Efgartigimod Demonstrates Consistent Improvements in Generalized Myasthenia Gravis Patients of Shorter Disease Duration
Vera Bril1, Tuan Vu2, Edward Brauer3, René Kerstens3, James Howard4, in collaboration with the ADAPT Investigator Study Group
1Ellen & Martin Prosserman Centre for Neuromuscular Diseases, University Health Network, 2Department of Neurology, University of South Florida, Morsani College of Medicine, 3argenx, 4Department of Neurology, The University of North Carolina
Objective:

Assess efficacy of efgartigimod in anti-AChR autoantibody positive (AChR-Ab+) patients with generalized myasthenia gravis (gMG) early in their disease and management course.

Background:

In the ADAPT study, efgartigimod (a human IgG1 antibody Fc-fragment that reduces pathogenic autoantibody and total IgG levels through neonatal Fc receptor blockade) was well tolerated and effective in a broad gMG population.

Design/Methods:

Efgartigimod 10 mg/kg or placebo was administered intravenously in cycles of 4 weekly infusions, with subsequent cycles initiated based on clinical evaluation. Efficacy assessment included Myasthenia Gravis Activities of Daily Living (MG-ADL) and Quantitative Myasthenia Gravis (QMG) scales, with response defined as ≥2-point (MG-ADL) or ≥3-point (QMG) improvement for ≥4 consecutive weeks, occurring ≤1 week after last infusion. This analysis assessed responder status and minimal symptom expression (MSE; MG-ADL 0 or 1) in subgroups of AChR-Ab+ patients with <3 years and ≥6 years disease duration.

Results:

In patients with <3 years disease duration, 78.6% (n=11/14) efgartigimod-treated vs 23.5% (n=4/17) placebo-treated were MG-ADL responders (95% CI, 25.6–84.5) during cycle 1. In patients with ≥6 years disease duration, the proportion of MG-ADL responders was 56.8% (n=21/37) for efgartigimod-treated and 21.9% (n=7/32) for placebo-treated patients (95% CI, 13.4-56.3). Similar results were observed in proportion of QMG responders between efgartigimod- and placebo-treated patients among <3 and ≥6-year subgroups. Additionally, 42.9% (n=6/14) of patients with <3 years disease duration and 40.5% (n=15/37) of patients with ≥6 years disease duration receiving efgartigimod were able to achieve MSE compared with 12.5% (n=2/16) and 9.4% (n=3/32) of those receiving placebo, respectively. Adverse events were mostly mild-moderate and included headache, nasopharyngitis, nausea, diarrhea, and upper respiratory/urinary tract infection.

Conclusions:

A greater percentage of patients early in their disease course (<3 years disease duration) treated with efgartigimod were responders and achieved MSE compared with placebo.

10.1212/WNL.0000000000203722