Abstract Details

In the ADAPT-SC study, efgartigimod PH20 SC was shown to have noninferior total IgG reduction to efgartigimod IV, resulting in similar clinical improvement in participants with gMG. Participants completing ADAPT-SC or enrolled in ADAPT+ (efgartigimod IV OLE) were eligible for the ongoing ADAPT-SC+ OLE.

Evaluate long-term safety, tolerability, and efficacy of subcutaneous (SC) efgartigimod PH20 (coformulated with recombinant human hyaluronidase PH20) in participants with generalized myasthenia gravis (gMG) enrolled in the ADAPT-SC+ open-label extension (OLE) study.

Efgartigimod PH20 SC 1000 mg was administered in cycles of 4 once-weekly injections. Subsequent cycles were initiated ≥28 days from the last dose based on clinical evaluation. Myasthenia Gravis Activities of Daily Living (MG-ADL) score assessed clinical efficacy. 

As of December 2022, 179 participants received ≥1 dose of efgartigimod PH20 SC, with an average of ≈6 treatment cycles over a mean (SD) study duration of 413 (105) days, resulting in 193 patient-years of observation. Adverse events (AEs) were predominantly mild/moderate. Most frequent AEs were injection site erythema (29.1%), COVID-19 (22.3%), and headache (20.1%). Injection site reactions were mild/moderate, did not lead to treatment discontinuation, and decreased in incidence with subsequent cycles from 34.6% (n=62/179) in Cycle 1 to 11.5% (n=14/122) in Cycle 6. Improvement from cycle baseline (mean [SE] improvement at Week 4) was observed in Cycle 1 in MG-ADL total score (-4.1 [0.27]), Myasthenia Gravis Quality of Life 15-Item Questionnaire, Revised (MG-QoL15r) (-5.1 [0.44]), and EuroQoL 5-Dimension, 5-Level (EQ-5D-5L) (13.8 [1.54]), with consistent and repeatable improvements seen through Cycle 9. Observed improvements were similar to those seen with efgartigimod IV during ADAPT/ADAPT+.

Treatment with multiple cycles of efgartigimod PH20 SC was well tolerated and efficacious, consistent with efgartigimod IV in ADAPT/ADAPT+.