Tacrolimus as a rescue immunosuppressant after heart transplantation

The impact of tacrolimus as rescue therapy in children using a double immunosuppressive regimen after heart transplantation

BACKGROUND

Organ transplant recipients with refractory rejection or intolerance to the prescribed immunosuppressant may respond to rescue therapy with tacrolimus. We sought to evaluate the clinical outcomes of children undergoing heart transplantation who required conversion from a cyclosporine-based, steroid-free therapy to a tacrolimus-based regimen.

METHODS

We performed a prospective, observational, cohort study of 28 children who underwent conversion from cyclosporine-based, steroid-free therapy to a tacrolimus-based therapy for refractory or late rejection or intolerance to cyclosporine.

RESULTS

There was complete resolution of refractory rejection episodes and adverse side effects in all patients. The incidence rate (×100) of rejection episodes before and after conversion was 7.98 and 2.11, respectively (P ≤ .0001). There was a 25% mortality rate in patients using tacrolimus after a mean period of 60 months after conversion.

CONCLUSION

Tacrolimus is effective as rescue therapy for refractory rejection and is a therapeutic option for pediatric patients.

Tacrolimus with mycophenolate mofetil (MMF) or sirolimus vs. cyclosporine with MMF in cardiac transplant patients: 1-year report

The most advantageous combination of immunosuppressive agents for cardiac transplant recipients has not yet been established. Between November 2001 and June 2003, 343 de novo cardiac transplant recipients were randomized to receive steroids and either tacrolimus (TAC) + sirolimus (SRL), TAC + mycophenolate mofetil (MMF) or cyclosporine (CYA) + MMF. Antilymphocyte induction therapy was allowed for up to 5 days. The primary endpoint of >/=3A rejection or hemodynamic compromise rejection requiring treatment showed no significant difference at 6 months (TAC/MMF 22.4%, TAC/SRL 24.3%, CYA/MMF 31.6%, p = 0.271) and 1 year (p = 0.056), but it was significantly lower in the TAC/MMF group when compared only to the CYA/MMF group at 1 year (23.4% vs. 36.8%; p = 0.029). Differences in the incidence of any treated rejection were significant (TAC/SRL = 35%, TAC/MMF = 42%, CYA/MMF = 59%; p < 0.001), as were median levels of serum creatinine (TAC/SRL = 1.5 mg/dL, TAC/MMF = 1.3 mg/dL, CYA/MMF = 1.5 mg/dL; p = 0.032) and triglycerides (TAC/SRL = 162 mg/dL, TAC/MMF = 126 mg/dL, CYA/MMF = 154 mg/dL; p = 0.028). The TAC/SRL group encountered fewer viral infections but more fungal infections and impaired wound healing. These secondary endpoints suggest that the TAC/MMF combination appears to offer more advantages than TAC/SRL or CYA/MMF in cardiac transplant patients, including fewer >/=3A rejections or hemodynamic compromise rejections and an improved side-effect profile.

Antiinflammatory effects of Tacrolimus in a mouse model of pleurisy

INTRODUCTION

Tacrolimus is an antibiotic macrolide with immunosuppressant properties isolated from Streptomyces tsukubaensis.

OBJECTIVES

This study evaluated whether the acute and systemic administration of Tacrolimus significantly interfered in leukocyte migration, exudation, myeloperoxidase and adenosine-deaminase and nitric oxide levels, as well as Interleukin-1 (IL-1beta) and tumor necrosis factor alpha (TNFalpha) levels in a mouse model of pleurisy in comparison to those obtained with dexamethasone.

MATERIALS AND METHODS

Pleurisy was induced by carrageenan (Cg, 1%), bradykinin (BK, 10 nmol), histamine (HIS, 1 micromol) or substance P (PS, 20 nmol) administered by intrapleural route (ipl.) and the inflammatory parameters (cell migration and exudation) were analyzed 4 h after. In the model of pleurisy induced by carrageenan, other markers in the pleural fluid, such as cytokines (TNFalpha and Il-1beta), nitrite/nitrate (NOx), myeloperoxidase (MPO) and adenosine-deaminase (ADA) levels, were also studied. Dexamethaseone (0.5 mg/kg, i.p., 0.5 h before) was also analyzed in all protocols.

RESULTS

In the pleurisy induced by carrageenan, Tacrolimus (1 mg/kg, i.p.) and dexamethasone (0.5 mg/kg, i.p.) administered 0.5 h before caused a significant decrease in leukocytes, neutrophils and exudation (P < 0.01). Under the same conditions, Tacrolimus and dexamethasone did not modify the blood's white or red cells (P > 0.05). Tacrolimus showed a long lasting antiinflammatory effect, inhibiting leukocytes and neutrophils for up to 24 h (P < 0.01), whereas the inhibition of exudation was less marked (up to 2 h) (P < 0.01). These drugs caused a marked reduction in MPO activity, as well as IL-1beta and TNFalpha levels (P < 0.01), but only Tacrolimus inhibited ADA activity (P < 0.01). On the other hand, dexamethasone, but not Tacrolimus, inhibited NOx levels (P < 0.01). In the same conditions, Tacrolimus significantly inhibited cell migration induced by either bradykinin, histamine or substance P (P < 0.05). In a similar manner, dexamethasone inhibited leukocyte influx induced by bradykinin and histamine (P < 0.05). Regarding exudation effects, dexamethasone markedly inhibited this parameter induced by BK, HIS or SP, whereas Tacrolimus only inhibited exudation caused by HIS (P < 0.05).

CONCLUSIONS

The results of the present work indicate that Tacrolimus showed important antiinflammatory properties against pleurisy in mice that are different from those caused by dexamethasone. The inhibition of proinflammatory cytokine (TNFalpha, IL-1beta), enzyme (myeloperoxidase, adenosine-deaminase) and mediator (bradykinin, histamine, substance P) release and/or action appears to account for Tacrolimus's actions.

Reversal of tacrolimus-related hypertrophic obstructive cardiomyopathy 5 years after kidney transplant in a 6-year-old recipient

Hypertrophic obstructive cardiomyopathy (HOCM) is an unusual but serious side-effect of tacrolimus (TAC) based immunosuppression primarily affecting pediatric patients after solid organ transplant. TAC-induced HOCM has already been described in patients after liver, bowel and heart transplant shortly after the procedure. Herein, we present the first case report of TAC-induced HOCM in a young renal transplant recipient 5 yr after renal transplant. The condition was diagnosed by ECHO and EKG and successfully treated by discontinuation of TAC followed by conversion to cyclosporine (CsA).

Clinical pharmacokinetics and pharmacodynamics of tacrolimus in solid organ transplantation

The aim of this review is to analyse critically the recent literature on the clinical pharmacokinetics and pharmacodynamics of tacrolimus in solid organ transplant recipients. Dosage and target concentration recommendations for tacrolimus vary from centre to centre, and large pharmacokinetic variability makes it difficult to predict what concentration will be achieved with a particular dose or dosage change. Therapeutic ranges have not been based on statistical approaches. The majority of pharmacokinetic studies have involved intense blood sampling in small homogeneous groups in the immediate post-transplant period. Most have used nonspecific immunoassays and provide little information on pharmacokinetic variability. Demographic investigations seeking correlations between pharmacokinetic parameters and patient factors have generally looked at one covariate at a time and have involved small patient numbers. Factors reported to influence the pharmacokinetics of tacrolimus include the patient group studied, hepatic dysfunction, hepatitis C status, time after transplantation, patient age, donor liver characteristics, recipient race, haematocrit and albumin concentrations, diurnal rhythm, food administration, corticosteroid dosage, diarrhoea and cytochrome P450 (CYP) isoenzyme and P-glycoprotein expression. Population analyses are adding to our understanding of the pharmacokinetics of tacrolimus, but such investigations are still in their infancy. A significant proportion of model variability remains unexplained. Population modelling and Bayesian forecasting may be improved if CYP isoenzymes and/or P-glycoprotein expression could be considered as covariates. Reports have been conflicting as to whether low tacrolimus trough concentrations are related to rejection. Several studies have demonstrated a correlation between high trough concentrations and toxicity, particularly nephrotoxicity. The best predictor of pharmacological effect may be drug concentrations in the transplanted organ itself. Researchers have started to question current reliance on trough measurement during therapeutic drug monitoring, with instances of toxicity and rejection occurring when trough concentrations are within 'acceptable' ranges. The correlation between blood concentration and drug exposure can be improved by use of non-trough timepoints. However, controversy exists as to whether this will provide any great benefit, given the added complexity in monitoring. Investigators are now attempting to quantify the pharmacological effects of tacrolimus on immune cells through assays that measure in vivo calcineurin inhibition and markers of immunosuppression such as cytokine concentration. To date, no studies have correlated pharmacodynamic marker assay results with immunosuppressive efficacy, as determined by allograft outcome, or investigated the relationship between calcineurin inhibition and drug adverse effects. Little is known about the magnitude of the pharmacodynamic variability of tacrolimus.

An update on clinical outcomes in heart and lung transplantation

Much progress has been made in heart and lung transplantation over recent decades. The immune mechanisms that result in allograft rejection are now better understood, and the development of immunosuppressant therapies has decreased recipient mortality among transplant recipients. During the 1980s, immunosuppressant therapy primarily involved the use of corticosteroids and cyclosporine. However, while survival rates increased among transplant recipients, many patients experienced primary graft failures, acute and chronic rejection, as well as death. Until the introduction of tacrolimus in the early 1990s, all patients received the same immunosuppressant regimen, regardless of its effectiveness. Tacrolimus therapy has contributed much to the success rates of both heart and lung transplantation, and by 2001, it had become the preeminent immunosuppressant agent used in lung transplantation.

Drug immunosuppression therapy for adult heart transplantation. Part 2: clinical applications and results

This review describes the clinical application of classical immunosuppressive drugs as well as that of more recent drugs. All current immunosuppressive drugs target T-cell activation, and cytokine production and clonal expansion, or both. Immunosuppressive protocols can be broadly divided into induction therapy, maintenance immunosuppression, and treatment of acute rejection episodes.

Inhibitors of Calcineurin

Before the early 1980s, patient and allograft survival for solid organ transplant recipients was dismal. By 1983, the first calcineurin blocker, cyclosporine (Sandimmun), had been introduced, and outcomes were dramatically improved. However, cyclosporine macroemulsion had suboptimal pharmacokinetics, significant drug interactions, and several adverse effects, including nephrotoxicity, neurotoxicity, hyperlipidemia, and hypertension. Recent advances with cyclosporine include the introduction of modified dosage formulations: Neoral, a microemulsion, and several generic microemulsion products. The potent second-generation calcineurin blocker tacrolimus (Prograf) was introduced in 1994 and has become the drug of choice for several types of transplant recipients. Although tacrolimus has improved pharmacokinetics and therapeutic drugmonitoring parameters, it has adverse effects such as nephrotoxicity, neurotoxicity, and diabetes. Thus, current immunosuppressive regimens implementing calcineurin blockers often involve additional immunosuppressive agents to “spare” the use of these agents, minimizing their adverse effects. This article reviews the mechanisms of action, pharmacokinetics, clinical use, therapeutic drug monitoring, drug interactions, adverse effects, and dosing of cyclosporine and tacrolimus in solid organ transplant recipients.

Tacrolimus: a further update of its use in the management of organ transplantation

Extensive clinical use has confirmed that tacrolimus (Prograf) is a key option for immunosuppression after transplantation. In large, prospective, randomised, multicentre trials in adults and children receiving solid organ transplants, tacrolimus was at least as effective or provided better efficacy than cyclosporin microemulsion in terms of patient and graft survival, treatment failure rates and the incidence of biopsy-proven acute and corticosteroid-resistant rejection episodes. Notably, the lower incidence of rejection episodes after renal transplantation in tacrolimus recipients was reflected in improved cost effectiveness. In bone marrow transplant (BMT) recipients, the incidence of tacrolimus grade II-IV graft-versus-host disease was significantly lower with tacrolimus than cyclosporin treatment. Efficacy was maintained in renal and liver transplant recipients after total withdrawal of corticosteroid therapy from tacrolimus-based immunosuppression, with the incidence of acute rejection episodes at up to 2 years' follow-up being similar with or without corticosteroids. Tacrolimus provided effective rescue therapy in transplant recipients with persistent acute or chronic allograft rejection or drug-related toxicity associated with cyclosporin treatment. Typically, conversion to tacrolimus reversed rejection episodes and/or improved the tolerability profile, particularly in terms of reduced hyperlipidaemia. In lung transplant recipients with obliterative bronchiolitis, conversion to tacrolimus reduced the decline in and/or improved lung function in terms of forced expiratory volume in 1 second. Tolerability issues may be a factor when choosing a calcineurin inhibitor. Cyclosporin tends to be associated with a higher incidence of significant hypertension, hyperlipidaemia, hirsutism, gingivitis and gum hyperplasia, whereas the incidence of some types of neurotoxicity, disturbances in glucose metabolism, diarrhoea, pruritus and alopecia may be higher with tacrolimus treatment. Renal function, as assessed by serum creatinine levels and glomerular filtration rates, was better in tacrolimus than cyclosporin recipients at up to 5 years' follow-up.

CONCLUSION

Recent well designed trials have consolidated the place of tacrolimus as an important choice for primary immunosuppression in solid organ transplantation and in BMT. Notably, in adults and children receiving transplants, tacrolimus-based primary immunosuppression was at least as effective or provided better efficacy than cyclosporin microemulsion treatment in terms of patient and graft survival, treatment failure and the incidence of acute and corticosteroid-resistant rejection episodes. The reduced incidence of rejection episodes in renal transplant recipients receiving tacrolimus translated into a better cost effectiveness relative to cyclosporin microemulsion treatment. The optimal immunosuppression regimen is ultimately dependent on balancing such factors as the efficacy of the individual drugs, their tolerability, potential for drug interactions and pharmacoeconomic issues.

Tacrolimus in heart transplantation

Tacrolimus (Tac), which blocks T- and B-cell proliferation by inhibiting calcineurin, was first used for immunosuppression following heart transplant (HT) in 1989. Two multicenter randomized trials have compared Tac to the oil-based cyclosporine (CsA) formulation (both combined with azathioprine and steroids) in HT patients. The two drugs displayed similar patient survival rates and incidences of rejection, nephrotoxicity, diabetes, and infections. The Tac group however, showed a lower incidence of arterial hypertension (and, in one study, of dyslipidemia). A pilot study of Tac in combination with mycophenolate mofetil (MMF) and steroids suggested that maintenance of serum mycophenolic acid levels at 2.5 to 4.5 microg/mL yields lower rejection rates without greater toxicity than previous regimens. Currently, a European multicenter randomized trial is comparing Tac with Neoral CsA, both used in combination with MMF, steroids, and induction antibodies. For patients undergoing primary immunosuppression with CsA, Tac has proved effective for rescue from steroid-resistant acute rejection. It also has tentatively been used without other drugs in selected patients. It is a valid alternative to CsA in current immunosuppressive regimens, because it does not cause gingival hyperplasia or hirsutism and, thus, may improve the quality of life and treatment compliance of female and pediatric patients. It may be preferable to CsA for patients with arterial hypertension or intractable dyslipidemia. Current and future studies will clarify the efficacy and safety of regimens combining Tac with MMF or rapamycin.

Failure of cyclosporin a to rescue peripheral nerve allografts in acute rejection

Prevention and control of graft rejection remain essential in the investigation of peripheral nerve allotransplantation. Although use of cyclosporin A (CsA) has been shown to suppress successfully the rejection of nerve allografts, limited information exists concerning use of this drug to arrest rejection in progress, and thereby effect salvage of these grafts. The aim of this study was to determine the efficacy of CsA in the treatment of ongoing acute rejection of peripheral nerve allografts. Buffalo rats received posterior tibial nerve grafts from either Lewis or Buffalo donor animals and were divided into five groups: group 1 received isografts and no CsA treatment (n = 8), group 2 received allografts with continuous CsA therapy (n = 10), group 3 received allografts with no treatment (n = 7), group 4 received allografts with initiation of CsA therapy delayed until 3 weeks after the procedure (n = 11), and group 5 received allografts with an interrupted course of CsA (n = 15). All grafts were harvested at 10 weeks. Histomorphometric analysis demonstrated comparable nerve regeneration in groups 1 and 2 and good regeneration in group 3 animals, despite cellular infiltrate suggestive of rejection. At 3 weeks after surgery, group 4 animals showed early rejection and significantly less neuroregeneration than positive controls at 10 weeks after delayed initiation of CsA therapy. Finally, group 5 animals showed early regeneration at 3 weeks but significantly lesser regeneration by 10 weeks after interruption of therapy. In this experimental protocol, CsA was ineffective in rescuing histologically proven rejection in progress.

Current practices: immunosuppression induction, maintenance, and rejection regimens in contemporary post-heart transplant patient treatment

Cardiac transplantation is the definitive treatment for eligible patients with end-stage cardiomyopathy. Survival rates have improved dramatically during the last 10 years, especially since the advent of cyclosporine-A. Cardiac allograft rejection, previously considered a major cause of early mortality after transplantation, is no longer the limiting factor for early survival, with the use of newer and more specific immunosuppression regimens. Very few randomized, prospective trials, including comparisons between immunosuppression regimens, have been conducted in this area. Therefore, practices vary with physician and institutional experience. Most centers use a multipronged approach to immunosuppression, targeting multiple sites in the immune cascade that lead to allograft rejection. Multiple new agents in development are reviewed. Drugs such as sirolimus and its derivative, everolimus, act on specific intracellular receptors within lymphocytes, whereas other medications such as Daclizumab (Roche Laboratories, Nutley, NJ) block the interleukin-2 receptor on the surface of activated T cells. The immune response to foreign antigens is complex, with multiple redundant levels. Immunosuppression regimens continue to seek a fine balance between overimmunosuppression and insufficient protection, which may lead to allograft rejection or loss.