Natalizumab Reduces Clinical and MRI Activity in Multiple Sclerosis Patients with High Disease Activity: Results from a Multicenter Study in Switzerland

Background: Natalizumab has been recommended for the treatment of relapsing-remitting multiple sclerosis (RRMS) in patients with insufficient response to interferon-β or glatiramer acetate (disease-modifying treatments – DMT) or in aggressive MS. The pivotal trials were not designed to investigate natalizumab monotherapy in these patient populations. Aim: To investigate the efficacy of natalizumab after treatment failure of previous DMT and in highly active MS. Methods: A retrospective, multicenter study in Switzerland. Three major MS centers reported all RRMS patients who initiated natalizumab ≧12 months prior to study conduction. Results: 85 RRMS patients were included (72% female, mean age 37.3 years, mean Expanded Disability Status Scale 3.1; 88.2% were pretreated with DMT), and mean treatment duration with natalizumab was 18.4 ± 2.6 months. 79% of the patients were relapse-free during the observational period. The annualized relapse rate decreased from 2.0 ± 0.6 to 0.27 ± 0.2, and 92.9% were progression-free after 12 months (p < 0.001). The mean number of gadolinium-enhancing lesions decreased from 1.2 ± 1.2 to 0.1 ± 0.1 at 12 months’ follow-up (91.7% reduction).Discontinuation rate was 11.8% (7.1% for antibody positivity). Conclusions: Patients who initiate natalizumab after previous high disease activity experience a marked reduction of clinical and MRI disease activity.