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Background: Treatments used in NMOSD include mycophenolate mofetil (MMF), azathioprine and rituximab. More recently, three treatments were FDA-approved for treatment of aquaporin-4 positive NMOSD: satralizumab, eculizumab and inebilizumab. Given the cost of these new therapies and the evidence for efficacy of rituximab, most patients are started on rituximab first line, and transitioned to an FDA-approved treatment if they relapse.
Methods: Retrospective analysis of relapses and treatment outcomes in patients with NMOSD at Mass General Brigham. Relapses (excluding the index event) classified as clinically convincing as defined by a core NMOSD phenotype were included in this analysis. An absolute lymphocyte count (ALC) of <1.5 x 10³ cells/μL has been suggested as a biomarker for MMF efficacy, therefore ALC at time of relapse was collected when available. Results A total of 100 patients were included. 92.7% were AQP4 positive and 82.5% were female. 63.9% of patients were white and 89.7% were not hispanic. Mean age at diagnosis was 24.4 years (SD 15.9) and median follow-up was 9.91 years (IQR 8.31). A total of 201 relapses from 94 unique patients were analyzed. A total of 59 unique patients received rituximab, compared to 16 for MMF, 7 for MS injectables, 8 for azathioprine, 3 for satralizumab, 2 for inebilizumab and 5 for eculizumab. The failure rate, defined as at least 1 relapse while on a specific treatment, was 88% for azathioprine, 68% for MMF and 35% for rituximab. Patients were most commonly on no DMT (40.1%) at the time of relapse. Most of these were historical relapses from 1980-2000, before DMTs became standard of care. For patients who were on a DMT at time of relapse, the most common DMTs were rituximab (28.3%), MS injectables (18.9%), prednisone (18.9%), MMF (18.1%) and azathioprine (10.23%). The CD19 count was 0 for 10/11 (90.1%) and the CD20 count was 0 for 7/7 (100%) of relapses when available. ALC was <1.5 x 10³ cells/μL for 11/14 (78.5%) of relapses when available. There were no relapses on satralizumab or inebilizumab, and a one relapse on eculizumab which occurred shortly after starting treatment. Median treatment duration was 5.6 years (IQR 7.2) for MMF, 6.7 years (IQR 7.9) for rituximab, 2.4 years (IQR 4.8) for azathioprine, 3.7 years (0.45) for eculizumab, 3.1 years (IQR 0.04) for inebilizumab and 2.3 years (IQR 1.3) for satralizumab. Conclusions A significant proportion of relapses occurred on rituximab despite suppressed B-cells. Similarly, a significant proportion of relapses occurred on MMF despite lymphopenia and most patients failed azathioprine. There was only a single relapse on the FDA-approved treatments. While the number of relapses on rituximab can be partly explained by the longer treatment duration and number of patients treated, the treatment failure rate is substantial. Based on this data, we advocate that NMOSD patients should be initiated on an FDA-approved treatment first-line.
