Conversion from calcineurin inhibitor-based immunosuppression to mammalian target of rapamycin inhibitors or belatacept in renal transplant recipients

Current treatment options for erectile dysfunction in kidney transplant recipients

INTRODUCTION

Erectile dysfunction (ED) and kidney dysfunction share common risk factors linked to conditions involving endothelial impairment, such as coronary artery disease, dyslipidemia, diabetes mellitus, hypertension, smoking, and obesity. Men with chronic kidney disease experience a high incidence and prevalence of ED. While a functional renal graft can alleviate the issue for some patients, a significant portion of recipients still experience ED (20%-50%).

OBJECTIVES

This narrative review describes the variety of current treatments modalities on ED in kidney transplant recipients (KTRs) and their clinical outcomes.

METHODS

MEDLINE, Web of Science, PubMed, and Google Scholar were used to find eligible articles pertaining to the treatment options of ED in KTRs. A total of 64 articles were evaluated.

RESULTS

In KTRs, ED stems from a multifaceted etiology: anxiety, drug side effects, interference with penile vascularity, or the response of cavernosal muscle to neurotransmitters, along with changes in the endocrine milieu. A diverse range of treatments to restore erectile function has proven to be safe and effective for KTRs. Options include drug therapy, surgical interventions, intracavernosal injection therapies, vacuum erection devices, and extracorporeal shockwave therapy.

CONCLUSION

The initial treatment approach may involve the use of a phosphodiesterase type 5 inhibitors at a low dosage, especially if testosterone-circulating levels align with the diagnosis of hypogonadism. The consideration of a combination therapy involving testosterone and phosphodiesterase type 5 inhibitors should be contemplated due to the associated beneficial effects. Extracorporeal shockwave therapy has shown positive short-term clinical and physiological effects on erectile function in patients who did not respond to first-line treatments, resulting in spontaneous erections sufficient for sexual penetration in 50% of cases. Penile implants should be considered as third-line options based on specific patient needs and compliance with clinical conditions.

"Eculizumab First" in the Management of Posttransplant Thrombotic Microangiopathy

Introduction

Posttransplant thrombotic microangiopathy (PT-TMA) is an uncommon event that characterizes approximately 3% to 14% of kidney transplants (KTs), and that is associated with a higher risk of delayed graft function and graft loss. PT-TMA occurs more frequently within the first 3 months after transplant and can be a manifestation of de novo disease or the recurrence of previous atypical hemolytic uremic syndrome (aHUS). Abnormalities in complement regulation genes could explain the increased susceptibility of some patients to PT-TMA. Eculizumab is a humanized monoclonal antibody that inhibits the formation of the membrane attack complex C5b-9. The aim of this study is to evaluate the efficacy of eculizumab as treatment for PT-TMA.

Methods

We retrospectively analyzed clinical records of 45 KT patients who received eculizumab immediately after the clinical diagnosis of PT-TMA.

Results

Kidney biopsy was performed in 91.1% of patients, and complement genetic study was performed in 64.4%. Of the kidney biopsies, 85.4% showed signs of TMA; genetic analysis revealed 1 pathogenetic variant, 2 variants of uncertain significance, 1 likely benign variant, 8 risk polymorphisms, and 27 risk haplotypes. After 2 weeks from the treatment starting, hemoglobin and platelets significantly increased. A remarkable improvement in kidney function was also observed. After 6 months, 28.8% of patients had a complete renal recovery whereas 44.4% had a partial recovery.

Conclusion

This is, to our knowledge, the largest series of KT patients with PT-TMA treated with eculizumab. These data suggest that eculizumab is associated with a normalization of hemolysis indices and an important and progressive improvement of graft function.

Unveiling the Incidence and Graft Survival Rate in Kidney Transplant Recipients With De Novo Thrombotic Microangiopathy: A Systematic Review and Meta-Analysis

De novo thrombotic microangiopathy (TMA) is a rare and challenging condition in kidney transplant recipients, with limited research on its incidence and impact on graft survival. This study conducted a systematic review and meta-analysis of 28 cohorts/single-arm studies and 46 case series/reports from database inception to June 2022. In meta-analysis, among 14,410 kidney allograft recipients, de novo TMA occurred in 3.20% [95% confidence interval (CI): 1.93-4.77], with systemic and renal-limited TMA rates of 1.38% (95% CI: 06.5-2.39) and 2.80% (95% CI: 1.27-4.91), respectively. The overall graft loss rate of de novo TMA was 33.79% (95% CI: 26.14-41.88) in meta-analysis. This study provides valuable insights into the incidence and graft outcomes of de novo TMA in kidney transplant recipients.

Erectile Dysfunction after Kidney Transplantation

Patients with kidney transplantation often have a worse quality of life than the general population. One of the reasons for this, in male patients, is the high prevalence of erectile dysfunction. This is mainly due to the presence of comorbidities, surgery for kidney transplantation, adverse drug effects, psychological changes related to chronic disease, as well as hyperprolactinemia and hypogonadism. Whenever these endocrine dysfunctions occur after kidney transplantation, they must be corrected with appropriate treatment, i.e., testosterone replacement therapy. Administration of the phosphodiesterase-5 inhibitor (PDE5i) sildenafil at the recommended posology does not significantly alter the pharmacokinetics of the calcineurin inhibitors cyclosporin A or tacrolimus and does not impair kidney allograft function. Tacrolimus increases the peak concentration and prolongs the half-life of PDE5i in kidney transplant patients and, therefore, daily administration cannot be recommended due to the significant drop in blood pressure. Intracavernous injection or topical application of alprostadil can be a second-line option for the treatment of erectile dysfunction after kidney transplantation, which does not alter cyclosporine concentrations and does not deteriorate kidney function. Finally, penile prostheses can be successfully implanted following pelvic organ transplantation after eliminating the risk of infection associated with surgery.

De novo thrombotic microangiopathy in two kidney transplant recipients from the same deceased donor: A case series

Thrombotic microangiopathy (TMA) is a recognized and serious complication of renal transplantation. Atypical hemolytic uremic syndrome (aHUS), a subset of TMA, occurs in the setting of dysregulation of the alternative complement pathway and can cause disease in native kidneys as well as recurrence in allografts. De novo TMA represents a classification of TMA post-transplant in the absence of clinical or histopathological evidence of TMA or aHUS in the native kidney. De novo TMA is a more heterogeneous syndrome than aHUS and the pathogenesis and risk factors for de novo TMA are poorly understood. The association between calcineurin inhibitors (CNI) and de novo TMA is controversial. Anti-complement blockade therapy with eculizumab is effective in some cases, but more studies are needed to identify appropriate candidates for therapy. We present two cases of de novo TMA occurring immediately in recipients from the same deceased donor and provoking the question of whether deceased donor-related factors could represent risks for developing de novo TMA.

Thrombotic microangiopathy after renal transplantation: Current insights in de novo and recurrent disease

Thrombotic microangiopathy (TMA) is one of the most devastating sequalae of kidney transplantation. A number of published articles have covered either de novo or recurrent TMA in an isolated manner. We have, hereby, in this article endeavored to address both types of TMA in a comparative mode. We appreciate that de novo TMA is more common and its prognosis is poorer than recurrent TMA; the latter has a genetic background, with mutations that impact disease behavior and, consequently, allograft and patient survival. Post-transplant TMA can occur as a recurrence of the disease involving the native kidney or as de novo disease with no evidence of previous involvement before transplant. While atypical hemolytic uremic syndrome is a rare disease that results from complement dysregulation with alternative pathway overactivity, de novo TMA is a heterogenous set of various etiologies and constitutes the vast majority of post-transplant TMA cases. Management of both diseases varies from simple maneuvers, e.g., plasmapheresis, drug withdrawal or dose modification, to lifelong complement blockade, which is rather costly. Careful donor selection and proper recipient preparation, including complete genetic screening, would be a pragmatic approach. Novel therapies, e.g., purified products of the deficient genes, though promising in theory, are not yet of proven value.

De novo thrombotic microangiopathy after kidney transplantation

Thrombotic microangiopathy (TMA) is a serious complication of transplantation that adversely affects kidney transplant recipient and allograft survival. Post-transplant TMA is usually classified into two categories: 1) recurrent TMA and 2) de novo TMA. Atypical hemolytic uremic syndrome (aHUS) resulting from dysregulation and over-activation of the alternate complement pathway is a rare disease but the most common diagnosis associated with recurrence in the allografts. De novo TMA, on the other hand, represents an overwhelming majority of the cases of post-transplant TMA and is a substantially more heterogeneous entity than recurrent aHUS. Here, we review the etio-pathogenesis, diagnosis and treatment options for de novo post-transplant TMA. It is usually in the setting of calcineurin inhibitor use, mammalian target of rapamycin inhibitor use, or antibody mediated rejection; recently genetic mutations in complement regulatory genes for Factor H and Factor I similar to those described in aHUS have been reported in up to a third of these patients. Systemic signs of TMA are frequently absent, and a renal allograft biopsy is often needed to establish the diagnosis. Although withdrawal of the offending agents is usually the first line of treatment and resolution of laboratory abnormalities has been documented with this approach in several case reports and case series, available retrospective data demonstrate lack of benefit in long-term graft outcomes. Co-stimulation blockage with belatacept provides an effective alternate immunosuppressive strategy for these patients. Anti-complement therapy with eculizumab is effective in some cases; further work is required to define which patients with TMA (with and without concomitant antibody-mediated rejection) would benefit from receiving this treatment, and what biomarkers can be used to identify them.

Efficacy and safety of early tacrolimus conversion to sirolimus after kidney transplantation: Long-term results of a prospective randomized study

We report a prospective, open-label, randomized study to evaluate the safety and efficacy of converting patients with a stable renal function from tacrolimus (Tac)-based regimen to a sirolimus (SRL)-based regimen after kidney transplantation. Fifty-eight low-risk renal allograft recipients who receiving Tac 6 months posttransplant, were randomly assigned to continue Tac (n = 29) or convert to SRL (n = 29). We evaluated the 3-year outcomes including patient and graft survival, graft function, and safety profile. Three-year patient and graft survival in SRL and Tac groups were 93.1% versus 100% (P = 0.32), and 89.7% versus 100% (P = 0.11), respectively. However, the SRL group had a significantly better renal function, from the 2^nd year posttransplant until the last follow-up. Four (13.8%) patients in the SRL group and 3 (10.3%) in the Tac group (P = 0.5) developed biopsy-proven acute rejection. Mean urinary protein excretion increased significantly after SRL conversion. Diastolic blood pressure was significantly lower at the end of the study in patients who eliminated Tac (80.4 vs. 75.6 mmHg in Tac and SRL group, respectively) (P = 0.03). Mean hemoglobin concentrations decreased after SRL conversion and remained significantly lower from 12 months to 36 months (P = 0.01). The mean serum cholesterol (540 ± 44 mg/dl) and triglyceride (177 ± 27 mg/dl) increased significantly in the SRL group, compared to Tac group (487 ± 62 mg/dl) (P = 0.03) and (141 ± 26 mg/dl) (P = 0.04). Our experience demonstrates that conversion to SRL from calcineurin inhibitors-based therapy may result in better renal function and blood pressure control in renal transplant recipients without an increased risk of acute rejection. However, these benefits have not resulted in a growing advantage in graft or patient survival.

Safety and Efficacy Outcomes 3 Years After Switching to Belatacept From a Calcineurin Inhibitor in Kidney Transplant Recipients: Results From a Phase 2 Randomized Trial

BACKGROUND

In a phase 2 study, kidney transplant recipients of low immunologic risk who switched from a calcineurin inhibitor (CNI) to belatacept had improved kidney function at 12 months postconversion versus those continuing CNI therapy, with a low rate of acute rejection and no transplant loss.

STUDY DESIGN

36-month follow-up of the intention-to-treat population.

SETTING & PARTICIPANTS

CNI-treated adult kidney transplant recipients with stable transplant function (estimated glomerular filtration rate [eGFR], 35-75mL/min/1.73m²).

INTERVENTIONS

At 6 to 36 months posttransplantation, patients were randomly assigned to switch to belatacept-based immunosuppression (n=84) or continue CNI-based therapy (n=89).

OUTCOMES

Safety was the primary outcome. eGFR, acute rejection, transplant loss, and death were also assessed.

MEASUREMENTS

Treatment exposure-adjusted incidence rates for safety, repeated-measures modeling for eGFR, Kaplan-Meier analyses for efficacy.

RESULTS

Serious adverse events occurred in 33 (39%) belatacept-treated patients and 36 (40%) patients in the CNI group. Treatment exposure-adjusted incidence rates for serious infections (belatacept vs CNI, 10.21 vs 9.31 per 100 person-years) and malignancies (3.01 vs 3.41 per 100 person-years) were similar. More patients in the belatacept versus CNI group had any-grade viral infections (14.60 vs 11.00 per 100 person-years). No posttransplantation lymphoproliferative disorder was reported. Belatacept-treated patients had a significantly greater estimated gain in mean eGFR (1.90 vs 0.07mL/min/1.73m² per year; P for time-by-treatment interaction effect = 0.01). The probability of acute rejection was not significantly different for belatacept (8.38% vs 3.60%; HR, 2.50 [95% CI, 0.65-9.65; P=0.2). HR for the comparison of belatacept to the CNI group for time to death or transplant loss was 1.00 (95% CI, 0.14-7.07; P=0.9).

LIMITATIONS

Exploratory post hoc analysis with a small sample size.

CONCLUSIONS

Switching patients from a CNI to belatacept may represent a safe approach to immunosuppression and is being further explored in an ongoing phase 3b trial.

Transplant Tolerance Induction in Newborn Infants: Mechanisms, Advantages, and Potential Strategies

Although several tolerance induction protocols have been successfully implemented in adult renal transplantation, no tolerance induction approach has, as yet, been defined for solid organ transplantations in young infants. Pediatric transplant recipients have a pressing demand for the elaboration of tolerance induction regimens. Indeed, since they display a longer survival time, they are exposed to a higher level of risks linked to long-term immunosuppression (IS) and to chronic rejection. Interestingly, central tolerance induction may be of great interest in newborns, because of their immunological immaturity and the important role of the thymus at this early stage in life. The present review aims to clarify mechanisms and strategies of tolerance induction in these immunologically premature recipients. We first introduce the discovery and mechanisms of neonatal tolerance in murine experimental models and subsequently analyze tolerance induction in human newborn infants. Hematopoietic mixed chimerism in neonates is also discussed based on in utero hematopoietic stem cell (HSC) transplant studies. Then, we review the recent advances in tolerance induction approaches in adults, including the infusion of HSCs associated with less toxic conditioning regimens, regulatory T cells/facilitating cells/mesenchymal stem cells transplantation, costimulatory blockade, and thymus manipulation. Finally, IS withdrawal in pediatric solid organ transplant is discussed. In conclusion, the establishment of transplant tolerance induction in infants is promising and deserves further investigations. Future studies could focus on the selection of patients, on less toxic conditioning regimens, and on biomarkers for IS minimization or withdrawal.

Safety of mTOR inhibitors in adult solid organ transplantation

INTRODUCTION

Mammalian target of rapamycin (mTOR) inhibitors (sirolimus and everolimus) are a class of immunosuppressive drugs approved for solid organ transplantation (SOT). By inhibiting the ubiquitous mTOR pathway, they present a peculiar safety profile. The increased incidence of serious adverse events in early studies halted the enthusiasm as a kidney sparing alternative to calcineurin inhibitors (CNI).

AREAS COVERED

Herein we review mTOR inhibitors safety profile for adult organ transplantation, ranging from acute side effects, such as lymphoceles, delayed wound healing, or cytopenias, to long-term ones which increase morbidity and mortality, such as cancer risk and metabolic profile. Infection, proteinuria, and cutaneous safety profiles are also addressed.

EXPERT OPINION

In the authors' opinion, mTOR inhibitors are a safe alternative to standard immunosuppression therapy with CNI and mycophenolate/azathioprine. Mild adverse events can be easily managed with an increased awareness and close monitoring of trough levels. Most serious side effects are dose- and organ-dependent. In kidney and heart transplantation mTOR inhibitors may be safely used as either low-dose de novo or through early-conversion. In the liver, conversion 4 weeks post-transplantation may reduce long-term chronic kidney disease secondary to calcineurin nephrotoxicity, without increasing hepatic artery/portal vein thrombosis.

Simultaneous pancreas and kidney transplantation: current trends and future directions

Purpose of review

Important trends are being observed in pancreas transplantation in the USA. We will describe recent trends in simultaneous pancreas kidney (SPK) transplantation related to immunosuppression, treatment of rejection, and transplantation for patients of advanced age and C-peptide positive diabetes.

Recent findings

Rates of pancreas transplantation have declined, despite improved pancreatic graft outcomes. Regarding immunosuppression, trends in SPK transplantation include T-cell depletion induction therapy, waning mammalian target of rapamycin inhibitor use and steroid use in greater than 50% of pancreas transplant recipients with few patients undergoing late steroid weaning. Rejection of the pancreas may be discordant with the kidney after SPK and there is a greater appreciation of antibody-mediated rejection of the pancreas allograft. De-novo donor-specific antibody without graft dysfunction remains an active area of study, and the treatment for this condition is unclear. SPKs are being performed with greater frequency in type 2 diabetes mellitus patients and in patients of advanced age, with exemplary results.

Summary

The current state of the art in SPK transplantation is yielding superb and improving results.