New interim data from the open label extension (OLE) of the ADAPT-SC+ trial (NCT04818671) assessing a subcutaneous (SC) version of efgartigimod (Argenx) PH20 demonstrated improvements in daily function in treated patients with generalized myasthenia gravis (gMG). These findings suggest multiple cycles of the treatment were well tolerated and showed strong efficacy, which were consistent with the results observed in using the intravenous (IV) formulation in the ADAPT/ADAPT+trial (NCT03669588).1
Since March 2022, 164 patients received at least 1 dose of efgartigimod PH20 SC, with an average of approximately equal to 3 treatment cycles over a mean study duration of 170 days (SD, 59), resulting in 72 patient-years of observation. In the first cycle, at week 4, investigators observed a –4.0 score (SE, 0.25) reduction in the Myasthenia Gravis Activities of Daily Living (MGADL) total score from cycle baseline, with consistent and repeatable improvements observed by investigators in subsequent cycles.
Clinical Takeaway
- Efgartigimod PH20 subcutaneous treatment in the ADAPT-SC+ trial demonstrated consistent improvements in daily function for myasthenia gravis patients, with well-tolerated cycles of administered treatment.
- Patients who completed previous trials and received efgartigimod IV were eligible for the ongoing ADAPT-SC+ trial, which showed efficacy similar to the intravenous treatment.
- The most common adverse events were mild or moderate, including injection site erythema, headache, and COVID-19, which did not lead to treatment discontinuation and decreased in incidence with subsequent cycles.
These findings were presented at the American Association of Neuromuscular & Electrodiagnostic Medicine (AANEM) meeting, held November 1-4, in Phoenix, Arizona, by lead author Yuebing Li, MD, PhD, a neurologist in the neuromuscular center at the Cleveland Clinic, and colleagues. Patients who completed ADAPT-SC (NCT04735432) or who were enrolled in the efgartigimod IV OLE ADAPT+ were eligible also for the ongoing OLE, ADAPT-SC+ trial. In the OLE, efgartigimod PH20 SC 1000 mg was given to patients in cycles of 4 weekly injections. The subsequent cycles were performed at least 28 days from the last dose based on clinical evaluation and then MGADL score evaluated clinical efficacy.
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In this analysis, investigators noted that adverse events (AEs) were predominantly mild or moderate. The most common AEs were injection site erythema (25.6%), headache (15.2%), and COVID-19 (11.6%). Patients who had site reactions were also mild or moderate in severity, did not lead to any discontinuation of treatment, and reduced in the incidence with subsequent cycles.
In the phase 3 ADAPT-SC study, SC efgartigimod PH20 met its primary end point of total IgG reduction from baseline at day 29, while showing statistical noninferiority to the FDA approved IV efgartigimod afla-fcab (Vyvgart) formulation.2 In a study population of 110 participants, the subcutaneous formulation was associated with a mean total reduction in IgG of 66.4% at day 29 compared with 62.2% seen with the IV formulation (P <.0001 for noninferiority). These results were consistent across the overall study cohort and were no different between patients with or without acetylcholine receptor (AChR) antibodies.
