Efficacy of azathioprine and mycophenolate mofetil in acetylcholine receptor antibody positive generalized myasthenia gravis patients

Abstract

Background & Objective: Corticosteroids are the first-line immunosuppressive drug. Azathioprine and mycophenolate mofetil are commonly used as steroid-sparing agents or additional immunosuppressive drugs. However, the efficacies of azathioprine and mycophenolate mofetil are lacking, especially in acetylcholine receptor antibody-positive generalized myasthenia gravis patients (AChR Ab-positive generalized MG). The objectives are firstly to determine the efficacy of azathioprine in AChR Ab- positive generalized MG patients; and secondly to determine the efficacy of mycophenolate mofetil in patients who did not respond or were intolerant to azathioprine.

Methods: A retrospective study of AChR Ab-positive generalized MG patients who were treated with prednisolone in combination with azathioprine and who had switched treatment from azathioprine to mycophenolate mofetil was conducted. Treatment response and adverse effects were evaluated.

Results: Of 105 patients, 95 patients (90.5%) could tolerate and respond to prednisolone in combination with azathioprine, 6 patients (5.7%) had adverse effects, and 4 patients (3.8%) did not respond to azathioprine. Patients who had adverse effects or did not respond to azathioprine were switched to mycophenolate mofetil. Of the 105 patients, 7.6% had MGFA Post-intervention Status (MGFA-PIS) at the last follow-up or before switching from azathioprine to mycophenolate mofetil as Complete Stable Remission (CSR), 2.9% as Pharmacologic Remission (PR), 10.5% as Minimal Manifestations -1 (MM-1), 30.4% as MM-2, 48.6% as MM-3 and the median Medical Research Council (MRC) sum score was 60.0 points. Ten of the 105 patients were switched from azathioprine to mycophenolate mofetil. MGFA-PIS was better after switching treatments in these ten patients than that before the switching.

Conclusion: This study supports the efficacy and safety of azathioprine as an additional immunosuppressive drug in combination with prednisolone for treatment in AChR Ab-positive generalized MG patients. Mycophenolate mofetil can be considered as alternative immunosuppressive drug for patients who cannot tolerate adverse effects or have no response to azathioprine.