To assess the efficacy and safety of Inebilizumab in Chinese adult patients with neuromyelitis optica spectrum disorders.

Inclusion Criteria:

• Patients who have comprehensive understanding of the study content, process and possible adverse reactions, and sign the informed consent forms voluntarily
• Men and women 18 years or older
• Patients with NMOSD diagnosed according to the definition in the Guidelines for the Diagnosis and Treatment of Neuromyelitis Optica Spectrum Disorders in China
• Patients with positive serum anti-AQP4-IgG results at screening
• A documented history of one or more NMOSD acute relapses that required rescue therapy within the last year, or 2 or more NMOSD acute relapses that required rescue therapy within 2 years prior to screening
• Patients with EDSS score of ≤ 7.5 points
• Patients who and whose sexual partner agree to take highly effective method of contraception from screening

Exclusion Criteria:

• Patients who have received any of the following treatments at any time prior to randomization:

  1. Monoclonal antibodies against CD52: such as alemtuzumab, etc.
  2. Total lymphoid irradiation
  3. Bone marrow transplant
  4. T-cell vaccination therapy

• Receipt of rituximab or other B-cell depleting agents (e.g., Belimumab, Telitacicept) within 6 months prior to screening, unless the patient has B-cell counts above the LLN according to the central laboratory;

• Receipt of rituximab or other B-cell depleting agents (e.g., Belimumab, Telitacicept) within 6 months prior to screening, unless the patient has B-cell counts above the LLN according to the central laboratory;

• Patients who have received intravenous injection of immunoglobulin (IVIG) within 1 month prior to randomization;

• Patients who have received immunosuppressant therapy (e.g., cyclophosphamide, methotrexate, mitoxantrone, ciclosporin A, etc.) and biologics (satralizumab, natalizumab, tocilizumab, eculizumab, etc.) within 3 months or 5 half-lives of such drugs (whichever is longer) before randomization;

• Any concomitant disease other than NMOSD that required treatment with oral or IV steroids at doses > 20 mg/day for > 21 days within the 6 months prior to screening;

• Concurrent/previous enrollment in another clinical study involving an investigational treatment within 4 weeks or 5 published half-lives of the investigational treatment, whichever is the longer, prior to enrollment;

• Severe drug allergic history or anaphylaxis to two or more food products or medicine (including known sensitivity to acetaminophen/paracetamol, diphenhydramine or equivalent antihistamine, and methylprednisolone or equivalent glucocorticoid); Known history of allergy or reaction to any component of the investigational product formulation or history of anaphylaxis following any biologic therapy;

• Patients with evidence of alcohol, drug, or chemical abuse, or with history of such abuse within 1 year prior to randomization;

• Female patients who are lactating or pregnant, or plan to become pregnant at any time from signing the informed consent through the study plus 6 months following last dose of investigational product;

• Patients with clinically significant serious active or chronic viral infection, or bacterial infection within 60 days prior to randomization, which requires treatment with anti-infective agents or hospitalization, or might pose an additional risk to the patient in the opinion of the investigator;

• Patients with known history or underlying disease of primary immunodeficiency (congenital or acquired), such as human immunodeficiency virus (HIV) infection or splenectomy, which predisposes the patient to infection;

• Confirmed positive serology results of hepatitis B/C at screening

• Patients with history of malignancy, except squamous or basal cell carcinoma of skin that has been successfully treated with documented success of curative therapy > 3 months prior to randomization;

• Any other conditions that, in the opinion of the investigator, are not suitable for participating in the clinical study.