Clinical Experience With Efgartigimod in Generalized Myasthenia Gravis: Results From a Case Series of US-Based Patients Participating in an Expanded Access Program

Objective To describe the efgartigimod treatment regimens and response among 6 US-based patients with generalized myasthenia gravis (gMG) enrolled in an Expanded Access Program (EAP). Background For some patients with gMG, available therapies do not provide sufficient symptom relief and can cause serious side effects. Efgartigimod, a human IgG1 antibody Fc-fragment (natural ligand of the neonatal crystalline fragment receptor [FcRn]), has increased affinity to FcRn vs endogenous IgG. Efgartigimod reduces IgG recycling and increases IgG degradation. Efgartigimod received FDA approval in 2021 for the treatment of gMG in adults who are anti-acetylcholine receptor (AChR) antibody positive. Design/Methods In the efgartigimod EAP (NCT04777734), gMG patients had access to open-label efgartigimod. Eligible patients (=18 y) met clinical criteria of the Myasthenia Gravis Foundation of America classifications II–IV and had a Myasthenia Gravis Activities of Daily Living (MG-ADL) score =5 points (>50% attributed to non-ocular symptoms). During the first two, fixed-treatment cycles, patients received 4 weekly infusions of efgartigimod 10 mg/kg. During the 4-week inter-treatment period, patients received their ongoing treatments and no efgartigimod infusions. Baseline demographic characteristics and safety data were collected. Treating physicians had the option to assess and track clinical function and burden of disease among treated patients. Results As of the cutoff date (Dec 17, 2021), 8 patients have been enrolled in the US; follow-up data are available for 6 (3 males and 3 females; median age 59 y). 83% (5/6) of patients received at least 2 treatment cycles and 4–5 infusions per cycle. Symptom improvements were noted. Four patients reported 6 AEs: fatigue (resolved), tachycardia and headache (both resolved), dyspnea and diplopia (both not resolved), and back spasms (status unknown). Conclusions We report on 6 patients with gMG who received efgartigimod as part of an EAP. Detailed patient narratives will be presented.