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Background: Use of quantitative magnetic resonance imaging (MRI) metrics as surrogates for clinical outcomes in multiple sclerosis (MS) trials is controversial.Objectives: We sought to validate, at the individual-patient level, the number of MRI active lesions, as a surrogate marker for relapses in MS.Methods: Individual-patient data from two large, placebo-controlled clinical trials of subcutaneous interferon β-1a in patients with relapsing–remitting or secondary progressive (SP) MS were analysed separately and as pooled data. The four Prentice criteria were applied to assess surrogacy for the number of new T2 MRI lesions. The predictive value of short-term treatment effects on this MRI marker for longer-term clinical relapses was also assessed.Results: All Prentice criteria were satisfied. The number of new T2 MRI lesions correlated with the number of relapses over the follow-up period. The proportion of treatment effect on relapses accounted for by the effect of treatment on new T2 MRI lesions over 2 years was 53% in patients with relapsing–remitting MS, 67% in patients with secondary progressive MS, and 62% in pooled data. In the pooled data, treatment effects on new lesions over 1 year mediated a good proportion (70%) of effects on relapses over the subsequent year.Conclusions: This study provides evidence that new T2 MRI lesion count is a surrogate for relapses in patients with MS treated with interferon or drugs with a similar mechanism of action. Short-term treatment effects on this MRI measure can predict longer-term effects on relapses. [ABSTRACT FROM AUTHOR]

This study evaluated the efficacy of a new formulation of subcutaneous (sc) interferon (IFN)-β1a in relapsing-remitting multiple sclerosis (RRMS). Patients (n=180) were randomized (2 : 1) to IFN-β1a or placebo for 16 weeks; all patients then received IFN-β1a for 24 weeks. Monthly brain MRI was performed. At week 16, the mean number of combined unique active (CUA) lesions was lower with IFN-β1a than with placebo (p<0.001; 69% fewer lesions). The mean cumulative number of CUA lesions was already lower with IFN-β1a by week 4 (post hoc analysis; p=0.015). The new formulation of sc IFN-β1a has rapid beneficial effects on MRI outcomes in RRMS. [ABSTRACT FROM AUTHOR]