Sustained Efficacy of Natalizumab in the Treatment of Relapsing-Remitting Multiple Sclerosis Independent of Disease Activity and Disability at Baseline: Real-Life Data From a Swiss Cohort

Objectives: Therapy for relapsing-remitting multiple sclerosis with natalizumab (Tysabri; Biogen Idec) has been shown to be effective in the reduction of the clinical relapse rate and disability progression. However, real-life longitudinal data, including years before baseline, are rare. Methods: An observational single-center study was carried out. We analyzed data from 64 consecutive patients with multiple sclerosis. Results: After 1 year of treatment (n = 64), score on the Expanded Disability Status Scale (EDSS) decreased by 0.47 points (P = 0.047) and the annualized relapse rate (ARR) decreased by 82% (P < 0.001). After 2 years (n = 41), EDSS score was still reduced by 0.28 (not significant) and ARR was reduced by 69% (P < 0.001). After 3 years (n = 23), EDSS score was reduced by 0.26 (not significant), and ARR was reduced by 77% (P < 0.001). Reduction of EDSS score and ARR did not depend on baseline ARR (1-2 vs 92) or EDSS score and was not biased by exceptional high disease activity or relapses around baseline. Conclusions: These real-life data reinforce that natalizumab is effective over years, reduces ARR, and stabilizes EDSS score independent of baseline ARR, baseline EDSS score, or baseline treatment.