Neoral monitoring by simplified sparse sampling area under the concentration-time curve: its relationship to acute rejection and cyclosporine nephrotoxicity early after kidney transplantation

Therapeutic drug monitoring in kidney and liver transplantation: current advances and future directions

INTRODUCTION

Immunosuppressive drugs (ISD) present a narrow therapeutic window and extremely high inter- and intra-individual pharmacokinetic variability, which complicates their use in solid organ transplant recipients. In order to find a narrow appropriate equilibrium for each patient with the aim of maintaining clinical efficacy and reducing the risk of adverse drug reactions, a complex both clinical and biological monitoring is required, in particular through the use of therapeutic drug monitoring (TDM).

AREA COVERED

This review provides an overview of the available information on the relationship between exposure to immunosuppressive drugs and their efficacy and/or toxicity in kidney and liver transplantation. The aim of the review is to describe the pharmacodynamic/pharmacokinetic relationship that exists for immunosuppressive drugs, to summarize the studies that assess the value of TDM for these drugs in clinical practice, and to present the target and monitoring strategies aimed at optimizing patient immunosuppression, which could help to take a step forward in the field of solid organ transplant patient care.

EXPERT OPINION

To improve the care of transplant patients, several TDM innovations can be pursued by investigators. Among these, the development of microsampling methods for TDM or the combination of pharmacodynamic biomarkers with ISD exposure measurements appear to be relevant strategies.

Time-Dissociated Pharmacokinetic Pharmacodynamic Model of Cyclosporine Among Malaysian Renal Transplant Recipients

BACKGROUND

Cyclosporine is an essential component of many immunosuppressive regimens. However, its pharmacokinetic and pharmacodynamic (PKPD) modeling has not been widely investigated. This study aims to develop a time-dissociated PKPD model of cyclosporine in renal transplant patients.

METHODS

Medical records of renal transplant patients at Penang General Hospital were retrospectively analyzed. A time-dissociated PKPD model with covariate effects was developed using NONMEM to evaluate renal graft function response, quantified as estimated glomerular filtration rate (eGFR), toward the cyclosporine cumulative exposure (area under the concentration-time curve). The final model was integrated into a tool to predict the potential outcome. Individual eGFR predictions were evaluated based on the clinical response recorded as acute rejection/nephrotoxicity events.

RESULTS

A total of 1256 eGFR readings with 2473 drug concentrations were obtained from 107 renal transplant patients receiving cyclosporine. An Emax drug effect with a linear drug toxicity model best described the data. The baseline renal graft level (E0), maximum effect (Emax), area under the concentration-time curve achieving 50% of the maximum effect, and nephrotoxicity slope were estimated as 12.9 mL·min-1·1.73 m-2, 50.7 mL·min-1·1.73 m-2, 1740 ng·h·mL-1, and 0.00033, respectively. The hemoglobin level was identified as a significant covariate affecting the E0. The model discerned acute rejection from nephrotoxicity in 19/24 cases.

CONCLUSIONS

A time-dissociated PKPD model successfully described a large number of observations and was used to develop an online tool to predict renal graft response. This may help discern early rejection from nephrotoxicity, especially for patients unwilling to undergo a biopsy or those waiting for biopsy results.

Analysis of the variable factors affecting changes in the blood concentration of cyclosporine before and after transfusion of red blood cell concentrate

Background

The blood concentration of cyclosporine (CyA) is frequently elevated following the transfusion of red blood cell concentrate (RCC) to patients after allogeneic hematopoietic stem cell transplantation (HSCT). The aim of this retrospective study was to identify the variable factors affecting changes in the blood concentration of CyA before and after transfusion of RCC.

Methods

We enrolled 105 patients (age, 5–66 years) who received both CyA and transfusion after HSCT. The ratio of the measurement after transfusion to the measurement before transfusion was calculated for the hematocrit and blood concentration/dose ratio of CyA (termed the HCT ratio and the CyA ratio, respectively).

Results

The blood concentration/dose ratio of CyA was increased after transfusion compared with before transfusion (P < 0.001). The HCT ratio was significantly correlated with the CyA ratio (P = 0.23, P < 0.001). The HCT ratio, concomitant medication that could elevate CyA concentration after RCC transfusion, and difference in the alkaline phosphatase level between before and after transfusion (ΔALP) were explanatory variables associated with the variation in the CyA ratio. There was no correlation between the CyA concentration after transfusion and the change in the estimated glomerular filtration rate.

Conclusions

A change in the blood concentration/dose ratio of CyA was found to be associated with a change in the HCT, concomitant medication that could elevate CyA concentration after RCC transfusion, and ALP levels. If the HCT level rises significantly after RCC transfusion, clinicians and pharmacists should pay attention to changes in the blood CyA concentration.

Continuous cyclosporine a infusion in patients with severe Kawasaki disease

BACKGROUND

The efficacy and safety of continuous intravenous infusion of cyclosporine A (CICsA) in patients with intravenous immunoglobulin-resistant Kawasaki disease are unclear.

METHODS

Between 2010 and 2020, 83 patients with Kawasaki disease that was not responsive to intravenous immunoglobulin (total dose ≥ 4 g/kg) were enrolled. All patients were started on CICsA (3 mg/kg/day) and switched to oral cyclosporine A (CsA) (4-6 mg/kg/day). Treatment efficacy, occurrence of coronary artery lesions (CALs), and laboratory parameters were evaluated. Patients were divided into two groups according to CICsA response: the responder group (afebrile ≤24 h after CICsA without additional treatment) and the weak responder group (afebrile >24 h after CICsA requiring additional treatment).

RESULTS

Fifty-five patients became afebrile within 24 and 74 h became afebrile in less than 72 h. Adverse events included hypertension in four and hyperkalemia in two patients. Thirty-nine patients were defined as responders and 44 patients as weak responders. There were no significant differences in CAL between the two groups. In weak responders, white blood cells, neutrophils, and C-reactive protein levels were higher, and albumin, immunoglobulin G, and CsA concentration were lower than in responders, indicating that weak responders had more severe inflammatory findings. However, there were no significant differences in CAL. Logistic regression analysis revealed that the response to treatment for CICsA was associated with immunoglobulin G levels at baseline and CsA concentrations the day after CICsA.

CONCLUSION

Although CICsA required additional treatments in about half of the cases, a favorable clinical course was observed by using this strategy, especially for reducing CAL.

Association Between Blood and Lymphocyte Levels of Cyclosporin A and Infectious Complications in Renal Transplant Patients

Objectives

This study aims to investigate a potential association between whole blood and lymphocyte Cyclosporin A (CyA) levels and the occurrence and frequency of infectious complications in kidney transplant patients.

Methods

The study involves 130 kidney transplant recipients who received CyA in addition to Mycophenolate Mofetil and steroids. CyA whole blood trough and maximum level (CyA BL₀ and CyA BLm) as well as the corresponding levels in the lymphocytes (CyA L₀ and CyA Lm) were measured for 6 months post-transplantation.

Results

Cytomegalovirus (CMV) as well as urinary tract infections (UTIs) were the most commonly diagnosed with an incidence of 24.6% and 26.2%, respectively. Only CyA L₀ showed a significant association with CMV infection occurrence (adjusted OR = 1.051, 95% CI .997–1.025, P-value 0.046). A positive linear correlation was found between CyA BL₀, CyA BLm and CyA Lm and the number of CMV episodes per patient.

Conclusion

We showed an association between the CMV infections occurrence and the trough lymphocyte level of CyA (CyA L₀). Both lymphocyte CyA levels also correlated with the frequency of CMV infections. Further studies are needed to establish the optimal range of both CyA blood and lymphocyte levels and decrease the risk of opportunistic infections in high risk patients.

Cyclosporine A C1.5 monitoring reflects the area under the curve in children with nephrotic syndrome: a single-center experience

BACKGROUND

The currently used single-monitoring method for drug-blood-level evaluation in cyclosporine A (CsA) treatment for nephrotic syndrome (NS) was established through hourly measurements based on adult organ transplantation. However, the pharmacokinetics may differ due to different concomitant medications, age, and conditions. This study was conducted to determine the measurement timing that best reflects the CsA area under the curve (AUC) in pediatric NS.

METHODS

This retrospective study included children aged 2-14 years who were started on CsA treatment for idiopathic NS during 2013-2020. AUC_0-4 was calculated from 7 points, before and 0.5, 1, 1.5, 2, 3, and 4 h after administration. Mean values at each timing were compared with age-dependent different drug forms. Correlation between AUC_0-4 and measurement timing was analyzed.

RESULTS

There were 13 patients (11 boys) whose median age during testing was 7.3 years, and the total number of measurements was 94. The highest timing of CsA concentrations was found in C₁ 59.6%. The content liquid used at younger ages had a faster absorption time to peak value and lower blood concentration than those of capsules. Among the significant correlations observed, AUC_0-4 and C_1.5 showed the strongest significant correlation coefficient (r = 0.93, P < 0.001).

CONCLUSION

In pediatric NS, CsA metabolism may be faster than that in previous organ transplantation. Compared with C₂, C_1.5 monitoring may result in better disease control as it can best reflect the AUC_0-4 and peak values associated with side effects, which are indicators of therapeutic efficacy.

Measuring Intracellular Concentrations of Calcineurin Inhibitors: Expert Consensus from the International Association of Therapeutic Drug Monitoring and Clinical Toxicology Expert Panel

BACKGROUND

Therapeutic drug monitoring (TDM) of the 2 calcineurin inhibitors (CNIs), tacrolimus (TAC) and cyclosporin A, has resulted in improvements in the management of patients who have undergone solid organ transplantation. As a result of TDM, acute rejection (AR) rates and treatment-related toxicities have been reduced. Irrespective, AR and toxicity still occur in patients who have undergone transplantation, showing blood CNI concentrations within the therapeutic range. Moreover, the AR rate is no longer decreasing. Hence, smarter TDM approaches are necessary. Because CNIs exert their action inside T lymphocytes, intracellular CNIs may be a promising candidate for improving therapeutic outcomes. The intracellular CNI concentration may be more directly related to the drug effect and has been favorably compared with the standard, whole-blood TDM for TAC in liver transplant recipients. However, measuring intracellular CNIs concentrations is not without pitfalls at both the preanalytical and analytical stages, and standardization seems essential in this area. To date, there are no guidelines for the TDM of intracellular CNI concentrations.

METHODS

Under the auspices of the International Association of TDM and Clinical Toxicology and its Immunosuppressive Drug committees, a group of leading investigators in this field have shared experiences and have presented preanalytical and analytical recommendations for measuring intracellular CNI concentrations.

Development of a Population Pharmacokinetic Model for Cyclosporine from Therapeutic Drug Monitoring Data

Aim

To develop a population pharmacokinetic model for Uruguayan patients under treatment with cyclosporine (CsA) that can be applied to TDM. Patients and Methods. A total of 53 patients under treatment with CsA were included. 37 patients with at least one pharmacokinetic profile described with four samples were considered for model building, while the remaining 16 were considered for the assessments of predictive performances. Pharmacokinetic parameter estimation was performed using a nonlinear mixed effect modelling implemented in the Monolix® software (version 2019R1, Lixoft, France); meanwhile, simulations were performed in R v.3.6.0 with the mlxR package.

Results

A two-compartment model with a first-order disposition model including lag time was used as a structural model. The final model was internally validated using prediction corrected visual predictive check (pcVPC) and other graphical diagnostics. A total of 621 CsA steady-state concentrations were analyzed for model development. Population estimates for the absorption constant (ka) and lag time were 0.523 h⁻¹ and 0.512 h, respectively; apparent clearance (CL/F) was 30.3 L/h (relative standard error [RSE] ± 8.25%) with an interindividual variability of 39.8% and interoccasion variability of 38.0%; meanwhile, apparent clearance of distribution (Q/F) was 17.0 L/h (RSE ± 12.1%) with and interindividual variability of 53.2%. The covariate analysis identified creatinine clearance (ClCrea) as an individual factor influencing the Cl of CsA. The predictive capacity of the population model was demonstrated to be effective since predictions made for new patients were accurate for C1 and C2 (MPPEs below 50%). Bayesian forecasting improved significantly in the second and third occasions.

Conclusion

A population pharmacokinetic model was developed to reasonably estimate the individual cyclosporine clearance for patients. Hence, it can be utilized to individualize CsA doses for prompt and adequate achievement of target blood concentrations of CsA.

Sensitive, wide-range and high-throughput quantification of cyclosporine in whole blood using ultra-performance liquid chromatography coupled to tandem mass spectrometry and comparison with an antibody-conjugated magnetic immunoassay

Because either trough or peak concentration at 2 h after administration is measured in routine therapeutic drug monitoring for cyclosporine A (CyA), a quantification method with a wide-range calibration curve capable of simultaneously measuring both concentrations is required. We developed a sensitive, wide-range and high-throughput quantification method for CyA in whole blood using ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS), and compared patients' blood CyA levels measured by UPLC-MS/MS and antibody-conjugated magnetic immunoassay (ACMIA). Whole blood samples were prepared by solid-phase extraction using Oasis HLB μElution plate. The UPLC-MS/MS assay showed excellent linearity over a wide calibration range of 5-2500 ng/mL. Within-batch accuracy and precision as well as batch-to-batch accuracy and precision fulfilled the criteria of US Food and Drug Administration guidelines. The blood CyA concentrations measured by the UPLC-MS/MS assay correlated strongly with those measured by ACMIA. A Bland-Altman plot showed a fixed error between CyA concentrations measured by the two methods, and the concentrations measured by the UPLC-MS/MS method were consistently lower than those measured by ACMIA. We have succeeded to develop a sensitive, wide-range and high-throughput quantification method for CyA in whole blood using UPLC-MS/MS.

Evidence for the alloimmune basis and prognostic significance of Borderline T cell-mediated rejection

Prognostic biomarkers of T cell-mediated rejection (TCMR) have not been adequately studied in the modern era. We evaluated 803 renal transplant recipients and correlated HLA-DR/DQ molecular mismatch alloimmune risk categories (low, intermediate, high) with the severity, frequency, and persistence of TCMR. Allograft survival was reduced in recipients with Banff Borderline (hazard ratio [HR] 2.4, P = .003) and Banff ≥ IA TCMR (HR 4.3, P < .0001) including a subset who never developed de novo donor-specific antibodies (P = .002). HLA-DR/DQ molecular mismatch alloimmune risk categories were multivariate correlates of Banff Borderline and Banff ≥ IA TCMR and correlated with the severity and frequency of rejection episodes. Recipient age, HLA-DR/DQ molecular mismatch category, and cyclosporin vs tacrolimus immunosuppression were independent correlates of Banff Borderline and Banff ≥ IA TCMR. In the subset treated with tacrolimus (720/803) recipient age, HLA-DR/DQ molecular mismatch category, and tacrolimus coefficient of variation were independent correlates of TCMR. The correlation of HLA-DR/DQ molecular mismatch category with TCMR, including Borderline, provides evidence for their alloimmune basis. HLA-DR/DQ molecular mismatch may represent a precise prognostic biomarker that can be applied to tailor immunosuppression or design clinical trials based on individual patient risk.

The effect of ABCB1 polymorphism on sirolimus in renal transplant recipients: a meta-analysis

Background

Sirolimus (SRL) is an immunosuppressive drug and substrate of the P-glycoprotein (P-GP) encoded by ABCB1. The relationship between ABCB1 polymorphism and the pharmacokinetics of SRL in different studies were conflicting in renal transplant recipients. Thus, this meta-analysis aims to investigate the influence of ABCB1 C3435T, C1236T, and G2677T/A polymorphisms on the dose-adjusted trough level (C/D) of SRL in renal transplant recipients.

Methods

PubMed, Embase, and the Cochrane Library were searched for relevant studies. The quality of each eligible study was assessed according to Newcastle-Ottawa Scale. The STATA 15.0 was adopted to perform the meta-analysis. The fixed-effects model was used for pooled results with low heterogeneity (I² ≤50%); otherwise, the random-effects model was used.

Results

A total of 6 studies were included in the meta-analysis. Results of pooled analysis showed no significant association of SRL C/D ratio with ABCB1 C3435T polymorphism. The subgroup analysis based on different ethnic groups and different time-points after SRL initiation in renal transplant recipients were also conducted. No significant association was observed in these subgroups. Significant associations were showed between ABCB1 C1236T polymorphism and the C/D ratio of SRL in the homozygous model (TT vs. CC; WMD: −45.54; 95% CI: −75.15, −15.94; P=0.003), and also in subgroup of Caucasian (TT vs. CC; WMD: −46.57; 95% CI: −91.90, −1.25; P=0.044 and TT vs. CC + CT; WMD: −52.10; 95% CI: −95.38, −8.82; P=0.018). Significant differences were found in association between the ABCB1 G2677T/A polymorphism and the C/D ratio of SRL, including the homozygous model (TT vs. GG; WMD: −76.47; 95% CI: −126.37, −26.58; P= 0.003), the heterozygous model (GT vs. GG,WMD: 178.62; 95% CI: 125.03, 232.22; P= 0.000), the dominant model (GT + TT vs. GG; WMD: 82.23; 95% CI: 36.28, 128.17; P=0.000), the recessive model (TT vs. GG + GT; WMD: −179.38; 95% CI: −283.33, −75.42; P=0.001), and the over-dominant model (GT vs. GG + TT; WMD: 199.44; 95% CI: 84.84, 314.05; P=0.001).

Conclusions

No significant association exists between ABCB1 C3435T polymorphism and the C/D ratio of SRL in renal transplant recipients. To achieve target therapeutic concentrations, ABCB1 C1236T homozygous mutant TT genotype will require a higher dose of sirolimus than wild type GG, especially in Caucasian renal transplant recipients. ABCB1 G2677T/A TT genotype will also need a higher dose of sirolimus genotype. Genotyping of ABCB1 might help to improve the individualization of SRL for renal transplant recipients. Further studies are expected to provide high-quality evidence.

Pharmacodynamic monitoring using biomarkers to individualize pharmacotherapy

Drug doses are often titrated upon their clinical effects (e.g., blood pressure). Unfortunately, for many drugs there is no direct, clinical read-out to estimate dose adequateness. Alternatively, drug dosing is based on the maximum tolerated dose approach or therapeutic drug monitoring. However, the concentration-response curves may be flattened or bell-shaped as suggested for some ‘biologicals’. Together, these aspects raise the question why drug dosing is not individualized by pharmacodynamic monitoring. Evaluating the effects of drugs at their pharmacological target or meaningful biomarkers might indicate nonresponders, objectively quantify the maximum molecular effect and thus restrict overdose and underdosing. This review outlines the theory and biological or technical prerequisites for biomarker-based pharmacodynamic monitoring, and highlights selected examples from different fields of clinical medicine.

Effect of MDR1 C1236T polymorphism on cyclosporine pharmacokinetics: A systematic review and meta-analysis

BACKGROUND

Cyclosporine (CsA) is one of the immunosuppressive drugs, whose pharmacokinetic characteristics vary greatly among individuals. The published data reveal conflicting effects of the polymorphism of MDR1 exon 12 SNP C1236T on the pharmacokinetics of cyclosporine.This study aims to conduct a meta-analysis to investigate the effect of SNP C1236T on the pharmacokinetics of cyclosporine.

METHODS

A literature retrieval was conducted to find the relevant papers in databases including PubMed, Embase, Cochrane Library, China National Knowledge Infrastructure (CNKI), Wan Fang Database (Wan Fang), Chinese Biomedical Literature Database (CBM), VIP Database for Chinese Technical Periodicals (VIP) electronic source for published studies until January 2017. The pharmacokinetic parameters, including C0 (trough blood concentration), C2 (whole-blood levels at 2 hours after drug intake), Cmax (the maximum concentration), and daily dose were extracted and a meta-analysis was performed by RevMan 5.3.

RESULTS

A total of 11 papers concerning 1361 individuals were included in the meta-analysis. As for dose adjusted C0, the results showed difference between subjects carrying CC genotypes and TT genotypes (MD: 6.76, 95% CI [2.38, 11.14], P = .02]. As for C2, the results showed significant difference between subjects carrying CC genotypes and CT genotypes (MD: -18.50, 95% CI [-35.49, -1.52], P = .03), as well as CC genotypes and TT genotypes (MD: -19.01, 95% CI (-35.85, -2.16), P = .03). As for Cmax, daily dose, and C0, the overall results showed no major influence.

CONCLUSIONS

MDR1 C1236T polymorphism may have a minor effect on cyclosporine pharmacokinetics in transplantation patients.

Effectiveness and nephrotoxicity of a 2-year medium dose of cyclosporine in pediatric patients with steroid-dependent nephrotic syndrome: determination of the need for follow-up kidney biopsy

BACKGROUND

High dose of cyclosporine (CyA) for ≥2 years in children with steroid-dependent nephrotic syndrome (SDNS) increases the risk for nephropathy. Considering this, risk can be lowered with lower doses of CyA; we evaluated the effects of a medium dose of CyA, with target serum level, C2, of 450 ng/ml, over a 2-year period of observation, to determine the need for follow-up kidney biopsy.

METHODS

We retrospectively evaluated C2 levels in 38 patients (17 males, 5.2 ± 2.9 years old) with SDNS at treatment initiation, at 6, 12 and 18 months during treatment, and at the time of kidney biopsy, 2-year after treatment initiation. Fifteen patients were also treated with mizoribine or mycophenolate mofetil. A number of relapses-per-patient-per-year, relative to SDNS onset and initiation of CyA treatment, were evaluated. Serum levels of total protein, albumin and total cholesterol, blood urea nitrogen level, and the estimated glomerular filtration rate were measured at treatment initiation and at 1- and 2-year post-treatment initiation.

RESULTS

Only one very mild case of CyA-associated nephrotoxicity was identified based on biopsy results at 2-year post-treatment initiation. C2 concentrations were maintained at 422.2 ± 133.5 ng/ml and the number of relapses decreased from 3.0 relapses-per-patient-per-year prior to CyA treatment to 0.47 relapses-per-patient-per-year after CyA treatment. No effects of the treatment on the estimated glomerular filtration rate were noted.

CONCLUSION

A 2-year treatment with a medium dose of cyclosporine A with or without other immunosuppressive agents is relatively safe with regard to the development of cyclosporine A nephrotoxicity.

Correlation Between Immunosuppressive Therapy and CD4(+) T-Cell Intracellular Adenosine Triphosphate Levels in Liver Transplant Recipients

OBJECTIVE

The aim of this work was to analyze the correlation between immunosuppressive therapy and CD4(+) T-cell intracellular adenosine triphosphate (iATP) levels after liver transplantation and to describe the distribution characteristics of iATP in CD4(+) T cells among liver transplant recipients.

METHODS

We studied 172 patients who were followed regularly after liver transplantation with long-term stable conditions from July 2010 to October 2012. CD4(+) T-cell iATP levels were detected with the use of the Cylex Immuknow Assay method and analyzed retrospectively according to immunosuppressive therapy protocol.

RESULTS

There was a significant difference in CD4(+) T-cell iATP level among the recipients receiving different immunosuppressive therapy protocols after liver transplantation. CD4(+) T-cell iATP level in the FK506 group and FK506 + prednisone (Pred) groups was higher than in the FK506 + mycophenolate mofetil (MMF), FK506 + MMF + Pred, and rapamycin (Rapa) groups. CD4(+) T-cell iATP level in patients receiving an MMF protocol was lower than in the group without MMF.

CONCLUSIONS

There is a relationship between distribution immunosuppressive therapy protocol and CD4(+) T-cell iATP level after liver transplantation. MMF and Rapa lower the CD4(+) T-cell iATP level significantly.

Effects of oral cyclosporine on canine T-cell expression of IL-2 and IFN-gamma across a 12-h dosing interval

The duration of immunosuppressive effects following oral cyclosporine in dogs is unknown. This study used flow cytometry and quantitative reverse transcription-polymerase chain reaction (qRT-PCR) to evaluate the effects of high-dose oral cyclosporine across a 12-h dosing interval. Expression of interleukin-2 (IL-2) and interferon-gamma (IFN-γ) was compared before and after 8 days of cyclosporine at 10 mg/kg every 12 h in six healthy dogs. Samples were collected at 0, 2, 4, and 8 h postdosing for analysis of unactivated and activated T-cell and whole blood cytokine expression using flow cytometry and qRT-PCR, respectively, and at 0, 2, 4, 6, 8, and 10 h postdosing for measurement of cyclosporine concentrations. Flow cytometry and qRT-PCR both demonstrated significant marked reductions in IL-2 and IFN-γ levels at 0, 2, 4, and 8 h after dosing compared to pretreatment levels (P < 0.05) for activated samples, with less consistent effects observed for unactivated samples. Both flow cytometry and qRT-PCR are viable techniques for measuring cyclosporine pharmacodynamics in dogs, yielding comparable results with activated samples. Two hours postdrug administration is the preferred time for concurrent assessment of peak drug concentration and cytokine expression, and T-cell activation is needed for optimal results.

Limited sampling strategies for estimating intravenous and oral cyclosporine area under the curve in pediatric hematopoietic stem cell transplantation

BACKGROUND

The optimal monitoring strategy for cyclosporine (CsA) in pediatric hematopoietic stem cell transplantation (HSCT) patients remains unclear. Although there is a growing interest in the use of the area under the concentration-time curve (AUC), measurement of AUC in clinical settings is often impractical. The objective of this study was to identify and validate limited sampling strategies (LSSs) for the prediction of CsA AUC after intravenous (IV) and oral (PO) administration in this population.

METHODS

Sixty-eight pediatric patients who underwent HSCT and received CsA were investigated. Twelve-hour pharmacokinetic profiles (n = 138) performed per standard of care were collected. Weighted multiple linear regression was used to investigate all possible LSSs consisting of 4 or less concentration-time points. Their predictive performance was evaluated by leave one out cross validation and external validation by measuring the root mean squared relative error (RMSE%) and the 95th percentile of the absolute relative error (AE%). Values less than 20% were considered clinically acceptable.

RESULTS

Nine LSSs (4 IV and 5 PO) convenient for clinical application proved to have clinically acceptable performance. Notably, LSS based on C0, C2, and C4 was found to be accurate for estimation of CsA exposure after both IV and PO administration with the 95th percentile of AE% of 19.7% and 17.5%, respectively.

CONCLUSIONS

LSSs using 3 or 4 concentration-time points obtained within 4 hours postdose provide a convenient and reliable method to estimate CsA exposure in this population. These LSSs may facilitate future research aiming at better defining the relationship between AUC and clinical outcomes.

Cyclosporine use in hematopoietic stem cell transplantation: pharmacokinetic approach

Cyclosporine is one of the most vital agents in the process of successful allogeneic hematopoietic stem cell transplantation. Despite a long history and worldwide extent of cyclosporine use for prevention of graft versus host disease, currently there are lots of uncertainties about its optimal method of application to reach the best clinical outcome. A major portion of this problem stems from complicated cyclosporine pharmacokinetics. Study of cyclosporine pharmacokinetic behavior can significantly help recognition of its effectiveness and consequently, optimization of dosing, administration, monitoring and management of adverse effects. In this review, highly accredited but sparse scientific data are gathered in order to provide a better insight for preparation of practice guidelines and directing future studies for allogeneic hematopoietic cell recipients.

Impact of sampling time deviations on the prediction of the area under the curve using regression limited sampling strategies

The regression limited sampling strategy approach (R-LSS), which is based on a small number of blood samples drawn at selected time points, has been used as an alternative method for the estimation of the area under the concentration-time curve (AUC). However, deviations from planned sampling times may affect the performance of R-LSS, influencing related therapeutic decisions and outcomes. The aim of this study was to investigate the impact of different sampling time deviation (STD) scenarios on the estimation of AUC by the R-LSS using a simulation approach. Three types of scenarios were considered going from the simplest case of fixed deviations, to random deviations and then to a more realistic case where deviations of mixed nature can occur. In addition, the sensitivity of the R-LSS to STD in each involved sampling point was evaluated. A significant impact of STD on the performance of R-LSS was demonstrated. The tolerance of R-LSS to STD was found to depend not only on the number of sampling points but more importantly on the duration of the sampling process. Sensitivity analysis showed that sampling points at which rapid concentration changes occur were relatively more critical for AUC prediction by R-LSS. As a practical approach, nomograms were proposed, where the expected predictive performance of R-LSS was provided as a function of STD information. The investigation of STD impact on the predictive performance of R-LSS is a critical element and should be routinely performed to guide R-LSS selection and use.

Relationship between pharmacokinetics and pharmacodynamics of calcineurin inhibitors in renal transplant patients

The calcineurin inhibitors (CNIs) cyclosporine A (CsA) and tacrolimus (Tac) are immunosuppressive drugs, which are typically employed in the field of organ transplantation. Both drugs have narrow therapeutic indices, highly variable pharmacokinetics, and are associated with severe adverse effects. In current clinical routine, the dose finding of CNIs is based on the measurement of their blood concentrations. However, this method is limited in its ability to determine the biological impact of the drug. Alternative monitoring strategies, focusing on the pharmacodynamics of CNIs, could help to personalize drug dosing and optimize the treatment with CNIs. Therefore, we analyzed the relationship between pharmacokinetic and pharmacodynamic of the CNIs CsA (n = 9) and Tac (n = 8) in stable renal transplant patients during a 12-h dosing period. We observed a significant decrease in the drug-blood concentration during the course of the day and in parallel a significant recovery of T cell function. In addition, our data document that analysis of intracellular interleukin (IL)-2 production and determination of the IL-2 release are accurate parameters for monitoring the pharmacodynamics of CNIs.

Therapeutic drug monitoring in pediatric renal transplantation

Finding the balance between clinical efficacy and toxicity of immunosuppressive drugs is a challenge in renal transplantation (RTx), but especially in pediatric RTx patients. Due to the expected longer life-span of pediatric transplant patients and the long-term consequences of drug-induced infectious, malignant and cardiovascular adverse effects, protocols which minimize immunosuppressive therapy make conceptual sense. In this context, therapeutic drug monitoring is a tool which provides support for the individualization of therapy. It has, however, limitations, and specific data in the pediatric cohort are comparatively sparse. There is large heterogeneity among the studies conducted to date in terms of methods, follow-up, endpoints, immunosuppressive regimens and patients. In addition, data from adult studies are not readily transferrable to the pediatric situation. This educational review gives a concise overview on aspects of therapeutic drug monitoring in pediatric RTx.

Early non-steady-state population pharmacokinetics of oral cyclosporine in renal transplant recipients

This study aimed to evaluate the change in the pharmacokinetics (PK) of cyclosporine in the non-steady-state period in the first week after renal transplantation; the factors influencing this change, including genetic variability; and the time point concentration that correlated best with drug exposure. Data were obtained from 69 patients, and PK studies were conducted on postoperative days (PODs) 2, 3, and 7. Samples were taken pre-dose and at 1, 2, 3, 4, 6, 8, and 12 hours after drug administration. MDR1, CYP3A4, and CYP3A5 were genotyped. A population PK analysis and correlational analysis between the concentration at each time point and the area under the time-concentration curve were performed. A two-compartment model with first-order absorption was chosen. The rate and extent of drug absorption showed a significant increase on POD3, followed by a slight decrease on POD7. Until POD3, 8 hours post-dose was the single time point concentration that correlated best with drug exposure and 3 hours was the best time point on POD7. In both analyses, the MDR1 genotype showed potential as a factor influencing PK change. We conclude that oral administration of cyclosporine and dose adjustment based on a single concentration measurement might result in unexpected drug exposure during this early posttransplantation period.

Bayesian approach for the estimation of cyclosporine area under the curve using limited sampling strategies in pediatric hematopoietic stem cell transplantation

BACKGROUND

The optimal marker for cyclosporine (CsA) monitoring in transplantation patients remains controversial. However, there is a growing interest in the use of the area under the concentration-time curve (AUC), particularly for cyclosporine dose adjustment in pediatric hematopoietic stem cell transplantation. In this paper, we develop Bayesian limited sampling strategies (B-LSS) for cyclosporine AUC estimation using population pharmacokinetic (Pop-PK) models and investigate related issues, with the aim to improve B-LSS prediction performance.

METHODS

Twenty five pediatric hematopoietic stem cell transplantation patients receiving intravenous and oral cyclosporine were investigated. Pop-PK analyses were carried out and the predictive performance of B-LSS was evaluated using the final Pop-PK model and several related ones. The performance of B-LSS when targeting different versions of AUC was also discussed.

RESULTS

A two-compartment structure model with a lag time and a combined additive and proportional error is retained. The final covariate model does not improve the B-LSS prediction performance. The best performing models for intravenous and oral cyclosporine are the structure ones with combined and additive error, respectively. Twelve B-LSS, consisting of 4 or less sampling points obtained within 4 hours post-dose, predict AUC with 95th percentile of the absolute values of relative prediction errors of 20% or less. Moreover, B-LSS perform better for the prediction of the 'underlying' AUC derived from the Pop-PK model estimated concentrations that exclude the residual errors, in comparison to their prediction of the observed AUC directly calculated using measured concentrations.

CONCLUSIONS

B-LSS can adequately estimate cyclosporine AUC. However, B-LSS performance is not perfectly in line with the standard Pop-PK model selection criteria; hence the final model might not be ideal for AUC prediction purpose. Therefore, for B-LSS application, Pop-PK model diagnostic criteria should additionally account for AUC prediction errors.

Immune cell function assay does not identify biopsy-proven pediatric renal allograft rejection or infection

Management of pediatric renal transplant patients involves multifactorial monitoring modalities to ensure allograft survival and prevent opportunistic infection secondary to immunosuppression. An ICFA, which utilizes CD4 T-cell production of ATP to assess immune system status, has been used to monitor transplant recipients and predict susceptibility of patients to rejection or infection. However, the validity of this assay to reflect immune status remains unanswered. In a two-yr retrospective study that included 31 pediatric renal transplant recipients, 42 patient blood samples were analyzed for immune cell function levels, creatinine, WBC (white blood cell) count, immunosuppressive drug levels, and viremia, concurrent with renal biopsy. T-cell ATP production as assessed by ICFA levels did not correlate with allograft rejection or with the presence or absence of viremia. ICFA levels did not correlate with serum creatinine or immunosuppressive drug levels, but did correlate with WBC count. The ICFA is unreliable in its ability to reflect immune system status in pediatric renal transplantation. Further investigation is necessary to develop methods that will accurately predict susceptibility of pediatric renal transplant recipients to allograft rejection and infection.

High intra-individual variability of cyclosporine pharmacokinetics in lung transplant recipients without cystic fibrosis

BACKGROUND

There has been little study on the variability of CsA pharmacokinetics in stable lung transplant (LT) recipients without cystic fibrosis. This study was conducted to determine the prevalence of high intra-individual variability of CsA in LT recipients and its implications in CsA monitoring.

METHODS

Twenty-nine pharmacokinetic curves were performed in 10 consecutive stable patients from a single center. The intra-individual coefficient of variation (CV) of the AUC₀₋₁₂ h was calculated in each case. Patients were grouped according to whether their CV was high (≥20%) or low (<20%). Correlations between cyclosporine CsA concentration at each time point, AUC₀₋₄ h , and AUC₀₋₁₂ h were also calculated.

RESULTS

Six (60%) patients presented low CVs and four (40%) high CVs. In patients with low CVs, the best correlation of AUC₀₋₁₂ h was with CsA concentration at two h post-dose (C₂) (r = 0.674, p = 0.002), whereas in those with high CV, the best correlation was with C5 (r = 0.800, p = 0.003). In the latter group, the correlation with C₂ was low (r = 0.327, p = 0.32), whereas the correlation with C₀ was high (r = 0.709, p < 0.05).

CONCLUSIONS

Intra-individual variability of CsA pharmacokinetics may be high in many LT recipients. In patients with high CV, the use of C₀ levels may be more appropriate for CsA monitoring than C₂ levels.

Correlations between cyclosporine concentrations at 2 hours post-dose and trough levels with functional outcomes in de novo lung transplant recipients

BACKGROUND

Although the reliability of cyclosporine (CyA) concentration at 2 (C2) hours postdosing has been established for kidney, liver, and heart transplant recipients, its use in lung cases remains to be validated. We investigated the relationship between CyA dual time point monitoring and long-term functional outcomes after lung transplantation.

METHODS

We included data from 38 lung transplant recipients receiving CyA, azathioprins, and steroids in the study. CyA dosages were based on the trough concentrations. CyA concentrations at 0 (C0) and 2 (C2) hours postdosing were obtained at 1, 2, 3, 6, 9, 12, 15, 18, and 24 months postoperative. We retrospectively compared average CyA level (C0 and C2) during the first 3 posttransplantation months with forced expiratory volume in 1 second (FEV1), forced vital capacity (FVC), forced expiratory flow 25%-75 % (FEF 25-75), creatinine, systolic blood pressure (SBP), and diastolic blood pressure (DBP) using regression analysis via generalized estimating equations (GEE).

RESULTS

Only improvement in FVC (P = .033) and deterioration of SBP (P < .001) were related to C0 monitoring. No correlation was observed between C0 and FEV1 (P = .13), FEF 25-75 (P = .48), creatinine (P = .07), and DBP (P = .97). Nor was any relationship observed between C2 concentrations and FEV1 (P = .64), FVC (P = .38), FEF 25-75 (P = .09), creatinine (P = .95), SBP (P = .73), or DBP (P = .51).

CONCLUSION

There was a lack of a relationship between CyA concentrations (C0 and C2) and functional outcomes among de novo lung transplantations except for a positive correlation of 0 value with long-term improved FVC and increased SBP. This study suggested that C2 determinations may not improving lung recipient management.

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.

Comparison of architect I 2000 for determination of cyclosporine with axsym

BACKGROUND

Cyclosporine has been shown effective drug in suppressing acute rejection in recipients of allograft organ transplants.

METHODS

The cyclosporine concentration of 96 blood samples was determined using CMIA (chemiluminesecent microparticle immnoassay) Architect i 2000 and FPIA (fluorescence polarization immunoassay) AxSYM Abbott diagnostic. All patients have transplantation of kidneys and were hospitalized at Department of Nephrology at the Clinical center of University of Sarajevo. The reference serum range of cyclosporine for kidney organ transplantation for maintenance lies between 50 and 150 ng/mL. The quality control, precision and accurancy of Architect i 2000 were assessed.

RESULTS

The quality control was done using quality control serums for low (= 91 ng/mL), medium (= 328 ng/mL) and high (= 829 ng/mL). We have used commercial BIORAD controls and got reproducibility CV 5.83 % to 13 % for Architect i 2000. It was established that the main difference between Architect i 2000 and AxSYM and it was statistically significant for P < 0.05 according to Student t-test. Correlation coefficient was r = 0.903.

CONCLUSION

The CMIA Architect assay has significant reduced cyclosporine metabolite interference relative to other immunoassay and is a convenient and sensitive automated method to measure cyclosporine in whole blood.

Acute effects of calcineurin inhibitors on kidney allograft microperfusion visualized by contrast-enhanced sonography

BACKGROUND

Calcineurin inhibitors induce detrimental vascular remodeling, which may be one cause of chronic allograft failure. Real-time contrast-enhanced sonography (CES) is a relatively new technique in providing quantitative information on microvascular tissue perfusion in kidney allografts in more detail. The purpose of the study was to explore whether acute changes of kidney allograft microperfusion due to the administration of cyclosporine A (CsA) and tacrolimus (Tac) can be evidenced using real-time CES.

METHODS

In an explorative single-center clinical trial, renal parenchymal tissue perfusion of 32 stable kidney allograft recipients was evaluated with CES before and 2 hr after the intake of CsA or Tac. In addition to laboratory and clinical parameters, Doppler indices and estimated glomerular filtration rate were measured.

RESULTS

Although systolic and diastolic blood pressure and color Doppler indices did not significantly differ, there was a significant decrease of renal blood flow 2 hr after the intake of CsA compared with baseline (4.78±2.31 dB/s, 49%, respectively). In contrast, kidney allograft microperfusion was neither significantly reduced in patients receiving CsA paralleled by calcium channel blockers nor significantly reduced in patients receiving Tac. Furthermore, there was a significant correlation between renal blood flow obtained before drug administration and kidney function.

CONCLUSIONS

CES revealed a 49% reduction of kidney allograft microperfusion 2 hr after the intake of CsA, which might be abrogated by calcium channel blockers. In comparison to CsA, Tac did not result in a significant decrease of kidney blood flow.

Population pharmacokinetics of ciclosporin in haematopoietic allogeneic stem cell transplantation with emphasis on limited sampling strategy

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT • The population pharmacokinetics and limited sampling strategies for ciclosporin monitoring have been extensively studied in renal and liver transplant recipients. Little is known about the pharmacokinetics of ciclosporin in patients undergoing haematopoietic allogeneic stem cell transplantation (HSCT). • It is anticipated that there is a difference in pharmacokinetics in patients after kidney or liver transplantation compared with patients undergoing stem cell transplantation, because of mucositis and interacting drugs (e.g. fluconazole). • Data on the pharmacokinetics of ciclosporin and the relationship between its systemic exposure, as reflected by the area under the curve (AUC), and the biological effect as graft vs. host-disease (GVHD) prophylaxis and graft vs. tumour (GVT) response are scarce in patients after HSCT. WHAT THIS STUDY ADDS • A pharmacokinetic model was developed for orally and intravenously administered ciclosporin, enabling an adequate estimate of the systemic exposure of ciclosporin in patients after HSCT. A limited sampling strategy was tested that may serve as a tool to study the optimum systemic exposure (AUC) of ciclosporin in HSCT to prevent GVHD but establish adequate GVT response and to guide therapeutic drug monitoring. AIM To develop a population pharmacokinetic model of ciclosporin (CsA) in haematopoietic allogeneic stem cell transplantation to facilitate a limited sampling strategy to determine systemic exposure (area under the curve [AUC]), in order to optimize CsA therapy in this patient population. METHODS The pharmacokinetics of CsA were investigated prospectively in 20 patients following allogeneic haematopoietic stem cell transplantation (HSCT). CsA was given twice daily, as a 3 h i.v. infusion starting at day 1 of the conditioning scheme, and orally later on, when oral intake was well tolerated. Fluconazole was given as antimycotic prophylaxis. Pharmacokinetic parameter estimation was performed using nonlinear mixed effect modelling as implemented in the NONMEM program. A first order absorption model with lag time was compared with Erlang frequency distribution and Weibull distribution models. The influence of demographic variables on the individual empirical Bayesian estimates of clearance and distribution volume was tested. Subsequently two limited sampling strategies (LSS) were evaluated: posterior Bayesian fitting and limited sampling equations. RESULTS Twenty patients were included and 435 samples were collected after i.v. and oral administration of CsA. A two compartment model with first order absorption best described the data. Clearance (CL) was 21.9 l h(-1) (relative standard deviation [RSD]± 5.2%) with an inter-individual variability of 21%. The central volume of distribution (V(c) ) was 18.3 l (RSD ± 8.7%) with an inter-individual variability of 29%. Bioavailability (F) was 0.71 (RSD ± 9.9%) with and inter-individual variability of 25% and lag time (t(lag) ) was 0.44 h (RSD 5.5%). Weight, body surface area, haematocrit, albumin, ALAT and ASAT had no significant influence on pharmacokinetic parameters. The best multiple point combination for posterior Bayesian fitting, in terms of estimating systemic CsA exposure, appeared to be C0 + C2 + C3. Two selected LSS two time point equations and all selected three and four time point equations predicted de all AUC(0,12 h) within 15% bias and prediction. CONCLUSIONS The i.v. and oralcurves were best described with a two compartment model with first-order absorption with lag time. With the Bayesian estimators from this model, the area under the concentration-time curve in HSCT patients taking fluconazole can be estimated with only three blood samples (0, 2, 3 h) with a bias of 1% and precision of 4%.

Safety and efficacy of generic cyclosporine arpimune in Filipino low-risk primary kidney transplant recipients

BACKGROUND

In the Philippines, maintenance of immunosuppression may not always be affordable, leading to acute rejection and graft loss. The availability of the generic cyclosporine Arpimune could be economically beneficial, but its safety and efficacy should be established.

METHODS

This prospective cohort study enrolled 30 renal transplant patients who received Arpimune with mycophenolate/prednisone. Their results were compared up to 6 months with 30 matched control patients who received Neoral during the same period. Areas under the receiver operating characteristic curves (AUC) after intake of Arpimune and therapeutic drug monitoring using cyclosporine levels 2 hours after each dose were done. Pearson correlation was performed to determine linearity of relationship between the generic cyclosporine concentrations and AUC 0-4. Chi-square test was used in obtaining cyclosporine Arpimune concentrations.

RESULTS

The abbreviated concentration AUC of Arpimune was similar to that of Neoral, and the 2-hour sampling point (r = 0.813; P < .001) showed the best correlation. Calculated creatinine clearance (mL/min) versus Neoral was 71.36 ± 13 versus 68.03 ± 16.6 (P = .61) at 1 month, 70.4 ± 14.8 versus 64.2 ± 11.4 (P = .12) at 3 months, and 74.02 ± 15.8 versus 62.03 ± 12.1 (P = .002) at 6 months. Two Arpimune versus 4 Neoral patients (P = .67) developed biopsy-proven acute rejection. One septic death occurred in the Arpimune group. Graft survival was 100% in both groups. Hyperlipidemia was the most frequent side effect for both.

CONCLUSIONS

The AUC of Arpimune was similar to that of Neoral. Use of the generic cyclosporine Arpimune provided effective immunosuppression in the 6 months after transplantation. Renal allograft function was similar to that of Neoral, with minimal rates of acute rejection and adverse events.

Genetic and clinical determinants of early, acute calcineurin inhibitor-related nephrotoxicity: results from a kidney transplant consortium

BACKGROUND

Calcineurin inhibitor (CNI)-related acute nephrotoxicity is a common complication of transplantation. Clinical factors and elevated CNI levels are associated with nephrotoxicity; however, they do not fully explain the risk. Genetic factors may also predispose individuals to nephrotoxicity.

METHODS

We enrolled 945 kidney recipients into a multicenter, prospective study. DNA was genotyped for 2724 single-nucleotide polymorphisms (SNPs) using a customized chip. Cox models, unadjusted and adjusted for clinical factors, examined the association between SNPs and time to early CNI-related acute nephrotoxicity in the first 6 months posttransplant.

RESULTS

Cyclosporine was associated with a 1.49 hazard (95% confidence interval, 1.04-2.14) of acute nephrotoxicity relative to tacrolimus. Acute nephrotoxicity occurred in 22.6% of cyclosporine and 19.8% of tacrolimus recipients. The median (interquartile range) daily dose and trough concentration at time of nephrotoxicity were 400 mg (400-500 mg) and 228 ng/mL (190-272 ng/mL) in the cyclosporine group, and 6 mg (4-8 mg) and 12.6 ng/mL (10.2-15.9 ng/mL) in the tacrolimus group, respectively. In single-SNP adjusted analysis, nine SNPs in the XPC, CYP2C9, PAX4, MTRR, and GAN genes were associated with cyclosporine nephrotoxicity. In a multi-SNP analysis, SNPs from the same genes remained significant after adjusting for the clinical factors, showing that the SNPs are jointly and independently predictive of cyclosporine nephrotoxicity. No SNPs were associated with tacrolimus nephrotoxicity.

CONCLUSION

We identified SNPs that were potentially associated with early, acute cyclosporine-related nephrotoxicity. Identifying risk SNPs before transplantation provides an opportunity for personalization of immunosuppression by identifying those who may benefit from CNI-avoidance or minimization, or assist in selecting CNI type. These SNPs require independent validation.

Age effect on whole blood cyclosporine concentrations following oral administration in children with nephrotic syndrome

The aim of this study was to investigate age-related pharmacokinetic differences of cyclosporine (CyA) in children with nephrotic syndrome. Whole blood concentrations of CyA were monitored for a total of 96 times in 36 cases. The 25 male and 11 female patients ranged in age from 1.9 to 19.7 years with a mean age of 9.1 years. Renal biopsy showed minimal change in 33 patients and focal segmental glomerulosclerosis in three patients. CyA was orally administered in two divided doses just before meals. The doses of CyA administered were adjusted such that the target value for blood concentration at 2 h post-dose (C2) was 400-450 ng/ml. The 96 subjects were divided into three groups according to age: group I, 1-5 years (n = 30); group II, 6-10 years (n = 34); and group III, ≥ 11 years (n = 32). In all subjects, peak levels (Cmax) of CyA were reached at C1 or C2. There was no significant difference between the groups for C2, area under the whole blood concentration-time curve up to 4 h post-dose (AUC0-4), and Cmax. The mean CyA doses of groups I, II, and III were 4.8 ± 1.0 mg/kg/day, 3.8 ± 0.9 mg/kg/day, and 3.0 ± 0.6 mg/kg/day, respectively, and there were significant differences between every two groups. In addition, the dose-normalized Cmax (Cmax/dose) and AUC0-4 (AUC0-4/dose) values were significantly lower in the younger group than in the older group. These findings suggested that in children, when the same concentration is targeted, the required CyA dose would vary according to age but would be significantly higher for the younger children.

Trends in immune function assay (ImmuKnow; Cylex™) results in the first year post-transplant and relationship to BK virus infection

BACKGROUND

The ImmuKnow assay is a functional T-cell assay (TCA) that may quantify cellular immune responsiveness following renal transplantation. Using a standard protocol of TCA sampling in the first year post-transplant, we examined changes in TCA values over time and tested for an association between TCA and BK virus (BKV) infection as a marker of over-immunosuppression.

METHODS

We performed a single-center retrospective analysis of 897 TCA results in 414 renal transplant recipients obtained at 0 (N = 122), 1 (N = 316), 6 (N = 258) and 12 (N = 201) months post-transplant from May 2005 to July 2009 with concurrent urine and blood BKV polymerase chain reaction measurements.

RESULTS

Nearly 40% of patients experienced a decrease in TCA of >150 ng/mL from 1 to 6 months (mean 466-356 ng/mL, P < 0.0001) and remained stable from 6 to 12 months (mean 357 versus 370 ng/mL, P = 0.33). Neither a change in TCA of >150 ng/mL nor a TCA value of ≤ 225 ng/mL were associated with a diagnosis of BKV infection at 1 or 6 months, while TCA ≤ 225 ng/mL was associated with BKV infection at 12 months (P = 0.005).

CONCLUSIONS

A reduction in TCA from 1 to 6 months post-transplant is common and is not associated with conditions of over-immunosuppression, rendering the interpretation of changes in TCA during this time period difficult. BKV infection is associated with low TCA values at 12 months, suggesting that patients with low TCA values after 6 months may benefit from potential tailoring of immunosuppression or more aggressive monitoring to prevent subsequent BKV infection.

Routine Cyclosporine concentration - C2 level Monitoring. Is it helpful during the early post Transplant Period?

BACKGROUND

Pre dose or trough blood cyclosporine (CSA) concentration is routinely monitored and the result is used to alter patient's drug dosing. Patients with identical pre dose blood CSA may have very different systemic exposure to the drug. Recently CSA 2 hour post dose level [C2] has been reported to correlate better with drug exposure. We undertook this study to evaluate the influence of trough and C2, CSA concentration monitoring on short-term renal allograft outcomes.

METHODS

25 patients of renal transplant receiving a triple drug regimen of CSA micro emulsion (Panacea Biotec) 8mg/kg, azathioprine 1mg/kg and prednisolone 0.5mg/kg were analyzed prospectively for graft outcomes. CSA levels were monitored in whole blood by radioimmunoassay using monoclonal antibodies, at 72 hours after the transplant.

RESULTS

The mean age of patients was 37.08 + 9.1 years. There were 20 males and 5 females. The mean age of donors was 40.2 + 8.2 years. There were 11 related donors with at least a haplomatch, 4 spousal and 10 unrelated donors with a nil antigen match. The mean pre dose CSA concentration was 289.22 + 171.9ng/ml; range (98.8 + 783.41ng/ml). The CSA concentration at 2 hours after the CSA administration was 838 + 310.87ng/ml (range, 169 + 1268ng/ml). 3 (12%) patients had acute rejection. In these patients the mean pre dose CSA concentration was 328.67ng/ml and the mean C2, CSA concentration was 1006.26ng/ml. CSA induced hemolytic uraemic syndrome was diagnosed in one patient. The trough and C2, CSA concentration levels were 174 and 870.83ng/ml respectively in this patient.

CONCLUSION

In our study CSA levels, trough and peak showed significant inter patient variability. The trough and C2 concentration levels did not correlate with the episodes of acute rejection. We conclude that in a triple drug regimen with fixed dosing schedules routine trough CSA level monitoring is not helpful in the acute post renal transplant period.

Effects of the CYP3A5*3 variant on cyclosporine exposure and acute rejection rate in renal transplant patients: a meta-analysis

BACKGROUND

Whether the loss-of-function allele CYP3A5*3 variant is associated with significantly impaired metabolism of cyclosporine A (CsA) in transplant patients is still controversial because of the lack of prospective, large-scale clinical studies performed among diversely ethnic populations.

OBJECTIVES

This meta-analysis was designed to determine whether the CYP3A5*3 variant could affect CsA blood concentrations and the rate of acute rejection in renal transplant recipients.

METHODS AND RESULTS

All relevant publications were retrieved online from 1966 to March 2010, in which 14 studies were chosen, and 1821 renal transplant patients were enrolled. The results showed that there were significant differences in the CsA dose-adjusted trough concentration (C0) between the CYP3A5*3/*3 and CYP3A5*1/*1 carriers [weighted mean difference (WMD): 10.06 mug/l per mg/kg, 95% confidence interval (CI): 3.12-17.00, P=0.004] and between the non-CYP3A5*1 allele carriers and the CYP3A5*1 allele carriers (WMD: 8.32 mug/l per mg/kg, 95% CI: 3.16-13.49, P=0.002). In addition, a subgroup analysis stratified by ethnicity indicated that a significant difference in CsA dose-adjusted C0 was observed between the non-CYP3A5*1 allele carriers and the CYP3A5*1 allele carriers in Asian patients, but not in Caucasian patients. Moreover, a significant difference in the mean daily dose was observed between the non-CYP3A5*1 allele carriers and the CYP3A5*1 allele carriers (WMD: -0.19 mg/kg, 95% CI: -0.31 to -0.07, P=0.002). However, the meta-analysis suggested that there was little or no association of the CYP3A5*3 variant with the acute rejection rate in renal transplant patients treated with CsA [odds ratio=0.94, 95% CI: 0.57-1.54, P=0.80].

CONCLUSION

We concluded that the CYP3A5*3 variant could be associated, to a certain extent, with increased CsA dose-adjusted C0 in blood and reduced mean daily doses, but that this genetic variant allele seemed to have little effect on the acute rejection rate in renal transplant patients taking CsA.

Toxicodynamic effects of ciclosporin are reflected by metabolite profiles in the urine of healthy individuals after a single dose

WHAT IS ALREADY KNOWN ABOUT THE SUBJECT * Ciclosporin's nephrotoxicity initially targets the proximal tubule and is, at least in part, driven by increased formation of oxygen radicals. * (1)H-nuclear magnetic resonance spectroscopy (NMR)- and mass spectrometry (MS)-based biochemical profiling (metabolomics) allows for the sensitive detection of metabolite pattern changes in urine. * In systematic studies in rats we showed that ciclosporin caused urine metabolite pattern changes typical for proximal tubule damage and that these pattern changes seemed to be more sensitive than established clinical kidney function markers such as serum creatinine concentrations. WHAT THIS PAPER ADDS * This study showed that urine metabolite pattern changes as assessed by (1)H-NMR and HPLC-MS are sensitive enough to detect the effect of ciclosporin as early as 4 h after a single oral dose. * In our previous rat studies, changes in urine metabolite pattern in response to ciclosporin translated into healthy humans, indicating the involvement of the same toxicodynamic mechanisms. * The results provide proof of concept for further development of this combination molecular marker strategy into diagnostic tools for the detection and monitoring of drug nephrotoxicity. AIMS The immunosuppressant ciclosporin is an efficient prophylaxis against transplant organ rejection but its clinical use is limited by its nephrotoxicity. Our previous systematic studies in the rat indicated urine metabolite pattern changes to be sensitive indicators of the negative effects of ciclosporin on the kidney. To translate these results, we conducted an open label, placebo-controlled, crossover study assessing the time-dependent toxicodynamic effects of a single oral ciclosporin dose (5 mg kg(-1)) on the kidney in 13 healthy individuals. METHODS In plasma and urine samples, ciclosporin and 15-F(2t)-isoprostane concentrations were assessed using HPLC-MS and metabolite profiles using (1)H-NMR spectroscopy. RESULTS The maximum ciclosporin concentrations were 1489 +/- 425 ng ml(-1) (blood) and 2629 +/- 1308 ng ml(-1) (urine). The increase in urinary 15-F(2t)-isoprostane observed 4 h after administration of ciclosporin indicated an increase in oxidative stress. 15-F(2t)-isoprostane concentrations were on average 2.9-fold higher after ciclosporin than after placebo (59.8 +/- 31.2 vs. 20.9 +/- 19.9 pg mg(-1) creatinine, P < 0.02). While there were no conclusive changes in plasma 15-F(2t)-isoprostane concentrations or metabolite patterns, non-targeted metabolome analysis using principal components analysis and partial least square fit analysis revealed significant changes in urine metabolites typically associated with negative effects on proximal tubule cells. The major metabolites that differed between the 4 h urine samples after ciclosporin and placebo were citrate, hippurate, lactate, TMAO, creatinine and phenylalanine. CONCLUSION Changes in urine metabolite patterns as a molecular marker are sufficiently sensitive for the detection of the negative effects of ciclosporin on the kidney after a single oral dose.

Triple therapy with single daily dose of cyclosporine in Japanese patients with idiopathic membranous nephropathy

OBJECTIVE

The optimal therapeutic approach to patients with idiopathic membranous nephropathy (IMN) remains controversial. In this study, we assessed the efficacy of single daily dose cyclosporine (CsA) combined with low-dose prednisolone (PSL) and an angiotensin II receptor blocker (ARB) in patients with IMN.

METHODS

We studied 13 nephrotic patients (8 men, 5 women) with IMN diagnosed on biopsy. An initial single daily dose of 2 mg/kg, but not exceeding 150 mg, CsA was given for 12 months, tapered by a 25 mg reduction every 2 months. An initial twice-daily dose of 0.5 mg/kg PSL was given for 2 months and was also tapered. An ARB was given to all patients and the same dosage was used throughout the study. Patients were followed up for 6 to 66 months.

RESULTS

Nine patients achieved complete remission at 6.7±2.9 months, and incomplete remission was obtained in the remaining patients. After a follow-up period of 32.7±20.0 months, their serum creatinine and estimated glomerular filtration rate values were similar to baseline levels. The 9 patients who completed the treatment course have not relapsed. Moreover, there were no adverse effects requiring discontinuation of this triple therapy.

CONCLUSION

A single daily dose of CsA combined with a low dose of PSL and an ARB in new-onset nephrotic patients with IMN induced a high remission rate of nephrotic syndrome, with a low incidence of relapse and a low risk of adverse effects. The triple therapy and prospective follow-up shows potential as a treatment approach for patients with IMN.

The immunosuppressive pipeline: meeting unmet needs in liver transplantation

Liver transplantation is now recognized as the treatment of choice for end-stage liver failure. Its success can be attributed largely to the generation of selective immunosuppressive agents, which have resulted in a dramatic reduction in the incidence of acute rejection and improvements in the short- and long-term outcomes of patients. However, the unresolved limitation of current immunosuppressive agents is long-term toxicity, which results in increases in the incidence and severity of cardiovascular, neurological, and renal diseases. Our recent understanding of the pathways of cell activation has resulted in the development of a new generation of immunosuppressive agents that may address the challenges facing transplantation today and allow the minimization or substitution of existing agents. Furthermore, advances in our understanding of the mechanisms of tolerance and the identification of biomarker signatures hold the promise that in some patients transplantation may be able to be performed without the need for long-term immunosuppression (tolerance).

Single time point immune function assay (ImmuKnow) testing does not aid in the prediction of future opportunistic infections or acute rejection

BACKGROUND AND OBJECTIVES

Current assays and tests that are used to determine the degree of immunosuppression in renal transplant recipients are suboptimal. The ImmuKnow assay (Cylex), a measure of intracellular CD4+ T cell ATP release proposed as a means to quantify cell-mediated immunity in transplant recipients, could be considered as a potential tool to identify patients at risk for opportunistic infections (OI) or acute rejection (AR).

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We retrospectively analyzed 1330 ImmuKnow assay values in 583 renal transplant recipients at a single center from 2004 to 2009 and correlated these values with episodes of OI and AR in the subsequent 90 days. Assay values were compared with a control population matched for age, gender, and time post-transplantation.

RESULTS

In patients with OI (n=94), there were no differences in prior mean assay values compared with matched controls (386 versus 417 ng/ml, P=0.24). In 47 patients with AR, again no differences were detected in prior assay results (390 versus 432 ng/ml, P=0.25) when compared with controls. "Low" values (≤225 ng/ml) lacked sensitivity and specificity as a predictive test for subsequent OI, as did "strong" (≥525 ng/ml) values as a predictive test for subsequent AR.

CONCLUSIONS

Our results fail to show an association between single time point ImmuKnow assay values and the subsequent development of an adverse event in the subsequent 90 days. The optimal use of the ImmuKnow assay in kidney transplantation has yet to be determined.