Rebif® (interferon beta-1a) continues to demonstrates efficacy in treating clinically isolated syndrome and reducing conversion to MS


A single episode of neurological symptoms which lasts at least 24 hours and are suggestive of multiple sclerosis is called clinically isolated syndrome (CIS). Not all people with CIS go on to develop MS, however those with a CIS who display tissue damage on MRI are at a higher risk of conversion. Until recently, CIS was not listed as a type of MS but is now recognized as the earliest form of relapsing-remitting MS. Researchers are exploring the effects of disease-modifying therapies on those with high-risk CIS to determine if they are successful in delaying further neurological activity and diagnosis of MS. Current MS drug interferon beta-1a – marketed by pharmaceutical company EMD Serono as Rebif® – is available in Canada for the treatment of relapsing-remitting MS. In 2012, evidence demonstrating efficacy of Rebif® in treating CIS led to its approval for this indication. Since then, further research has been done to define the optimal dose of Rebif® to treat CIS and better understand how therapy benefits those who are at risk for developing MS.

The Study

REFLEX (REbif® FLEXible dosing in early MS) was a two-year, double-blinded, placebo-controlled study that investigated the effects of interferon beta-1a (Rebif® 44mcg) in 517 individuals with CIS. Participants were chosen at random to receive one of the following treatments: Rebif® 44mcg three-times weekly, Rebif® 44mcg once weekly and placebo. Researchers recorded relapse rates and MRI activity for participants in each group over a two year period, and measured the time to conversion to MS.


Results from the study found that time to conversion to MS following a CIS was reduced by just over 50% for those treated with three-times weekly Rebif® 44mcg versus placebo. Both Rebif treatment groups (once a week and three times weekly) demonstrated a reduction in time to conversion to MS compared with placebo at two years however the three-times weekly Rebif® group demonstrated a significantly higher reduction than the once weekly Rebif® group. This study also showed that Rebif® (three times a week) significantly improved magnetic resonance imaging (MRI) outcomes and delayed relapses compared with placebo at two years.


This study provides additional clinical evidence of the benefits of early treatment in those who experience clinically isolated syndrome that are at high-risk of conversion to MS. EMD Serono will continue to work with public plans in an effort to make Rebif® available to Canadians diagnosed with CIS. To date, the provinces of Ontario and Quebec have included Rebif® to their formularies for treatment of individuals with CIS.


Freedman, MS et al. (2014) Patient subgroup analyses of the treatment effect of subcutaneous interferon b-1a on development of multiple sclerosis in the randomized controlled REFLEX study. J Neurol 261:490–499.