584 Overview of the safety profile of efgartigimod from clinical trials in participants with diverse IgG–mediated autoimmune diseases

This study evaluated the safety profile of efgartigimod (EFG), an Fc receptor inhibitor, across different IgG-mediated disorders. Intravenous EFG safety was assessed in generalized myasthenia gravis (gMG) in phase 2 and 3 (ADAPT) trials and a 3-year open-label extension (ADAPT+) trial. It was also evaluated in a phase 3 (ADVANCE) trial in primary immune thrombocytopenia (ITP) and an open-label phase 2 trial in pemphigus. These studies examined different dosing regimens of EFG (10–25 mg/kg), including cyclical dosing in gMG and continuous weekly dosing in ITP and pemphigus. EFG demonstrated a consistent safety profile across all indications and doses studied, with comparable treatment-emergent adverse event (TEAE) rates to placebo (ADAPT 77.4% EFG/84.3% placebo; ADVANCE 93.0% EFG/95.6% placebo; 85% of participants in the open-label pemphigus study). Most TEAEs across studies were mild to moderate in severity. Discontinuation rates due to adverse events were low across studies (3.6% EFG/3.6% placebo in ADAPT; 3.5% EFG/2.2% placebo in ADVANCE; 3% of pemphigus study participants). EFG was well tolerated in ADAPT+, with no increase in TEAE incidence rates or infections with repeated EFG cycles (up to 19). Efgartigimod treatment did not reduce albumin levels or increase cholesterol levels. 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.