Safety Profile Overview of Efgartigimod Clinical Trials in Participants With Diverse IgG-Mediated Autoimmune Diseases

Background: Efgartigimod is a human IgG1 antibody Fc-fragment that reduces IgG autoantibody levels through FcRn blockade. This study reports safety of efgartigimod across IgG-mediated disorders. Methods: The safety of intravenous efgartigimod was evaluated in 204 efgartigimod-treated subjects with generalized myasthenia gravis (phase 3 ADAPT and 3-year open-label extension ADAPT+ trials), primary immune thrombocytopenia (phase 3 ADVANCE trial), or pemphigus (open-label phase 2 trial). These studies examined different efgartigimod doses (10–25 mg/kg), including cyclical dosing in generalized myasthenia gravis and continuous weekly dosing in primary immune thrombocytopenia and pemphigus. Results: Across all indications and doses studied, efgartigimod demonstrated a consistent safety profile, with treatment-emergent adverse event (TEAE) rates comparable to placebo (ADAPT, 77.4% efgartigimod/84.3% placebo; ADVANCE, 93.0% efgartigimod/95.6% placebo; and 85% in the pemphigus study). Most TEAEs were mild to moderate in severity. Discontinuation rates due to adverse events were consistently low (ADAPT, 3.6% efgartigimod/3.6% placebo; ADVANCE, 3.5% efgartigimod/2.2% placebo; and 3% of pemphigus study participants). In ADAPT+, no increases in TEAEs or infections occurred with additional efgartigimod dosing (19 cycles). Conclusions: Efgartigimod was well tolerated across indications and doses studied. Most TEAEs, including infections, were mild or moderate in severity and did not increase in frequency with recurrent dosing.