Sanofi is celebrating after getting the green light for its multiple sclerosis pill Aubagio.

The US Food and Drug Administration has approved Aubagio (teriflunomide) as a once-daily, oral treatment for patients with relapsing forms of MS. The thumbs-up is based on data from the TEMSO trial and Russell Katz, director of the Division of Neurology Products in the agency’s Center for Drug Evaluation and Research, noted that the results showed the relapse rate for patients using Aubagio "was about 30% lower than the rate for those taking a placebo".

The drug will contain a boxed warning concerning the risk of liver problems, including death, and a risk of birth defects. Doctors should do blood tests to check liver function before a patient starts taking Aubagio and periodically during treatment, the FDA added. The label will also carry a warning noting that, based on animal studies, the drug may cause foetal harm.

David Meeker, head of Sanofi's Genzyme unit, said "we are very excited to introduce Aubagio", adding that "the approval of our first MS therapy represents an important milestone for Genzyme and underscores our commitment to long-term leadership and partnership in the MS community". Timothy Coetzee, chief research officer at the National MS Society in the USA, said “we are greatly encouraged to see a new oral therapeutic option become available" and with "collaborative research underway around the world today, this is an extremely hopeful time for anyone who is diagnosed with MS".

Sanofi noted that the ongoing Aubagio clinical development programme, involving more than 5,000 patients in 36 countries, is amongst the largest of any MS therapy. Some patients in extension trials have been treated for up to 10 years.

The drug will now go up against Novartis' MS pill Gilenya (fingolimod) and the FDA is also expected to approve Biogen Idec's  BG-12 (dimethyl fumarate) soon. Analysts have suggested these two drugs will dominate the MS pill arena and Sanofi, which also has the injectable Lemtrada (alemtuzumab) under review on both sides of the Atlantic, will get a smaller share of the market.