Sponsor Strategic Priority Adjustment

The purpose of this study is to initially observe the safety and effectivity of RC18 in Participants 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 the group .If the patients taking leflunomide and teriflunomide,they should need to take colestyramine for elution.
• Have participated in any clinical trial in the first 28 days of the initial screening or 5 times half-life period of the study compound (taking shorter time ).
• The patients have severe psychiatric symptoms and are not compatible with clinical studies
• Malignant tumor patients ;
• patients experienced any of the following events within 12 weeks before screening : myocardial infarction, unstable ischemic heart disease, stroke, or New York Heart Association class IV heart failure
• Patients can't accept magnetic resonance imaging inspection during the trial.
• Infection with herpes zoster or HIV virus at the screening;
• The anti-hepatitis C virus （anti-HCV） of patients show positive;
• Investigator considers candidates not appropriating for the study.