Measurement of Cyclosporine A in Rat Tissues and Human Kidney Transplant Biopsies—A Method Suitable for Small (<1 mg) Samples

Blood, Cellular, and Tissular Calcineurin Inhibitors Pharmacokinetic-Pharmacodynamic Relationship in Heart Transplant Recipients: The INTRACAR Study

BACKGROUND

After heart transplantation, calcineurin inhibitors (CNI) (cyclosporin A and tacrolimus) are key immunosuppressive drugs to prevent graft rejection. Whole-blood concentration (C blood )-guided therapeutic drug monitoring (TDM) is systematically performed to improve graft outcomes. However, some patients will still experience graft rejection and/or adverse events despite CNI C blood within the therapeutic range. Other pharmacokinetic parameters, such as the intragraft, or intracellular concentration at the CNI site of action could refine their TDM. Nonetheless, these remain to be explored. The objective of the INTRACAR study was to describe the relationship between whole blood, intragraft, and intracellular CNI concentrations as well as their efficacy in heart transplant recipients (HTR).

METHODS

In a cohort of HTR, protocol endomyocardial biopsies (EMB) were collected to assess rejection by anatomopathological analysis. Part of the EMB was used to measure the intragraft concentrations of CNI (C EMB ). C blood and the concentration inside peripheral blood mononuclear cells, (C PBMC ), a cellular fraction enriched with lymphocytes, were also monitored. Concentrations in the 3 matrices were compared between patients with and without biopsy-proven acute rejection (BPAR).

RESULTS

Thirty-four HTR were included, representing nearly 100 pharmacokinetic (PK) samples for each CNI. C blood , C EMB , and C PBMC correlated for both CNI. BPAR was observed in 74 biopsies (39.6%) from 26 patients (76.5%), all except one was of low grade. None of the PK parameters (C blood , C EMB , C PBMC , C EMB/blood , and C PBMC/blood ) was associated with BPAR.

CONCLUSIONS

In this cohort of well-immunosuppressed patients, no association was observed for any of the PK parameters, including C blood , with the occurrence of BPAR. However, a trend was noticed for the C EMB and C EMB/blood of cyclosporin A. Further studies in higher-risk patients may help optimize the use of C EMB and C PBMC for CNI TDM in HTR.

Cyclosporine A but Not Corticosteroids Support Efficacy of Ex Vivo Expanded, Adoptively Transferred Human Tregs in GvHD

Reshaping the immune balance by adoptive transfer of regulatory T-cells (Tregs) has emerged as a promising strategy to combat undesired immune reactions, including in Graft-versus-Host Disease (GvHD), which is the most lethal non-relapse complication of allogeneic hematopoietic stem cell transplantation. Currently however, little is known about the potentially inhibitory in vivo effects of conventional immunosuppressive drugs, which are routinely used to treat GvHD, on adoptively transferred Tregs. Here we demonstrate drug-specific effects of the conventional immunosuppressive drugs Cyclosporine A, Mycophenolate mofetil and methylprednisolone on adoptively transferred Tregs in a humanized NOD/SCID/IL2Rgamma-/- GvHD mouse model. The clinical course of GvHD and postmortem organ histology, including cellular organ infiltration, showed that co-administration of Cyclosporine A and Tregs is highly beneficial as it enhanced Treg accumulation at inflammatory sites like lung and liver. Similarly, co-administration of Mycophenolate mofetil and Tregs improved clinical signs of GvHD. In contrast, co-administration of methylprednisolone and Tregs resulted in reduced Treg recruitment to inflammatory sites and the fast deterioration of some animals. Consequently, when clinical trials investigating safety and efficacy of adjunctive Treg therapy in GvHD are designed, we suggest co-administering Cyclosporine A, whereas high doses of glucocorticosteroids should be avoided.

Kidney and Liver Tissue Tacrolimus Concentrations in Adult Transplant Recipients-The Influence of the Whole Blood and Tissue Concentrations on Efficiency of Treatment during Immunosuppressive Therapy

Tacrolimus (TAC) has a narrow therapeutic index and highly variable pharmacokinetic characteristics. Close monitoring of the TAC concentrations is required in order to avoid the risk of acute rejection or adverse drug reaction. The results in some studies indicate that inter-tissue TAC concentrations can be a better predictor with regards to acute rejection episode than TAC concentration in whole blood. Therefore, the aim of the study was to assess the correlation between dosage, blood, hepatic and kidney tissue concentration of TAC measured by a validated liquid chromatography tandem mass spectrometry (LC-MS/MS) and clinical outcomes in a larger cohort of 100 liver and renal adult transplant recipients. Dried biopsies were weighed, mechanically homogenized and then the samples were treated with a mixture of zinc sulfate—acetonitrile to perform protein precipitation. After centrifugation, the extraction with tert-butyl methyl ether was performed. The analytical range was proven for TAC tissue concentrations of 10–400 pg/mg. The accuracy and precision fell within the acceptance criteria for intraday as well as interday assay. There was no correlation between dosage, blood (C₀) and tissue TAC concentrations. TAC concentrations determined in liver and kidney biopsies ranged from 8.5 pg/mg up to 160.0 pg/mg and from 7.1 pg/mg up to 215.7 pg/mg, respectively. To the best of our knowledge, this is the first LC-MS/MS method for kidney and liver tissue TAC monitoring using Tac¹³C,D₂ as the internal standard, which permits measuring tissue TAC concentrations as low as 10 pg/mg.

Development and validation of a combined enzymatic-digestion/mass spectrometry assay for Tacrolimus quantitation in cardiac biopsies

Recent studies report strategies for analysing immunosuppressive drugs in brain, liver and renal tissue, mostly in animals: we developed and validated a two steps combined enzymatic digestion/mass spectrometry assay to quantify Tacrolimus (TAC) in heart biopsies. Our aims were to avoid sample loss and sample contamination during the laboratory preparation, and to limit matrix effects in the electrospray ionization source (ESI) of the mass spectrometer. Enzymatic tissue digestion followed by a liquid-liquid drug extraction in the same vial of reaction allowed us to reach both our aims. The assay was assessed for selectivity, matrix effect, linearity, Lower Limit of Quantification (LLOQ) and Detection (LOD), accuracy and precision, according to the "Guideline on Bioanalytical Method Validation (EMA). A stable isotopically labelled (SIL) analogue (¹³CD₂-TAC) was used as internal standard. The chromatographic separation of the analyte took 6 min. The observed linear range of quantification was 0.0162-0.520 ng in terms of TAC added to the biopsies (by 50 μL of the corresponding working solutions). The limit of detection and the lower limit of quantification (LLOQ) were 0.008 and 0.0162 ng, respectively. Both the mobile phases contained ammonium acetate and formic acid that promote the formation of ammoniated precursor ions that can be easily fragmented ([M + NH₄]⁺, TAC m/z 821.3; ¹³CD₂-TAC m/z 824.3). The calibration curves were generated by plotting analyte-to-internal standard peak area ratios versus TAC amount (ng) added to the biopsies, and using a weighted (1/x) linear regression. Curves were not forced to pass through the origin. Swine hearts were employed as blank matrix for all the analytical method validation procedures but, after approval by the ethics committee (by "Fondazione IRCCS Policlinico San Matteo": Protocol 20190032933), TAC was also quantified in endomyocardial biopsies from informed and consenting heart transplant patients. The study was funded by Fondazione IRCCS Policlinico San Matteo (RC08017617), as a part of the clinical studies on the maintenance of immunosuppressive therapy in cardiac transplant patients. Tacrolimus concentrations in patients biopsies were expressed as ratio between the detected amount of TAC (ng) in the tissue and the weight of the tissue itself (mg).

Relationship between allograft cyclosporin concentrations and P-glycoprotein expression in the 1st month following renal transplantation

The immunosuppressant cyclosporin is a P-glycoprotein (P-gp) substrate whose impaired function has been associated with an increased risk of cyclosporin-induced nephrotoxicity following renal transplantation. This study investigated the relationship between blood and allograft cyclosporin concentration, and the effect of P-gp expression. Fifty biopsy samples were obtained from 39 renal transplant recipients who received cyclosporin as part of maintenance immunosuppression. Blood cyclosporin concentrations (2 hours postdose) were obtained from clinical records, matching allograft cyclosporin concentrations were measured in frozen biopsy tissue by liquid chromatography-tandem mass spectrometry, and allograft P-gp expression was assessed by immunohistochemistry. Blood and allograft cyclosporin concentrations in the 1st month post-transplantation ranged from 505-2005 μg/L and 0.01-16.7 ng/mg tissue, respectively. Dose was the only significant predictor of allograft cyclosporin concentrations (adjusted R²  = .24, F-statistic = 11.52, P = .0019), with no effect of P-gp expression or blood cyclosporin concentrations. P-gp expression is not the major determinant of allograft cyclosporin concentrations.

Pharmacokinetics, Pharmacodynamics and Pharmacogenetics of Tacrolimus in Kidney Transplantation

Background:

Tacrolimus (Tac, or FK506), a calcineurin inhibitor (CNI), is the first-line immu-nosuppressant which consists of the footstone as immunosuppressive regimens in kidney transplantation. However, the drug toxicity and the significant differences of pharmacokinetics (PK) and pharmacodynam-ics (PD) among individuals are hidden troubles for clinical application. Recently, emerging evidences of Tac pharmacogenetics (PG) regarding drug absorption, metabolism, disposition, excretion and response are discovered for better understanding of this drug.

Method:

We reviewed the published articles regarding the Tac PG and its effects on PK and PD in kidney transplantation. In addition, we summarized information on polygenic algorithms.

Results:

The polymorphism of genes encoding metabolic enzymes and transporters related to Tac were largely investigated, but the results were inconsistent. In addition to CYP3A4, CYP3A5 and P-gp (also known as ABCB1), single nucleotide polymorphisms (SNPs) might also affect the PK and PD parameters of Tac.

Conclusion:

The correlation between Tac PK, PD and PG is very complex. Although many factors need to be verified, it is envisaged that thorough understanding of PG may assist clinicians to predict the optimal starting dosage, help adjust the maintenance regimen, as well as identify high risk patients for adverse ef-fects or drug inefficacy

Association of CYP3A5, CYP2C8, and ABCB1 Polymorphisms With Early Renal Injury in Chinese Liver Transplant Recipients Receiving Tacrolimus

BACKGROUND

The purpose of this study is to explore the association of CYP3A5, ABCB1, and CYP2C8 polymorphisms with the risk of developing early kidney impairment in Chinese liver transplant recipients receiving tacrolimus.

METHODS

CYP3A5, ABCB1, and CYP2C8 polymorphisms were genotyped in the Chinese liver transplant recipients in the study receiving tacrolimus for at least 2 years by polymerase chain reaction and high-resolution melting method. Serum cystatin C and urine microprotein (α1-microglobulin, microalbumin, transferrin, and immunoglobulin) of liver transplant recipients were used to determine both the status of early renal injury and the lesion part.

RESULTS

We documented 3 genotypes of CYP3A5 and ABCB1 and only 2 genotypes of CYP2C8 in our cohort. The levels of cystatin C and all 4 indicators of the urine microprotein in the recipient group were significantly higher than those in the control group (P < .05). The concentrations of transferrin differed significantly in each CYP3A5 genotype group (P < .05). Based on diverse CYP2C8 genotypes, we divided all the recipients into 2 groups: CYP2C8*1*1 group and CYP2C8*3*1 group. The concentrations of α1-microglobulin and cystatin C differed significantly between the 2 groups (P < .05). For CYP2C8*3, the positive predictive value is 68.5% and negative predictive value is 70.2%. For CYP3A5*3, the positive predictive value is 55.3% and negative predictive value is 60.4%.

CONCLUSIONS

CYP2C8*3 and CYP3A5*3 appear to be predictive of risk of tacrolimus-induced early renal impairment. CYP3A5*3 was associated with the risk of early renal glomerular lesion, while CYP2C8*3 was associated with the risk of the tubulointerstitial injury. ABCB1 polymorphisms (both C3435T and C1236T) were not associated with the early renal injury in liver transplant recipients.

Pharmacogenetic aspects of the use of tacrolimus in renal transplantation: recent developments and ethnic considerations

INTRODUCTION

Tacrolimus (Tac) is effective in preventing acute rejection but has considerable toxicity and inter-individual variability in pharmacokinetics and pharmacodynamics. Part of this is explained by polymorphisms in genes encoding Tac-metabolizing enzymes and transporters. A better understanding of Tac pharmacokinetics and pharmacodynamics may help to minimize different outcomes amongst transplant recipients by personalizing immunosuppression.

AREAS COVERED

The pharmacogenetic contribution of Tac metabolism will be examined, with a focus on recent discoveries, new developments and ethnic considerations.

EXPERT OPINION

The strongest and most consistent association in pharmacogenetics is between the CYP3A5 genotype and Tac dose requirement, with CYP3A5 expressers having a ~ 40-50% higher dose requirement compared to non-expressers. Two recent randomized-controlled clinical trials using CYP3A5 genotype, however, did not show a decrease in acute rejections nor reduced toxicity. CYP3A4*22, CYP3A4*26, and POR*28 are also associated with Tac dose requirements and may be included to provide the expected improvement of Tac therapy. Studies focusing on the intracellular drug concentrations and on calcineurin inhibitor-induced nephrotoxicity also seem promising. For all studies, however, the ethnic prevalence of genotypes should be taken into account, as this may significantly impact the effect of pre-emptive genotyping.

Alternative matrices for therapeutic drug monitoring of immunosuppressive agents using LC-MS/MS

Immunosuppressive drugs used in solid organ transplants typically have narrow therapeutic windows and high intra- and intersubject variability. To ensure satisfactory exposure, therapeutic drug monitoring (TDM) plays a pivotal role in any successful posttransplant maintenance therapy. Currently, recommendations for optimum immunosuppressant concentrations are based on blood/plasma measurements. However, they introduce many disadvantages, including poor prediction of allograft survival and toxicity, a weak correlation with drug concentrations at the site of action and the invasive nature of the sample collection. Thus, alternative matrices have been investigated. This paper reviews tandem-mass spectrometry (LC-MS/MS) methods used for the quantification of immunosuppressant drugs utilizing nonconventional matrices, namely oral fluids, fingerprick blood and intracellular and intratissue sampling. The advantages, disadvantages and clinical application of such alternative mediums are discussed. Additionally, sample extraction techniques and basic chromatography information regarding these methods are presented in tabulated form.

Surrogate matrix: opportunities and challenges for tissue sample analysis

Often there is limited availability of matching tissue matrix and/or the analyte may occur endogenously in the target tissue. Surrogate matrix provides an option for quantitation of drug, metabolite(s) and biomarker(s) in these circumstances. However, the use of a surrogate matrix also presents challenges. This paper summarizes and discusses the challenges of selecting a proper surrogate, validating the suitability of the surrogate and establishing a surrogate tissue method using the fit-for-purpose approach. This paper also systematically reviews the current practices for evaluating key parameters of a surrogate tissue assay, including sensitivity, specificity, selectivity, interference, precision, accuracy, recovery, matrix effects and stability. Considerations and suggestions are provided for dealing with such challenges during method establishment and tissue sample analysis.

Validation of an LC-MS/MS method for the quantification of mycophenolic acid in human kidney transplant biopsies

Mycophenolic acid (MPA) has a low therapeutic index and large inter-individual pharmacokinetic variability necessitating therapeutic drug monitoring to individualise dosing after transplantation. There is an ongoing discrepancy as to whether plasma MPA concentrations sufficiently predict kidney rejection or toxicity and whether immunosuppressant concentrations within the graft tissue may better predict transplant outcomes. The aim of the study was to develop an LC-MS/MS method for the quantification of MPA concentrations in human kidney biopsies taken as part of routine clinical procedures. A total of 4 surplus human kidney biopsies obtained from 4 different kidney transplant recipients were available to use for this study. MPA was also quantified in 2 kidney samples from rats administered MPA to assess tissue extraction reproducibility. Human kidney biopsies and rat kidneys were homogenised mechanically and underwent liquid-liquid extraction before analysis by LC-MS/MS. MPA-free human kidney tissue was used in calibrators and quality control samples. Analyte detection was achieved from multiple reaction monitoring of the ammonium adducts of both MPA (m/z 321.1→207.3) and N-phthaloyl-l-phenylalanine (PPA, internal standard, m/z 296.2→250.2) using positive electrospray ionisation. The method was linear (calibration curves R(2)>0.99, n=10), precise, and accurate with coefficients of variation and bias less than 15%. Extraction efficiencies for MPA and PPA were approximately 97% and 86%, respectively, and matrix effects were minimal. In 4 kidney transplant recipients, tissue MPA concentrations ranged from 1.3 to 7.7ng/mg of tissue, however, the correlation between blood (C0) and tissue MPA concentrations could not be established. The method was successfully applied to the quantification of MPA in human kidney biopsies without the need to alter current clinical protocols.