Evaluating the Pharmacokinetics, Pharmacodynamics, and Safety of Efgartigimod Administered Intravenously in Children With Generalized Myasthenia Gravis

Exclusion Criteria

• •1. Participants with MGFA class I, IVb, and V.
• •2. 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 IMP.
• •3. Has any of the following medical conditions:
• •1. Clinically significant uncontrolled active or chronic bacterial, viral, or fungal infection at screening.
• •2. Any other known autoimmune disease that, in the opinion of the investigator, would interfere with an accurate assessment of clinical symptoms of myasthenia gravis or put the participant at undue risk.
• •3. History of malignancy unless deemed cured by adequate treatment with no evidence of recurrence for ≥3 years before the first administration of IMP. Participants with the following cancers can be included at any time: Adequately treated basal cell or squamous cell skin cancer; Carcinoma in situ of the cervix; Carcinoma in situ of the breast; Incidental histological findings of prostate cancer
• •4. Clinical evidence of other significant serious diseases, or have had a recent major surgery, or who have any other condition that, in the opinion of the investigator, could confound the results of the trial or put the participant at undue risk
• •4. Worsening muscle weakness secondary to concurrent infections or medications (aminoglycosides, fluoro-quinolones, beta-blockers, etc).
• •5. A documented lack of clinical response to plasma exchange (PLEX).
• •6. Received a live or live-attenuated vaccine fewer than 28 days before screening. Receiving an inactivated, subunit, polysaccharide, or conjugate vaccine any time before screening is not exclusionary.
• •7. Received a thymectomy \<3 months before screening or 1 is planned to be performed during the trial period.
• •8. The following results from these diagnostic assessments will be considered exclusionary:
• •a. Positive serum test at screening for an active viral infection with any of the following conditions: Hepatitis B virus (HBV) that is indicative of an acute or chronic infection; Hepatitis C virus (HCV) based on HCV antibody assay; Positive HIV serology at screening; Positive nasopharyngeal swab polymerase chain reaction (PCR) test for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) at screening.
• •9. Using the following prior or concomitant therapies: Use of an investigational product within 3 months or 5 half-lives (whichever is longer) before the first dose of IMP, Use of any monoclonal antibody within the 6 months before the first dose of IMP, Use of intravenous immunoglobulin (IVIg), administered subcutaneously or intramuscularly, or PLEX within 4 weeks before screening.
• •10. Total immunoglobulin (IgG) levels \<6 g/L below the lower limit of normal (LLN) according to the reference ranges of the central laboratory for participant by sex and age at screening.
• •11. A known hypersensitivity reaction to efgartigimod or any of its excipients.
• •12. Current participation in another interventional clinical trial or previous participation in an efgartigimod trial with at least 1 dose of IMP received.
• •13. History (within 12 months of screening) of current alcohol, drug, or medication abuse as assessed by the investigator.