Increased relapse activity for multiple sclerosis natalizumab users who become nonpersistent: a retrospective study.

BACKGROUND: Natalizumab disease-modifying therapy for relapsing-remitting multiple sclerosis (MS) is efficacious in randomized controlled trials. Few studies have estimated the association between real-world natalizumab persistence behavior and relapse-related outcomes. OBJECTIVES: To (a) examine the impact of using natalizumab consistently (i.e., persistent) on relapse-related outcomes as compared with transitioning to inconsistent natalizumab use (i.e., nonpersistent) and (b) examine the impact of other treatment patterns on relapse-related outcomes for those who initiated natalizumab. METHODS: Using the IMS PharMetrics Plus claims database (years 2006-2012), we identified MS subjects who initiated natalizumab (no natalizumab claims in year prior) and had at least 2 years of follow-up. Persistence in annual follow-up periods was defined as no 90-day or greater gap in natalizumab therapy. Relapse was an MS-related hospitalization or outpatient visit with intravenous or oral steroid burst claim within 7 d...