Impact of interferon beta-1a on neurologic disability in relapsing multiple sclerosis

A phase III double-blind, placebo-controlled clinical trial demonstrated that interferon beta-la (IFNβ-1a) (Avonex, Biogen) significantly delayed progression of disability in relapsing MS patients. The primary clinical outcome was time from study entry until disability progression, defined as≥1.0 point worsening from baseline Kurtzke Expanded Disability Status Scale (EDSS) score persisting for at least two consecutive scheduled visits separated by 6 months. The objective of this study was to examine the magnitude of benefit on EDSS and its clinical significance.