Efgartigimod Improves Activities of Daily Living in AntiAChR-Positive Myasthenia Gravis

In the phase 3 ADAPT trial (NCT03669588) of efgartigimod (ARGX-113; Argenx, Boston, MA), participants with acetylcholine receptor-antibody positive (antiAChR+) myasthenia gravis (MG) showed improvements on MG Activities of Daily Living (MG-ADL) and Quantitative Myasthenia Gravis (QMG) scales.

Efgartigimod is an investigational antibody fragment made to reduce disease-causing immunoglobulin G (IgG) antibodies and block the IgG recycling process. Efgartigimod binds to the neonatal Fc receptor (FcRn), which is widely expressed throughout the body and plays a central role in rescuing IgG antibodies from degradation. 

At week 4, participants with antiAChR+ MG who were treated with efgartigimod had an increase in thresholds on the MG-ADL and QMG scores compared with participants treated with placebo. Of the participants treated with efgartigimod, 55.6% had a 5-point or greater improvement on the MG-ADL and a 6-point or greater improvement on the QMG (50.0%). Approximately one-third (33.9%) of participants treated with efgartigimod had a 9-point or greater improvement on the QMG score, which was not achieved by any participants treated with placebo.

Responders were defined by having at least a 2-point change on the MG-ADL for at least 4 consecutive weeks. Efgartigimod was demonstrated to be well-tolerated with a safety profile that was comparable to placebo. Participants with antiAChR+ MG who were treated with efgartigimod were MG-ADL responders in the first (67.7% efgartigimod vs 29.7% placebo) and second (70.6% efgartigimod vs 25.6% placebo) treatment cycles (P<.0001 for both cycles).Of the participants with antiAChR + generalized MG (gMG) treated with efgartigimod, 67.7% were responders on the MG-ADL score compared with 29.7% of participants treated with placebo (P<.0001).

This trialwas a randomized double-blind placebo-controlled multicenter global trial evaluating the safety and efficacy of efgartigimod in participants with gMG. A total of 167 adults with gMG enrolled were randomly assigned to receive efgartigimod or placebo in a 1:1 ratio for 26 weeks. Participants were eligible to enroll in ADAPT regardless of antibody status, including patients with AChR antibodies (AChR-Ab+) and patients where AChR antibodies were not detected. Participants were randomized in a 1:1 ratio to receive efgartigimod or placebo for a total of 26 weeks.