Research Studies

- Boy or girl 2 to <18 years of age - Diagnosis of MG with generalized muscle weakness - Has a positive serologic test for acetylcholine receptor (anti-AChR) antibodies or muscle specific tyrosine kinase (anti-MuSK) antibodies at screening - Has suboptimal response to current stable therapy for gMG according to the investigator OR Has discontinued corticosteroids and/or immunosuppressants/immunomodulators - Medical History exclusion criteria might apply upon review - Exclusionary for patients dependent on gastric tube for nutritional needs or ventilator dependent - Wash-out period for current medications may apply

Inclusion Criteria: - Boy or girl 2 to <18 years of age. - Diagnosis of MG with generalized muscle weakness meeting the clinical criteria for gMG as defined by the MGFA Clinical Classification Class IIa/b, IIIa/b, or IVa/b at screening - Has suboptimal response to current stable therapy for gMG according to the investigator OR Has discontinued corticosteroids and/or immunosuppressants/immunomodulators including eculizumab or other novel approved immune agents at least 4 weeks prior to screening due to intolerance or lack of efficacy. -.Has a positive serologic test for acetylcholine receptor (anti-AChR) antibodies or musclespecific tyrosine kinase (anti-MuSK) antibodies at screening. United States. (www.cdc.gov) OR must be vaccinated as per country/territory-specific guidelines or local regulations. - Has sufficient venous access to allow drug administration by infusion and blood sampling as per the protocol - Is recommended to be up to date on all age-appropriate vaccinations (eg diphtheria and tetanus) prior to screening as per routine local medical guidelines - Participants should have a body weight and body mass index between 5th and 95th percentile for age and sex. Obese participants greater than 95th percentile and underweight participants below 5th percentile may participate following medical clearance - female of childbearing potential must have a negative pregnancy test - A legal guardian must sign an informed consent form (ICF) indicating that he or she understands the purpose of, and procedures required for, the study and is willing to participate in the study. - A legal guardian or primary caregiver must be available to help the study-site personnel ensure follow-up; accompany the participant to the study site on each assessment day Exclusion Criteria: - Has a history of severe and/or uncontrolled hepatic (eg, viral/alcoholic/autoimmune hepatitis/cirrhosis and/or metabolic liver disease), gastrointestinal, renal, pulmonary, cardiovascular (including congenital heart diseases), psychiatric, neurological musculoskeletal disorder, any other medical disorder(s) (eg, diabetes mellitus), or clinically significant abnormalities in screening laboratory - Has any confirmed or suspected clinical immunodeficiency syndrome not related to treatment of his/her gMG, or has a family history of congenital or hereditary immunodeficiency unless confirmed absent in the participant - Has MGFA Class I disease or presence of MG crisis (MGFA Class V) at screening, history of MG crisis within 1 month of screening, or fixed weakness - Is dependent on gastric tube for nutritional needs or is ventilator dependent. - Is actively undergoing radiation or chemotherapy for an unresected thymoma/malignant thymoma. Participants with stable, benign thymoma - Has had a thymectomy within 12 months prior to screening, or thymectomy is planned during the Active treatment Phase of the study. - Has current or a history of any neurologic disorder other than MG that might interfere with the accuracy of study assessments - Has shown a previous severe immediate hypersensitivity reaction, such as anaphylaxis to therapeutic proteins (eg, monoclonal antibodies). - Has experienced myocardial infarction, unstable ischemic heart disease, or stroke within 12 weeks of screening. - Contraception regulations apply - Has current suicidal ideation