Ofatumumab in AQP4-IgG Seropositive NMOSD

Inclusion Criteria: * Diagnosis of NMOSD according to the 2015 International Panel Diagnostic Criteria for NMOSD with AQP4-IgG. * Clinical evidence of at least 2 relapses (including first attack) in past 24 months with at least 1 relapse occurring in the preceding 12 months. * Adults aged ≥18 years old. * Expanded disability status scale (EDSS) score between 0 and 7.5 (inclusive). * Provision of written informed consent to participate in this study. * Only oral corticosteroids were permitted at screening (≤10mg equivalent per day), which should be terminated within one month. * Effective contraception was used for female patients with fertility during the treatment or at least 3 months after stopping medication. Exclusion Criteria: * Progressive neurological deterioration unrelated to relapses of NMOSD, or presence of neurological findings suspected with PML. * Pregnant or breastfeeding patients and those with family planning during the study period. * Patients participating in any other clinical therapeutic study at the screening or within 30 days of screening. * Patients with splenectomy or history of no spleen, and those with planned surgery (excluding minor surgery) during the study period. * Presence of uncontrolled severe concurrent diseases; long-term glucocorticoids or immunosuppressants use due to other autoimmune diseases, or presence of other chronic diseases that cannot receiving immunosuppression. * Active infection at within 4 weeks before baseline. * Positive for HBV or HCV. * Evidence of latent or active tuberculosis (TB). * Have received any live or live-attenuated vaccine within 6 weeks before baseline. * History of malignancy in past 5 years, including solid tumor, malignant hematopathy and carcinoma in situ. * History of severe allergic reactions to biological agents. * Inability to provide written informed consent.