mTOR inhibitors in pediatric kidney transplantation

Role of brentuximab vedotin plus sirolimus in the treatment of classical Hodgkin lymphoma type post-transplant lymphoproliferative disorder: a case-based review

Post-transplant lymphoproliferative disorder (PTLD) is a common secondary malignancy after transplantation, which has been recognized as a life-threatening complication. Hodgkin lymphoma (HL)-type PTLD is the rarest of four subtypes of PTLD, which has no treatment guideline due to its rarity. HL-type PTLD includes classical HL-type PTLD (cHL-PTLD) and HL-like PTLD. In our study, we reported the case of successful treatment using brentuximab vedotin (BV) plus sirolimus for a patient with classical HL-type PTLD in detail. Lymph node biopsy showed a picture of classical HL with mixed cellularity subtype, and immunophenotyping suggested CD30 strong positivity. Due to his impaired physical condition, we decided against intensive chemotherapy and started BV treatment with immunosuppressive agents switched to sirolimus. The 66-year-old patient with cHL-PTLD had achieved a durable complete remission for over a 1-year follow-up period. Additionally, we analyzed the clinical profile and outcomes in PTLD patients who used BV monotherapy or combined therapy by literature review. In summary, this case-based review might provide clues that treatment of cHL-PTLD with new modalities such as BV monotherapy or combination therapy, together with improvements in the immunosuppressive regimens like sirolimus, might be a feasible and chemotherapy-free approach, but warrants further evaluation in a larger patient cohort.

Clinical Practice Guidelines for tuberous sclerosis complex-associated renal angiomyolipoma by the Japanese Urological Association: Summary of the update

New clinical issues have been raised through an interval of 7 years from the previous version (2016). In this study, we update the "Clinical Practice Guidelines for tuberous sclerosis complex-associated renal angiomyolipoma" as a 2023 version under guidance by the Japanese Urological Association. The present guidelines were cooperatively prepared by the Japanese Urological Association and Japanese Society of Tuberous Sclerosis Complex; committee members belonging to one of the two societies or specializing in the treatment of this disease were selected to prepare the guidelines in accordance with the "Guidance for preparing treatment guidelines" published by Minds (2020 version). The "Introduction" consisted of four sections, "Background Questions (BQ)" consisted of four sections, "Clinical Questions (CQ)" consisted of three sections, and "Future Questions (FQ)" consisted of three sections (total: 14 sections). Concerning CQ, an agreement was confirmed through voting by the committee members based on the direction and strength of recommendation, accuracy of evidence, and recommendation comments. The present guidelines were updated based on the current evidence. We hope that the guidelines will provide guiding principles for the treatment of tuberous sclerosis complex-associated renal angiomyolipoma to many urologists, becoming a foundation for subsequent updating.

Children Are Not Small Adults: Similarities and Differences in Renal Transplantation Between Adults and Pediatrics

Kidney transplantation is the treatment of choice for all patients with end-stage kidney disease, including pediatric patients. Graft survival in pediatrics was lagging behind adults, but now is comparable with the adult cohort. Although many of the protocols have been adopted from adults, there are issues unique to pediatrics that one should be aware of to take care of this population. These issues include recipient size consideration, increased incidence of viral infections, problems related to growth, common occurrence of underlying urological issues, and psychosocial issues. This article addresses the similarities and differences in renal transplantation, from preparing a patient for transplant, the transplant process, to post-transplant complications.

Induction and maintenance immunosuppression in pediatric kidney transplantation-Advances and controversies

Advances in immunosuppression have improved graft survival in pediatric kidney transplant recipients; however, treatment-related toxicities need to be balanced against the possibility of graft rejection. Several immunosuppressive agents are available for use in transplant recipients; however, the optimal combinations of agents remain unclear, resulting in variations in institutional protocols. Lymphocyte-depleting antibodies, specifically ATG, are the most common induction agent used for pediatric kidney transplantation in the US. Basiliximab may be used for induction in immunologically low-risk children; however, pediatric data are scarce. CNIs and antiproliferative agents (mostly Tac and mycophenolate in recent years) constitute the backbone of maintenance immunosuppression. Steroid-avoidance maintenance regimens remain controversial. Belatacept and mTOR inhibitors are used in children under specific circumstances such as non-adherence or CNI toxicity. This article reviews the indications, mechanism of action, efficacy, dosing, and side effect profiles of various immunosuppressive agents available for pediatric kidney transplantation.

Steering Transplant Immunosuppression by Measuring Virus-Specific T Cell Levels: The Randomized, Controlled IVIST Trial

BACKGROUND

Pharmacokinetic monitoring is insufficient to estimate the intensity of immunosuppression after transplantation. Virus-specific T cells correlate with both virus-specific and general cellular immune defense. Additional steering of immunosuppressive therapy by virus-specific T cell levels might optimize dosing of immunosuppressants.

METHODS

In a multicenter, randomized, controlled trial, we randomized 64 pediatric kidney recipients to a control group with trough-level monitoring of immunosuppressants or to an intervention group with additional steering of immunosuppressive therapy by levels of virus-specific T cells (quantified by cytokine flow cytometry). Both groups received immunosuppression with cyclosporin A and everolimus in the same target range of trough levels. Primary end point was eGFR 2 years after transplantation.

RESULTS

In the primary analysis, we detected no difference in eGFR for the intervention and control groups 2 years after transplantation, although baseline eGFR 1 month after transplantation was lower in the intervention group versus the control group. Compared with controls, patients in the intervention group received significantly lower daily doses of everolimus and nonsignificantly lower doses of cyclosporin A, resulting in significantly lower trough levels of everolimus (3.5 versus 4.5 µg/L, P<0.001) and cyclosporin A (47.4 versus 64.1 µg/L, P<0.001). Only 20% of patients in the intervention group versus 47% in the control group received glucocorticoids 2 years after transplantation (P=0.04). The groups had similar numbers of donor-specific antibodies and serious adverse events.

CONCLUSIONS

Steering immunosuppressive therapy by virus-specific T cell levels in addition to pharmacokinetic monitoring seems safe, results in a similar eGFR, and personalizes immunosuppressive therapy by lowering exposure to immunosuppressive drugs, likely resulting in lower drug costs.

CLINICAL TRIAL REGISTRY NAME AND REGISTRATION NUMBER

IVIST trial, https://www.clinicaltrialsregister.eu/ctr-search/search?query=2009-012436-32 and ISRCTN89806912.

Nephrotoxins and nephrotoxic acute kidney injury

Although the concept of nephrotoxicity has been recognized for more than 80 years, interest in nephrotoxins has intensified dramatically over the past two decades. Much of this attention has rightfully been focused on pharmaceutical agents and iatrogenic harm; however, it is important for providers to recognize that nephrotoxins can be found in naturally occurring substances as well. Although nephrotoxins exist in a myriad of forms, the means by which they induce injury can be organized into a few categories. For most of these agents, regardless of the mechanism, the final common pathway is acute kidney injury (AKI). Unfortunately, therapeutic options are limited and no treatments currently exist to reverse nephrotoxic AKI once it occurs. As a result, current strategies focus on increased awareness, nephrotoxin avoidance, early injury detection, and mitigation of disease severity. The goal of this review is to summarize our current understanding of nephrotoxic mechanisms and the epidemiology of nephrotoxic AKI. Additionally, avoidance and preventative strategies are discussed, screening approaches are suggested, and chronic monitoring recommendations are made.

Cardiovascular Risk Factors are Inversely Associated With Omega-3 Polyunsaturated Fatty Acid Plasma Levels in Pediatric Kidney Transplant Recipients

OBJECTIVES

High plasma levels of the omega-3 fatty acids eicosapentaenoic acid (EPA), docosahexaenoic acid, and docosapentaenoic acid associates with positive outcomes in adult renal transplant recipients. However, data from pediatric populations are scarce. The aim of the study was to assess the fatty acid profile in a pediatric renal transplantation cohort and to examine the associations between plasma omega-3 fatty acids and cardiovascular disease (CVD) risk factors.

METHODS

In this cross-sectional study comprising 53 children (median age, 12.2 years; 32 boys) with a renal transplant, we assessed the prevalence of CVD risk factors as well as markers of end organ damage: carotid intima-media thickness (cIMT) and left ventricular mass index. The associations between plasma omega-3 fatty acids and CVD risk factors were assessed.

RESULTS

Twenty-five (47%) patients were preemptively transplanted. Seventy-six percent had dyslipidemia and 51% had hypertension. The mean left ventricular mass index was 40.4 ± 14.3 g/m^2.7, and 14% had left ventricular hypertrophy. The mean cIMT was 0.41 ± 0.04 mm. In a multivariate linear regression, EPA levels were inversely associated to blood pressure (β coeff. = -0.37, P = .007), triglycerides (β coeff. = -0.44, P = .01), and high-density lipoprotein cholesterol (β coeff. = -0.41, P = .01).

CONCLUSION

EPA levels are inversely associated with components of the metabolic syndrome, which may provide support for specific dietary advice or supplementation in this patient population. cIMT is less pronounced in our cohort than in comparable cohorts with lower rate of preemptive transplantations. Our results need replication in prospective cohorts.

A Pediatric Case of Sirolimus-Associated Pneumonitis After Kidney Transplantation

Sirolimus is an immunosuppressive medication often used in solid organ transplantation. It has been associated with severe side effects, including pulmonary toxicity. In adult patients, a single center study found that 14% of those treated with sirolimus developed pulmonary pneumonitis; however, the incidence in the pediatric population is not known. Most reports in adult patients indicate that elevated drug concentrations and a prolonged duration of use are associated with pulmonary toxicity. We report a case of a 17-year-old male kidney transplant recipient who developed rapid-onset respiratory failure, necessitating mechanical ventilation and acute renal replacement therapy for ultrafiltration secondary to sirolimus-induced pneumonitis. He had been treated for acute rejection with corticosteroids 17 days prior to the development of pneumonitis. His symptoms developed within 1 week of initiation of sirolimus and with a serum concentration of 1.1 ng/mL. Sirolimus was discontinued, and, following aggressive diuresis and ventilatory support, his respiratory status returned to baseline. Sirolimus-induced pneumonitis is an important diagnosis to be considered in any transplant recipient receiving sirolimus with new onset fever, cough, or dyspnea without an identifiable source, especially if there is a preceding history of treatment with high-dose corticosteroids.

Prophylactic treatment of rapamycin ameliorates naturally developing and episode -induced heterotopic ossification in mice expressing human mutant ACVR1

Background

Fibrodysplasia ossificans progressiva (FOP) is a rare autosomal-dominant disease characterized by heterotopic ossification (HO) in soft tissues and caused by a mutation of the ACVR1A/ALK2 gene. Activin-A is a key molecule for initiating the process of HO via the activation of mTOR, while rapamycin, an mTOR inhibitor, effectively inhibits the Activin-A-induced HO. However, few reports have verified the effect of rapamycin on FOP in clinical perspectives.

Methods

We investigated the effect of rapamycin for different clinical situations by using mice conditionally expressing human mutant ACVR1A/ALK2 gene. We also compared the effect of rapamycin between early and episode-initiated treatments for each situation.

Results

Continuous, episode-independent administration of rapamycin reduced the incidence and severity of HO in the natural course of FOP mice. Pinch-injury induced HO not only at the injured sites, but also in the contralateral limbs and provoked a prolonged production of Activin-A in inflammatory cells. Although both early and injury-initiated treatment of rapamycin suppressed HO in the injured sites, the former was more effective at preventing HO in the contralateral limbs. Rapamycin was also effective at reducing the volume of recurrent HO after the surgical resection of injury-induced HO, for which the early treatment was more effective.

Conclusion

Our study suggested that prophylactic treatment will be a choice of method for the clinical application of rapamycin for FOP.

Assessing the efficacy of mammalian target of rapamycin inhibitors by phosphorylation of p70S6K in CD4-positive cells of liver transplant patients

The activity of p70S6 kinase located downstream of the mammalian target of rapamycin (mTOR) pathway is sensitive to mTOR inhibitors. However, the methods of assessing p70S6 kinase activity are still unclear. This study aimed to investigate p70S6 kinase activity in CD4-positive cells of liver transplant patients.Liver transplant patients treated with mTOR inhibitors were recruited from Beijing Chaoyang Hospital between October 2014 and October 2016. The influence of mycophenolic acid (MPA) derivatives and prednisone on p70S6 kinase phosphorylation in CD4-positive cells was examined in liver transplant patients and healthy controls (HCs). The phosphorylation of p70S6K in CD4 + CD25 regulatory T cells (Treg cells) and CD4 + CD25- T effector cells was analyzed by phospho-flow cytometry.The phospho-flow technique detected a significant loss of p70S6 kinase phosphorylation in CD4-positive cells of patients treated with mTOR inhibitors compared with HCs. MPA derivatives and prednisone did not affect p70S6 kinase phosphorylation significantly. No significant difference in p70S6 kinase phosphorylation was observed when the whole blood was stored within 3 hours at room temperature. The phosphorylation of p70S6K was significantly lower in CD4 + CD25 Treg cells than in CD4 + CD25-T effector cells in HCs. After liver transplant patients were treated with mTOR inhibitors, p70S6K phosphorylation was more reduced in CD4 + CD25-T effector cells than in CD4 + CD25 Treg cells.The presence of phosphorylation of p70S6 kinase in CD4-positive cells was reduced in liver transplant patients who were treated by mTOR inhibitors.

Indications and efficacy of conversion from tacrolimus- to sirolimus-based immunosuppression in pediatric patients who underwent liver transplantation for unresectable hepatoblastoma

SRL-based immunosuppressive strategies in pediatric liver transplantation are not clearly defined, especially within the first year after liver transplant. TAC is the more common, traditional immunosuppressant used. However, SRL may modulate TAC-associated kidney injury and may also have antiproliferative properties that are valuable in the management of patients following liver transplantation for HB. We sought to determine whether early conversion from TAC to SRL was safe, effective, and beneficial in a subset of liver transplant recipients with unresectable HB exposed to CDDP-based chemotherapy. Between 2008 and 2013, six patients were transplanted for unresectable HB. All patients received at least one cycle of CDDP-based chemotherapy prior to transplant. All patients were switched from TAC- to SRL-based immunosuppression within 1 year of transplant. Five patients had improvement in their mGFR, while one patient had a slight decline. The improvement in mGFR was statistically significant. No adverse events were identified. Three patients had BPAR that responded to pulsed steroids. Historical controls showed similar rates of BPAR within the first year after transplant. There were no identified HB recurrences in the follow-up time period. Conversion from TAC to SRL appears to be safe and effective in this selected group of pediatric liver transplant recipients without adverse reaction or HB recurrences.

Long-term outcome in a case series of Denys-Drash syndrome

Background

Denys-Drash syndrome (DDS) is a rare disease caused by mutations in exons 8 and 9 of the WT1 gene. It is characterized by the association of early onset steroid-resistant nephrotic syndrome (SRNS), Wilms' tumour and, in some patients, intersex disorders, with increasing risk of gonadoblastoma. There are few published data concerning the long-term outcome of patients with DDS. The aim of this study was to report our experience.

Methods

Data were collected from five children (three boys) with confirmed DDS diagnosed from 1996 to 2017. The mean follow-up of these patients was 16 years.

Results

The patients presented with SRNS and diffuse mesangial sclerosis at renal biopsy. All patients were hypertensive and progressed to end-stage kidney disease, initiating dialysis at a mean age of 28 months. Three patients developed Wilms' tumour 9 months after the SRNS was identified, which was treated by nephrectomy and chemotherapy. All five patients received kidney transplantation. SRNS did not recur after transplantation in any of the patients and graft survival was similar to that of other kidney transplant recipients in our programme. All three boys had ambiguous genitalia and cryptorchidism but a confirmed male karyotype (46, XY). One girl presented with gonadal agenesis, whereas the other one had normal female ovarian tissue and external genitalia. Both girls had a female karyotype (46, XX). Gonadoblastoma was not observed at any case.

Conclusions

Early DDS recognition in patients with SRNS is crucial due to its low prevalence, the specific treatment approach required and early detection of Wilms' tumour. Few data are available regarding long-term outcomes.

Regulation of human T cell responses by dNP2-ctCTLA-4 inhibits human skin and microvessel graft rejection

Manipulation of human T cell functioning by delivery of macromolecules such as DNA, RNA, or protein is limited, unless the human T cells have been stimulated or electropermeabilized. To achieve successful adaptation and survival of a grafted organ, the alloreactive T cells that induce graft rejection must be regulated. Corticosteroids, calcineurin inhibitors, and mTOR inhibitors, which are systemic immunosuppressants, are currently used for transplantation, with significant side effects. In this study, we demonstrated that a cell-permeable peptide (CPP), dNP2, could efficiently deliver proteins into human CD4 and CD8 T cells. We confirmed regulatory functioning of the cytoplasmic domain of CTLA-4 conjugated with dNP2 (dNP2-ctCTLA-4) in human T cell activation, proliferation, and chemokine receptor expression. We utilized a human skin allograft system in SCID/beige mice to examine whether dNP2-ctCTLA-4 could inhibit allograft rejection by controlling T cell responses. The grafted skin tissue inflammation, allogeneic T cell infiltration, and blood cytokine level was markedly reduced by dNP2-ctCTLA-4, resulting in successful transplantation. In addition, it also inhibited T cell alloresponses against microvessels formed form Bcl-2-transduced human umbilical vein endothelial cells implanted into Balb/c Rag1^-/-/IL-2Rγ^-/- double knockout (DKO) mice, assessed as reduced T cell infiltration and granzyme B expression. These results collectively suggest that dNP2 peptide conjugation offers a valuable tool for delivering macromolecules like proteins into human T cells, and dNP2-ctCTLA-4 is a novel agent that shows potential in controlling human T cell responses to allow successful adaptation of grafted tissues.

mTOR signalling: jack-of-all-trades 1

The mechanistic target of rapamycin (mTOR) is an evolutionarily conserved serine/threonine kinase that senses and integrates environmental information into cellular regulation and homeostasis. Accumulating evidence has suggested a master role of mTOR signalling in many fundamental aspects of cell biology and organismal development. mTOR deregulation is implicated in a broad range of pathological conditions, including diabetes, cancer, neurodegenerative diseases, myopathies, inflammatory, infectious, and autoimmune conditions. Here, we review recent advances in our knowledge of mTOR signalling in mammalian physiology. We also discuss the impact of mTOR alteration in human diseases and how targeting mTOR function can treat human diseases.

Everolimus for pediatric patients with acute graft-versus-host disease after hematopoietic stem cell transplantation: A pilot study

Acute graft-versus-host disease (aGVHD) is a significant cause of morbidity and mortality after allogeneic hematopoietic stem cell transplantation (HSCT). Due to the poor prognosis for patients not responding to first-line steroids treatment, improvements in aGVHD therapy are needed. Everolimus is a promising candidate that combines immunosuppressive properties with anti-neoplastic effects. Here, we retrospectively reviewed the efficacy of everolimus with steroids as primary treatment in 13 patients with grade II to grade IV aGVHD after HSCT. Among them, 12 (92.3%) had complete response to everolimus with steroids without additional immunosuppressive agents. The median duration of therapy was 76 days (range 20-110). Asymptomatic hypertriglyceridemia was the most common therapy complication (69.2%), but treatment interruption was not needed. Thrombotic microangiopathy was rare (7.7%), but can be quickly solved by stopping everolimus and cyclosporine treatment. Other toxicities were manageable. Two patients developed chronic GVHD (15.4%), limited in one and extensive in the other. The overall survival was 76.9% with a median follow-up of 3.4 years after HSCT (range 0.7-5.7). Accordingly, everolimus with steroids were feasible for patients with aGVHD after HSCT as primary treatment. Further large-scale studies are required.

Treatment of renal angiomyolipoma in tuberous sclerosis complex (TSC) patients

In adult tuberous sclerosis complex (TSC) patients, renal complications are the leading cause of death. Beginning in childhood, up to 80 % of patients develop renal angiomyolipoma characterized by a size-dependent risk of life-threatening bleeding. After discovery of the two causative genes, TSC1 and TSC2, and the role of mammalian target of rapamycin (mTOR) regulation in the pathogenesis of TSC, an increasing number of clinical studies evaluating mTOR inhibition in TSC patients have shown impressive results in many organ manifestations, such as brain, lung, and kidney. For renal angiomyolipoma, mTOR inhibitor treatment fundamentally changed the approach from preventive embolization or even partial nephrectomy to everolimus treatment in order to preserve kidney function.

Calcineurin inhibitor- and corticosteroid-free immunosuppression in pediatric heart transplant patients

Pediatric heart transplant patients at our institution are immunosuppressed with a CNI and another immune-modulating agent without utilizing corticosteroids. Patients whose renal function worsened and who did not respond to CNI minimization had their CNI discontinued. The clinical history of 35 pediatric heart transplant patients with significant renal insufficiency whose CNI was discontinued was retrospectively analyzed. Data including serum creatinine and weight were collected before, at time of, and every 3-6 months after CNI discontinuation. This was used to calculate an eGFR. Cardiac allograft rejection and mortality data were also collected. CNI discontinuation occurred 39 times in 35 patients. The median eGFR significantly increased by 14 mL/min 3 months after CNI discontinuation and the increase continued to be significant (P≤.05) at 5 years. Freedom from rejection analysis showed no difference between graft rejection 2 years before versus after CNI discontinuation (P=.437). No mortality was associated with CNI discontinuation. Immunosuppression free of CNIs and corticosteroids appears to be a safe alternative in pediatric heart transplant patients with significant renal insufficiency. Furthermore, this strategy can significantly reverse renal insufficiency, even late after transplantation.

Sirolimus and tacrolimus coefficient of variation is associated with rejection, donor-specific antibodies, and nonadherence

BACKGROUND

Immunosuppression medication nonadherence has been associated with donor-specific antibodies and treatment-refractory rejection. Drug-level monitoring is a practical direct marker for nonadherence, as variations indicate erratic ingestion of medication. We previously reported that high variability in tacrolimus trough levels determined by the percent coefficient of variation (CV %) and standard deviation (SD) were associated with biopsy-proven rejection. We hypothesized that the CV % and SD in patients on a sirolimus/low-dose tacrolimus regimen may associate with self-reported medication nonadherence, rejection and donor-specific antibodies.

METHODS

In this pilot feasibility study, we studied 37 biopsies in 23 pediatric renal transplant patients on both sirolimus and tacrolimus immunosuppression; CV %, SD, de novo donor-specific antibodies, rejection, and self-reported adherence were examined.

RESULTS

A cut-off sirolimus CV % of 25 maximized the percentage of biopsies correctly classified as rejection (32 of 37, or 86 %, p = 0.001). A cut-off tacrolimus CV % of 31 maximized the percentage of correctly classified biopsies (25 of 37, or 68 %, p = 0.09). Among patients with both high sirolimus and tacrolimus CV %, 67 % developed de novo donor-specific antibodies (p = 0.002) with a DQ predominance and 71 % reported nonadherence (p = 0.05).

CONCLUSIONS

In pediatric renal transplantation, sirolimus and tacrolimus CV % is a potential tool for monitoring patients at risk for allograft rejection and donor-specific antibodies secondary to medication nonadherence.

Sirolimus therapy in a child with partially diazoxide-responsive hyperinsulinaemic hypoglycaemia

Hyperinsulinaemic hypoglycaemia (HH), which causes persistent neonatal hypoglycaemia, can result in neurological damage and it’s management is challenging. Diazoxide is the first-line treatment, albeit not all patients will fully respond to it, as episodes of hypoglycaemia may persist and it entails unpleasant adverse effects. Sirolimus, an mTOR inhibitor, has reportedly been successful in treating children with severe diffuse HH, thus obviating the need for pancreatectomy. We report a girl with HH, with a novel heterozygous ABCC8 gene missense mutation (c.4154A>T/ p.Lys1385Thr), who was initially responsive to diazoxide therapy. After 11 months of diazoxide treatment, she developed intermittent, unpredictable breakthrough episodes of hypoglycaemia, in addition to generalized hypertrichosis and weight gain from enforced feeding to avoid hypoglycaemia. Sirolimus, which was commenced at 15 months of age, gradually replaced diazoxide, with significant reduction and abolition of hypoglycaemia. The hypertrichosis resolved and there was less weight gain given the reduced need for enforced feeding. Sirolimus, which was administered over the next 15 months, was well tolerated with no significant side effects and was gradually weaned off. After stopping sirolimus, apart from hypoglycaemia developing during an episode of severe viral gastroenteritis, the capillary glucose concentrations were maintained >3.5 mmol/L, even after a 10 h fast. Sirolimus may have a role in the treatment of partially diazoxide-responsive forms of HH who experience breakthrough hypoglycaemia, but the long-term safety and efficacy of sirolimus are not established.

Role of mTOR inhibitors for the control of viral infection in solid organ transplant recipients

Appropriate post-transplant immunosuppressive regimens that avoid acute rejection, while reducing risk of viral reactivation, have been sought, but remain a chimera. Recent evidence suggesting potential regulatory and antiviral effects of mammalian target of rapamycin inhibitors (mTORi) is of great interest. Although the concept of an immunosuppressive drug with antiviral properties is not new, little effort has been made to put the evidence together to assess the management of immunosuppressive therapy in the presence of a viral infection. This review was developed to gather the evidence on antiviral activity of the mTORi against the viruses that most commonly reactivate in adult solid organ recipients: cytomegalovirus (CMV), polyomavirus, Epstein-Barr virus (EBV), human herpesvirus 8 (HHV8), and hepatitis C virus (HCV). A rapid review methodology and evaluation of quality and consistency of evidence based on the GRADE system was used. The existing literature was variable in nature, although indicating a potential advantage of mTORi in CMV, polyomavirus, and HHV8 infection, and a most doubtful relation with EBV and HCV infection. Several recommendations about the management of these infections are presented that can change certain current patterns of immunosuppression and help to improve the prognosis of the direct and indirect effects of viral infection in solid organ recipients.

Surveillance biopsies after paediatric kidney transplantation: A review

Kidney transplantation is the most effective means of treating children with end-stage kidney disease, and yet, there continues to be a limited "life span" of transplanted kidneys in paediatric recipients. Early graft monitoring, using the surveillance biopsy, has the potential to extend renal allograft survival in paediatric recipients. The surveillance biopsy provides important and timely information about acute and chronic graft pathology, particularly SCR and calcineurin inhibitor-induced nephrotoxicity, which can subsequently guide management decisions and improve long-term graft survival. The ostensible value of the surveillance biopsy is furthered by the limitations of conventional renal functional studies. However, there is still much debate surrounding the surveillance biopsy in paediatric recipients, particularly in regard to its overall utility, safety and timing. This review discusses the current literature regarding the utility, safety, and potential predictive value of surveillance biopsies for guiding post-transplant management in paediatric renal allograft recipients, as well as the viability of other potentially newer non-invasive strategies for renal allograft monitoring.

Role of mTOR Inhibitors in Kidney Disease

The first compound that inhibited the mammalian target of rapamycin (mTOR), sirolimus (rapamycin) was discovered in the 1970s as a soil bacterium metabolite collected on Easter Island (Rapa Nui). Because sirolimus showed antiproliferative activity, researchers investigated its molecular target and identified the TOR1 and TOR2. The mTOR consists of mTOR complex 1 (mTORC1) and mTORC2. Rapalogues including sirolimus, everolimus, and temsirolimus exert their effect mainly on mTORC1, whereas their inhibitory effect on mTORC2 is mild. To obtain compounds with more potent antiproliferative effects, ATP-competitive inhibitors of mTOR targeting both mTORC1 and mTORC2 have been developed and tested in clinical trials as anticancer drugs. Currently, mTOR inhibitors are used as anticancer drugs against several solid tumors, and immunosuppressive agents for transplantation of various organs. This review discusses the role of mTOR inhibitors in renal disease with a particular focus on renal cancer, diabetic nephropathy, and kidney transplantation.

Metabolic consequences of modern immunosuppressive agents in solid organ transplantation

Among other factors, sophistication of immunosuppressive (IS) regimen accounts for the remarkable success attained in the short- and medium-term solid organ transplant (SOT) survival. The use of steroids, mycophenolate mofetil and calcineurin inhibitors (CNI) have led to annual renal graft survival rates exceeding 90% in the last six decades. On the other hand, attrition rates of the allograft beyond the first year have remained unchanged. In addition, there is a persistent high cardiovascular (CV) mortality rate among transplant recipients with functioning grafts. These shortcomings are in part due to the metabolic effects of steroids, CNI and sirolimus (SRL), all of which are implicated in hypertension, new onset diabetes after transplant (NODAT), and dyslipidemia. In a bid to reduce the required amount of harmful maintenance agents, T-cell-depleting antibodies are increasingly used for induction therapy. The downsides to their use are greater incidence of opportunistic viral infections and malignancy. On the other hand, inadequate immunosuppression causes recurrent rejection episodes and therefore early-onset chronic allograft dysfunction. In addition to the adverse metabolic effects of the steroid rescue needed in these settings, the generated proinflammatory milieu may promote accelerated atherosclerotic disorders, thus setting up a vicious cycle. The recent availability of newer agent, belatacept holds a promise in reducing the incidence of metabolic disorders and hopefully its long-term CV consequences. Although therapeutic drug monitoring as applied to CNI may be helpful, pharmacodynamic tools are needed to promote a customized selection of IS agents that offer the most benefit to an individual without jeopardizing the allograft survival.

Efficacy and safety of sirolimus in a neonate with persistent hypoglycaemia following near-total pancreatectomy for hyperinsulinaemic hypoglycaemia

Hyperinsulinaemic hypoglycaemia (HH) is characterised by inappropriate insulin secretion and is the most common cause for persistent neonatal hypoglycaemia. The only treatment available for medically unresponsive hypoglycaemia is a near-total pancreatectomy. A neonate with severe HH, due to a homozygous ABCC8 mutation, was not responsive to treatment with maximal doses of diazoxide and subcutaneous daily octreotide, and underwent a near-total pancreatectomy; however, hypoglycaemia persisted. Introduction of sirolimus, an mTOR (mammalian target of rapamycin) inhibitor, obviated the requirement for glucose infusion. Euglycaemia was achieved with no significant adverse events from the drug. Sirolimus therapy was ceased at 13 months of age. No episodes of persistent hypoglycaemia were observed after cessation of sirolimus. This report demonstrates the successful use of sirolimus for persistent hypoglycaemia in the critically ill infant post pancreatectomy. Sirolimus could be considered in patients with severe HH not responsive to conventional medical and surgical therapy. However, the long-term efficacy and safety with this immunosuppressive drug in very young patients are not assured.

Efficacy and Safety of an Everolimus- vs. a Mycophenolate Mofetil-Based Regimen in Pediatric Renal Transplant Recipients

Introduction

Data on the efficacy and safety of everolimus in pediatric renal transplantation compared to other immunosuppressive regimens are scarce.

Patients/Methods

We therefore performed a multicenter, observational, matched cohort study over 4 years post-transplant in 35 patients on everolimus plus low-dose cyclosporine, who were matched (1:2) with a control group of 70 children receiving a standard-dose calcineurin-inhibitor- and mycophenolate mofetil-based regimen.

Results

Corticosteroids were withdrawn in 83% in the everolimus vs. 39% in the control group (p<0.001). Patient and graft survival were comparable. The rate of biopsy-proven acute rejection episodes Banff score ≥ IA during the first year post-transplant was 6% in the everolimus vs. 13% in the control group (p = 0.23). The rate of de novo donor-specific HLA antibodies (11% in everolimus, 18% in controls) was comparable (p = 0.55). At 4 years post-transplant, mean eGFR in the everolimus group was 56±33 ml/min per 1.73 m² vs. 63±22 ml/min per 1.73 m² in the control group (p = 0.14). Everolimus therapy was associated with less BK polyomavirus replication (3% vs. 17% in controls; p = 0.04), but with a higher percentage of arterial hypertension and more hyperlipidemia (p<0.001).

Conclusion

In pediatric renal transplantation, an everolimus-based regimen with low-dose cyclosporine yields comparable four year results as a standard regimen, but with a different side effect profile.

Choosing the right dose of tacrolimus

Choosing the right dose of tacrolimus 'adapted to each individual patient' is a central question after transplantation. The pharmacokinetic behaviour of tacrolimus in paediatric patients is significantly influenced by clinical factors growth and maturation, as well as genetic factors. Large interindividual variability and narrow therapeutic index make dosage individualisation mandatory in children. CYP3A5 expressers require a 1.8-fold higher tacrolimus dose than non-expressers. A visual patient-tailored dosing chart, taking into consideration the child's weight, recent haematocrit level and CYP3A5 genotype, was developed based on a population pharmacokinetic-pharmacogenetic model, and can be used routinely to individualise tacrolimus starting dose. Area under the concentration-time curve-based dosage adaptation through limited sampling strategy and Bayesian estimation is more reliable than trough concentration. Therapeutic drug monitoring and dosage adaptation can be included in routine post-transplantation consultation and should be considered in the urgent situations (eg, rejection, adverse event, lack of compliance, change of coadministration drug with potential drug-drug interaction and other situations).

Recent developments in kidney transplantation in children

PURPOSE OF REVIEW

Renal transplantation in childhood is a well established procedure with excellent short-term outcomes. However, waiting times for transplantation are still relatively long if living donation cannot be performed, and long-term outcomes after transplantation have not significantly improved during the last decade.

RECENT FINDINGS

This review describes alternative modalities to improve donation rates such as en bloc kidney transplantation from young donors, ABO-incompatible transplantation and kidney paired donation. This review also deals with long-term post-transplant morbidities, such as follows: first, medication side-effects (metabolic syndrome, cardiovascular disease) and with the benefits of steroid and calcineurin inhibitor drug minimization; second, the deleterious impact of viral infections and their management and third, chronic antibody-mediated rejection, its therapeutic and prevention possibilities.

SUMMARY

Donor shortage and long-term morbidities, after transplantation, are still relevant issues in paediatric renal transplantation medicine. Significant research and efforts have been made to advance the field and create novel approaches for improvement of transplantation rates and post-transplant graft or patient survival. These modalities are to be established in the routine setting.