Effect of mycophenolic acid in experimental, nontransplant glomerular diseases: new mechanisms beyond immune cells

The Ca2+-actin-cytoskeleton axis in podocytes is an important, non-immunologic target of immunosuppressive therapy in proteinuric kidney diseases

The integrity of the filtration barrier of the kidney relies on the proper composition of podocyte interdigitating foot processes. Their architecture is supported by a complex actin-cytoskeleton. Following podocyte stress or injury, podocytes encounter structural changes, including rearrangement of the actin network and subsequent effacement of the foot processes. Immunosuppressive drugs, which are currently used as treatment in proteinuric kidney diseases, have been shown to exert not only immune-mediated effects. This review will focus on the direct effects of glucocorticoids, cyclosporine A, tacrolimus, mycophenolate mofetil, and rituximab on podocytes by regulation of Ca2+ ion channels and consecutive downstream signaling which prevent cytoskeletal rearrangements and ultimately proteinuria. In addition, the efficacy of these drugs in genetic nephrotic syndrome will be discussed.

Combination of rituximab and low-dose glucocorticoids for idiopathic refractory nephrotic syndrome with MCD/FSGS: a single-center prospective cohort study

BACKGROUND

The treatment of idiopathic refractory nephrotic syndrome (IRNS) remains a difficult problem in clinical practice. This study aims to determine the efficacy and safety of combining low-dose glucocorticoids with rituximab in IRNS treatment.

METHODS

This prospective, single-center cohort study enrolled 60 patients who were diagnosed with refractory IRNS with minimal change disease (MCD) or focal segmental glomerulosclerosis (FSGS) and treated at First Affiliated Hospital of Sun Yat-sen University. All patients received a treatment regimen consisting of rituximab (375 mg/m2/week × 4) and low-dose glucocorticoids.

RESULTS

46 complete remissions and 4 partial remissions were observed within 6 months of treatment. Within 12 months of treatment, 48 patients achieved complete remission, and 4 achieved partial remission. The complete remission rate for steroid-dependent/frequently relapsing nephrotic syndrome was significantly higher than that for steroid-resistant nephrotic syndrome (88.24% vs. 33.33%, p < .01). Following up for 12 months, 16 patients relapsed, accounting for 30.76% of the total, with a mean time to relapse of 10.97 months. Compared with baseline data, 24-hour urine protein quantification, total cholesterol and triglycerides significantly decreased, while serum albumin, globulin and IgG significantly increased at 12 months after treatment. All follow-ups were without serious adverse events. Twenty-four patients experienced infusion-related adverse reactions, which could be relieved by slowing down the infusion rate or suspending the infusion. Nine patients experienced infection-related adverse reactions; six of them were relieved with antibiotic treatment, and 3 patients were controlled by symptomatic treatment.

CONCLUSIONS

Rituximab combined low-dose glucocorticoids therapy is effective and safe in idiopathic refractory nephrotic syndrome.

Optimal exposure of mycophenolic acid for induction therapy of childhood lupus nephritis patients: an observational cohort study

OBJECTIVES

Mycophenolic acid (MPA) is recommended for lupus nephritis (LN) treatment, but with large inter-individual variability in pharmacokinetics (PK). The aim of this study is to reveal the relationship between MPA exposure and disease response and adverse drug reactions in pediatric LN patients.

METHOD

This was a population-based observational cohort study. A total of 86 pediatric LN patients treated with mycophenolate mofetil (MMF) for induction therapy were enrolled. The area-under the concentration-time curve (AUC) was calculated using MPA concentrations according to a limited sampling strategy. Receiver operating characteristic analysis was performed to assess the MPA-AUC threshold values. The cumulative incidence of renal remission and inactive systemic lupus erythematosus (SLE) over time was evaluated by Kaplan-Meier's analysis.

RESULTS

MPA-AUC was identified as an independent factor associated with renal remission and lupus activity at 6 and 12 months after MMF treatment, and the improved renal remission rates were correlated with higher MPA-AUC, with thresholds of 29.81 and 30.63 μg·h·mL-1 at 6 months and 12 months, respectively. Furthermore, the thresholds for maintaining the hypoactive state of LN were 30.96 and 31.19 μg·h·mL-1at 6 months and 12 months, respectively. Patients reaching target thresholds for MPA-AUC achieved renal response or stable disease earlier. In addition, the MPA-AUC threshold for decreasing MMF-related adverse reactions was 50.80 μg·h·mL-1.

CONCLUSION

The initial and long-term treatments of pediatric LN patients with MMF should be individualized according to the MPA-AUC, and the recommended MPA exposure is 31.19-50.80 μg·h·mL-1.

Physicochemical Characterization and In Vitro Activity of Poly(ε-Caprolactone)/Mycophenolic Acid Amorphous Solid Dispersions

The obtention of amorphous solid dispersions (ASDs) of mycophenolic acid (MPA) in poly(ε-caprolactone) (PCL) is reported in this paper. An improvement in the bioavailability of the drug is possible thanks to the favorable specific interactions occurring in this system. Differential scanning calorimetry (DSC) was used to investigate the miscibility of PCL/MPA blends, measuring glass transition temperature (Tg) and analyzing melting point depression to obtain a negative interaction parameter, which indicates the development of favorable inter-association interactions. Fourier transform infrared spectroscopy (FTIR) was used to analyze the specific interaction occurring in the blends. Drug release measurements showed that at least 70% of the drug was released by the third day in vitro in all compositions. Finally, preliminary in vitro cell culture experiments showed a decreased number of cancerous cells over the scaffolds containing MPA, presumably arising from the anti-cancer activity attributable to MPA.

The effect of mycophenolate mofetil on podocytes in nephrotoxic serum nephritis

Mycophenolate mofetil (MMF) is applied in proteinuric kidney diseases, but the exact mechanism of its effect on podocytes is still unknown. Our previous in vitro experiments suggested that MMF can ameliorate podocyte damage via restoration of the Ca2+-actin cytoskeleton axis. The goal of this study was to characterize podocyte biology during MMF treatment in nephrotoxic serum (NTS) nephritis (NTN). NTN was induced in three-week old wild-type mice. On day 3, half of the mice were treated with MMF (100 mg/kgBW/d p.o.) for one week. On day 10, we performed proteomic analysis of glomeruli as well as super-resolution imaging of the slit diaphragm. For multiphoton imaging of Ca2+ concentration ([Ca2+]i), the experimental design was repeated in mice expressing podocyte-specific Ca2+ sensor. MMF ameliorated the proteinuria and crescent formation induced by NTS. We identified significant changes in the abundance of proteins involved in Ca2+ signaling and actin cytoskeleton regulation, which was further confirmed by direct [Ca2+]i imaging in podocytes showing decreased Ca2+ levels after MMF treatment. This was associated with a tendency to restoration of podocyte foot process structure. Here, we provide evidence that MPA has a substantial direct effect on podocytes. MMF contributes to improvement of [Ca2+]i and amelioration of the disorganized actin cytoskeleton in podocytes. These data extend the knowledge of direct effects of immunosuppressants on podocytes that may contribute to a more effective treatment of proteinuric glomerulopathies with the least possible side effects.

How immunosuppressive drugs may directly target podocytes in glomerular diseases

Podocytes are the direct target of immunologic injury in many immune-mediated glomerular diseases, leading to proteinuria and subsequent kidney failure. Immunosuppressive agents such as steroids, calcineurin inhibitors, and rituximab are the commonly used treatment strategies in this context for their immunotherapeutic or anti-inflammatory properties. However, in recent years, studies have demonstrated that immunosuppressive agents can have a direct effect on podocytes, introducing the concept of the non-immunologic mechanism of kidney protection by immunomodulators. In this review, we focus on the mechanisms by which these agents may directly target the podocyte independent of their systemic effects and examine their clinical significance.

New Insights into the Treatment of Glomerular Diseases: When Mechanisms Become Vivid

Treatment for glomerular diseases has been extrapolated from the experience of other autoimmune disorders while the underlying pathogenic mechanisms were still not well understood. As the classification of glomerular diseases was based on patterns of juries instead of mechanisms, treatments were typically the art of try and error. With the advancement of molecular biology, the role of the immune agent in glomerular diseases is becoming more evident. The four-hit theory based on the discovery of gd-IgA1 gives a more transparent outline of the pathogenesis of IgA nephropathy (IgAN), and dysregulation of Treg plays a crucial role in the pathogenesis of minimal change disease (MCD). An epoch-making breakthrough is the discovery of PLA2R antibodies in the primary membranous nephropathy (pMN). This is the first biomarker applied for precision medicine in kidney disease. Understanding the immune system's role in glomerular diseases allows the use of various immunosuppressants or other novel treatments, such as complement inhibitors, to treat glomerular diseases more reasonable. In this era of advocating personalized medicine, it is inevitable to develop precision medicine with mechanism-based novel biomarkers and novel therapies in kidney disease.

Personalized Therapy for Mycophenolate: Consensus Report by the International Association of Therapeutic Drug Monitoring and Clinical Toxicology

ABSTRACT

When mycophenolic acid (MPA) was originally marketed for immunosuppressive therapy, fixed doses were recommended by the manufacturer. Awareness of the potential for a more personalized dosing has led to development of methods to estimate MPA area under the curve based on the measurement of drug concentrations in only a few samples. This approach is feasible in the clinical routine and has proven successful in terms of correlation with outcome. However, the search for superior correlates has continued, and numerous studies in search of biomarkers that could better predict the perfect dosage for the individual patient have been published. As it was considered timely for an updated and comprehensive presentation of consensus on the status for personalized treatment with MPA, this report was prepared following an initiative from members of the International Association of Therapeutic Drug Monitoring and Clinical Toxicology (IATDMCT). Topics included are the criteria for analytics, methods to estimate exposure including pharmacometrics, the potential influence of pharmacogenetics, development of biomarkers, and the practical aspects of implementation of target concentration intervention. For selected topics with sufficient evidence, such as the application of limited sampling strategies for MPA area under the curve, graded recommendations on target ranges are presented. To provide a comprehensive review, this report also includes updates on the status of potential biomarkers including those which may be promising but with a low level of evidence. In view of the fact that there are very few new immunosuppressive drugs under development for the transplant field, it is likely that MPA will continue to be prescribed on a large scale in the upcoming years. Discontinuation of therapy due to adverse effects is relatively common, increasing the risk for late rejections, which may contribute to graft loss. Therefore, the continued search for innovative methods to better personalize MPA dosage is warranted.

Autoimmunity in Focal Segmental Glomerulosclerosis: A Long-Standing Yet Elusive Association

Focal segmental glomerulosclerosis (FSGS) is a histological term that describes a pathologic renal entity affecting both adults and children, with a wide array of possible underlying etiologies. Podocyte damage with scarring, the hallmark of this condition, leads to altered permeability of the glomerular barrier, which may result in massive proteinuria and relentless renal function deterioration. A definite cause of focal segmental glomerulosclerosis can be confirmed in a minority of cases, while most forms have been traditionally labeled as primary or idiopathic. Despite this definition, increasing evidence indicates that primary forms are a heterogenous group rather than a single disease entity: several circulating factors that may affect glomerular permeability have been proposed as potential culprits, and both humoral and cellular immunity have been implicated in the pathogenesis of the disease. Consistently, immunosuppressive drugs are considered as the cornerstone of treatment for primary focal segmental glomerulosclerosis, but response to these agents and long-term outcomes are highly variable. In this review we provide a summary of historical and recent advances on the pathogenesis of primary focal segmental glomerulosclerosis, focusing on implications for its differential diagnosis and treatment.

Interferon-inducer antivirals: Potential candidates to combat COVID-19

Coronavirus disease 2019 (COVID-19) is an infective disease generated by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Given the pandemic urgency and lack of an effective cure for this disease, drug repurposing could open the way for finding a solution. Lots of investigations are ongoing to test the compounds already identified as antivirals. On the other hand, induction of type I interferons are found to play an important role in the generation of immune responses against SARS-CoV-2. Therefore, it was opined that the antivirals capable of triggering the interferons and their signaling pathway, could rationally be beneficial for treating COVID-19. On this basis, using a database of antivirals, called drugvirus, some antiviral agents were derived, followed by searches on their relevance to interferon induction. The examined list included drugs from different categories such as antibiotics, immunosuppressants, anti-cancers, non-steroidal anti-inflammatory drugs (NSAID), calcium channel blocker compounds, and some others. The results as briefed here, could help in finding potential drug candidates for COVID-19 treatment. However, their advantages and risks should be taken into account through precise studies, considering a systemic approach. Even though the adverse effects of some of these drugs may overweight their benefits, considering their mechanisms and structures may give a clue for designing novel drugs in the future. Furthermore, the antiviral effect and IFN-modifying mechanisms possessed by some of these drugs might lead to a synergistic effect against SARS-CoV-2, which deserve to be evaluated in further investigations.

Therapeutic drug monitoring of mycophenolate mofetil in pediatric patients: novel techniques and current opinion

Introduction: Mycophenolate mofetil (MMF) is an ester prodrug of the immunosuppressant mycophenolic acid (MPA) and is recommended and widely used for maintenance immunosuppressive therapy in solid organ and stem-cell transplantation as well as in immunological kidney diseases. MPA is a potent, reversible, noncompetitive inhibitor of the inosine monophosphate dehydrogenase (IMPDH), a crucial enzyme in the de novo purine synthesis in T- and B-lymphocytes, thereby inhibiting cell-mediated immunity and antibody formation. The use of therapeutic drug monitoring (TDM) of MMF is still controversial as outcome data of clinical trials are equivocal. Areas covered: This review covers in great depth the existing literature on TDM of MMF in the field of pediatric (kidney) transplantation. In addition, the relevance of TDM in immunological kidney diseases, in particular childhood nephrotic syndrome is highlighted. Expert opinion: TDM of MMF has the potential to optimize therapy in pediatric transplantation as well as in nephrotic syndrome. Limited sampling strategies to estimate MPA exposure increase its feasibility. Future perspectives rather encompass approaches reflecting total immunosuppressive load than single drug TDM.

Effective delivery of mycophenolic acid by oxygen nanobubbles for modulating immunosuppression

Immunosuppressive drugs are crucial for preventing acute graft rejection or autoimmune diseases. They are generally small molecules that require suitable drug carriers for ensuring stability, bioavailability, and longer half-life. Mycophenolic acid (MPA) is an extensively studied immunosuppressive drug. However, it requires suitable carriers for overcoming clinical limitations. Currently, lipid-shelled micro- and nanobubbles are being thoroughly investigated for diagnostic and therapeutic applications, as they possess essential properties, such as injectability, smaller size, gaseous core, high surface area, higher drug payload, and enhanced cellular penetration. Phospholipids are biocompatible and biodegradable molecules, and can be functionalized according to specific requirements.

Methods: In this study, we synthesized oxygen nanobubbles (ONBs) and loaded the hydrophobic MPA within the ONBs to generate ONB/MPA. Peripheral blood mononuclear cells (PBMCs) were treated with ONB/MPA to determine the suppression of immune response by measuring cytokine release. In vivo murine experiments were performed to evaluate the effectiveness of ONB/MPA in the presence of inflammatory stimulants.

Results: Our results suggest that ONBs successfully delivered MPA and reduced the release of cytokines, thereby controlling inflammation and significantly increasing the survival rate of animals.

Conclusion: This method can be potentially used for implantation and for treating autoimmune diseases, wherein immunosuppression is desired.

Effect of different rituximab regimens on B cell depletion and time to relapse in children with steroid-dependent nephrotic syndrome

BACKGROUND

Several studies have demonstrated that rituximab (RTX) improves relapse-free survival in patients with steroid-dependent nephrotic syndrome (SDNS). However, these studies used various RTX regimens and there are few data comparing these regimens in children with SDNS. In this retrospective study, we assessed the effect of three different initial RTX regimens on both time to B cell reconstitution and to first relapse.

METHODS

Sixty-one SDNS patients receiving a first course of RTX were included. Group 1 received one injection of 100 mg/m², group 2 received one injection of 375 mg/m², and group 3 received two injections of 375 mg/m² at day 0 and day 7. Time to B cell reconstitution and time to first relapse and respective risk factors were studied.

RESULTS

Median time to B cell reconstitution was 2.5 [1.8-3.5], 5.0 [3.9-6.0], and 6.6 [4.6-7.8] months in groups 1, 2, and 3, respectively. RTX regimen was associated with time to B cell reconstitution (HRs group 2 vs. 3, 4.07 [1.96-8.48]; group 1 vs. 3, 11.13 [4.04-30.67]). One-year relapse-free survival was 50% [58-77], 59% [42-76], and 72% [46-87] in groups 1, 2, and 3, respectively. RTX regimen was associated with risk of relapse (HRs group 2 vs. 3, 1.55 [0.51-4.65]; group 1 vs. 3, 4.98 [1.15-21.60]).

CONCLUSIONS

The initial dose of rituximab impacts time to B cell reconstitution and the probability of relapse. Risk of relapse is also associated with patient characteristics, suggesting that RTX regimen could be modified for each patient to balance efficacy, cost, and side effects.

Mycophenolate mofetil for sustained remission in nephrotic syndrome

The clinical application of mycophenolate mofetil (MMF) has significantly widened beyond the prophylaxis of acute and chronic rejections in solid organ transplantation. MMF has been recognized as an excellent treatment option in many immunologic glomerulopathies. For children with frequently relapsing nephrotic syndrome (FRNS) or steroid-dependent nephrotic syndrome (SDNS) experiencing steroid toxicity, MMF has been recommended as a steroid-sparing drug. Uncontrolled studies in patients with FRNS and SDSN have shown that many patients can achieve sustained remission of proteinuria with MMF monotherapy. Three randomized controlled trials have similarly demonstrated that MMF is beneficial in these patients, but less effective than the calcineurin inhibitors cyclosporin A or tacrolimus. Some, but not all, patients with steroid-resistant nephrotic syndrome (SRNS) may also respond to MMF, usually given in combination with other drugs, with partial or complete remission. There are important limitations to the interpretation and comparability of these studies including study design, sample size, patient selection, clinical endpoints, carry-over effects, and duration of follow-up. In all studies, MMF had relatively few side effects, no nephrotoxicity, or no systemic toxicity. MMF is teratogenic, and contraceptive advice is required in females. There is a poor correlation between MMF dose and mycophenolic acid (MPA) exposure and significant inter- and intra-patient variability in drug pharmacokinetics. A higher estimated MPA-AUC_0-12 target range than recommended for pediatric renal transplant recipients is essential to prevent relapses. Therefore, therapy should be guided by drug monitoring to avoid relapses. Further studies are needed to test the efficacy of MMF in inducing remission and, as part of a combination therapy, achieving sustained remission in patients with SRNS.

Mycophenolate mofetil following glucocorticoid treatment in Henoch-Schönlein purpura nephritis: the role of early initiation and therapeutic drug monitoring

BACKGROUND

Henoch-Schönlein purpura (HSP) is the most common vasculitis in childhood and traditionally considered as a self-limiting disease. However, renal involvement can unfavorably determine long-term prognosis. The reported regimens to treat HSP nephritis (HSPN) are diverse, indicating that the most effective treatment remains controversial.

METHODS

This retrospective, single-center study involved 18 patients presenting with HSPN and nephrotic-range proteinuria. We aimed to investigate the efficacy and safety of mycophenolate mofetil (MMF) and identify a cut-off level for estimated mycophenolic acid area under the curve (eMPA-AUC_0-12h) values, which can predict complete remission with high sensitivity.

RESULTS

Despite prior insufficient therapeutic response to corticosteroids, 89% of patients showed a significant decrease in proteinuria after 1 month of MMF treatment. None of them relapsed during treatment; however, two children relapsed after discontinuation. Based on results of a receiver operating characteristic (ROC) analysis, an eMPA-AUC_0-12h >56.4 mg*h/l was a predictor for complete remission within 3 months (80% sensitivity, 83.3% specificity, p = 0.035). During MMF administration, we encountered no adverse event requiring discontinuation of treatment.

CONCLUSION

Our study demonstrates that MMF is a safe and potentially effective secondary treatment option for children with HSPN to achieve and maintain long-term remission without serious side effects. To achieve complete remission within 3 months, resolve severe inflammatory glomerular lesions, and avoid progression to chronic kidney disease, we propose timely diagnosis and early initiation of MMF with an eMPA-AUC_0-12h value of 56.4 mg*h/l.