pharmacokinetics. The objective of this study was to evaluate the effects of ABCB1 and SXR SNPs on cyclosporine exposure in a group of kidney transplant patients followed up from childhood to adulthood. Patients & methods: Recipients were genotyped for ABCB1 C1236T, G2677T/A and C3435T, and for SXR RS3842689 and A7635G. Dose-adjusted trough levels and weight-adjusted daily doses were compared among patients according to allelic status by a generalized estimation equation approach that allows longitudinal data analyses. Results: A genotype-dependent effect was found in all ABCB1 genotypes and in one of the SXR SNPs. This effect was particularly evident for the TT genotype of the ABCB1 G2677T/A SNP, the TT genotype of the ABCB1 C3435T SNP and for heterozygotes of the deletion of 6 bp in the promoter region of SXR. Conclusion: The presence of specific ABCB1 and SXR SNPs could significantly affect cyclosporine exposure during a kidney transplant patient’s development from childhood to adulthood in a time-dependent fashion.

Original submitted 3 May 2013; Revision submitted 25 July 2013

From gut to kidney: transporting and metabolizing calcineurin-inhibitors in solid organ transplantation

Since their introduction circa 35 years ago, calcineurin-inhibitors (CNI) have become the cornerstone of immunosuppressive therapy in solid organ transplantation. However, CNI's possess a narrow therapeutic index with potential severe consequences of drug under- or overexposure. This demands a meticulous policy of Therapeutic Drug Monitoring (TDM) to optimize outcome. In clinical practice optimal dosing is difficult to achieve due to important inter- and intraindividual variation in CNI pharmacokinetics. A complex and often interdependent set of factors appears relevant in determining drug exposure. These include recipient characteristics such as age, race, body composition, organ function, and food intake, but also graft-related characteristics such as: size, donor-age, and time after transplantation can be important. Fundamental (in vitro) and clinical studies have pointed out the intrinsic relation between the aforementioned variables and the functional capacity of enzymes and transporters involved in CNI metabolism, primarily located in intestine, liver and kidney. Commonly occurring polymorphisms in genes responsible for CNI metabolism (CYP3A4, CYP3A5, CYP3A7, PXR, POR, ABCB1 (P-gp) and possibly UGT) are able to explain an important part of interindividual variability. In particular, a highly prevalent SNP in CYP3A5 has proven to be an important determinant of CNI dose requirements and drug-dose-interactions. In addition, a discrepancy in genotype between graft and receptor has to be taken into account. Furthermore, common phenomena in solid organ transplantation such as inflammation, ischemia- reperfusion injury, graft function, co-medication, altered food intake and intestinal motility can have a differential effect on the expression enzymes and transporters involved in CNI metabolism. Notwithstanding the built-up knowledge, predicting individual CNI pharmacokinetics and dose requirements on the basis of current clinical and experimental data remains a challenge.

Nuclear receptors PXR and CAR: implications for drug metabolism regulation, pharmacogenomics and beyond

INTRODUCTION

'Orphan' nuclear receptors belong to the nuclear receptor (NR) superfamily of transcriptional factors. Binding of ligands to these receptors results in the recruitment of the co-activators, thereby regulating the expression of cognate target genes.

AREAS COVERED

This review discusses the transcriptional regulation of P450 genes by two major xenobiotic nuclear receptors, pregnane X receptor (PXR) and constitutive androstane receptor (CAR). Additional PXR and CAR target genes include those encoded for UDP-glucuronosyltransferases, glutathione S-transferases, sulfotransferases and drug transporters. The authors discuss the involvement of PXR and CAR in endobiotic metabolism. They also review the polymorphisms of PXR and CAR.

EXPERT OPINION

PXR and CAR are both xenobiotic and endobiotic receptors. A remarkably diverse set of chemicals can activate PXR and CAR. There is significant cross-talk among xenobiotic receptors. Future studies are needed to focus on the polymorphisms of the nuclear receptors and the complex regulatory networks among nuclear receptors. Considerations should be given while designing PXR- or CAR-targeting pharmaceutics to avoid adverse drug effects. In the meantime, due to the diverse functions of PXR and CAR, agonists or antagonists for these receptors may have therapeutic potentials in managing certain diseases and enhancing therapeutic indexes.

The potential of steroids and xenobiotic receptor polymorphisms in forecasting cyclosporine pharmacokinetic variability in young kidney transplant recipients

The steroids and xenobiotics receptor (SXR) up-regulates the expression and the synthesis of key enzymes in CyA metabolism. In this study, we examined the possible interactions between CyA exposure and SXR polymorphisms during the first year after renal transplantation. The study involved 66 pediatric renal transplant recipients (25 women and 41 men, mean age 13.9 ± 7.4 yr). All patients were genotyped for two sequence variations in the NR1I2 gene: g.-205_-200delGAGAAG and 7635 A>G. CyA trough levels and CyA weight-adjusted daily dose were recorded at 30, 90, 180, and 360 days after transplantation and compared between the different genotypes. A third newly discovered SXR polymorphism was characterized and also included in the study. CyA trough levels and CyA weight-adjusted daily dose were comparable on four time points throughout the first year post-transplant in all three groups. GEE showed a significant reduction in weight-adjusted CyA daily dose in patients carrying the deletion of 6 bp in SXR with a significant group-by-time effect that persisted also when analysis was corrected for age, prednisone dose, and acute rejection episodes. In our group of patients, only the g.-205_-200delGAGAAG SXR polymorphism was able to influence the metabolism of CyA continuously, during the first year after transplantation.

Polymorphisms in CYP3A5, CYP3A4, and ABCB1 are not associated with cyclosporine pharmacokinetics nor with cyclosporine clinical end points after renal transplantation

BACKGROUND

The association of CYP3A5, CYP3A4, and ABCB1 single nucleotide polymorphisms (SNPs) with cyclosporine (CsA) pharmacokinetics is controversial. The authors studied the influence of these SNPs on CsA pharmacokinetics as well as on the incidence of biopsy-proven acute rejection (BPAR) and renal function after kidney transplantation.

METHOD

One hundred seventy-one patients participating in an international, randomized controlled trial were genotyped for CYP3A5*3, CYP3A4*1B and the ABCB1 1236 C>T, 2677 G>T/A, and 3435 C>T SNPs. The patients were treated with CsA, mycophenolate mofetil, and glucocorticoids. CsA was dosed to reach predose concentrations (C0) or two hours postdose concentrations (C2). Pharmacokinetic parameters were measured on Days 3 and 10 and Months 1, 3, 6, and 12 after transplantation. Renal function was assessed by measuring serum creatinine and calculating the creatinine clearance. The incidence of BPAR and delayed-graft function was recorded.

RESULTS

CYP3A5, CYP3A4, and ABCB1 genotype were not associated with dose-adjusted CsA C0 or C2. The incidence of BPAR in this cohort was 16% and was comparable between the different ABCB1 genotype groups. No significant difference in the incidence of BPAR was found between CYP3A5 expressers (10%) and nonexpressers (18%) (P = 0.24) nor was there a difference in the incidence of BPAR between CYP3A4*1 homozygotes (5%) versus CYP3A4*1B carriers (18%) (P = 0.13). There were no differences with regard to creatinine clearance between the different CYP3A and ABCB1 genotype groups.

CONCLUSION

According to the results, determination of CYP3A and ABCB1 SNPs pretransplantation is not helpful in determining the CsA starting dose and does not aid in predicting the risk of BPAR or worse renal function in an individual patient.

Dried blood spots, pharmacokinetic studies and better medicines for children

Determining circulating drug concentrations in children is an ongoing obstacle to the development of age-appropriate dosing regimens. The requirement for small blood sample volumes in children compared with adults is a significant barrier to obtaining age-specific pharmacokinetic-pharmacodynamic data for this population and hence optimizing the efficacy and safety profile of medicines used by this group. This article discusses the potential for dried blood spot sampling to offer a solution to this issue.

Lack of association of ABCB1 and PXR polymorphisms with response to treatment in epilepsy

It is proposed that overexpression of P-glycoprotein (P-gp), encoded by the ABC subfamily B member 1 (ABCB1) gene, is involved in resistance to antiepileptic drugs (AEDs) in about 30% of patients with epilepsy. Genetic variation and haplotype patterns are population specific which may cause different phenotypes such as response to AEDs. Although several studies examined the link between the common polymorphisms in the ABCB1 gene with resistance to AEDs, the results have been conflicting. This controversy may be caused by the effect of some confounders such as ethnicity and polytherapy. Moreover, expression of the ABCB1 gene is under the control of pregnane X receptor (PXR). Evidence showed that PXR gene contribute to the response to treatment. The aim of this study was to assess the association of ABCB1 and PXR genetic polymorphisms with response to the carbamazepine (CBZ) or sodium valproate (VPA) monotherapy in epilepsy. Genotypes were assessed in 685 Chinese, Indian, and Malay epilepsy patients for ABCB1 (C1236T, G2677T, C3435T) and PXR (G7635A) polymorphisms. No association between these polymorphisms and their haplotypes, and interaction between them, with response to treatment was observed in the overall group or in the Chinese, Indian, and Malay subgroups. Our data showed that these polymorphisms may not contribute to the response to CBZ or VPA monotherapy treatment in epilepsy.