Full results of the Evidence of Interferon Dose-Response-European North American Comparative Efficacy (EVIDENCE) study: a multicenter, randomized, assessor-blinded comparison of low-dose weekly versus high-dose, high-frequency interferon beta-1a for relapsing multiple sclerosis.

BACKGROUND: Interferon (IFN)-beta therapy represents an important advance in the management of relapsing multiple sclerosis (MS), but information about the relative benefits and risks of available preparations is limited.

OBJECTIVE: This report describes the full results of the Evidence of Interferon Dose-response-European North American Comparative Efficacy (EVIDENCE) study, combining analyses that were previously reported in separate publications for different phases of the study.

METHODS: The EVIDENCE study was a multicenter, randomized, assessor-blinded comparison of 2 IFN-beta dosing regimens. In the study, patients with relapsing MS were randomly assigned to SC IFN-beta1a 44 lag TIW (Rebif, Serono Inc., Geneva, Switzerland) or IM IFN-betala 30 mug QW (Avonex, Biogen Idec, Cambridge, Massachusetts) for 1 to 2 years. The primary clinical end point during the comparative phase was the proportion of patients who remained free from relapses; secondary and tertiary clinical end points included the annualized relapse rate and time to first relapse, re- spectively. All clinical and magnetic resonance imaging (MRI) evaluations were performed by blinded assessors. In the crossover phase of the study, patients who were originally randomized to low-dose QW treatment switched to the high-dose TIW treatment for an additional 8 months. Adverse events were determined by spontaneous reporting and monthly laboratory testing during the comparative phase.

RESULTS: A total of 677 patients were enrolled in the study and evenly randomized to treatment; 605 patients completed the comparative phase and 439 completed the crossover phase. During the comparative phase, a significantly higher proportion of patients in the high-dose TIW treatment group remained free from relapses when compared with patients in the low-dose QW treatment group (adjusted odds ratio, 1.5; 95% CI, 1.1-2.0; P = 0.023). The high-dose TIW regimen was also associated with a significant reduction in the annualized relapse rate (-17%; P = 0.033) and a prolonged time to first relapse (hazard ratio, 0.70; P = 0.002). MRI measures of disease activity were significantly reduced in the high-dose TIW group compared with the low-dose QW treatment. During the crossover phase, a 50% reduction in mean relapse rates was observed in patients who converted from low-dose QW treatment to high-dose TIW treatment (P < 0.001), with significant concomitant reductions in MRI activity. Injection-site reactions were significantly more common with high-dose TIW treatment than with low-dose QW treatment (85% vs 33%; P < 0.001). Neutralizing antibody formation was more common with high-dose TIW treatment than with low-dose QW treatment (26% vs 3%; P < 0.001).

CONCLUSIONS: The comparative phase of the EVIDENCE study found that treatment of MS with SC IFN-beta1a 44 microg TIW was associated with a significant reduction in clinical and imaging measures of disease activity over 1 to 2 years, when compared with IM IFN-betala 30 microg QW treatment. The crossover phase found that patients who changed from low-dose QW treatment to high-dose TIW treatment experienced enhanced benefits of treatment without a substantial increase in adverse events.