2023 NMSG Abstracts and Meeting Information

Introduction: Azathioprine is generally considered the first-line steroid-sparing immunosuppressive agent for myasthenia gravis (MG). Mycophenolate and methotrexate are often reserved as second-line choices due to lack of randomised controlled trial evidence, despite widespread consensus on their efficacy.Objectives: We aimed to gather real-world data on the side effects of steroid sparing agents, their use in United Kingdom (UK) clinical practice, and the reasons for discontinuation in the UK.Methods: We performed a national survey of side effects and reasons for discontinuation of immunosuppressants in patient with MG in the UK. 235 patients who completed the survey; 166 had taken azathioprine, 102 mycophenolate, and 40 methotrexate. Results: High proportions of patients reported side effects from their medications for MG; 90% of those on prednisolone, 79% pyridostigmine, 78% azathioprine, 62% methotrexate, and 60% mycophenolate. Side effects of treatments for MG led to admission to accident and emergency (n=7) or hospital (n=33) in 17% of patients.Azathioprine was discontinued by 66% of patients who started it (53% of these due to side effects), compared to only 19% mycophenolate (26%), and 32% methotrexate (25%). Azathioprine was significantly more likely to be discontinued than mycophenolate due to side effects (p<0.0001). There was no significant difference in treatment cessation due to lack of effect. Conclusions: This real world data highlights the significant burden of treatment for MG. Mycophenolate appears to be better tolerated than azathioprine. Strategies to optimise azathioprine dosing such as azathioprine metabolite testing should be utilized to reduce the risk of treatment failure.