A Study of Efgartigimod PH20 SC in Children Between 2 and Less Than 18 Years of Age With Generalized Myasthenia Gravis

Exclusion criteria

• Is a female adolescent of child-bearing potential who is pregnant and/or lactating or intends to become pregnant during their participation in the study • Has worsening muscle weakness secondary to a concurrent infection or as a result of a medication • Has a documented lack of clinical response to plasma exchange (PLEX) • Received a live or live-attenuated vaccine within \<4 weeks before screening • Received a thymectomy within 3 months before screening or is planning to get a thymectomy during their participation in the study • Has a known autoimmune disease or any medical condition that would interfere with an accurate assessment of clinical symptoms of generalised Myasthenia Gravis or puts the participant at undue risk • History of malignancy, cancer, unless considered cured by adequate treatment with no evidence of recurrence for ≥3 years. Adequately treated participants with the following cancers can be included at any time: 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 • Clinically significant active infection that is not sufficiently resolved in the investigator's opinion or positive serum test at screening for active infection with any of the following: Hepatitis B virus (HBV), Hepatitis C virus (HCV), HIV • Has a positive PCR test for SARS-CoV-2 at screening • Has/had a clinically significant disease, had recent major surgery (within 3 months of screening) or intends to have major surgery during the study, or has/had any other medical condition that, in the investigator's opinion, would confound the results of the study or put the participant at undue risk • Has received a different study drug in another clinical study within \<12 before screening • Is currently participating in another interventional clinical study • Has previously participated in an efgartigimod clinical study and received at least one dose of study drug • Has a known hypersensitivity to study drug or any of its excipients • Has a history of or current episode of alcohol, drug, or medication abuse as assessed by the investigator • Use of some medications before screening (more information is found in the protocol) The complete list of exclusion criteria can be found in the protocol.