Efficacy and Safety of Low-Dose IL-2 in Neuromyelitis Optica Spectrum Disorder

Inclusion Criteria: * Age: 18 to 74 years, inclusive at the time of informed consent. * Diagnosed with NMOSD according to the 2015 international consensus diagnostic criteria for NMOSD. * Expanded Disability Status Scale (EDSS) score between 0 and 6.5. * For women of childbearing potential, contraception must be used for more than 2 weeks after meeting the inclusion criteria, and HCG must be negative at the time of enrollment. * Able to provide written informed consent and demonstrate the ability and willingness to comply with the study protocol requirements. Exclusion Criteria: * Any prior history of receiving whole-body irradiation or bone marrow transplantation. * Any treatment with investigational drugs within 3 months prior to baseline. * Pregnancy or breastfeeding. * Any surgical procedure within 4 weeks prior to baseline (except minor surgeries). * Evidence of other demyelinating diseases or progressive multifocal leukoencephalopathy (PML). * Evidence of severe uncontrolled comorbidities that may hinder participation. * Other neurological disorders, hematological / hematopoietic disorders, congenital/acquired severe immunodeficiencies. * Heart failure (≥NYHA Class III), renal insufficiency, liver insufficiency, or respiratory failure. * White blood cell count \<3000/ml, lymphocyte count \<1000/ml, platelet count \<150,000/ml. * Evidence of chronic active hepatitis B or C. * Substance abuse or alcoholism history within 1 year prior to baseline. * Evidence of active tuberculosis (excluding participants undergoing chemoprophylaxis for latent tuberculosis infection). * Intolerance to IL-2: hypersensitivity reactions to the active substance or any of its excipients (e.g. shock, allergic reactions). * Active suicidal ideation within the past 6 months before screening, or a history of suicide attempts within the past 3 years.