Abstract: We included two trials with 851 patients that evaluated the efficacy and safety of daclizumab versus placebo for RRMS. We judged them to be at low risk of bias. Due to different time point evaluations and available data on primary studies, we were unable to undertake a meta-analysis. At 24 weeks, the median change was 0 (range -2 to 3) in the interferon beta and placebo group, 0 (-2 to 4) in the interferon beta and low-dose daclizumab group and 0 (-2 to 2) in the interferon beta and high-dose daclizumab group in 230 participants. The proportion of patients who had new clinical relapses were the following: 16 patients (21%) in the interferon beta and high-dose daclizumab group, 19 (24%) in the interferon beta and low-dose daclizumab group and 19 (25%) in the interferon beta and placebo group had relapses (P value = 0.87). At 52 weeks, the changes in Expanded Disability Status Scale (EDSS) from baseline was 0.09 ± 0.71 in placebo group, -0.08 ± 0.52 in low-dose daclizumab group and 0.05 ± 0.61 in high-dose daclizumab group in 621 participants. There was a significant difference between placebo and low-dose daclizumab groups (P value = 0.01), but no significant difference between placebo and high-dose daclizumab groups (P value = 0.49). The proportion of patients with new relapsing MS was significantly reduced in both daclizumab groups (19% in low-dose daclizumab group, 20% in high-dose daclizumab group) compared with placebo group (36%) (P value < 0.0001 and P value = 0.00032, respectively). There was no increased number of patients in any adverse events (risk ratio (RR) 0.98, 95% confidence interval (CI) 0.89 to 1.07) or serious adverse events in daclizumab groups compared with placebo (RR 1.15, 95% CI 0.29 to 4.54). Infections were the most frequent adverse events in treated participants and were resolved with standard therapies. One trial was still ongoing. There was insufficient evidence to determine whether daclizumab was more effective than placebo in patients affected by RRMS in terms of clinical and MRI measures of outcomes. Daclizumab appeared to be relatively well tolerated. Infections were the most frequent adverse events, and were resolved with standard therapies.

Plain-language summary: To test the efficacy we measured the disability changes and the proportion of patients who had new relapses, while to test the safety we took into account the number of patients who exhibited any type of adverse events. We searched scientific databases for randomised controlled trials (clinical studies where people are randomly put into one of two or more treatment group) comparing daclizumab, alone or with other treatments versus placebo (a pretend treatment). Patients were aged 18 to 65 years with relapsing remitting multiple sclerosis. Evidence is current to May 2013. We found two studies (funded by Facet Biotech/Biogen Idec and Biogen Idec/AbbVie Biotherapeutics Inc), which met our inclusion criteria, with 851 patients, both male and female, aged 18 to 65 years. The results did not provide sufficient evidence on the effectiveness of daclizumab, and further studies are needed. One study is still ongoing. Daclizumab was generally well-tolerated, the most frequent adverse events being infections, which were all resolved with standard therapies. In order to have more clear results, the length of follow-up (where the patients are observed and monitored following treatment) needs to be longer. We considered both studies to be of high quality.