Switching natalizumab to fingolimod within 6 weeks reduces recurrence of disease activity in MS patients

BACKGROUND: Natalizumab is an effective treatment in relapsing-remitting multiple sclerosis (MS). Mainly because of the risk of progressive multifocal leukoencephalopathy (PML), a substantial proportion of John Cunningham (JC) virus-positive patients switch to fingolimod. Previous reports show a clear benefit when the duration of a washout (WO) period of natalizumab is 0-3 months in comparison to longer WO periods. However, there is no consensus regarding the optimal duration of a WO period under 3 months. OBJECTIVE: We compared MS disease activity after different WO periods. In addition, we investigated several factors that possibly influence recurrence of disease activity, including serum natalizumab concentration and lymphocyte counts. METHODS: From a prospective observational cohort study of natalizumab-treated patients, we selected 52 patients who switched to fingolimod. We divided the patients in three groups (8 weeks WO). Serum natalizumab concentration and lymphocyte count were assessed during and after natalizumab treatment. RESULTS: Patients with a WO period of >8 weeks had a significant higher recurrence of disease activity (odds ratio, 6.8; 95% confidence interval, 1.4-32.8) compared to patients with a WO period of