Background: The long-term outcomes of inebilizumab in participants from the N-MOmentum trial with a history of immunosuppressant therapy as compared to those without was evaluated. Methods: N-MOmentum (NCT02200770) was a 28-week randomized phase 2/3 trial of inebilizumab vs placebo, with an optional Open-Label Period (OLP) (>2 years). In this post hoc analysis, AQP4+ participants who received inebilizumab (through the OLP) were grouped by no history of immunosuppression therapy beyond treatment of acute NMOSD attacks (naïve), or prior azathioprine (AZA) and/or mycophenolate mofetil (MMF) therapy. Results: Among participants who received inebilizumab during the study, 94 received prior AZA/MMF and 103 were immunosuppressant naïve. Annualized relapse rate (95%CI) for participants with prior AZA/MMF was 0.11 (0.07, 0.17), compared to 0.08 (0.05, 0.14) for naïve. The hospitalization rate (annualized rate [95% CI]) for prior AZA/MMF was 0.15 (0.08, 0.27), and 0.12 (0.06, 0.22) for naïve. Participants with ≥1 study drug-related-treatment-emergent-adverse-event (TEAE) was 30.9% (29/94) in prior AZA/MMF and 46.6% (48/103) of naïve. Most adverse events were infection-related for both groups; 72.3% (68/94) for prior AZA/MMF and 77.7% (80/94) for naïve. Conclusions: This post hoc analysis evaluating long-term outcomes of inebilizumab in AQP4+ NMOSD participants treated with prior AZA/MMF therapy demonstrated a similar efficacy and safety profile as participants without prior immunosuppressant therapy.