Efficacy and Safety of Belimumab in Neuromyelitis Optica Spectrum Disorders

Inclusion Criteria: 1. Male or female patients ≥ 18 years old 2. Diagnosis of NMO or NMO spectrum disorder according to the 2015 International Panel for Neuromyelitis Optica Diagnosis criteria 3. Clinical evidence of either at least one attack requiring rescue therapy (intravenous corticosteroids, intravenous immunoglobulin, plasma exchange, or a combination of these therapies) in the year before screening or at least two attacks requiring rescue therapy in the 2 years before screening. 4. EDSS \<= 6.0 5. Patients were seropositive for AQP4-IgG 6. Able and willing to give written informed consent and comply with the requirements of the study protocol. Exclusion Criteria: 1. Current evidence or known history of clinically significant infection (Herpes simplex virus, varicella-zoster virus, cytomegalovirus, Epstein-Barr virus, human immunodeficiency virus, Hepatitis viruses, Syphilis, etc) 2. Participation in another interventional trial within the last 3 months 3. Tumor disease currently or within last 5 years 4. Pregnant, breastfeeding, or child-bearing potential during the course of the study 5. Clinically relevant heart, liver, kidney or bone marrow function disorder