Withdrawal of proliferation signal inhibitors due to adverse events in the maintenance phase of heart transplantation

The CECARI Study: Everolimus (Certican®) Initiation and Calcineurin Inhibitor Withdrawal in Maintenance Heart Transplant Recipients with Renal Insufficiency: A Multicenter, Randomized Trial

In this 3-year, open-label, multicenter study, 57 maintenance heart transplant recipients (>1 year after transplant) with renal insufficiency (eGFR 30–60 mL/min/1.73 m²) were randomized to start everolimus with CNI withdrawal (N = 29) or continue their current CNI-based immunosuppression (N = 28). The primary endpoint, change in measured glomerular filtration rate (mGFR) from baseline to year 3, did not differ significantly between both groups (+7.0 mL/min in the everolimus group versus +1.9 mL/min in the CNI group, p = 0.18). In the on-treatment analysis, the difference did reach statistical significance (+9.4 mL/min in the everolimus group versus +1.9 mL/min in the CNI group, p = 0.047). The composite safety endpoint of all-cause mortality, major adverse cardiovascular events, or treated acute rejection was not different between groups. Nonfatal adverse events occurred in 96.6% of patients in the everolimus group and 57.1% in the CNI group (p < 0.001). Ten patients (34.5%) in the everolimus group discontinued the study drug during follow-up due to adverse events. The poor adherence to the everolimus therapy might have masked a potential benefit of CNI withdrawal on renal function.

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.

Influence of proliferation signal inhibitors on vascular endothelial growth factor production in heart transplant recipients - preliminary report

Proliferation signal inhibitors (PSI) are especially beneficial for heart transplant recipients, but are rarely used due to frequent side effects. As they may be caused by vascular endothelial growth factor (VEGF), we performed a prospective cross-sectional pilot study to assess the influence of PSI and/or calcineurin inhibitors (CNI) presence in immunosuppressive protocols of heart transplant recipients on VEGF secretion. All electively screened heart transplant recipients willing to participate were enrolled in the study. The preliminary report was based on the results of the first 89 serum samples. The study group (n = 84) consisted of the PSI group (n = 14) further divided into the PSI + CNI subgroup (n = 10) and PSIw/oCNI subgroup (n = 4) based on concomitant CNI use, and the CNIw/oPSI group (n = 70) receiving CNI without PSI. The control group (n = 5) consisted of patients not requiring immunosuppression. VEGF was present in serum of 70 (83%) study group patients: median (range) 18 (0-316) pg/mL, mean 35 ± 57 pg/mL; in 13 (93%) PSI group patients: 22 (0-110) pg/mL, 28 ± 28 pg/mL, with 19 (8-20) pg/mL, 16 ± 6 pg/mL in the PSI + CNI subgroup, and 29 (0-110) pg/mL, 32 ± 32 pg/mL in the PSIw/oCNI subgroup. In the CNIw/oPSI group VEGF was present in 57 (81%) patients: 16 (0-316) pg/mL, 37 ± 62 pg/mL, and in the control group in 3 (60%) patients: 4 (0-110) pg/mL, 32 ± 48 pg/mL. None of the differences observed between any compared groups and/or subgroups was significant (χ² and Mann-Whitney U test). In conclusion, differences of VEGF concentration observed among groups imply the influence of PSI and CNI on VEGF production, but further studies involving higher numbers of participants are needed to prove it.

Everolimus in heart transplantation: an update

The evidence base relating to the use of everolimus in heart transplantation has expanded considerably in recent years, providing clinically relevant information regarding its use in clinical practice. Unless there are special considerations to take into account, all de novo heart transplant patients can be regarded as potential candidates for immunosuppression with everolimus and reduced-exposure calcineurin inhibitor therapy. Caution about the use of everolimus immediately after transplantation should be exercised in certain patients with the risk of severe proteinuria, with poor wound healing, or with uncontrolled severe hyperlipidemia. Initiation of everolimus in the early phase aftertransplant is not advisable in patients with severe pretransplant end-organ dysfunction or in patients on a left ventricular assist device beforetransplant who are at high risk of infection or of wound healing complications. The most frequent reason for introducing everolimus in maintenance heart transplant patients is to support minimization or withdrawal of calcineurin inhibitor therapy, for example, due to impaired renal function or malignancy. Due to its potential to inhibit the progression of cardiac allograft vasculopathy and to reduce cytomegalovirus infection, everolimus should be initiated as soon as possible after heart transplantation. Immediate and adequate reduction of CNI exposure is mandatory from the start of everolimus therapy.

Use of mTOR inhibitors in chronic heart transplant recipients with renal failure: calcineurin-inhibitors conversion or minimization?

BACKGROUND

In the last decade, mTOR inhibitors (mTOR-is) have become the cornerstone of the calcineurin inhibitor (CNI)-reduced/free regimens aimed to the preservation of post-transplant renal function. We compared utility and safety of the total replacement of calcineurin inhibitors with a mTOR-i with a strategy based on calcineurin inhibitor minimization and concomitant use of m-TOR-i.

METHODS

In a retrospective multi-center cohort of 394 maintenance cardiac recipients with renal failure (GFR<60 mL/min/1.73 m(2)), we compared 235 patients in whom CNI was replaced with a mTOR-i (sirolimus or everolimus) with 159 patients in whom mTOR-is were used to minimize CNIs. A propensity score analysis was carried out to balance between group differences.

RESULTS

Overall, after a median time of 2 years from mTOR-i initiation, between group differences for the evolution of renal function were not observed. In a multivariate adjusted model, improvement of renal function was limited to patients with mTOR-i usage within 5years after transplantation, particularly with the conversion strategy, and in those patients who could maintain mTOR-i therapy. Significant differences between strategies were not found for mortality, infection and mTOR-i withdrawal due to drug-related adverse events. However, conversion group tended to have a higher acute rejection incidence than the minimization group (p=0.07).

CONCLUSION

In terms of renal benefits, our results support an earlier use of mTOR-is, irrespective of the strategy. The selection of either a conversion or a CNI minimization protocol should be based on the clinical characteristics of the patients, particularly their rejection risk.

Sirolimus-FKBP12.6 impairs endothelial barrier function through protein kinase C-α activation and disruption of the p120-vascular endothelial cadherin interaction

OBJECTIVE

Sirolimus (SRL) is an immunosuppressant drug used to prevent rejection in organ transplantation and neointimal hyperplasia when delivered from drug-eluting stents. Major side effects of SRL include edema and local collection of intimal lipid deposits at drug-eluting stent sites, suggesting that SRL impairs endothelial barrier function (EBF). The aim of this study was to address the role of SRL on impaired EBF and the potential mechanisms involved.

APPROACH AND RESULTS

Cultured human aortic endothelial cells (HAECs) and intact human and mouse endothelium was examined to determine the effect of SRL, which binds FKBP12.6 to inhibit the mammalian target of rapamycin, on EBF. EBF, measured by transendothelial electrical resistance, was impaired in HAECs when treated with SRL or small interfering RNA for FKBP12.6 and reversed when pretreated with ryanodine, a stabilizer of ryanodine receptor 2 intracellular calcium release channels. Intracellular calcium increased in HAECs treated with SRL and normalized with ryanodine pretreatment. SRL-treated HAECs demonstrated increases in protein kinase C-α phosphorylation, a calcium sensitive serine/threonine kinase important in vascular endothelial (VE) cadherin barrier function through its interaction with p120-catenin (p120). Immunostaining of HAECs, human coronary and mouse aortic endothelium treated with SRL showed disruption of p120-VE cadherin interaction treated with SRL. SRL impairment of HAEC EBF was reduced with protein kinase C-α small interfering RNA. Mice treated with SRL demonstrated increased vascular permeability by Evans blue albumin extravasation in the lungs, heart, and aorta.

CONCLUSIONS

SRL-FKBP12.6 impairs EBF by activation of protein kinase C-α and downstream disruption of the p120-VE cadherin interaction in vascular endothelium. These data suggest this mechanism may be an important contributor of SRL side effects related to impaired EBF.