Background: The anti-CD25 treatment of daclizumab appears to be effective in patients with relapsing remitting multiple sclerosis (RRMS) as regards clinical and MRI outcomes. Moreover, there are no severe safety concerns arising from clinical testing so far.

Objectives: To assess the efficacy and safety of daclizumab for the clinical progression of patients with relapsing remitting multiple sclerosis.

Search methods: We searched the Cochrane Multiple Sclerosis and Rare Diseases of the Central Nervous System Group's Trials Register (February 2012), MEDLINE (January 1966 to February 2012), EMBASE (January 1985 to February 2012). At the same time, we handsearched the references quoted in the identified trials reports (February 2012) from the most important neurological associations and MS Societies. Contacts with researchers participating in trials on daclizumab have been established.

Selection criteria: All randomized controlled clinical trials (RCTs) evaluating daclizumab, alone or combined with other treatments versus placebo, or any other treatment for patients with RRMS.

Data collection and analysis: Two review authors independently assessed references retrieved for possible inclusion. Disagreements regarding inclusion were resolved by consensus. We contacted study authors for additional information. We collected adverse effects information from the trials.

Main results: We identified 470 references from all electronic databases searched excluding duplicate. After screening of titles and abstracts, full papers of 10 studies were obtained and assessed for eligibility. An additional ongoing trial was found. Only one trial (230 participants) evaluating the efficacy of daclizumab versus placebo in interferon beta treated patients was included. It was judged as of high quality study. No significant difference was found in the expanded disability score changes and the annualised relapse rate comparing treated versus placebo groups. No significant difference of common adverse events was found across all the groups at the endpoint. The mean number of new or enlarged gadolinium contrast-enhancing lesions was significantly decreased in the interferon beta and high-dose daclizumab group, compared with that in the interferon beta and placebo group.

Authors' conclusions: Daclizumab is well tolerated in combination with interferon beta treated multiple sclerosis population. Comparing with placebo, high-dose daclizumab can significantly decreased the number of new or enlarged gadolinium contrast-enhancing lesions. However, the evidence of recommendation is insufficient. More well-designed RCTs or crossover controlled trials are required to evaluate the efficacy and safety of daclizumab.