Background: 'No evidence of disease activity' (NEDA) is increasingly used as a treatment target with disease-modifying drugs for relapsing multiple sclerosis.

Methods: This post-hoc analysis of the randomised EVIDENCE trial compared interferon beta-1a injected subcutaneously three times weekly (IFN β-1a SC tiw) with interferon β-1a injected intramuscularly once weekly (IFN β-1a IM qw) on NEDA and clinical activity-free (CAF) status. The influence of the frequency of magnetic resonance imaging (MRI) scanning on NEDA and the effect of baseline T1 gadolinium-enhancing (Gd+) lesions on NEDA and CAF were also investigated.

Results: More patients in the IFN β-1a SC tiw group achieved NEDA compared with the IFN β-1a IM qw group, although rates were lower when monthly MRI scans through 24weeks were included (35.0% vs. 21.6%, respectively; p<0.001) versus the 24-week scan alone (59.5% vs. 41.2%; p<0.001). Absence of baseline Gd+ lesions predicted NEDA through Week 72 in the IFN β-1a IM qw group (p=0.022), and CAF through Week 48 in patients receiving IFN β-1a SC tiw (p=0.024).

Conclusions: IFN β-1a SC tiw was associated with significantly higher rate of NEDA status compared with IFN β-1a IM qw. Baseline Gd+ lesions augured less frequent CAF or NEDA status. Inclusion of more MRI scans in the analysis reduced rates of NEDA status.