A Phase III Study of TACI-antibody Fusion Protein Injection (RC18) in Subjects With Neuromyelitis Optica Spectrum Disorders

Inclusion Criteria: * Meet the 2015 international consensus diagnostic criteria for Neuromyelitis Optica Spectrum Disorders and astrocyte water channel aquaporin-4 (AQP4) antibody positivity. * EDSS 0-7.5 * Clinical evidence of at least 2 relapses within the first two years of randomization and/ or 1 relapse within the first one year of randomization * Consent to use effective contraception during the study period (women of childbearing age) * Voluntarily signed informed consent Exclusion Criteria: * Abnormal laboratory parameters need to be excluded, including but not limited to: * Currently suffering from active hepatitis or serious liver disease and medical history * Patients were treated with rituximab or other monoclonal antibodies within 6 months prior to randomization . * Any concomitant disease other than neuromyelitis optica（NMO）/ neuromyelitis optica Spectrum disorders（NMOSD）that required treatment with lucocorticoid. * pregnant , lactating women and men or women who have birth plans during the research; * Have a history of allergic reaction to contrast agent for parenteral administration and human biological medicines. * Receipt of intravenous immune globulin （ IVIG） within 28 days prior to randomization. * Receipt of any of the following prior to randomization: Azathioprine,Cyclosporin, Methotrexate Mitoxantrone,Cyclophosphamide,Tocilizumab,Tacrolimus,Mycophenolate,and Patients discontinued more than 5 times the half-life of the drug before they could get into …