Factors associated with early response to efgartigimod in patients with generalized myasthenia gravis: a multicenter retrospective observational study.

Background and purpose: Efgartigimod has demonstrated efficacy in generalized myasthenia gravis (gMG) in both clinical trials and real-world studies. However, factors influencing early response have been less reported. This study aimed to evaluate the efficacy of efgartigimod in a multicenter gMG cohort and to identify the clinical factors associated with early therapeutic response.

Methods: This multicenter, real-world, retrospective, observational study included 115 gMG patients administered efgartigimod across four myasthenia gravis (MG) centers. Responders were defined as patients with a ≥ 2-point Myasthenia Gravis Activities of Daily Living (MG-ADL) or ≥ 3-point Quantitative Myasthenia Gravis Score (QMG) score reduction, while early responders were those achieving score reductions after the first infusion. Subgroup analyses were conducted based on immunosuppressant (IST) use. Logistic regression analysis was performed to identify factors associated with response to first efgartigimod infusion according to MG-ADL or QMG scores reduction. Variables were compared between responders and non-responders to identify early response factors.

Results: After the first infusion, 72.5% of patients achieved improvement in MG-ADL and 60.5% in QMG, with these rates increasing to 93.3% and 87.5% respectively by the fourth infusion. Efgartigimod demonstrated the most significant improvement in bulbar, limb, and ocular symptoms; however, there was no statistically significant improvement in respiratory symptoms occurred during the initial 4-week treatment period. Multivariate logistic analysis showed that short disease duration and high MG-ADL bulbar score at baseline indicated early response. High QMG bulbar score at baseline also indicated early response. Efficacy was independent of IST use. No patients discontinued treatment due to severe adverse events; minor side effects were not recorded.

Conclusions: Efgartigimod demonstrated robust efficacy in gMG patients. Early response was linked to shorter disease duration and severe bulbar symptoms, which promotes the identification of patients who are likely to benefit quickly from efgartigimod.