The objectives of this phase Ib study are to evaluate the efficacy, safety, pharmacokinetics, pharmacodynamics and immunogenic profiles of B001 in subjects with aquaporin-4 antibody (AQP4-IgG) positive NMOSD.

Inclusion Criteria:

1. NMOSD as defined by either of the following 2015 criteria with anti-AQP4 antibody (Ab) seropositive status at screening
2. Clinical evidence of at least 1 documented relapse in last 12 months prior to screening
3. Expanded Disability Status Scale (EDSS) score from 0 to 7.5 inclusive at screening
4. Age 18 to 70 years, inclusive at the time of informed consent

Exclusion Criteria:

1. Any previous treatment with anti-CD20, eculizumab, anti-BLyS monoclonal antibody (e.g., belimumab), any other treatment for prevention of multiple sclerosis (MS) relapse (e.g., interferon, natalizumab, glatiramer acetate, fingolimod, teriflunomide or dimethyl fumarate) within 6 months prior to baseline.

2. Received immunosuppression such as azathioprine, mycophenolate mofetil, methotrexate, cyclophosphamide, tacrolimus, mitoxantrone, cyclosporine A, etc, and rug therapy, biological agents such as satralizumab, tocilizumab, eculizumab, etc, 3 months prior to the first administration.

3. Evidence of serious uncontrolled concomitant diseases that may preclude participant participation, as described; Other nervous system disease, cardiovascular disease, hematologic/hematopoiesis disease, respiratory disease, muscular disease, endocrine disease, renal/urologic disease, digestive system disease, congenital or acquired severe immunodeficiency.

4. Known active infection within 3 months prior to baseline

5. Pregnancy or lactation.

6. History of severe allergic reaction to a biologic agent

7. Evidence of chronic active hepatitis B or C

8. Evidence of active tuberculosis

9. Following laboratory abnormalities at screening*:

   1. White blood cells (WBC) <4.0 x10^3/microliter (μL)
   2. Absolute neutrophil count (ANC)
   3. Absolute lymphocyte count <0.5 x10^3/μL
   4. Platelet count <80 x 10^9/ L
   5. Aspartate aminotransferase (AST) or alanine aminotransferase

10. History of drug or alcohol abuse within 6 months prior to baseline

11. Receipt of any live or live attenuated vaccine within 4 weeks prior to baseline

12. Uncontrolled systemic diseases, including hypertension that cannot be effectively controlled after treatment (systolic blood pressure ≥150 mmHg and/or diastolic blood pressure ≥100 mmHg), diabetes, gastrointestinal diseases, etc.; or the investigator believes that there is anything inappropriate reasons for selection.