Conversion to Sirolimus in Pediatric Renal Transplantation Recipients

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.

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.

mTOR inhibitors in pediatric kidney transplantation

The mammalian target of the rapamycin (mTOR) inhibitors sirolimus and everolimus are increasingly being used in pediatric kidney transplantation in different combinations and doses. Several studies have shown beneficial effects of using mTOR inhibitors in children after pediatric renal transplantation. A switch to a low-dose calcineurin inhibitor (CNI) and mTOR inhibitor has been proven to stabilize the glomerular filtration rate. Additionally, de novo studies using a low-dose CNI and an mTOR inhibitor have shown good graft survival and a low number of rejections. Side effects of mTOR inhibitors, such as hyperlipidemia, wound healing problems, and proteinuria, mainly occur if high doses are given and if treatment is not combined with a CNI. Lower doses of mTOR inhibitors do not result in growth impairment or reduced testosterone levels. Treatment with mTOR inhibitors is also associated with a lower number of viral infections, especially cytomegalovirus. Due to their antiproliferative effect, mTOR inhibitors could theoretically reduce the risk of post-transplant lymphoproliferative disease. mTOR inhibitors, especially in combination with low-dose CNIs, can safely be used in children after kidney transplantation as de novo therapy or for conversion from CNI- and mycophenolate mofetil-based regimens.

Growing experience with mTOR inhibitors in pediatric solid organ transplantation

Controlled trials of mTOR inhibitors in children following solid organ transplantation are scarce, although evidence from prospective single-arm studies is growing. Everolimus with reduced CNI therapy has been shown to be efficacious and safe in de novo pediatric kidney transplant patients in prospective trials. Prospective and retrospective data in children converted from CNI therapy to mTOR inhibition following kidney, liver, or heart transplantation suggest preservation of immunosuppressive efficacy. Good renal function has been maintained when mTOR inhibitors are used de novo in children following kidney transplantation or after conversion to mTOR inhibition with CNI minimization. mTOR inhibition with reduced CNI exposure is associated with a low risk for developing infection in children. Growth and development do not appear to be impaired during low-dose mTOR inhibition, but more studies are required. No firm conclusions can be drawn as to whether mTOR inhibitors should be discontinued in children requiring surgical intervention or whether mTOR inhibition delays progression of hepatic fibrosis after pediatric liver transplantation. In conclusion, current evidence suggests that use of mTOR inhibitors in children undergoing solid organ transplantation is efficacious and safe, but a number of issues remain unresolved and further studies are required.

The importance of different immunosuppressive regimens in the development of posttransplant diabetes mellitus

Solid-organ transplantation is the optimal long-term treatment for most patients with end-stage organ failure. After solid-organ transplantation, short-term graft survival significantly improved (1). However, due to chronic allograft nephropathy and death with functioning graft, long-term survival has not prolonged remarkably (2). Posttransplant immunosuppressive medications consist of one of the calcineurin inhibitors in combination with mycophenolate mofetil (MMF) or azathioprine (Aza) and steroids. All of them have different adverse effects, among which posttransplant diabetes mellitus (PTDM) is an independent risk factor for cardiovascular (CV) events and infections causing the death of many transplant patients and it may directly contribute to graft failure (3). According to the criteria of the American Diabetes Association (4), diabetes mellitus (DM) is defined by symptoms of diabetes (polyuria and polydipsia and weight loss) plus casual plasma glucose concentration ≥ 11.1 mmol/L or fasting plasma glucose (FPG) ≥ 7.0 mmol/L or 2-h plasma glucose level ≥ 11.1 mmol/L following oral glucose tolerance test (OGTT). This metabolic disorder occurring as a complication of organ transplantation has been recognized for many years. PTDM, which is a combination of decreased insulin secretion and increased insulin resistance, develops in 4.9/15.9% of liver transplant patients, in 4.7/11.5% of kidney recipients, and in 15/17.5% of heart and lung transplants [cyclosporine A (CyA)/tacrolimus (Tac)-based regimen, respectively] (5). Risk factors of PTDM can be divided into non-modifiable and modifiable ones (6), among which the most prominent is the immunosuppressive therapy being responsible for 74% of PTDM development (7). Emphasizing the importance of the PTDM, numerous studies have determined the long-term outcome. On the basis of these studies, graft and patient survival is tendentiously (8) or significantly (9, 10) decreased for those developing PTDM.

Renal function in children with heart transplantation after switching to CNI-free immunosuppression with everolimus

Renal impairment because of CNI contributes to long-term morbidity. Therefore, CNI avoiding or sparing treatment strategies are important. In this article, we describe the results of a CNI-free treatment protocol with regard to recovery of renal function. Twenty-eight patients with heart transplantation were switched from CNI regimen to everolimus and mycophenolate, when cGFR was <75 mL/min/1.73 m(2). In all patients, CNI was stopped, when everolimus trough levels of 5-8 ng/L were achieved. Serum creatinine and cGFR were determined before and after 6 and 12 months. Median serum creatinine decreased from 1.2 mg/dL (range 0.7-3.7) before everolimus to 1.0 (range 0.6-1.8) and 1.0 (range 0.5-1.9) mg/dL after 6 and 12 months. Median cGFR was 47.81 (range 18.3-72.6) mL/min/1.73 m(2) before everolimus and 63.1 (range 37.8-108.7) mL/min/1.73 m(2) at six months and 64.8 (range 37.7-106.6) mL/min/1.73 m(2) after 12 months. All changes from baseline to six and 12 months were statistically significant (p < 0.05). Adverse events were infections (n = 3) and rejections (n = 3). Therapy was discontinued in four patients. Conversion to CNI-free immunosuppression resulted in significant improvements of renal function within six months of CNI withdrawal. Side effects are common. However, more studies are required to demonstrate the effectiveness in children.

Sirolimus in pediatric renal transplantation

SRL, an mTOR inhibitor that inhibits cell cycle progression, represents an important alternative to CNIs, which are still the cornerstones of pediatric solid organ tx. Because there are still limited data on SRL use among pediatric solid organ recipients, further studies are needed to verify the efficacy and safety of SRL. It has unique pharmacokinetic characteristics concerning dosing intervals and reduction of the dose in combination with other immunosuppressants. SRL also has antineoplastic, antiviral, and antiatherogenic advantages over other immunosuppressive agents. The adverse effects of SRL including thrombocytopenia, hyperlipidemia, proteinuria, impaired wound healing, mouth ulcers, edema, male hypogonadism, TMA, and interstitial pneumonitis must be considered carefully in pediatric population. This article reviews the most recent data on SRL application in the field of pediatric renal tx.

Growth failure associated with sirolimus: case report

An 11-year-old girl, who was a renal transplant recipient, developed linear growth failure associated in time with sirolimus (SRL) treatment. After 5 years of functional graft [creatinine clearance (CCr) 90 ml/min per 1.73 m(2) body surface area], she developed acute renal failure due to calcineurin inhibitor-related hemolytic uremic syndrome, and cyclosporine A was replaced by SRL. Before the drug change, she had been growing normally (5.5 cm/year) and had reached the 33.9 percentile (P) of height (z-height -0.41), similar to her target. Two years later, her height had decreased to P 6th (z-height -1.54), as her growth velocity had diminished to 2.2 cm/year, despite optimal renal function (CCr 68 ml/min per 1.73 m(2)). Human recombinant growth hormone was needed to promote her catch-up growth and achieve the P 49th of height (z-height -0.03). SRL may have deleterious effects on growing children due its characteristic anti-proliferative and anti-angiogenic properties. Pediatric transplant recipients' linear growth should be cautiously monitored while they are being given SRL.

Patient selection critical for calcineurin inhibitor withdrawal in pediatric kidney transplantation

CNI withdrawal may be employed as a "rescue" strategy for patients with established renal allograft injury and/or declining allograft function, with the aim at eliminating CNI-associated nephrotoxic effects. This analysis reviews outcomes in a pediatric population and identifies risk factors for adverse events post-CNI withdrawal. We performed a retrospective analysis of 17 pediatric renal transplants who underwent CNI withdrawal, with conversion to sirolimus and MMF. Mean CrCl decreased from 64.3 +/- 22 to 59.38 +/- 28.6 mL/min/1.73 m(2) (p = 0.04) at six months and 57.46 +/- 31.1 mL/min/1.73 m(2) (p = 0.02) at 12 months post-withdrawal. Forty-one percent of patients experienced AR. Increased risk for AR was associated with prior AR history, lower sirolimus trough levels, and lower CNIT biopsy scores. Graft loss (24%) was associated with worse CrCl, proteinuria, and histologic chronicity. Proteinuria (spot protein/creatinine ratio) increased from 0.75 +/- 1.0 to 1.71 +/- 2.0 (p = 0.03), unrelated to de novo sirolimus use. Four patients returned to CNI-based immunosuppression due to AR (n = 3) and gastrointestinal side effects (n = 1). Careful selection of pediatric candidates for CNI withdrawal is recommended. Worsening graft function and graft loss may be minimized by selecting patients with high CNIT scores and low biopsy chronicity and excluding patients with prior AR history.