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

Immunosuppressive agents for myasthenia gravis

BACKGROUND

The benefits of different immunosuppressants for myasthenia gravis (MG) are unclear.

OBJECTIVES

Assessment of immunosuppressant drug efficacy in MG.

SEARCH STRATEGY

We searched the Cochrane Neuromuscular Disease Group Trials Register, MEDLINE (from January 1966 to July 2007), EMBASE (from January 1980 to July 2007), review and trial bibliographies and contacted trial authors.

SELECTION CRITERIA

Types of studies: Randomised and quasi-randomised controlled trials.

TYPES OF PARTICIPANTS

Any age, any type or severity of MG regardless of concomitant treatment. Types of interventions: Any immunosuppressive agent. Types of outcome measures: Primary: (1) Improvement or not at six months. Secondary: (1) Improvement or not at one year (2) Need for other treatment, for example corticosteroid dose, at six months (3) Number of exacerbations during the first year (4) Acetylcholine receptor antibody titre after at least six months (5) Occurrence of one or more adverse events at any time after the introduction of treatment.

DATA COLLECTION AND ANALYSIS

One author extracted and two checked the data.

MAIN RESULTS

Seven trials are included but few reported the outcomes selected for this review. A meta-analysis of ciclosporin versus placebo from two trials (59 participants) - one as monotherapy (20 participants) and the other with corticosteroids (39 participants) - showed that it resulted in improvement of participants in the ciclosporin group compared with those in the placebo group, with a relative rate of improvement of 2.44 (95% confidence interval (CI) 1.13 to 5.27). In addition the weighted mean difference in QMG score between the ciclosporin and placebo groups was -0.34 (95% CI -0.52 to -0.17). Azathioprine (plus prednisolone for first month) had no significant benefit over prednisolone alone (41 participants). The effects of azathioprine plus prednisolone versus prednisolone plus placebo were similar (34 participants). Cyclophosphamide was reported to be statistically more efficacious than placebo at 12 months in corticosteroid-dependent participants (23 participants), but no raw data were available. Trials of mycophenolate mofetil and tacrolimus did not provide relevant endpoint data for this review. All trials had low numbers of participants. Adverse event reporting was variable. Trial protocol heterogeneity prevented comparison of the different immunosuppressants.

AUTHORS' CONCLUSIONS

In generalised MG, limited evidence from small RCTs suggests that ciclosporin, as monotherapy or with corticosteroids, or cyclophosphamide with corticosteroids, significantly improve MG.Limited evidence from RCTs shows no significant benefit from azathioprine (as monotherapy or with steroids), mycophenolate mofetil (as monotherapy or with either corticosteroids or ciclosporin) or tacrolimus (with corticosteroids or plasma exchange). Bigger, better-designed, longer trials are needed.

IMPDH1 gene polymorphisms and association with acute rejection in renal transplant patients

Inosine 5'-monophosphate dehydrogenase 1 (IMPDH1) catalyzes the rate-limiting step of the de novo pathway for purine synthesis and is a major target of the immunosuppressive drug mycophenolic acid (MPA). Few variants of the IMPDH1 gene have been reported. The objective of this study was to identify and characterize IMPDH1 variants to determine whether genetic variation contributes to differences in MPA response and toxicity in transplant patients. Seventeen genetic variants were identified in the IMPDH1 gene with allele frequencies ranging from 0.2 to 42.7%. In this study, 191 kidney transplant patients who received mycophenolate mofetil were genotyped for IMPDH1. Two single-nucleotide polymorphisms, rs2278293 and rs2278294, were significantly associated with the incidence of biopsy-proven acute rejection in the first year post-transplantation. Future studies of the multifactorial nature of acute rejection must consider IMPDH1 polymorphisms in MPA-treated patients.

Diagnosis and treatment of myasthenia gravis

OBJECTIVE

To describe the clinical presentation, diagnosis, and treatment of myasthenia gravis (MG) while emphasizing the important role of the pharmacist.

DATA SOURCES

English-language articles from MEDLINE pertinent to MG study selection and data extraction: All relevant publications addressing MG management were considered, including prospective comparative trials, epidemiological studies, guideline statements, review articles, and editorials. Particular focus occurred on primary literature published after 1976, but limited amount(s) existed. The American Autoimmune Related Diseases Association, Autoimmune Information Network, Inc., Myasthenia Gravis Foundation of America, Inc. (MGFA), National Institute of Neurological Disorders and Stroke, and National Organization for Rare Disorders.

DATA SYNTHESIS

MG is an autoimmune disorder involving the neuromuscular junction causing characteristic weakness in voluntary muscle groups. To determine appropriate pharmacotherapy, one must characterize the disease based on the degree of function and region of muscles affected. MGFA established a classification system of the disease in order to assess severity. Contemporary treatments include cholinesterase inhibitors, corticosteroids, immodulating/immunosuppressive therapy, intravenous immune globulin, plasmapheresis, and thymectomy. Because of the lack of double-blind, placebo-controlled, randomized clinical trials, treatments are less evidence-based than many other disease states. Clinicians should be aware of the different treatments and recognize the best treatment for the individual.

CONCLUSIONS

The diagnosis and treatment of MG is a therapeutic challenge. Pharmacists play an essential role in the care of these patients by avoiding drugs that exacerbate the disease, promoting optimal pharmacotherapy, monitoring pharmacotherapy, and ensuring compliance with prescribed medications.

A novel variant L263F in human inosine 5'-monophosphate dehydrogenase 2 is associated with diminished enzyme activity

BACKGROUND AND OBJECTIVE

Inosine 5'-monophosphate dehydrogenase 2 is required for purine synthesis in activated lymphocytes. Variants in the IMPDH2 gene may account for the large inter-individual variability in baseline enzyme activity, immunosuppressive efficacy and side effects in transplant recipients receiving mycophenolic acid. Therefore, the objective of this study was to identify and functionally characterize IMPDH2 variants.

METHODS

DNA samples from 152 solid organ transplant patients were screened at exons and exon/intron junctions of the IMPDH2 genes by PCR amplification followed by bidirectional direct DNA sequencing. Genetic variant was constructed by site-directed mutagenesis and transformed to an inosine 5'-monophosphate dehydrogenase-deficient strain of Escherichia coli h712. Proteins were purified to homogeneity and the enzymatic activity was measured by reduced nicotinamide adenine dinucleotide production.

RESULTS

Nine genetic variants were identified in the IMPDH2 gene, with frequencies of the rarer alleles ranging from 0.5 to 10.2%. A novel nonsynonymous variant L263F was identified, and the kinetic assay demonstrated that the inosine 5'-monophosphate dehydrogenase activity of L263F variant was decreased to 10% of the wild-type. The Ki for mycophenolic acid inhibition of the L263F variant was comparable with the wild-type, and the variant Km for inosine 5'-monophosphate and nicotinamide adenine dinucleotide did not change significantly.

CONCLUSIONS

IMPDH2 has low genetic diversity, but the nonsynonymous variant L263F has a significant impact on inosine 5'-monophosphate dehydrogenase activity. This novel functional variant may be one of the factors contributing to the inter-individual difference of baseline inosine 5'-monophosphate dehydrogenase activity as well as drug efficacy and adverse events in transplant patients.

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.

Ocular myasthenia: diagnosis, treatment, and pathogenesis

BACKGROUND

Although myasthenia gravis (MG) is often considered the best-understood autoimmune disorder and effective treatments have controlled life-threatening complications, the pathogenesis of ocular myasthenia (OM) remains enigmatic, and its clinical consequences offer therapeutic challenges.

REVIEW SUMMARY

About half of patients with MG present with visual complaints of droopy eyelids or double vision, and many will remain with purely ocular muscle weakness without generalized weakness, defined as OM. OM may be confused with disorders of the brainstem, ocular motor nerves, and eye muscles. Frustrating for the clinician, confirmatory tests such as the edrophonium test, serum acetylcholine receptor antibodies, and standard electrodiagnostic evaluations may fail to positively identify the clinical suspicion of OM. Patients may derive relief from nonpharmacologic interventions and cholinesterase inhibitors, but most will desire better symptom control with corticosteroids or need other immunosuppression. Early corticosteroid therapy may reduce the probability of generalization of the disease. The reasons for ocular muscle involvement by OM include physiologic and cellular properties of the ocular motor system and the unique immunology of OM, which, when better understood, will lead to novel treatments.

CONCLUSIONS

OM is a challenging disorder for the clinician and scientist, with both learning from the other for the betterment of the patient. The future requires answers to why the ocular muscles are so frequently involved by MG, whether the generalization of the disease may be limited by early corticosteroid treatment, and what treatment options may be developed which will improve symptoms without long-term complications.

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.

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.

A review of the medical management of chronic inflammatory demyelinating polyradiculoneuropathy

Chronic idiopathic demyelinating polyradiculoneuropathy (CIDP) is a rare condition, but merits consideration due to its disabling consequences for patients and the growing existence of efficacious therapies during the last few decades. The first step is to characterise this neuropathy among the chronic dysimmune polyneuropathies, according to clinical, electrophysiologicalal and sometimes pathologicalal and immunochemical criteria. Typical CIDP is currently defined by criteria which have progressively improved since the first attempt made by an Ad Hoc Subcommittee of the American Academy of Neurology in 1991. However, CIDP may be associated with several concurrent diseases, and other chronic demyelinating polyneuropathies may be considered as either subtypes of CIDP, such as sensory CIDP and multifocal acquired sensory and motor neuropathy, or frontiers of CIDP, such as multi-focal motor neuropathy and polyneuropathy associated with monoclonal gammopathy. These considerations are helpful in the choice of treatments, as the response to immunomodulatory agents is different according to the type of the dysimmune neuropathy. CIDP is considered to be an immune-mediated disorder and may respond dramatically to numerous short-term therapies, such as corticosteroids, plasma exchanges, or intravenous immunoglobulin. The aim of this review is both to summarise the main results of the published open and randomised controlled trials for CIDP, and to provide some information about randomised controlled trials currently in progress. The objectives of the current and future trials are firstly, to choose the best regimen for short-term treatments, and secondly, to test new immunosuppressants in long-term therapy, if the neurological condition requires it.

An Update on Myasthenic Crisis

Myasthenia gravis (MG) is the most common disorder of the neuromuscular junction. Myasthenia crisis, defined as respiratory failure requiring mechanical ventilation in MG, is a common life-threatening complication that occurs in approximately 15% to 20% of patients with MG during their life time. The advent of effective mechanical ventilation, specialized neurointensive care units and the widespread use of immunotherapies have substantially altered the prognosis of myasthenic crisis. Early intubation and mechanical ventilation is perhaps the most important step in the management of myasthenic crisis. The authors favor an orotracheal approach for intubation, and placement of small bore duodenal tubes that may help decrease the risk of aspiration and may be more comfortable than regular nasogastric tubes for the patient. Plasma exchange may be more effective than the intravenous immunoglobulin in the treatment of myasthenic crisis involving respiratory failure. A randomized trial is required to confirm the superior efficacy of plasma exchange compared with intravenous immunoglobulin. In the acute setting, the role of immunosuppression and intravenous/intramuscular pyridostigmine and the newer agents such as tacrolimus remains limited and at times controversial. The therapy should be tailored at an individual basis using best clinical judgment.

Update on myasthenia gravis

Myasthenia gravis is an autoimmune disorder caused by autoantibodies against the nicotinic acetylcholine receptor on the postsynaptic membrane at the neuromuscular junction and characterised by weakness and fatigability of the voluntary muscles. It has a bimodal peak of incidence with first peak in the third decade and the second peak in the sixth decade. It is probably underdiagnosed in the very old population. Our understanding of the pathogenesis, immunology, and molecular biology of myasthenia gravis has greatly improved in last three decades. It is almost always possible to establish the diagnosis of myasthenia gravis with the current tests. The modern treatment is highly successful and the mortality of treated myasthenia gravis is practically zero. However, there are still important gaps in our knowledge of the origin of myasthenia gravis, the factors that contribute to chronic disease, and the way to cure the disease. In this article the current knowledge of the various aspects of myasthenia gravis are outlined.

Autoimmune Myasthenia Gravis: Recommendations for Treatment and Immunologic Modulation

Treatment for myasthenia gravis should be individualized to each patient based on the clinical characteristics of myasthenia including the distribution, duration, and severity of weakness and resulting functional impairment; the risks for treatment complications related to age, gender, and medical comorbidities; and the presence of thymoma. Acetylcholinesterase inhibitors provide temporary, symptomatic treatment for all forms of myasthenia gravis. Immune modulators address the underlying autoimmune process in myasthenia gravis, but are associated with potential complications and side effects. Most patients with generalized myasthenia who have significant weakness beyond the ocular muscles and who remain symptomatic, despite treatment with cholinesterase inhibitors, are candidates for immune modulation. Although corticosteroids are effective for long-term immune modulation in myasthenia gravis, several more contemporary immunomodulators including azathioprine, cyclosporine, and mycophenolate mofetil have shown efficacy in myasthenia gravis and are used increasingly as first-line treatments and as steroid-sparing agents. Plasma exchange is used to achieve rapid improvement in patients with myasthenic crisis or exacerbation, to improve strength before a surgical procedure or thymectomy, and to minimize steroid-induced exacerbation in patients with oropharyngeal or respiratory muscle weakness. Intravenous immunoglobulin represents an alternative to plasma exchange in patients requiring relatively rapid short-term improvement in the setting of poor venous access. Because of a lack of controlled trials, the role of thymectomy in nonthymomatous myasthenia gravis is unclear, although evidence suggests that thymectomy increases the probability for myasthenic remission or improvement.

Ocular myasthenia gravis

Myasthenia gravis (MG) is an autoimmune disorder characterized clinically by proximal weakness and bulbar symptoms and pathologically by damage to the post-synaptic membrane at the neuromuscular junction. Ocular myasthenia gravis (ocular MG) is a form of myasthenia gravis whereby the patients' weakness is limited to the muscles of the eyes and eyelids (levator palpebrae superioris). Although not life-threatening, the limitations posed by ocular myasthenia gravis can prove disabling and distressing to patients. Acetylcholinesterase inhibitors such as pyridostigmine or neostigmine are the preferred first-line treatment for ocular myasthenia gravis, with mild cases requiring no additional intervention. However, in moderate or severe cases, treatment must be tailored to the needs and desires of the patient. Intravenous immunoglobulin, although costly, is safe and effective at treating MG. Corticosteroids are effective at reducing or eliminating symptoms and may modify the long-term course of the illness. Steroid-sparing agents such as azathioprine and mycophenolate mofetil are reasonably safe and well-tolerated alternatives to steroids. Surgical interventions such as strabismus surgery and eyelid suspension serve to correct impairments refractory to medical management. Thymectomy, although less frequently recommended, is a reasonable consideration, especially for young adults, given the potential for long-term benefit.

Treatment review and update for myasthenia gravis

Myasthenia gravis (MG) is the best understood autoimmune disease, with well-characterized humoral and cellular effector mechanisms. It is not surprising, therefore, that immunotherapies play a key role in the management of MG. Significant progress has been made over the last few decades in the treatment of patients with MG, and the number of effective avenues of therapy continue to increase. In this review, we provide an update on management options in MG, highlighting recent literature on both traditional and more novel approaches.

Myasthenia Gravis

Myasthenia gravis is a disorder of neuromuscular transmission, manifest by variable weakness of skeletal muscle. The disorder has a range of therapies that differ with respect to efficacy, timing, and side effects. The physician treating myasthenia gravis must be well versed in understanding the evidence basis for using these agents, as well as the trade-offs between persistent disease manifestations and their costs and expected benefits. Diagnosis of myasthenia gravis depends on recognizing the pattern of weakness, which typically involves some combination of extraocular, bulbar, facial, limb, and neck muscles. Management relies on some combination of medications that influence the function of the neuromuscular junction and treatments that alter the immune response. Thymectomy is commonly used, although trends in evidence-based medicine are leading expert clinicians to look closely at its efficacy. Plasma exchange is useful for patients in crisis, who require rapid improvement. The exact role for high-dose intravenous immunoglobulin in this setting is still being studied, although the agent is gaining popularity. Knowing that the treatments are effective is not enough. It is still important to determine the treatment that has a more rapid onset, because these patients often require intensive care or respiratory assistance.

Mycophenolate mofetil for myasthenia gravis: an analysis of efficacy, safety, and tolerability

The authors report a retrospective analysis of the use of mycophenolate mofetil (MyM) in 85 patients with autoimmune myasthenia gravis. The Myasthenia Gravis Foundation of America (MGFA) postintervention status (PIS) was used to characterize the treatment response in each patient. Sixty-two patients (73%) achieved a PIS status indicating improvement. Quantitative strength testing performed on the majority of patients before and after treatment also improved. Side effects to MyM were observed in 27% of patients but required discontinuation in only 6%.

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.

Single Fiber EMG as an Outcome Measure in Myasthenia Gravis: Results from a Double-Blind, Placebo-Controlled Trial

In a placebo-controlled, therapeutic, pilot trial of mycophenolate mofetil (MM) in autoimmune myasthenia gravis (MG), the authors compared pretreatment and posttreatment single fiber electromyography (SFEMG) jitter measurements performed on the same muscle in a total of 11 patients. The mean jitter value decreased (improved) by an average of 15.4 micros in patients receiving MM (n = 6), compared to an increase (worsening) in mean jitter of 4.0 micros in patients receiving placebo (n = 5). This difference was statistically significant (P = 0.030). In most patients, the change in SFEMG measurements correlated with the change in clinical state as measured by quantitative testing of muscle function. The authors conclude that immunomodulation by MM improves neuromuscular junction function in MG and that SFEMG may be a useful marker of early response in future therapeutic trials in autoimmune MG.