Long-term assessment of safety, tolerability, and effectiveness of subcutaneous efgartigimod PH20 in adults with generalized myasthenia gravis: final findings from the phase 3 open-label extension study (ADAPT-SC+)

To evaluate the long-term safety, tolerability, and efficacy of subcutaneous efgartigimod PH20 in adults with generalized myasthenia gravis (gMG).

Study Design: Multicenter, single-arm, open-label extension trial where participants received efgartigimod PH20 SC 1000 mg in individualized cycles.
Treatment Administration: Cycles comprised four weekly injections, with intervals of ≥4 weeks in year 1 and ≥1 week from year 2 for consenting participants.

180 participants received at least one dose of efgartigimod PH20 SC, with a mean treatment duration of 2.6 years.
Treatment-emergent adverse events (TEAEs) occurred in 93.9% of participants, with injection site reactions (46.1%) being the most common, followed by COVID-19 (29.4%) and headache (26.7%).
95.1% of AChR-Ab+ and 94.7% of AChR-Ab− participants achieved clinically meaningful improvement (CMI) in Myasthenia Gravis Activities of Daily Living (MG-ADL).
59.2% of AChR-Ab+ and 34.2% of AChR-Ab− participants reached minimal symptom expression (MSE).
83.3% of participants with AChR-Ab+ gMG and 53.8% with AChR-Ab− gMG maintained MSE across consecutive assessments for ≥8 weeks.

ADAPT-SC+ findings demonstrate sustained efficacy, safety, and tolerability of efgartigimod PH20 SC.

The study provides evidence for the long-term use of efgartigimod PH20 SC in managing gMG.