Long-term clinical experience with weekly interferon beta-1a in relapsing multiple sclerosis.

Post-marketing surveillance studies are needed to assess the long-term safety, compliance and clinical efficacy of interferon beta-1a (IFNβ-1a) therapy in multiple sclerosis (MS) patients. The goals of this study were to (i) assess the safety, compliance and clinical efficacy of long-term intramuscular (i.m.) IFNβ-1a therapy in a large cohort of patients, and (ii) suggest possible predictors of therapeutic response. A total of 255 patients were included in the study. Mean time on therapy was 31.7 ± 19.3 months. Within 3 years, 31% of patients discontinued treatment, mainly for disease activity. No significant sustained blood analysis alteration was observed over time, apart from a decrease of cholesterol levels. After 3 years of treatment, mean Expanded Disability Status Scale (EDSS) scores increased by 0.4 points compared with baseline. The mean annual relapse rate was reduced compared with baseline. Patients with ≤2 relapses in the previous 2 years and with baseline EDSS scores of ≤2 had a longer estimated time to first relapse and to progression and first relapse, respectively. These results confirm the safety and suggest a sustained effectiveness of i.m. IFNβ-1a, extending the reported follow-up period to 6.3 years, and hypothesize the presence of possible predictors of clinical outcome.