Mycophenolate Mofetil for Myasthenia Gravis A Double-Blind, Placebo-Controlled Pilot Study

Comparative effectiveness of azathioprine and mycophenolate mofetil for myasthenia gravis (PROMISE-MG): a prospective cohort study

BACKGROUND

Myasthenia gravis is an autoimmune disorder of the neuromuscular junction. Treatment typically includes symptomatic oral cholinesterase inhibitors, immunosuppression, and immunomodulation. In addition to corticosteroids, azathioprine and mycophenolate mofetil are the most frequently used immunosuppressants in North America. We aimed to evaluate the comparative effectiveness of these two drugs, and to assess the effect of the dose and duration of treatment.

METHODS

We did a prospective cohort study at 19 academic centres in Canada and the USA. We included patients (aged ≥18 years) with autoimmune myasthenia gravis, who were never treated with immunosuppressants. Treating clinicians determined the choice of medication, dose, follow-up intervals, and drug monitoring. Outcome measures and adverse events were recorded at each visit. We assessed two co-primary outcomes. The first was the patient-reported Myasthenia Gravis-Quality of Life 15-revised (MGQOL-15r) score, measured as the mean change from treatment initiation to the follow-up visit with the lowest score. A clinically meaningful reduction (CMR) in MGQOL-15r was defined as a 5-point decrease. The second was a composite clinical outcome of disease improvement (Myasthenia Gravis Foundation of America Post-Intervention Status Minimal Manifestations or better) and low adverse event burden (defined as grade ≤1 Common Terminology Criteria for Adverse Events). We also compared these outcomes in patients receiving an adequate dose and duration of azathioprine (≥2 mg/kg per day for at least 12 months) or mycophenolate mofetil (≥2 g per day for at least 8 months) and a lower dose or shorter duration of these agents. We used propensity score weighting with generalised linear regression models. This study is registered with ClinicalTrials.gov (NCT03490539).

FINDINGS

Between May 1, 2018, and Aug 31, 2020, 167 patients were enrolled; 85 did not receive azathioprine or mycophenolate mofetil and were excluded. Four were excluded from outcome analyses because they had scores of 0 on an outcome measure at treatment initiation. Of the 78 patients included in analyses, 47 received mycophenolate mofetil (median follow-up 25 months [IQR 13·5-31·5]) and 31 received azathioprine (median follow-up 20 months [IQR 13-30]). The mean change in MG-QOL15r was -10·4 (95% CI -18·9 to -1·3) with mycophenolate mofetil and -6·8 (-17·2 to 3·6) with azathioprine (mean difference -3·3, 95% CI -7·7 to 1·2; p=0·15). 38 (81%) of 47 patients receiving mycophenolate mofetil and 18 (57%) of 31 receiving azathioprine had a CMR in MG-QOL15r (risk difference 24·0%; 95% CI -0·2 to 48·0; p=0·052). The clinical composite outcome was achieved in 22 (47·7%) of 47 patients who received mycophenolate mofetil and nine (28·1%) of 31 who received azathioprine (risk difference 19·6%, 95% CI -4·9 to 44·2; p=0·12). Descriptive analysis did not find a difference in the proportion of patients reaching a CMR in MG-QOL15r between the adequate dose and duration group and the lower dose or shorter duration group. Adverse events occurred in 11 (32%) of 34 patients who received azathioprine and nine (19%) of 48 who received mycophenolate mofetil. The most frequent adverse events were hepatotoxicity with azathioprine (five [15%] of 34) and gastrointestinal disturbances (seven [15%] of 48) with mycophenolate mofetil. There were no study-related deaths.

INTERPRETATION

More than half of patients treated with azathioprine and mycophenolate mofetil felt their quality of life improved; no difference in clinical outcomes was noted between the two drugs. Adverse events associated with azathioprine were potentially more serious than those with mycophenolate mofetil, although mycophenolate mofetil is teratogenic. Lower than recommended doses of azathioprine might be effective, with reduced dose-dependent adverse events. More comparative effectiveness studies are required to inform treatment choices in myasthenia gravis.

FUNDING

Patient-Centered Outcomes Research Institute, Myasthenia Gravis Foundation of America.

Unlocking the Complexity of Neuromuscular Diseases: Insights from Human Pluripotent Stem Cell-Derived Neuromuscular Junctions

Over the past 20 years, the use of pluripotent stem cells to mimic the complexities of the human neuromuscular junction has received much attention. Deciphering the key mechanisms underlying the establishment and maturation of this complex synapse has been driven by the dual goals of addressing developmental questions and gaining insight into neuromuscular disorders. This review aims to summarise the evolution and sophistication of in vitro neuromuscular junction models developed from the first differentiation of human embryonic stem cells into motor neurons to recent neuromuscular organoids. We also discuss the potential offered by these models to decipher different neuromuscular diseases characterised by defects in the presynaptic compartment, the neuromuscular junction, and the postsynaptic compartment. Finally, we discuss the emerging field that considers the use of these techniques in drug screening assay and the challenges they will face in the future.

Current Treatment of Myasthenia Gravis

Myasthenia gravis (MG) is the most extensively studied antibody-mediated disease in humans. Substantial progress has been made in the treatment of MG in the last century, resulting in a change of its natural course from a disease with poor prognosis with a high mortality rate in the early 20th century to a treatable condition with a large proportion of patients attaining very good disease control. This review summarizes the current treatment options for MG, including non-immunosuppressive and immunosuppressive treatments, as well as thymectomy and targeted immunomodulatory drugs.

Global prevalence of myasthenia gravis and the effectiveness of common drugs in its treatment: a systematic review and meta-analysis

BACKGROUND

Myasthenia gravis is a neuromuscular autoimmune disorder characterized by weakness and disability in the voluntary muscles. There have been several preliminary studies on the epidemiology of myasthenia gravis in different parts of the world and the effectiveness of common drugs in its treatment, but there has been no comprehensive study of the efficacy of common drugs in the treatment of myasthenia gravis. Therefore, this study aimed to determine the epidemiology of myasthenia gravis globally and the effectiveness of common drugs in its treatment using systematic review and meta-analysis.

METHODS

Research studies were extracted from IranDoc, MagIran, IranMedex, SID, ScienceDirect, Web of Sciences (WoS), ProQuest, Medline (PubMed), Scopus and Google Scholar based on Cochran's seven-step guidelines using existing keywords extracted in MeSH browser. The I2 test was used to calculate the heterogeneity of studies, and Begg and Mazumdar rank correlation tests were used to assess publication bias. Data were analyzed using Comprehensive Meta-Analysis software (Version 2).

RESULTS

In the search for descriptive studies based on the research question, 7374 articles were found. After deleting articles unrelated to the research question, finally, 63 articles with a sample size of 1,206,961,907 people were included in the meta-analysis. The prevalence of MG worldwide was estimated to be 12.4 people (95% CI 10.6-14.5) per 100,000 population. For analytical studies on the effectiveness of common myasthenia gravis drugs, 4672 articles were found initially, and after removing articles unrelated to the research question, finally, 20 articles with a sample size of 643 people in the drug group and 619 people in the placebo group were included in the study. As a result of the combination of studies, the difference between the mean QMGS score index after taking Mycophenolate and Immunoglobulin or plasma exchange drugs in the group of patients showed a significant decrease of 1.4 ± 0.77 and 0.62 ± 0.28, respectively (P < 0.01).

CONCLUSION

The results of systematic review of drug evaluation in patients with myasthenia gravis showed that Mycophenolate and Immunoglobulin or plasma exchange drugs have positive effects in the treatment of MG. It also represents the positive effect of immunoglobulin or plasma exchange on reducing SFEMG index and QMGS index and the positive effect of Mycophenolate in reducing MG-ADL index, SFEMG and Anti-AChR antibodies index. In addition, based on a meta-analysis of the random-effect model, the overall prevalence of MG in the world is 12.4 people per 100,000 population, which indicates the urgent need for attention to this disease for prevention and treatment.

Progress in the therapy of myasthenia gravis: getting closer to effective targeted immunotherapies

PURPOSE OF REVIEW

To provide an update on immunomodulating and immunosuppressive therapies in myasthenia gravis and highlight newly approved, or pending approval, therapies with new biologics.

RECENT FINDINGS

Preoperative IVIg is not needed to prevent myasthenic crisis in stable myasthenia gravis patients scheduled for surgery under general anesthesia, based on controlled data. Rituximab, if initiated early in new-onset myasthenia gravis, can lead to faster and more sustained remission even without immunotherapies in 35% of patients at 2 years. Biomarkers determining the timing for follow-up infusions in Rituximab-responding AChR-positive patients are discussed. Most patients with MuSK-positive myasthenia gravis treated with Rituximab have sustained long-term remission with persistent reduction of IgG4 anti-MuSK antibodies. Eculizumb in the extension REGAIN study showed sustained long-term pharmacological remissions and reduced exacerbations. Three new biologic agents showed promising results in phase-II controlled myasthenia gravis trials: Zilucoplan, a subcutaneous macrocyclic peptide inhibiting complement C5; Efgartigimod, an IgG1-derived Fc fragment binding to neonatal FcRn receptor; and Rozanolixizumab, a high-affinity anti-FcRn monoclonal antibody. Finally, the safety of ongoing myasthenia gravis immunotherapies during COVID19 pandemic is discussed.

SUMMARY

New biologics against B cells, complement and FcRn receptor, are bringing us closer to successful targeted immunotherapies in the chronic management of myasthenia gravis promising an exciting future for antibody-mediated neurological diseases.

Outcome Measures in Clinical Trials of Patients With Myasthenia Gravis

Myasthenia gravis (MG) is a heterogeneous disorder whose clinical presentation ranges from mild ocular deficits to severe widespread weakness. This variance poses a challenge when quantifying clinical deficits. Deficits and symptoms are quantified using standardized clinical scales and questionnaires which are often used as outcome measures. The past decades have seen the development of several validated outcome measures in MG, which are used in clinical trials to obtain regulatory approval. In recent years, emphasis has moved from objective assessments to patient-reported outcomes. Despite a growing body of literature on the validity of the MG-specific outcome measures, several unresolved factors remain. As several novel therapeutics are currently in clinical development, knowledge about capabilities and limitations of outcome measures is needed. In the present paper, we describe the most widely used clinical classifications and scales in MG. We highlight the choice of outcome measures in published and ongoing trials, and we denote whether trial efficacy was reached on these outcomes. We discuss advantages and limitations of the individual scales, and discuss some of the unresolved factors relating to outcome assessments in MG.

Treatment of refractory myasthenia gravis by double-filtration plasmapheresis and rituximab: A case series of nine patients and literature review

INTRODUCTION

Myasthenia gravis (MG) is an autoimmune disease mediated by circulating autoantibodies (anti-AchR, anti-MuSK, etc.). More than 20% of myasthenic patients are refractory to conventional treatments (plasma exchange, IVIg, steroids, azathioprine, mycophenolate mofetil). Rituximab (B-lymphocyte-depleting anti-CD20) and apheresis (double-filtration plasmapheresis [DFPP] and immunoadsorption [IA]) are interesting therapeutic alternatives.

METHODS

This monocentric pilot study included nine refractory myasthenic patients (March 2018 to May 2020) treated by DFPP and/or IA associated with rituximab (375 mg/m² ). Clinical responses were assessed using the Myasthenia Gravis Foundation of America (MGFA) score.

RESULTS

Average age of patients was 53 ± 17 years. Gender ratio (M/F) was 3:6. The combination of apheresis and rituximab reduced median MGFA score from IV to II after 12 months of follow-up. Clinical improvement assessed by MGFA score was sustained in the long-term for all patients, during an average follow-up of 14 ± 9 months, allowing them to be self-sufficient and out sick-leave. The median number of apheresis sessions was 7 (5-30). The dose of prednisolone was reduced in two patients from 40 mg/d and 30 mg/d to 7.5 mg/d and 10 mg/d, respectively. It was stopped in a patient who was taking 30 mg/d. No infectious, bleeding, or thrombosis complications were noted.

CONCLUSION

The combination of rituximab and DFPP was effective to treat refractory MG.

Immunotherapy in myasthenia gravis in the era of biologics

No consensus has been reached on the ideal therapeutic algorithm for myasthenia gravis (MG). Most patients with MG require induction therapy with high doses of corticosteroids and maintenance with an immunosuppressant. Severe cases and acute worsening require intravenous immunoglobulin or plasmapheresis before oral immunosuppressants start having an effect. However, biologics are emerging as important therapeutic tools that promise to provide better corticosteroid sparing effects than standard treatments and can even induce remission. In particular, eculizumab, a monoclonal antibody against complement C5, has been approved by the FDA for refractory MG on the basis of a phase III trial. Rituximab, an anti-CD20 monoclonal antibody that depletes peripheral B cells, has also been effective in many large uncontrolled series, although was not in a small phase III trial. Whether the newer anti-CD20 agents ocrelizumab, ofatumumab, obinutuzumab, ublituximab or inebilizumab will be more effective remains unclear. Belimumab, an antibody against the B cell trophic factor BAFF, was ineffective in phase III trials, and efgartigimod, which depletes antibodies, was effective in a phase II study. Some anti-cytokine agents relevant to MG immunopathogenesis also seem promising. Checkpoint inhibitors can trigger MG in some patients, necessitating early intervention. Increased availability of new biologics provides targeted immunotherapies and the opportunities to develop more specific therapies.

Maintenance immunosuppression in myasthenia gravis, an update

Therapies for myasthenia gravis (MG) include symptomatic and immunosuppressive/immunomodulatory treatment. Options for immunosuppression include corticosteroids, azathioprine, mycophenolate mofetil, cyclosporine, tacrolimus, methotrexate, rituximab, cyclophosphamide, eculizumab, intravenous immunoglobulin, subcutaneous immunoglobulin, plasmapheresis, and thymectomy. The practical aspects of long-term immunosuppressive therapy in MG are critically reviewed in this article. Application of one or more of these specific therapies is guided based on known efficacy, adverse effect profile, particular disease subtype and severity, and patient co-morbidities.

Immunosuppressive and monoclonal antibody treatment for myasthenia gravis: A network meta-analysis

BACKGROUND

We intended to compare and rank all the immunotherapies including immunosuppressant agents or monoclonal antibodies for myasthenia gravis (MG).

METHODS

A network meta-analysis was performed to synthesize the direct evidence and indirect evidence. Quantitative MG score (QMGS) was defined as the primary outcome. The secondary outcomes included the glucocorticoid reduction and hazard ratios (HR) from the counts of adverse events (AEs).

RESULTS

We identified 14 studies including 808 MG patients. For the primary outcome, cyclosporine A (CsA) was hierarchically the best with statistical significances of -1.18 (-1.81, -0.59) vs placebo (PLA), -0.98 (-1.72, -0.23) vs mycophenolate mofetil, and -0.77 (-1.57, -0.032) vs tacrolimus (TAC). When the intervention periods were controlled, both eculizumab (ECZ) of -1.50 (-2.81, -0.18) and CsA of -1.23 (-1.81, -0.64) vs PLA reached a statistical significance. Belimumab and ECZ ranked the most tolerable therapies while CsA of 2.41 (0.58, 10.01) ranked the last vs PLA.

CONCLUSION

These findings demonstrated that ECZ represented the most effective and tolerable therapeutic alternative to be recommended for refractory MG. TAC may be a beneficial therapy to treat MG extensively while the efficacy of CsA and cyclophosphamide may be limited by their multiple or severe AEs.

The placebo response in myasthenia gravis assessed by quantitative myasthenia gravis score: A meta-analysis

INTRODUCTION

This meta-analysis investigates the placebo response in generalized myasthenia gravis (MG) trials by means of Quantitative Myasthenia Gravis (QMG) scores.

METHODS

PubMed, Scopus, Web of Science, Cochrane Controlled Trial Register, and EMBASE were searched. QMG score, dropouts rate, adverse events (AEs), and AEs responsible for dropouts were examined, together with treatment moderators.

RESULTS

The magnitude of placebo response showed an effect size of 0.24, which was significantly lower than 0.67 of the drug response (P = 0.019). Furthermore, the forest plot revealed that, overall, active treatments showed a significantly higher impact on QMG scores than placebos.

CONCLUSIONS

Placebo and drug responses in MG trials are small and moderate, respectively. The lack of MG trials with a pure placebo arm or a no-treatment control arm made it impossible to disentangle improvements due to the placebo psychological effect from other effects such as natural history and/or regression to the mean. Muscle Nerve 59:671-678, 2019.

Recent advances in understanding and managing myasthenia gravis

Autoimmune myasthenia gravis (MG) is a neuromuscular junction disorder marked clinically by fatigable muscle weakness and serologically by the presence of autoantibodies against acetylcholine receptors (AChRs), muscle-specific kinase (MuSK), or lipoprotein-related protein 4 (LPR4). Over the past few decades, the mortality of patients with MG has seen a dramatic decline secondary to evolving interventions in critical care and medical management. In the past 2 to 3 years, there have been several changes in standard of care for the treatment of MG. These changes include confirmation of the benefit of thymectomy versus medical management alone in AChR patients and a new US Food and Drug Administration-approved medication for refractory MG. There are also several exciting new prospective drugs in the pipeline, which are in different stages of clinical trial testing.

Advances in autoimmune myasthenia gravis management

INTRODUCTION

Myasthenia gravis (MG) is an autoimmune neuromuscular disorder with no cure and conventional treatments limited by significant adverse effects and variable benefit. In the last decade, therapeutic development has expanded based on improved understanding of autoimmunity and financial incentives for drug development in rare disease. Clinical subtypes exist based on age, gender, thymic pathology, autoantibody profile, and other poorly defined factors, such as genetics, complicate development of specific therapies. Areas covered: Clinical presentation and pathology vary considerably among patients with some having weakness limited to the ocular muscles and others having profound generalized weakness leading to respiratory insufficiency. MG is an antibody-mediated disorder dependent on autoreactive B cells which require T-cell support. Treatments focus on elimination of circulating autoantibodies or inhibition of effector mechanisms by a broad spectrum of approaches from plasmapheresis to B-cell elimination to complement inhibition. Expert commentary: Standard therapies and those under development are disease modifying and not curative. As a rare disease, clinical trials are challenged in patient recruitment. The great interest in development of treatments specific for MG is welcome, but decisions will need to be made to focus on those that offer significant benefits to patients.

Clinical trials for myasthenia gravis: a historical perspective

Symposia dedicated to myasthenia gravis and related disorders date back to 1947 and serve as markers of the progress for the field. We provide a brief historical review of therapy development through the lens of the publications that arose from the close to quinquennial meetings that have been supported nearly since their inception by the Myasthenia Gravis Foundation of America and the New York Academy of Sciences. One can appreciate great advances, false starts, and dead ends that are found in all fields of medicine. We tally up the score card for MG and find points scored, but the win is not yet close.

Mycophenolate Mofetil Treatment of Myasthenia Gravis

Objective:

To review published literature evaluating the effectiveness of mycophenolate mofetil for the treatment of myasthenia gravis (MG).

Data Sources:

Searches of MEDLINE (1966–August 2005) and Cochrane Database (1993–August 2005) were conducted. Studies conducted in humans and published in English were retrieved. Additional data were identified through subsequent bibliographic reviews.

Data Synthesis:

Interruption of T- and B-lymphocyte proliferation in various autoimmune diseases has been investigated. Mycophenolate is known to inhibit lymphocyte proliferation and has shown improved clinical responses in several autoimmune diseases including lupus erythematosus, rheumatoid arthritis, and systemic vasculitis. Data suggesting similar benefits in MG treatment have been reported in case reports, retrospective analyses, an open-label trial, and a randomized, double-blind trial.

Conclusions:

Limited evidence from retrospective analyses and clinical trials suggests that mycophenolate is a possible treatment option for patients with MG. Improvement in clinical symptoms and a steroid-sparing effect have been reported when mycophenolate is used in this patient population. Larger, randomized, controlled, and comparative trials are needed to establish optimal dose, time to effect, specific therapeutic role, and long-term safety for mycophenolate when used for treating MG.

Mycophenolate mofetil and myasthenia gravis

Myasthenia gravis (MG) represents the prototypic autoimmune disorder with well characterized immunopathology. Advances in the diagnosis and treatment of this neuromuscular transmission disorder have significantly improved the management of myasthenic patients. Unfortunately the currently available immunomodulating treatments have significant side effects and some patients do not tolerate them or adequately respond to them. Therefore the possibility of a new immunosuppressant agent that is safe, effective and has steroid-sparing effect is very appealing. Mycophenolate mofetil (MMF) has shown promising effects in MG patients in preliminary studies and is currently being studied in two prospective, randomized, double-blind, placebo controlled, multicenter trials to better establish its role in the treatment of MG.

Immunosuppressant and immunomodulatory treatments for multifocal motor neuropathy

BACKGROUND

Multifocal motor neuropathy (MMN) is characterised by progressive, predominantly distal, asymmetrical limb weakness and usually multiple partial motor nerve conduction blocks. Intravenous immunoglobulin (IVIg) is beneficial but the role of immunosuppressive agents is uncertain. This is an update of a review first published in 2002 and previously updated in 2003, 2005, 2008 and 2011.

OBJECTIVES

To assess the effects of immunosuppressive agents for the treatment of multifocal motor neuropathy.

SEARCH METHODS

On 22 September 2014 we searched the Cochrane Neuromuscular Disease Group Specialized Register, CENTRAL, MEDLINE, EMBASE and LILACS for trials of MMN. We also searched two trials registers for ongoing studies.

SELECTION CRITERIA

We planned to include randomised controlled trials (RCTs) and quasi-RCTs. We considered prospective and retrospective case series and case reports in the Discussion.

DATA COLLECTION AND ANALYSIS

Two review authors searched the titles and abstracts of the articles identified and extracted the data independently.

MAIN RESULTS

Only one RCT of an immunosuppressive or immunomodulatory agent has been performed in MMN. This study randomised 28 participants and showed that mycophenolate mofetil, when used with IVIg, did not significantly improve strength, function or reduce the need for IVIg. No serious adverse events were observed. The study was deemed at low risk of bias. We summarised the results of retrospective and prospective case series in the discussion.

AUTHORS' CONCLUSIONS

According to moderate quality evidence, mycophenolate mofetil did not produce significant benefit in terms of reducing need for IVIg or improving muscle strength in MMN. Trials of other immunosuppressants should be undertaken.

EFNS/ENS Guidelines for the treatment of ocular myasthenia

BACKGROUND AND PURPOSE

The symptoms of acquired autoimmune ocular myasthenia are restricted to the extrinsic eye muscles, causing double vision and drooping eyelids. These guidelines are designed to provide advice about best clinical practice based on the current state of clinical and scientific knowledge and the consensus of an expert panel.

SEARCH STRATEGY

Evidence for these guidelines was collected by searches in the MEDLINE and Cochrane databases. The task force working group reviewed evidence from original articles and systematic reviews. The evidence was classified (I, II, III, IV) and consensus recommendation graded (A, B or C) according to the EFNS guidance. Where there was a lack of evidence but clear consensus, good practice points are provided.

CONCLUSIONS

The treatment of ocular myasthenia should initially be started with pyridostigmine (good practice point). If this is not successful in relieving symptoms, oral corticosteroids should be used on an alternate-day regimen (recommendation level C). If steroid treatment does not result in good control of the symptoms or if it is necessary to use high steroid doses, steroid-sparing treatment with azathioprine should be started (recommendation level C). If ocular myasthenia gravis is associated with thymoma, thymectomy is indicated. Otherwise, the role of thymectomy in ocular myasthenia is controversial. Steroids and thymectomy may modify the course of ocular myasthenia and prevent myasthenia gravis generalization (good practice point).

Dentistry and the myasthenia gravis patient: a review of the current state of the art

Myasthenia gravis (MG) is a chronic neuromuscular disease characterized by muscular weakness and fatigability. Dental management of patients diagnosed with MG presents a challenge to the oral health care provider. The purpose of this article was to review the etiology, pathogenesis, diagnosis, and clinical signs and symptoms associated with MG, highlighting the role of the oral health care provider in the process of diagnosis and management of the oral and dental complications that might be associated with the disease, while avoiding myasthenic crisis. A discussion of the recent approaches to treatment of the disease and current research on MG is presented.

Opportunistic infections in myasthenia gravis treated with mycophenolate mofetil

Mycophenolate mofetil (MMF) is used for immunosuppression in myasthenia gravis (MG). Although there are numerous data on associated infection and prophylaxis in transplant patients who are on MMF, data in MG remains lacking. We report two elderly seropositive MG patients who developed cytomegalovirus (CMV) enteritis and Epstein-Barr virus (EBV) encephalitis while on MMF for 5months and 1year, respectively. Chronic MMF therapy in MG patients may trigger life-threatening infections including CMV and EBV diseases, especially in the elderly. Similar to the practice in transplant patients, viral serology testing and appropriate prophylactic regimen with antiviral agents should be considered, particularly in older MG patients.

Immunosuppressant and immunomodulatory treatments for multifocal motor neuropathy

BACKGROUND

Multifocal motor neuropathy is characterised by progressive, predominantly distal, asymmetrical limb weakness and usually multiple partial motor nerve conduction blocks. Intravenous immunoglobulin is beneficial but the role of immunosuppressive agents is uncertain. This is an update of a review first published in 2002 and previously updated in 2003, 2005 and 2008.

OBJECTIVES

To provide the best available evidence from randomised controlled trials on the role of immunosuppressive agents for the treatment of multifocal motor neuropathy.

SEARCH METHODS

We searched the Cochrane Neuromuscular Disease Group Specialized Register (4 October 2011), the Cochrane Central Register of Controlled Trials (CENTRAL) (2011, Issue 3 in The Cochrane Library), MEDLINE (January 1966 to September 2011), EMBASE (January 1980 to September 2011), and LILACS (January 1982 to September 2011) for trials of multifocal motor neuropathy.

SELECTION CRITERIA

We planned to include randomised and quasi-randomised controlled trials. We considered prospective and retrospective case series and case reports in the Discussion.

DATA COLLECTION AND ANALYSIS

Two review authors searched the titles and abstracts of the articles identified and extracted the data independently.

MAIN RESULTS

Only one randomised controlled trial of an immunosuppressive or immunomodulatory agent has been performed in multifocal motor neuropathy. This study randomised 28 participants and showed that mycophenolate mofetil, when used with intravenous immunoglobulin, did not significantly improve strength, function or reduce the need for intravenous immunoglobulin. No serious adverse events were observed. The study was deemed at low risk of bias. We summarised the results of retrospective and prospective case series in the discussion.

AUTHORS' CONCLUSIONS

According to moderate quality evidence, mycophenolate mofetil did not produce significant benefit in terms of reducing need for intravenous immunoglobulin or improving muscle strength. Trials of other immunosuppressants should be undertaken.

Treatment of myasthenia gravis based on its immunopathogenesis

The prognosis of myasthenia gravis (MG) has improved dramatically due to advances in critical-care medicine and symptomatic treatments. Its immunopathogenesis is fundamentally a T-cell-dependent autoimmune process resulting from loss of tolerance toward self-antigens in the thymus. Thymectomy is based on this immunological background. For MG patients who are inadequately controlled with sufficient symptomatic treatment or fail to achieve remission after thymectomy, remission is usually achieved through the addition of other immunotherapies. These immunotherapies can be classified into two groups: rapid induction and long-term maintenance. Rapid induction therapy includes intravenous immunoglobulin (IVIg) and plasma exchange (PE). These produce improvement within a few days after initiation, and so are useful for acute exacerbation including myasthenic crisis or in the perioperative period. High-dose prednisone has been more universally preferred for remission induction, but it acts more slowly than IVIg and PE, commonly only after a delay of several weeks. Slow tapering of steroids after a high-dose pulse offers a method of maintaining the state of remission. However, because of significant side effects, other immunosuppressants (ISs) are frequently added as "steroid-sparing agents". The currently available ISs exert their immunosuppressive effects by three mechanisms: 1) blocking the synthesis of DNA and RNA, 2) inhibiting T-cell activation and 3) depleting the B-cell population. In addition, newer drugs including antisense molecule, tumor necrosis factor alpha receptor blocker and complement inhibitors are currently under investigation to confirm their effectiveness. Until now, the treatment of MG has been based primarily on experience rather than gold-standard evidence from randomized controlled trials. It is hoped that well-organized studies and newer experimental trials will lead to improved treatments.

Treatment of myasthenia gravis

Myasthenia gravis (MG) is an antibody-mediated, neuromuscular transmission disorder, which ranges in clinical manifestations of ocular myasthenia that may be visually disabling to myasthenic crisis with patients suffering life-threatening respiratory insufficiency. MG also has pathophysiologic subgroups based on presence or absence of acetylcholine receptor or muscle-specific kinase antibodies and presence of thymoma. Cholinesterase inhibitors partially improve weakness, but the vast majority of patients require therapies that moderate the autoimmune attack. Mortality of MG has been reduced over the last century, but adverse effects of treatment compromise patient care and rigorous evidence to guide the clinician are lacking.

Mycophenolate mofetil as second line immunosuppressant in Myasthenia gravis--a long-term prospective open-label study

Background

The preferred immunosuppressive drug for long term treatment of myasthenia gravis (MG) is azathioprine (AZA). Mycophenolate mofetil (MMF) was suggested as an effective and safe second line alternative to AZA.

Methods

In a prospective open-label study, 11 patients with acetylcholine receptor antibody (AchR-ab) positive MG (n = 4 ocular MG, n = 7 generalized MG) were treated with MMF which replaced AZA. Reasons for the change of immunosuppressant therapy were side effects (n = 9) or unresponsiveness under AZA (n = 3).

Results

Mean duration of MMF treatment was 16.9 months (6-46 months). During MMF treatment AZA side effects resolved in 8/9 patients, concomitant therapy could be discontinued in 4 patients and reduced in 5 patients, and 5 patients remitted and 3 remained in remission. One MMF-refractory patient required add-on IVIG therapy and another with ocular MG showed signs of generalization after 20 months of MG treatment. One patient was diagnosed with bronchial carcinoma after 10 months of MMF treatment.

Conclusion

Due to its favourable spectrum of side effects compared to AZA MMF might serve as a second-line immunosuppressant in those MG patients who have not tolerated AZA.

Insights on chronic-relapsing opsoclonus-myoclonus from a pilot study of mycophenolate mofetil

Opsoclonus-myoclonus syndrome is characterized by abnormal lymphocyte trafficking into brain. The authors hypothesized that mycophenolate mofetil, a lymphocyte proliferation inhibitor, might be therapeutic. The cerebrospinal fluid and blood immunophenotypes of 15 children with predominantly chronic-relapsing opsoclonus-myoclonus syndrome were compared before and after treatment by flow cytometry. Mycophenolate mofetil reduced the cerebrospinal fluid expansion of HLA-DR+ activated T cells (-40%); the frequency of other T-cell or natural killer cell subsets remained unchanged, but cerebrospinal fluid B cells increased significantly. Adrenocorticotropic hormone dose was lowered by 64% over an average of 1.5 years, yet 73% eventually relapsed despite therapeutic drug levels. Prior treatment with rituximab prevented relapse-associated increase in cerebrospinal fluid B cells, without hindering mycophenolate mofetil-induced reduction in T-cell activation. These data demonstrate resistant immunologic problems in chronic-relapsing opsoclonus-myoclonus syndrome. Mycophenolate mofetil did not prevent relapse. The novel effect of mycophenolate mofetil on chronically activated T cells may contribute to its efficacy in T-cell mediated neurological disorders.

Immunosuppressant and immunomodulatory treatments for multifocal motor neuropathy

BACKGROUND

Multifocal motor neuropathy is characterised by progressive, predominantly distal, asymmetrical limb weakness and usually multiple partial motor nerve conduction blocks. Intravenous immunoglobulin is beneficial but the role of immunosuppressive agents is uncertain.

OBJECTIVES

To provide the best available evidence from randomised controlled trials on the role of immunosuppressive agents for the treatment of multifocal motor neuropathy.

SEARCH STRATEGY

For this update, we searched the Cochrane Neuromuscular Disease Group Trials Register (October 8 2008), the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2008, Issue 4), MEDLINE (from January 1966 to October 8 2008), and EMBASE (from January 1980 to October 8 2008), for trials of multifocal motor neuropathy.

SELECTION CRITERIA

Randomised and quasi-randomised controlled trials were to be included and one was found. Prospective and retrospective case series and case reports were considered in the Discussion.

DATA COLLECTION AND ANALYSIS

Two review authors searched the titles and abstracts of the articles identified and extracted the data independently.

MAIN RESULTS

In this update, we found the first randomised controlled trial of multifocal motor neuropathy. This study, which randomised 28 patients, showed that mycophenolate mofetil did not significantly improve strength or function or reduce the need for intravenous immunoglobulin. We summarised the results of retrospective and prospective case series in the discussion.

AUTHORS' CONCLUSIONS

In the only randomised placebo-controlled trial of any immunosuppressive agent, mycophenolate mofetil did not produce significant benefit. Trials of other immunosuppressants should be undertaken.

Mycophenolate mofetil for myasthenia gravis: a clear and present controversy

Mycophenolate mofetil (MMF) has been used to treat myasthenia gravis (MG) for over 10 years. MMF's use in the MG population stems from its theoretical mechanism of action and the medical literature that supports its benefit in MG patients. Recently, two large, double-blinded, placebo-controlled, randomized clinical trials were initiated to study the effectiveness of MMF for MG. One of these studies found no benefit in taking MMF with 20 mg of prednisone as compared to taking prednisone alone, while the other study demonstrated no advantage in taking MMF against placebo during a 36-week prednisone taper. This article critically reviews the medical literature on MMF's use in MG and suggests further research avenues on this topic.

Etanercept treatment in myasthenia gravis

Etanercept is a tumor necrosis factor (TNF) blocking agent that has been shown to suppress ongoing experimental autoimmune myasthenia gravis (EAMG). This subcutaneously administered TNF blocking agent has also been shown to be safe and effective in several rheumatological diseases including rheumatoid arthritis, psoriasis, and ankylosing spondylitis. A prospective clinical pilot trial of etanercept in corticosteroid-dependent autoimmune myasthenia gravis (MG) patients supports further study into etanercept as a treatment for MG.

Ocular myasthenia: diagnostic and treatment recommendations and the evidence base

PURPOSE OF REVIEW

Increasing rigor is being applied to medical decision making, but myasthenia gravis, commonly considered the best understood autoimmune disorder from a pathophysiological basis, lags other disciplines in the evidence base used to make clinical decisions. The review attempts to provide a focused, practical guideline for the diagnosis and treatment of ocular myasthenia within the limits of largely retrospective case series and expert opinion.

RECENT FINDINGS

Confirmation of clinical diagnosis continues to be challenging for ocular myasthenia. Despite the recognition of a new autoantigen, the muscle-specific kinase protein in generalized myasthenia gravis, it has been found to be only rarely identified in ocular myasthenia patients and therefore the majority of patients lack detectable autoantibodies and confirmation of a neuromuscular transmission disorder relies on specialized testing of single-fiber electromyography. The visual compromise of ocular myasthenia responds poorly to nonpharmacological and cholinesterase inhibitor therapy, and although corticosteroids are thought to be extremely effective, their toxicity is poorly defined in ocular myasthenia patients and whether they reduce the risk of development of generalized disease is not known.

SUMMARY

Rigorous clinical trials or large databases with outcome assessments are necessary in order to allow development of rational treatment strategies.

Myasthenia gravis

Myasthenia gravis (MG) is a rare, autoimmune neuromuscular junction disorder. Contemporary prevalence rates approach 1/5,000. MG presents with painless, fluctuating, fatigable weakness involving specific muscle groups. Ocular weakness with asymmetric ptosis and binocular diplopia is the most typical initial presentation, while early or isolated oropharyngeal or limb weakness is less common. The course is variable, and most patients with initial ocular weakness develop bulbar or limb weakness within three years of initial symptom onset. MG results from antibody-mediated, T cell-dependent immunologic attack on the endplate region of the postsynaptic membrane. In patients with fatigable muscle weakness, the diagnosis of MG is supported by: 1. pharmacologic testing with edrophonium chloride that elicits unequivocal improvement in strength; 2. electrophysiologic testing with repetitive nerve stimulation (RNS) studies and/or single-fiber electromyography (SFEMG) that demonstrates a primary postsynaptic neuromuscular junctional disorder; and 3. serologic demonstration of acetylcholine receptor (AChR) or muscle-specific tyrosine kinase (MuSK) antibodies. Differential diagnosis includes congenital myasthenic syndromes, Lambert Eaton syndrome, botulism, organophosphate intoxication, mitochondrial disorders involving progressive external ophthalmoplegia, acute inflammatory demyelinating polyradiculoneuropathy (AIDP), motor neuron disease, and brainstem ischemia. Treatment must be individualized, and may include symptomatic treatment with cholinesterase inhibitors and immune modulation with corticosteroids, azathioprine, cyclosporine, and mycophenolate mofetil. Rapid, temporary improvement may be achieved for myasthenic crises and exacerbations with plasma exchange (PEX) or intravenous immunoglobulin (IVIg). Owing to improved diagnostic testing, immunotherapy, and intensive care, the contemporary prognosis is favorable with less than five percent mortality and nearly normal life expectancy.