An Open-Label, Single-arm Study to Evaluate the Pharmacokinetics (PK), Pharmacodynamics (PD), Safety, and Efficacy of Gefurulimab in Pediatric Patients (6 to < 18 Years of Age) With Generalized Myasthenia Gravis (gMG) Who Express Acetylcholine Receptor Antibodies (AChR+)

Inclusion Criteria: United States of America (USA) specific inclusion criterion: * Participant must be 12 to \< 18 years of age at the time of signing the informed consent/assent. * All participants must be vaccinated against meningococcal infection from serogroups A, B, C, W, and Y within 3 years and at least 2 weeks prior to the first dose of study intervention administration. Rest of World (ROW) specific inclusion criteria: * Participant must be 6 to \< 18 years of age at the time of signing the informed consent/assent. * All participants must be vaccinated against meningococcal infection from serogroups A, C, W, Y (and B where available) within 3 years prior to study intervention on Day 1. If vaccination occurs \< 2 weeks prior to Day 1, the participants will receive prophylactic antibiotics for at least 2 weeks after initial meningococcal vaccination for serogroups A,C,W,Y (and B, where available) Global inclusion criteria: * Diagnosis of MG with generalized muscle weakness meeting the clinical criteria defined by Myasthenia Gravis Foundation of America (MGFA) Class II, III or IV * Positive serological test for autoantibodies against AChR Exclusion Criteria: * History of thymectomy, or any other thymic surgery within 12 months prior to Screening * Untreated thymic malignancy, carcinoma, or thymoma * History of Neisseria meningitidis infection * Pregnancy, breastfeeding, or intention to conceive during the course of the study