Effectiveness of rituximab versus oral immunosuppressive therapies in neuromyelitis optica spectrum disorder in a racially diverse cohort of subjects: A single-center retrospective study.

Background: Neuromyelitis optica spectrum disorder (NMOSD) is an autoimmune, inflammatory disorder characterized by severe relapses and high level of disability. In clinical trials of NMOSD, Black patients are under-represented, < 12%, compared to a relatively high prevalence of NMSOD in this population, 10/100,000. Despite the higher prevalence of NMOSD in Black and Asian patients, there is limited knowledge of the effectiveness of disease modifying treatments across racially diverse groups.

Objective: To assess the effectiveness of rituximab and oral immunosuppressive agents in a cohort of NMOSD patients, the majority of whom are Black, in a real-world, clinical setting.

Methods: A single-center retrospective study was conducted at the University of Chicago Medical Center.

Inclusion Criteria: (1) diagnosis according to the 2015 International Panel for NMO Diagnosis (IPND) Criteria, (2) positive anti-aquaporin-4 antibodies on ELISA or cell-based tests, (3) initiation of immunosuppressant therapy within 5 years of disease onset, (4) first-line treatment with rituximab, mycophenolate (MMF), or azathioprine (AZA). Patients with negative anti-AQP4 titers were excluded. Kaplan-Meier survival analysis was used to estimate proportion of relapse-free patients following initiation of first line immunosuppressive therapy. A Cox proportional hazards regression model assessed the association of risk of relapsing with first-line immunosuppressive treatments with and without adjustments of pre-specified factors (age at disease onset, duration of disease, sex, race, CNS location of relapse).

Results: 7 of 29 patients (24%) receiving rituximab experienced a relapse within the first 3 years of treatment vs. 13 of 23 patients (57%) receiving either AZA or MMF. Within the first 6 months of treatment, 2 (6.9%) patients treated with rituximab experienced a relapse vs. 7 (30.4%) patients treated with either MMF or AZA. In the 29 patients treated with rituximab, the 1-year and 3-year proportion of relapse-free patients was 88.8% and 70.9%. For the 23 patients treated with either AZA or MMF, the 1-year and 3-year proportion of relapse-free patients was 69.5% and 38.7%. In the univariate analysis, the risk of relapse was significantly higher in patients treated with AZA or MMF compared to those treated with rituximab (hazard ratio [HR] of 2.48 [0.99 - 6.21]; p = 0.046).

Conclusion: In this real-world study involving a majority of Black NMOSD patients, rituximab was relatively more effective in preventing relapses within 3 years of therapy initiation than AZA and MMF. Rituximab remains an effective option for treating NMOSD, especially when there are delays in treatment due to access and economic issues associated with newer treatments.