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…