Abstract
BACKGROUND: Natalizumab is a highly efficacious treatment for relapsing-remitting multiple sclerosis (RRMS). OBJECTIVE: To assess the real-world long-term safety of natalizumab in RRMS. METHODS: This multicenter, 5-year prospective observational study, included adults with RRMS newly initiated on natalizumab as per the approved product label in the routine care in Greece. Safety was evaluated by collecting serious adverse events (SAEs) following study enrollment. RESULTS: Between 19-Apr-2012 and 18-Dec-2014, 304 eligible patients (median age at natalizumab initiation: 38.0 years; median disease duration: 6.2 years) were enrolled by 20 hospital-based neurologists. Over a median treatment duration period of 58.7 months, 50.7% of the patients discontinued natalizumab, mainly due to anti-JCV antibody detection (59.1%). The adverse event treatment discontinuation rate was 5.2%. The SAE incidence rate during the safety data collection period (median: 48.7 months) was 4.6%. The most common SAEs were infections (1.0%), including 2 cases (0.7%) of progressive multifocal leukoencephalopathy (PML), and no other opportunistic infections. PML diagnoses occurred 6.2-6.7 years after natalizumab initiation, and approximately 2 years after first detection of anti-JCV antibody for both patients. The incidence rate of malignancies was 0.7%. CONCLUSION: In real-world settings in Greece, natalizumab displayed an acceptable safety profile, with no new safety signals emerging.