Efgartigimod Demonstrates Consistent Improvements in Generalized Myasthenia Gravis Across Patient Subgroups, Including Early in Diagnosis

Topic:

Clinical Trials

Poster Number: 134

Author(s):

Elissa Ritt, DHSc, argenx, Vera Bril, MD, Ellen & Martin Prosserman Centre for Neuromuscular Diseases, University Health Network, Tuan Vu, MD, University of South Florida, Edward Brauer, PharmD, argenx, René Kerstens, MSc, argenx, James Howard, MD, FAAN, The University of North Carolina at Chapel Hill, in collaboration with the ADAP in collaboration with the ADAPT Investigator Study, ADAPT Investigator Study Group

Background: In the ADAPT study, treatment with efgartigimod (a human IgG1 antibody Fc-fragment that reduces pathogenic autoantibody and total IgG levels through neonatal Fc receptor blockade) resulted in clinically meaningful improvements in acetylcholine receptor autoantibody positive (AChR-Ab+) patients with generalized myasthenia gravis (gMG).

Objectives: Assess efficacy of efgartigimod in subgroups of AChR-Ab+ patients (n=129) with gMG.

Methods: Efgartigimod (EFG) 10 mg/kg or placebo (PBO) was administered intravenously in cycles of 4 weekly infusions, with subsequent cycles initiated based on clinical evaluation. Efficacy was assessed using Myasthenia Gravis Activities of Daily Living (MG-ADL) and Quantitative Myasthenia Gravis (QMG) scores. Responder status was defined as ≥2-point (MG-ADL) and ≥3-point (QMG) improvement for ≥4 consecutive weeks (with first improvement ≤1 week after last infusion). The proportion of responders was assessed for patients sub-grouped by clinical characteristics such as time from diagnosis, thymectomy status, and concomitant medications.

Results: In patients <3 years from diagnosis, 78.6% EFG (n=11/14) vs 23.5% PBO (n=4/17) patients were MG-ADL responders (between group difference 55.0%, 95% CI, 25.6–84.5). In non-thymectomized patients, 85.0% EFG (n=17/20) achieved responder status vs 32.4% PBO (n=11/34; between group difference 52.6%, 95% CI, 30.5–74.8). The proportion of responders among patients receiving only concomitant acetylcholinesterase inhibitors was 84.6% EFG (n=11/13) vs 16.7% PBO (n=1/6; between group difference 67.9%, 95% CI, 32.3–100.0) and among patients receiving any corticosteroid was 63.0% EFG (n=29/46) vs 29.4% PBO (n=15/51; between group difference 33.6%, 95% CI, 14.9–52.4). Results for other subgroups, along with the proportion of QMG responders, also consistently favored EFG. Common adverse events (mostly mild/moderate) in both treatment arms were headache, nasopharyngitis, nausea, diarrhea, and upper respiratory/urinary tract infection. Conclusion: Efgartigimod treatment resulted in consistent improvements across subgroups, including patients with early disease, reinforcing the efficacy of efgartigimod across a broad gMG population.