Mycophenolate mofetil in myasthenia gravis: the unanswered question

Comparative effectiveness clinical trials to advance treatment of myasthenia gravis

Myasthenia gravis (MG) presents many challenges for establishing treatment efficacy through clinical trials. Among these are the rarity and heterogeneity of the disease, spontaneous fluctuations, prolonged latency to effect for many immunosuppressive drugs, and the uncertain generalizability of results from randomized controlled trials (RCTs). Prospective observational study designs may overcome some of these limitations, but attention is required to ensure that internal validity is not compromised. Observational comparative effectiveness research (CER) utilizes data obtained during routine clinical care to evaluate the effectiveness of interventions in real-life practice conditions, thereby improving generalizability to the clinic. Compared with RCTs, observational CER studies may be less resource intensive and costly. Recent advances that have improved the feasibility of CER studies for MG are (1) the development of MG common data elements, (2) the publication of international consensus guidance for MG treatment, and (3) the development of a web-based REDCap database that can be shared and adapted to standardize data collection. This infrastructure could be used for multisite comparisons of commonly used therapies and provides longitudinal information on patient- and clinician-centered MG outcome measures. A challenge is to design studies that address the potential limitations of observational trials, such as confounding and selection and information bias.

Current and emerging treatments for the management of myasthenia gravis

Myasthenia gravis is an autoimmune neuromuscular disorder. There are several treatment options, including symptomatic treatment (acetylcholinesterase inhibitors), short-term immunosuppression (corticosteroids), long-term immunosuppression (azathioprine, cyclosporine, cyclophosphamide, methotrexate, mycophenolate mofetil, rituximab, tacrolimus), rapid acting short-term immunomodulation (intravenous immunoglobulin, plasma exchange), and long-term immunomodulation (thymectomy). This review explores in detail these different treatment options. Potential future treatments are also discussed.

Immunosuppressive therapies in myasthenia gravis

Immunosuppression is the mainstay of treatment for myasthenia gravis (MG). In this paper, we review the mechanisms of action and clinical application of corticosteroids and different classes of immunosuppressive drugs that are currently used in MG patients, and present the results of their use in more than 1000 patients with MG seen at our two centers. Immunosuppressive treatment was considered along with, or as an alternative to thymectomy in MG patients with disabling weakness, not adequately controlled with anticholinesterase drugs. Overall, 82% of our patients received immunosuppressants for at least 1 year, with frequencies varying according to disease severity, from 93-95% of those with thymoma or MuSK antibodies to 72% in ocular myasthenia. Prednisone was used in the great majority of patients, azathioprine was the first-choice immunosuppressant; mycophenolate mofetil and cyclosporine were used as second-choice agents. All clinical forms of MG benefited from immunosuppression: the rate of remission or minimal manifestations ranged from 85% in ocular myasthenia to 47% in thymoma-associated disease. Treatment was ultimately withdrawn in nearly 20% of anti-AChR positive early-onset patients, but in only 7% of thymoma cases. The risk of complications appears to depend on drug dosage, treatment duration, and patient characteristics, the highest rate of serious side effects (20%) having been found in late-onset MG and the lowest (4%) in early-onset disease. Although nonspecific, current immunosuppressive treatment is highly effective in most MG patients. Lack of randomized evidence, the need for prolonged administration, and unwanted effects are still relevant limitations to its use.