Everolimus in pediatric de nova renal transplant patients

Everolimus Personalized Therapy: Second Consensus Report by the International Association of Therapeutic Drug Monitoring and Clinical Toxicology

ABSTRACT

The Immunosuppressive Drugs Scientific Committee of the International Association of Therapeutic Drug Monitoring and Clinical Toxicology established the second consensus report to guide Therapeutic Drug Monitoring (TDM) of everolimus (EVR) and its optimal use in clinical practice 7 years after the first version was published in 2016. This version provides information focused on new developments that have arisen in the last 7 years. For the general aspects of the pharmacology and TDM of EVR that have retained their relevance, readers can refer to the 2016 document. This edition includes new evidence from the literature, focusing on the topics updated during the last 7 years, including indirect pharmacological effects of EVR on the mammalian target of rapamycin complex 2 with the major mechanism of direct inhibition of the mammalian target of rapamycin complex 1. In addition, various concepts and technical options to monitor EVR concentrations, improve analytical performance, and increase the number of options available for immunochemical analytical methods have been included. Only limited new pharmacogenetic information regarding EVR has emerged; however, pharmacometrics and model-informed precision dosing have been constructed using physiological parameters as covariates, including pharmacogenetic information. In clinical settings, EVR is combined with a decreased dose of calcineurin inhibitors, such as tacrolimus and cyclosporine, instead of mycophenolic acid. The literature and recommendations for specific organ transplantations, such as that of the kidneys, liver, heart, and lungs, as well as for oncology and pediatrics have been updated. EVR TDM for pancreatic and islet transplantation has been added to this edition. The pharmacodynamic monitoring of EVR in organ transplantation has also been updated. These updates and additions, along with the previous version of this consensus document, will be helpful to clinicians and researchers treating patients receiving EVR.

Induction and maintenance immunosuppression in pediatric kidney transplantation-Advances and controversies

Advances in immunosuppression have improved graft survival in pediatric kidney transplant recipients; however, treatment-related toxicities need to be balanced against the possibility of graft rejection. Several immunosuppressive agents are available for use in transplant recipients; however, the optimal combinations of agents remain unclear, resulting in variations in institutional protocols. Lymphocyte-depleting antibodies, specifically ATG, are the most common induction agent used for pediatric kidney transplantation in the US. Basiliximab may be used for induction in immunologically low-risk children; however, pediatric data are scarce. CNIs and antiproliferative agents (mostly Tac and mycophenolate in recent years) constitute the backbone of maintenance immunosuppression. Steroid-avoidance maintenance regimens remain controversial. Belatacept and mTOR inhibitors are used in children under specific circumstances such as non-adherence or CNI toxicity. This article reviews the indications, mechanism of action, efficacy, dosing, and side effect profiles of various immunosuppressive agents available for pediatric kidney transplantation.

Current developments in pediatric liver transplantation

In 1953, the pioneer of human orthotopic liver transplantation (LT), Thomas E Starzl, was the first to attempt an orthotopic liver transplant into a 3 years old patient suffering from biliary atresia. Thus, the first LT in humans was attempted in a disease, which, up until today, remains the main indication for pediatric LT (pLT). During the last sixty years, refinements in diagnostics and surgical technique, the introduction of new immunosuppressive medications and improvements in perioperative pediatric care have established LT as routine procedure for childhood acute and chronic liver failure as well as inherited liver diseases. In contrast to adult recipients, pLT differs greatly in indications for LT, allocation practice, surgical technique, immunosuppression and post-operative life-long aftercare. Many aspects are focus of ongoing preclinical and clinical research. The present review gives an overview of current developments and the clinical outcome of pLT, with a focus on alternatives to full-size deceased-donor organ transplantation.

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.

The role of everolimus in liver transplantation

During the last 5 decades, liver transplantation has witnessed rapid development in terms of both technical and pharmacologic advances. Since their discovery, calcineurin inhibitors (CNIs) have remained the standard of care for immunosuppression therapy in liver transplantation, improving both patient and graft survival. However, adverse events, particularly posttransplant nephrotoxicity, associated with long-term CNI use have necessitated the development of alternate treatment approaches. These include combination therapy with a CNI and the inosine monophosphate dehydrogenase inhibitor mycophenolic acid and use of mammalian target of rapamycin (mTOR) inhibitors. Everolimus, a 40-O-(2-hydroxyethyl) derivative of mTOR inhibitor sirolimus, has a distinct pharmacokinetic profile. Several studies have assessed the role of everolimus in liver transplant recipients in combination with CNI reduction or as a CNI withdrawal strategy. The efficacy of everolimus-based immunosuppressive therapy has been demonstrated in both de novo and maintenance liver transplant recipients. A pivotal study in 719 de novo liver transplant recipients formed the basis of the recent approval of everolimus in combination with steroids and reduced-dose tacrolimus in liver transplantation. In this study, everolimus introduced at 30 days posttransplantation in combination with reduced-dose tacrolimus (exposure reduced by 39%) showed comparable efficacy (composite efficacy failure rate of treated biopsy-proven acute rejection, graft loss, or death) and achieved superior renal function as early as month 1 and maintained it over 2 years versus standard exposure tacrolimus. This review provides an overview of the efficacy and safety of everolimus-based regimens in liver transplantation in the de novo and maintenance settings, as well as in special populations such as patients with hepatocellular carcinoma recurrence, hepatitis C virus-positive patients, and pediatric transplant recipients. We also provide an overview of ongoing studies and discuss potential expansion of the role for everolimus in these settings.

Growing experience with mTOR inhibitors in pediatric solid organ transplantation

Controlled trials of mTOR inhibitors in children following solid organ transplantation are scarce, although evidence from prospective single-arm studies is growing. Everolimus with reduced CNI therapy has been shown to be efficacious and safe in de novo pediatric kidney transplant patients in prospective trials. Prospective and retrospective data in children converted from CNI therapy to mTOR inhibition following kidney, liver, or heart transplantation suggest preservation of immunosuppressive efficacy. Good renal function has been maintained when mTOR inhibitors are used de novo in children following kidney transplantation or after conversion to mTOR inhibition with CNI minimization. mTOR inhibition with reduced CNI exposure is associated with a low risk for developing infection in children. Growth and development do not appear to be impaired during low-dose mTOR inhibition, but more studies are required. No firm conclusions can be drawn as to whether mTOR inhibitors should be discontinued in children requiring surgical intervention or whether mTOR inhibition delays progression of hepatic fibrosis after pediatric liver transplantation. In conclusion, current evidence suggests that use of mTOR inhibitors in children undergoing solid organ transplantation is efficacious and safe, but a number of issues remain unresolved and further studies are required.

De novo therapy with everolimus and reduced-exposure cyclosporine following pediatric kidney transplantation: a prospective, multicenter, 12-month study

Prospective data regarding the de novo use of everolimus following kidney transplantation in children are sparse. In a prospective, 12-month, single-arm, open-label study, pediatric kidney transplant patients received everolimus (target trough concentration ≥3 ng/mL) with reduced-exposure CsA and corticosteroids, with or without basiliximab induction. Sixteen of the 18 patients completed the study on-treatment. Age range was 2-16 yr (mean 10.9 yr); eight patients received a living donor graft. Mean (s.d.) everolimus level was 7.4 (3.1) ng/mL during the first 12 months post-transplant. There were no cases of BPAR, graft loss, or death during the study. Protocol biopsies were performed at month 12 in seven patients, with subclinical (untreated) acute rejection diagnosed in one case. Mean (s.d.) estimated GFR (Schwartz formula) was 98 (34) mL/min/1.73 m(2) at month 12. Three patients experienced one or more serious adverse events with a suspected relation to study medication. One patient discontinued study medication due to post-transplant lymphoproliferative disease (5.6%). Everolimus with reduced-dose CsA and corticosteroids achieved good efficacy and renal function and was well tolerated in this small cohort of pediatric kidney transplant patients. Controlled trials are required to answer remaining questions about the optimal use of everolimus in this setting.

Postoperative care of the transplanted patient

The successful delivery of optimal peri-operative care to pediatric heart transplant recipients is a vital determinant of their overall outcomes. The practitioner caring for these patients must be familiar with and treat multiple simultaneous issues in a patient who may have been critically ill preoperatively. In addition to the complexities involved in treating any child following cardiac surgery, caretakers of newly transplanted patients encounter multiple transplant-specific issues. This chapter details peri-operative management strategies, frequently encountered early morbidities, initiation of immunosuppression including induction, and short-term outcomes.

Renal function in children with heart transplantation after switching to CNI-free immunosuppression with everolimus

Renal impairment because of CNI contributes to long-term morbidity. Therefore, CNI avoiding or sparing treatment strategies are important. In this article, we describe the results of a CNI-free treatment protocol with regard to recovery of renal function. Twenty-eight patients with heart transplantation were switched from CNI regimen to everolimus and mycophenolate, when cGFR was <75 mL/min/1.73 m(2). In all patients, CNI was stopped, when everolimus trough levels of 5-8 ng/L were achieved. Serum creatinine and cGFR were determined before and after 6 and 12 months. Median serum creatinine decreased from 1.2 mg/dL (range 0.7-3.7) before everolimus to 1.0 (range 0.6-1.8) and 1.0 (range 0.5-1.9) mg/dL after 6 and 12 months. Median cGFR was 47.81 (range 18.3-72.6) mL/min/1.73 m(2) before everolimus and 63.1 (range 37.8-108.7) mL/min/1.73 m(2) at six months and 64.8 (range 37.7-106.6) mL/min/1.73 m(2) after 12 months. All changes from baseline to six and 12 months were statistically significant (p < 0.05). Adverse events were infections (n = 3) and rejections (n = 3). Therapy was discontinued in four patients. Conversion to CNI-free immunosuppression resulted in significant improvements of renal function within six months of CNI withdrawal. Side effects are common. However, more studies are required to demonstrate the effectiveness in children.

The use of everolimus in pediatric liver transplant recipients: first experience in a single center

The role of mTOR inhibitors, such as EVL, has not been established for pediatric liver transplant recipients up to now, although data from adult solid organ graft transplantation are very promising. Major complications following pediatric liver transplantation in the long-term course include chronic graft rejection and CNI-derived nephrotoxicity. The purpose of our study was to report first results using EVL as a rescue therapy in pediatric liver transplant recipients for the following indications: chronic graft dysfunction n=12, suspected CNI toxicity n=3, hepatoblastoma n=2, and recurrence of primary sclerosing cholangitis post-Ltx n=1. Four patients with chronic graft dysfunction developed completely normal liver function tests using EVL, six patients showed partial improvement, and two patients did not respond at all. One patient with CNI-induced nephropathy showed a slightly improved GFR. Both patients with hepatoblastoma did not develop any metastasis post-Ltx. First experience with EVL in pediatric liver transplant recipients shows promising results in patients with chronic graft failure when standard immunosuppression has failed. The future role of EVL in immunosuppressive protocols for children post-Ltx has to be proven by controlled clinical trials.

Everolimus: a proliferation signal inhibitor with clinical applications in organ transplantation, oncology, and cardiology

Everolimus, a proliferation signal inhibitor in the mammalian target of rapamycin (mTOR) drug class, has many clinical applications, including in organ transplantation, oncology, and cardiology. It currently has United States Food and Drug Administration (FDA) approval for prophylaxis against rejection in de novo renal transplant recipients, treatment of renal cell carcinoma, and use as a drug-eluting stent. To review the pharmacology, pharmacokinetics, efficacy, and safety of everolimus, we performed a search of the MEDLINE database (January 1997-April 2010) for all English-language articles of in vitro and in vivo studies that evaluated everolimus, as well as abstracts from recent scientific meetings and the manufacturer. In transplantation, everolimus demonstrates immunosuppressive properties and has been used to prevent acute rejection in cardiac, liver, lung, and renal transplant recipients. It appears that this agent may be potent enough to allow for the minimization or removal of calcineurin inhibitors in the long-term management of renal transplant recipients. In oncology, everolimus has been proven effective for the management of treatment-resistant renal cell carcinoma. In cardiology, everolimus is available as a drug-coated stent and is used in percutaneous coronary interventions for prevention of restenosis. In transplant recipients and patients with renal cell carcinoma, everolimus appears to have an extensive adverse-event profile. The pharmacologic properties of everolimus differentiate this agent from other drugs used in these clinical areas, and its pharmacokinetic properties differentiate it from sirolimus.

Pharmacokinetic optimization of immunosuppressive therapy in thoracic transplantation: part II

Part I of this article, which appeared in the previous issue of the Journal, reviewed calcineurin inhibitors--ciclosporin and tacrolimus. In part II, we review the pharmacokinetics and therapeutic drug monitoring of mycophenolate and mammalian target of rapamycin inhibitors--sirolimus and everolimus--in thoracic transplantation, and we provide an overall discussion and suggest various areas for future study.

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.

Recovery of tacrolimus-associated brachial neuritis after conversion to everolimus in a pediatric renal transplant recipient--case report and review of the literature

TAC has been shown to be a potent immunosuppressive agent for solid organ transplantation in pediatrics. Neurotoxicity is a potentially serious toxic effect. It is characterized by encephalopathy, headaches, seizures, or neurological deficits. Here, we describe an eight-and-a-half-yr-old male renal transplant recipient with right BN. MRI demonstrated hyperintense T2 signals in the cervical cord and right brachial plexus roots indicative of both myelitis and right brachial plexitis. Symptoms persisted for three months despite TAC dose reduction, administration of IVIG and four doses of methylprednisolone pulse therapy. Improvement and eventually full recovery only occurred after TAC was completely discontinued and successfully replaced by everolimus.

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.

Everolimus: an update on the mechanism of action, pharmacokinetics and recent clinical trials

BACKGROUND

A growing body of evidence suggests that everolimus might offer effective immunosuppressive activity together with antiproliferative effects that may address some of the unmet needs in the long-term therapeutic management of the post-transplant patient.

OBJECTIVE

To summarize the emerging evidence for employing everolimus-based immunosuppression.

METHODS

A systematic review was conducted of the Medline, Embase and Renal Health Library (Cochrane Collaboration) databases, and of the summary publications from international transplant meetings and congresses during 2000-2008.

RESULTS

This article summarizes this analysis, with special focus on the pharmacokinetic characteristics of everolimus and on the results of its use in renal transplantation. Some data has also been included about the efficacy of the drug in other solid organ transplantation and in tumours.

CONCLUSIONS

Everolimus is an immunosuppressant drug with proven efficacy in transplantation. When used in combination with cyclosporin, better results are obtained in renal function with low cyclosporin doses. Adverse events related to this drug are frequent and lead to moderate dropout rates.

Multicenter trial of everolimus in pediatric renal transplant recipients: results at three year

There are few prospective clinical trials of mTOR inhibitors (or proliferation signal inhibitors) combined with CNI inhibitors in de novo pediatric renal transplantation. Results reported here are from a multicenter, open-label study in de novo pediatric renal transplant patients (<or=16 yr), in which patients received everolimus with cyclosporine and corticosteroids for one yr, then entered an extension study for a further two yr. Nineteen patients completed the one-yr study, of whom three discontinued study medication. Fifteen of the remaining 16 patients entered the extension study, eight of whom were aged <10 yr (Group 1) and seven were aged 10-16 yr (Group 2). Mean daily dose of everolimus during the first 36 months was 1.53 mg/m(2) BSA. Biopsy-proven acute rejection occurred in three patients in Group 2 and in one patient in Group 1. Biopsy-proven chronic allograft rejection was reported in four patients (two in each age group). Graft survival at one yr was 100%; one patient in Group 2 lost their graft subsequently during the extension. For patients entering the extension, patient survival at three yr was 100%. There were three cases of viral infection, including one case of cytomegalovirus infection. At three yr, mean total cholesterol was 5.5 +/- 0.8 mm/L (213 +/- 31 mg/dL) and four patients received statin therapy. Mean serum creatinine at 36 months was 96 +/- 36 microm/L (1.1 +/- 0.4 mg/dL). This is the first long-term prospective study to demonstrate that a regimen of everolimus, cyclosporine, and corticosteroids provides good efficacy, tolerability, and safety in de novo pediatric renal transplant patients.

RAD inhibition of sarcoma growth: implications for laryngeal transplantation

PURPOSE

Laryngeal transplantation has not been widely accepted because of concerns regarding accelerated tumor recurrences in the setting of nonspecific immunosuppression. Allotransplantation could potentially be offered to patients if immunosuppressive therapy could be demonstrated to exert tumor suppressive properties. Preliminary reports have demonstrated an antiproliferative effect of everolimus (RAD), a derivative of the immunosuppressant rapamycin.

MATERIALS AND METHODS

Forty-five 10-week-old inbred C57BL/6N (B6) mice were injected subcutaneously with 1 x 10(6) MCA205 sarcoma cells. On the third postinoculation day, the mice were divided into 4 treatment groups, undergoing daily gavage with RAD at 0, 0.2, 1.0, and 5.0 mg/kg per day for 10 consecutive days. Thereafter, treatment with RAD was discontinued and tumor size was measured every 2 days during treatment and biweekly until sacrifice on the 31st postinoculation day. Whole-blood trough levels (C(min)) were measured for each group.

RESULTS

Mean tumor diameter among the control animals and the mice treated with RAD 0.2 mg/kg per day demonstrated no significant difference (P > .07). Groups treated with RAD 1 and 5 mg/kg per day demonstrated significant growth inhibition between the 7th and the 23rd postinoculation days (P < .0001), with no significant differences being noted between these two groups (P > .09). Mean tumor suppressive whole-blood C(min)'s for the 1 and 5 mg/kg per day groups were 75.6 and 368.9 pg/microL, respectively.

CONCLUSIONS

RAD delivered at immunosuppressive doses of 1 and 5 mg/kg per day resulted in significant growth restriction of a fibrosarcoma in a murine model.

Reversal of loss of glomerular filtration rate in children with transplant nephropathy after switch to everolimus and low-dose cyclosporine A

Until now there have been no good therapeutic options in children with biopsy-proven transplant nephropathy (TN) and loss of glomerular filtration rate (GFR) while receiving cyclosporine A (CsA), mycophenolate mofetil (MMF) and prednisolone (Pred). In 13 kidney transplanted children (mean age 13 yr, SD 4) with CsA/MMF/Pred immunosuppression, renal biopsy revealed significant TN. MMF was discontinued, CsA dose was reduced to 50% and Everolimus was started (1.6 mg/m(2)/day). Pred was stopped in 10 of 13 patients. The mean GFR was 55 mL/min/1.73 m(2) (SD 24) one yr before switch, 45 mL/min/1.73 m(2) (SD 16, p < 0.05) at the time of switch and 47 mL/min/1.73 m(2) (SD 18, p < 0.05) 12 months later. There were no severe side-effects or acute rejections. Lactate dehydrogenase, cholesterol, creatine kinase, and U-albumin/creatinine ratio did not increase significantly. After six months, the mean certican-C0 level was 4.0 microg/L (SD 1.5) and mean CsA-C0 level was 52 ng/mL (SD 23). The GFR of transplanted kidneys in children with TN improved by changing immunosuppression from CsA/MMF/Pred to everolimus and low-dose CsA.

The challenge of renal function in heart transplant children

Renal dysfunction may occur after pediatric heart transplantation and impacts on long-term prognosis. This study aims to review the incidence and mechanisms of chronic nephropathy following heart transplantation, and suggest therapeutic directions. The proportion of pediatric heart-transplant recipients with impaired renal function varies from 22 to 57%, and end-stage renal failure from 3 to 10%, depending on the method used for estimating the glomerular filtration rate. The pathophysiology of renal dysfunction is in part due to calcineurin inhibitor-induced renal vasoconstriction, through activation of the intrarenal renin-angiotensin system, TGF-beta1 upregulation and TGF-beta1 gene polymorphisms. Overproduction of angiotensin II, associated with angiotensin-converting-enzyme genotype, might be associated with poor prognosis and pharmacological factor gene polymorphisms, and may contribute to variation of calcineurine inhibitor exposure in the kidney. Strategies to prevent renal dysfunction include reducing calcineurine inhibitor exposure or delaying calcineurine inhibitor administration from the early post-transplant period. Calcium channel blockers and angiotensin-converting-enzyme inhibitors, blockade of angiotensin II, or anti-TGF-beta1 antibodies might limit nephrotoxicity. No accurate marker can predict the potential of renal lesions to develop. Lowering calcineurine inhibitors levels with immunosuppressive agents that are either less nephrotoxic or non-nephrotoxic should be formally studied. Of high interest is the impact of genetic polymorphism on the development of renal dysfunction.

Chronic allograft nephropathy in paediatric renal transplantation

Chronic allograft nephropathy (CAN) is now the leading cause of renal transplant loss in paediatric transplant recipients. Despite improvements in immunosuppression, which have significantly reduced the incidence of acute rejection, the rates of chronic kidney loss have remained unchanged in paediatric transplant patients over the last 20 years. Chronic allograft nephropathy is a pathological diagnosis of which the key features are tubular atrophy and interstitial fibrosis. More consistent definitions and grading of these through the Banff classification have allowed more rigorous study of the development of chronic allograft nephropathy along with further identification of specific lesions associated with the underlying aetiologies. While initially thought to be primarily due to immune injury, it is now evident that CAN is the end result of a variety of immune and non-immune injuries including ischaemia reperfusion injury, calcineurin inhibitor (CNI) toxicity and infections. Protocol biopsy studies have demonstrated rates of CAN development in children similar to those in adults with comparable underlying pathological processes. This review outlines the current knowledge of CAN within the context of paediatric renal transplantation.

Immunosuppression in pediatric solid organ transplantation: opportunities, risks, and management

The pediatric transplant community stands at a time of unprecedented choice of immunosuppressive agents - and with a legacy of morbidity from those agents used in the previous two decades. This review considers the clinical utility and side-effect profiles of immunosuppressants used widely in current practice (e.g., glucocorticoids, azathioprine, ciclosporin, tacrolimus, mycophenolate, and sirolimus) and those agents which are in increasing use or in evaluation (e.g., IL-2 receptor antibodies, everolimus, FTY720, LEA29Y, and deoxyspergualin). Further consideration is given to the wider drug interactions likely during the use of new immunosuppressant regimens and to our growing awareness of the influences of genetic heterogeneity on drug efficacy and handling. Finally, we consider the new demands being placed on the use of drug monitoring to regulate dosage of this new repertoire of immunosuppressants.

Pharmacogenetic differences and drug-drug interactions in immunosuppressive therapy

With the advent of new immunosuppressants and formulations, the elucidation of molecular targets and the evolution of therapeutic drug monitoring, the field of organ transplantation has witnessed significant reductions in acute rejection rates, prolonged graft survival and improved patient outcome. Nonetheless, challenges persist in the use of immunosuppressive medications. Marked interindividual variability remains in drug concentrations and drug response. As medications with narrow therapeutic indices, variations in immunosuppressant concentrations can result in acute toxicity or transplant rejection. Recent studies have begun to identify factors that contribute to this variability with the promise of tailoring immunosuppressive regimens to the individual patient. These advances have uncovered differences in genetic composition in drug-metabolising enzymes, drug transporters and drug targets. This review focuses on commonly used maintenance immunosuppressants (including cyclosporin, mycophenolate mofetil, tacrolimus, sirolimus, everolimus, azathioprine and corticosteroids), examines current studies on pharmacogenetic differences in drug-metabolising enzymes, drug transporters and drug targets and addresses common drug-drug interactions with immunosuppressant therapies. The potential role of drug-metabolising enzymes in contributing to these drug-drug interactions is briefly considered.

Stable graft function after reduction of calcineurin inhibitor dosage in paediatric kidney transplant patients

BACKGROUND

Chronic calcineurin inhibitor (CNI) toxicity contributes to the development and progression of chronic allograft nephropathy (CAN), which is still the major cause of transplant dysfunction and graft loss. Reduction in dosage of CNI may delay the development of CAN, leading to longer graft survival.

METHODS

Therefore, 19 paediatric kidney transplant patients under immunosuppressive therapy with CNI (12/19 ciclosporin A, CSA, 7/19 tacrolimus, Tac), mycophenolat mofetil and some patients on steroids were included in a prospective study. Over a period of 9 months CNI dosage was stepwise reduced from CSA trough levels of 100-150 ng/ml to 50-70 ng/ml and Tac trough levels of 5-8 ng/ml to 2-3 ng/ml, respectively.

RESULTS

Glomerular filtration rate was stabilized in patients after CSA and Tac reduction. One borderline rejection occurred in a patient prior to reduction of Tac. In patients on CSA, one interstitial cellular rejection (BANFF IA) was noted. Reduction of CNI had no significant effects on blood pressure, lipid status and the infection frequency.

CONCLUSIONS

In paediatric kidney transplant patients, reduction of CNI down to low trough levels stabilizes renal function. However, the risk of acute rejection episodes may be increased. Therefore, further studies based on protocol biopsies within a randomized trial are warranted.

Everolimus (RAD) inhibits in vivo growth of murine squamous cell carcinoma (SCC VII)

OBJECTIVE

Everolimus (RAD) is an mTOR inhibitor closely related to rapamycin. A potent immunosuppressive agent, it has also shown evidence of antineoplastic properties. SCC VII is a spontaneously arising murine squamous cell carcinoma line. This study examines the effect of everolimus on SCC VII proliferation. The data may provide support for the use of everolimus in transplant recipients with a history of malignancy.

METHODS

A dose efficacy study was conducted that used a murine model of intradermal tumor growth and pulmonary metastases. The development of intradermal tumors and pulmonary metastases were studied. Of 80 total mice, 40 received intradermal injection of 1 x 10 SCC VII cells and 40 received intravenous injection of 1 x 10 cells to establish pulmonary metastases. Within each group, animals were subdivided into four subgroups that received 1) 1 mg/kg everolimus twice a day, 2) 0.5 mg/kg everolimus twice a day, 3) 7.5 mg/kg cyclosporine per day, and 4) no treatment. Intradermal tumors were measured three times per week. Animals receiving an intravenous tumor injection were killed after 17 days and pulmonary metastases were quantified. Medication trough levels were measured in all treated animals.

RESULTS

Everolimus showed statistically significant tumor inhibition at 1.0 mg/kg twice a day and 0.5 mg/kg twice a day when compared with animals treated with cyclosporine and with untreated animals (P < .0001). Tumor inhibition was evident in both models studied (intradermal tumors and pulmonary metastasis generation).

CONCLUSIONS

Everolimus provides potent tumor inhibition in animals inoculated with SCC VII cells. Inhibition of both local and distant spread of disease is evident. Although most immunosuppressives are known to potentiate neoplastic disease, this study supports the use of everolimus immunosuppression in the face of prior malignancy. This data has significant implication for laryngeal transplantation after laryngectomy.

Mycophenolate mofetil introduction stabilizes and subsequent cyclosporine A reduction slightly improves kidney function in pediatric renal transplant patients: a retrospective analysis

Chronic allograft nephropathy (CAN) is the major cause of late graft loss. Among others, chronic calcineurin inhibitor toxicity (CNI) contributes to the development of CAN. Therefore, reduction in CNI dosage may delay the development of CAN, leading to longer graft survival. It was the aim of the present retrospective analysis to investigate the effect of mycophenolate mofetil (MMF) addition with subsequent cyclosporine A (CSA) reduction on renal function in pediatric kidney allograft recipients. Seventeen patients (aged 8.3-17.6 yr) with monotherapy with CSA and progressive loss of renal function at a median of 3.4 yr after kidney transplantation were enrolled. After at least three months of MMF treatment, CSA dosage was stepwise reduced to trough levels of 100, 80, and 60 ng/mL. In all patients, introduction of MMF prevented a further decrease of glomerular filtration rate (GFR). The mean GFR 12 months before study enrollment was 96.1+/-24.5 and 71.0+/-21.0 mL/min/1.73 m2 at start of MMF. After introduction of MMF and unchanged CSA dosage GFR was stabilized to 71.1+/-23.8 mL/min/1.73 m2. After CSA reduction to trough levels of 60 ng/mL, GFR was slightly ameliorated up to 76.3+/-24.1 mL/min/1.73 m2. Within the follow-up period, one borderline rejection occurred in a patient in whom the CSA trough level was 60 ng/mL since seven months. In pediatric kidney allograft recipients with progressive loss of renal function reduction of CSA after introduction of MMF may stabilize and even slightly ameliorate renal function.

The Role of Therapeutic Monitoring of Everolimus in Solid Organ Transplantation

Everolimus is a novel proliferation signal inhibitor used in immunosuppressive therapies for the prevention of acute and chronic rejection. A role for everolimus drug monitoring has been suggested because of the potential for improving efficacy and reducing adverse effects. Everolimus has proven efficacy for prevention of rejection in adult de novo renal and cardiac transplant recipients. Similar effects have been shown in pediatric renal transplant patients. Several analytic methods are available to quantify everolimus concentrations. A good relationship exists between everolimus concentration and pharmacological response. Mere clinical monitoring of efficacy is insufficient because clinical presentations of graft rejection vary for each patient and are nonspecific. Thus, the authors have used a previously published 9-step decision-making algorithm to evaluate the utility of therapeutic drug monitoring for everolimus. The recommended therapeutic range for everolimus is a trough concentration of 3 to 8 ng/mL, as concentrations over 3 ng/mL have been associated with a decreased incidence of rejection, and concentrations >8 ng/mL with increased toxicity. Everolimus exhibits interindividual pharmacokinetic variability. African American patients have higher apparent clearance, whereas patients with hepatic dysfunction or those on concomitant medications with potent cytochrome P450 (CYP) 3A4 inhibitor or inducer properties have lower or higher apparent clearance, respectively. Solid organ transplant recipients will likely be maintained on immunosuppressant therapy for the life of the graft and/or recipient and thus are likely to benefit from clinical pharmacokinetic monitoring. Based on the available evidence, therapeutic drug monitoring for everolimus may provide additional information on efficacy and safety than sound clinical judgment alone. Patients on everolimus who have problems with absorption, who take concurrent cytochrome P450 inhibitors or inducers, or are noncompliant will attain the greatest benefit from drug monitoring.

Mammalian target of rapamycin (mTOR) inhibition in chronic lymphocytic B-cell leukemia: a new therapeutic option

Chronic lymphocytic B-cell leukemia (B-CLL) is an incurable disease characterized by the accumulation of monoclonal mature B cells, although disease progression relies upon cycling B-CLL cells in proliferation centers in central lymph organs. Rapamycin and its analogs are immunosuppressant drugs that exert their activity by specific inhibition of the mammalian target of rapamycin (mTOR). mTOR inhibition induces cell cycle arrest not only in normal lymphocytes but also in malignant cells. Therefore, rapamycins have recently entered the field of cancer treatment. In the present review we discuss how progression through the cell cycle is regulated in B-CLL cells and how rapamycin and its analogs can be used as target therapies against proliferating B-CLL cells. We also focus on additional effects of rapamycin, such as targeting the interaction between malignant B cells and the microenvironment.

Two-Hour Postdose Concentration: A Reliable Marker for Cyclosporine Exposure in Adolescents With Stable Renal Transplants

In pediatric renal transplant recipients, most patients receive maintenance treatment with cyclosporine (CsA) and mycophenolate mofetil (MMF). Until now, the 2-hour postdose CsA target level for combined maintenance treatment with MMF has not been defined. This prospective pilot study evaluated the pharmacokinetics of CsA under the influence of MMF to determine a reliable single CsA concentration time that correlates with the area under the curve (AUC(0-6h)) estimates for adolescents who were additionally treated with MMF during the late posttransplant period. The study included 13 adolescents (mean posttransplantation time, 3.5 +/- 2.55 years) with stable renal transplant function (S-Crea 121 +/- 40 micromol/L). CsA pharmacokinetic absorption profiles over a 6-hour dose interval (n = 26) were evaluated for the optimal single peak concentration using the CsA concentrations predose (C0) and at 1, 2, 3, 4, and 6 hours postdose (C1-6). Whereas C2 (mean 743.2 +/- 221.8 ng/mL) was the single point with the closest correlation to AUC(0-6h) (r2 = 0.86; P < .001), C0 (mean 120.5 +/- 35.2 ng/mL) showed the weakest correlation (r2 = 0.61, P = .002). C2 appears to be an accurate predictor of CsA exposure in adolescent kidney transplant recipients under maintenance immunosuppression in combination with MMF. Average values achieved with current dosing practices cluster around the target C2 ranges recommended for adults. The data provide a foundation for initiation of prospective clinical trials to assess the long-term risk for chronic allograft dysfunction among pediatric stable renal transplant patients in combination protocols.

Immunosuppressant Drug Monitoring: Is the Laboratory Meeting Clinical Expectations?

OBJECTIVE:

To review the literature relating to immunosuppressant drug measurement as performed in therapeutic drug monitoring laboratories associated with transplantation centers and consider whether the assay methods widely used for patient dosage management achieve acceptable quality criteria in the context of other sources of variability with these drugs.

DATA SOURCES:

Articles used were accessed primarily through MEDLINE, as well as references cited in related publications. Searches were restricted to organ transplantation in humans.

STUDY SELECTION AND DATA EXTRACTION:

Emphasis was placed on the literature relating to the quality of immunosuppressant drug assays, their limitations, and evidence of clinical benefit in dosage individualization.

DATA SYNTHESIS:

There is a dilemma evident between the quality of the analytical services offered by some diagnostic immunoassay manufacturers and the ability of a significant number of clinical laboratories globally to select only appropriate assay methods.

CONCLUSIONS:

In many cases, clinical laboratories fail to meet the reasonable clinical expectations required for interpretation of immunosuppressant drug assay results as an adjunct to optimal dosage individualization and patient care.

What is the calcineurin inhibitor of choice for pediatric renal transplantation?

Cyclosporine microemulsion (CyA) and tacrolimus (Tac) are the principal immunosuppressants prescribed for adult and pediatric renal transplantation. In the majority of patients, these calcineurin inhibitors have been used in combination with other immunosuppressive drugs, such as azathioprine or mycophenolate mofetil (MMF). In this review we will address the question of what calcineurin inhibitor we should use in an individual pediatric renal transplant patient. Well-designed randomized studies in children showed no difference in short-term patient and graft survival with cyclosporine microemulsion and tacrolimus. However Tac is significantly more effective than CyA microemulsion in preventing acute rejection after renal transplantation in a pediatric population when used in conjunction with azathioprine and corticosteroids. This difference disappears when calcineurin inhibitors are used in combination with MMF as both Tac and CyA produce similar rejection rates and graft survival. However, Tac is associated with improved graft function at 1 and 2 yr post-transplant. Adverse events of hypomagnesaemia and diarrhea seem to be higher in Tac group whereas hypertrichosis, flu syndrome and gum hyperplasia occurs more frequently in the CyA group. The incidence of post-transplant diabetes mellitus was almost identical between Tac and CyA treated patients. The recommendation drawn from the available data is that both CyA and Tac can be used safely and effectively in children. However Tac may be preferable to CyA because of steroid sparing effect and less hirsutism. We recommend that cyclosporine should be chosen when patients experience Tac-related adverse events. Nevertheless, the best calcineurin inhibitor should be decided on individual patients according to variable risk factors, such as risk of rejection in sensitized patient or delayed graft function. The possibility of adverse events should also be considered.

Clinical pharmacokinetics of everolimus

Everolimus is an immunosuppressive macrolide bearing a stable 2-hydroxyethyl chain substitution at position 40 on the sirolimus (rapamycin) structure. Everolimus, which has greater polarity than sirolimus, was developed in an attempt to improve the pharmacokinetic characteristics of sirolimus, particularly to increase its oral bioavailability. Everolimus has a mechanism of action similar to that of sirolimus. It blocks growth-driven transduction signals in the T-cell response to alloantigen and thus acts at a later stage than the calcineurin inhibitors ciclosporin and tacrolimus. Everolimus and ciclosporin show synergism in immunosuppression both in vitro and in vivo and therefore the drugs are intended to be given in combination after solid organ transplantation. The synergistic effect allows a dosage reduction that decreases adverse effects. For the quantification of the pharmacokinetics of everolimus, nine different assays using high performance liquid chromatography coupled to an electrospray mass spectrometer, and one enzyme-linked immunosorbent assay, have been developed. Oral everolimus is absorbed rapidly, and reaches peak concentration after 1.3-1.8 hours. Steady state is reached within 7 days, and steady-state peak and trough concentrations, and area under the concentration-time curve (AUC), are proportional to dosage. In adults, everolimus pharmacokinetic characteristics do not differ according to age, weight or sex, but bodyweight-adjusted dosages are necessary in children. The interindividual pharmacokinetic variability of everolimus can be explained by different activities of the drug efflux pump P-glycoprotein and of metabolism by cytochrome P450 (CYP) 3A4, 3A5 and 2C8. The critical role of the CYP3A4 system for everolimus biotransformation leads to drug-drug interactions with other drugs metabolised by this cytochrome system. In patients with hepatic impairment, the apparent clearance of everolimus is significantly lower than in healthy volunteers, and therefore the dosage of everolimus should be reduced by half in these patients. The advantage of everolimus seems to be its lower nephrotoxicity in comparison with the standard immunosuppressants ciclosporin and tacrolimus. Observed adverse effects with everolimus include hypertriglyceridaemia, hypercholesterolaemia, opportunistic infections, thrombocytopenia and leucocytopenia. Because of the variable oral bioavailability and narrow therapeutic index of everolimus, blood concentration monitoring seems to be important. The excellent correlation between steady-state trough concentration and AUC makes the former a simple and reliable index for monitoring everolimus exposure. The target trough concentration of everolimus should range between 3 and 15 microg/L in combination therapy with ciclosporin (trough concentration 100-300 microg/L) and prednisone.

Mammalian target of rapamycin inhibition as therapy for hematologic malignancies

The mammalian target of rapamycin (mTOR) is a downstream effector of the phosphatidylinositol 3-kinase (PI3K)/Akt (protein kinase B) signaling pathway, which mediates cell survival and proliferation. mTOR regulates essential signal-transduction pathways, is involved in the coupling of growth stimuli with cell cycle progression, and initiates mRNA translation in response to favorable nutrient environments. mTOR is involved in regulating many aspects of cell growth, including membrane traffic, protein degradation, protein kinase C signaling, ribosome biogenesis, and transcription. Because mTOR activates both the 40S ribosomal protein S6 kinase (p70s6k) and the eukaryotic initiation factor 4E-binding protein 1, its inhibitors cause G1-phase cell cycle arrest. Inhibitors of mTOR also prevent cyclin dependent kinase (CDK) activation, inhibit retinoblastoma protein phosphorylation, and accelerate the turnover of cyclin D1, leading to a deficiency of active CDK4/cyclin D1 complexes, all of which may help cause G1-phase arrest. It is known that the phosphatase and tensin homologue tumor suppressor gene (PTEN) plays a major role in embryonic development, cell migration, and apoptosis. Malignancies with PTEN mutations, which are associated with constitutive activation of the PI3K/Akt pathway, are relatively resistant to apoptosis and may be particularly sensitive to mTOR inhibitors. Rapamycin analogs with relatively favorable pharmaceutical properties, including CCI-779, RAD001, and AP23573, are under investigation in patients with hematologic malignancies.

Is everolimus useful in preventing allograft rejection and vasculopathy after heart transplant?

The main cause of illness and death after the first year of heart transplantation is vasculopathy of the cardiac allograft, probably initiated by early immunological and non-immunological endothelial damage. The incidence of multiple episodes of grade 3A rejection 6 months after primary heart transplantation was lower with everolimus (1.5 mg, 8.1% and 3 mg, 6.6%) than in the azathioprine group (14%). Allograft vasculopathy was less frequent with everolimus than azathioprine. A follow-up study is necessary to determine whether these effects translate into the important end points of reduced incidences of death, graft loss or a second transplantation.

The impact of cyclosporine on the development of immunosuppressive therapy—pediatric transplantation using cyclosporine

Cyclosporine A (CsA) was introduced to pediatric renal transplantation more than 20 years ago, and it has greatly improved graft survival and made transplantation the treatment of choice for children with end-stage renal failure. Exposure to CsA was shown to be highly variable among transplant recipients. Therefore, major efforts have been employed to monitor CsA blood levels. The widely used trough levels had never been formally validated, and every center had defined its own target values. With the advanced microemulsion formula of CsA, drug exposure became more predictable, but scientifically evaluated monitoring concepts are still lacking. Monitoring the absorption phase using single time points (eg, 2 hours after ingestion) is promising, as shown in adult trials. In pediatric transplant recipients, randomized clinical trials have to be implemented urgently to fully exploit the potential of CsA in the prevention of graft rejection while minimizing toxicity. Although newer immunosuppressive drugs have been developed, further studies should be undertaken to define the role of CsA in combination protocols.