Evaluating Long-term Safety of Efgartigimod Administered Intravenously and Efgartigimod PH20 Administered Subcutaneously in Children With Generalized Myasthenia Gravis (ADAPT Jr +)

A Long-term, Single-Arm, Open-label, Multicenter Trial to Evaluate Safety of Efgartigimod Administered Intravenously and Efgartigimod PH20 Administered Subcutaneously in Children With Generalized Myasthenia Gravis

The purpose of this trial is to evaluate the long-term safety of efgartigimod IV and efgartigimod PH20 SC administered to participants with gMG in the antecedent studies, ARGX-113-2006 and ARGX-113-2207, respectively.

Participants will receive efgartigimod IV or efgartigimod PH20 SC, using the dose administered in the antecedent studies. Participants who have not reached the age of 18 can remain in the study until efgartigimod becomes commercially available in the respective country or available through another continued access program for gMG. Participants who have reached the age of 18 can remain in the study for a maximum of 2 years, until efgartigimod becomes commercially available in the respective country or available through another continued access program for gMG, whichever comes first.

Study Overview

• Status: Enrolling by invitation
• Conditions: Generalized Myasthenia Gravis; gMG
• Intervention / Treatment: Biological: Efgartigimod IV or Efgartigimod PH20 SC

• Study Type: Interventional
• Enrollment (Estimated): 12
• Phase: Phase 2; Phase 3

Contacts and Locations

Study Locations

• Belgium
  • Edegem, Belgium, 2650
    • Universitair Ziekenhuis Antwerpen
  • Ghent, Belgium, 9000
    • UZ Gent
• Canada
  • Ottawa, Canada, K1H 8L1
    • Childrens Hospital of Eastern Ontario
• France
  • Marseille, France, 13005
    • AP-HM- Hôpital de La Timone
• Germany
  • Essen, Germany, 45147
    • Universitatsklinikum Essen
• Israel
  • Jerusalem, Israel, 9112001
    • Hadassah Medical Center- Ein Kerem
• Netherlands
  • Leiden, Netherlands, 2333 ZA
    • Leids Universitair Medisch Centrum
• Poland
  • Gdansk, Poland, 80-211
    • Uniwersyteckie Centrum Kliniczne w Gdansku
  • Katowice, Poland, 40-123
    • Wielospecjalistyczna Poradnia Lekarska Synapsis
  • Warsaw, Poland, 02-097
    • Centralny Szpital Kliniczny - Uniwersyteckie Centrum Kliniczne WUM
• Spain
  • Valencia, Spain, 46026
    • Hospital Universitari i Politecnic La Fe de Valencia
• United Kingdom
  • London, United Kingdom, WC1N 3JH
    • Great Ormand Street Hospital for Children NHS Foundation Trust - Great Ormond Street Hospital - Pediatric Neurology
  • Oxford, United Kingdom, OX3 9DU
    • Oxford University Hospitals NHS Foundation Trust - John Radcliffe Hospital Children's Hospital
• United States
  • Illinois
    • Chicago, Illinois, United States, 60611
      • Ann and Robert H Lurie Children's Hospital of Chicago - Main Hospital
  • North Carolina
    • Charlotte, North Carolina, United States, 28207
      • Atrium Health Neurology Specialty Care
  • Virginia
    • Charlottesville, Virginia, United States, 22903
      • University of Virginia (UVA) Health - Developmental Pediatrics Clinic

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 2 years to 18 years (Child, Adult)
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

• The participant completed ARGX-113-2006, defined as:

  1. The participant reached End of Trial in trial ARGX-113-2006 or End of Study in ARGX-113-2207 and agreed to participate in the ARGX-113-2008 trial.
  2. The participant qualifies for retreatment in trial ARGX-113-2006, but cannot complete a Treatment Period (TP) and the required Intertreatment Period (IP) visits within the ARGX-113-2006 trial's timeframe.
• Either the participant or the participant's legally authorized representative can understand the requirements of the trial and provide written informed consent/assent, and willingness and ability to comply with the trial protocol procedures.
• Contraceptive use for sexually active participants should be consistent with local regulations for those participating in clinical studies.

Exclusion Criteria:

• Female adolescents of childbearing potential (FAOCBP): Pregnancy or lactation, or the participant intends to become pregnant during their participation in the study.
• Discontinued early from ARGX-113-2006 or ARGX-113-2207 treatment.
• Clinically significant uncontrolled chronic bacterial, viral, or fungal infection at study entry not sufficiently resolved in the investigator's opinion or known autoimmune disease or any medical condition that would interfere with an accurate assessment of clinical symptoms of gMG or put the participant at undue risk.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: N/A
• Interventional Model: Single Group Assignment
• Masking: None (Open Label)

Number of Arms

1

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Efgartigimod or Efgartigimod PH20 SC; Patients receiving Efgartigimod IV treatment or Efgartigimod PH 20 SC treatment	Biological: Efgartigimod IV or Efgartigimod PH20 SC; Intravenous infusion of Efgartigimod or Subcutaneous injection of Efgartigimod PH20 SC

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Incidence of AEs, SAEs and AESIs	AE : adverse event; SAE : serious adverse event; AESI : adverse event of special interest	Up to 4 years

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Incidence of ADAs against efgartigimod	ADA : anti-drug antibody	Up to 4 years
Incidence of antibodies against rHuPH20	rHuPH20: recombinant human hyaluronidase PH20	Up to 4 years

Collaborators and Investigators

• Sponsor: argenx

Study record dates

Study Major Dates

• Study Start (Actual): August 18, 2022
• Primary Completion (Estimated): September 1, 2029
• Study Completion (Estimated): September 1, 2029

Study Registration Dates

• First Submitted: April 1, 2022
• First Submitted That Met QC Criteria: May 13, 2022
• First Posted (Actual): May 16, 2022

Study Record Updates

• Last Update Posted (Actual): April 23, 2026
• Last Update Submitted That Met QC Criteria: April 22, 2026
• Last Verified: January 1, 2026

More Information

Terms related to this study

• Additional Relevant MeSH Terms: Nervous System Diseases; Neoplasms by Site; Neoplasms; Neuromuscular Diseases; Autoimmune Diseases; Immune System Diseases; Autoimmune Diseases of the Nervous System; Neurodegenerative Diseases; Paraneoplastic Syndromes, Nervous System; Nervous System Neoplasms; Paraneoplastic Syndromes; Neuromuscular Junction Diseases; Myasthenia Gravis
• Other Study ID Numbers: ARGX-113-2008; 2023-507379-23-00 (Ctis)

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: UNDECIDED

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: Yes
• Studies a U.S. FDA-regulated device product: No
• product manufactured in and exported from the U.S.: Yes