Rituximab in AChR and MusK Myasthenia Gravis: long-term follow-up with different therapeutic protocols

The objective of this study was to describe a real-world, single-center experience with the long-term efficacy and safety of rituximab therapy in patients with generalized Myasthenia Gravis. Forty-four patients (AChR n = 22, MusK n = 22) with refractory myasthenia gravis or inadequate disease control were treated with rituximab from January 2009 to May 2025. A subset of anti-Musk MG patients received a low-dose protocol. The primary endpoint was the Myasthenia Gravis Foundation of America post-intervention status success. Secondary endpoints included changes in Myasthenia Gravis activities of daily living over time, responder status, and time to reduced or discontinued steroid therapy. At 60 months, 33.3% of the AChR and 66.7% of the MusK group achieved success in post-intervention status. Additionally, 76.2% of the AChR group and 90.9% of the MusK group decreased steroid doses, reaching the target of 10 mg/day or less at one year and six months, respectively. Stable steroid discontinuation was possible in 42.9% of the AChR group (median time: 84 months) and 68.2% of the MusK group (median time: 12 months). Within the MusK subgroup, treatment response was consistently higher in the 1000 mg group. However, both dosing strategies resulted in significant clinical improvements, and time-to-event steroid outcomes did not differ substantially by dose. MusK serotype was the only significant predictor of treatment success. No serious adverse events occurred during long-term follow-up. This study provides real-world, long-term data on the effectiveness and safety of rituximab in treating generalized myasthenia gravis with either anti-AChR or MusK antibodies.