Interferon β-1a in relapsing multiple sclerosis: four-year extension of the European IFNβ-1a Dose-C omparison Study

Background: Multiple sclerosis (MS) is a chronic disease requiring
long-term monitoring of treatment. Objective: To assess the
four-year clinical efficacy of intramuscular (IM) IFNb-1a in
patients with relapsing MS from the European IFNb-1a Dose-C
omparison Study. Methods: Patients who completed 36 months of
treatment (Part 1) of the European IFNb-1a Dose-C omparison Study
were given the option to continue double-blind treatment with
IFNb-1a 30 mcg or 60 mcg IM once weekly (Part 2). Analyses of
48-month data were performed on sustained disability progression,
relapses, and neutralizing antibody (NA b) formation. Results: O f
608/802 subjects who completed 36 months of treatment, 493 subjects
continued treatment and 446 completed 48 months of treatment and
follow-up. IFNb-1a 30 mcg and 60 mcg IM once weekly were equally
effective for up to 48 months. There were no significant
differences between doses over 48 months on any of the clinical
endpoints, including rate of disability progression, cumulative
percentage of patients who progressed (48 and 43, respectively),
and annual relapse rates; relapses tended to decrease over 48
months. The incidence of patients who were positive for NAbs at any
time during the study was low in both treatment groups. Conclusion:
C ompared with 60-mcg IM IFNb-1a once weekly, a dose of 30 mcg IM
IFNb-1a once weekly maintains the same clinical efficacy over four
years.