Efficacy and safety of efgartigimod in the treatment of impending myasthenic crisis

Objective To compare the short-term efficacy and safety of efgartigimod versus intravenous immunoglobulin (IVIg) in patients with impending myasthenic crisis (IMC). Methods This single-center, randomized, open-label, prospective comparative cohort study included 38 acetylcholine receptor antibody–positive (AChR−Ab+) patients with IMC, which was defined as rapid progression of bulbar or respiratory symptoms within ≤2 weeks, meeting at least one of the following criteria:Myasthenia Gravis Foundation of America (MGFA) grade IVb, a Quantitative Myasthenia Gravis (QMG) bulbar subscore of 3, a respiratory subscore of 2, or a combined bulbar–respiratory subscore ≥4. The participants were included and categorized into either the efgartigimod group (n=21; 10 mg/kg weekly for 4 weeks) or the IVIg group (n=17; 400 mg/kg/day for 5 days). The primary endpoints were the rate of IMC remission within one month (defined as a QMG score 2 for both the bulbar and respiratory items, or a combined bulbar plus respiratory QMG score 4, or an improvement of the MGFA classification to below class IVb, sustained for at least 24 hours.) and time to remission. Secondary outcomes comprised changes in QMG total, bulbar, and respiratory subscores, and Myasthenia Gravis Activities of Daily Living (MG-ADL) from baseline to remission. Safety was assessed by rates of progression to myasthenic crisis (MC) and treatment-emergent adverse events (TEAEs). Results Between January 2024 and March 2025, 38 patients were randomized. IMC remission rates were 90.48% with efgartigimod and 94.12% with IVIg (P = 1.000). The median time to remission was significantly shorter with efgartigimod (8 days; 95% CI: 5.75–10.67) than with IVIg (12 days; 95% CI: 9.92–13.20; P = 0.009). One patient per group progressed to myasthenic crisis (4.76% vs 5.88%). No TEAEs were reported. Conclusion Efgartigimod demonstrated comparable efficacy to IVIg for IMC remission but with a significantly faster onset, supporting its role as a rapid and safe alternative.