P.057 Achievement of minimal symptom expression in acetylcholine receptor antibody-positive participants treated with efgartigimod in ADAPT/ADAPT+

Abstract

Background: A key efficacy indicator in generalized myasthenia gravis (gMG) treatment is improvement in MG-ADL score. Minimal symptom expression (MSE, MG-ADL total score of 0 or 1) is explored as a novel proposed treatment target in gMG in the phase 3 study of intravenous efgartigimod, ADAPT, and its open-label extension, ADAPT+. Methods: Post hoc analyses of acetylcholine receptor antibody positive participants in ADAPT (n=129) and ADAPT+ (n=111) were performed. Results: In ADAPT, 44.6% receiving efgartigimod achieved MSE vs 10.9% of participants given placebo. Despite less frequent assessment during ADAPT+, 40.5% of participants achieved MSE. Eighty-one percent of participants treated with efgartigimod who achieved MSE in ADAPT also achieved MSE during ADAPT+; 23% who had not achieved MSE in ADAPT did in ADAPT+. Achieving MSE was associated with substantial improvements in QMG, MGC, MG-QoL15r, and EQ-5D-5L mean scores of 11.4, 16.0, 12.4, and 0.3 points, respectively, from baseline to best score (across all visits). These drastic improvements resulted in quality of life (QoL) comparable to that of healthy populations. MSE achievement also resulted in sustained improvements in these disease-specific and QoL measures. Conclusions: Participants who achieved MSE showed substantial and consistent improvements across multiple disease measures and experienced QoL comparable to that of healthy populations.