Approximately 23 subjects will be enrolled.~Experimental drug treatment: Orelabrutinib, 50mg, orally, once a day.~The subject will come to visit at week 0, 1, 2, 4, 8, 12, 16, 20, 24, 36, 48 and safety follow up visit which is planed 28 days after last administration.~Baseline patient assessment:~Baseline examination: vital signs, physical examination, blood routine examination, urine routine examination, liver and kidney function, coagulation function, thyroid function, HIV, HCV, HBV virus test, tuberculosis test, chest X-ray, ECG and pregnancy test.~Functional disability assessment: Expanded Disability Status Scale (EDSS) score and low contrast vision (LCVA) score.~EQ5D scale evaluation.~Serum AQP4-IgG titer, neuro filament light chain, T/B/NK cell count, Immunoglobulin (IgG, IgA and IgM)
Neuromyelitis optica spectrum disorder (NMOSD) is a chronic inflammatory demyelinating autoimmune disease of the central nervous system. NMOSD is a highly relapsing, severely disabling disease. AQP4-IgG positive NMOSD is related to a specific aquaporin 4 antibody (AQP4 IgG) produced by mature B cells. BTK is a key kinase in B cell receptor signal transduction pathway. Abnormal activation of BTK related signaling pathway can lead to autoantibody production and autoimmune diseases. Therefore, BTK can be developed as a new target for autoimmune diseases.