Neurofilament light levels are associated with long-term outcomes in multiple sclerosis

Background: Neurofilament light chain (NfL) is a promising marker of disease activity/treatment response in multiple sclerosis (MS), although its predictive value for long-term clinical outcomes remains unclear. Objective: We measured NfL from a phase 3 trial in relapsing-remitting MS and investigated its association with outcomes after 8 and 15 years. Methods: NfL concentrations were measured by single molecule array assay in cerebrospinal fluid (CSF) from MS patients (n = 235) in a 2-year randomized clinical trial (RCT) of intramuscular interferon β-1a, and in serum (n = 164) from the extension study. Results: Year 2 CSF and Year 3 serum NfL were associated with brain parenchymal fraction (BPF) change over 8 years (p