Evaluating Long-term Safety of Efgartigimod Administered Intravenously in Children With Generalized Myasthenia Gravis

Study Overview
=================
Brief Summary
-----------------
The purpose of this trial is to evaluate the safety of efgartigimod administered to participants of the previous trial ARGX-113-2006.

Official Title
-----------------
A Long-term, Single-Arm, Open-label, Multicenter, Follow-on Trial of ARGX-113-2006 to Evaluate Safety of Efgartigimod Administered Intravenously in Children With Generalized Myasthenia Gravis

Conditions
-----------------
Generalized Myasthenia Gravis

Intervention / Treatment
-----------------
* Biological: Efgartigimod IV


Participation Criteria
=================
Eligibility Criteria
-----------------
Inclusion Criteria: Participants are eligible to be included in the trial only if all of the following criteria apply: The participant completed ARGX-113-2006, defined as: The participant reached end of trial in trial ARGX-113-2006 and agreed to participate in the ARGX-113-2008 trial. 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 (ie, between TPnV1 to IPnV4). Either the participant or the participant's legally acceptable representative (LAR) can understand the requirements of the trial and provide written informed consent/assent (including consent/assent for the use and disclosure of research-related health information), and demonstrates a willingness and ability to comply with the trial protocol procedures (including attending the required trial visits). Contraceptive use by males and females must be consistent with local regulations for those participating in clinical trials and: Male participants agree not to donate sperm from the time the informed consent form (ICF) is signed until the end of the trial. Female adolescents of childbearing potential (FAOCBP; defined in Section 10.4.1.1 of the protocol) must have a negative urine pregnancy test at trial entry (TP1V1 or IP0V1). The contraceptive requirements for male participants are described in Section 10.4.2.2 of the protocol. The contraceptive requirements for FAOCBP are described in Section 10.4.2.1 of the protocol. Exclusion Criteria: Participants are excluded from the trial if any of the following criteria apply: Female adolescents of childbearing potential: Pregnancy or lactation, or the participant intends to become pregnant during the trial or within 90 days after the last dose of investigational medicinal product (IMP). Discontinued early from ARGX-113-2006 treatment for pregnancy, receiving prohibited medication, participating in another trial with an investigational product, or the occurrence of a life threatening or an investigational medicinal product-related adverse events, as assessed by the investigator A known hypersensitivity reaction to efgartigimod or any of its excipients Received a live-attenuated vaccine fewer than 4 weeks before trial entry. Any of the following medical conditions: Clinically significant uncontrolled chronic bacterial, viral, or fungal infection at trial entry Any other known autoimmune disease that, in the opinion of the investigator, would interfere with accurate assessment of clinical symptoms of myasthenia gravis or put the participant at undue risk

Ages Eligible for Study
-----------------
Minimum Age: 2 Years
Maximum Age: 18 Years

Sexes Eligible for Study
-----------------
All

Accepts Healthy Volunteers
-----------------
No

Study Plan
=================
How is the study designed?
-----------------

Design Details

Primary Purpose: Treatment
Intervention Model: Single Group Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Efgartigimod<br>Patients receiving efgartigimod IV treatment | Biological: Efgartigimod IV<br>* Intravenous infusion of Efgartigimod<br>|

What is the study measuring?
-----------------
Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Incidence of adverse events (AEs) |  | up to 4 years | 
| Severity of adverse events (AEs) |  | up to 4 years | 
| Incidence of serious adverse events (SAEs) |  | up to 4 years | 
| Severity of serious adverse events (SAEs) |  | up to 4 years | 
| Incidence of adverse events of special interest (AESIs) |  | up to 4 years | 
| Severity of adverse events of special interest (AESIs) |  | up to 4 years | 
| Changes in height from baseline |  | up to 4 years | 
| Changes in weight from baseline |  | up to 4 years | 
| Electrocardiogram - heart rate |  | up to 4 years | 
| Electrocardiogram - QTcF (ms) |  | up to 4 years | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Incidence of antidrug antibodies (ADAs) against efgartigimod |  | up to 4 years | 
| Prevalence of antidrug antibodies (ADAs) against efgartigimod |  | up to 4 years |