Patterns and predictors of therapeutic response to efgartigimod in acetylcholine receptor-antibody generalized myasthenia gravis subtypes

Background: Efgartigimod is an approved biologic for generalized myasthenia gravis (gMG), which is an autoimmune disease and can potentially be life-threatening. However, the therapeutic response to efgartigimod among the acetylcholine receptor gMG (AChR-gMG) subtypes remains inconclusive. Objective: To explore the patterns and predictors for the therapeutic response to efgartigimod among AChR-gMG subtypes. Design: This prospective, observational study included AChR-gMG patients treated with efgartigimod at 15 centers in China with a follow-up for at least 20 weeks. Methods: The primary outcome was the proportion of minimal symptom expression (MSE) responders, denoted by a Myasthenia Gravis Activities of Daily Living (MG-ADL) score of 0 or 1 within 4 weeks and maintained for ⩾4 weeks. AChR antibody-positive MG (AChR-MG) subtypes were classified into early onset myasthenia gravis (EOMG), late-onset myasthenia gravis (LOMG), and thymoma-associated myasthenia gravis (TAMG). The predictive factors for MSE responders were identified by univariate and multivariate logistic regression analysis. Results: One hundred sixteen patients were included with a median follow-up duration of 238 days (172.5–306.3). There were 50 (43.1%) patients with EOMG, 28 (24.1%) with LOMG and 38 (32.8%) with TAMG. After efgartigimod initiation, 35 (30.2%) patients were MSE responders, and the proportion of MSE responders was highest in the LOMG group (42.9%). The MG-ADL score reduction in the LOMG group was more significant than in the EOMG group by weeks 16 and 20 (both p = 0.022). Response patterns to efgartigimod among the AChR-MG subtypes differed as measured by the proportion of improved patients and MSE. LOMG presented sustained symptom control, while EOMG and TAMG showed more fluctuations. Eight TAMG patients (21.1%) switched to another biologic ( p = 0.005). Baseline MG-ADL was an independent predictor for therapeutic response to efgartigimod ( p < 0.001). Conclusion: Our findings revealed patterns of treatment responses among AChR-gMG subtypes, with LOMG patients potentially presenting a more sustained response. These findings likely provide preliminary data for precision therapy in MG in the era of biologics. Trial registration: NCT04535843.