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 (IFNb-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.) IFNb-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. IFNb-1a, extending the reported follow-up period to 6.3 years, and hypothesize the presence of possible predictors of clinical outcome. Introduction Interferon b-1a (IFNb-1a, Avonex; Biogen Idec, Inc, Cambridge, MA, USA) has shown beneficial effects in patients with multiple sclerosis (MS), reducing relapses and disability progression [1,2], and in patients with a first demyelinating event, reducing the rate of developing clinically definite MS [3]. However, long-term efficacy, safety, and compliance to IFNb-1a have not been sufficiently demonstrated [4], as randomized, blinded, controlled trials are expensive and usually last for a short time. Disease modifying treatments systemic effects are usually monitored through blood analysis. The effects of all the available IFNs have been studied giving controversial results. The most frequent effects are liver enzymes changes, thyroid function alterations, hematological effect and blood lipid changes. A multicenter, dose-comparison study to assess differences in therapeutic response between two doses of weekly IFNb-1a has been reported [5,6], and is the only study to provide information about longterm (> 3 years) therapy with weekly intramuscular (i.m.) IFNb-1a. Several studies