Consistent efficacy of daclizumab beta across patient demographic and disease activity subgroups in patients with relapsing-remitting multiple sclerosis

Background: Daclizumab beta is a humanized monoclonal antibody specific for the human interleukin-2 receptor alpha chain (CD25). In two pivotal studies in relapsing multiple sclerosis (MS), patients treated with daclizumab beta exhibited lower annualized relapse rates (ARR) when compared with placebo or with intramuscular (IM) interferon beta-la. Objectives: To determine if the efficacy of daclizumab beta demonstrated in the phase 2 SELECT study and the phase 3 DECIDE study was consistent in patient subgroups. Methods: In the SELECT study, patients received daclizumab beta 150 or 300 mg administered subcutaneously every 4 weeks for 52 weeks, and were compared with patients who received placebo. In the DECIDE study, patients received daclizumab beta 150 mg administered subcutaneously every 4 weeks for 96-144 weeks, and were compared with patients who received IM interferon beta-la 30 mu g. Subgroups were defined by sex, age, the number of relapses in the year before the study, disease duration, baseline disability measured by EDSS, presence of Gd-enhancing lesions, T2 hyperintense lesion volume at baseline, and previous interferon beta-la use. Results: Treatment with daclizumab beta was associated with relative lower ARR, with 95% confidence intervals (CIs) below 1 in 13 of 15 subgroups (SELECT study) compared with placebo and in all 17 subgroups compared with interferon beta-la (DECIDE study). In 2 subgroups in the SELECT study (patients who were older than 35 years of age or who had a disease duration of 10 or more years), the rate ratio point estimate for the ARR was in favor of daclizumab beta but the 95% CI overlapped with 1. The clinical benefits in ARR achieved with daclizumab beta treatment compared with placebo or interferon beta-la across subgroups were similarly supported by reductions in lesion activity on magnetic resonance images (MRIs). Conclusions: These findings suggest that treatment with daclizumab beta is consistently effective among clinically important patient subgroups and support its potential as a viable therapeutic option across the spectrum of relapsing MS.