OBJECTIVES: MG-ADL is a widely-used outcome in generalized Myasthenia Gravis (gMG), measuring impairments in talking, chewing, swallowing, breathing, brushing teeth/combing hair, rising from a chair, double vision and eyelid droop. No relationship has been established between MG-ADL and Health-Related Quality-of-Life. This analysis aimed to estimate the relationship between gMG symptoms and utility values (UK value set) using the Phase-3 ADAPT data, and to verify what the effect was of efgartigimod on this association. Efgartigimod is a novel therapy significantly improving gMG symptoms.

METHODS: The ADAPT study enrolled 167 gMG patients comparing efgartigimod vs. placebo plus conventional therapy (CT). The MG-ADL and EQ-5D-5L were completed (bi-)weekly up to 26 weeks. A first regression estimated the association between utility and the eight domains of the MG-ADL. A Generalized Estimating Equations (GEE) model was then estimated to predict utility based on the patient’s total MG-ADL score and treatment received.

RESULTS: A total of 3,032 simultaneous assessments of MG-ADL and EQ-5D-5L were collected in ADAPT. Mean changes in MG-ADL score and in EQ-5D utility during follow-up were -3.2 and +0.116 for efgartigimod and -1.8 and +0.05 for CT. Efgartigimod-treated patients experienced more improvements than CT in all domains, with the largest improvements observed in: swallowing, brushing teeth/combing hair (MG-ADL); self-care, usual activities and mobility (EQ-5D-5L).

Regression analysis showed individual MG-ADL domains contributed differently to utility values, with the greatest contributions from brushing teeth/combing hair, rising from a chair, chewing food and breathing. The GEE model showed that each unit improvement in MG-ADL lead to a utility increase of 0.0233 (p<0.001), and that efgartigimod-treated patients experienced an additional improvement of 0.0598 (p=0.0079) in utility for the same MG-ADL score.

CONCLUSIONS: Improvements in gMG symptoms were significantly associated with higher utility values. MG-ADL scores alone were not sufficient to capture the utility gained from efgartigimod therapy.