Evidence for the efficacy of interferon beta-1b in delaying the onset of clinically definite multiple sclerosis in individuals with clinically isolated syndrome

The BEtaferon®/BEtaseron® in Newly Emerging MS For Initial Treatment (BENEFIT) trial assessed the efficacy of early versus delayed treatment with interferon beta-1b for patients with clinically isolated syndrome (CIS). Patients were randomly assigned to receive either interferon beta-1b 250 μg every other day (early treatment, n = 292) or placebo (delayed treatment, n = 176) for 2 years or until progression to clinically definite multiple sclerosis. Clinical and magnetic resonance imaging (MRI) outcomes were assessed after 2 years (at the end of the placebo-controlled phase) and then again at 3, 5, and 8 years post randomization. MRI assessments were made after 2, 3, and 5 years. The results showed a consistent advantage of early treatment across most clinical and MRI variables, although median Expanded Disability Status Scale scores remained consistently low, with no differences between groups. These findings suggest that early treatment with interferon beta-1b improves long-term outcomes for patients presenting with CIS.