Efficacy, Safety, PK, PD, and ADA of Eculizumab in Chinese Adults With NMOSD

Inclusion Criteria: * Participants with diagnosis of NMOSD as defined by the 2015 international consensus diagnostic criteria * Anti-AQP4 antibody positive * At least 1 attack or relapse in the last 12 months prior to the Screening Period * EDSS score ≤ 7 * If a participant enters the study receiving IST(s) for relapse prevention, the participant must be on a stable maintenance dose of IST(s) as follows, prior to screening and must remain on that dose for the duration of the study, unless the participant experiences a relapse * Female participants of childbearing potential must have a negative pregnancy test (serum HCG at screening * Male participants are eligible to participate if they agree to the following during the study intervention Treatment Period and for at least 5 months after the last dose of study intervention: * Refrain from donating fresh unwashed semen. PLUS, either, * Be abstinent from heterosexual intercourse as their preferred and usual lifestyle (abstinent on a long term and persistent basis) and agree to remain abstinent. OR * Must agree to use barrier as detailed below: * Agree to use a male condom when having sexual intercourse with a WOCBP who is not currently pregnant. Exclusion Criteria: * Pregnant, breastfeeding, or intending to conceive during the course of the study * Prior history of N meningitidis infection or unresolved meningococcal disease * Any systemic bacterial or other infection which is clinically significant in the opinion of the Investigator and has not been treated with appropriate antibiotics * Presence of fever ≥ 38 C within 7 days prior to study intervention administration on Day 1 * Hypersensitivity to murine proteins or to one of the excipients of study intervention * Use of rituximab, inebilizumab, or other B cell-depleting therapy within 6 months prior to Day 1 and during the study * Use of mitoxantrone or satralizumab within 3 months prior to screening and during the study * Use of IVIg within 3 weeks prior to screening * If a participant enters the study receiving oral corticosteroid(s) with or without other ISTs, the daily corticosteroid dose must be no more than prednisone 20 mg/day (or equivalent) prior to screening and the participant must remain on that dose for the duration of the study or until the participant experiences a relapse (specific medications listed in Section 6.9.1 may be allowed) * Has previously received treatment with C5 inhibitors * Participation in any other investigational drug study or exposure to an investigational drug or device within 5 half-lives of treatment (if known) or 30 days, which is longer, before the first dose administration