Study of Inebilizumab in Pediatric Subjects With Neuromyelitis Optica Spectrum Disorder

Inclusion Criteria:

• Male or female participants, minimum body weight of 15 kg, age 2 to < 18 years atthe time of screening.

• Positive serum anti-AQP4-IgG result at screening and diagnosed with NMOSD accordingto the criteria of Wingerchuk et al, 2015.

• Documented history of one or more NMOSD acute relapses within the last year, or 2 ormore NMOSD acute relapses within 2 years prior to screening.

Exclusion Criteria:

• Any condition that, in the opinion of the Investigator, would interfere with theevaluation or administration of the Investigational Product or interpretation ofparticipant safety or study results.

• Concurrent/previous enrollment in another clinical study involving aninvestigational treatment within 4 weeks or 5 published half-lives of theinvestigational treatment, whichever is the longer, prior to Day 1.

• Evidence of significant hepatic, renal, or metabolic dysfunction or significanthematological abnormality (one repeat test may be conducted to confirm resultswithin the same screening period).

• B-cell counts < one-half of the lower limit of normal (LLN) for age according to thecentral laboratory.

• Receipt of the following at any time prior to Day 1:

1. Alemtuzumab

2. Total lymphoid irradiation

3. Bone marrow transplant

4. T-cell vaccination therapy

• Receipt of rituximab or any experimental B-cell depleting agent within 6 monthsprior to screening unless B-cell counts have returned to ≥ one-half the LLN.

• Receipt of intravenous immunoglobulin (IVIG) within one month prior to Day 1.

• Receipt of any of the following within 2 months prior to Day 1:

1. Cyclosporine

2. Methotrexate

3. Mitoxantrone

4. Cyclophosphamide

5. Tocilizumab

6. Satralizumab

7. Eculizumab

• Receipt of natalizumab (Tysabri®) within 6 months prior to Day 1.

• Severe drug allergic history or anaphylaxis to 2 or more food products or medicine (including known sensitivity to acetaminophen/paracetamol, diphenhydramine orequivalent antihistamine, and methylprednisolone or equivalent glucocorticoid).

• Diagnosed with a concurrent autoimmune disease that is uncontrolled (unless approvedby the medical monitor).

• Recent receipt of live/attenuated vaccine or blood transfusion.

Receipt of any of the following:

1. Any live or attenuated vaccine within 4 weeks prior to Day 1 (administration ofkilled vaccines and nucleoside-modified mRNA-based vaccines is acceptable; theSponsor recommends that Investigators ensure all participants are up to date onrequired vaccinations prior to study entry).

2. Bacillus Calmette Guérin vaccine within one year of screening.

3. Blood transfusion within 4 weeks prior to screening or during screening.

• Clinically significant serious active or chronic viral, bacterial, or fungalinfection that requires treatment with anti-infectives, hospitalization, or, inthe Investigator's opinion, represents an additional risk to the participant,within 2 months prior to Day 1.

• Known history of congenital or acquired immunodeficiency (e.g., due to humanimmunodeficiency virus [HIV] infection, splenectomy, immunosuppression-relatedor idiopathic T-cell deficiencies) that predisposes the participant toinfection.

• Positive test for chronic hepatitis B infection at screening, defined aseither:

a. Positive hepatitis B surface antigen (HBsAg), or b. Positive hepatitis B core (HBc) antibody (anti-HBc) plus negative hepatitis B surface (HBs) antibody (anti-HBs).

• Positive test for hepatitis C virus antibody.

• Negative test for varicella zoster virus (VZV)-IgG.

• History of cancer, apart from squamous cell or basal cell carcinoma of the skintreated with documented success of curative therapy > 3 months prior to Day 1.

• History of active or latent tuberculosis (TB), or a positive QuantiFERON®-TB Goldtest at screening, unless treatment for TB was completed per local guidelines.Participants with latent TB or a positive QuantiFERON®-TB Gold test who are activelyon anti-TB treatment can enroll if they have completed at least one month of anti-TBtreatment and intend to complete the full course of anti-TB treatment. Participantswith an indeterminate QuantiFERON®-TB Gold test result can enroll if a repeatQuantiFERON®-TB Gold test is negative or a tuberculin skin test is negative.

• For participants who may undergo MRI scans:

1. Unable to undergo an MRI scan (e.g., hypersensitivity to Gd-containing MRIcontrast agents, implanted pacemakers, defibrillators, or other metallicobjects on or inside the body that limit performing MRI scans), or

2. Unable to tolerate or comply with the MRI procedure.