Pharmacokinetics and pharmacodynamics in renal transplant recipients under treatment with cyclosporine and Myfortic

[Recommendations when switching therapy from immunosuppressive drugs to dupilumab in patients with atopic dermatitis]

Basierend auf neuen Erkenntnissen zur molekularen Pathogenese der atopischen Dermatitis, wurde neben Glukokortikoiden und Ciclosporin mit Dupilumab nun auch eine zielgerichtete antientzündliche Systemtherapie zugelassen. Wegen ihrer Pharmakologie sind weder Glukokortikoide und Ciclosporin noch die außerhalb der Zulassung angewendeten Substanzen Methotrexat, Azathioprin und Mycophenolsäurederivate für eine Langzeittherapie geeignet. Bei der Umstellung der Therapie von den genannten niedermolekularen Substanzen auf Dupilumab sollten verschiedene Faktoren berücksichtigt werden. Hierbei sind sowohl der konkrete Anlass der Umstellung (Unwirksamkeit, unerwünschte Wirkungen oder sich einstellende Kontraindikationen) als auch die pharmakologischen Gegebenheiten zu berücksichtigen. Da es hierzu bisher keine konkreten klinischen Untersuchungen gibt, haben die Autoren auf der Grundlage einer Literaturrecherche Handlungsempfehlungen für den praktischen Alltag erarbeitet.

Sustained Inhibition of Calcineurin Activity With a Melt-Dose Once-daily Tacrolimus Formulation in Renal Transplant Recipients

Tacrolimus (Tac) is the cornerstone calcineurin inhibitor in transplantation. Extended-release Meltdose formulation (Tac-LCP) offers better bioavailability compared with immediate-release formulation (Tac-IR). We postulated that the less fluctuating pharmacokinetic (PK) profile of Tac-LCP might maintain a sustained inhibition of calcineurin activity (CNA) between dose intervals. Higher concentrations (peak plasma concentration (C_max )) after Tac-IR may not result in a more potent CNA inhibition due to a capacity-limited effect. This study was aimed at evaluating the pharmacodynamic (PD)/PK profiles of Tac-IR compared with Tac-LCP. An open-label, prospective, nonrandomized, investigator-driven study was conducted. Twenty-five kidney transplant recipients receiving Tac-IR were switched to Tac-LCP. Before and 28 days after conversion, intensive CNA-PD and PK sampling were conducted using ultra-high-performance liquid chromatography-tandem accurate mass spectrometry. PD nonlinear mixed effects model was performed in Phoenix-WinNonlin. Statistically significant higher C_max (P < 0.001) after Tac-IR did not result in lower CNA as compared with after Tac-LCP (P = 0.860). Tac-LCP showed a statistically more maintained CNA inhibition between dose intervals (area under the effect-time curve from 0 to 24 hours (AUE_0-24h )) compared with Tac-IR, in which CNA returned to predose levels after 4 hours of drug intake (373.8 vs. 290.5 pmol RII·h/min·mg prot, Tac-LCP vs. Tac-IR; P = 0.039). No correlation was achieved between any PD and PK parameters in any formulations. Moreover, Tac concentration to elicit a 50% of the maximum response (half-maximal inhibitory concentration) was 9.24 ng/mL. The higher C_max after Tac-IR does not result in an additional CNA inhibition compared with Tac-LCP attributable to a capacity-limited effect. Tac-LCP may represent an improvement of the PD of Tac due to the more sustained CNA inhibition during dose intervals.

Maintenance Immunosuppression in Solid Organ Transplantation: Integrating Novel Pharmacodynamic Biomarkers to Inform Calcineurin Inhibitor Dose Selection

Calcineurin inhibitors, the primary immunosuppressive therapy used to prevent alloreactivity of transplanted organs, have a narrow therapeutic index. Currently, treatment is individualized based on clinical assessment of the risk of rejection or toxicity guided by trough concentration monitoring. Advances in immune monitoring have identified potential markers that may have value in understanding calcineurin inhibitor pharmacodynamics. Integration of these markers has the potential to complement therapeutic drug monitoring. Existing pharmacokinetic-pharmacodynamic (PK-PD) data is largely limited to correlation between the biomarker and trough concentrations at single time points. Immune related gene expression currently has the most evidence supporting PK-PD integration. Novel biomarker-based approaches to pharmacodynamic monitoring including development of enhanced PK-PD models are proposed to realize the full clinical benefit.

Pharmacokinetic considerations related to therapeutic drug monitoring of tacrolimus in kidney transplant patients

INTRODUCTION

Tacrolimus (Tac) is the cornerstone of immunosuppressive therapy after solid organ transplantation and will probably remain so. Excluding belatacept, no new immunosuppressive drugs were registered for the prevention of acute rejection during the last decade. For several immunosuppressive drugs, clinical development halted because they weren't sufficiently effective or more toxic. Areas covered: Current methods of monitoring Tac treatment, focusing on traditional therapeutic drug monitoring (TDM), controversies surrounding TDM, novel matrices, pharmacogenetic and pharmacodynamic monitoring are discussed. Expert opinion: Due to a narrow therapeutic index and large interpatient pharmacokinetic variability, TDM has been implemented for individualization of Tac dose to maintain drug efficacy and minimize the consequences of overexposure. The relationship between predose concentrations and the occurrence of rejection or toxicity is controversial. Acute cellular rejection also occurs when the Tac concentration is within the target range, suggesting that Tac whole blood concentrations don't necessarily correlate with pharmacological effect. Intracellular Tac, the unbound fraction of Tac or pharmacodynamic monitoring could be better biomarkers/tools for adequate Tac exposure - research into this has been promising. Traditional TDM, perhaps following pre-emptive genotyping for Tac-metabolizing enzymes, must suffice for a few years before these strategies can be implemented in clinical practice.

Pharmacokinetics and pharmacodynamics of immunosuppressive drugs in elderly kidney transplant recipients

Elderly patients are a fast growing population among transplant recipients over the past decades. Both the innate and adaptive immune reactivity decrease with age, which is believed to contribute to the decreased incidence of acute rejection and increased infectious death rate in elderly transplant recipients. In contrast to recipient age, donor age is associated with a higher incidence of acute rejection. Pharmacokinetic studies in renal transplant recipients show that CNI troughs are >5% higher in elderly compared to younger patients given the same dose normalized by body weight. This may impact the starting dose of tacrolimus and cyclosporine. Possibly in elderly patients the intracellular (in lymphocyte) concentrations are relatively high in relation to the whole blood concentration, resulting in a stronger pharmacodynamic effect at the same whole blood trough concentration. For cyclosporine this has been shown, but it is not clear if the same is true for other immunosuppressive drugs. Pharmacodynamic studies have compared the inhibition of target enzymes, or more downstream effects of immunosuppressive drugs, in younger and older patients. Measurement of nuclear factor of activated T-cell (NFAT)-regulated gene expression (RGE), a pharmacodynamic read-out of CNI, is a promising biomarker of immunosuppression. Low levels of NFAT RGE are associated with increased risk of infection and non-melanoma skin cancer in elderly patients. Clinical trials to evaluate the safety and efficacy of immunosuppression regimens in this specific patient population, which is underrepresented in published trials, are lacking. More studies in elderly patients are needed to investigate the impact of age on the pharmacokinetics or pharmacodynamics of immunosuppressive drugs, and to decide on the optimal regimen and target levels for elderly transplant recipients.

Pharmacology and toxicology of mycophenolate in organ transplant recipients: an update. Arch Toxicol. 2014;88:1351-1389. [PMID: 24792322 DOI: 10.1007/s00204-014-1247-1]

This review aims to provide an update of the literature on the pharmacology and toxicology of mycophenolate in solid organ transplant recipients. Mycophenolate is now the antimetabolite of choice in immunosuppressant regimens in transplant recipients. The active drug moiety mycophenolic acid (MPA) is available as an ester pro-drug and an enteric-coated sodium salt. MPA is a competitive, selective and reversible inhibitor of inosine-5'-monophosphate dehydrogenase (IMPDH), an important rate-limiting enzyme in purine synthesis. MPA suppresses T and B lymphocyte proliferation; it also decreases expression of glycoproteins and adhesion molecules responsible for recruiting monocytes and lymphocytes to sites of inflammation and graft rejection; and may destroy activated lymphocytes by induction of a necrotic signal. Improved long-term allograft survival has been demonstrated for MPA and may be due to inhibition of monocyte chemoattractant protein 1 or fibroblast proliferation. Recent research also suggested a differential effect of mycophenolate on the regulatory T cell/helper T cell balance which could potentially encourage immune tolerance. Lower exposure to calcineurin inhibitors (renal sparing) appears to be possible with concomitant use of MPA in renal transplant recipients without undue risk of rejection. MPA displays large between- and within-subject pharmacokinetic variability. At least three studies have now reported that MPA exhibits nonlinear pharmacokinetics, with bioavailability decreasing significantly with increasing doses, perhaps due to saturable absorption processes or saturable enterohepatic recirculation. The role of therapeutic drug monitoring (TDM) is still controversial and the ability of routine MPA TDM to improve long-term graft survival and patient outcomes is largely unknown. MPA monitoring may be more important in high-immunological recipients, those on calcineurin-inhibitor-sparing regimens and in whom unexpected rejection or infections have occurred. The majority of pharmacodynamic data on MPA has been obtained in patients receiving MMF therapy in the first year after kidney transplantation. Low MPA area under the concentration time from 0 to 12 h post-dose (AUC0-12) is associated with increased incidence of biopsy-proven acute rejection although AUC0-12 optimal cut-off values vary across study populations. IMPDH monitoring to identify individuals at increased risk of rejection shows some promise but is still in the experimental stage. A relationship between MPA exposure and adverse events was identified in some but not all studies. Genetic variants within genes involved in MPA metabolism (UGT1A9, UGT1A8, UGT2B7), cellular transportation (SLCOB1, SLCO1B3, ABCC2) and targets (IMPDH) have been reported to effect MPA pharmacokinetics and/or response in some studies; however, larger studies across different ethnic groups that take into account genetic linkage and drug interactions that can alter a patient's phenotype are needed before any clinical recommendations based on patient genotype can be formulated. There is little data on the pharmacology and toxicology of MPA in older and paediatric transplant recipients.

Protocol biopsies in pediatric renal transplant recipients on cyclosporine versus tacrolimus-based immunosuppression

BACKGROUND

Protocol biopsies can detect subclinical rejection and early signs of calcineurin inhibitor-induced nephrotoxicity.

METHODS

In a prospective study, protocol biopsies 3 and 12 months after transplant in transplanted children from two centers were studied. One center used cyclosporine (CsA)-based immunosuppression and the other center used tacrolimus. Patients were on CsA (n = 26, group 1) or on tacrolimus (n = 10, group 2). Patients received basiliximab induction, mycophenolate mofetil, and prednisone.

RESULTS

In patients on CsA, 26 kidney biopsies were performed during the 6 months after transplantation. Eighteen protocol biopsies were performed at 3 months post transplant; 13 were normal and five showed rejection (two borderline and three Banff II rejections). Eight biopsies were motivated by an increase of serum creatinine; four were normal and four revealed signs of acute rejection (two borderline and two Banff II). Twelve protocol biopsies were performed after 12 months; all were normal. For patients on tacrolimus (n = 10), ten protocol transplant biopsies were performed at 3 months post-transplant; none showed signs of rejection. No biopsy was performed for an increase of serum creatinine. There were no differences in patient age, number of human leukocyteantigen (HLA) incompatibilities, or other patient characteristics.

CONCLUSIONS

Patients on tacrolimus had less acute rejection episodes detected on protocol biopsies 3 months after transplant. Protocol biopsies seem to play an important role in the detection of subclinical rejection in patients on CsA.

Pharmacokinetics of Cyclosporine A in Chinese heart transplant recipients

AIM

To determine the steady state concentration and the pharmacokinetics of Cyclosporine A (CsA) in heart transplant recipients.

METHODS

A single dose of 100 mg CsA capsules twice daily was given to five heart transplant recipients of steady state. The concentrations of CsA in plasma were determined by streptavidin peroxidase fluorescent polarization immunoassay.

RESULTS

The main pharmacokinetic parameters of CsA were as follows: t(max) (1.60 ± 0.55) h, ρmax(951.60 ± 229.20) μg.L-1, t1/2(6.53 ± 2.40) h, and AUC0 -t(5162.10 ± 1355.01) μg.h.L-1.

CONCLUSION

The study obtained the steady state pharmacokinetic parameters of CsA in Chinese heart transplant recipients.

Pharmacodynamic monitoring of canine T-cell cytokine responses to oral cyclosporine

BACKGROUND

Pharmacodynamic assays measure the immunosuppressive effects of cyclosporine on T-cells and offer an alternative assessment of efficacy in individual patients.

OBJECTIVE

To assess the immunosuppressive effects of high and low dosage cyclosporine on canine T-cells and to develop a novel testing system for individualized dose adjustment.

ANIMALS

Seven healthy female Walker hounds.

METHODS

Experimental study using a paired comparison design. Flow cytometry was used to measure T-cell expression of IL-2, IL-4, and IFN-γ. Cytokine expression 8 days after oral administration of high and low dosages of cyclosporine was compared to baseline and washout values, respectively. The high dosage was initially 10 mg/kg q12h and was then adjusted to attain established immunosuppressive trough blood drug concentrations (>600 ng/mL). The low dosage was 5 mg/kg q24h.

RESULTS

High dosage cyclosporine resulted in significant decreases in IL-2 and IFN-γ expression (P = .0156, P = .0156), but not IL-4 expression (P = .2188). Low dosage cyclosporine was associated with a significant decrease in IFN-γ expression (P = .0156), while IL-2 expression was not affected (P = .1094).

CONCLUSIONS AND CLINICAL IMPORTANCE

T-cell function is suppressed at trough blood drug concentrations exceeding 600 ng/mL, and is at least partially suppressed in some dogs at low dosages. Direct evaluation of T-cell function could be an effective, more sensitive alternative to measuring blood drug concentrations for monitoring immunosuppressive therapy.

Principles of therapeutic drug monitoring

Therapeutic drug monitoring (TDM) is central to optimize drug efficacy in children, because the pharmacokinetics and pharmacodynamics of most drugs differ greatly between children and adults. Many factors should be analyzed to implement TDM in the pediatric population, including a validated pharmacological parameter and an analytical method adapted to children as limited sampling volumes and high sensitivity are required. The use of population approaches, new analytical methods such as saliva and dried blood spots, and pharmacodynamic monitoring give attractive options to improve TDM, individualize therapy in order to optimize efficacy and reduce adverse drug reactions.

Pharmacodynamic monitoring of calcineurin inhibition therapy: principles, performance, and perspectives. Ther Drug Monit. 2010;32:3-10. [PMID: 20009796 DOI: 10.1097/ftd.0b013e3181c0eecb]

The calcineurin inhibitors (CNIs) cyclosporin A and tacrolimus are immunosuppressive drugs used extensively in allograft recipients. These drugs show large interindividual pharmacokinetic variation and are associated with severe adverse affects, including nephrotoxicity and cardiovascular disease. In current practice, CNIs are combined with other immunosuppressive drugs such as steroids and mycophenolate mofetil. Dosage is titrated based on blood concentration measurement. For further optimization of calcineurin (CN) inhibition therapy, new monitoring strategies are required. Pharmacodynamic-monitoring strategies constitute novel approaches for optimization of CNIs therapy. This review focuses on the general aspects of immunosuppressive drug pharmacodynamic monitoring and describes the methodologies used for monitoring CN inhibition therapy. Two different types of pharmacodynamic-monitoring strategies can be distinguished: (1) enzymatic strategies, which monitor inhibition of drug-target enzyme activity, and (2) immunologic strategies, which measure cellular responsiveness after in vitro simulated immunologic responses. Enzymatic tests are drug type-specific markers in which CN activity is directly determined. Immunologic strategies measure immune responsiveness at several levels, such as mRNA transcripts (intracellular) concentrations/excretion of cytokines, expression of surface activation markers, and cell proliferation. This review also discusses analytical issues and clinical experience with these techniques. The call for new methodologies to evaluate immunosuppressive therapy has led to the development of a large variety of pharmacodynamic-monitoring strategies. The first reports of their clinical relevance are available, but further understanding of the analytical and clinical variables involved are required for the development of accurate, reproducible, and clinically relevant markers.

Effect of bifendate on the pharmacokinetics of cyclosporine in relation to the CYP3A4*18B genotype in healthy subjects

AIM

To evaluate the potential drug-drug interactions between bifendate and cyclosporine, a substrate of CYP3A4, in relation to different CYP3A4*18B genotype groups.

METHODS

Eighteen unrelated healthy subjects (six CYP3A4*1*1, six CYP3A4*1/*18B, and six CYP3A4*18/*18B) were selected for this study. After repeated oral administration of a placebo or bifendate (three times daily for 14 d), the whole-blood level of cyclosporine was measured using high performance liquid chromatography-electrospray mass spectrometry (HPLC/ESI-MS). This study was carried out in a two-phase randomized crossover manner.

RESULTS

After the treatment with bifendate, the areas under the curve (AUC(0-24) and AUC(0-infinity)) decreased significantly by 9.7%+/-3.7% (P=0.01) and 19.2%+/-16.8% (P=0.001) in CYP3A4*1/*1 subjects, 11.3%+/-9.4% (P=0.03) and 10.5%+/-9.6% (P=0.043) in CYP3A4*1/*18B subjects, and 40.2%+/-14.7% (P=0.02) and 37.5%+/-15.8% (P=0.003) in CYP3A4*18B/*18B subjects. Meanwhile, the decreases in the AUC(0-24) and AUC(0-infinity) values in the three groups were significantly different (using one-way analysis of variance, P=0.001 and P=0.001), and the change in the CYP3A4*18B/*18B group was greater than that in the other two groups. The oral clearance of cyclosporine was altered in all the subjects, with substantial increases by 10.2%+/-4.4% (P=0.004) in CYP3A4*1/*1 subjects, 14.0%+/-12.0% (P=0.048) in CYP3A4*1/*18B subjects, and 32.4%+/-21.7% (P=0.013) in CYP3A4*18B/*18B subjects.

CONCLUSION

These results suggest that bifendate decreases the plasma concentration of cyclosporine in a CYP3A4 genotype-dependent manner.