Real-World Disability Improvement In Patients With Relapsing-Remitting Multiple Sclerosis Treated With Natalizumab In The Tysabri Observational Program

Background: Natalizumab has been associated with disability improvement as indicated by a confirmed Expanded Disability Status Scale (EDSS) score decrease. Objective: The aim of this study was to characterize disability improvement in patients in the Tysabri Observational Program (TOP), an ongoing observational study of relapsing-remitting multiple sclerosis patients initiating natalizumab in clinical practice. Methods: TOP data as of November 2018 were included. Confirmed disability improvement (CDI) was defined as a decrease > 1.0 confirmed 24 weeks later from a baseline EDSS score > 2.0. Confirmed functional system (FS) improvement was defined as a decrease > 1.0 confirmed 24 weeks later from a baseline score > 1.0 in that FS. Results: Of 5384 patients, 1287 (23.9%) had CDI; 51.8% experienced CDI in the first treatment year. Among patients with CDI, 56.6% had CDI > 1.5 points; 34.4% had CDI > 2.0 points. The cumulative probability of maintaining improvement 8 years after the CDI event was 52.6%. At treatment initiation, 5363 patients (85.2%) had impairment in > 1 FS. At 8 years, the cumulative probability of confirmed improvement in any FS was 88.8% and ranged from 38.3% to 58.6% in individual FS. Conclusion: These results highlight disability improvement as a potential benefit of natalizumab treatment. Improvements across all FS demonstrate the range of functional improvement.