Evidence of interferon β-1a dose response in relapsing-remitting MS

Abstract

Objective: To compare efficacy of interferon β-1a, 22 μg or 44 μg weekly, with placebo in relapsing MS.Background: Uncertainty exists concerning the optimal dose regimen for interferon β in relapsing-remitting MS. Many patients and physicians prefer the convenience and lesser side effects of an injection given once weekly (qw) as opposed to three times weekly. Pharmacokinetic data and information on biologic markers suggest that this frequency may be suboptimal.Methods: Randomized, double-blind study of interferon β-1a 22 μg, 44 μg, or placebo administered by weekly subcutaneous injection for 48 weeks. Proton density (PD)/T2-weighted and T1-weighted–gadolinium MRI scans during 24 weeks of therapy were analyzed for the number of combined unique (CU) lesions (primary outcome). Biannual PD/T2 scans were analyzed for T2 activity and burden of disease (BOD).Results: CU lesions at 24 weeks had a median of 0.71/scan with placebo, 0.5/scan with 22 μg (not significant), and 0.33/scan with 44 μg (p = 0.002). T2 new lesion count/scan (mean/median) at 48 weeks was 3.2/1.5 for placebo, 2.4/1.0 for 22 μg (p = 0.03), and 1.5/1.0 for 44 μg (p = 0.0005). BOD at 48 weeks showed a median increase of 5.9% for placebo compared with a decrease of 1.4% in the 44 μg group (p = 0.0058) and 2% in the 22 μg group (p = 0.0018). No clinical variable, apart from steroid use in the 44 μg qw group (p = 0.014), showed significance.Conclusions: These data confirm an MRI benefit of interferon β-1a at low dose in MS, but highlight the limited clinical effect. Taken together with other studies, the data demonstrate a dose–effect relationship for both clinical and MRI variables.