Teriflunomide is a new active drug which has recently been approved as a 
first-line treatment of relapsing forms of MS in the US, Australia, Argentina, 
and the European Union. It is characterized by a once-daily oral application and 
a well-established long-term safety profile. The main therapeutic effect is 
considered to be mediated via the inhibition of the de novo synthesis of 
pyrimidine in proliferating immune cells. Two phase III clinical trials (TEMSO, 
TOWER) tested teriflunomide in patients with relapsing forms of MS: efficacy was 
shown, with positive effects on relapse rates and disease progression for 14 
mg/day. Overall, the safety profile in these studies was favorable. In patients 
treated with teriflunomide, the regular monitoring of blood cell counts and 
liver enzymes is required. Teriflunomide must not be used during pregnancy. In 
this article, we review recent phase II and phase III clinical trial data, and 
discuss the potential of teriflunomide for the treatment of relapsing forms of 
MS.