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

The primary objective of this study is to confirm the efficacy, safety, pharmacokinetics (PK), pharmacodynamics (PD), and immunogenicity of ravulizumab in the treatment of Chinese adults with anti-aquaporin-4 (AQP4) antibody (Ab) + 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.