RecruitingPhase 3Drug trialA Study To Evaluate Pharmacokinetics, Efficacy, Safety, Tolerability, And Pharmacodynamics Of Satralizumab In Pediatric Patients With Aquaporin-4 Antibody Positive Neuromyelitis Optica Spectrum Disorder (NMOSD)This study will primarily evaluate the pharmacokinetics of satralizumab in pediatric patients aged 2-11 years with anti-aquaporin-4 (AQP4) antibody seropositive neuromyelitis optica spectrum disorder (NMOSD). Efficacy, safety, tolerability, and pharmacodynamics will be evaluated in a descriptive manner, given the small number of patients who will be enrolled in this study.