Effect of interferon beta-1a subcutaneously three times weekly on clinical and radiological measures and no evidence of disease activity status in patients with relapsing-remitting multiple sclerosis at year 1

Background: In the PRISMS study, interferon beta-1a subcutaneously (IFN beta-1a SC) reduced clinical and radiological disease burden at 2 years in patients with relapsing-remitting multiple sclerosis. The study aimed to characterize efficacy of IFN beta-1a SC 44 mu g and 22 mu g three times weekly (tiw) at Year 1. Methods: Exploratory endpoints included annualized relapse rate (ARR), 3-month confirmed disability progression (1-point Expanded Disability Status Scale increase if baseline was < 6.0 [0.5-point if baseline was >= 6.0]), active T2 lesions, and no evidence of disease activity (NEDA; defined as no relapses [subanalyzed by relapse severity], 3-month confirmed progression, or active T2 lesions). Effect of IFN beta-1a SC in prespecified patient subgroups was also assessed. Results: Patients were randomized to IFN beta-1a 22 mu g (n = 189), 44 mu g (n = 184), or placebo (n = 187). At 1 year, IFN beta-1a SC tiw reduced ARR (p < 0.001), risk of disability progression (p <= 0.029), and mean number of active T2 lesions per patients per scan (p < 0.001) versus placebo. Clinical and radiological benefits were seen as early as Month 2 and 3. Outcomes in subgroups were consistent with those in the overall population. More patients treated with IFN beta-1a SC tiw achieved NEDA status, versus placebo, regardless of relapse severity (p <= 0.006). Conclusion: Clinical, radiological, and NEDA outcomes at Year 1 were consistent with Year 2 results. Treatment efficacy was consistent in pre-specified patient subgroups.