Achievement of Minimal Symptom Expression and Effect on Disease-specific Measures in Acetylcholine Receptor Antibody-positive Participants with Generalized Myasthenia Gravis Treated with Efgartigimod in ADAPT/ADAPT+
Srikanth Muppidi1, James Howard2, Hiroyuki Murai3, Glenn Phillips4, Cynthia Qi4, Deborah Gelinas4, Edward Brauer4, Sihui Zhao4, Vera Bril5, John Vissing6
1Stanford Healthcare, Palo Alto, California, 2Department of Neurology, The University of North Carolina, Chapel Hill, North Carolina, 3Department of Neurology, School of Medicine, International University of Health and Welfare, Tokyo, Japan, 4argenx, Ghent, Belgium, 5Ellen & Martin Prosserman Centre for Neuromuscular Diseases, University Health Network, Toronto, Ontario, Canada; University of Toronto, Toronto, Ontario, Canada, 6Copenhagen Neuromuscular Center, Rigshospitalet, University of Copenhagen, Denmark
Objective:

To assess incidence, characteristics, and changes in generalized myasthenia gravis (gMG)-specific scales in participants achieving minimal symptom expression (MSE) in the phase 3 study of intravenous efgartigimod, ADAPT, and its open-label extension, ADAPT+.

 

 

Background:

Efgartigimod, a human IgG1 antibody Fc-fragment, reduces IgG levels through neonatal Fc receptor blockade. A key efficacy indicator in gMG treatment is improvement in MG-ADL score. MSE (MG-ADL total score of 0 or 1) is explored as a novel proposed treatment target in gMG.

 

Design/Methods:

Post hoc analyses of acetylcholine receptor antibody-positive participants in ADAPT (n=129) and ADAPT+ (n=111) were performed.

Results:

In ADAPT participants, 44.6% treated with efgartigimod achieved MSE vs 10.9% of participants given placebo any time during the study. The difference between groups was noted as early as Week 4 and sustained throughout the study. In ADAPT+, 40.5% of participants achieved MSE. Eighty-one percent of participants from the efgartigimod arm who achieved MSE in ADAPT also achieved MSE during ADAPT+; 23% who had not achieved MSE in ADAPT did in ADAPT+. Baseline characteristics for efgartigimod-treated participants who achieved MSE during ADAPT were comparable to those who did not. Although mean (SD) baseline MG-ADL score was statistically significantly lower for those achieving MSE (8.2 [1.8] vs 9.7 [2.7]; P<0.0084), the difference was not clinically meaningful. Achieving MSE was associated with substantial improvements in QMG, MGC, and MG-QoL15r mean scores of 11.4, 16.0, and 12.4 points, respectively, from baseline to best score (across all visits). Researchers observed a 0.3-point increase in EQ-5D-5L utility score, resulting in quality of life (QoL) comparable to healthy populations. MSE achievement also resulted in sustained improvements of these disease-specific and QoL measures. Patients experienced clinically meaningful improvements over 60% of the visits during ADAPT.

Conclusions:

Participants who achieved MSE had substantial improvement across multiple disease measures and experienced QoL comparable to healthy populations.

 

10.1212/WNL.0000000000205792