Improved gastrointestinal symptom burden after conversion from mycophenolate mofetil to enteric-coated mycophenolate sodium in kidney transplanted children

Pharmacomicrobiomics: Immunosuppressive Drugs and Microbiome Interactions in Transplantation

The human microbiome is associated with human health and disease. Exogenous compounds, including pharmaceutical products, are also known to be affected by the microbiome, and this discovery has led to the field of pharmacomicobiomics. The microbiome can also alter drug pharmacokinetics and pharmacodynamics, possibly resulting in side effects, toxicities, and unanticipated disease response. Microbiome-mediated effects are referred to as drug-microbiome interactions (DMI). Rapid advances in the field of pharmacomicrobiomics have been driven by the availability of efficient bacterial genome sequencing methods and new computational and bioinformatics tools. The success of fecal microbiota transplantation for recurrent Clostridioides difficile has fueled enthusiasm and research in the field. This review focuses on the pharmacomicrobiome in transplantation. Alterations in the microbiome in transplant recipients are well documented, largely because of prophylactic antibiotic use, and the potential for DMI is high. There is evidence that the gut microbiome may alter the pharmacokinetic disposition of tacrolimus and result in microbiome-specific tacrolimus metabolites. The gut microbiome also impacts the enterohepatic recirculation of mycophenolate, resulting in substantial changes in pharmacokinetic disposition and systemic exposure. The mechanisms of these DMI and the specific bacteria or communities of bacteria are under investigation. There are little or no human DMI data for cyclosporine A, corticosteroids, and sirolimus. The available evidence in transplantation is limited and driven by small studies of heterogeneous designs. Larger clinical studies are needed, but the potential for future clinical application of the pharmacomicrobiome in avoiding poor outcomes is high.

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.

Considerations and controversies of pharmacologic management of the pediatric kidney transplant recipient

Pediatric kidney transplantation has experienced considerable growth and improvement in patient and allograft outcomes over the past 20 years, in part due to advancements in immunosuppressive regimens and management. Despite this progress, care for this unique population can be challenging due to limited pediatric transplant data and trials, intricacies related to differences in children and adolescents compared with their adult counterparts, and limitations to long-term survival facing all solid organ transplant populations. Immunosuppression and infection prevention practices vary from one pediatric transplant center to another and clinical controversies exist surrounding treatment and dosing. This review aims to summarize key aspects of pharmacologic management in this population and present pertinent data that describe the influence of practice to serve as a resource for practitioners caring for this unique specialty patient population. Additionally, this review highlights select controversies that exist within pediatric kidney transplantation.

Is Conversion from Mycophenolate Mofetil to Enteric-Coated Mycophenolate Sodium Justifiable for Gastrointestinal Quality of Life?

BACKGROUND

Globally, enteric-coated mycophenolate sodium (EC-MPS) is replacing mycophenolate mofetil (MMF) in maintenance immunosuppressant regimens. The predominant reason for conversion is the purported improvement in gastrointestinal (GI) quality of life. This paper considers the level of bias associated with studies comparing EC-MPS and MMF for GI-related improvement and provides insight into whether conversion is supported by evidence.

METHODS

Using a pre-determined protocol, a literature search was conducted. Full-text review, data extraction and risk of bias analysis was conducted by two independent authors using the Cochrane domain-based evaluation of risk of bias. The review was reported according to the preferred reporting items for systematic reviews and meta-analyses.

RESULTS

Twenty-nine studies were included in risk of bias analysis. Of these, only three were deemed a low risk of bias. Across these three studies, there were no statistically significant differences in the proportion of GI-related adverse events nor was there a significant difference in the GI-related quality of life between EC-MPS- and MMF-treated patients in these data.

CONCLUSION

There was a high risk of bias across the 29 studies investigating conversion from MMF to EC-MPS for potential improvement in GI-related quality of life. The consolidated results of the three studies with low risk of bias suggest no evidence to convert patients stabilised on MMF. If a patient experiences GI-related adverse events whilst taking MMF, other methods should be explored before conversion to EC-MPS.

Adverse Events under Tacrolimus and Cyclosporine in the First 3 Years Post-Renal Transplantation in Children

BACKGROUND

Progress in immunosuppression has reduced acute rejection, graft loss and mortality after renal transplantation. Adverse drug reactions are well described in adults but few data are available in children. Our objectives were to analyse the adverse events reported in the first 3 years post-transplantation in children receiving tacrolimus or cyclosporine-based immunosuppression and compare them with the information of the Summary of Product Characteristics.

METHODS

This retrospective study included all children who underwent a renal transplant at Hospital Robert Debré between 2002 and 2015. Initial immunosuppression was based on induction, calcineurin inhibitor, mycophenolate mofetil and corticosteroids. Adverse events were collected from medical records and coded using the Medical Dictionary for Regulatory Activities and the implications of tacrolimus and cyclosporine analysed. Statistical analyses were performed using SAS 9.4.

RESULTS

One hundred and twenty-five children were included. During the observation period [2.7 years (0.6-4.3)], 105 patients received tacrolimus and 39 received cyclosporine. The incidence rate for gastrointestinal disorders was 0.128 and 0.056 by patient-years of exposure (p < 0.05), under tacrolimus and cyclosporine schedules. For neutropenia, it was 0.064 and 0.014 (p < 0.05). The frequencies of toxic nephropathy and gastrointestinal pain were higher than those in the Summary of Product Characteristics of tacrolimus (> 20%) and cyclosporine (> 10%). Cosmetic events for cyclosporine and neutropenia for tacrolimus were frequently observed (18 and 14.3%, respectively), although uncommon in the Summary of Product Characteristics.

CONCLUSIONS

The exposure-adjusted incidence rate of gastrointestinal disorders and neutropenia was higher in children under the tacrolimus schedule. Our findings contribute to the evaluation of the benefit-risk balance of immunosuppressive therapy following paediatric renal transplantation.

Therapeutic drug monitoring in pediatric renal transplantation

Finding the balance between clinical efficacy and toxicity of immunosuppressive drugs is a challenge in renal transplantation (RTx), but especially in pediatric RTx patients. Due to the expected longer life-span of pediatric transplant patients and the long-term consequences of drug-induced infectious, malignant and cardiovascular adverse effects, protocols which minimize immunosuppressive therapy make conceptual sense. In this context, therapeutic drug monitoring is a tool which provides support for the individualization of therapy. It has, however, limitations, and specific data in the pediatric cohort are comparatively sparse. There is large heterogeneity among the studies conducted to date in terms of methods, follow-up, endpoints, immunosuppressive regimens and patients. In addition, data from adult studies are not readily transferrable to the pediatric situation. This educational review gives a concise overview on aspects of therapeutic drug monitoring in pediatric RTx.

Pharmacology and toxicology of mycophenolate in organ transplant recipients: an update

This review aims to provide an update of the literature on the pharmacology and toxicology of mycophenolate in solid organ transplant recipients. Mycophenolate is now the antimetabolite of choice in immunosuppressant regimens in transplant recipients. The active drug moiety mycophenolic acid (MPA) is available as an ester pro-drug and an enteric-coated sodium salt. MPA is a competitive, selective and reversible inhibitor of inosine-5'-monophosphate dehydrogenase (IMPDH), an important rate-limiting enzyme in purine synthesis. MPA suppresses T and B lymphocyte proliferation; it also decreases expression of glycoproteins and adhesion molecules responsible for recruiting monocytes and lymphocytes to sites of inflammation and graft rejection; and may destroy activated lymphocytes by induction of a necrotic signal. Improved long-term allograft survival has been demonstrated for MPA and may be due to inhibition of monocyte chemoattractant protein 1 or fibroblast proliferation. Recent research also suggested a differential effect of mycophenolate on the regulatory T cell/helper T cell balance which could potentially encourage immune tolerance. Lower exposure to calcineurin inhibitors (renal sparing) appears to be possible with concomitant use of MPA in renal transplant recipients without undue risk of rejection. MPA displays large between- and within-subject pharmacokinetic variability. At least three studies have now reported that MPA exhibits nonlinear pharmacokinetics, with bioavailability decreasing significantly with increasing doses, perhaps due to saturable absorption processes or saturable enterohepatic recirculation. The role of therapeutic drug monitoring (TDM) is still controversial and the ability of routine MPA TDM to improve long-term graft survival and patient outcomes is largely unknown. MPA monitoring may be more important in high-immunological recipients, those on calcineurin-inhibitor-sparing regimens and in whom unexpected rejection or infections have occurred. The majority of pharmacodynamic data on MPA has been obtained in patients receiving MMF therapy in the first year after kidney transplantation. Low MPA area under the concentration time from 0 to 12 h post-dose (AUC0-12) is associated with increased incidence of biopsy-proven acute rejection although AUC0-12 optimal cut-off values vary across study populations. IMPDH monitoring to identify individuals at increased risk of rejection shows some promise but is still in the experimental stage. A relationship between MPA exposure and adverse events was identified in some but not all studies. Genetic variants within genes involved in MPA metabolism (UGT1A9, UGT1A8, UGT2B7), cellular transportation (SLCOB1, SLCO1B3, ABCC2) and targets (IMPDH) have been reported to effect MPA pharmacokinetics and/or response in some studies; however, larger studies across different ethnic groups that take into account genetic linkage and drug interactions that can alter a patient's phenotype are needed before any clinical recommendations based on patient genotype can be formulated. There is little data on the pharmacology and toxicology of MPA in older and paediatric transplant recipients.

Paediatric use of mycophenolate mofetil

A number of medications do not have a licence, or label, for use in the paediatric age group nor for the specific indication for which they are being used in children. Over recent years, mycophenolate mofetil has increasingly been used off-label (i.e. off-licence) in adults for a number of indications, including autoimmune conditions; progressively, this wider use has been extended to children. This review summarizes current use of mycophenolate mofetil (MMF) in children, looking at how MMF works, the pharmacokinetics, the clinical conditions for which it is used, the advantages it has when compared with other immunosuppressants and the unresolved issues remaining with use in children. The review aims to focus on off-label use in children so as to identify areas that require further research and investigation. The overall commercial value of MMF is limited because it has now come off patent in adults. Given the increasing knowledge of the pharmacodynamics, pharmacokinetics and pharmacogenomics demonstrating the clinical benefits of MMF, new, formal, investigator-led studies, including trials focusing on the use of MMF in children, would be of immense value.

Enteric-coated mycophenolate sodium in de novo and maintenance kidney-pancreas transplant recipients

BACKGROUND

Our objective was to describe efficacy and safety of enteric-coated mycophenolate sodium (EC-MPS) in de novo and maintenance recipients of kidney-pancreas transplant in the clinical practice.

METHODS

Observational, multicentre, prospective, 12-month study.

RESULTS

We included 24 de novo and 24 maintenance patients. EC-MPS mean (± SD) doses at initiation in de novo patients were 1440 ± 0 vs. 1268 ± 263 mg/d at month 12 (M12). Patient and renal graft survival at one yr were 100%, and pancreatic graft survival was 83.3% (two losses owing to technical failure and two owing to rejection). In the maintenance cohort, EC-MPS was introduced at a median (P25-P75) of 30 (6-71) months after transplant. Baseline doses were 585 ± 310 vs. 704 ± 243 mg/d at M12. In this group, a significant increase in creatinine clearance was observed (65 ± 22 at baseline vs. 74 ± 20 mL/min at M12, p = 0.011). Patient, renal, and pancreatic graft survival were 100%, 95.8%, and 100%, respectively (one kidney graft loss owing to rejection). During follow-up, one patient from each group discontinued EC-MPS.

CONCLUSIONS

The efficacy of EC-MPS in the clinical practice of kidney-pancreas transplantation is good, with high patient and grafts survival at 12 months, and good safety profile. The maintenance group displayed an improvement in renal function.

Tolerance of enteric-coated mycophenolate sodium in combination with calcineurin inhibitor in kidney transplant recipients: Polish experience

INTRODUCTION

Enteric-coated mycophenolate sodium (EC-MPS) was developed to reduce the incidence of gastrointestinal adverse effects. This multicenter observational study was designed to evaluate the safety profile and drug tolerance in kidney transplant recipients.

METHODS

Three hundred adult kidney recipients (median age 48 years) were enrolled over 3 years to receive EC-MPS de novo (n=175), as a switch from azathioprine (n=62) or mycophenolate mofetil MMF (n=63); in combination with calcineurin inhibitor. Drug doses, serum creatinine, estimated glomerular filtration rate (eGFR), as well as drug tolerance, patient and physician evaluation of therapy (on a 4-point scale) were recorded at enrollment and followed over 28 weeks. We modeled the probability of the highest level (ie, best result) of the categorical outcome variable.

RESULTS

Two hundred seventy-three patients completed the study (91%). In the pooled study group (1) best drug tolerance was expected more frequently with tacrolimus versus cyclosporine (odds ratio [OR] 2.12, P<.05); (2) best physician evaluation, with earlier EC-MPS introduction (OR for 4-week delay: 0.99, P<.03) and higher eGFR (OR for 5 mL/min increase: 1.21, P<.01). Among the EC-MPS de novo administrations group: (1) best drug tolerance was expected more frequently with coadministered tacrolimus versus cyclosporine (OR 3.14, P<.02); (2) best patient evaluation, with higher eGFR (OR for 1 mL/min increase: 1.04, P<.04); and (3) best physician evaluation, with higher eGFR (OR for 1 mL/min increase: 1.04, P<.001) and earlier EC-MPS introduction (OR for 4-week delay: 0.99, P<.03). In the conversion from MMF to EC-MPS group: (1) best drug tolerance was expected less frequently with coadministered cyclosporine versus tacrolimus (OR 0.05, P<.04) and more frequently with younger recipients (OR .001, P<.04); (2) best physician evaluation was expected more frequently with lower EC-MPS dose (OR for 360-mg dose increase: 0.4, P<.01) and with higher eGFR (OR for 5 mL/min increase: 1.42, P<.002). Adverse events were reported among 49/300 patients (16 serious adverse events).

CONCLUSIONS

EC-MPS was tolerated better by younger kidney recipients, when combined with tacrolimus versus cyclosporine, and when introduced earlier after transplantation. EC-MPS tolerance decreased gradually with renal function deterioration.

Pediatric aspects of therapeutic drug monitoring of mycophenolic acid in renal transplantation

Mycophenolate mofetil (MMF) is widely used for maintenance immunosuppressive therapy in pediatric renal and heart transplant recipients. Children undergo developmental changes (ontogeny) of drug disposition, which may affect drug metabolism of the active compound mycophenolic acid (MPA). Therefore, a detailed characterization of MPA pharmacokinetics and pharmacodynamics in this patient population is required. In general, the overall efficacy and tolerability of MMF in pediatric patients appear to be comparable with those in adults, except for a higher prevalence of gastrointestinal adverse effects in children younger than 6 years. The currently recommended dose in pediatric patients with concomitant cyclosporine is 1200 mg/m(2) per day in 2 divided doses; the recommended MMF dose with concomitant tacrolimus or without a concurrent calcineurin inhibitor is 900 mg/m(2) per day in 2 divided doses. Recent data suggest that fixed MMF dosing results in MPA underexposure (MPA-area under the concentration-time curve (AUC(0-12)), <30 mg × h/L) early posttransplant in approximately 60% of patients. To achieve adequate MPA exposure in most patients, an initial MMF dose of 1800 mg/m(2) per day with concomitant cyclosporine and 1200 mg/m(2) per day with concomitant tacrolimus for the first 2 to 4 weeks posttransplant has been suggested. As in adults, there is an approximately 10-fold variability in dose-normalized MPA-AUC(0-12) values between pediatric patients after renal transplantation, strengthening the argument for concentration-controlled dosing of the drug. Although the clinical utility of therapeutic drug monitoring of MPA for graft outcome and patient survival is still controversial, potential indications are the avoidance of underimmunosuppression, particularly in patients with high immunologic risk in the initial period posttransplant, in patients who are treated with protocols that explore the possibilities of calcineurin inhibitor minimization, withdrawal or even complete avoidance, and steroid withdrawal or avoidance regimens that might also benefit from intensified therapeutic drug monitoring of MPA. An additional indication especially in adolescent patients is the monitoring of drug adherence. Therapeutic drug monitoring of MPA in pediatric solid organ transplantation using limited sampling strategies is preferable over drug dosing based on trough level monitoring only. Several validated pediatric limited sampling strategies are available. Clearly, more research is required to determine whether pediatric patients will benefit from therapeutic drug monitoring of MPA for long-term maintenance immunosuppression with MMF.

Efficacy and safety of conversion of mycophenolate mofetil to enteric-coated mycophenolate sodium in Mexican renal transplant children

The aim of the study was to evaluate the efficacy and safety of the conversion of MMF to EC-MPS in pediatric renal transplant recipients. We included 12 patients with stable graft function who were receiving MMF treatment. In the first visit, a complete medical examination was performed, which included a GSRS, a nine-point pharmacokinetic profile, samples for renal, liver and hematological tests and evaluation of IMPDH2 gene expression. The patients were transferred to an equimolar dose of EC-MPS. Two wk later, a clinical evaluation and blood collection, as in the first visit were performed. There was no change in serum creatinine, leukocyte count, serum albumin, or transaminase levels, but we found a statistically significant reduction of hemoglobin after conversion (13.2 +/- 1.6 g/dL with MMF vs. 12.5 +/- 1.3 g/dL when receiving EC-MPS). The GSRS total mean score was 16 +/- 12 with MMF vs. 8 +/- 5 with EC-MPA (p < 0.05). There was no statistically significant difference between formulations in the gene expression of IMPDH 2, in the AUC(0-12h) or in C(max). However, peak concentration occurred later with EC-MPS.

Safety and tolerance of sodium mycophenolate in patients after renal transplantation--an observational study

BACKGROUND

Enteric-coated mycophenolate sodium (EC-MPS) was developed as an alternative agent to mycophenolate mofetil (MMF), aimed at reduction of gastrointestinal (GI) complications.

METHODS

Seventy-four patients (mean age 42.3 years) switched from MMF to MPS were included in the study and followed-up for 3 months (Visit 0, Visit 2 after 1 month and Visit 3 after 3 months). The mean time from transplantation to switch was 3.7 years. During Visit 2 and 3 the following were recorded: impact of treatment change on the severity of GI symptoms (4 point scale: 1-worsening, 2-no change, 3-improvement, 4-resolution), EC-MPS tolerance, adverse events (AEs), patient compliance and physician satisfaction with treatment (4 point scale: 1-bad, 2-fair, 3-good, 4-very good).

RESULTS

Sixty-three patients completed the study (85.1%). EC-MPS dose ranged from 720 to 1440 mg. GI symptom severity score averaged at 3.41. Symptoms most commonly compelling a conversion were: abdominal pain, diarrhea, abdominal colic, nausea, anorexia and vomiting. Out of 175 complaints, 144 (82%) either improved or resolved, 5 (2.86%) aggravated, and 25 (14.86%) persisted. Patient compliance and mean physician satisfaction score averaged at 3.70 and 3.02 at Visit 3, respectively. 9 AEs (2 severe) were reported. Causal relationship with the medication was suspected in 5 cases (1 case of SAE). The most common AEs were: anemia, infection (including sepsis), GI symptoms (abdominal pain, diarrhea).

CONCLUSIONS

The following was concluded in our study: (1) sodium mycophenolate is well tolerated; (2) after switching from MMF to EC-MPS, gastrointestinal symptoms alleviated; (3) EC-MPS is a safe medication, with a low adverse events rate.

Conversion from mycophenolate mofetil to delayed formulation in pediatric renal transplantation: higher mycophenolic acid predose level but no changes in the immune biomarkers

EC-MPS was designed to improve MPA-related GII because of MMF, by delaying the release of MPA until reaching the small intestine. At present, its immunosuppressive activity in pediatric renal transplant recipients with GII has not been clarified. We studied eight renal transplant recipients before and after three months of the conversion from MMF to equimolar doses of EC-MPS. After three months of treatment with EC-MPA, GII decreased between 100% and 12.5%. The predose levels of MPA were about 60% higher on EC-MPS (6.9 +/- 1.1 microg/mL) compared with MMF administration (4.2 +/- 0.9 microg/mL). Hemoglobin decreased significantly post-conversion (12.0 +/- 0.4 to 11.0 +/- 0.5 g/dL). Serum creatinine, creatinine clearance, and urinary protein excretion did not change. Also, proliferative response and cytotoxic antibodies showed no significant change. The release of interleukin-10 was strikingly augmented with MMF or EC-MPS therapy; meanwhile, gamma-interferon and TNF were low under both treatments. Our data indicate that conversion from MMF to EC-MPS leads to an improvement in GII without altering key elements of immunosuppression.