Interleukin-2 Receptor Antagonists as Induction Therapy After Heart Transplantation: Systematic Review With Meta-Analysis of Randomized Trials

Induction therapy in heart transplantation: A systematic review and network meta-analysis for developing evidence-based recommendations

INTRODUCTION

Induction therapy (IT) utility in heart transplantation (HT) remains contested. Commissioned by a clinical-practice guidelines panel to evaluate the effectiveness and safety of IT in adult HT patients, we conducted this systematic review and network meta-analysis (NMA).

METHODS

We searched for studies from January 2000 to October 2022, reporting on the use of any IT agent in adult HT patients. Based on patient-important outcomes, we performed frequentist NMAs separately for RCTs and observational studies with adjusted analyses, and assessed the certainty of evidence using the GRADE framework.

RESULTS

From 5156 publications identified, we included 7 RCTs and 12 observational studies, and report on two contemporarily-used IT agents-basiliximab and rATG. The RCTs provide only very low certainty evidence and was uninformative of the effect of the two agents versus no IT or one another. With low certainty in the evidence from observational studies, basiliximab may increase 30-day (OR 1.13; 95% CI 1.06-1.20) and 1-year (OR 1.11; 95% CI 1.02-1.22) mortality compared to no IT. With low certainty from observational studies, rATG may decrease 5-year cardiac allograft vasculopathy (OR .82; 95% CI .74-.90) compared to no IT, as well as 30-day (OR .85; 95% CI .80-.92), 1-year (OR .87; 95% CI .79-.96), and overall (HR .84; 95% CI .76-.93) mortality compared to basiliximab.

CONCLUSION

With low and very low certainty in the synthetized evidence, these NMAs suggest possible superiority of rATG compared to basiliximab, but do not provide compelling evidence for the routine use of these agents in HT recipients.

Induction Therapy and Therapeutic Antibodies

Prevention of allograft rejection is one of the crucial goals in solid organ transplantation to ensure durability of the graft and is chiefly mediated by cellular and humoral pathways targeting cell surface alloantigens. The risk of rejection is highest in the first post-transplant year and wanes with time albeit the risk always exists and varies with the type of organ transplanted. Induction therapies refer to the use of high-intensity immunosuppression in the immediate post-operative period to mitigate the highest risk of rejection. This term encompasses chiefly the use of antibody therapies directed against one of the key pathways in T-cell activation or abrogating effects of circulating alloantibodies. These antibodies carry more potent immunomodulatory effect than maintenance immunosuppressive therapy alone and many of them lead to durable immune cell depletion. A variety of monoclonal and polyclonal antibodies have been utilized for use not only for induction therapy, but also for treatment of allograft rejection when it occurs and as components of desensitization therapy before and after transplantation to modulate circulating alloantibodies.

Influence of Induction Therapy Using Basiliximab With Delayed Tacrolimus Administration in Heart Transplant Recipients - Comparison With Standard Tacrolimus-Based Triple Immunosuppression

BACKGROUND

Appropriate indications and protocols for induction therapy using basiliximab have not been fully established in heart transplant (HTx) recipients. This study elucidated the influence of induction therapy using basiliximab along with delayed tacrolimus (Tac) initiation on the outcomes of high-risk HTx recipients.Methods and Results:A total of 86 HTx recipients treated with Tac-based immunosuppression were retrospectively reviewed. Induction therapy was administered to 46 recipients (53.5%) with impaired renal function, pre-transplant sensitization, and recipient- and donor-related risk factors (Induction group). Tac administration was delayed in the Induction group. Induction group subjects showed a lower cumulative incidence of acute cellular rejection grade ≥1R after propensity score adjustment, but this was not significantly different (hazard ratio [HR]: 0.63, 95% confidence interval [CI]: 0.37-1.08, P=0.093). Renal dysfunction in the Induction group significantly improved 6 months post-transplantation (P=0.029). The cumulative incidence of bacterial or fungal infections was significantly higher in the Induction group (HR: 10.6, 95% CI: 1.28-88.2, P=0.029).

CONCLUSIONS

These results suggest that basiliximab-based induction therapy with delayed Tac initiation may suppress mild acute cellular rejection and improve renal function in recipients with renal dysfunction, resulting in its non-inferior outcome, even in high-risk patients, when applied to the appropriate recipients. However, it should be carefully considered in recipients at a high risk of bacterial and fungal infections.

Impact of Induction Immunosuppression on Post-Transplant Outcomes of Patients Bridged with Contemporary Left Ventricular Assist Devices

For patients bridged to transplant (BTT) with left ventricular assist devices (LVAD), data regarding the use of induction immunosuppressive therapy remain limited. The objectives of the current study were to describe the current trends and clinical consequences of IT in patients BTT with LVAD. The United Network of Organ Sharing database was queried to identify adult, single-organ heart transplant recipients who were BTT with LVAD between 2008 and 2018. Propensity score matching was then used to balance clinical covariates between those patient who did and did not receive IT. The primary outcomes of interest were graft survival, hospitalization for rejection and infection, and freedom from transplant coronary artery disease (TCAD). In the overall cohort, 49.1% (n = 3,978) received IT, with basiliximab being the most commonly used agent followed by antithymocyte globulin. After propensity score matching, 4,388 patients (2,194 without induction and 2,194 with induction) were identified. Between those who did and did not receive IT, there was no significant difference in graft survival, freedom from hospitalization for rejection, and freedom from hospitalization for infection. Patients who received IT experienced increased freedom from TCAD (p = 0.004) with unadjusted hazard ratio of 0.81 (95% Cardiac Index: 0.70-0.93). For freedom from TCAD, antithymocyte globulin was associated with better outcomes than basiliximab (80.2% vs. 73.1% at 5 years, log rank p value = 0.004). In a sensitivity analysis, there was no significant increase in hospitalization for infection in those patients with an infected LVAD before transplant. Use of induction therapy in patients BTT with LVAD appears to be safe and feasible, without a significant increase in the risk of infection or rejection, even in those patients with pretransplant device-related infections. IT, particularly antithymocyte globulin, was associated with increased time to development of TCAD. Routine use of IT in patients BTT with LVAD may be considered, and further randomized control trials are warranted to further support these data.

Repeated daclizumab administration to delay the introduction of calcineurin inhibitors in heart transplant patients with postoperative renal dysfunction

Daclizumab is an interleukin-2 receptor antagonist which is used for induction therapy in heart transplant patients. It has few side effects and is associated with a low infection rate. Postoperative renal failure after heart transplantation is common and potentially fatal. The administration of calcineurin inhibitors in the postoperative period can aggravate the situation. We report the cases of six patients who underwent heart transplantation and developed acute renal failure in the immediate postoperative period. All were administered daclizumab weekly to avoid the introduction of calcineurin inhibitors and to facilitate recovery of renal function. Calcineurin inhibitors were introduced only once renal function had improved. Renal function recovered in all cases and there was a low complication rate. The administration of repeated doses of daclizumab to patients who experience acute postoperative renal failure after heart transplantation may provide an alternative therapeutic approach that enables calcineurin inhibitors to be avoided and, consequently, renal function to recover.

CD28 and KIR2D receptors as sensors of the immune status in heart and liver transplantation

Viral infections and cellular acute rejection (AR) condition immunosuppressive therapy and compromise the evolution of allografts. Immune monitoring can be useful for ascertaining rejection and for differentiating allo-reaction from activation induced by infections. This work analyzes the usefulness of monitoring the expression of CD28 and KIR2D receptors in peripheral blood T lymphocytes by flow cytometry, to ascertain the immune response in heart and liver transplant recipients. In both types of transplant, the up-regulation of CD28 in CD4(+) lymphocytes in the periods of greatest AR frequency indicates an effective allo-response, whereas the post-transplantation emergence of circulating CD8(+)CD28(-) and CD8(+)CD28(-)KIR2D(+) T cells correlates with better early clinical results. Cytomegalovirus (CMV) infection, but not hepatitis C virus (HCV) or other infections, abrogated both CD28 up-regulation and CD8(+)CD28(-)KIR2D(+) T-cell expansion. Our results show that monitoring the expression of CD28 and KIR2D receptors on T lymphocytes might be considered as sensors of the immune status of heart and liver recipients.

Induction treatment with monoclonal antibodies for heart transplantation

Individualization of induction therapy for heart transplantation (HT) is needed, given that only patients at significant risk for fatal rejection seem to present a favorable risk-benefit ratio. The question whether monoclonal interleukin 2 antagonists or antilymphocyte antibodies should be recommended remains unanswered. As most studies suggest that they have similar efficacy in preventing acute rejection, other variables related to safety or management costs should be taken into account. The cytokine release syndrome, associated with the use of OKT3, complicates management of HT patient. The experience in our center with 2 consecutive cohorts, treated with basiliximab (BAS) and OKT3, respectively, suggests that the use of BAS is associated, in addition to similar immunosuppressive efficacy and better safety profile than OKT3, with simpler patient management during the initial hospital stay, which could be associated with a reduction in posttransplant costs. Because few centers continue to use OKT3 as induction therapy in HT, more studies comparing cost-effectiveness of BAS vs polyclonal antilymphocyte antibodies (ATG) are needed.

Strategies to prevent cellular rejection in pediatric heart transplant recipients

Despite more than 40 years' experience in pediatric heart transplantation, cellular rejection remains a significant cause of morbidity and mortality. In this review, strategies and agents to prevent acute cellular rejection are discussed. Strategies to prevent rejection are divided into two phases - induction and maintenance therapies. Currently, the most commonly used induction agents are polyclonal antibodies (rabbit or equine antithymocyte globulin) and interleukin-2 receptor antibodies (daclizumab or basiliximab). Induction therapies have reduced early rejection, are renal sparing, and can reduce corticosteroid exposure, but have not yet been shown to have a longer term survival benefit. Multiple maintenance immunosuppressants are available. Nearly all regimens include a calcineurin inhibitor (either ciclosporin [cyclosporine] or tacrolimus). Most combinations in pediatric heart transplantation include an antiproliferative agent (azathioprine, mycophenolate mofetil or, less commonly, sirolimus). Everolimus has seen increasing use in adult heart transplant patients in Europe but, to date, its use is rare in pediatric heart transplantation. The use of corticosteroids as a third agent is still common, but strategies to avoid or minimize their use are increasing. The 'best' combination of therapies varies between studies. By gaining a better understanding of individuals' genetic and environmental risk factors, we may in the future be able to better predict the course of cardiac allografts and enhance our ability to tailor immunosuppression to individual patient variables with the ultimate goal of inducing a state of immune tolerance.

Immunosuppression armamentarium in 2010: mechanistic and clinical considerations

Effective immunosuppression is the key to successful organ transplantation, with success being defined as minimal rejection risk with concomitant minimal drug toxicities. Despite the general recognition of this fact, a paucity of appropriate clinical trials in children has contributed to lack of standardization of clinical management regimens, resulting in an extensive diversity of favored approaches. Nonetheless, although consensus has not been reached on the ideal approach to immunosuppression in pediatric transplantation, new drug therapies have contributed to a continuing improvement in graft and patient survival. Future clinical research must focus on diminishing the extensive burden of toxicities of these therapeutic agents in children.

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.

Induction Immunosuppression for Orthotopic Heart Transplantation: A Review

Objectives

To describe the appropriateness and safety of induction immunosuppression for patients at risk for fatal rejection, and to describe the safety and effectiveness profiles of the induction regimens available in the United States.

Data Sources

MEDLINE/PubMed database, EMBASE database, Google Scholar; references from pertinent articles were also reviewed to identify additional data.

Study Selection

A systematic literature review from January 1, 1980, through June 30, 2008, was performed. Included articles ranged from case series to prospective randomized controlled double-blind placebo-controlled trials that detailed the following topics with respect to induction immunosuppression: risk of fatal rejection, renal sparing, malignancy, OKT3, rabbit or equine antithymocyte globulin, daclizumab, basiliximab, and alemtuzumab.

Results

Patients at highest risk for fatal rejection experienced a survival benefit from induction immunosuppression, whereas all other patients experienced no benefit or harm. Most of the early data detail positive experiences with polyclonal antibody regimens. Several newer trials compare the use of polyclonal strategies with the use of anti-CD25 targeted monoclonal antibodies. Few researchers have assessed the usefulness of an anti-CD52 approach. Overall, induction therapy remains a poorly studied and widely variable practice among the major US heart transplant centers.

Conclusion

At present, the unrestricted use of induction for all patients does not seem prudent. Induction should be individualized for each patient on the basis of a well-designed protocol, careful analysis of the transplant center's demographics, and the effectiveness and safety profiles of the regimens used.

Recent progress in heart failure treatment and heart transplantation

There has been significant progress in heart failure treatment; its stages are defined as a management platform for cardiovascular specialists. Surgical ventricular restoration adds no outcome advantage in ischemic heart failure over coronary artery bypass surgery alone. Novel medical therapies may include cytokine blockade and the vasodilator, relaxin. Although diastolic failure is prevalent, its clinical significance is unclear. Cardiac resynchronization reduces mortality and hospitalization. Perioperative enoximone facilitates beta-blockade for prophylaxis against myocardial ischemia. Heart failure still determines outcome in pulmonary embolism and cardiac surgery. The practice of ventricular assist devices continues to progress. A profile system based on urgency of mechanical support will guide future outcome assessment. Clinical scoring systems will guide the management of right heart failure. Device flow determines the risk of cerebral hyperperfusion and neurologic dysfunction. Regardless of device type, renal dysfunction remains an important outcome determinant. Postoperative heparinization is increasingly challenged because of the risks of bleeding and heparin-induced thrombocytopenia. The practice of heart transplantation continues to mature. The bicaval rather than the biatrial technique improves short-term outcome. Oral sildenafil is effective for pulmonary hypertension and right ventricular support. Although immunosuppression with tacrolimus is beneficial, sirolimus is less nephrotoxic and preserves coronary vasomotor function. The induction of immunosuppression may be modified as it has a weak evidence base. Psychosocial factors also continue to influence clinical outcome significantly. The future of heart failure treatment is bright with signs of active growth and progress in this vibrant subspecialty.