Calcineurin Inhibitors in Renal Transplantation Still Needed but in Reduced Doses: A Review

Despite their contribution in the success of organ transplantation, calcineurin inhibitors (CNIs) may be responsible for frequent and severe side effects that can affect graft survival and life expectancy. In this article, we have reviewed registry studies and randomized controlled trials (RCTs) that seek to avoid, withdraw, or minimize CNIs in renal transplant recipients. Attempts to completely avoid CNIs by administering mycophenolate mofetil (MMF) and/or sirolimus (SRL) have resulted in increased risks of rejection and side effects, with small advantage to improve renal graft function. Early withdrawal of CNIs after transplantation using administration of MMF can improve graft function but may be associated with a greater risk of acute or chronic rejection and graft failure. RCTs in which CNIs were replaced a few months after transplantation by SRL reported improved graft function among SRL-treated patients, but such a treatment was complicated by iatrogenic toxicity. Late replacement of CNIs with SRL did not produce a particular advantage and again was complicated by more frequent side effects. On the basis of these trials, it seems that CNI elimination can trigger rejection or side effects. Recent RCTs showed that minimization of CNI doses in association with everolimus does not increase the risk of rejection, allows one to obtain good graft function, and is well tolerated. Such an approach seems therefore preferable to complete elimination of CNIs with substitution of the current immunosuppressive drugs.     

The evolving role of alemtuzumab (Campath-1H) for immunosuppressive therapy in organ transplantation

Alemtuzumab is a monoclonal anti-CD52 antibody, which has been used extensively off label in solid organ transplantation. Its primary use has been as an induction agent at the time of organ transplantation, although there is limited experience using it to treat steroid-resistant rejection. Prolonged lymphocyte depletion can be expected following alemtuzumab treatment even with one dose of 30 mg intravenously. The nature and kinetics of lymphocyte repopulation depend on the maintenance immunosuppression being administered. In comparison with Thymoglobulin, a polyclonal depleting antibody preparation, alemtuzumab offers significant practical benefits with lower cost, fewer side effects in administration, and no specific issues with i.v. access. The risks and benefits of depleting induction agents, such as alemtuzumab, are compared with nondepleting agents, such as anti-CD25 induction therapy. While the majority of experience in solid organ transplantation has been in kidney transplantation, there is more limited experience in liver, pancreas, islet, small bowel, and lung transplantation. We herein review some of the lessons learned from clinical experience to date in solid organ transplantation using alemtuzumab as an immunosuppressant.     

Successful allotransplantation of encapsulated islets in pancreatectomized canines for diabetic management without the use of immunosuppression

BACKGROUND: Pancreatic islet transplantation has shown great success in the treatment of diabetic patients. However, the required immunosuppressive therapy exposes patients to serious side effects. METHODS: We have designed a novel five-component/three-membrane capsule and encapsulation system to protect the transplanted islet cells from immune system attack while allowing the influx of molecules and nutrients necessary for cell function/survival and efflux of the desired cellular product, specifically insulin, for making recipients healthy. RESULTS: We transplanted encapsulated canine pancreatic islets into the peritoneal cavity of pancreatectomized canines. Transplantation normalized fasting blood glucose levels in nine out of nine dogs for up to 214 days with a single transplantation. Retransplantation was assessed in three animals and encapsulated islets were effective in providing fasting glycemic control after the initial transplantation had run its course. No immunosuppression or anti-inflammatory therapy was used. CONCLUSION: This advancement in transplantation may lead to an alternative approach for islet transplantation treatment for diabetic patients. This approach may also benefit patients suffering from other hormone deficiency diseases including liver disease and Parkinson's disease.     

Pharmacokinetics of Sirolimus and Tacrolimus in Pediatric Transplant Patients

To evaluate the pharmacokinetics of Sirolimus (SRL) and Tacrolimus (TAC) in pediatric transplant recipients. Fifty-one SRL and 55 TAC pharmacokinetic profiles were obtained from 20 male and 14 female recipients of liver alone (LTx, n = 23), small bowel alone, and with liver (SBTx, n = 11). The median age was 13.3 years (range 0.9-23.9). Whole blood concentrations of SRL and TAC were determined by liquid chromatography-mass spectrometry (LC-MS) and microparticulate enzyme immunoassay (MEIA-Abbott Laboratories, IL), respectively. Pharmacokinetic (PK) parameters were derived from noncompartmental model analysis. The half-life was estimated using the data points during the terminal disposition phase and area under the concentration (AUC) time curve was calculated within a dosing interval using the trapezoidal method. The dose of SRL or TAC did not correlate with the corresponding AUCs. Trough concentrations of SRL and TAC correlated well with AUC (r = 0.8544 and 0.8603, respectively). Half-life (h) did not differ significantly between different transplant groups for SRL and TAC (SRL: LTx: 21.2 h, SBTx: 19.3 h; TAC: LTx: 14.1 h, SBTx: 12.7 h). Serial PK analysis with the first measurement within 14 days after transplantation revealed no difference in AUC/dose/BSA for SRL, with time. During this period, SRL half-life increased significantly, from 11.2 +/- 1.0-20.1 +/- 3.1 h (n = 4; p = 0.02). After introduction of SRL, TAC half-life did not change (11.6 +/- 3.9-14.0 +/- 10.4, n = 10, P = 0.52) in all the groups analyzed together. TAC AUC/dose/BSA decreased significantly in LTx and SBTx patients (90.9 +/- 55.3 vs. 48.8 +/- 27.3). Trough concentration measurements provide good estimates of SRL and TAC exposure in pediatric transplant recipients. The short half-life of SRL in children may support twice-daily administration early after liver and small intestinal transplantation. During conversion of subjects from TAC to combined TAC and SRL, aggressive therapeutic drug monitoring must be used to individualize therapy and avoid serous adverse events.     

Resolution of neurotoxicity and beta-cell toxicity in an islet transplant recipient following substitution of tacrolimus with MMF

Calcineurin inhibitors such as tacrolimus have well-recognized efficacy in organ transplantation but side effects of nephrotoxicity, neurotoxicity, and beta-cell toxicity that can be particularly detrimental in islet transplantation. Neuro- and nephrotoxicity have been demonstrated in multiple islet transplant recipients despite the relatively low serum maintenance levels typically used (3-5 ng/ml). We describe a single patient in whom symptoms and signs of neurotoxicity necessitated substitution of tacrolimus with mycophenolate mofetil (MMF), which resulted in complete symptom resolution over the subsequent 9 months. Concomitantly noted were an almost immediate improvement in glycemic control and an improved response to stimulation testing, suggesting remission of tacrolimus-induced beta-cell toxicity and insulin resistance. At 18 months post-"switch," 30 months posttransplant, the patient remains insulin independent with good glycemic control. The goal to remove calcineurin inhibitors from regimens of islet transplantation is a worthy one.     

Comparison of steroid avoidance in tacrolimus/mycophenolate mofetil and tacrolimus/sirolimus combination in kidney transplantation monitored by surveillance biopsy

BACKGROUND: Chronic steroid therapy in kidney transplantation has myriad side effects and steroid avoidance has become feasible. This prospective study compared the safety and efficacy of steroid avoidance in tacrolimus (TAC)/mycophenolate mofetil (MMF) and TAC/sirolimus (SRL) combinations in kidney transplantation. METHODS: In all, 150 kidney recipients were analyzed: 75 each in TAC/MMF and TAC/SRL groups. The primary endpoint was acute rejection. Surveillance biopsies were completed to analyze subclinical acute rejection (SCAR) and chronic allograft nephropathy (CAN). Acute rejection and SCAR were treated by methylprednisolone. Two-year patient and graft survival, renal function, and adverse effects were monitored. RESULTS: Acute rejection was seen in 12% of TAC/MMF and 8% of TAC/SRL patients. Two-year actuarial patient survival was 95% and 97%, and graft survival 90% and 90% in TAC/MMF and TAC/SRL groups, respectively. Surveillance biopsy showed cumulative incidence of SCAR was 27 % in TAC/MMF and 16 % in TAC/SRL groups at 2 years (P = 0.04). Overall, 33% of recipients in TAC/MMF and 20% in TAC/SRL received methylprednisolone for acute rejection/SCAR. Moderate/severe CAN was 10% in TAC/SRL group and 22% in TAC/MMF group(P = 0.06). New-onset diabetes mellitus (NODM) was 4% each in both groups. All recipients remain free of maintenance steroid therapy. CONCLUSIONS: Steroid avoidance in tacrolimus-based immunosuppression with MMF or SRL provides equivalent 2-year patient and graft survival with a low incidence of acute rejection and NODM. SCAR and CAN are lower in TAC/SRL compared to TAC/MMF group. The impact of decreased SCAR and CAN in TAC/SRL group on longer-term graft survival and function is to be evaluated.     

大鼠肝/小肠联合整块移植模型建立

目的建立大鼠肝/小肠联合整块移植模型。方法分别以Wistar和SD大鼠为供、受体进行肝/小肠联合移植,并进行单独肝移植或小肠移植作为对照,不同移植组各取12只受体进行生存期观察。结果肝/肠联合移植手术52次,手术成功43例,成功率82.7%。联合移植组受体有9只(75%)存活时间超过60 d,且小肠移植物存活。单独小肠移植组受体均于20 d内死亡,单独肝移植组10只受体(83.3%)存活60 d以上。结论肝/小肠联合整块移植模型是研究肝/肠联合移植免疫学特性的有力模型。     

Sirolimus in Pediatric Liver Transplantation: A Single-Center Experience

Background and Aims

Liver transplantation (OLT) in children has seen significant improvements in recent years. Long-term immunosuppressive strategies have focused on avoiding the risks of long-term immunosuppression, particularly nephrotoxicity, de novo malignancy and late infections. Since its introduction in renal transplantation in 1999, sirolimus (SRL) has been used by an increasing number of liver transplant centers. The aim of this study was to review the experience using SRL in pediatric liver transplant recipients at a single center.

Methods

Between 1989 and 2006, 318 children underwent OLT including 13 who were converted to SRL therapy because of tacrolimus-related side effects. The indications were posttransplant lymphoproliferative disease (PTLD; n = 11), nephrotoxicity (n = 1), and de novo autoimmune hepatitis (n = 1). One patient with PTLD previously concurrently displayed chronic rejection. SRL dosages ranged between 0.4 and 5 mg/d. The median duration of follow-up was 18 months.

Results

PTLD recurred in 1 patient. There were no episodes of acute rejection. One child developed hyperlipidemia that resolved with diet and medication.

Conclusions

Conversion from tacrolimus to SRL in selected pediatric liver transplant recipients is safe. Children with PTLD may benefit from immunosuppression with SRL after liver transplantation.     

Sirolimus-based immunosuppressive therapy in liver transplant recipient with tacrolimus-related chronic renal insufficiency

BACKGROUND: While providing potent immunosuppression for liver transplant recipients, calcineurin inhibitors (CNI) exhibit nephrotoxicity as a major side effect. The purpose of this study was to evaluate the safety and efficacy of conversion from CNI to sirolimus (SRL) among liver transplant recipients with CNI-induced chronic nephrotoxicity. METHODS: Between January 2004 and June 2005, we performed conversion in 16 recipients after a median period of 8.5 months after liver transplantation. The indication for conversion was CNI-related nephrotoxicity with a serum creatinine (sCr) value >132.6 umol/L. Renal function was measured before and after conversion to SRL. Clinical and laboratory data related to the clinical course of the patients were recorded to investigate the safety and efficacy of conversion. RESULTS: Sixteen patients were converted to SRL after developing nephrotoxicity. Their renal function improved gradually after conversion. The levels of sCr decreased significantly within the first 30 days (164.1 +/- 12.48 micromol/L to 130.1 +/- 5.573 micromol/L), and over the next 60 days after conversion (97.86 +/- 11.69 micromol/L to 90.7 +/- 8.95 micromol/L) (P < .01). Similarly, the mean glomerular filtration rate (GFR) increased significantly during the same period. Four recipients experienced hypercholesterolemia, 1 with ankle edema, and 1 with acute rejection. The median follow-up was 2.4 years. No patient discontinued SRL due to side effects. No patient needed dialysis or kidney transplantation during the study period. CONCLUSIONS: SRL is a safe, effective replacement agent as primary immunosuppressive therapy following withdrawal of CNIs in liver transplant recipients with CNI-induced chronic nephrotoxicity.     

Three Cases of Alopecia Following Clinical Islet Transplantation

Successful clinical islet allotransplantation requires control of both allo‐ and autoimmunity by using immunosuppressant drugs which have a number of side effects. The development of the autoimmune condition alopecia areata following successful islet transplantation is therefore unexpected. Three cases of alopecia affecting female islet transplant recipients are described. In all cases, alopecia developed approximately 7 years after initial transplant. All had received daclizumab, sirolimus and tacrolimus with their initial transplants, but all were receiving a combination of tacrolimus and mycophenolate mofetil at the time alopecia developed. Two subjects had received thymoglobulin for a subsequent islet infusion and prior to the onset of alopecia. The progression of alopecia has been halted or reversed in all cases. Tacrolimus has been continued in two cases (one as monotherapy) while cyclosporine was used in place of tacrolimus in the third case. These three cases represent a crude incidence of <2.5% over 5 years compared with a prevalence of alopecia in islet transplant candidates (pretransplant) of <1%. Although alopecia might be expected in a proportion of individuals with type 1 diabetes, the risk may be increased after islet transplantation, and may be associated with the use of anti‐TNF drugs, lymphodepleting antibodies or higher dose tacrolimus.     

Robust tolerance to fully allogeneic islet transplants achieved by chimerism with minimal conditioning

BACKGROUND: Whether mixed chimeras induced by nonmyeloablative conditioning are tolerant to challenge with donor allogeneic islet grafts is unknown. Here we investigate whether our nonmyeloablative, costimulation blockade-free and sirolimus (SRL)-based protocol could facilitate mixed chimerism via bone marrow transplantation (BMT) and induce islet allograft tolerance. METHODS: After low dose (1-3 Gy) total body irradiation (TBI, day -1), with or without prior lymphocyte depletion, C57BL/6 mice were transfused with 40 x 10(6) BALB/c bone marrow cells (day 0) and received SRL (3 mg/kg/day) for 4 weeks. Chimerism was monitored by flow cytometry and the recipients were rendered diabetic chemically and challenged with donor islets. RESULTS: Mixed chimerism was achieved in mice treated with TBI 3 Gy/SRL but it declined over time in 60% (9/15) of them. Long-term stable chimerism was established in 100% of recipients over 50 weeks with either antilymphocyte serum (ALS, 9/9), anti-CD4 (4/4), or anti-CD4 plus anti-CD8 (5/5) prior to BMT. TBI conditioning could be reduced to 1 Gy, with 90% (9/10) maintaining chimerism in the long-term. When TBI was substituted with cyclophosphamide (CTX) or busulfan (BUS), all mice remained chimeric in the long-term. The chimeras showed no proliferative response to donor antigen and accepted both first and second donor-specific islet grafts indefinitely while rejecting third-party grafts. CONCLUSIONS: This data provides the first evidence that stable fully allogeneic chimeras induced with BMT after nonmyeloablative conditioning with SRL and lymphocyte-depleting antibodies exhibit robust donor-specific tolerance to islet grafts.     

Bcl-2 protection of islet allografts is unmasked by costimulation blockade

One major limitation in pancreatic islet transplantation is availability of donor tissue. Donor shortage is exacerbated by islet apoptosis from the stresses of islet isolation and transplantation. Furthermore, the side effects of immunosuppressive drugs preclude transplants into patients whose diabetes is controlled by parenteral insulin. We hypothesised that over-expressing anti-apoptotic Bcl-2 or secretion of immunomodulatory CTLA4Ig molecules in islet beta cells would enhance survival of transplanted islets while minimizing systemic side effects. Over-expression of Bcl-2 neither significantly increased preservation of islet cell mass after transplantation into immunocompromised recipients nor decreased cytokine-mediated apoptosis in vitro. Although Bcl-2 over-expression alone was insufficient in protecting islet allografts from rejection, its beneficence was shown by the enhancement of protection when the adaptive immune response was inhibited by locally produced CTLA4Ig. Thus, the combination of anti-apoptotic and immunosuppressive intervention has additive or synergistic efficacy and may reduce the level of systemic immunosuppression or quantity of donor tissue required.     

Has Time Come for New Goals in Human Islet Transplantation?

The enthusiasm regarding clinical islet transplantation has been dampened by the long-term results. Concerns about the associated risks of life-long immunosuppression and the striking imbalance between potential recipients and available donor pancreata warrant changes in some of the current goals.
Islet transplantation will never be a cure of type 1 diabetes in the majority of patients with no secondary complications, but is a valid option for a limited number of patients with brittle diabetes waiting for an organ or after organ transplantation. Furthermore, insulin independence should not be the main goal of islet transplantation, but avoidance of severe hypoglycemia and good glycemic control, which can be achieved with a relatively small functional beta-cell mass. Therefore, initially one islet infusion is sufficient. Retransplantation at a later time point remains an option, if glucose control deteriorates.
Efforts to improve islet transplantation should no longer focus on islet isolation and immunosuppression, but rather on the low posttransplant survival rate of islets caused by activation of the coagulation pathway and the limited oxygen delivery to the islets. Transplantation of smaller islets be it naturally small or size tailored reaggregated islets has the potential to facilitate these processes.     

Sirolimus-associated interstitial pneumonitis in solid organ transplant recipients

Sirolimus is a potent immunosuppressive agent used with increasing frequency in solid organ transplantation (SOT). However, it has been associated with rare but devastating pulmonary toxicity. We describe a case of pulmonary toxicity associated with the use of sirolimus in a 64-yr-old heart transplant recipient. We also review all reported cases of sirolimus-associated lung toxicity among SOT recipients in an effort to better understand the pathophysiology, risk factors, and outcomes of this rare but serious complication. A total of 64 cases have been reported since January 2000 including the present case. These consisted of 52 kidney, four lung, three liver, three heart, one heart-lung and one islet cell transplants. In most cases, patients presented with a constellation of symptoms consisting of fever, dyspnea, fatigue, cough, and occasionally hemoptysis. Although the risk factors for this association have not been clearly established, high dose, late exposure to the drug and male gender have been noticed among most. In almost all of the reported cases, sirolimus was added later in the course of immunosuppressive therapy, usually in an effort to attenuate the nephrotoxic effects of a previous regimen containing a calcineurin inhibitor. There were three deaths (4.8%) among 62 patients with known status at follow up; all deaths were among heart transplant recipients. Most patients (95%) resolved their clinical and radiographic findings with discontinuation or dose-reduction of the drug. Sirolimus-induced pulmonary toxicity is a rare but serious entity that should be considered in the differential diagnosis of a transplant recipient presenting with respiratory compromise. Dose-reduction or discontinuation of the drug can be life saving.     

Sirolimus and everolimus: inhibitors of mammalian target of rapamycin in liver transplantation

Sirolimus (SRL) and everolimus are members of a relatively new class of immunosuppressants that impair cell cycle proliferation by inhibition of the mammalian target of rapamycin. These agents have been evaluated and licensed for use in kidney transplantation where they are used predominantly as maintenance immunosuppression because they lack the nephrotoxicity associated with calcineurin inhibitors. Neither SRL nor its newer analogue everolimus are currently licensed for use in liver transplantation, but both have been used with varying degrees of success and efficacy in this setting. Concern has been expressed about a potential association between de novo use of SRL and both a high incidence of hepatic artery thrombosis after liver transplantation and impaired wound healing, and thus, subsequent development has focused on the use of SRL in response to calcineurin inhibitor toxicity in patients with established liver transplants as well as using its potential antitumor effects in patients transplanted for malignancy. This article reviews the reported experience of mammalian target of rapamycin inhibitor therapy in liver transplantation.     

Long-term control of diabetes in a nonhuman primate by two separate transplantations of porcine adult islets under immunosuppression

Porcine islet transplantation is an alternative to allo-islet transplantation. Retransplantation of islets is a routine clinical practice in islet allotransplantation in immunosuppressed recipients and will most likely be required in islet xenotransplantation in immunosuppressed recipients. We examined whether a second infusion of porcine islets could restore normoglycemia and further evaluated the efficacy of a clinically available immunosuppression regimen including anti-thymocyte globulin for induction; belimumab, sirolimus, and tofacitinib for maintenance and adalimumab, anakinra, IVIg, and tocilizumab for inflammation control in a pig to nonhuman primate transplantation setting. Of note, all nonhuman primates were normoglycemic after the retransplantation of porcine islets without induction therapy. Graft survival was >100 days for all 3 recipients, and 1 of the 3 monkeys showed insulin independence for >237 days. Serious lymphodepletion was not observed, and rhesus cytomegalovirus reactivation was controlled without any serious adverse effects throughout the observation period in all recipients. These results support the clinical applicability of additional infusions of porcine islets. The maintenance immunosuppression regimen we used could protect the reinfused islets from acute rejection.     

Infections following orthotopic liver transplantation.

The epidemiology of infections associated with orthotopic liver transplantation is summarized herein, and approaches to prophylaxis are outlined. Infection is a major complication following orthotopic liver transplantation, and more than half of transplant recipients develop at least one infection. The risk of infection is highest in the first month after transplantation, and the most common pathogens are bacteria and cytomegalovirus (CMV). Bacterial infections usually occur in the first month, arise in the abdomen, and are caused by aerobes. The peak incidence of CMV infection is late in the first month and early in the second month after transplantation. CMV syndromes include fever and neutropenia, hepatitis, pneumonitis, gut ulceration, and disseminated infection. Other significant problems are Candida intraabdominal infection, Herpes simplex mucocutaneous infection or hepatitis, adenovirus hepatitis, and Pneumocystis carinii pneumonia. Prophylaxis of infection in liver transplant recipients has not been well-studied. Several different regimens of parenteral, oral absorbable, and/or oral non-absorbable antibiotics active against bacteria and yeast have been used at various centers, but no randomized controlled trials have been conducted. Selective bowel decontamination appears to be a promising approach to the prevention of bacterial and Candida infections, while oral acyclovir may be a relatively convenient and effective agent for CMV prophylaxis.     

Bleeding complications precipitated by unrecognized Gingko biloba use after liver transplantation

Because of its neurocognitive enhancing effects, Gingko biloba has emerged as amongst the most commonly used herbal products. We report a liver transplant recipient with potentially life-threatening toxicity resulting from Gingko biloba use. Seven days after a second liver transplantation for recurrent hepatitisB virus infection, subphrenic hematoma was documented in a 59-year-old Korean patient. Failure to control bleeding with CT-guided drainage necessitated exploratory laparotomy for the evacuation of a large subphrenic hematoma. Three weeks later, an episode of vitreous hemorrhage was documented. Unbeknownst to his care providers, the patient had been consuming Gingko biloba throughout the postoperative period. No further bleeding episodes occurred after the cessation of Gingko biloba use. Unrecognized use of herbal products may be associated with serious side effects and adverse clinical sequelae in transplant recipients. Given their increasing popularity, the use of herbal products should be routinely sought as part of the history in transplant recipients.     

Sirolimus allows renal recovery in lung and heart transplant recipients with chronic renal impairment.

BACKGROUND: Until recently, there has been no practical alternative to the use of calcineurin inhibitors (CIs) as primary immunosuppressants in lung transplantation (LTx) and heart transplantation (HTx). Sirolimus (SRL) is a novel powerful immunosuppressant without renal toxicity, a common post-transplant problem associated with CI therapy. METHODS: SRL was used in 20 LTx and 5 HTx recipients >90 days post-transplant, where serious renal impairment was limiting CI dosing. Patients started on 2 to 5 mg/day orally at a median of 1,185 days post-transplant. Dosage adjustments were made according to trough levels, toxicity and perceived efficacy. With SRL initiation, 48% ceased CI therapy and the remainder decreased their dose substantively. RESULTS: After 30 days, 4 of 5 dialyzed patients ceased dialysis and 15 of 20 patients with an elevated serum creatinine (Cr) (mean Cr 0.29 mmol/liter) improved their Cr. The direction of change in Cr at 30 days predicted longer term Cr. The starting Cr did not predict the 30-day or long-term value. There were two bouts of acute and one bout of chronic rejection. There were 35 infectious complications in 16 patients and 24 episodes of potential SRL-related toxicity in 17 patients. These events generally responded to dose reduction or temporary cessation and were level-related. Fifteen recipients presently remain on the drug. None of the 7 deaths could be directly related to toxicity. CONCLUSION: SRL is a useful alternative immunosuppressant, allowing significant CI withdrawal in transplant recipients with renal impairment. Whether the resulting improvement in Cr can be maintained in the long term probably depends on the balance between the extent of acute and chronic renal damage.