Immunosuppression: practice and trends

Conversion to mycophenolate mofetil for modulating recurrent hepatitis C in liver transplant recipients

BACKGROUND

The aim of this study was to analyze the influence of cyclosporine A (CsA) taper in conjunction with mycophenolate mofetil (MMF) therapy on recurrent hepatitis C virus (HCV) in liver transplant patients.

PATIENTS AND METHODS

Nineteen liver recipients with serologically and morphologically confirmed recurrent HCV were included in this study. After MMF introduction up to a maximum dose of 2000 mg/day, CsA dose was significantly tapered. In the control group immunosuppression remained unchanged. Allograft function and morphology, viral loads, and renal function were analyzed continuously.

RESULTS

MMF treatment was well tolerated without risk of rejection. Allograft fibrosis progressed in 6 patients of the MMF group (66.6%) and none (0%) of the controls at 12-month biopsy (P=0.005). Moreover, aminotransferases and viral loads increased slightly in the MMF-treated patients. Renal function improved significantly (serum creatinine: 239.3+/-90.2 micromol/L vs. 175.8+/-46.0 micromol/L; P=0.008) in the treatment group, while deteriorating (serum creatinine: 156.8+/-44.6 micromol/L vs. 214.8+/-120.1 micromol/L; P=0.06) in the controls.

CONCLUSION

MMF introduction allows a safe CsA taper in HCV-positive liver transplant patients and results in significant improvement of renal function. However, there seems to be a risk of marked progression of HCV-induced allograft injury.

Sensitivity of hepatitis C virus to cyclosporine A depends on nonstructural proteins NS5A and NS5B

HCV re-occurs after liver transplantation and increases mortality. Cyclosporine, but not tacrolimus, has potent antiviral effects against HCV replication in cell culture. To determine the conditions, if any, under which HCV is susceptible to cyclosporine in vivo, we selected for cyclosporine-resistant mutant HCV in vitro. The resulting mutations were mapped to x-ray crystallographic structures and sequence databases. Mutations selected by cyclosporine were clustered in the nonstructural (NS) proteins NS5A and NS5B. Different sets of mutations in NS5A, paired with the same 2 NS5B mutations, conferred different levels of cyclosporine resistance when engineered back into the HCV replicon. Mutations in NS5B are structurally consistent with a proposed model of regulation of RNA binding by cyclophilin B (CyPB). These mutations also highlight a natural polymorphism between different HCV genotypes that correlates with the variation in response to cyclosporine A (CsA) noted in some clinical trials. Replicons engineered to have mutations in only NS5A (P < or = 0.0001) or only NS5B (P = 0.002) suggest that while both NS5A or NS5B variants alter cyclosporine susceptibility, NS5A has the largest effect.

CONCLUSION

Preexisting sequence variation could alter the effect of cyclosporine on HCV in vivo.

Individualization of mycophenolate mofetil dose in renal transplant recipients

The immunosuppressive agent mycophenolate mofetil has been successfully used over the past 10 years to prevent acute allograft rejection after renal transplantation. It has mainly been administered as a fixed dose of mycophenolate mofetil 1000 mg b.i.d. The pharmacokinetics of mycophenolic acid, the active moiety of the prodrug mycophenolate mofetil, show large between-patient variability, and exposure to mycophenolic acid correlates with the risk for acute rejection. This suggests that already excellent clinical results can be further improved by mycophenolate mofetil dose individualization. This review discusses different arguments in favour of individualization of mycophenolate mofetil dose, as well as strategies for managing mycophenolate mofetil therapy individualization, including pharmacokinetic and pharmacodynamic monitoring and dose individualization based on pharmacogenetic information. It is expected that pharmacokinetic monitoring of mycophenolic acid will offer the most effective and feasible tool for mycophenolate mofetil dose individualization.

Pharmacokinetics of mycophenolate mofetil in hematopoietic stem cell transplant recipients

Mycophenolate mofetil (MMF), a prodrug of mycophenolic acid (MPA), is increasingly used in the prophylaxis of graft-versus-host disease (GVHD) after hematopoietic stem cell transplantation (HCT). Few pharmacokinetic data are available about the use of MMF for this indication. This case series aimed at analyzing the pharmacokinetics of MMF in a population of HCT recipients representative for everyday practice. From 15 HCT recipients, serial plasma samples were taken after twice-daily oral intake of MMF. Plasma concentrations of total MPA and its glucuronide metabolites, as well as free MPA, were quantified. Median apparent oral MPA clearance (CL/F), apparent half-life, and total MPA area under the curve for hours 0 to 12 (AUC0-12, normalized to 1000 mg MMF) were, respectively, 56 L/h (range: 29-98 L/h), 2.3 hours (range: 0.8-5.7 hours), and 18.0 mg*h/L (range: 10-35 mg*h/L). Total MPA concentrations were below 2 mg/L 8 hours after MMF administration, indicating reduced enterohepatic recirculation. Median free MPA AUC0-12 (normalized to 1000 mg MMF) was 224 microg*h/L (range: 56-411 microg*h/L). Because of high CL/F, total MPA exposure in HCT recipients is low and apparent half-life is short in comparison with reference values from renal transplantation. Exposure may be improved in HCT recipients by higher or more frequent MMF dosing.

Pharmacokinetics, safety, and efficacy of mycophenolate mofetil in combination with sirolimus or ciclosporin in renal transplant patients

AIMS

To compare the pharmacokinetics of mycophenolic acid (MPA) and its metabolite (MPAG) when mycophenolate mofetil (MMF) is administered in combination with sirolimus or ciclosporin (CsA) in renal allograft recipients. Safety and efficacy (biopsy-proven acute rejection (BPAR)) were also assessed.

METHODS

Patients (n = 45) were randomized 2 : 1 to receive treatment with sirolimus (n = 30; dosed to maintain trough concentrations of 10-25 ng ml(-1) until week 8, and then 8-15 ng ml(-1) thereafter) or CsA (n = 15; administered as per centre practice) both in combination with daclizumab, oral MMF and corticosteroids. Pharmacokinetic assessments were performed at day 7, week 4, and months 3 and 6 post-transplant. The primary endpoint was the AUC(0,12 h) for MPA and MPAG. The pharmacokinetics of sirolimus were also assessed.

RESULTS

MPA exposure was 39-50% lower (month 6 mean AUC(0,12 h) (95%CI): 40.4 (33.8, 47.0) vs. 68.5 (54.9, 82.0) microg ml(-1) h) and MPAG exposure was 25-52% higher (722 (607, 838) vs. 485 (402, 569) microg ml(-1) h at month 6) in the presence of CsA compared with sirolimus across visits. BPAR was 40.0% with sirolimus and 13.3% with CsA. The incidence of hypertension, tremors and hirsutism was higher with CsA than with sirolimus, while the incidence of diarrhoea, hyperlipidaemia and impaired wound closure was higher with sirolimus. No deaths, malignancies or graft losses were reported.

CONCLUSIONS

Co-administration of sirolimus with MMF led to greater MPA exposure, but lower MPAG exposure, than co-administration with CsA. As rejection rates were higher in the absence of CsA, further study of calcineurin inhibitor-free regimens is required before general recommendations can be made.

EBV-specific CD8+ T cell reactivation in transplant patients results in expansion of CD8+ type-1 regulatory T cells

Posttransplantation lymphoproliferative disorders (PTLD) are life-threatening complications of solid organ transplantation, triggered by EBV infection in chronically immunosuppressed (IS) patients. Our goal is to establish DC-based protocols for adoptive immunotherapy of refractory PTLD, while understanding how the immunosuppressive drug environment may subvert DC-EBV-specific T cell interactions. Type-1 CD8(+) T cells are critical for efficient immune surveillance and control of EBV infection, whereas type-2 or Treg/type-3 responses may provide an environment conductive to disease progression. We have recently reported that chronic IS inhibits DC function in transplant patients. Here, we have analyzed the comparative ability of mature, type-1 polarized DCs (i.e. DC1) generated from quiescent transplant patients or healthy controls, to boost type-1 EBV-specific CD8(+) T cells in vitro. Our results show that unlike healthy controls, where DC1 loaded with MHC class I EBV peptides preferentially reactivate specific type-1 CD8(+) T cells, DC1 generated from transplant patients reactivate EBV-specific CD8(+) T cells that produce both IFN-gamma and IL-10, up-regulate FOXP3 mRNA, and suppress noncognate CD4(+) T-cell proliferation via cell-cell contact. These data support a novel regulatory pathway for anti-EBV T-cell-mediated responses in IS transplant patients, with implications for the design of adoptive immunotherapies in this setting.

Current concepts and perspectives of immunosuppression in organ transplantation

BACKGROUND

While early surgical success made organ transplantation possible in the 1950s and 1960s, the breakthrough in clinical organ transplantation was achieved through the discovery and invention of modern immunosuppressive agents in the early/mid-1980s. Especially during the 1990 s, a large array of immunosuppressants has expanded the armamentarium used to prevent and treat allograft rejection, resulting in an excellent short-term and an acceptable long-term outcome. However, these drugs have potent but still non-specific immunosuppressive properties and frequently show severe acute and chronic side effects, sometimes questioning the overall success.

CONCEPTS/TRENDS

As the "Holy-Grail" of the transplant community, the induction of "true donor-specific tolerance" has not been achieved yet; current immunosuppressive strategies, in particular in Europe, include "individually tailored immunosuppressive" protocols, mostly based on specific immunologic and non-immunologic risk factors. These protocols allow for optimal immunosuppressive protocols for each patient group according to their needs by choosing the most suitable, well-tolerated combination of agents and the most effective doses to avoid acute rejection episodes (incidence and severity) and minimise drug-related toxicity to reduce long-term drug-related morbidity and mortality. Nevertheless, transplant recipient are still being forced to take a life-long course of chemical immunosuppressive agents to keep their graft, knowing about the possible life-threatening side effects.

SUMMARY

We review current trends of immunosuppressive protocols in liver and kidney transplantation, focusing on calcineurin-inhibitor-sparing protocols, mammalian-target-of-rapamycin (mTOR) inhibitor based-protocols and corticosteroid-avoidance protocols, being aware of the fact, that most of these strategies could be applicable for other transplanted organs, too. Finally, we describe future trends and new developments that are rising on the horizon.

Therapeutic drug monitoring of mycophenolic acid: does it improve patient outcome?

Treatment with the immunosuppressive agent mycophenolate mofetil (MMF) decreases the risk of rejection after renal transplantation and improves graft survival compared with azathioprine. The exposure to the active metabolite mycophenolic acid (MPA) is correlated to the risk of developing acute rejection. The interpatient variability in exposure of MPA is wide relative to the proposed therapeutic window of the MPA AUC(0 12) (30 - 60 mg.h/l). The pharmacokinetics of MPA are influenced by patient characteristics such as gender, time after transplantation, serum albumin concentration, renal function, comedication and pharmacogenetic factors. Therapeutic drug monitoring is likely to reduce inter-patient variability. Limited sampling strategies are used to predict the full AUC(0 12). Three prospective randomised studies compared concentration controlled MMF therapy to a fixed-dose regimen. Preliminary outcomes of these studies showed conflicting results and longer follow up is needed to further clarify the role of therapeutic drug monitoring in increasing the therapeutic potential of MMF.

Clinical pharmacokinetics and pharmacodynamics of mycophenolate in solid organ transplant recipients

This review aims to provide an extensive overview of the literature on the clinical pharmacokinetics of mycophenolate in solid organ transplantation and a briefer summary of current pharmacodynamic information. Strategies are suggested for further optimisation of mycophenolate therapy and areas where additional research is warranted are highlighted. Mycophenolate has gained widespread acceptance as the antimetabolite immunosuppressant of choice in organ transplant regimens. Mycophenolic acid (MPA) is the active drug moiety. Currently, two mycophenolate compounds are available, mycophenolate mofetil and enteric-coated (EC) mycophenolate sodium. MPA is a potent, selective and reversible inhibitor of inosine monophosphate dehydrogenase (IMPDH), leading to eventual arrest of T- and B-lymphocyte proliferation. Mycophenolate mofetil and EC-mycophenolate sodium are essentially completely hydrolysed to MPA by esterases in the gut wall, blood, liver and tissue. Oral bioavailability of MPA, subsequent to mycophenolate mofetil administration, ranges from 80.7% to 94%. EC-mycophenolate sodium has an absolute bioavailability of MPA of approximately 72%. MPA binds 97-99% to serum albumin in patients with normal renal and liver function. It is metabolised in the liver, gastrointestinal tract and kidney by uridine diphosphate gluconosyltransferases (UGTs). 7-O-MPA-glucuronide (MPAG) is the major metabolite of MPA. MPAG is usually present in the plasma at 20- to 100-fold higher concentrations than MPA, but it is not pharmacologically active. At least three minor metabolites are also formed, of which an acyl-glucuronide has pharmacological potency comparable to MPA. MPAG is excreted into the urine via active tubular secretion and into the bile by multi-drug resistance protein 2 (MRP-2). MPAG is de-conjugated back to MPA by gut bacteria and then reabsorbed in the colon. Mycophenolate mofetil and EC-mycophenolate sodium display linear pharmacokinetics. Following mycophenolate mofetil administration, MPA maximum concentration usually occurs in 1-2 hours. EC-mycophenolate sodium exhibits a median lag time in absorption of MPA from 0.25 to 1.25 hours. A secondary peak in the concentration-time profile of MPA, due to enterohepatic recirculation, often appears 6-12 hours after dosing. This contributes approximately 40% to the area under the plasma concentration-time curve (AUC). The mean elimination half-life of MPA ranges from 9 to 17 hours. MPA displays large between- and within-subject pharmacokinetic variability. Dose-normalised MPA AUC can vary more than 10-fold. Total MPA concentrations should be interpreted with caution in patients with severe renal impairment, liver disease and hypoalbuminaemia. In such individuals, MPA and MPAG plasma protein binding may be altered, changing the fraction of free MPA available. Apparent oral clearance (CL/F) of total MPA appears to increase in proportion to the increased free fraction, with a reduction in total MPA AUC. However, there may be little change in the MPA free concentration. Ciclosporin inhibits biliary excretion of MPAG by MRP-2, reducing enterohepatic recirculation of MPA. Exposure to MPA when mycophenolate mofetil is given in combination with ciclosporin is approximately 30-40% lower than when given alone or with tacrolimus or sirolimus. High dosages of corticosteroids may induce expression of UGT, reducing exposure to MPA. Other co-medications can interfere with the absorption, enterohepatic recycling and metabolism of mycophenolate. Most pharmacokinetic investigations of MPA have involved mycophenolate mofetil rather than EC-mycophenolate sodium therapy. In population pharmacokinetic studies, MPA CL/F in adults ranges from 14.1 to 34.9 L/h (ciclosporin co-therapy) and from 11.9 to 25.4 L/h (tacrolimus co-therapy). Patient bodyweight, serum albumin concentration and immunosuppressant co-therapy have a significant influence on CL/F. The majority of pharmacodynamic data on MPA have been obtained in patients receiving mycophenolate mofetil therapy in the first year after kidney transplantation. Low MPA AUC is associated with increased incidence of biopsy-proven acute rejection. Gastrointestinal adverse events may be dose related. Leukopenia and anaemia have been associated with high MPA AUC, trough concentration and metabolite concentrations in some, but not all, studies. High free MPA exposure has been identified as a risk factor for leukopenia in some investigations. Targeting a total MPA AUC from 0 to 12 hours (AUC12) of 30-60 mg.hr/L is likely to minimise the risk of acute rejection and may reduce toxicity. IMPDH monitoring is in the early experimental stage. Individualisation of mycophenolate therapy should lead to improved patient outcomes. MPA AUC12 appears to be the most useful exposure measure for such individualisation. Limited sampling strategies and Bayesian forecasting are practical means of estimating MPA AUC12 without full concentration-time profiling. Target concentration intervention may be particularly useful in the first few months post-transplant and prior to major changes in anti-rejection therapy. In patients with impaired renal or hepatic function or hypoalbuminaemia, free drug measurement could be valuable in further interpretation of MPA exposure.

New advances in antirejection therapy

PURPOSE OF REVIEW

The prevention and treatment of rejection have been the major focus of clinical and research studies since the inception of heart transplantation. Recent improvement in survival after transplant has been in large part due to continued advancement in antirejection therapies.

RECENT FINDINGS

The combination of steroids/cyclosporine/azathioprine has been widely used since the early 1980s. The last decade has seen the increasing use of the drugs mycophenolate mofetil and tacrolimus. Newer agents such as target of rapamycin protein inhibitors and anti-interleukin-2 inhibitors have come under intense research recently, and may play a significant role in heart transplantation. Further study is required for agents such as rituximab. With the recent introduction of a new grading of cardiac allograft rejection, controversy remains over when rejection should be treated and which agents should be used.

SUMMARY

Use of newer proven antirejection drugs has reduced rejection and improved survival after heart transplantation. Rejection and side effects from these drugs are still major problems, however; therefore continued research in this area is required.

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.

Evolutional Changes in Maintenance Immunosuppression Following Heart Transplantation

Patients with a heart transplant (HT) may require changes in their immunosuppressive maintenance medication. The basic treatment regimen in our patients consisted of an anticalcineurin agent, an antimetabolite, and a steroid.

OBJECTIVE

We undertook a descriptive study to quantify the incidence and causes of these changes and determine how they occur.

MATERIALS AND METHODS

We included the 432 HT performed at our center from November 1987 to October 2005. The baseline treatment was considered to be the treatment given following HT, and the maintenance treatment was that taken at the time of data collection. Kaplan-Meier survival curves were constructed for the analysis.

RESULTS

The most significant change was the switch from azathioprine to mycophenolate mofetil. The survival rate after 17 years was 66%.

CONCLUSIONS

As in the international registries, there has been an evident reduction in the use of cyclosporine and more particularly of azathioprine, in favor of tacrolimus and mycophenolate mofetil, respectively. No changes in the use of steroids have been observed. These data reflect an increasingly greater use of immunosuppressive agents with reduced side effect profiles.

Current and evolving immunosuppressive regimens in kidney transplantation

The advent of novel immunosuppressive agents with increased potency now offers multiple treatment options for transplant physicians. However, variable efficacy, drug-drug interactions, and adverse effects associated with long-term immunosuppression continue to complicate the clinical management of kidney transplant recipients. Currently, investigators are challenged to develop regimens that take into account not only efficacy, but also dosing, monitoring, safety, and patient quality of life. Recent research has focused on evaluating new combinations of approved agents that seek to improve outcomes by improving control of immunologic events with fewer complications. This article reviews current practice and recent studies to give all health care providers who manage kidney transplant recipients a better understanding of current regimens and general trends in immunosuppressive therapy.

Mycophenolate mofetil use is associated with decreased risk of late acute rejection in adult liver transplant recipients

Mycophenolate mofetil (MMF) used in a triple-drug regimen has been shown to decrease acute rejection rates, compared to a double-drug regimen. The impact of MMF on late acute rejection (LAR) episodes has not been well described. To investigate the risk of LAR (rejection > or = 6 months post-transplantation) data from the Scientific Registry of Transplant Recipients (SRTR) were used. We studied adult primary liver transplant recipients transplanted between June 1, 1995, and April 30, 2004, with hepatitis C virus (HCV) (n = 3356), hepatitis B virus (HBV) (n = 550) or a nonviral (n = 5740) primary cause of liver disease who were recorded as receiving continuous 3-(MMF + Tacro + steroids) versus 2-drug (Tacro + steroids) therapy for at least 6 months immediately post transplantation. Kaplan-Meier analysis showed significantly lower LAR rates 4 years post-transplant in 3- versus 2-drug HCV, HBV and nonviral disease patients. Multivariate regression confirmed 3- versus 2-drug therapy to be associated with a decreased risk of LAR. Late graft survival was significantly lower at 4 years post-transplant for patients with LAR 6-12 months post-transplantation versus patients with early rejection (78.0% vs. 87.0%, p < 0.001) and no rejection (88.1%, p < 0.001). Three-drug versus 2-drug therapy for a minimum of 6 months may offer a better treatment strategy to avoid the consequences and expense of LAR episodes.

Biologics in the prevention and treatment of graft rejection

Biologics are used in solid organ allografting and hematopoietic stem cell transplantation (HSCT) for the induction and maintenance of immunosuppression. In solid organ transplantation, antibodies targeting T cells are part of induction protocols administered for initiation of immunosuppression during organ transfer and during sustained post transplant periods for prevention of graft rejection. Several clinical trials in renal allografting provide data for the efficacy and safety of biologics in this clinical setting. Application of biologics also allows the reduction of calcineurin inhibitors, thereby reducing toxicity and improving long-term graft function. In acute rejection periods, anti T cell antibodies are established in steroid-resistant cases. Strategies interfering with the activity of soluble cytokines are less frequently applied for solid organ transplantation. In HSCT, T cell directed antibodies as part of conditioning protocols improve engraftment and reduce the incidence of detrimental graft vs host disease (GvHD). In acute GvHD, both antibodies targeting T cells and cytokines like TNF-alpha are established therapeutics for remission induction.

Soluble HLA-G in heart transplantation: their relationship to rejection episodes and immunosuppressive therapy

The aims of this study were to quantify the level of soluble HLA-G in heart transplant patients, to determine the relationship between the sHLA-G levels and the appearance of acute rejection episodes, and to identify the influence of immunosuppressive therapy on sHLA-G levels. Analysis of sHLA-G, measured by enzyme-linked immunosorbent assay in the transplant patients, revealed the existence of two similarly sized groups of patients. One group displayed a significant increase (p < 0.001) in sHLA-G during the first month after transplantation while the other group maintained low levels of the molecule (0-30 ng/ml) throughout the study. The latter group displayed a high incidence of recurrent severe rejection. A significant increase (p < 0.01) in sHLA-G 2 hours after administration of immunosuppressive treatment (mycophenolate mofetil, cyclosporine A/FK506, corticoids) was found. These results suggest that sHLA-G participates in the induction of certain levels of immunological tolerance in these recipients.

Choice of antibody immunotherapy influences cytomegalovirus viremia in simultaneous pancreas-kidney transplant recipients

OBJECTIVE

Simultaneous pancreas-kidney (SPK) transplantation in type 1 diabetic patients requires immunotherapy against allo- and autoreactive T-cells. Cytomegalovirus (CMV) infection is a major cause for morbidity after transplantation and is possibly related to recurrent autoimmunity. In this study, we assessed the pattern of CMV viremia in SPK transplant recipients receiving either antithymocyte globulin (ATG) or anti-CD25 (daclizumab) immunosuppressive induction therapy.

RESEARCH DESIGN AND METHODS

We evaluated 36 SPK transplant recipients from a randomized cohort that received either ATG or daclizumab as induction therapy. Patients at risk for CMV infection received oral prophylactic ganciclovir therapy. The CMV DNA level in plasma was measured for at least 180 days using a quantitative real-time PCR. Recipient peripheral blood mononuclear cells were cross-sectionally HLA tetramer-stained for CMV-specific CD8(+) T-cells.

RESULTS

Positive CMV serostatus in donors was correlated with a higher incidence of CMV viremia than negative serostatus. In patients at risk, daclizumab induction therapy significantly prolonged CMV-free survival. CMV viremia occurred earlier and was more severe in patients with rejection episodes than in patients without rejection episodes. CMV-specific CD8(+) T-cell counts were significantly lower in patients developing CMV viremia than in those who did not.

CONCLUSIONS

Despite their comparable immunosuppressive potential, daclizumab is safer than ATG regarding CMV infection risk in SPK transplantation. ATG-treated rejection episodes are associated with earlier and more severe infection. Furthermore, high CMV-specific tetramer counts reflect antiviral immunity rather than concurrent viremia because they imply low viremic activity. These findings may prove valuable in the discussion on both safety of induction therapy and recurrent autoimmunity in SPK and islet transplantation.

Ciclosporin aggravates tissue damage in ischemia reperfusion-induced acute pancreatitis

OBJECTIVES

Ischemia reperfusion (I/R)-associated early graft pancreatitis is a major complication after pancreas transplantation. The influence of immunosuppressants on graft pancreatitis remains unclear. The aim of this study was to evaluate ciclosporin and tacrolimus in experimental pancreatic I/R.

METHODS

Moderate pancreatitis was induced in rats by I/R injury. Animals were assigned to 4 groups: (1) control without I/R, (2) I/R without therapy, (3) I/R + ciclosporin, or (4) I/R + tacrolimus. After 24 hours, pancreatic damage was evaluated by amylase, endothelin 1, thromboxane A2, and histology. Additionally, microcirculation was evaluated 12 hours after reperfusion by intravital microscopy.

RESULTS

I/R significantly increased amylase compared with controls, with maximum levels after ciclosporin treatment. Histology showed comparable tissue injury in control and tacrolimus-treated animals. Ciclosporin-treated animals developed significantly (P < 0.05) more inflammation and necrosis compared with the other groups. Erythrocyte velocity evaluated by intravital microscopy was reduced in all animals after I/R. This was significantly pronounced after ciclosporin application. There was a significant increase of adherent leukocytes and platelets in ciclosporin-treated animals compared with both other groups.

CONCLUSIONS

Tacrolimus does not negatively influence I/R-induced pancreatitis, whereas ciclosporin aggravates pancreatic tissue damage after I/R. These effects should be evaluated in the clinical setting of pancreas transplantation.

Psychological disorders and distress after adult cardiothoracic transplantation

This review summarizes and integrates evidence concerning mental health outcomes following heart, lung, and heart-lung transplantation. Drawing on English-language case reports and empirical studies published between January 1980 and December 2004, the goals of the review were to (a) describe the prevalence and clinical characteristics of psychological disorders, as well as the level and pattern of clinically significant distress in the years posttransplant; (b) review the major risk factors for poor posttransplant psychological outcomes; (c) consider evidence suggesting that posttransplant psychological outcomes predict physical morbidity and mortality after transplant; (d) summarize findings from intervention studies designed to improve posttransplant psychological outcomes; and (e) provide patient care recommendations for the practicing clinician and recommendations for continued clinical research. Several major conclusions can be drawn from this literature. First, depressive and anxiety-related disorders and associated distress are common posttransplant. While new onsets of disorder may decline after the first year posttransplant, the development of new medical complications in the late years posttransplant may provoke renewed distress and recurrences of disorder. Second, risk factors for posttransplant psychological disorders and elevated distress include both standard risk factors observed in other populations (eg, younger age, lifetime history of psychiatric disorder) and transplant-specific factors related to physical functional impairments, social supports, and strategies for coping with health problems. Third, while little evidence has been published to date, there is some indication that posttransplant psychological outcomes can predict subsequent physical health outcomes. Fourth, extremely few intervention studies in cardiothoracic transplant recipients have been performed. The few reports indicate that multicomponent psychosocial strategies focused on risk factor reduction and enhancement of personal coping resources may lead to reductions in psychological distress. An important caveat in considering all of the evidence reviewed is that most studies focus on heart rather than lung or heart-lung recipients. Recommendations for practicing clinicians focus on assessment and treatment options, based on the evidence to date. Research recommendations focus on the need for intervention effectiveness studies.

Ten Years of Treatment With Tacrolimus Is Related to an Excellent Renal Function, Allowing Monotherapy in a Large Proportion of Cases: Unicentric Results of the Tacrolimus Versus Cyclosporine A European Multicentric Study in Kidney Transplant Patients

Tacrolimus (Tac) is the most frequently used base inmunosuppressant for transplantation in Spain and the United States. However, long-term data on its use in renal transplant patients are lacking. The aim of this study was to analyze the 10-year outcome of patients from our institution treated with Tac or cyclosporine (CsA) who were included in the European Multicenter Study of kidney transplantation (1993 to 1994). This trial compared the efficacy and safety of steroids + Tac + azathioprine versus steroids + CsA + azathioprine at 1 year, showing a significantly lower acute rejection rate in Tac patients, with no differences in graft or patient survival. In our long-term analysis, we included patients with a functioning graft after the first year: 15 patients on Tac and 11 on CsA. In the "intent-to-treat" (ITT) analysis, patient survival was 14/15 (93%) versus 9/11 (82%) and death noncensored graft survival was 10/15 (67%) versus 8/11 (73%) in Tac and CsA, respectively. Analyzing patients "into treatment" (TT), death/noncensored graft survival was 11/16 (69%) versus 6/9 (67%), respectively. Serum creatinine tended to be lower in Tac group (ITT 1.26 +/- 0.42 vs 1.63 +/- 1.16 mg/dL, P = NS; TT 1.23 +/- 0.4 vs 1.86 +/- 1.28 mg/dL, P = NS). However, in the TT analysis, Tac patients exhibited a significantly better creatinine clearance (89.3 +/- 40 vs 46.8 +/- 21 mL/min, P = .037) and lower systolic blood pressure (125 +/- 5 vs 140 +/- 12 mm Hg, P = .007) at 10 years. No other significant differences were observed in blood pressure, lipid profile, or glucose metabolism. Outstandingly, Tac monotherapy was the most frequently used regimen after 10 years: ITT 6/9 (67%) versus 1/8 (12.5%), P = .05, TT 7/10 (70%) versus 0/6 (0%), P = .011. Patients under Tac monotherapy exhibited an excellent graft function (serum creatinine 1.08 +/- 0.14 mg/dL) and negative proteinuria, with Tac trough levels of 7.9 +/- 1.3 ng/mL. In summary, our results suggest that Tac-based immunosuppression provides an excellent kidney function 10 years after transplantation and allows monotherapy in a high percentage of kidney transplant patients.

Impact of mycophenolate mofetil loading on drug exposure in the early posttransplant period

Achieving adequate therapeutic levels of immunosuppressive medications is important in rejection prevention. This study examined exposure to mycophenolic acid (MPA) in kidney transplant patients within the first 5 days posttransplantation.

METHODS

This single-center, nonrandomized study of first solitary kidney allograft recipients receiving cyclosporine (n = 116) or tacrolimus (n = 50) included patients who received either 1 g or 1.5 g of mycophenolate mofetil twice daily starting postoperatively. Exposure to MPA was measured at days 3 and 5 posttransplant using published limited sampling time equations.

RESULTS

There were no significant differences in exposure in the cyclosporine-treated patients receiving 3-g (n = 22) compared to 2-g (n = 94) daily doses (AUC([0-12]) 33.8 +/- 10.0 mg*h/L versus 30.1 +/- 9.7 mg*h/L, P = .20, respectively). About half the patients in both groups had AUC([0-12]) <30 mg*h/L on days 3 and 5 posttransplant. On the other hand, there was significantly greater exposure on day 3 in the tacrolimus-treated patients receiving 3 g (n = 21) compared to 2 g (n = 29) daily (AUC([0-12]) 43.1 +/- 9.0 mg*h/L versus 36.8 +/- 11.1 mg*h/L, P = .016, respectively). On day 3 one (4.8%) patient receiving 3 g had an AUC([0-12]) of <30 mg*h/L; whereas, eight (27.5%) receiving 2 g were below this level (P = .068). The AUC([0-12]) levels were not different on day 5.

CONCLUSIONS

Loading with higher doses of mycophenolate mofetil results in greater exposure and a trend toward more patients in the therapeutic window within the first week for tacrolimus- but not for cyclosporine-treated patients.

Screening to prevent polyoma virus nephropathy: a medical decision analysis

Polyomavirus nephropathy (PVN) is an emerging medical dilemma in kidney transplantation. Methods to screen before clinical disease are available and early immunosuppression reduction may change the natural history of progression. However, the consequences of an increase in rejection may limit the benefits. In a simulation model a 'screen' versus 'no-screen' strategy was compared. Baseline PVN cumulative incidence was assumed to be 4%. Patients with PVN were modeled to have 4-fold higher risk of graft loss. In the screen strategy, patients positive for blood DNA PCR had their immunosuppression reduced. This pre-emptive change was modeled to reduce progression to overt PVN by 80%. Therapy reduction was associated with a 10% risk of precipitating acute rejection and greater risk of chronic allograft loss. In the baseline case, screening saved 1912 dollars (discounted) and produced 0.020 more quality adjusted life years (QALYs) than not screening. Screening resulted in decreased net QALYs if the false positive viremia rate was >9.5% and the PVN incidence was <2.1%. Much of the cost savings of screening relate to savings from immunosuppression reduction in the screened arm. Screening may well be cost-effective if not cost saving in centers with high PVN rates. There remain significant areas of uncertainty.

Three-year efficacy and safety results from a study of everolimus versus mycophenolate mofetil in de novo renal transplant patients

Everolimus 1.5 or 3 mg/day was compared with mycophenolate mofetil (MMF) 2 g/day in a randomized, multicenter 36-month trial in de novo renal allograft recipients (n = 588) receiving cyclosporine microemulsion (CsA) and corticosteroids. The study was double-blind until all patients had completed 12 months, then open-label. By 36 months, graft loss occurred in 7.2, 16.7 and 10.7% of patients in the everolimus 1.5, 3 mg/day, and MMF groups, respectively (p = 0.0048 for everolimus 1.5 mg/day vs. 3 mg/day); efficacy failure (biopsy-proven acute rejection (BPAR), graft loss, death or lost to follow-up) occurred in 33.0, 38.9 and 37.2% of patients (p = 0.455 overall), respectively. Mortality and incidence of BPAR were comparable in all groups. Creatinine values were higher in everolimus groups, requiring a protocol amendment that recommended lower CsA exposure. Diarrhea, lymphocele, peripheral edema and hyperlipidemia were more common among everolimus-treated patients, whereas viral infections, particularly cytomegalovirus infection, increased in the MMF group. Overall safety and tolerability were better with MMF and everolimus 1.5 mg/day than with everolimus 3 mg/day. In conclusion, at 36 months, an immunosuppressive regimen containing everolimus 1.5 mg/day had equivalent patient, and graft survival and rejection rates compared with MMF in de novo renal transplant recipients, whereas everolimus 3 mg/day had inferior graft survival. Renal dysfunction in everolimus cohorts necessitates close monitoring.

The Impact of Mycophenolate Mofetil on Long-Term Outcomes in Kidney Transplantation

Mycophenolate mofetil (MMF) has been used in kidney and pancreas transplantation for almost 10 years. In the pivotal phase III trials, MMF use was accompanied by a dramatic reduction of rejection rates in kidney transplantation; however, the impact on graft and patient was undetermined. Analyses of the United States Renal Data System and the Scientific Registry of Transplant Recipients databases later provided a valuable measure of the impact of MMF in improving outcomes. In this review, we provide a synopsis of the prospective studies, including but not limited to the pivotal MMF approval trials, and analyses of the national transplant registries relevant to the long-term impact of MMF in kidney transplantation. Indeed, a substantial body of evidence has shown MMF treatment improves patient survival, graft survival, and death-censored graft survival in kidney transplantation. The beneficial effects of MMF have been particularly notable in high-risk recipients such as African Americans. In coming years, these benefits will require reevaluation in the context of the growing use of novel protocols combining MMF with tacrolimus or sirolimus.

[Tacrolimus blood levels and incidence of graft rejection in heart transplantation]

OBJECTIVE

To determine the relationship between pharmacokinetic parameters and clinical outcomes after heart transplantation and to determine the range of tacrolimus blood levels which provides the most effective protection against graft rejection. To study other factors that predict graft rejection.

METHOD

We retrospectively analyzed the clinical outcomes of all adult patients who received a heart transplant between January 2000 and October 2003 and had routine monitoring of tacrolimus trough levels at the time of scheduled endomyocardial biopsy. Rejection was defined as Grade = 3, based on the International Society for Heart and Lung Transplantation (ISHLT) criteria. The follow-up period was 1 year. All patients were on a triple therapy regimen of Tacrolimus (TAC), Corticosteroids and Azatioprine/Micophenolate Mofetil. Data were analyzed by Student s t-test, univariate logistic regression and ROC curve.

RESULTS

Tacrolimus blood levels measured at day +5 postransplant were the strongest predictor of acute graft rejection over a 1-year follow-up period (rejection 5.76 +/- 3.4 ng/ml vs no rejection 9.66 +/- 2.73 ng/ml, p = 0.016). A decrease of one unit in TAC trough level values at day +5 postransplant implied a 1.58 greater risk of rejection (p = 0.05). Overall incidence of treated acute rejection was lower for patients with trough levels higher than 8 ng/ml on day +5 postransplant (33 vs 80%, p = 0.055, Fisher s exact test).

CONCLUSIONS

Data suggest that in heart transplant patients it may be crucial to achieve tacrolimus levels of at least 8 ng/ml during the first days postsurgery to avoid rejection.

Sirolimus in combination with tacrolimus is associated with worse renal allograft survival compared to mycophenolate mofetil combined with tacrolimus

Cyclosporine (CsA) nephrotoxicity is enhanced by sirolimus (SRL). Tacrolimus is perceived to be less nephrotoxic than CsA, and therefore, CsA has been largely replaced by tacrolimus (TAC) when calcineurin inhibitors are used with SRL. We analyzed 44 915 adult renal transplants in the Scientific Renal Transplant Registry (SRTR) from 2000 to 2004. Three thousand five hundred twenty-four (7.8%) patients received a baseline immunosuppressive regimen of TAC/SRL, with an inferior overall (log-rank p<0.001) and death-censored graft survival (p<0.001) as compared to TAC/MMF (N=27 007). This effect was confirmed in multivariate Cox models; the adjusted hazard ratio (AHR) for overall graft loss with TAC/SRL was 1.47 (95% CI=1.32, 1.63) and for CsA/SRL 1.38 (95% CI=1.20, 1.59) relative to TAC/MMF. These effects were most apparent in high-risk transplants. Six-month acute rejection rates were low (11.5-12.6%) and not different between groups. In summary, national data indicate that TAC/SRL as compared to TAC/MMF is associated with significantly worse renal allograft survival in all subgroups of patients and, in particular, higher-risk transplants. These results have to be interpreted in the context of the inherent limitations of any retrospective database analysis and evaluated in context with data from prospective clinical trials.

The macrophage is the predominant inflammatory cell in renal allograft intimal arteritis

BACKGROUND

Intimal arteritis defines acute vascular rejection in the Banff 97 schema. The arteritis is generally considered to be lymphocytic, although the cellular infiltrate in tubulitis is composed of both lymphocytes and macrophages. This study aimed to determine the extent of macrophage involvement in renal allograft intimal arteritis.

METHODS

We obtained archival biopsy material from 57 biopsies of 34 renal allografts transplanted between March 1999 and February 2002. All biopsies were diagnostic. We examined clinical and histological parameters. Biopsies were graded using the Banff 97 criteria. We identified macrophages and memory T cells using immunohistochemistry for CD68 and CD45RO, respectively.

RESULTS

In all, 24 biopsies showed borderline rejection, and 12 biopsies showed grade IA, 13 showed grade IB, and 8 showed grade II or III acute rejection. Both lymphocytes and macrophages were present in the tubulointerstitium in all grades of acute rejection. We identified intimal arteritis in 10 vessels in eight biopsies. The infiltrating cells invariably included CD68-positive cells; however, we saw intimal CD45RO-positive cells in only seven vessels. There were significantly more CD68-positive cells than CD45RO-positive cells (mean, 9.5 vs. 4.4 positive cells per vessel, P< 0.01). CD45RO cells were never the predominant component of the intimal inflammatory infiltrate.

CONCLUSIONS

In the intimal arteritis of biopsies graded as Banff II or III acute rejection, the infiltrating cells were predominantly macrophages. T cells were in the minority. This finding challenges the assumption that the mononuclear cells in intimal arteritis are predominantly lymphocytic.

Mycophenolate mofetil combination therapy improves long-term outcomes after liver transplantation in patients with and without hepatitis C

To evaluate the impact of mycophenolate mofetil (MMF) on long-term outcomes of tacrolimus and corticosteroids, we analyzed data reported to the Scientific Registry of Transplant Recipients for 11,670 adult patients (3463 with hepatitis C [HCV]) who underwent primary, single-organ, liver transplantation between 1995 and 2001. Patients who were discharged from the hospital on tacrolimus-based immunosuppression with (n = 4466; n = 1323 HCV) or without MMF (n = 7204; n = 2140 HCV) were included in the analysis. Recipients treated at discharge with MMF, tacrolimus, and corticosteroids had significantly increased patient survival (81.0% vs. 77.0% at 4 years, P < 0.0001) and graft survival (76.4% vs. 72.9%, P < 0.0001), and lower rates of acute rejection (29.0% vs. 33.4%, P < 0.001) as compared to recipients treated at discharge with tacrolimus and corticosteroids alone. A trend toward lower rates of death from infection was observed (6.1% at 4 years for MMF vs. 7.1% at 4 years for tacrolimus and corticosteroids, P = 0.0508), but this result did not reach statistical significance. In multiple regression analyses, MMF triple therapy at discharge was associated with a reduced risk of death (hazard ratio [HR] = 0.77, P < 0.001), graft loss (HR = 0.81, P < 0.001), acute rejection (HR = 0.89, P = 0.002), and death from infectious complications (HR = 0.80, P = 0.007). Outcomes were similar for the cohort with HCV.In conclusion, the addition of MMF at discharge to tacrolimus-based immunosuppression is associated with improved long-term outcomes after liver transplantation in patients with and without HCV.

Clinical experience with Certican (everolimus) in maintenance heart transplant patients at the Medical University of Vienna

Innovations in immunosuppressant therapy often transfer from renal transplantation to heart transplantation. Accordingly, there is growing interest in calcineurin inhibitor (CNI)- and steroid-sparing regimens for heart transplant patients. The novel proliferation signal inhibitor, Certican (everolimus), has been shown to allow reduced CNI exposure in renal transplant recipients without loss of efficacy. It has also demonstrated efficacy for reducing biopsy-proven acute rejection (BPAR) and cardiac allograft vasculopathy (CAV) in de novo heart transplantation. The present study reports early clinical experience of introducing everolimus as maintenance immunosuppression in heart transplant recipients whose previous regimen had failed. A 58-year-old woman received an organ from a 56-year-old female donor. She was prescribed cyclosporine for micromemulsion (CsA; Neoral), azathioprine, prednisolone and atorvastatin. After 3 months, azathioprine was switched to mycophenolate mofetil (MMF). At Month 27, the patient experienced Grade 3A BPAR, had a left ventricular ejection fraction (LVEF) of 20%, and compromised renal function. After steroid boluses to control BPAR, everolimus 3.0 mg/day was prescribed, while CsA and prednisolone doses were reduced. One month later, the patient contracted herpes labialis and pneumonia, and creatinine was elevated; CsA was stopped, everolimus dose was reduced to 1.5 mg/day and prednisolone reduced further. After another month, LVEF recovered to 50% and creatinine was 1.29 mg/dl. There was evidence of hyperlipidemia, which responded to atorvastatin 10 mg. For maintenance immunosuppression after heart transplantation, everolimus may allow CsA dose reduction and could be efficacious in combination with MMF. Further studies are required to confirm its efficacy and effects on CAV.

NFAT proteins: key regulators of T-cell development and function

Since the discovery of the first nuclear factor of activated T cells (NFAT) protein more than a decade ago, the NFAT family of transcription factors has grown to include five members. It has also become clear that NFAT proteins have crucial roles in the development and function of the immune system. In T cells, NFAT proteins not only regulate activation but also are involved in the control of thymocyte development, T-cell differentiation and self-tolerance. The functional versatility of NFAT proteins can be explained by their complex mechanism of regulation and their ability to integrate calcium signalling with other signalling pathways. This Review focuses on the recent advances in our understanding of the regulation, mechanism of action and functions of NFAT proteins in T cells.

A comparison of tacrolimus and cyclosporine in liver transplantation: effects on renal function and cardiovascular risk status

A retrospective chart review of 1065 consecutive liver allograft recipients in 11 centers from January 1997 to September 1998 was performed. Patients were followed for 3 years or until graft loss. Patients received either tacrolimus (n = 594), cyclosporine (n = 450) or no calcineurin inhibitor (n = 21). Model for end-stage liver disease (MELD) scores at time of transplant were similar between the two groups. During follow-up, more patients switched from cyclosporine to tacrolimus (26.7%) than from tacrolimus to cyclosporine (12.8%; p < 0.0001). Patient and graft survival were equivalent. Corticosteroid use was more common in cyclosporine-treated patients (p < 0.00001). Patients receiving tacrolimus experienced lower serum creatinine levels at months 3 through 36 (p < 0.0001). Systolic blood pressure was lower in patients receiving tacrolimus (p < 0.001) despite a reduced requirement for anti-hypertensive agents (p < 0.0001). In addition, tacrolimus was associated with lower total cholesterol and triglyceride levels for months 3 through 24 and 3 through 12, respectively (p < 0.01), despite a reduced requirement for anti-hyperlipidemic agents. The incidence of new-onset diabetes mellitus was similar in both groups. While both calcineurin inhibitors were associated with excellent patient and graft survival, renal function, blood pressure and serum lipid levels were significantly better with tacrolimus treatment.

Low Hematocrit and Serum Albumin Concentrations Underlie the Overestimation of Tacrolimus Concentrations by Microparticle Enzyme Immunoassay versus Liquid Chromatography–Tandem Mass Spectrometry

Background: Rapid liquid chromatography–tandem mass spectrometry (LC-MS/MS) methods are used increasingly for tacrolimus (TRL) monitoring but show a negative difference with respect to a microparticle immunoassay (MEIA). This report examines possible reasons for this difference between methods.

Methods: We collected 1156 blood samples from 277 adult and 121 pediatric recipients of liver, renal, and bone marrow grafts or hepatocyte or pancreatic islet cell implants. TRL was measured in whole blood by MEIA and LC-MS/MS, and hematologic and biochemical data were collected when available.

Results: LC-MS/MS was significantly more precise (P &lt;0.02) than the MEIA with increased sensitivity. The MEIA had a median difference of 16.2% vs LC-MS/MS overall, and this was significantly affected by patient cohort (P &lt;0.001). The difference was greater in adult or pediatric liver graft recipients while they were inpatients rather than outpatients (31.8% and 14.0% vs 7.5% and 6.5%, respectively). The difference was also greater in bone marrow than kidney graft recipients (32.8% vs 15.8%, respectively). Multiple linear regression analysis showed significant inverse relationships of this difference with hematocrit (packed cell volume) and plasma albumin (P &lt;0.001) in the total cohort and a positive relationship with plasma bilirubin in a subgroup of pediatric liver graft recipients.

Conclusions: Patients with a low packed cell volume and plasma albumin are likely to show artificially high concentrations of TRL when measured by MEIA. The increased risk of underimmunosuppression must be considered should doses be reduced to lower these seemingly high TRL concentrations.

Immunosuppression in liver transplantation: beyond calcineurin inhibitors

Although calcineurin inhibitors (CNIs) remain the mainstay of immunosuppression in liver transplantation (LTX), their long-term toxicity significantly contributes to morbidity and mortality. The elucidation of mechanisms of alloimmunity and leukocyte migration have provided novel targets for immunosuppression development. The toxicities of these agents differ from that of the CNI and act additively or synergistically. CNI avoidance protocols in LTX have not been achieved routinely; however, pilot trials have begun to delineate the limitations and promises of such approaches. CNI-sparing protocols appear to be much more promising in balancing the early need for minimizing rejection while tapering doses and minimizing long-term toxicity.

Tailored immunosuppression and steroid withdrawal in pancreas-kidney transplantation

BACKGROUND

Recent improvements in simultaneous pancreas-kidney transplantation (SPK) and the striking decrease in acute rejection lead us to focus on the effects of long-term immunosuppression.

AIM OF THIS STUDY

Evaluation of a policy of steroid withdrawal and tailored immunosuppression in pancreas-kidney patients treated in a single center.

METHODS

review of the clinical charts in 9 SPK recipients (male/female = 5/4, median age 41 years, median follow-up 42 months), by the same operator, under supervision of the two usual caregivers. Therapeutic protocols. Induction phase: all patients received mycophenolate mophetil (starting dose: 2 grams), tacrolimus and steroids, 8 received Simulect, 1 received thymoglobulins. Maintenance therapy was slowly reduced, with the goal of steroid withdrawal.

RESULTS

The therapeutic adjustments were mainly determined by two almost opposing elements: 1. Rapid adjustments in the case of side-effects (gastrointestinal problems, infections and neoplasia); 2. Slow tapering off in the case of good organ function. On the other hand, a switch to cyclosporine A and to rapamycine was considered in the case of chronic organ malfunction. By these means, over a median of 42 months follow-up, steroid withdrawal was slowly obtained in 6/9 patients (at a median time of 25 months).

CONCLUSIONS

Within the limits of this small-scale study, a tailored immunosuppressive policy allows at least some "positively selected" patients to reach the "dream" of steroid withdrawal after SPK.

Pediatric transplantation

Analysis of the OPTN/SRTR database demonstrates that, in 2002, pediatric recipients accounted for 7% of all recipients, while pediatric individuals accounted for 14% of deceased organ donors. For children fortunate enough to receive a transplant, there has been continued improvement in outcomes following all forms of transplantation. Current 1-year graft survival is generally excellent, with survival rates following transplantation in many cases equaling or exceeding those of all other recipients. In renal transplantation, despite excellent early graft survival, there is evidence that long-term graft survival for adolescent recipients is well below that of other recipients. A causative role for noncompliance is possible. While the significant improvements in graft and patient survival are laudable, waiting list mortality remains excessive. Pediatric candidates awaiting liver, intestine, and thoracic transplantation face mortality rates generally greater than those of their adult counterparts. This finding is particularly pronounced in patients aged 5 years and younger. While mortality awaiting transplantation is an important consideration in refining organ allocation strategies, it is important to realize that other issues, in addition to mortality, are critical for children. Consideration of the impact of end-stage organ disease on growth and development is often equally important, both while awaiting and after transplantation.