Study Design of Subcutaneous Efgartigimod PH20 in Juvenile Generalized Myasthenia Gravis

Topic:

Clinical Trials

Poster Number: P356

Author(s):

Jamie Aldridge, PhD, PA-C, argenx, Ghent, Belgium, Abigail Schwaede, MD, Ann & Robert H. Lurie Children’s Hospital of Chicago, Northwestern University Feinberg School of Med, Nancy L. Kuntz, MD, Ann & Robert H. Lurie Children’s Hospital of Chicago, Northwestern University Feinberg School of Med, Anna Bogatyreva, argenx, Ghent, Belgium, Flavia Menezes, argenx, Ghent, Belgium, Juliette Giacobbe, argenx, Ghent, Belgium, Tonke van Bragt, Curare Consulting BV, Liempde, The Netherlands, Anna Kostera-Pruszczyk, MD, PhD, Department of Neurology, Medical University of Warsaw & ERN EURO-NMD, Warsaw, Poland, Sithara Ramdas, Dr, John Radcliffe Hospital; MDUK Oxford Neuromuscular Centre, University of Oxford, Oxford, UK

Introduction
Efgartigimod is a human immunoglobulin G1 (IgG1) antibody Fc-fragment that blocks neonatal Fc receptor (FcRn). Previous phase 3 trials have demonstrated that both efgartigimod IV (ADAPT/ADAPT+) and efgartigimod PH20 SC (ADAPT-SC/ADAPT-SC+) is efficacious and well tolerated in adults with gMG. The incidence of juvenile gMG (1-5:1,000,000) is considerably lower than adult gMG and there remains an unmet need for effective and safe treatments in this population. A clinical trial assessing efgartigimod IV in juvenile gMG (NCT04833894) is currently underway. Here, we present the study design evaluating efgartigimod PH20 SC in patients with juvenile gMG (NCT06392386).

Objective
This study aims to confirm the age-appropriate dose of subcutaneous efgartigimod coformulated with recombinant hyaluronidase (efgartigimod PH20 SC).

Methods
This study will recruit ≥12 patients, aged 2-17 years, and has a staggered design starting with the older age group (12-17 years). Participants must have a confirmed diagnosis of MGFA class II, III, or IVa, seropositivity for anti-AChR autoantibodies, and be on a stable dose of MG therapy. The study will consist of a 2-week screening period, 4-week treatment period, and 8-week follow-up period. During the treatment period, patients will receive 4 once-weekly injections of efgartigimod PH20 SC.

Results
Pharmacokinetics (PK), pharmacodynamics (PD), safety, tolerability, immunogenicity, and clinical effect of efgartigimod PH20 SC will be assessed, along with evaluation of antibody responses to vaccines during efgartigimod treatment. Assessments include MG-ADL, QMG, EQ-5D-Y, Quality of Life in Neurological Disorders Pediatric Fatigue Score, and Clinical Global Impression of Improvement. Age-appropriate adaptations to assessments will be made during the study.

Summary/Conclusion
This study will use PK/PD modeling to confirm the appropriate efgartigimod PH20 SC dose and evaluate efficacy and safety for pediatric patients with gMG. Efgartigimod PH20 SC may address an unmet need and provide additional flexibility for the treatment of pediatric patients with gMG.