Individualized Dosing of Efgartigimod in Patients With Generalized Myasthenia Gravis: Clinical Experience at a Single Center.

Introduction/aims: Neonatal Fc receptor (FcRn) inhibitors represent a promising treatment option for patients with generalized myasthenia gravis (gMG); however, data on clinical use are limited. The aim of this report is to describe one center's approach to efgartigimod dosing in patients with gMG.

Methods: Medical records of patients with acetylcholine receptor antibody-positive (AChR-Ab+) gMG whose symptoms were not adequately controlled by oral medications and/or intravenous immunoglobulin who received efgartigimod between January 2022 and January 2024 were retrospectively evaluated. The first three efgartigimod cycles (10 mg/kg IV) were initiated at fixed intervals (4 once-weekly infusions, with 4 weeks between cycles). After the third cycle, initiation of subsequent treatment cycles and time between cycles were determined individually by clinical evaluation. Effectiveness was measured by the Myasthenia Gravis Activities of Daily Living (MG-ADL) scale. Adverse events and changes to concomitant therapies were monitored.

Results: Nineteen patients were included and received a mean of 4.4 efgartigimod cycles, including two patients who discontinued after two cycles. All patients exhibited a clinically meaningful improvement in MG-ADL total score from baseline to the end of the last cycle, with a mean improvement of 5.8 points. Seven (37%) patients achieved minimal symptom expression (MSE, MG-ADL 0-1). From baseline to the end of the last cycle, daily prednisone dose was decreased or it was discontinued, while two patients initiated prednisone. Efgartigimod was generally well tolerated.

Discussion: This approach to efgartigimod dosing resulted in substantial MG-ADL score improvement in these patients with AChR-Ab+ gMG as well as reduced daily dose and/or discontinuation of concomitant corticosteroids.