Efficacy, Safety, Pharmacokinetics, Pharmacodynamics, and Immunogenicity Study of Ravulizumab in Chinese Adults With Neuromyelitis Optica Spectrum Disorder (NMOSD)

Key Inclusion (essential) * Diagnosis: NMOSD per 2015 international consensus criteria, and anti AQP4 antibody positive at Screening. * Disease activity: ≥1 attack/relapse in the past 12 months. * Disability: EDSS ≤7. * Background therapy: If on IST and/or oral corticosteroids, participant should be on a stable maintenance regimen prior to Screening and plan to remain stable during the study unless relapse occurs. (Detailed agent specific duration/dose rules to be confirmed at screening.) * Body weight: ≥40 kg. * Vaccinated against meningococcal infections from serogroups A, C, W, Y (and B where available) within the 3 years prior to study intervention administration on Day 1. Key Exclusion (essential) * Pregnancy/lactation: Pregnant, breastfeeding, or intending to conceive during the study. * Infection risk: History of meningococcal disease or unresolved meningococcal disease, active systemic infection within 14 days, or fever ≥38°C within 7 days before Day 1. * Hypersensitivity: To murine proteins or ravulizumab excipients. * Serious comorbidities: Any condition that in the Investigator's judgment adds risk or interferes with participation/assessment. * Viral infections: Known HIV, active HBV, or active HCV. * Prior/concomitant immunomodulatory treatments: * B cell-depleting therapy (e.g., rituximab, inebilizumab) within 3 months before Screening. * Mitoxantrone or satralizumab within 3 months before Screening. * IVIg within 3 weeks before Screening. * Any prior or current complement inhibitor. Note: Other protocol-defined criteria may apply and should be verified during full eligibility review.