The temporal profile of calcineurin inhibition by cyclosporine in vivo

Pharmacodynamic monitoring by residual NFAT-regulated gene expression in stable pediatric liver transplant recipients

Pharmacokinetic monitoring of CNI is unsatisfactory, because at comparable CNI blood concentrations frequency and severity of adverse effects vary considerably among individual patients. Determining the RGE of NFAT-regulated genes in leukocytes is a new pharmacodynamic approach to measure directly the functional consequences of calcineurin inhibition in T-lymphocytes. We compared clinical outcome parameters and RGE of activated T-cells after pLtx. We measured prospectively RGE of NFAT regulated genes in 33 pLTX recipients in the maintenance period after pLTX. CsA-treated patients with recurrent infections had significantly lower RGE rates (27%) than children without recurrent infections (50%; p = 0.04), whereas pharmacokinetic parameters of CsA and the concomitant immunosuppressive therapy were comparable between both groups. In patients on tacrolimus-based IS therapy NFAT RGE was only slightly reduced (90%). Pharmacodynamic monitoring of CsA by measurement of RGE in T-lymphocytes has the potential to identify over-immunosuppressed pediatric liver transplant recipients on a CsA-based IS therapy, while in children on low-dose tacrolimus therapy, RGE measurement does not provide additional clinically useful information.

Repeated recall of learned immunosuppression: evidence from rats and men

Akin to other physiological responses, the immune system can be modified, via Pavlovian or behavioral conditioning. It is unknown, however, whether and to what extent learned immune responses can be repeatedly recalled over time. Here we demonstrate in both rats and humans that repeated contingent pairing of a novel taste (conditioned stimulus, CS) together with the immunosuppressive drug cyclosporine A as unconditioned stimulus (US) leads to the acquisition of a learned immunosuppression. Sole presentation of the CS caused a significant inhibition of interleukin (IL)-2 and interferon (IFN)-γ production by rat splenic T cells and human peripheral T lymphocytes, closely mimicking the effect of the drug. More importantly, a comparable suppression of cytokine production was also observed after a second, unreinforced exposure to the CS that was separated from the first evocation by an interval of 6 (rats) or 11 (humans)days, respectively. Together, our findings demonstrate that a learned immunosuppression can be repeatedly recalled in both animals and humans, which is an important prerequisite for the implementation of conditioning paradigms as supportive therapy.

Effects of cyclosporine, tacrolimus and rapamycin on renal calcium transport and vitamin D metabolism

BACKGROUND

Abnormalities in mineral metabolism are common complications of organ transplantation. The role of immunosuppressive agents in alteration of mineral metabolism is not clear.

METHODS

We conducted an animal study to investigate the effects of cyclosporine A (CsA), tacrolimus, and sirolimus on renal calcium, magnesium and vitamin D metabolism.

RESULTS

CsA and tacrolimus induced a 2- to 3-fold and 1.6- to 1.8-fold increase in urinary calcium and magnesium excretion, respectively, while rapamycin had no effects on calcium, but doubled the urinary magnesium excretion. CsA and tacrolimus, but not rapamycin, elevated serum 1,25(OH)(2) vitamin D without affecting the parathyroid hormone level. CsA and tacrolimus reduced mRNA abundance in TRPV5 (CsA: 64 ± 3% of control; tacrolimus: 50 ± 3%) calbindin-D28k (CsA: 62 ± 4%; tacrolimus: 43 ± 3%), and vitamin D receptor (CsA: 52 ± 3%; tacrolimus: 58 ± 2%, all p < 0.05). Rapamycin did not affect gene expression in any of studied proteins. The immunofluorescence staining study demonstrated a 50% reduction of TRPV5 and calbindin-D28k by CsA and tacrolimus.

CONCLUSION

The suppression of VDR by calcineurin inhibitors is probably the underlying mechanism of renal calcium wasting. In spite of an increased 1,25(OH)(2) vitamin D level, the kidney is not able to reserve calcium, suggesting a role of vitamin D resistance that may be related to bone loss.

Use of immunoglobulins in the prevention of GvHD in a xenogeneic NOD/SCID/γc- mouse model

The efficacy of IVIG in preventing GvHD has not been definitely demonstrated clinically. Using a xenogeneic model of GvHD in NOD/SCID/γc- (NSG) mice, we showed that weekly administration of IVIG significantly reduced the incidence and associated mortality of GvHD to a degree similar to CsA. Unlike CsA and OKT3, IVIG were not associated with inhibition of human T-cell proliferation in mice. Instead, IVIG significantly inhibited the secretion of human IL-17, IL-2, IFN-γ and IL-15 suggesting that IVIG prevented GvHD by immunomodulation. Furthermore, the pattern of modification of the human cytokine storm differed from that observed with CsA and OKT3. Finally, in a humanized mouse model of immune reconstitution, in which NSG mice were engrafted with human CD34(+) stem cells, IVIG transiently inhibited B-cell reconstitution, whereas peripheral T-cell reconstitution and thymopoiesis were unaffected. Together these in vivo data raise debate related to the appropriateness of IVIG in GvHD prophylaxis. In addition, this model provides an opportunity to further elucidate the precise mechanism(s) by which IVIG inhibit GvHD.

Safety and toxicology of cyclosporine in propylene glycol after 9-month aerosol exposure to beagle dogs

BACKGROUND

Cyclosporine inhalation solution (CIS) delivered via nebulization is under evaluation for the prevention of chronic rejection post-lung transplant. A 300-patient randomized, controlled clinical trial (CYCLIST) is expected to be completed late in 2011. In support of this trial, a chronic inhalation toxicology study in dogs has been completed.

METHODS

To mimic the clinical setting, animals (four/sex/dose plus two/sex/dose in the control and high dose recovery groups) were exposed to aerosolized CIS, via nose-only exposure, three times per week for 9 months at targeted inhaled doses of 0 (air), 4, 12, and 24 mg/kg. In addition, the potential for persistence or reversibility of any toxic effects were assessed after a 6-week recovery period. The toxicological endpoints included clinical observations, body-weight, food consumption, toxicokinetics, clinical chemistry, and histopathology.

RESULTS

All dogs receiving CIS completed the study with the only consistent observations being excessive salivation and changes in minute ventilation. There was no limiting lung or systemic toxicity associated with exposure to CIS, and the only possible drug-related effect was an observation of benign fibroadenoma tissue in the mammary glands of the high-dose female recovery group. Toxicokinetic data showed that cyclosporine is initially absorbed rapidly with little drug remaining in lung tissue or blood 24 h after the end of dosing.

CONCLUSION

The study supports the pulmonary and systemic safety of aerosolized CIS at expected lung dose levels/kg of up to 12 times greater than the average dose patients are receiving in the CYCLIST trial.

Biomarkers as a tool for management of immunosuppression in transplant patients

Therapeutic drug monitoring is a well-established approach in transplantation medicine to guide immunosuppressive therapy. However, it cannot always predict the effects of immunosuppressive drugs on immune cells, because it does not reflect any aspect of an individual patient's immune system. Pharmacodynamic monitoring is a more recent strategy to provide information about the biologic effect of a specific drug or drug combination on the individual transplant patient. Currently, there is a large number of different biomarkers that either directly (specific markers) or indirectly (global markers) relate to the pharmacodynamic effects of immunosuppressive drugs and are under investigation as potential candidates to be introduced in clinical practice. Such biomarkers may be useful to identify patients at risk of developing acute rejection, infection, or cancer as well as patients who are suitable for minimization of immunosuppressant therapy and may be helpful to manage the timing and rate of immunosuppressant weaning. Serial longitudinal monitoring may allow maintenance of an individualized immunosuppressive regimen. Thus, biomarker monitoring is a potential complementary tool to therapeutic drug monitoring. This review summarizes the current state of knowledge about the use of a number of global or drug-specific pharmacodynamic biomarkers. It is not a comprehensive overview of the literature available, but rather an evidence-based reflection by experts who are intensively involved in scientific work in this field.

A comparison of short-term exposure of once-daily extended release tacrolimus and twice-daily cyclosporine on renal function in healthy volunteers

BACKGROUND

Calcineurin inhibitor nephrotoxicity remains an issue for recipients of solid organ transplants. After cyclosporine A (CsA) microemulsion administration, effective renal plasma flow (ERPF) and glomerular filtration rate(GFR) are decreased coincident with the maximal concentration (Cmax) of CsA. The pharmacokinetic (PK) profile of the once-daily formulation of tacrolimus extended release (Tac ER) includes an equivalent AUCPK 0-24 hr and a lower Cmax versus twice-daily Tac immediate release.

METHODS

Eighteen healthy subjects were allocated once-daily Tac ER and twice-daily CsA in a prospective, randomized,open-label, two-period, two-sequence single crossover study. CsA was targeted to C2 of 700 to 1400 ng/mL, and Tac ER was targeted to C0 of 5 to 10 ng/mL. Pharmacodynamic (PD) assessments were conducted preexposure, and PD and PK were assessed during a 6-hr postdose period after 10-day exposure.

RESULTS

The achieved mean C(o) Tac and CsA were 6.4 +/- 1.16 and 201 +/- 57 ng/mL, respectively. At Cmax, the change in ERPF was +30 +/- 127 vs. -70 +/- 96 mL/min/1.73 m2 relative to baseline for Tac ER and CsA (P=0.0085). The ERPF and GFR AUC (PD 0-6) hr were 3645 +/- 887 vs. 3210 +/- 582 mL/1.73 m2 (P=0.027) and 604 +/- 98 vs. 543+/- 79 mL/1.73 m2(P=0.023) for Tac ER versus CsA, respectively. Both systolic and diastolic blood pressures were significantly greater with exposure to CsA compared with Tac ER.

CONCLUSIONS

Acute reductions in ERPF and GFR are attenuated with Tac ER compared with CsA and may correlate with the differing PK profiles of these calcineurin inhibitors.

Toward managing chronic rejection after lung transplant: the fate and effects of inhaled cyclosporine in a complex environment

The fate and effects of inhaled cyclosporine A (CsA) are considered after deposition on the lung surface. Special emphasis is given to a post-lung transplant environment and to the potential effects of the drug on the various cell types it is expected to encounter. The known stability, metabolism, pharmacokinetics and pharmacodynamics of the drug have been reviewed and discussed in the context of the lung microenvironment. Arguments support the contention that the immuno-inhibitory and anti-inflammatory effects of CsA are not restricted to T-cells. It is likely that pharmacologically effective concentrations of CsA can be sustained in the lungs but due to the complexity of uptake and action, the elucidation of effective posology must ultimately rely on clinical evidence.

The use of cyclosporine in dermatology: part II

Cyclosporine is highly effective in the treatment of a multitude of dermatoses. Concern over its side effect profile has limited its use in dermatology. Adverse effects are, for the most part, dose dependent and related to duration of therapy. Using the recommended monitoring protocols results in a significant decrease in the incidence of cyclosporine-related toxicities. This article provides a comprehensive review of the pharmacokinetics of cyclosporine, potential drug interactions, adverse effects, and recommendations for monitoring in patients treated with cyclosporine. The use of cyclosporine in pregnancy and in the pediatric population is also addressed.

LEARNING OBJECTIVES

After completing this learning activity, participants should be familiar with the monitoring guidelines of cyclosporine, its contraindications, its possible drug interactions, its adverse effect profile, and its use in pregnancy and the childhood and adolescent populations.

Pharmacodynamic monitoring of cyclosporine A by NFAT-regulated gene expression and the relationship with infectious complications in pediatric renal transplant recipients

Pharmacokinetic monitoring of CsA is unsatisfactory, because at comparable CsA blood concentrations, the frequency and severity of adverse effects vary considerably among patients. We have therefore recently developed a precise, reliable, and robust whole-blood pharmacodynamic assay that measures the suppression of CsA-target genes in T lymphocytes. Because of the different characteristics of CsA pharmacokinetics in children and the higher propensity for infectious complications, this assay requires validation in the pediatric patient population. We therefore quantified in a prospective study of 45 pediatric renal transplant recipients the residual expression of NFAT-regulated genes in lymphocytes by RT-PCR and correlated these findings with the frequency of recurrent infections in the maintenance period post-transplant. Patients with recurrent infections showed a significantly stronger inhibition of NFAT-regulated gene expression (18.2%) than patients without recurrent infections (31.7%; p = 0.012). This difference was specific, because various PK parameters of CsA and the concomitant immunosuppressive therapy were comparable between patients. Multivariate regression analysis showed that patient age and residual NFAT-regulated gene expression were the only independent determinants of recurrent infections. By ROC curve analysis, a cutoff value of 23% residual NFAT-regulated gene expression had the highest sensitivity (71.1%) and specificity (65.4%) for the discrimination of patients with and without recurrent infections. Pharmacodynamic monitoring of CsA by measurement of residual NFAT-regulated gene expression in T lymphocytes has the potential to identify over-immunosuppressed pediatric renal transplant recipients and is therefore a useful tool for the optimization of CsA therapy.

Whole blood flow cytometric measurement of NFATc1 and IL-2 expression to analyze cyclosporine A-mediated effects in T cells

The calcineurin inhibitor Cyclosporine A (CsA) is one of the crucial immunosuppressive drugs given after organ transplantation. The small therapeutic window of CsA generates the dilemma that efficient and toxic drug doses differ only slightly. Moreover, these threshold concentrations differ considerably between individuals; therefore, functional assays are urgently needed. We explored whether the transcription factor NFATc1, a direct as well as indirect target of CsA, can be used as a potential biomarker to determine the individual immunosuppressive activity of CsA. First, in isolated human T cells we showed that flow cytometry is practicable to measure NFATc1, the most abundant NFATc isoform in activated T cells. Second, for whole blood we developed a flow cytometric assay to determine in parallel the inducible transcription factor NFATc1 and the cytokine IL-2 in stimulated T cells. We found that added CsA inhibits both the expression of NFATc1 and IL-2 in T cells of stimulated whole blood samples with IC(50) values of 200 and 150 nM, respectively. The intra- and inter-assay variability was low, and clinical practicability was good. Further experiments have to demonstrate whether the parallel cytometric measurement of NFATc1 and IL-2 in whole blood is a good predictor of individual CsA efficacy and toxicity in CsA-treated patients.

A three-dimensional organotypic assay to measure target cell killing by cytotoxic T lymphocytes

Cytotoxic T lymphocytes (CTL) mediate antigen- and cell-cell contact dependent killing of target cells, such as cancer cells and virus-infected cells. In vivo, this process requires the active migration of CTL towards and away from target cells. We here describe an organotypic 3D collagen matrix assay to monitor CTL migration together with CTL-mediated killing of target cells. The assay supports both, time-lapse microscopy of killing dynamics as well as population analysis of killing after matrix digestion and flow cytometry. The assay was used to assess the detrimental effect of cyclosporine A (CsA) present during CTL activation, which caused an inhibition of CTL-target cell conjugation and strongly impaired CTL-mediated killing, particularly at low effector-target ratios. Thus, the organotypic assay is useful to monitor spatiotemporal control mechanisms of cytotoxic immune effector functions.

Potential adverse effects of cyclosporin A on kidneys after spinal cord injury

STUDY DESIGN

Cell transplantation strategies are gaining increasing interest for spinal cord injury (SCI) with the objective of promoting spinal cord repair. To avoid allogenic graft rejection, an adequate immune suppression is required, and one of the most potent and commonly used immunosuppressives is cyclosporin A (CsA). In SCI, permanent sensory motor loss is combined with modifications of drug absorption, distribution and elimination.

OBJECTIVES

The objectives of this study were to thoroughly explore histological and functional outcomes of CsA treatment in a rat model of spinal cord compression.

SETTING

Experiments were carried out at the Institute for Neurosciences of Montpellier (France), the Integrative Biology of Neurodegeneration Laboratory (Spain) and in the Novartis Institutes for BioMedical Research (Switzerland) for CsA blood concentration determination.

METHODS

We first evaluated histological outcomes of CsA treatment on kidneys and spinal cord after SCI. We then investigated whether SCI modified CsA blood concentration. Finally, using behavioral analysis, we assessed the potential CsA impact on functional recovery.

RESULTS

When spinal-cord-injured rats were treated with a CsA dose of 10 mg kg(-1) per day, we observed deleterious effects on kidneys, associated with modifications of CsA blood concentration. Adding an antibiotic treatment reduced kidney alteration without modifying CsA blood concentration. Finally, we showed that CsA treatment per se modified neither functional recovery nor lesion extension.

CONCLUSION

This study pinpoints the absolute requirement of careful CsA monitoring in the clinical setting for patients with SCI to minimize potential unexpected effects and avoid therapeutic failure.

Wnt/Ca2+/NFAT signaling maintains survival of Ph+ leukemia cells upon inhibition of Bcr-Abl

Although Bcr-Abl kinase inhibitors have proven effective in the treatment of chronic myeloid leukemia (CML), they generally fail to eradicate Bcr-Abl(+) leukemia cells. To identify genes whose inhibition sensitizes Bcr-Abl(+) leukemias to killing by Bcr-Abl inhibitors, we performed an RNAi-based synthetic lethal screen with imatinib mesylate in CML cells. This screen identified numerous components of a Wnt/Ca(2+)/NFAT signaling pathway. Antagonism of this pathway led to impaired NFAT activity, decreased cytokine production, and enhanced sensitivity to Bcr-Abl inhibition. Furthermore, NFAT inhibition with cyclosporin A facilitated leukemia cell elimination by the Bcr-Abl inhibitor dasatinib and markedly improved survival in a mouse model of Bcr-Abl(+) acute lymphoblastic leukemia (ALL). Targeting this pathway in combination with Bcr-Abl inhibition could improve treatment of Bcr-Abl(+) leukemias.

Pharmacodynamic monitoring of calcineurin inhibition therapy: principles, performance, and perspectives

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.

Performance evaluation of the new ADVIA Centaur system cyclosporine assay (single-step extraction)

BACKGROUND

Cyclosporine (CsA) monitoring is essential for transplant success. We report a performance study of the recently released, fully automated Siemens ADVIA Centaur CsA assay.

METHODS

Whole blood samples from 248 transplant patients were prepared using a new 1-step extraction method. Performance evaluations vs. HPLC-tandem MS (LC-MS/MS), Abbott TDx and AxSYM assays were conducted according to CLSI EP5-A2 and EP9-A2 guidelines.

RESULTS

The correlation coefficient for LC-MS/MS and ADVIA Centaur was > or = 0.97 at each site, and for each transplant type. Regression analysis yielded y=0.94x+19 for all sites: 95% CI=0.91-0.96 (slope) and 10-28 (intercept). Absolute and relative bias was minimal for C0 and C2 sampling. Centaur vs. Abbott TDx and AxSYM assays: y = 0.72x+6, r = 0.98, 95% CI = 0.70-0.73 (slope), 3-9 (intercept); and y = 0.69x+18, r = 0.97, 95% CI = 0.67-0.71 (slope), 8-27(intercept). Within run CVs were 4.5%-7.1%, total CVs were 5.3%-7.7%.

CONCLUSIONS

The ADVIA Centaur assay compared favorably with LC-MS/MS and Abbott assays, displaying good correlation for all transplant types and methods.

Pharmacogenetics of calcineurin inhibitors in renal transplantation

Cyclosporine A and tacrolimus (Tac) are inmunosuppresive drugs with a narrow therapeutic range. Underdosing is associated with organ rejection, whereas overdosing could result in toxicity. Therapeutic drug monitoring at different postdose times is necessary to maintain the blood concentrations within a target window. These calcineurin inhibitors are characterized by a broad interindividual pharmacokinetics variability, which makes the determination of the initial dose difficult. In a patient receiving a dose, the amount of the drug that is measured in the blood determines its bioavailability, which depends on the absorption, biotransformation, and elimination of the drug. These processes are primarily controlled by efflux pumps and enzymes of the cytochrome P (CYP) 450 family. DNA variants at the genes encoding these proteins contribute to the interindividual heterogeneity for calcineurin inhibitors metabolism. Cyclosporine A and Tac are metabolized by CYP3A4 and CYP3A5, and several single nucleotide polymorphisms in the two genes have been associated with differences in drug clearance. Carriers of the CYP3A5 wild-type allele have a higher CYP3A5 expression compared with individuals who are homozygous for a common DNA variant that affects gene splicing (CYP3A5*3). For renal transplant recipients receiving Tac, homozygotes for this nonexpression allele would exhibit significantly lower Tac clearance and may require a lower dose to remain within the blood target concentration compared with CYP3A5 expressors. To date, this CYP3A5 variant is the only reported genetic factor to predict the appropiate starting dosage of Tac, avoiding overdosing and improving the outcome of renal transplantation.

Low-dose cyclosporine A therapy increases the regulatory T cell population in patients with atopic dermatitis

BACKGROUND

Atopic dermatitis (AD) is a T cell dependent chronic relapsing inflammatory skin disorder successfully treated with cyclosporine A (CsA). Clinical observations indicate that even low-dose CsA therapy is successful in severely affected AD patients. We studied the impact of low-dose CsA therapy on the ability of T helper cells to be activated, and examined whether regulatory T (Treg) cells are increased in these patients.

METHODS

Peripheral T cells were activated in a whole blood sample and interleukin-2 producing cells were measured by intracellular cytokine staining. Regulatory T cells were analyzed by intracellular FoxP3 staining. Regulatory T cells (CD4(+)CD25(+)CD127(low)) and effector T cells (CD4(+)CD25(-)CD127(+)) were sorted by flow cytometry and used for suppression assays.

RESULTS

A group of AD patients treated with low-dose CsA had a significantly larger Treg cell population than a healthy control subject group. In individual patients, onset of low-dose CsA therapy reduced the ability of T cells to be activated to 42 +/- 18% (P < 0.005) and significantly increased Treg cells, both in absolute numbers (1.6-fold change) and frequencies (1.7-fold change). Treg cells from AD patients showed similar suppressive capacities as Treg cells from healthy donors. Furthermore, Treg cells from AD patients had skin homing properties.

CONCLUSION

Our results indicate that the therapeutic effect of low-dose CsA therapy in AD patients might be not only mediated by the inhibition of T cell hyperactivity but also by an increased population of Treg cells.

Impact of cyclosporine-A concentration on the incidence of severe acute graft-versus-host disease after allogeneic stem cell transplantation

This single-center retrospective study analyzed 85 consecutive patients who underwent allogeneic stem cell transplantation (allo-SCT) with the aim to assess whether there is a correlation between exposure to cyclosporine-A (CsA; as measured by CsA concentrations during the first month after allo-SCT) and the risk for developing severe grade III-IV acute graft-versus-host disease (aGVHD). The median concentrations of CsA in the blood at 1, 2, 3, and 4 weeks after allo-SCT were 348 (range: 172-733), 284 (range: 137-535), 274 (range: 107-649), and 247 (range: 37-695) ng/mL, respectively. Overall, grade II-IV aGVHD occurred in 36 patients (42%) at a median of 29 (range: 6-100) days after allo-SCT. The incidence of grade III-IV aGVHD (n = 20) was 23% (95% confidence interval [CI], 14%-32%). In univariate analysis, patients receiving allo-SCT from an HLA-matched unrelated donor had a higher risk of grade III-IV aGVHD, and patients having the lowest CsA concentration in the first and second weeks after allo-SCT had a significantly higher risk of grade III-IV aGVHD. In a multivariate logistic regression analysis, a higher CsA concentration measured during the first week following graft infusion was the strongest parameter significantly associated with a reduced risk of severe grade II-IV aGVHD (P = .012; relative risk [RR] = 0.24; 95% CI, 0.08-0.73). Of note, when adjusted by donor type, CsA concentration in week 1 remained significantly associated with risk of severe grade II-IV aGVHD (P = .014). We conclude that precise monitoring of CsA concentrations and adjustment of CsA dose early after allo-SCT may be effective to prevent onset of severe aGVHD.

Pharmacokinetic optimization of immunosuppressive therapy in thoracic transplantation: part I

Although immunosuppressive treatments and therapeutic drug monitoring (TDM) have significantly contributed to the increased success of thoracic transplantation, there is currently no consensus on the best immunosuppressive strategies. Maintenance therapy typically consists of a triple-drug regimen including corticosteroids, a calcineurin inhibitor (ciclosporin or tacrolimus) and either a purine synthesis antagonist (mycophenolate mofetil or azathioprine) or a mammalian target of rapamycin inhibitor (sirolimus or everolimus). The incidence of acute and chronic rejection and of mortality after thoracic transplantation is still high compared with other types of solid organ transplantation. The high allogenicity and immunogenicity of the lungs justify the use of higher doses of immunosuppressants, putting lung transplant recipients at a higher risk of drug-induced toxicities. All immunosuppressants are characterized by large intra- and interindividual variability of their pharmacokinetics and by a narrow therapeutic index. It is essential to know their pharmacokinetic properties and to use them for treatment individualization through TDM in order to improve the treatment outcome. Unlike the kidneys and the liver, the heart and the lungs are not directly involved in drug metabolism and elimination, which may be the cause of pharmacokinetic differences between patients from all of these transplant groups. TDM is mandatory for most immunosuppressants and has become an integral part of immunosuppressive drug therapy. It is usually based on trough concentration (C(0)) monitoring, but other TDM tools include the area under the concentration-time curve (AUC) over the (12-hour) dosage interval or the AUC over the first 4 hours post-dose, as well as other single concentration-time points such as the concentration at 2 hours. Given the peculiarities of thoracic transplantation, a review of the pharmacokinetics and TDM of the main immunosuppressants used in thoracic transplantation is presented in this article. Even more so than in other solid organ transplant populations, their pharmacokinetics are characterized by wide intra- and interindividual variability in thoracic transplant recipients. The pharmacokinetics of ciclosporin in heart and lung transplant recipients have been explored in a number of studies, but less is known about the pharmacokinetics of mycophenolate mofetil and tacrolimus in these populations, and there are hardly any studies on the pharmacokinetics of sirolimus and everolimus. Given the increased use of these molecules in thoracic transplant recipients, their pharmacokinetics deserve to be explored in depth. There are very few data, some of which are conflicting, on the practices and outcomes of TDM of immunosuppressants after thoracic transplantation. The development of sophisticated TDM tools dedicated to thoracic transplantation are awaited in order to accurately evaluate the patients' exposure to drugs in general and, in particular, to immunosuppressants. Finally, large cohort TDM studies need to be conducted in thoracic transplant patients in order to identify the most predictive exposure indices and their target values, and to validate the clinical usefulness of improved TDM in these conditions. In part I of the article, we review the pharmacokinetics and TDM of calcineurin inhibitors. In part II, we will review the pharmacokinetics and TDM of mycophenolate and mammalian target of rapamycin inhibitors, and provide an overall discussion along with perspectives.

Calcineurin inhibitor nephrotoxicity

The use of the calcineurin inhibitors cyclosporine and tacrolimus led to major advances in the field of transplantation, with excellent short-term outcome. However, the chronic nephrotoxicity of these drugs is the Achilles' heel of current immunosuppressive regimens. In this review, the authors summarize the clinical features and histologic appearance of both acute and chronic calcineurin inhibitor nephrotoxicity in renal and nonrenal transplantation, together with the pitfalls in its diagnosis. The authors also review the available literature on the physiologic and molecular mechanisms underlying acute and chronic calcineurin inhibitor nephrotoxicity, and demonstrate that its development is related to both reversible alterations and irreversible damage to all compartments of the kidneys, including glomeruli, arterioles, and tubulo-interstitium. The main question--whether nephrotoxicity is secondary to the actions of cyclosporine and tacrolimus on the calcineurin-NFAT pathway--remains largely unanswered. The authors critically review the current evidence relating systemic blood levels of cyclosporine and tacrolimus to calcineurin inhibitor nephrotoxicity, and summarize the data suggesting that local exposure to cyclosporine or tacrolimus could be more important than systemic exposure. Finally, other local susceptibility factors for calcineurin inhibitor nephrotoxicity are reviewed, including variability in P-glycoprotein and CYP3A4/5 expression or activity, older kidney age, salt depletion, the use of nonsteroidal anti-inflammatory drugs, and genetic polymorphisms in genes like TGF-beta and ACE. Better insight into the mechanisms underlying calcineurin inhibitor nephrotoxicity might pave the way toward more targeted therapy or prevention of calcineurin inhibitor nephrotoxicity.

Monitoring immunosuppression with measures of NFAT decreases cancer incidence

Long-term immunosuppression causes a significantly increased risk for the development of malignancies in transplanted patients. A link between immunosuppression and incidence of cancer is well documented and involves the effect of immunosuppression on anti-tumor surveillance and antiviral adaptive immune responses. We present a 67-year-old patient with a history of recurrent non-melanoma skin cancer. After adjustment of immunosuppressive therapy under close pharmacodynamic control, the development of new malignant lesions could be prevented. The availability of a quantitative, quick laboratory test for an assessment of the individual functional activity of immunocompetent cells that are crucial for transplant rejection, defense against viral infection, and tumor surveillance along with the ability to adjust doses of immunosuppressive agents such that patients are largely protected against malignant disease and/or viral infection are important. NFAT-regulated gene expression measured in peripheral blood allowed us to predict "safe" immunosuppression. Thus patients could maintain a stable allograft function. This represents a breakthrough in transplantation medicine and advances our attempts to individualize treatment in transplanted patients.

Pharmacodynamic evaluation of the first dose of mycophenolate mofetil before kidney transplantation

BACKGROUND AND OBJECTIVES

The effect of mycophenolate mofetil (MMF) on T cell function has not been evaluated in patients undergoing kidney transplantation. The aim of this study was to assess the effect of 1g of MMF on T cell function, that is, intralymphocyte cytokine expression, T cell activation (CD25 and CD71), and T cell proliferation, as well as inosine monophosphate dehydrogenase (IMPDH) activity, to better understand the relationship between pharmacokinetic and pharmacodynamic markers in patients receiving the first dose of MMF before kidney transplantation.

PATIENTS

Twenty-four patients undergoing a kidney transplantation from a living donor were enrolled in this study.

RESULTS

Compared with baseline (before MMF intake), T cell proliferation (93%), IMPDH activity (74%), CD25 (46%), and CD71 (50%) expression significantly decreased during the first hour after MMF intake, in parallel to the rise in MPA concentration. Thereafter, all pharmacodynamic markers, except IMPDH activity, returned back to baseline level. There was a complex inverse relationship between pharmacokinetic and pharmacodynamic markers. The inhibition of T cell proliferation was highly correlated to IMPDH activity, but also to T cell activation markers.

CONCLUSION

The administration of MMF to patients is associated not only with a dramatic decrease in both T cell proliferation and IMPDH activity, but also with in a decrease in CD25 and CD71 expression.

Temporal profile of calcineurin phosphatase activity during acute allograft rejection in the heterotopic rat heart transplantation model

BACKGROUND

Regardless of the extensive worldwide use of calcineurin inhibitors, little is known about the behavior of calcineurin phosphatase (CaN) during acute allograft rejection. The aim of this study was to investigate the temporal profile of CaN during acute allograft rejection and reveal if it can be utilized as a pharmacodynamic marker to identify and monitor the rejection process.

METHODS

The heterotopic cervical rat heart transplantation model was used (dark Agouti to Lewis). We performed 25 control isogeneic and 46 allogeneic transplantations. Rats were sacrificed at various postoperative time points. CaN activity was measured in isolated peripheral blood and spleen mononuclear cells and in graft heart homogenates. CaN activity was measured as the release of radiolabeled phosphate from a previously phosphorylated 19 amino acid peptide.

RESULTS

We have shown that CaN's activity levels are not significantly altered during acute allograft rejection in peripheral blood mononuclear cells and in spleen-isolated mononuclear cells. CaN's intragraft activity decreased with time in both rejectors and controls, and was significantly lower in the allogeneic group.

CONCLUSIONS

CaN failed as a pharmacodynamic biomarker of acute allograft rejection in the heterotopic rat heart transplantation model. Further research is required in order to reveal the precise role of CaN during acute allograft rejection.

Calcineurin inhibition in splenocytes induced by pavlovian conditioning

Pavlovian conditioning is one of the major neurobiological mechanisms of placebo effects, potentially influencing the course of specific diseases and the response to a pharmacological therapy, such as immunosuppression. In our study with behaviorally conditioned rats, a relevant taste (0.2% saccharin) preceded the application of the immunosuppressive drug cyclosporin A (CsA), a specific calcineurin (CaN) inhibitor. Our results demonstrate that through pavlovian conditioning the particular pharmacological properties of CsA can be transferred to a neutral taste, i.e., CaN activity was inhibited in splenocytes from conditioned rats after reexposure to the gustatory stimulus. Concomitant immune consequences were observed on ex vivo mitogenic challenge (anti-CD3). Particularly, Th1-cytokine, but not Th2-cytokine, production and cell proliferation were impeded. Appropriate pharmacological and behavioral controls certify that all these changes in T-lymphocyte reactivity are attributable to mere taste reexposure. Furthermore, the underlying sympathetic-lymphocyte interaction was revealed modeling the conditioned response in vitro. CaN activity in CD4(+) T lymphocytes is reduced by beta-adrenergic stimulation (terbutaline), with these effects antagonized by the beta-adrenoreceptor antagonist nadolol. In summary, CaN was identified as the intracellular target for inducing conditioned immunosuppression by CsA, contributing to our understanding of the intracellular mechanisms behind "learned placebo effects."

Calcineurin inhibitor sparing in paediatric solid organ transplantation : managing the efficacy/toxicity conundrum

Despite their efficacy, the calcineurin inhibitors (CNIs) ciclosporin and tacrolimus carry a risk of debilitating adverse effects, especially nephrotoxicity, that affect the long-term outcome and survival of children who are given organ transplants. Simple reduction in dosage of CNI has little or no long-term benefit on their adverse effects, and complete withdrawal without threatening graft outcome may only be possible after liver transplantation. Until the last decade, the only option was to increase corticosteroid and/or azathioprine doses, which imposed additional long-term hazards. Considered here are the emerging generation of new agents offering an opportunity for improving long-term graft survival, minimizing CNI-related adverse events and ensuring patient well-being.A holistic, multifaceted strategy may need to be considered - initial selection and optimized use and monitoring of immunosuppressant regimens, early recognition of indicators of patient and graft dysfunction, and, where applicable, early introduction of CNI-sparing regimens facilitating CNI withdrawal. The evidence reviewed here supports these approaches but remains far from definitive in paediatric solid organ transplantation. Because de novo immunosuppression uses CNI in more than 93% of patients, reduction of CNI-related adverse effects has focused on CNI sparing or withdrawal.A recurring theme where sirolimus and mycophenolate mofetil have been used for this purpose is the importance of their early introduction to limit CNI damage and provide long-term benefit: for example, long-term renal function critically reflects that at 1 year post-transplant. While mycophenolic acid shows advantages over sirolimus in preserving renal function because the latter is associated with proteinuria, sirolimus appears the more potent immunosuppressant but also impairs early wound healing. The use of CNI-free immunosuppressant regimens with depleting or non-depleting antibodies plus sirolimus and mycophenolic acid needs much wider investigation to achieve acceptable rejection rates and conserve renal function. The adverse effects of the alternative immunosuppressants, particularly the dyslipidaemia associated with sirolimus, needs to be minimized to avoid replacing one set of adverse effects (from CNIs) with another. While we can only conjecture that judicious combinations with the second generation of novel immunosuppressants currently in development will provide these solutions, a rationale of low-dose therapy with multiple immunosuppressants acting by complementary mechanisms seems to hold the promise for efficacy with minimal toxicity until the vision of tolerance achieves reality.

Therapeutic equivalence and mg:mg switch ability of a generic cyclosporine microemulsion formulation (Sigmasporin Microral) in stable renal transplant patients maintained on Sandimmun Neoral

We tested a hypothesized pharmacokinetic difference between the reference (Sandimmun Neoral) and test (Sigmasporin Microral) products to prove therapeutic equivalence in an open, multiple fixed dose, one-way crossover, multicenter, and multinational study over a period of 29 days. Forty two stable renal transplant recipients maintained on Sandimmun Neoral were enrolled. Whole blood was collected at day 14 of the study at 0, 0.5, 1.0, 1.5, 2, 3, 4, 5, 6, 8, 10, and 12 hours after reference dosing and the same schedule was repeated at day 29 after switching on an mg:mg basis to the test product at day 15 of the study. Analysis of variance was performed for the pharmacokinetic parameters (area under the curve [AUC]0-12, maximum concentration [Cmax]) of cyclosporine using log-transformed values. Tolerability was assessed by vital signs, adverse events, and laboratory investigations. The 90% confidence interval (CI) test for the Ln-transformed, pharmacokinetic parameters was all within the US Food and Drug Administration acceptable range of 80% to 125%, as Ln area under the steady-state curve (AUCss) was within the range of 92.56 to 103.55 and Ln Cmax was within the range of 85.73 to 103.58; the same also applied for AUC0-4, which may be considered the area of greatest inter- and intra-patient variability. Furthermore, in line with the newly adopted recommendations of the Expert Advisory Committee on Bioavailability and Bioequivalence of Health Canada, the 90% CI for AUCss was within the narrow range of 90% to 112%. No significant difference in tolerability was recorded between the two products. Sigmasporin Microral (Julphar) was found to be bioequivalent and clinically interchangeable on an mg:mg basis with Sandimmun Neoral (Novartis).

[Therapeutic monitoring of immunosuppressive drugs: interest of calcineurin activity assessment in liver transplantation]

Therapeutic monitoring of calcineurin inhibitors (ciclosporin and tacrolimus) consists in pharmacokinetic monitoring. Pharmacodynamics based on calcineurin activity may be particularly interesting in liver transplantation due to the large intra- and interindividual variability of pharmacokinetics of ciclosporin and tacrolimus. A recent investigation on the pharmacokinetic-pharmacodynamic relationship of tacrolimus showed that monitoring of calcineurin activity in PBMC may be particularly relevant within the first three post-transplantation months. Thereafter, the monitoring of trough blood concentrations of tacrolimus remains adequate. Moreover, two clinical investigations carried out within the early and late post-transplantation periods reported a promising result which is a positive correlation between calcineurin activity and incidence of graft rejection, whatever graft type and calcineurin inhibitors. In each study, transplanted recipients with a graft rejection exhibited a greater trough calcineurin activity compared to patients without graft rejection. However, prospective investigations are required because of the small cohorts of patients enrolled in both studies. The aim of these investigations will be to confirm the interest of calcineurin activity monitoring as a marker of cellular immunity and its positive link with pharmacokinetic monitoring.