A study comparing mycophenolate mofetil to azathioprine in simultaneous pancreas-kidney transplantation

Simultaneous pancreas-kidney transplantation for end-stage renal failure in type 1 diabetes mellitus: Current perspectives

Type 1 diabetes mellitus (T1DM) is one of the important causes of chronic kidney disease (CKD) and end-stage renal failure (ESRF). Even with the best available treatment options, management of T1DM poses significant challenges for cli nicians across the world, especially when associated with CKD and ESRF. Substantial increases in morbidity and mortality along with marked rise in treatment costs and marked reduction of quality of life are the usual consequences of onset of CKD and progression to ESRF in patients with T1DM. Simultaneous pancreas-kidney transplant (SPK) is an attractive and promising treatment option for patients with advanced CKD/ESRF and T1DM for potential cure of these diseases and possibly several complications. However, limited availability of the organs for transplantation, the need for long-term immunosuppression to prevent rejection, peri- and post-operative complications of SPK, lack of resources and the expertise for the procedure in many centers, and the cost implications related to the surgery and postoperative care of these patients are major issues faced by clinicians across the globe. This clinical update review compiles the latest evidence and current recommendations of SPK for patients with T1DM and advanced CKD/ESRF to enable clinicians to care for these diseases.

Antiproliferatives and Transplantation

Antiproliferative agents include Mycophenolic acid and Azathioprine (which is less commonly used unless in certain conditions). They were initially identified for use in autoimmune and cancer research due to their role in disruption of cellular replication. They have now become the cornerstone of antirejection maintenance therapy in solid organ transplant. In this chapter we will describe the major times that lead to discovery, mechanisms of action, side effects, use during pregnancy and the major clinical trials.

First World Consensus Conference on pancreas transplantation: Part II - recommendations

The First World Consensus Conference on Pancreas Transplantation provided 49 jury deliberations regarding the impact of pancreas transplantation on the treatment of diabetic patients, and 110 experts' recommendations for the practice of pancreas transplantation. The main message from this consensus conference is that both simultaneous pancreas-kidney transplantation (SPK) and pancreas transplantation alone can improve long-term patient survival, and all types of pancreas transplantation dramatically improve the quality of life of recipients. Pancreas transplantation may also improve the course of chronic complications of diabetes, depending on their severity. Therefore, the advantages of pancreas transplantation appear to clearly surpass potential disadvantages. Pancreas after kidney transplantation increases the risk of mortality only in the early period after transplantation, but is associated with improved life expectancy thereafter. Additionally, preemptive SPK, when compared to SPK performed in patients undergoing dialysis, appears to be associated with improved outcomes. Time on dialysis has negative prognostic implications in SPK recipients. Increased long-term survival, improvement in the course of diabetic complications, and amelioration of quality of life justify preferential allocation of kidney grafts to SPK recipients. Audience discussions and live voting are available online at the following URL address: http://mediaeventi.unipi.it/category/1st-world-consensus-conference-of-pancreas-transplantation/246.

New Antiproliferative Immunosuppressive Agents

Since the early 1980s, the combination of cyclosporine, azathioprine, and prednisone has been the mainstay tripledrug immunosuppressive regimen used in transplantation. However, advances in drug research, design, and development have allowed for the introduction of new agents that have greatly increased the number of immunosuppressive agents available for use in transplant recipients. Particularly, the newer antiproliferative immunosuppressive drugs (agents that directly inhibit the proliferation of T and B lymphocytes) have had an important impact on patient outcomes posttransplant. These agents are mycophenolate mofetil and sirolimus.

Serial analysis of biomarkers of acute pancreas allograft rejection

Pancreas transplant recipients experience graft loss in spite of improvements in immunosuppressant therapies and diagnostic technologies. Therefore, a method to improve detection and management of acute rejection is needed. This longitudinal study investigated the usefulness of three biomarkers, granzyme B, perforin, and human leukocyte antigen-DR alpha (HLA-DR) measured by real-time PCR on peripheral blood mononuclear cells, for their ability to detect acute rejection and its resolution in 13 recipients of pancreas allograft. Data demonstrated that pre-transplant baseline expression of biomarkers decreased following the initiation of immunosuppression. Throughout follow-up (range 3-27 months), individuals without acute rejection episodes had little variation in their biomarker levels. Recipients with biopsy-proven rejection had a significant increase in the levels of biomarkers as early as five wk before clinical rejection diagnosis. Furthermore, all seven patients with biopsy-proven rejection demonstrated a decrease in the levels of granzyme B and perforin following the increased immunosuppression for the treatment of rejection. This is the first clinical serial measurement of biomarkers in recipients of pancreas transplants. The data demonstrate that upregulation of granzyme B, perforin, and HLA-DR in peripheral blood mononuclear cells are sensitive to changes in the immune environment and could possibly be used to identify those patients at higher risk of rejection.

C4d-positive interacinar capillaries correlates with donor-specific antibody-mediated rejection in pancreas allografts

BACKGROUND

The deposition of the complement split fragment C4d and its association with acute antibody-mediated rejection (AMR) in pancreas transplant (PTx) is not well defined. To characterize the deposition of C4d in PTx, we analyzed 27 PTx biopsies from 18 patients transplanted between 2004 and 2007 at the University of Wisconsin.

METHODS

The presence of C4d was graded in interacinar capillaries (IAC), islets, interstitium, and small- and medium-size vessels. Sera obtained at the time or within 5 days of the biopsy were tested for antidonor-specific antibodies (DSA).

RESULTS

16 biopsies (59.26%) showed at least 5% C4d+ IAC (range 5%-90%). Of those, five biopsies (18.5%) revealed diffuse labeling (>50% C4d+ IAC) and 11 (40.74%) showed focal staining (5%-50% C4d+ IAC). C4d+ IAC (>5%) was significantly associated with the presence of strong DSA for class I or class II (P<0.018). C4d staining of the media or endothelium of small and medium-size vessels was a common finding in all biopsies without any association with DSA. Similarly, staining of islets and parenchymal interstitium was not statistically associated with AMR. The majority of patients received intravenous corticosteroid bolus and taper, with specific cases requiring thymoglobulin, IVIg, rituximab, or plasmapheresis. Forty-six percent of patients who demonstrated AMR returned to insulin therapy because of chronic graft damage and loss of C-peptide.

CONCLUSION

Our findings support the potential role of C4d labeling of PTx biopsies in the diagnosis of AMR and emphasize the staining of IAC as a valuable histologic tool for the diagnosis.

Minimization protocols in pancreas transplantation

Diagnosis of immunologic injury (acute and chronic) is much more difficult in pancreas transplants when compared with transplants of other organs. Currently, the immunosuppressive regimen for induction involves calcineurin inhibitors (CNI), antimetabolites and corticosteroids (Cs). This strong and nonspecific regimen does not take into consideration pancreas specificities (i.e. the need to avoid diabetogenic compounds). For obvious reasons, CNI might be calling for review, if permanently indicated in recipients of solitary pancreas with mild renal dysfunction. CNI as well as corticosteroids may induce hyperglycemia and contribute to differential diagnosis of a rejection process. However, in spite of the benefits accruing from withdrawal of above immunosuppressive agents, minimization or avoidance of these drugs could be dangerous and may end up with graft loss (i.e. antibody-mediated process). Long-term results of pancreas transplantation are now achieving comparable survival rates similar to the transplant of traditional organs such as kidney and liver. As a consequence, the physicians' objectives are to prolong the patient's quality of life and organ function as long as possible. Weaning strategies in regard to CNI and steroids are tested. Sirolimus, everolimus, CTLA-4 Ig, etc, are agents known to be either both nonnephrotoxic and nondiabetogenic or less so when compared with CNI. Their impact on pancreas transplantation is beginning to be evaluated. Large randomized trials in all pancreas categories, with long-term clinical and histologic results, are mandatory to establish new guidelines for immunosuppressive regimens for pancreas transplantation.

Antibody-mediated rejection of the kidney after simultaneous pancreas-kidney transplantation

The prevalence, risk factors, and outcome of antibody-mediated rejection (AMR) of the kidney after simultaneous pancreas-kidney transplantation are unknown. In 136 simultaneous pancreas-kidney recipients who were followed for an average of 3.1 yr, 21 episodes of AMR of the kidney allograft were identified. Eight episodes occurred early (</=90 d) after transplantation, and 13 occurred later. Histologic evidence of concomitant acute cellular rejection was noted in 12 cases; the other nine had evidence only of humoral rejection. In 13 cases, clinical rejection of the pancreas was diagnosed simultaneously, and two of these were biopsy proven and were positive for C4d immunostaining. Multivariate analysis identified only one significant risk factor: Female patients were three times more likely to experience AMR. Nearly all early episodes resolved with treatment and did not predict graft loss, but multivariate Cox models revealed that late AMR episodes more than tripled the risk for kidney and pancreas graft loss; therefore, new strategies are needed to prevent and to treat late AMR in simultaneous pancreas-kidney transplant recipients.

The long-term survival of simultaneous pancreas and kidney transplant with basiliximab induction therapy

Interleukin-2 receptor (IL2R) antibody has emerged as an attractive induction therapy for organ transplant. However, the long-term outcome of basiliximab induction in simultaneous pancreas and kidney (SPK) transplant remains speculative. We retrospectively analyzed the long-term survivals of 91 consecutive SPK recipients with basiliximab as induction, combination of steroid, tacrolimus (TAC) and mycophenolate acid (MFA)--either mycophenolate mofetil (MMF) or sodium mycophenolate (myfortic) as maintenance. At one, three, five, and seven-yr, the actual patient survival rate were 91.2%, 90.3%, 88.1%, and 88.2%, respectively; kidney graft survivals were 90.1%, 84.7%, 78.6%, and 70.6%, respectively; and pancreas graft survivals were 86.8%, 80.6%, 71.4%, and 58.8% respectively. There was a low incidence of rejection and CMV infection. Basiliximab induction with TAC, MFA, and steroid maintenance therapy can provide excellent long-term outcome for SPK recipients.

A comparison of long-term survivals of simultaneous pancreas-kidney transplant between African American and Caucasian recipients with basiliximab induction therapy

African Americans (AA) have traditionally been thought to have higher immunologic risk than Caucasians (CA) for rejection and allograft loss. The impact of ethnicity on the outcome of simultaneous pancreas-kidney (SPK) transplant with basiliximab induction has not been reported. In this study, we retrospectively analyze the long-term results of 36 AA and 55 CA recipients of primary SPK. The actual patient survival rates of AA and CA groups were 91.7% vs. 90.1% at 1 year, 93.3% vs. 88.1% at 3 years, and 94.4% vs. 83.3% at 5 years. The actual kidney survival of AA and CA were 91.7% vs. 89.1% at 1 year, 90% vs. 81% at 3 years, and 83.3% vs. 75% at 5 years. The actual pancreas survival of AA and CA were 88.9% vs. 85.5% at 1 year, 83.3% vs. 78.6% at 3 years and 72.2% vs. 70.8% at 5 years. Death-censored analyses also found no difference in pancreas and kidney graft survival rates over 5 years. Higher rejection rate, but the same low CMV infection, and comparable quality of graft function were noted in AA group. AA may not have worse long-term outcomes than CA recipients of SPK with basiliximab induction and tacrolimus (TAC), mycophenolate acid (MFA) and steroid maintenance immunotherapy.

Immunosuppressive standards in simultaneous kidney?pancreas transplantation

Simultaneous pancreas-kidney transplantation is an established procedure for patients with type I diabetes and end-stage renal disease. Continuous advances in the operation techniques with consequent reduction of perioperative morbidity and mortality and the introduction of modern immunosuppressive agents improved not only patients but also graft survival and significantly decreased rejection episodes of both kidney and pancreas grafts. Availability of a variety of new immunosuppressants in the clinical routine and increasing experience of the transplant specialists allowed further developments of therapeutic schemes with application of induction and maintenance immunosuppressive protocols. In this article, we summarize the current status of immunosuppressive regimens in simultaneous pancreas and kidney transplantation.

Total and free mycophenolic acid and its 7-O-glucuronide metabolite in Chinese adult renal transplant patients: pharmacokinetics and application of limited sampling strategies

OBJECTIVE

This study aimed to investigate the pharmacokinetic characteristics of total and free mycophnolic acid (MPA) and its 7-O-glucuronide metabolite (MPAG) in Chinese renal transplant recipients. In addition, limited sampling strategies were developed to estimate the individual area under concentration curve (AUC) of total and free MPA.

METHODS

Total and free MPA and MPAG concentrations were determined by high performance liquid chromatography. Whole 12-h pharmacokinetic profiles were obtained on the 10th day after operation in 12 adult Chinese de novo renal transplant recipients administrated with mycophenolate mofetil (MMF, 750 mg bid), cyclosporine and corticosteroids. Limited sampling strategies with jackknife technique, a resampling method, and Bland-Altman analysis were employed to develop equations to estimate total and free MPA AUC.

RESULTS

The pattern of total and free MPA and MPAG plasma concentration-time curves in the cohort of patients taking lower doses of MMF was consistent with previous reports of Caucasian patients taking MMF 1 g bid, except that dose-normalized exposure of total and free MPAG was much lower in the current study than in those of the Caucasians. The mean C (max) and AUC(0-12h) of total and free MPA were 9.4 +/- 3.4 mg/L, 20.2 +/- 6.5 mg x h/L and 0.4 +/- 0.4 mg/L, 0.7 +/- 0.5 mg x h/L, respectively, whereas mean C (max) and AUC(0-12h) of total and free MPAG were 97.3 +/- 32.6 mg/L, 656.0 +/- 148.0 mg.h/L and 29.9 +/- 8.5 mg/L, 222.0 +/- 58.1 mg x h/L respectively. The mean fractions of free MPA and MPAG were 3.5 +/- 2.0 and 34.6 +/- 8.0%, respectively. No determinant was identified to influence the pharmacokinetics of total and free MPA and MPAG or the free fraction of MPA and MPAG. The combinations of C (2h)-C (4h) and C (1h)-C (2h)-C (3h) were the best to estimate free and total MPA AUC(0-12h) respectively, whereas the combination of C (2h)-C (3h)-C (4h) and C (1h)-C (2h)-C (4h) was the best to estimate both simultaneously.

CONCLUSION

This is the first time that the pharmacokinetics profile of total and free MPA and its main metabolite MPAG has been examined in Chinese adult renal transplant patients. The limited sampling strategies proposed to estimate individual free and total MPA AUC could be useful in optimizing patient care.

Mycophenolate mofetil in islet cell transplant: variable pharmacokinetics but good correlation between total and unbound concentrations

The authors investigated the pharmacokinetics of mycophenolic acid over 1 year in 8 Caucasian women undergoing islet cell transplantation. Total mycophenolic acid AUC(0-12) mcg x h/mL before day 60 was 62.1-67.8, declining to 33.6-64.7 thereafter (P = .61). Median total trough concentrations were 1.16-2.90 mcg/mL. Unbound AUC(0-12) was 412-673 ng x h/mL and did not change over time (P = .30). Median percent unbound mycophenolic acid was 0.95% of total concentrations. Individual unbound and total mycophenolic acid concentrations were highly correlated (r2 = 0.94). Total mycophenolic acid trough concentration and total AUC(0-12) were modestly correlated (r2 = 0.65). Intra- and interpatient variability of systemic mycophenolic acid exposure was high. Six patients required dose reductions prior to day 60 due to adverse effects. All subjects achieved insulin independence; 3 later lost graft function. The trend toward higher exposure in the early periods followed by dose reductions suggests that lower initial doses and therapeutic drug monitoring may be necessary.

Indications of mycophenolate mofetil in liver transplantation

Mycophenolate mofetil (MMF) is approved for prophylaxis of acute rejection after kidney, heart, and liver transplantation as well as for pediatric patients after kidney transplantation. MMF, a noncompetitive inhibitor of inosine monophosphate dehydrogenase (IMPDH), blocks de novo purine synthesis which leads to an effective inhibition of proliferation selectively in T and B lymphocytes, smooth muscle cells, and fibroblasts. MMF shows additional effects with inhibition of the expression of activating and adhesion molecules on the surface of lymphocytes. The beneficial safety profile with distinct side effects compared to calcineurin inhibitors (CNI) enable efficacious combination with ciclosporin or tacrolimus as de novo therapy after liver transplantation. Furthermore, recent studies show the possibility to reduce CNI induced toxicities by adding MMF to primary immunosuppression. MMF is also used to enable early steroid withdrawal after liver transplantation. MMF can increase efficacy of immunosuppressive therapy and thereby support the treatment of steroid resistant acute rejections, chronic rejections and chronic graft dysfunction.

Successful Pancreas–Renal Transplantation Without Induction Therapy

Most pancreas transplant centers initially use immunosuppression with antilymphocyte induction because the pancreas appears to be a highly immunogeneic organ. Although the addition of an antilymphocyte agent provides enhanced immunosuppression in the early posttransplant period, it is associated with added costs and adverse reactions. In this study we evaluated the safety and efficacy of tacrolimus (Tac), mycophenolate mofetil (MMF), and steroid immunosuppression without induction after simultaneous kidney-pancreas transplantation (SKPT). Six patients (30%) displayed rejection episodes with a mean follow-up of 12 months (range = 4 to 18 months). No graft was lost due to rejection. The results of this series suggest that SKPT can be safely performed without induction therapy.

An evidence-based analysis of simultaneous pancreas-kidney and pancreas transplantation alone

While pancreas transplantation has evolved within two decades from a frustrating and poorly-accepted therapeutic option to a highly successful procedure, the respective benefits of the successive surgical and immunosuppressive developments have remained unclear. The aim of this study was to determine using an evidence-based methodology, which novel approaches have contributed to the current results and whether pancreas transplantation is cost-effective. Out of 2481 articles, 102 analyzed either surgical or immunosuppressive aspects of pancreas transplantation. Urological complications were more frequent in bladder over enteric drainage (range: 62-63% vs. 12-20%, p = 0.0001), but without significant difference in patient or graft survival. Portal drainage was associated with a trend toward fewer complications and better hyperinsulinemia control over systemic drainage in retrospective studies. Immunosuppression combining induction therapy, a calcineurin inhibitor, mycophenolate mophetil (MMF) and corticosteroids were associated with a 40% decreased incidence of rejection (p = 0.01) and an increase in graft survival above 90% at 1 year (p < 0.05). Pancreas transplantation is highly cost-effective compared to conservative alternatives. We conclude that despite a paucity of large studies, enteric drainage should be recommended but the benefits of portal venous drainage remain debated. Quadruple immunosuppression protocols including induction therapy should be the standard regimen.

Mychophenolate mofetil increased chagas disease reactivation in heart transplanted patients: comparison between two different protocols

Heart transplantation (HT) remains the treatment of choice for advanced chagasic cardiomyopathy. New immunosuppression protocols have provided better control of rejection (RJ) and cardiac allograft vasculopathy. However, their influence on infection and Chagas disease reactivation (CDR) is not well established. The aim of this study was to compare the CDR rate in patients under two different immunosuppression protocols. We studied 39 chagasic patients who had undergone orthotopic HT between April, 1987 and June, 2004. They were divided into two groups, one taking azathioprine (group 1=24 patients) and the other taking mycophenolate mofetil (group 2=15 patients), in the standard doses (2 mg/kg/day and 2 g/day, respectively), beside prednisone and cyclosporine, in equivalent doses. The number of CDR and RJ episodes were analyzed in the first and second years after HT. CDR rates were 8%+/-5% at 1 year and 12%+/-6% at 2 years of follow-up in group 1. Otherwise, patients in group 2 presented CDR rates of 75%+/-10% and 81%+/-9% at the same periods, respectively (p<0.0001, hazard ratio=6.06). When comparing RJ rates in the first year after HT, both groups had similar behavior under both immunosuppression protocols (p=0.88). These data show that current prescribed doses of mycophenolate mofetil increase the early risk of CDR without changing RJ incidence in this period.

Prospective, randomized trial of the effect of antibody induction in simultaneous pancreas and kidney transplantation: three-year results

BACKGROUND

Historically, antibody induction has been used because of the higher immunologic risk of graft loss or rejection observed in simultaneous pancreas and kidney (SPK) transplantation compared with kidney transplantation alone. This trial was designed to assess the effect of antibody induction in SPK transplant recipients receiving tacrolimus, mycophenolate mofetil, and corticosteroids. Induction agents included T-cell-depleting and interleukin-2 receptor antibodies.

METHODS

A total of 174 SPK transplant recipients were enrolled in a prospective, open-label, multi-center study. They were randomized to induction (n=87) or non-induction (n=87) groups and followed for 3 years.

RESULTS

At 3 years, actual patient (94.3% and 89.7%) and pancreas (75.9% and 75.9%) survivals were similar between the induction and non-induction groups, respectively. Actual kidney survival was similar at 1 and 2 years, but at 3 years, it was significantly better in the induction group compared with the non-induction group (92% vs. 81.6%; P =0.04). At 3 years, median serum creatinine and hemoglobin A1C were similar between the induction and non-induction groups (1.35 mg/dL and 1.20 mg/dL, 5.4% and 5.5%, respectively). Three-year cumulative incidence of biopsy-confirmed, treated acute kidney rejection in the induction and non-induction groups was 19.5% and 27.5% (P =0.14), respectively, with odds 4.6 times greater in African Americans regardless of treatment (P =0.004). Significantly higher rates of cytomegalovirus (CMV) viremia and CMV syndrome occurred in those receiving T-cell-depleting antibody induction (36.1%) when compared with those receiving anti-interleukin-2 receptor antibodies (2%) and non-induction (8.1%) (P <0.0001).

CONCLUSIONS

Tacrolimus, mycophenolate mofetil, and corticosteroids resulted in excellent safety and efficacy in SPK transplant recipients. Actual 3-year kidney survival was significantly better in the induction group; however, CMV viremia and CMV syndrome rates were significantly higher in the T-cell-depleting antibody group. African Americans demonstrated a significantly greater risk of acute rejection despite antibody induction. Decisions regarding the use of induction therapy must weigh the risk of kidney graft loss or rejection against the risk of infection.

Single-Center, open, prospective, randomized pilot study comparing cyclosporine versus tacrolimus in simultaneous Pancreas-Kidney transplantation

BACKGROUND

Although tacrolimus (Prograf) is the calcineurin inhibitor usually employed in simultaneous pancreas-kidney transplantation (SPKTx), no prospective randomized studies have compared its efficacy to cyclosporine (Neoral), when either drug is used in combination with mycophenolate mofetil (MMF) and the pancreas is drained into the portal vein.

METHODS

Between May 2001 and June 2003, 16 SPKTx recipients were randomized to be prescribed Neoral and 17 Prograf in addition to basiliximab, steroids, and MMF. All pancreata were drained into the portal vein.

RESULTS

After a median follow-up of 15.6 months, six kidney acute rejection episodes were observed with Prograf (36.5%; one steroid-resistant) and one Neoral (n = 1, 6.2%; P =.04). No pancreas rejection episode was recorded. Two infections occurred in two recipients from each group. No major adverse events were noted other than a severe hematological toxicity (Prograf). Metabolic parameters were equivalent in the two groups, save for higher total cholesterol (212 +/- 39 mg/dL vs 173 +/- 23 mg/dL; P =.008), LDL (129 +/- 33 mg/dL vs 101 +/- 21 mg/dL; P =.029), and triglyceride (191 +/- 86 mg/dL vs 126 +/- 40 mg/dL; P =.028), values with Neoral, although the same differences were already present at baseline. One recipient (Neoral) died with functioning grafts. Patient, pancreas, and kidney survival rates were all 94% for Neoral versus 100% for Prograf.

CONCLUSIONS

Although a larger series and a longer follow-up are needed, Neoral and Prograf used in combination with MMF seem to achieve equivalent success rates among primary SPKTx when the pancreas is drained into the portal vein.

Immunosuppression in pancreas transplantation: mycophenolate mofetil versus sirolimus

The use of mycophenolate mofetil (MMF) in pancreas transplantation has increased graft survival and decreased the incidence of acute rejections episodes (ARE), regardless of the choice of calcineurin inhibitor. The combination of MMF with tacrolimus (TAC) is the most common protocol, it is considered the gold standard for new protocols. In the last few years, there have been reports of a small number of patients treated with sirolimus (RAPA), usually combined with TAC. Patient and pancreas survival rates as well as the incidence of ARE were similar to protocols with TAC and MMF. Twenty simultaneous pancreas and kidney (SPK) transplantations were performed using an immunosuppressive protocol of TAC, RAPA, and steroids (STE) after 2000. The incidence of ARE was 25%; all episodes responded to STE. Only 2 patients (10%) displayed hypercholesterolemia requiring treatment with statins. The use of RAPA as an alternative to MMF is promising, although presently one with limited experience. The combination of MMF and RAPA with or without a calcineurin inhibitor is an option to be evaluated in the future.

Mycophenolate mofetil in solid-organ transplantation

This review focuses on the use of mycophenolate mofetil (MMF) as an immunosuppressive agent in solid-organ transplantation. MMF, a non-competitive inhibitor of inosine monophosphate dehydrogenase, blocks de novo purine synthesis in T and B lymphocytes, resulting in the selective inhibition of proliferation of these cells in response to antigenic stimuli. MMF may also promote apoptosis of these cells. The immunosuppressive ability of MMF is thought to derive mainly from the inhibition of inosine monophosphate dehydrogenase. The other effects of MMF include suppression of antibody synthesis by B lymphocytes, inhibition of proliferation of smooth muscle cells in culture and impaired glycosylation of adhesion molecules. MMF may exhibit anti-inflammatory effects resulting from decreased activity of the inducible form of nitric oxide synthase, a consequence of depletion of tetrahydrobiopterin, which leads to decreased generation of peroxynitrite, a pro-inflammatory molecule. The pharmacokinetics, pharmacodynamics and principles underlying therapeutic drug monitoring of MMF are reviewed. The results of the pivotal clinical trials of MMF in kidney and heart transplantation are discussed and a summary of the major studies demonstrating a positive effect of MMF on renal transplantation outcomes is presented. The use of MMF in the context of ABO-incompatible renal transplantation, renal transplantation in highly sensitised and cross-match positive recipients, humoral rejection of renal allografts, chronic allograft nephropathy and steroid/calcineurin inhibitor minimisation in renal transplantation are also discussed.

Long-term experience with simultaneous kidney-pancreas transplantation with portal-enteric drainage and tacrolimus/mycophenolate mofetil-based immunosuppression

Refinements in surgical techniques and advances in clinical immunosuppression have led to steadily improving results in pancreas transplantation (PTX). Although there is renewed interest in enteric exocrine drainage, most PTXs are performed with systemic venous delivery of insulin. To improve the physiology of PTX, we developed a novel technique of portal venous delivery of insulin and enteric drainage of the exocrine secretions (portal-enteric [P-E]). The purpose of the study was to analyse outcomes in patients undergoing PTX with P-E drainage and contemporary immunosuppression.

MATERIALS AND METHODS

From January 1997 through September 2002, we performed 67 primary simultaneous kidney-PTXs (SKPT) with P-E drainage. Maintenance immunosuppression consisted of tacrolimus (TAC), mycophenolate mofetil (MMF) and steroids. No antibody induction therapy occurred in 33 patients (49%) with the remainder receiving daclizumab (n = 15), basiliximab (n = 2), or thymoglobulin (n = 14) induction therapy. The patient group included 38 males and 29 females with a mean age of 39.7 year (range 23-58) and a mean duration of pretransplant diabetes of 24.5 year (9-46). Fourteen patients (21%) were African-American.

RESULTS

The mean waiting time for SKPT was 3.3 months (range 0.1-10). Mean kidney and pancreas cold ischaemia times were 15.1 and 15.4 h, respectively. Patient, kidney and pancreas graft survival rates were 97%, 92.5% and 82%, respectively, with a mean follow-up of 20 months (range 1-56). Two deaths (one sepsis, one cardiac event) occurred at 1 month after SKPT; both patients died with functioning grafts (DWFG). Three patients (4.5%) had delayed renal allograft function and received temporary dialysis after SKPT. Five kidney graft losses occurred (two DWFG, one thrombosis, two chronic rejection). All but four patients (6%) had immediate PTX function. A total of 12 pancreas graft losses occurred (two DWFG, five thrombosis, five chronic rejection). The incidence of acute rejection was 28%, but no grafts were lost due to isolated acute rejection. The incidence of major infection was 51%, but only five patients (7.5%) developed cytomegalovirus infection. A total of 19 patients (28%) underwent early relaparotomy within 3 months of SKPT. The composite endpoint of no rejection, graft loss, or mortality was attained by 63% of patients. At present, 58 patients (87%) are both dialysis and insulin-independent (including four retransplants).

CONCLUSION

These findings suggest that SKPT with P-E drainage and contemporary immunosuppression may result in excellent intermediate-term outcomes.

Prospective, randomized, multi-center trial of antibody induction therapy in simultaneous pancreas-kidney transplantation

A randomized, multicenter, prospective study was conducted at 18 pancreas transplant centers in the United States to determine the role of induction therapy in simultaneous pancreas-kidney (SPK) transplantation. One hundred and 74 recipients were enrolled: 87 recipients each in the induction and noninduction treatment arms. Maintenance immunosuppression consisted of tacrolimus, mycophenolate mofetil, and corticosteroids. There were no statistically significant differences between treatment groups for patient, kidney, and pancreas graft survival at 1-year. The 1-year cumulative incidence of any treated biopsy-confirmed or presumptive rejection episodes (kidney or pancreas) in the induction and noninduction treatment arms was 24.6% and 31.2% (p = 0.28), respectively. The 1-year cumulative incidence of biopsy-confirmed, treated, acute kidney allograft rejection in the induction and noninduction treatment arms was 13.1% and 23.0% (p = 0.08), respectively. Biopsy-confirmed kidney allograft rejection occurred later post-transplant and appeared to be less severe among recipients that received induction therapy. The highest rate of Cytomegalovirus (CMV) viremia/syndrome was observed in the subgroup of recipients who received T-cell depleting antibody induction and received organs from CMV serologically positive donors. Decisions regarding the routine use of induction therapy in SPK transplantation must take into consideration its differential effects on risk of rejection and infection.

Technical and immunologic progress in simultaneous pancreas-kidney transplantation

BACKGROUND

During the past few years the use of new immunosuppressants and refinements in surgical technique of simultaneous pancreas-kidney (SPK) transplantation have resulted in markedly improved outcomes. This is a retrospective study of 208 SPK transplants performed at Northwestern University, demonstrating the advances made at a single center that are reflective of the field at large.

METHODS

An 8.5-year time span was split into 4 distinct eras marking sequential changes in immunosuppression and surgical technique that ensued. SPK transplant outcomes of patient and graft survival and rejection rates were compared. Also examined were end points related to the changing risk profile of the recipients, as well as quality of allograft function and rates of rehospitalizations.

RESULTS

Recipients receiving tacrolimus/mycophenolate mofetil-based immunosuppression had patient, kidney, and pancreas survival rates significantly higher than those of earlier cohorts. The elimination of corticosteroids did not reduce survival rates or increase rejection risk. The use of pancreatic exocrine enteric drainage technique over bladder drainage reduced rehospitalizations.

CONCLUSIONS

Advances in immunosuppression management combined with technical refinements have made SPK transplantation a safer and more effective treatment option for the diabetic, uremic patient.

Duodenal histology for monitoring treatment of acute rejection in pancreaticoduodenal allografts in rats

BACKGROUND

Although the value of duodenal histology as a means to diagnose acute rejection in pancreaticoduodenal allografts has been validated, it is not known how the duodenum responds to antirejection treatment in comparison with the pancreas.

METHODS

Diabetic Lewis rats received a pancreaticoduodenal allograft. Cyclosporine was given for 5 days and then discontinued for 2 days (group 1), for 4 days (group 2), for 6 days (group 3), for 8 days (group 4), for 9 days (group 5), and for 10 days (group 6). Two animals of each group were killed for histology at the end of immunosuppressive-free intervals. In the remaining rats, rejection was treated with methylprednisolone on 3 consecutive days. Duodenal histology was compared with pancreatic morphology before and after treatment of rejection.

RESULTS

Duodenal histology had a positive and negative predictive value of 100% for detection of acute rejection in the pancreatic portion of the graft. After antirejection treatment, duodenal morphology was however less accurate (positive predictive value, 96%; negative predictive value, 67%). The Spearman correlation coefficient (p) of duodenal and pancreatic rejection grades was higher before antirejection treatment (p=1.0) than thereafter (p=0.724). Considering interstitial and vascular changes separately, vascular rejection correlated to a higher extent than interstitial rejection between the two portions of the graft (p=0.725 vs. p=0.677).

CONCLUSIONS

Duodenal histology accurately predicts the initial diagnosis of rejection of the pancreas. However, after treatment of acute rejection, duodenal morphology is more likely to recover from rejection than the pancreas. Awareness of this phenomenon might be important for the interpretation of duodenal follow-up biopsies.

Risk factors and impact of cytomegalovirus disease in simultaneous pancreas-kidney transplantation

BACKGROUND

The relevance of cytomegalovirus (CMV) in simultaneous pancreas kidney (SPK) transplant recipients in the modern era of immunosuppression and antiviral therapeutics is largely unquantified. We sought to determine the risk factors of CMV disease and its impact on SPK transplant outcomes in recipients all receiving a consistent regime of maintenance immunosuppression and CMV prophylaxis.

METHODS

This is a retrospective, single center study of 100 consecutive SPK transplant recipients. All received maintenance immunosuppression with mycophenolate mofetil, tacrolimus, and prednisone. CMV prophylaxis consisted of a short course of parenteral gancyclovir followed by oral gancyclovir. Recipients at high-risk (D+/R-) for CMV also received CMV hyperimmune globulin. Multivariate analysis of risk factors for CMV disease and risk factors for adverse outcomes in SPK transplantation were determined. The effect of duration of prophylaxis on timing and severity of CMV disease in high-risk (D+/R-) SPK transplant recipients was also evaluated.

RESULTS

The actual 1-year rate of CMV disease was 17.0% (12.0% noninvasive, 5.0% tissue invasive); and according to donor and recipient CMV serological status was: D-/R+: 0%; D-/R-: 2.8%; D+/R+: 25.6%; and D+/R-: 40.6%. Multivariate analysis showed transplantation of organs from a donor with positive CMV serology to be predictive of CMV disease with a relative risk of 63.37 (P=0.0052). In the high-risk (D+/R-) subgroup, the duration of prophylactic therapy delayed onset of CMV disease, but had minimal effect on severity. Invasive CMV disease was an independent predictor of mortality but did not decrease kidney or pancreas allograft survival.

CONCLUSIONS

Outcomes of SPK transplantation have improved in the current era of modern immunosuppression, yet CMV remains an important pathogen. The serological status of the organ donor and the duration of CMV prophylaxis are predictive of who and when CMV disease may occur. Nevertheless, new strategies that reduce risk and severity of CMV disease are still needed.

Comparison of azathioprine and mycophenolate mofetil for the prevention of acute rejection in recipients of pancreas transplantation

The study was performed to compare the efficacy and side effects of azathioprine (AZA) and mycophenolate mofetil (MMF) in conjunction with cyclosporine or tacrolimus and steroids for the prevention of acute pancreas rejection during the first 6 months of pancreas transplantation. In this case-controlled study, MMF is compared with historical controls of AZA in the prevention of acute pancreas rejection. The primary measures of treatment efficacy were patient and pancreas survival rate at 6 months after transplantation. Secondary efficacy measures were the occurrence of biopsy-proven pancreas rejections and the use of antilymphocyte preparations for rejection treatment. A total of 111 pancreas transplant patients (57 in the AZA group and 54 in the MMF group) were evaluated. The 6-month patient survival rate was 96% in the AZA group versus 97% in the MMF group (p = 0.57). The 6-month pancreas graft survival rate was 88% in the AZA group versus 91% in the MMF group (p = 0.29). However, biopsy-proven rejection episodes during the first 6 months of transplantation were significantly lower with MMF (46%) than with AZA (69%) (p = 0.01). In addition, patients in the AZA group received a greater number of full courses of antilymphocyte therapy as a rejection treatment (p = 0.004). Overall, the frequency of adverse events was similar, although the MMF group experienced higher incidences of gastrointestinal adverse events. In conclusion, compared with AZA, MMF significantly reduces the rate of biopsy-proven pancreas rejection during the first 6 months of transplantation and is well tolerated, except for gastrointestinal adverse events.

Lessons learned from more than 1,000 pancreas transplants at a single institution

OBJECTIVE

To determine outcome in diabetic pancreas transplant recipients according to risk factors and the surgical techniques and immunosuppressive protocols that evolved during a 33-year period at a single institution.

SUMMARY BACKGROUND DATA

Insulin-dependent diabetes mellitus is associated with a high incidence of management problems and secondary complications. Clinical pancreas transplantation began at the University of Minnesota in 1966, initially with a high failure rate, but outcome improved in parallel with other organ transplants. The authors retrospectively analyzed the factors associated with the increased success rate of pancreas transplants.

METHODS

From December 16, 1966, to March 31, 2000, the authors performed 1,194 pancreas transplants (111 from living donors; 191 retransplants): 498 simultaneous pancreas-kidney (SPK) and 1 simultaneous pancreas-liver transplant; 404 pancreas after kidney (PAK) transplants; and 291 pancreas transplants alone (PTA). The analyses were divided into five eras: era 0, 1966 to 1973 (n = 14), historical; era 1, 1978 to 1986 (n = 148), transition to cyclosporine for immunosuppression, multiple duct management techniques, and only solitary (PAK and PTA) transplants; era 2, 1986 to 1994 (n = 461), all categories (SPK, PAK, and PTA), predominantly bladder drainage for graft duct management, and primarily triple therapy (cyclosporine, azathioprine, and prednisone) for maintenance immunosuppression; era 3, 1994 to 1998 (n = 286), tacrolimus and mycophenolate mofetil used; and era 4, 1998 to 2000 (n = 275), use of daclizumab for induction immunosuppression, primarily enteric drainage for SPK transplants, pretransplant immunosuppression in candidates awaiting PTA.

RESULTS

Patient and primary cadaver pancreas graft functional (insulin-independence) survival rates at 1 year by category and era were as follows: SPK, era 2 (n = 214) versus eras 3 and 4 combined (n = 212), 85% and 64% versus 92% and 79%, respectively; PAK, era 1 (n = 36) versus 2 (n = 61) versus 3 (n = 84) versus 4 (n = 92), 86% and 17%, 98% and 59%, 98% and 76%, and 98% and 81%, respectively; in PTA, era 1 (n = 36) versus 2 (n = 72) versus 3 (n = 30) versus 4 (n = 40), 77% and 31%, 99% and 50%, 90% and 67%, and 100% and 88%, respectively. In eras 3 and 4 combined for primary cadaver SPK transplants, pancreas graft survival rates were significantly higher with bladder drainage (n = 136) than enteric drainage (n = 70), 82% versus 74% at 1 year (P =.03). Increasing recipient age had an adverse effect on outcome only in SPK recipients. Vascular disease was common (in eras 3 and 4, 27% of SPK recipients had a pretransplant myocardial infarction and 40% had a coronary artery bypass); those with no vascular disease had significantly higher patient and graft survival rates in the SPK and PAK categories. Living donor segmental pancreas transplants were associated with higher technically successful graft survival rates in each era, predominately solitary (PAK and PTA) in eras 1 and 2 and SPK in eras 3 and 4. Diabetic secondary complications were ameliorated in some recipients, and quality of life studies showed significant gains after the transplant in all recipient categories.

CONCLUSIONS

Patient and graft survival rates have significantly improved over time as surgical techniques and immunosuppressive protocols have evolved. Eventually, islet transplants will replace pancreas transplants for suitable candidates, but currently pancreas transplants can be applied and should be an option at all stages of diabetes. Early transplants are preferable for labile diabetes, but even patients with advanced complications can benefit.

Trends and perspectives in pancreas and simultaneous pancreas and kidney transplantation

Pancreas transplantation is still the best option to achieve normoglycaemia and insulin independence in patients with type I diabetes. As a result of improvements in surgical techniques, immunosuppression and patient selection, one year survival rates of 95, 83, and 88% for patient, pancreas, and kidney survival, respectively, are reported for patients with simultaneous pancreas and kidney transplantation. The main goals for the future are to reduce postoperative morbidity, to identify the relevant indications for single pancreas transplantation, to adopt the best surgical technique for individual patients' needs (bladder versus enteric drainage with or without portal venous delivery of insulin), and to develop immunosuppressive strategies with low nephrotoxic and diabetogenic potential.

Improved solitary pancreas transplant graft survival in the modern immunosuppressive era

The results of solitary pancreas (SP) transplantation have traditionally lagged behind those of simultaneous pancreas-kidney (SPK) transplantation. This is one of the chief factors that has limited the wide-scale application of SP transplantation in nonuremic type I diabetic patients. The purpose of this study is to report our present experience with SP transplantation and compare it to a prior experience. Twenty-three SP transplants (14 PAK, 4 PTA, and 5 PASPK) performed since January 1997 were compared to 56 SP transplants (53 PAK, 1 PTA, and 2 PASPK) performed before 1994. Between 1993 and 1997, SP transplants were not performed because of high morbidity in the early experience. Early SP transplants were performed using bladder drainage of exocrine secretions, and enteric drainage without a Roux-en-Y was used in the recent series. In the early era, immunosuppressive therapy included cyclosporine (CsA), azathioprine (AZA), corticosteroids, and in half of the patients, ALG or OKT3. Recent SP transplants received tacrolimus (TAC). mycophenolate mofetil (MMF), corticosteroids, and induction with either anti-thymocyte globulin (n = 9), OKT3 (n = 1), daclizumab (n = 5), or basiliximab (n = 8). The 1-year Kaplan-Meier patient survival was 85% in the early era and 100% in the recent group of patients (p = 0.08). In the previous era, four patients suffered significant decrement in renal function, necessitating dialysis or kidney transplantation following pancreas transplantation. All patients transplanted since 1997 maintain near prepancreas transplant levels of renal function (mean pretransplant serum creatinine (Cr) 1.3 +/- 0.3 mg/dl vs, mean current Cr 1.4 +/- 0.4 mg/dl, p = NS]. The 1-year Kaplan-Meier graft survival (insulin independence) of recent SP transplants was 87%, whereas for prior SP transplants it was 19% (p = 0.0001). The rate of acute pancreas rejection was significantly different between the two groups. Of early SP transplants, 76% experienced at least one rejection episode within the first year. In contrast, 35% of recent SP transplants suffered acute rejection during the same time period (p = 0.04). Current experience with SP transplantation demonstrates improved graft survival and reduced rejection rates with the use of newer immunosuppressive agents.

Portal venous and enteric exocrine drainage versus systemic venous and bladder exocrine drainage of pancreas grafts: clinical outcome of 40 consecutive transplant recipients

OBJECTIVE

To test the hypothesis that pancreas transplantation using the more physiologic method of portal venous-enteric (PE) drainage could be performed without compromising patient and graft outcome, compared with the standard method of systemic venous-bladder (SB) drainage.

METHODS

Between November 1995 and November 1998, the authors prospectively followed up 20 consecutive patients with SB drainage followed by 20 consecutive patients with PE drainage. All patients underwent simultaneous pancreas-kidney transplantation, and all were immunosuppressed with antilymphocyte serum, cyclosporin, azathioprine, and steroids.

RESULTS

The actuarial patient survival rate at 1 year was 95% in the SB group and 100% in the PE group. Death-censored kidney graft survival was 100% in both groups; pancreas graft survival was 95% in the SB group and 100% in the PE group. The mean initial hospital stay was 15 days for both groups. However, during the first 6 months after transplantation, the SB group required more medical day-unit visits, mostly for treatment of metabolic acidosis and dehydration. The incidence of urinary tract infections was similar in both groups. The incidence of cytomegalovirus infections was significantly less in the PE group. The incidence of acute rejection was 37% in the SB group and 15% in the PE group. Mean serum creatinine levels 6 months after transplantation were significantly lower in the PE group than in the SB group. Glycemic control was excellent in both groups, but fasting serum insulin levels were significantly lower in the PE group.

CONCLUSIONS

The PE method of pancreas transplantation can be performed with excellent patient and graft outcomes.

Mycophenolate mofetil impairs the maturation and function of murine dendritic cells

The immunosuppressive drug, mycophenolate mofetil (MMF), has been successfully introduced in allogeneic transplantation medicine and, more recently, in the treatment of autoimmune skin disorders. MMF inhibits lymphocyte proliferation via a blockade of the enzyme inosine 5'-monophosphate dehydrogenase, an enzyme on which lymphocytes solely depend to generate the purines necessary for DNA/RNA synthesis. To investigate the effects of MMF on cutaneous immune responses, a murine model of contact hypersensitivity (CHS) was used, with oxazolone or trinitrochlorobenzene as a contact allergen. Compared with the respective vehicle, i.p. applied MMF significantly inhibited the elicitation and, surprisingly, the induction of CHS responses. This prompted further studies into the effects of MMF on Ag presentation. Bone marrow-derived dendritic cells (DC) were cultured with GM-CSF and IL-4 in the presence of MMF and were tested for their Ag-presenting capacity. Sensitization and elicitation of CHS and delayed-type hypersensitivity responses by s. c. injected haptenated DC were reduced upon preincubation of DC with MMF. CHS responses were not impaired upon resensitization, indicating that MMF does not induce hapten-specific immunotolerance. In addition, MMF decreased the ability of DC to stimulate allogeneic T cells in MLR assays. Accordingly, flow cytometric analyses revealed a dose-dependent reduction of the expression of CD40, CD80, CD86, I-A, and ICAM-1 on DC with a concurrent reduction of IL-12 production. These data suggest that MMF, in addition to affecting T lymphocytes, directly affects APC, resulting in an impairment of immune responses. They furthermore point to a possible role of inosine 5'-monophosphate dehydrogenase in the maturation of DC.

A single center's clinical experience with quadruple immunosuppression including ATG or IL2 antibodies and mycophenolate mofetil in simultaneous pancreas-kidney transplants

Acute rejection remains a major problem in simultaneous pancreas-kidney (SPK) transplant and occurs in 60-100% of the cases. With the introduction of mycophenolate mofetil (MMF) replacing azathioprine (AZA) as a basis immunosuppressant, reduced rates of rejection have been reported. This study investigates the frequency and clinical relevance of allograft rejection in SPK patients receiving antithymocyte globulin (ATG) or Basiliximab induction therapy and cyclosporine Neoral (CyA), MMF, steroid basis immunosuppression. Between December 1996 and October 1999, 21 consecutive patients (15 males, 6 females) received a SPK transplant at our institution with a mean +/- standard deviation (SD) age of 42 +/- 6 yr. Of these, 14 patients were treated with anti-thymocyte globulin (ATG) Fresenius (rabbit) 3-5 mg/kg for 6 +/- 2 d, cyclosporine Neoral (CyA) (trough levels 350-400 ng/mL), MMF 3 g/d and low dose steroid therapy. Seven SPK patients were treated with Basiliximab (Simulect, Novartis 20 mg on d 0 and d 4 post-transplant) instead of ATG. The patients had an average human leucocyte antigen (HLA) mismatch of 3.9/6 and a negative cross match. All patients remained on triple drug therapy. Three patients were switched to tacrolimus instead of Neoral for CyA intolerance. The mean +/- SD cold ischemia time (CIT) of the organs was 10.1 +/- 2.4 h for the pancreas and 10.5 +/- 2.6 h for the kidney.

RESULTS

Biopsy-proven rejection occurred in the kidney of 1 ATG patient (8%), which responded to steroid bolus therapy. One of the patients (14%) with Basiliximab induction developed renal allograft rejection, which was resolved after a 6-d course of anti-CD3 mAb (OKT3) treatment. All patients (100%) were free from rejection in the pancreas, as measured by urine amylase levels and glycemic control without the need for exogenous insulin with a mean glycosylated hemoglobin (HBA1C) of 5.1 +/- 0.7%, and serum creatinine with a mean of 1.24 +/- 0.24 mg/dL in a mean follow-up period of 17 +/- 15 months (median 12, range 2 37).

CONCLUSION

Triple drug immunosuppression including cyclosporine, MMF and low dose steroids with ATG or interleukin 2 (IL2) receptor antibodies induction therapy appears to be a very suitable immunosuppressive regimen for combined pancreas-kidney transplant (PKT) with a marked reduction in the incidence of rejection.

Immunologic Aspects of Transplant Management: Pharmacotherapy and Rejection

The intensivist caring for the critically ill transplant patient must be knowledgeable in the management of immunosuppression or have expert help. Critical illness often has a major impact on the absorption and metabolism of immunosuppressive drugs, increasing or decreasing net immunosuppression. Too little immunosuppression brings the risk of graft loss, while too much increases the morbidity and mortality of serious infection. Optimum management often requires the skillful manipulation of dosage and/or routes of drug delivery. In many cases of life-threatening infection, immunosuppression must be discontinued altogether and restarted prior to significant graft injury. The cost of miscalculation is very high. Loss of a renal, pancreas, or small bowel transplant is tragic, while loss of a heart, lung, or liver is usually fatal. Unfortunately the management of immunosuppression is becoming more complex. As the field of transplantation matures, new immunosuppressants are being introduced. Also, more experience and growing numbers of clinical trials are making the required knowledge base ever larger. Each type of transplant has its own set of evolving immunosuppression strategies. This review presents the basic mechanisms of the most widely used drugs and the dangers of immunosuppression. The drugs are then discussed in the context of liver, small bowel, kidney, pancreas, heart, and lung transplantation. Finally, a brief section on the practical pharmacokinetics of the drugs is presented.

The use of mycophenolate mofetil in transplant recipients

With the development of new immunosuppressive agents, the focus of anti-rejection therapy has shifted from prevention of acute allograft rejection to an emphasis on sufficient immunosuppression with minimal toxicity. Mycophenolate mofetil (MMF) is a recently developed immunosuppressive drug, which acts to inhibit T and B cell proliferation by blocking the production of guanosine nucleotides required for DNA synthesis. It also prevents the glycosylation of adhesion molecules that are involved in attachment of lymphocytes to endothelium and potentially in leukocyte infiltration of an allograft during an immune response. High-quality randomized clinical trials have demonstrated that MMF, when used with cyclosporine (CsA) and steroids, reduces the frequency and severity of acute rejection episodes in kidney and heart transplants, improves patient and graft survival in heart allograft recipients and increases renal allograft survival at 3 years. It has also been effective in reversing acute and resistant rejection episodes in heart, kidney and liver recipients. The ability of MMF to facilitate sparing of other immunosuppressive agents, particularly in CsA-related nephrotoxicity, is also promising. By permitting reduction in CsA doses, MMF may stabilize or improve renal graft function in patients with CsA-related nephrotoxicity or chronic allograft nephropathy. Early results of phase I and II trials evaluating MMF therapy in liver and combined pancreas/kidney transplant recipients are encouraging. The main adverse effects associated with oral or intravenous MMF are gastrointestinal and hematologic in nature. Although the direct costs of using MMF vs. azathioprine (AZA) are higher, the decreased incidence and treatment of acute rejection in patients treated with MMF supports its use as a cost-effective option during the first year following transplantation.Thus, MMF has become an important therapeutic tool in the transplant clinician's armamentarium. Ongoing issues to be resolved in clinical trials include the role of MMF in the absence of other potent agents, e.g., as monotherapy or with a steroid but without calcineurin inhibitor; whether MMF will have an impact on chronic allograft dysfunction; and the cost-effectiveness of treatment following the first year of transplantation.

Maintenance immunosuppression: new agents and persistent dilemmas

Since the approval of cyclosporine in 1983, only 3 drugs, mycophenolate mofetil, tacrolimus, and sirolimus, have been approved for maintenance immunosuppression in renal transplant recipients. All 3 agents decrease the incidence of early acute allograft rejection. An increase in intermediate and long-term graft survival has not been shown. However, survival data from these clinical trials should be interpreted with caution because the studies were not designed for this purpose. All 3 drugs have significant, albeit different, safety profiles. It remains to be seen whether, the lower incidence of hypertension and hyperlipidemia seen in tacrolimus-treated patients will reduce the incidence and severity of the cardiovascular disease experienced by renal transplant recipients. Sirolimus causes severe hyperlipidemia, and the long-term consequences both on the pathogenesis of cardiovascular disease and on lipid-associated renal injury have yet to be determined. Tacrolimus and mycophenolate mofetil appear to increase graft survival in pancreas-kidney recipients but their efficacy in another high-risk group, African-American recipients, has not yet been clearly shown. However, the trend toward improved graft survival in African-American recipients treated with tacrolimus is encouraging. Steroid-withdrawal remains a goal in the posttransplant period. The available data from steroid-withdrawal and steroid-avoidance clinical trials are mixed. Steroid withdrawal can be achieved in about 50% of patients on a cyclosporine-based immunosuppression regimen. Steroid-withdrawal under coverage of tacrolimus, mycophenolate mofetil or Neoral (Novartis Pharmaceuticals, East Hanover, NJ) may be more successful than that achieved in patients receiving Sandimmune (Novartis Pharmaceuticals). Further studies are needed in this area.