Randomized crossover study to assess the inter- and intrasubject variability of morning mycophenolic acid concentrations from enteric-coated mycophenolate sodium and mycophenolate mofetil in stable renal transplant recipients

Pharmacokinetics and pharmacodynamics profiles of enteric-coated mycophenolate sodium in female patients with difficult-to-treat lupus nephritis

Relapsed or resistant lupus nephritis (LN) is considered a difficult-to-treat type of LN, and enteric-coated mycophenolate sodium (EC-MPS) has been used in this condition. Therapeutic drug monitoring using the area under the plasma mycophenolic acid concentration from 0 to 12 h postdose (MPA-AUC_0-12h ) ≥45 μg.h/ml is a useful approach to achieve the highest efficiency. This study assessed EC-MPS's pharmacokinetic (PK) and pharmacodynamic (PD) profiles and investigated an optimal level of the single time point of plasma MPA concentration. Nineteen biopsy-proven patients with class III/IV LN received 1440 mg/day of EC-MPS for 24 weeks. PK (maximum plasma MPA concentration [C_max ], time to C_max , and MPA-AUC_0-12h ) and PD (activity of inosine-5'-monophosphate dehydrogenase [IMPDH]) parameters were measured at weeks 2, 8, 16, and 24. We found that IMPDH activity decreased from baseline by 31-42% within 2-4 h after dosing, coinciding with the increased plasma MPA concentration. MPA-AUC_0-12h ≥45 μg.h/ml was best predicted by a single time point MPA concentration at C0.5, C2, C3, C4, and C8 (r²  = 0.516, 0.514, 0.540, 0.611, and 0.719, respectively), independent of dose, albumin, urine protein/creatinine ratio, and urinalysis. The MPA-C0.5 cutoff of 2.03 g/ml yielded the highest overall sensitivity of 85% and specificity of 88.2% in predicting MPA-AUC_0-12h ≥45 μg.h/ml. A single timepoint of plasma MPA-C0.5 ≥2.03 μg/ml may help guide EC-MPS adjustment to achieve adequate drug exposure. Further study of EC-MPS used to validate this cutoff is warranted.

Premature senescence of placental decidua cells as a possible cause of miscarriage produced by mycophenolic acid

BACKGROUND

Successful pregnancy is supported by a healthy maternal-fetal interface (i.e., the decidual tissues) which holds the conceptus and safeguards it against stressors from the beginning of pregnancy. Any disturbance of this interface can presumably lead to the loss of pregnancy. The use of the immunosuppressive drug mycophenolic acid (MPA) should be discontinued in pregnancy given its abortive and embryotoxic effects. Direct teratogenic effects have been observed in mammalian embryos cultured in MPA, but the underlying mechanisms of abortion by MPA are less understood.

METHODS

Decidual stromal cells isolated from human placentas are cultured in the presence of clinically relevant doses of MPA. Data regarding the effects of MPA on the proliferation and viability of decidua cultures are first analysed and then, molecular pathways contributing to these effects are unravelled.

RESULTS

MPA treatment of decidual stromal cells results in loss of proliferation capacity and a decrease in the viability of decidua cultures. The molecular pathways involved in the effects of MPA on decidual stromal cells are a reduction in pre-rRNA synthesis and subsequent disruption of the nucleolus. The nucleolar stress stabilizes p53, which in turn, leads to a p21-mediated cell cycle arrest in late S and G2 phases, preventing the progression of the decidua cells into the mitosis. Furthermore, MPA does not induce apoptosis but activate mechanisms of autophagy and senescence in decidual stromal cells.

CONCLUSION

The irreversible growth arrest of decidua cells, whose role in the maintenance of the pregnancy microenvironment is known, may be one cause of miscarriage in MPA treated pregnant women.

Impact of switching from mycophenolate mofetil to enteric-coated mycophenolate sodium on gastrointestinal side effects in patients with autoimmune disease: a Phase III, open-label, single-arm, multicenter study

BACKGROUND

The purpose of this study was to assess changes in gastrointestinal symptom severity in patients with autoimmune disease who were switched from mycophenolate mofetil to enteric-coated mycophenolate sodium (EC-MPS).

METHODS

In this national, explorative, single-arm study, 111 patients were enrolled and switched to equimolar EC-MPS at baseline. The primary endpoint was change in the Gastrointestinal Symptom Rating Scale (GSRS) total score after 6-8 weeks of treatment (Visit 2). The optional follow-up visit was 6-12 weeks after completion of the study (Visit 2). Secondary endpoints were changes in GSRS subscale score; changes in gastrointestinal-related quality of life measured by the Gastrointestinal Quality of Life Index (GIQLI); and general health-related quality of life (HRQoL) measured by Psychological General Well-Being Index and assessment of overall treatment effect (OTE). Change was evaluated by paired t-tests.

RESULTS

At Visit 2, the mean ± standard deviation GSRS total score improved from 2.28±1.13 to 2.02±0.93 points. The change (-0.28±0.92 points, P=0.002) was statistically significant. The change at the follow-up visit (-0.36±0.94 points, P=0.001) was statistically significant and more than the minimal clinical important difference. GSRS subscores showed statistically significant and clinically relevant improvement for abdominal pain (-0.51±1.2 points, P<0.001) and indigestion (-0.42±1.33 points, P=0.002). Overall GIQLI score showed significant improvement from baseline to Visit 2 (-5.8±18.6 points, P=0.002). Per OTE, improvement was reported in 44.1% and 34.2% patients as rated by physicians and patients, respectively. The majority of patients (55%) reported OTE-HRQoL as unchanged. Diarrhea and nausea were the commonly reported adverse events.

CONCLUSION

Patients switched to EC-MPS experienced less gastrointestinal symptom burden and showed improvement in HRQoL.

No relevant pharmacokinetic interaction between pantoprazole and mycophenolate in renal transplant patients: a randomized crossover study

AIMS

Mycophenolic acid (MPA) suppresses lymphocyte proliferation through inosine monophosphate dehydrogenase (IMPDH) inhibition. Two formulations have been approved: mycophenolate mofetil (MMF) and enteric-coated mycophenolate sodium (EC-MPS). Pantoprazole (PAN) inhibits gastric acid secretion, which may alter MPA exposure. Data from healthy volunteers suggest a significant drug-drug interaction (DDA) between pantoprazole and MPA. In transplant patients, a decreased MPA area under the concentration-time curve (AUC) may lead to higher IMPDH activity, which may lead to higher acute rejection risk. Therefore this DDA was evaluated in renal transplant patients under maintenance immunosuppressive therapy.

METHODS

In this single-centre, open, randomized, four-sequence, four-treatment crossover study, the influence of PAN 40 mg on MPA pharmacokinetics such as (dose-adjusted) AUC0-12 h (dAUC) was analysed in 20 renal transplant patients (>6 months post-transplantation) receiving MMF (1-2 g day(-1) ) and EC-MPS in combination with ciclosporin. The major metabolite MPA glucuronide (MPAG) and the IMPDH activity were also examined.

RESULTS

MMF + PAN intake led to a lowest mean dAUC for MPA of 41.46 ng h ml(-1) mg(-1) [95% confidence interval (CI) 32.38, 50.54], while MPA exposure was highest for EC-MPS + PAN [dAUC: 46.30 ng h ml(-1) mg(-1) (95% CI 37.11, 55.49)]. Differences in dAUC and dose-adjusted maximum concentration (dCmax) were not significant. Only for MMF [dAUC: 41.46 ng h ml(-1) mg(-1) (95% CI 32.38, 50.54)] and EC-MPS [dAUC: 43.39 ng h ml(-1) mg(-1) (95% CI 33.44, 53.34)] bioequivalence was established for dAUC [geometric mean ratio: 101.25% (90% CI 84.60, 121.17)]. Simultaneous EC-MPS + PAN intake led to an earlier time to Cmax (tmax) [median: 2.0 h (min-max: 0.5-10.0)] than EC-MPS intake alone [3 h (1.5-12.0); P = 0.037]. Tmax was not affected for MMF [1.0 h (0.5-5.0)] ± pantoprazole [1.0 h (0.5-6.0), P = 0.928). No impact on MPAG pharmacokinetics or IMPDH activity was found.

CONCLUSION

Pantoprazole influences EC-MPS and MMF pharmacokinetics but as it had no impact on MPA pharmacodynamics, the immunosuppressive effect of the drug was not impaired.

How accurate and precise are limited sampling strategies in estimating exposure to mycophenolic acid in people with autoimmune disease?

Mycophenolic acid (MPA) is a potent immunosuppressant agent, which is increasingly being used in the treatment of patients with various autoimmune diseases. Dosing to achieve a specific target MPA area under the concentration-time curve from 0 to 12 h post-dose (AUC12) is likely to lead to better treatment outcomes in patients with autoimmune disease than a standard fixed-dose strategy. This review summarizes the available published data around concentration monitoring strategies for MPA in patients with autoimmune disease and examines the accuracy and precision of methods reported to date using limited concentration-time points to estimate MPA AUC12. A total of 13 studies were identified that assessed the correlation between single time points and MPA AUC12 and/or examined the predictive performance of limited sampling strategies in estimating MPA AUC12. The majority of studies investigated mycophenolate mofetil (MMF) rather than the enteric-coated mycophenolate sodium (EC-MPS) formulation of MPA. Correlations between MPA trough concentrations and MPA AUC12 estimated by full concentration-time profiling ranged from 0.13 to 0.94 across ten studies, with the highest associations (r (2) = 0.90-0.94) observed in lupus nephritis patients. Correlations were generally higher in autoimmune disease patients compared with renal allograft recipients and higher after MMF compared with EC-MPS intake. Four studies investigated use of a limited sampling strategy to predict MPA AUC12 determined by full concentration-time profiling. Three studies used a limited sampling strategy consisting of a maximum combination of three sampling time points with the latest sample drawn 3-6 h after MMF intake, whereas the remaining study tested all combinations of sampling times. MPA AUC12 was best predicted when three samples were taken at pre-dose and at 1 and 3 h post-dose with a mean bias and imprecision of 0.8 and 22.6 % for multiple linear regression analysis and of -5.5 and 23.0 % for maximum a posteriori (MAP) Bayesian analysis. Although mean bias was less when data were analysed using multiple linear regression, MAP Bayesian analysis is preferable because of its flexibility with respect to sample timing. Estimation of MPA AUC12 following EC-MPS administration using a limited sampling strategy with samples drawn within 3 h post-dose resulted in biased and imprecise results, likely due to a longer time to reach a peak MPA concentration (t max) with this formulation and more variable pharmacokinetic profiles. Inclusion of later sampling time points that capture enterohepatic recirculation and t max improved the predictive performance of strategies to predict EC-MPS exposure. Given the considerable pharmacokinetic variability associated with mycophenolate therapy, limited sampling strategies may potentially help in individualizing patient dosing. However, a compromise needs to be made between the predictive performance of the strategy and its clinical feasibility. An opportunity exists to combine research efforts globally to create an open-source database for MPA (AUC, concentrations and outcomes) that can be used and prospectively evaluated for AUC target-controlled dosing of MPA in autoimmune diseases.

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.

A pilot study on area under curve of mycophenolic acid as a guide for its optimal use in renal transplant recipients

Background & objectives:

The immunosuppressants administered to renal transplant subjects are usually monitored therapeutically to prevent graft rejection and drug toxicity. Mycophenolic acid (MPA) is an immunosuppressant. The present prospective study was undertaken to establish the utility of plasma level monitoring of MPA and to correlate it with clinical outcomes in renal transplant receipients.

Methods:

MPA plasma level at 2, 4 and 9 h and the area under concentration-time curve (AUC) were estimated using high performance liquid chromatography in 24 renal transplant recipients receiving immunosuppressant MPA plus tacrolimus and steroid.

Results:

There was wide inter-individual variation in MPA plasma level and the AUC. The incidences of gastrointestinal adverse drug events (diarrhoea and acidity) were significantly more in the high MPA AUC patients. Though biopsy proven acute rejection was not found, of the six subjects with lower MPA AUC (<30 mg.h/l), three were clinically diagnosed to develop tacrolimus nephrotoxicity. The Gastrointestinal Symptom Rating Scale (GSRS) and Gastrointestinal Quality of Life Index (GIQLI) scores represented better health related quality of life in lower MPA AUC than in the higher MPA AUC (>60 mg.h/l).

Interpretation & conclusions:

The present findings suggest the MPA AUC of 30 - 60 mg.h/l in the maintenance stage of renal transplant patients to have optimum clinical benefit and relegated adverse events profile indicating the usefulness of AUC of MPA with limited sampling strategy in optimizing its use.

The emerging role of Brazil in clinical trial conduct for transplantation

Brazil is a country with over 190 000 000 inhabitants and a health system composed of a large public, government managed system. Between 1999 and 2010 the number of deceased donors increased by 161%, from 3.8 to 9.9 pmp, and the number of solid organ transplants increased by 121%, from 2891 to 6402. This growth was a consequence of the creation of a well-organized national transplant program. Government funding, decentralization and educational investment in transplant coordinators and related professional were decisive. In 2009 Brazil was the second largest country in the absolute number of kidney transplants (n = 4259). There are significant region disparities in performance which are mainly due to the development status. Improvements in transplant and research regulations resulted in an increasing participation of Brazilian transplant centers in multicenter trials, reaching over 44 studies during the last 11 years. Brazilian centers have been involved in clinical trials using everolimus, sirolimus, fingolimod, mycophenolate mofetyl, mycophenolate sodium, tacrolimus modified-release, sotrastaurin, belatacept, JAK3 inhibitor CP690,550 and valganciclovir. The still increasing number of transplants performed every year along with more efficient regulatory and sanitary analysis, organized clinical research programs and reduction in region performance disparities will eventually increase even more the participation of Brazil in trials worldwide.