A Study of Orelabrutinib in Patients With AQP4-IgG Positive Neuromyelitis Optica Spectrum Disorder

Inclusion Criteria: * 1\) 18-75 years old (inclusive) at the time of signing the informed consent form * 2)Diagnosed with AQP4-IgG positive NMOSD in accordance with 2015 IPND diagnostic criteria. * 3)Relapse ≥ 2 within 1 year before screening, and at least 1 relapse within 6 months before screening * 4)If the subject has stable steroids treatment (≤ 7.5mg prednisone, or equivalent dose of steroids), the treatment needs to be stable more than 1 month before starting the study drug treatment. * 5)EDSS ≤7.5 at screening * 6)Negative pregnancy test for female of childbearing potential at screening * 7)Understood the study procedure and voluntarily signed written informed consent Exclusion Criteria: * 1\) History of serious heart, lung, liver, kidney, blood disease, etc. * 2\) Any major infection judged by the investigator requiring hospitalization and parenteral antimicrobial treatment within 1 month before screening * 3\) History of episodes of herpes zoster ≥ 2 or disseminated herpes zoster ≥ 1 * 4\) History of or having any of the following medication / treatment: ① Received BTK inhibitor at any time in the past; ② B-cell targeted therapy within 12 weeks before the first dose; ③ Received biological agents within 12 weeks before the first dose; ④ Received live virus vaccine or live attenuated vaccine within 8 weeks before the first dose; ⑤ Received steroids treatment for other diseases within 6 months before screening, the dosage \> 20mg / day for more than 21 days; ⑥ Used a study drug or other experimental treatment within 4 weeks before screening or 5 half-lives, or participating in any other intervention clinical trial. * 5\) During screening or baseline examination, laboratory results meet the exclusion criteria: * Human immunodeficiency virus (HIV) positive * Hepatitis C virus (HCV) antibody positive. (If a subject has a history of HCV infection, has completed and recorded appropriate treatment at least 1 year before screening, and the HCV RNA measured by PCR at the time of screening is negative, the subject will not be excluded from this study.) * Hepatitis B surface antigen (HBsAg) positive and / or hepatitis B core antibody (HBcAb) positive * Estimated glomerular filtration rate (eGFR) \< 30 mL/min/1.73 m2 * ALT/AST \> 2 x ULN, Total Bilirubin \> 1.5 x ULN, or any other clinically significant laboratory abnormality * Neutrophil \< 1500 / mm3, platelet \< 75000 / mm3, lymphocyte \< 1000 / mm3 or leukocyte \< 3500 / mm3. * International standardized ratio (INR) ≥ 1.5 or activated partial thromboplastin time (APTT) ≥ 1.5x ULN. * CD19 B cells lower than the lower limit of the normal range * 6\) Used strong to medium CYP3A inducers within 3 weeks before treatment, or strong to medium CYP3A inhibitors within 1 week before treatment, or strong to medium CYP3A inducers or inhibitors may be used during treatment. * 7\) There are situations that other researchers think are not suitable to participate in this study.