Efficacy and safety of efgartigimod in very-late-onset myasthenia gravis.

Background: Myasthenia gravis (MG) is an autoimmune disease. Recently, the prevalence of very late-onset MG (VLOMG; onset ≥ 65 years) has rapidly increased. The treatment of VLOMG groups is associated with several challenges, including multiple comorbidities, polypharmacy, and immunosenescence. Efgartigimod, which is the first approved neonatal Fc receptor (FcRN) antagonist, is reported to rapidly ameliorate MG symptoms with a favorable safety profile. Thus, efgartigimod is a potential novel therapeutic for VLOMG. Objective: This study retrospectively analyzed the clinical data of patients with VLOMG treated with efgartigimod at our center over the past two years to assess its long-term efficacy and safety. Methods: This study retrospectively enrolled 62 patients with VLOMG who received at least one efgartigimod treatment cycle. The primary efficacy outcomes were the proportion of patients achieving minimum symptom expression (MSE) and the reduction in glucocorticoid dosage. The secondary efficacy outcomes were changes in Myasthenia Gravis-Activities of Daily Living (MG-ADL) scale scores, Quantitative Myasthenia Gravis (QMG) scale scores, Myasthenia Gravis Quality of Life 15-item revised (MG-QoL15r) scale scores, and scores of key muscle groups (ocular, bulbar, respiratory, axial, and limb muscles) relative to baseline. Results: This study enrolled 62 eligible patients with VLOMG. Of these 62 patients, 37, 10, and 15 completed 1, 2, and ≥3 treatment cycles, respectively. The cumulative MSE achievement rate was 41.9% (26/62) by the end of the study. MG-ADL, QMG and MG-QoL15r scores after treatment were significantly reduced relatively to baseline in patients who underwent 1, 2, and ≥ 3 treatment cycles (all P < 0.001, P < 0.01, and P < 0.05, respectively). Subgroup analysis of muscle groups revealed that bulbar, limb (including axial), and ocular muscle function after treatment was significantly improved relatively to baseline in 37 patients (all P < 0.01). Limb (including axial) muscle function after treatment was significantly improved relatively to baseline in 15 patients (P < 0.05). Glucocorticoid dosage after treatment was significantly decreased relatively to baseline in patients who underwent 1, 2, and ≥ 3 treatment cycles (P < 0.0001, P < 0.05, P < 0.05, respectively). During treatment with efgartigimod, one patient developed an allergic rash, one patient experienced gastric discomfort, and two patients reported headache. Conclusion: This study demonstrated that efgartigimod effectively ameliorates symptoms and improves the quality of life in patients with VLOMG and enables short-term glucocorticoid dosage reduction. Thus, efgartigimod seems to be a safe and effective long-term therapeutic agent for VLOMG.