Sirolimus Improves Renal Function in Cardiac Transplantation

Honoring 50 Years of Clinical Heart Transplantation in Circulation

Heart transplantation has become a standard therapy option for advanced heart failure. The translation of heart transplantation from innovative experiments to long-term clinical success has married prescient insights with discipline and organization in the domains of surgical techniques, organ preservation, immunosuppression, organ donation and transplantation logistics, infection control, and long-term graft surveillance. This review explores the key milestones of the past 50 years of heart transplantation and discusses current challenges and promising innovations on the clinical horizon.

The Past, Present and Future of Heart Transplantation

Heart transplantation (HTx) has become standard treatment for selected patients with end-stage heart failure. Improvements in immunosuppressant, donor procurement, surgical techniques, and post-HTx care have resulted in a substantial decrease in acute allograft rejection, which had previously significantly limited survival of HTx recipients. However, limitations to long-term allograft survival exist, including rejection, infection, coronary allograft vasculopathy, and malignancy. Careful balance of immunosuppressive therapy and vigilant surveillance for complications can further improve long-term outcomes of HTx recipients.

Chronic renal insufficiency in heart transplant recipients: risk factors and management options

Renal dysfunction after heart transplantation is a frequently observed complication, in some cases resulting in significant limitation of quality of life and reduced survival. Since the pathophysiology of renal failure (RF) is multifactorial, the current etiologic paradigm for chronic kidney disease after heart transplantation relies on the concept of calcineurin inhibitor (CNI)-related nephrotoxicity acting on a predisposed recipient. Until recently, the management of RF has been restricted to the minimization of CNI dosage and general avoidance of classic nephrotoxic risk factors, with somewhat limited success. The recent introduction of proliferation signal inhibitors (PSIs) (sirolimus and everolimus), a new class of immunosuppressive drugs lacking intrinsic nephrotoxicity, has provided a completely new alternative in this clinical setting. As clinical experience with these new drugs increases, new renal-sparing strategies are becoming available. PSIs can be used in combination with reduced doses of CNIs and even in complete CNI-free protocols. Different strategies have been devised, including de novo use to avoid acute renal toxicity in high-risk patients immediately after transplantation, or more delayed introduction in those patients developing chronic RF after prolonged CNI exposure. In this review, the main information on the clinical relevance and pathophysiology of RF after heart transplantation, as well as the currently available experience with renal-sparing immunosuppressive regimens, particularly focused on the use of PSIs, is reviewed and summarized, including the key practical points for their appropriate clinical usage.

Mycophenolate monitoring in liver, thoracic, pancreas, and small bowel transplantation: a consensus report

Assessing the value of mycophenolic acid (MPA) monitoring outside renal transplantation is hindered by the absence of any trial comparing fixed-dose and concentration-controlled therapy. However, in liver and thoracic transplantation particularly, clinical trials, observational studies with comparison groups, and case series have described MPA efficacy, exposure/efficacy relationships, pharmacokinetic variability, and clinical outcomes relating to plasma MPA concentrations. On the basis of this evidence, this report identifies MPA as an immunosuppressant for which the combination of variable disposition, efficacy, and adverse effects contributes to interindividual differences seemingly in excess of those optimal for a fixed-dosage mycophenolate regimen. Combined with experiences of MPA monitoring in other transplant indications, the data have been rationalized to define circumstances in which measurement of MPA concentrations can contribute to improved management of mycophenolate therapy in nonrenal transplant recipients.

Clinical recommendations for the use of everolimus in heart transplantation

Proliferation signal inhibitors (PSIs), everolimus (EVL), and sirolimus are a group of immunosuppressor agents indicated for the prevention of acute rejection in adult heart transplant recipients. Proliferation signal inhibitors have a mechanism of action with both immunosuppressive and antiproliferative effects, representing an especially interesting treatment option for the prevention and management of some specific conditions in heart transplant population, such as graft vasculopathy or malignancies. Proliferation signal inhibitors have been observed to work synergistically with calcineurin inhibitors (CNIs). Data from clinical trials and from the growing clinical experience show that when administered concomitantly with CNIs, PSIs allow significant dose reductions of the latter without loss of efficacy, a fact that has been associated with stabilization or significant improvement in renal function in patients with CNI-induced nephrotoxicity. The purpose of this article was to review the current knowledge of the role of PSIs in heart transplantation to provide recommendations for the proper use of EVL in cardiac transplant recipients, including indications, treatment regimens, monitoring, and management of the adverse events.

Usefulness of sirolimus as rescue therapy in heart transplant recipients with renal failure: analysis of the Spanish Multicenter Observational Study (RAPACOR)

BACKGROUND

Chronic renal failure is a common complication of heart transplantation. Sirolimus (SRL) is an immunosuppressive drug that, unlike calcineurin inhibitors (CNIs), is not associated with nephrotoxicity.

METHODS

We collected efficacy and safety data from a Spanish registry of heart transplant recipients who were switched from a CNI to SRL due to renal failure. Patients were included if the serum creatinine level before switching was >1.5 mg/dL and/or the estimated creatinine clearance level was below 50 mL/min.

RESULTS

Ninety-seven patients started SRL due to renal impairment. When SRL was started, CNIs were progressively tapered and in some cases withdrawn. Mean baseline creatinine level was 2.5 mg/dL and mean creatinine clearance level was 39 mL/min. Only 1 episode of acute rejection was observed in a patient receiving SRL plus cyclosporine (CsA) but the eventual allograft function remained stable. Compared with baseline, a significant improvement in renal function was observed at 6 months among patients who stopped CNIs before the third month after SRL was started, although not among those who continued taking CNIs. Upon multivariate analysis, no predictors of response were observed. SRL was withdrawn in 18% of patients due to adverse events.

CONCLUSIONS

Switching to SRL was safe in heart allograft recipients, improving renal function among those previously receiving a CNI. Renal function improves if CNIs are withdrawn soon after starting SRL.

Long-term immunosuppression with anti-CD25 monoclonal antibodies in heart transplant patients with chronic kidney disease

BACKGROUND

Chronic kidney disease (CKD), a frequent and serious complication after heart transplantation, is associated with increased mortality. Current strategies include dose reduction or conversion from calcineurin inhibitors (CNIs) to either mycophenolate mofetil and/or rapamycin, with variable results and side-effect profiles.

METHODS

We evaluated the effectiveness of long-term anti-CD25 monoclonal antibody (MAb)-based immunosuppression in 17 adult heart transplant recipients with CKD at 10 +/- 5 years post-transplant. Seven patients had previously been switched to rapamycin but had untreatable side-effects and 10 patients were still on a CNI. The latter were matched with 10 control heart transplant patients whose renal function had remained stable over a similar post-transplant follow-up period, on CNI.

RESULTS

Anti-CD25 MAb were given over 13 +/- 10 months and were well tolerated with CD25 saturation monitoring (target <2% expression). Side-effects secondary to rapamycin resolved in 6 patients. The slope change of the creatinine clearance improved in patients in whom CNIs were discontinued (+0.335 ml/min/month vs -0.124 ml/min/month in controls, p = 0.03). Four patients died. Three died after 2, 6 and 7 months of follow-up, respectively, with the following diagnoses: acute renal failure (the patient refused dialysis); acute rejection (the patient had refused protocol endomyocardial biopsy); and perforated diverticulitis. The fourth patient died of pneumonia, 3 months after conversion from anti-CD25 MAb to rapamycin, because of poor venous access.

CONCLUSIONS

The use of long-term anti-CD25 MAb therapy as a potential replacement for CNI- and rapamycin-based immunosuppression is feasible. It is crucial that rejection surveillance be intensified. A randomized, controlled trial is required to confirm the benefits and safety of this strategy.

The first year post-heart transplantation: use of immunosuppressive drugs and early complications

A large number of heart transplants are performed annually in different transplant centers in the United States. This is partly because of the improved survival of patients who undergo cardiac transplantation, thus making it a more viable option in the management of end-stage heart failure. The survival benefit after heart transplantation is a result of newer immunosuppressive drug regimens and a better understanding of their effects and interactions. Several studies, mostly involving a small number of patients, describe use and comparison of the many distinct immunosuppressive drugs available to date. Interestingly, many transplant centers perform in-house typical induction treatment regimens because of their own experience and intra-institutional preference. This review summarizes current practices of immunosuppressive drug therapy in the first year post-heart transplant based on the available clinical evidence and discusses future options of heart transplant immunosuppressive drug therapies.

Proliferation signal inhibitors in cardiac transplantation

PURPOSE OF REVIEW

Standard immunosuppression after cardiac transplantation includes a calcineurin inhibitor in combination with mycophenolate mofetil or azathioprine and corticosteroids. These agents have led to excellent outcomes but have shortcomings in terms of efficacy and toxicity. A new class of immunosuppressants, proliferation signal inhibitors, may meet some of these shortcomings.

RECENT FINDINGS

The efficacy of the available proliferation signal inhibitors - sirolimus and its derivative everolimus - has been compared with azathioprine in three randomized clinical trials. Sirolimus or everolimus use was associated with lower rates of acute rejection and reduced development of chronic allograft vasculopathy. Sirolimus was not found to be superior to mycophenolate mofetil in a randomized trial. Proliferation signal inhibitors have been reported to be effective in refractory recurrent acute rejection. Nonrandomized studies have demonstrated that proliferation signal inhibitor-based immunosuppression enables recovery from renal dysfunction secondary to calcineurin inhibitor treatment. Proliferation signal inhibitor-based treatment is associated with a lower risk of malignancy than calcineurin inhibitor-based regimens. Proliferation signal inhibitors have significant adverse effects that may limit widespread use.

SUMMARY

Proliferation signal inhibitors are important new immunosuppressive agents that have added considerably to the armamentarium allowing further tailored immunosuppression to individualize patient care after heart transplantation.

Sirolimus in de novo heart transplant recipients with severe renal impairment

Two patients with end-stage heart failure and advanced renal dysfunction (under chronic dialysis therapy) underwent heart transplantation. In order to avoid further renal impairment, a calcineurine inhibitor-free immunosuppression regimen based on the sirolimus was used. Although temporary perioperative support with hemofiltration and dialysis was needed, both patients eventually regained a reasonable renal function with no episodes of clinical rejection and normal cardiac function at 13 and 11 months, respectively, after transplantation. Sirolimus-based immunosuppression might be an interesting alternative to calcineurine inhibitors in the management of patients with significant renal impairment.