Successful treatment of a patient with severe refractory myasthenia gravis using mycophenolate mofetil

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.

Immunosuppression in Multiple Sclerosis and Other Neurologic Disorders

Multiple sclerosis (MS) is an autoimmune disease of the central nervous system (CNS) characterized by peripheral immune cell infiltration into the brain and spinal cord, demyelination, glial cell activation, and neuronal damage. Currently there is no cure for MS, however, available disease-modifying agents minimize inflammation in the CNS by various mechanisms. Approved drugs lessen severity of the disease and delay disease progression, however, they are still suboptimal as patients experience adverse effects and varying efficacies. Additionally, there is only one disease-modifying therapy available for the more debilitating, progressive form of MS. This chapter focuses on the presently-available therapeutics and, importantly, the future directions of MS therapy based on preclinical studies and early clinical trials. Immunosuppression in other neurological disorders including neuromyelitis optica spectrum disorders, myasthenia gravis, and Guillain-Barré syndrome is also discussed.

Update in immunosuppressive therapy of myasthenia gravis

Myasthenia gravis (MG) is an autoimmune disease of the neuromuscular junction. Immunosuppressive treatments are part of the therapeutic armamentarium in MG. Long-term systemic steroid administration carry considerable risks and adverse events. Consequently, steroid-free immunosuppressive therapy is necessary to reduce the dose or discontinue steroids. First immunosuppressive drug trials in MG were performed in the mid-60s using standard and nonspecific immunosuppression. Since then, only few randomized controlled clinical trials were conducted in MG and assesed drug efficacy in terms of its steroid-sparing capacity and the ability to reduce myasthenic signs and symptoms. Treatment strategy in MG is quite challenging, mainly due to the disease heterogeneity in terms of clinical presentation, immunopathogenesis and drug response. To solve this dilemma, emerging treatment are based on biological drugs and use new targets of the immune pathway.

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.

Treatment of Myasthenia Gravis

With specialized care, patients with myasthenia gravis can have very good outcomes. The mainstays of treatment are acetylcholinesterase inhibitors, and immunosuppressive and immunomodulatory therapies. There is good evidence thymectomy is beneficial in thymomatous and nonthymomatous disease. Nearly all of the drugs used for MG are considered "off-label." The 2 exceptions are acetylcholinesterase inhibitors and complement inhibition with eculizumab, which was recently approved by the US Food and Drug Administration for myasthenia gravis. This article reviews the evidence base and provides a framework for the treatment of myasthenia gravis, highlighting recent additions to the literature.

Myasthenia gravis: Historical achievements and the "golden age" of clinical trials

Since the death of Chief Opechankanough >350 years ago, the myasthenia gravis (MG) community has gained extensive knowledge about MG and how to treat it. This review highlights key milestones in the history of treatment and discusses the current "golden age" of clinical trials. Although originally thought by many clinicians to be a disorder of hysteria and fluctuating weakness without observable cause, MG is one the most understood autoimmune neurologic disorders. However, studying it in clinical trials has been challenging due to the fluctuating nature of the medical condition which impacts MG clinical outcomes. Clinical trials must also account for the possibility of a placebo effect. Because MG is a rare incurable autoimmune disorder, it limits the number of potential patients available to participate in clinical trials. In the last 15 years, however, significant progress has been made with MG randomized clinical trials, resulting in a new drug (eculizumab) for physicians' treatment repertoire and an old technique (thymectomy) confirmed effective for MG. Some of the therapies (eg, thymectomy, corticosteroids, plasma exchange, and intravenous immunoglobulin [IVIg]) have survived the test of time. Others (eg, eculizumab and neonatal Fc receptor inhibitor) are novel and hold promise.

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.

A one-year prospective, randomized, placebo-controlled, quadruple-blinded, phase II safety pilot trial of combination therapy with interferon beta-1a and mycophenolate mofetil in early relapsing-remitting multiple sclerosis (TIME MS)

BACKGROUND

Mycophenolate mofetil (MMF) is an oral DNA base synthesis inhibitor with immunomodulatory effects on B cells, T cells, and macrophages.

OBJECTIVE

To conduct a safety and tolerability pilot study of interferon beta-1a (IFN-b1a) in combination with either placebo or oral MMF in multiple sclerosis (MS).

METHODS

Twenty-four treatment-naïve R-RMS patients participated in a one-year prospective, placebo-controlled, blinded, safety pilot clinical trial. Every patient injected weekly intramuscular interferon beta-1a. The cohort was then randomized (1 : 1) to either active oral MMF or identical-appearing placebo tablets. Clinical evaluations were assessed every 3 months, along with brain MRI scans performed at baseline and repeated every 60 days for one year. Comprehensive laboratory assessments were monitored for safety, along with adverse events.

RESULTS

In this small pilot investigation, no differences were identified between the two treatment groups with respect to patient-reported adverse events, MRI metrics, or laboratory abnormalities. Notwithstanding these observations, and the limited number of patients treated, trends appeared to favor the combination therapy regimen.

CONCLUSIONS

The combination treatment regimen of interferon beta-1a and MMF appeared to be well tolerated in this pilot study. Despite the small sample size, therapeutic trends were observed in favor of combination therapy. An adequately powered controlled trial of MMF in MS appears warranted.

A randomized, blinded, parallel-group, pilot trial of mycophenolate mofetil (CellCept) compared with interferon beta-1a (Avonex) in patients with relapsing-remitting multiple sclerosis

BACKGROUND

Mycophenolate mofetil (MMF, CellCept®) has been utilized as an antirejection agent in transplant recipients and in patients with myriad autoimmune disorders including multiple sclerosis (MS).

OBJECTIVE

To investigate radiographic and clinical safety involving monotherapy use of daily oral MMF (1 g b.i.d.) versus weekly intramuscular interferon beta 1a (Avonex® at 30 mcg) in relapsing-remitting MS (RRMS).

METHODS

We organized a randomized, serial, 6-monthly, MRI-blinded, parallel-group multicenter pilot study to determine the safety of MMF versus interferon beta monotherapy in 35 untreated patients with RRMS, all of whom exhibited evidence of gadolinium (Gd) enhancement on a screening MRI of the brain. The primary outcome was the reduction in the cumulative mean number of combined active lesions (CAL), new Gd-enhancing lesions, and new T2 lesions on MRI analyses.

RESULTS

Both interferon beta and MMF appeared safe and well tolerated in the majority of patients. There was no difference between MMF therapy and the standard regimen of interferon beta therapy on the primary safety MRI endpoints of the study. However, the MMF group showed a trend toward a lower accumulation of combined active lesions, CAL, Gd and T2 lesions when compared with interferon beta treated patients.

CONCLUSIONS

The results from this pilot study suggest that the application of MMF monotherapy in MS deserves further exploration.

Guidelines for treatment of autoimmune neuromuscular transmission disorders

BACKGROUND

Important progress has been made in our understanding of the autoimmune neuromuscular transmission (NMT) disorders; myasthenia gravis (MG), Lambert-Eaton myasthenic syndrome (LEMS) and neuromyotonia (Isaacs' syndrome).

METHODS

To prepare consensus guidelines for the treatment of the autoimmune NMT disorders, references retrieved from MEDLINE, EMBASE and the Cochrane Library were considered and statements prepared and agreed on by disease experts.

CONCLUSIONS

Anticholinesterase drugs should be given first in the management of MG, but with some caution in patients with MuSK antibodies (good practice point). Plasma exchange is recommended in severe cases to induce remission and in preparation for surgery (recommendation level B). IvIg and plasma exchange are effective for the treatment of MG exacerbations (recommendation level A). For patients with non-thymomatous MG, thymectomy is recommended as an option to increase the probability of remission or improvement (recommendation level B). Once thymoma is diagnosed, thymectomy is indicated irrespective of MG severity (recommendation level A). Oral corticosteroids are first choice drugs when immunosuppressive drugs are necessary (good practice point). When long-term immunosuppression is necessary, azathioprine is recommended to allow tapering the steroids to the lowest possible dose whilst maintaining azathioprine (recommendation level A). 3,4-Diaminopyridine is recommended as symptomatic treatment and IvIG has a positive short-term effect in LEMS (good practice point). Neuromyotonia patients should be treated with an antiepileptic drug that reduces peripheral nerve hyperexcitability (good practice point). For paraneoplastic LEMS and neuromyotonia optimal treatment of the underlying tumour is essential (good practice point). Immunosuppressive treatment of LEMS and neuromyotonia should be similar to MG (good practice point).

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.

Use of mycophenolate mofetil as a rescue agent in the treatment of severe generalized myasthenia gravis in three dogs

OBJECTIVE

To describe the use of IV and oral mycophenolate mofetil (MMF) as adjunctive therapy in 3 dogs with severe generalized myasthenia gravis.

CASE SERIES SUMMARY

Three dogs suffering from severe generalized myasthenia gravis as confirmed by acetylcholine antibody titers were treated with MMF as part of their treatment regimens. All 3 dogs had radiographic evidence of megaesophagus and suffered from severe regurgitation. Each dog was initially treated with pyridostigmine and supportive agents. When clinical remission was not achieved, IV MMF was administered to all dogs. Signs of clinical remission were apparent within 48 hours and all dogs were later maintained on oral MMF following resolution of regurgitation.

NEW OR UNIQUE INFORMATION PROVIDED

This is the first report of the use of IV MMF as adjunctive treatment in dogs with severe generalized myasthenia gravis. Outcome was favorable in all 3 dogs and no adverse effects were noted from the MMF.

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.

Mycophenolate mofetil – as an adjunctive immunosuppressive therapy in refractory myasthenia gravis: The Singapore experience

We report our experience, using mycophenolate mofetil (MyM) as an adjunctive immunosuppressive therapy in patients with severe, refractory and high dose steroid-dependent myasthenia gravis (MG). Five patients were commenced on MyM in addition to other immunosuppressive therapies. All had significant clinical improvement and no subsequent myasthenic crisis requiring intensive care unit admission. MyM was well tolerated and no serious adverse effects were observed. MyM is an effective adjunctive therapy for the treatment of severe, refractory and steroid-dependent MG in our experience.

Mycophenolate mofetil substitution for cyclosporine-dependent myasthenia gravis and nephrotoxicity

Severe autoimmune myasthenia gravis is difficult to manage and may require immunosuppression with cyclosporine. However, cyclosporine dependency is associated with the risk of nephrotoxicity. Mycophenolate mofetil is a non-nephrotoxic alternative which should be considered to rescue cyclosporine-dependent, severe myasthenia gravis sufferers with renal impairment from progression to end-stage renal failure. However, the evidence is limited and studies have not assessed the outcome of a direct substitution in these cyclosporine-dependent patients. We study three such patients who successfully converted to mycophenolate mofetil, and briefly examine the evidence behind this option. We believe that total cyclosporine withdrawal is feasible, but strongly recommend overlapping mycophenolate mofetil treatment with cyclosporine.

Guidelines for the treatment of autoimmune neuromuscular transmission disorders

Important progress has been made in our understanding of the cellular and molecular processes underlying the autoimmune neuromuscular transmission (NMT) disorders; myasthenia gravis (MG), Lambert-Eaton myasthenic syndrome (LEMS) and neuromyotonia (peripheral nerve hyperexcitability; Isaacs syndrome). To prepare consensus guidelines for the treatment of the autoimmune NMT disorders. References retrieved from MEDLINE, EMBASE and the Cochrane Library were considered and statements prepared and agreed on by disease experts and a patient representative. The proposed practical treatment guidelines are agreed upon by the Task Force: (i) Anticholinesterase drugs should be the first drug to be given in the management of MG (good practice point). (ii) Plasma exchange is recommended as a short-term treatment in MG, especially in severe cases to induce remission and in preparation for surgery (level B recommendation). (iii) Intravenous immunoglobulin (IvIg) and plasma exchange are equally effective for the treatment of MG exacerbations (level A Recommendation). (iv) For patients with non-thymomatous autoimmune MG, thymectomy (TE) is recommended as an option to increase the probability of remission or improvement (level B recommendation). (v) Once thymoma is diagnosed TE is indicated irrespective of the severity of MG (level A recommendation). (vi) Oral corticosteroids is a first choice drug when immunosuppressive drugs are necessary in MG (good practice point). (vii) In patients where long-term immunosuppression is necessary, azathioprine is recommended together with steroids to allow tapering the steroids to the lowest possible dose whilst maintaining azathioprine (level A recommendation). (viii) 3,4-diaminopyridine is recommended as symptomatic treatment and IvIg has a positive short-term effect in LEMS (good practice point). (ix) All neuromyotonia patients should be treated symptomatically with an anti-epileptic drug that reduces peripheral nerve hyperexcitability (good practice point). (x) Definitive management of paraneoplastic neuromyotonia and LEMS is treatment of the underlying tumour (good practice point). (xi) For immunosuppressive treatment of LEMS and NMT it is reasonable to adopt treatment procedures by analogy with MG (good practice point).

Basic immunosuppressive drugs outside solid organ transplantation

Immunosuppressive drugs are the backbone of solid organ transplantation. The introduction of new immunosuppressive drugs led to improved patient and organ survival rates. Nowadays, acute rejection can be reduced to a minimum. Individualization and avoidance of drug-related adverse effects became a new goal to achieve. The potency of immunosuppressive drugs makes them attractive for use in various autoimmune diseases; therefore, the experience on immunosuppressive drugs outside the field of organ transplantation is analysed in this review.

Mycophenolate mofetil and tacrolimus: New therapeutic options in neuroimmunological diseases

Mycophenolate mofetil (MMF) and tacrolimus are novel immunosuppressive drugs, both first established in transplantation medicine and now used increasingly in neuroimmunological diseases including myasthenia gravis, dysimmune polyneuropathies, and myositis. In myasthenia gravis, the efficacy and safety of MMF has been shown by one open-label trial; one small, double-blind, placebo-controlled trial; and a few retrospective analyses. Similarly, for tacrolimus the greatest experience and evidence for efficacy and safety have been gathered in myasthenia gravis. MMF and tacrolimus have both been used as an alternative treatment for various other autoimmune diseases in which azathioprine or cyclosporine were not sufficiently effective. However, experience with tacrolimus in dysimmune polyneuropathies and myositis is limited. At this time, the available data suggest that MMF and tacrolimus are well suited for long-term immunosuppression in patients with myasthenia gravis. The spectrum of neuroimmunological diseases in which these drugs may be used has not been finally delineated and will require further controlled studies.

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.

Inosine 5'-monophosphate dehydrogenase inhibition by mycophenolic acid impairs maturation and function of dendritic cells

BACKGROUND

The mechanism of action of mycophenolic acid (MPA) has been described as a blockade of inosine 5'-monophosphate dehydrogenase (IMPDH) and is thought to selectively influence T- and B-lymphocytes due to their strong dependency on guanine nucleotides synthesized via the de novo purine synthesis pathway. Recent evidence suggests MPA to affect antigen-presenting cells.

METHODS

Using CD14+ derived human dendritic cells (DC) we have investigated the effects of MPA on differentiation, maturation and function and studied intracellular nucleotide content and IMPDH activity.

RESULTS

GTP content and IMPDH activities of DC were strongly and dose-dependently decreased when MPA was present during the entire culture period or was added after the fifth (immature DC) or the seventh (mature DC) day of culture. Concurrent to low GTP levels, a dose-dependent reduction in the expression of CD80, CD86, CD40, CD54 and CD83 was seen which was accompanied by a decreased capacity of DC to stimulate T-cells. Our data for the first time shows a direct effect of MPA on the maturation and function of human CD14+ derived DC, indicates a role of IMPDH and a dependency on the de novo purine synthesis pathway.

Severe Skin Reaction Related to Mycophenolate Mofetil for Myasthenia Gravis

The authors report the development of a papulosquamous psoriatic-like skin eruption following the introduction of mycophenolate mofetil (MM) in a patient with myasthenia gravis (MG). MM is a novel and potent immunosuppressive agent that blocks purine synthesis, thus selectively inhibiting T and B lymphocyte proliferation. Favorable results in refractory and steroid-dependent MG patients have been reported in open-label studies, revealing a rapid onset of action and a safe side effect profile. Drug eruption due to toxicity or immune-mediated damage has not been reported in association with MM. A 32-year-old man with generalized seropositive MG with a highly malignant clinical course was admitted to the authors' department due to an acute papulosquamous, psoriatic-like skin eruption 1 month following treatment initiation with MM. Skin biopsy revealed sparse perivascular infiltrate of lymphocytes intermingled with few eosinophils. Treatment with high-dose steroids together with discontinuation of MM induced a gradual improvement, with complete resolution of the symptoms 2 months later. A severe and fulminant skin eruption in association with MM treatment is described for the first time in the literature. The histopathologic diagnosis of "drug eruption" is supported by the resolution of symptoms following discontinuation of MM. However, other possibilities include an immune-mediated process supported by the presence of lymphocytic infiltrations, the clinical appearance and the distribution of lesions (simulating a psoriatic-like dermatitis), as well as the marked response to steroids.

Mycophenolate Mofetil in Multiple Sclerosis

OBJECTIVE

To describe experience with the use of mycophenolate mofetil (MMF) in the treatment of multiple sclerosis (MS).

BACKGROUND

MMF is a potent immunosuppressant that is a selective inhibitor of inosine 5'-monophosphate dehydrogenase type II, the enzyme responsible for the de novo synthesis of the purine nucleotide guanine within activated T and B lymphocytes and macrophages.

METHODS

A retrospective review of experience in treating 79 MS patients with MMF (61 with secondary progressive, 14 with relapsing-remitting, and 4 with primary progressive MS) in the authors' MS center.

RESULTS

In most cases, MMF was added as adjunctive therapy in patients already being treated with either interferon-beta (n = 44) or glatiramer acetate (n = 20). Fifteen patients not able to use interferon or glatiramer acetate were treated with MMF monotherapy. Seventy percent of the patients continued MMF therapy. Eight patients discontinued therapy because of side effects, 7 patients continued to exhibit evidence of disease progression, 4 were denied insurance coverage, 2 were lost to follow-up, and 1 patient had an elevation of hepatic transaminases that resolved on discontinuation of MMF. One patient discontinued MMF therapy secondary to cytomegalovirus diarrhea.

CONCLUSION

MMF was well tolerated by the majority of patients treated. While these clinical observations were uncontrolled, the clinical course of MS was either unchanged or subjectively improved in many of the treated patients. A randomized controlled trial of MMF in MS, either as monotherapy or in conjunction with interferon or glatiramer acetate, appears warranted.

Mycophenolate in treatment-resistant inflammatory neuropathies

There has been an increasing interest in the use of mycophenolate as an immunomodulatory drug in neuromuscular diseases. We report five consecutive patients with treatment-resistant chronic inflammatory demyelinating polyradiculoneuropathy or multifocal motor neuropathy who were treated with mycophenolate. None showed clinically significant benefit. The use of mycophenolate did not result in the reduction in the dose of corticosteroid or other immunosuppressive agents in any patient. Side-effects, although not serious, were troubling enough for two patients to stop mycophenolate.

Treatment of myasthenia gravis: current practice and future directions

Myasthenia gravis is the best understood of the autoimmune diseases and a number of treatments are currently used to produce clinical improvement. However, due to the scarcity of evidence-based and comparative data, there is still no consensus on many therapeutic issues. Even a widely accepted treatment like thymectomy has never been proven effective by a well-designed trial. These are just some of the unanswered questions: What is the best treatment algorithm and safest long-term management of myasthenia gravis? What patients are likely to benefit from thymectomy? How long should myasthenia gravis patients be treated? Is it possible to discontinue immunotherapy once remission has been achieved? What are the risks associated with long-term immunosuppression? In this article, we review current therapeutic strategies and these unresolved questions about myasthenia gravis treatment.

Advances in myasthenia gravis

Recent advances in the diagnosis and treatment of acquired myasthenia gravis (MG) are reviewed. Increased awareness about the need for more uniform methods of reporting treatment trials for MG has prompted systematic review of the literature and inspired an effort to develop better classifications and disease-specific outcome measures. New antibodies have been discovered in patients with seronegative MG, possibly defining an immunologically distinct form of the disease. A new immunosuppressant, mycophenolate mofetil, may be an additional and safe option in the treatment of MG. Other work supports the possibility of developing a vaccine against MG suitable for trial in humans.

Myasthenia gravis: options and timing of immunomodulatory treatment

The autoimmune pathogenesis of myasthenia gravis is relatively well understood. The current options for treatment of this disease are acute and long term immunotherapies, acetylcholinesterase inhibitors and thymectomy. Many factors influence the timing of initiation of immunomodulatory therapy in myasthenia gravis and both disease factors, such as stage and severity, and patient factors, such as age, pregnancy and intercurrent illness, must be considered. Decisions regarding the choice of therapy can be difficult because of the limited number of randomised controlled trials that have been performed in myasthenic patients. In general, acetylcholinesterase inhibitors alone are used only in mild ocular disease, and in the majority of other patients immunomodulatory therapy is begun early. Corticosteroids are the most commonly used initial therapy, followed by azathioprine. In refractory cases, the available options include immunosuppressants such as cyclosporin, mycophenolate mofetil and cyclophosphamide. Plasmapheresis and intravenous immunoglobulin are important in the treatment of acute exacerbations and myasthenic crisis and in the perioperative setting. Despite many years of experience, the role of thymectomy in improving long term outcome in nonthymomatous myasthenia gravis remains controversial.

Mycophenolate (CellCept) treatment of myasthenia gravis, chronic inflammatory polyneuropathy and inclusion body myositis

We report favorable results of the long term use of mycophenolate in the treatment of three patients with myasthenia gravis (MG), two patients with chronic inflammatory demyelinating polyneuropathy (CIDP), one patient with secondary polymyositis (PM), and one patient with inclusion body myositis (IBM). Side effects were mild. Mycophenolate appears to be a useful addition to the armamentarium of immunosuppressants for treatment of chronic immunologically mediated neuromuscular diseases.

Treatment of myasthenia gravis with mycophenolate mofetil: a case report

We report a patient with myasthenia gravis (MG) who had marked clinical benefit in response to treatment with mycophenolate mofetil as documented by serial quantitative measures of strength and muscle fatigue. Our patient had experienced either adverse side effects or a suboptimal response to the usual immunosuppressive agents used in MG. Mycophenolate mofetil was used in combination with cyclosporine and prednisone and allowed for significant reductions in dosage of these immunosuppressants. We conclude that mycophenolate mofetil deserves further study as a therapeutic agent in MG. In particular, its role as a steroid-sparing agent and as a drug to be used in combination immunotherapy in more severe or refractory cases of MG should be investigated.

Mycophenolate mofetil and its mechanisms of action

Mycophenolate mofetil (MMF, CellCept(R)) is a prodrug of mycophenolic acid (MPA), an inhibitor of inosine monophosphate dehydrogenase (IMPDH). This is the rate-limiting enzyme in de novo synthesis of guanosine nucleotides. T- and B-lymphocytes are more dependent on this pathway than other cell types are. Moreover, MPA is a fivefold more potent inhibitor of the type II isoform of IMPDH, which is expressed in activated lymphocytes, than of the type I isoform of IMPDH, which is expressed in most cell types. MPA has therefore a more potent cytostatic effect on lymphocytes than on other cell types. This is the principal mechanism by which MPA exerts immunosuppressive effects. Three other mechanisms may also contribute to the efficacy of MPA in preventing allograft rejection and other applications. First, MPA can induce apoptosis of activated T-lymphocytes, which may eliminate clones of cells responding to antigenic stimulation. Second, by depleting guanosine nucleotides, MPA suppresses glycosylation and the expression of some adhesion molecules, thereby decreasing the recruitment of lymphocytes and monocytes into sites of inflammation and graft rejection. Third, by depleting guanosine nucleotides MPA also depletes tetrahydrobiopterin, a co-factor for the inducible form of nitric oxide synthase (iNOS). MPA therefore suppresses the production by iNOS of NO, and consequent tissue damage mediated by peroxynitrite. CellCept(R) suppresses T-lymphocytic responses to allogeneic cells and other antigens. The drug also suppresses primary, but not secondary, antibody responses. The efficacy of regimes including CellCept(R) in preventing allograft rejection, and in the treatment of rejection, is now firmly established. CellCept(R) is also efficacious in several experimental animal models of chronic rejection, and it is hoped that the drug will have the same effect in humans.