Efficacy and safety of efgartigimod versus intravenous immunoglobulin in early intervention of acetylcholine receptor antibody-positive impending myasthenic crisis: A retrospective cohort study

Early intervention in impending myasthenic crisis (IMC) is critical to avert life-threatening progression. This study compared the clinical effectiveness and safety of the novel FcRn antagonist efgartigimod versus intravenous immunoglobulin (IVIg) in IMC management. In this retrospective cohort study, we analyzed 51 acetylcholine receptor antibody-positive (AChR-Ab+) IMC patients who received either efgartigimod (n ​= ​30) or IVIg (n ​= ​21) from June 2023 to November 2024. Efficacy was assessed based on changes in Myasthenia Gravis Activities of Daily Living (MG-ADL) and Quantitative Myasthenia Gravis (QMG) scores over four weeks. From weeks 2-4, the efgartigimod group showed significantly greater improvements in MG-ADL and QMG scores (both P ​< ​0.05), with a similar trend after baseline adjustment. By week 4, the results of the clinically meaningful improvement (CMI) analysis indicated that a higher proportion of patients in the efgartigimod group achieved MG-ADL improvement ≥7 points (90.0 ​% vs. 57.1 ​%) and greater QMG scores improvement. The proportion of patients reaching minimal symptom expression (MSE) was 80.0 ​% in the efgartigimod group compared to 14.3 ​% in the IVIg group, with mean improvement rates of 91.5 ​% vs. 60.7 ​%, respectively. One case of myasthenic crisis-related death occurred in the IVIg group, while no severe adverse events were reported in the remaining patients. Efgartigimod has been shown to effectively alleviate IMC symptoms, prevent progression to myasthenic crisis (MC), and significantly reduce in complications without substantially increasing the economic costs. These findings suggest its potential as a first-line therapeutic option for AChR-Ab-positive IMC patients.