Objectives: Efgartigimod has demonstrated efficacy and is well tolerated in patients with generalized myasthenia gravis (gMG) in the phase 3 ADAPT study (NCT: NCT03669588). This analysis compared the hospitalization (all-cause and MG-related) and exacerbation rates of adults with gMG using data from ADAPT.

Methods: ADAPT is a 26-week, global phase 3, randomized, double-blind, placebo controlled trial of 167 gMG patients. Patients were randomized 1:1 to receive a stable dose of oral therapy (any combination of Acetylcholinesterase Inhibitors, steroids or non-steroidal immunosuppressants) plus efgartigimod or placebo. All-cause and MG-related hospitalizations observed during the trial follow-up were compared between the treatment arms, as was the proportion of patients experiencing an exacerbation. An exacerbation event is defined as a 3-point worsening in Quantitative MG score compared to baseline.

Results: 14 hospitalization events were identified (4 efgartigimod; 10 placebo) during the study. Among these, 4 hospitalizations were related to MG (1 efgartigimod; 3 placebo). Efgartigimod patients had 50% lower rate of all-cause hospitalization (11.4 vs. 28.3 per 100 patient-year [PY]) and 67% lower rate of MG-related hospitalization (2.8 vs. 8.5 per 100 PY) than placebo patients. During the 26-week follow-up, significantly fewer efgartigimod-treated patients experienced exacerbations: 21% (18/84) versus 44% (36/81) for placebo-treated patients (p=0.0016). Among those experiencing exacerbations, the average worsening in QMG was 5.2 (range: 3 to 12) for patients receiving efgartigimod and 5.6 (range: 3 to 15) for patients receiving placebo. Consistent results were seen among Acetylcholine receptor positive patients.

Conclusions: Among adult patients with gMG, efgartigimod treatment was associated with significant reduction in exacerbation risk, and numerically lower rates of all-cause and MG-related hospitalizations.