A Phase 2, open-label, multicenter study to evaluate the pharmacokinetics (PK), pharmacodynamics (PD), and safety of inebilizumab in eligible pediatric participants 2 to \< 18 years of age with recently active neuromyelitis optica spectrum disorder (NMOSD) who are seropositive for autoantibodies against aquaporin-4 (AQP4-immunoglobulin \[Ig\]G).