Sanofi fails to win US FDA approval for Genzyme's MS drug Lemtrada

French drugmaker Sanofi failed to win US regulatory approval for its multiple sclerosis drug Lemtrada, hurting the company's plans for cornering a larger share of the $20-billion market for the disease.

According to the US Food and Drug Administration, Sanofi's Genzyme unit failed to submit evidence from ''adequate and well-controlled studies'' showing that the benefits of Lemtrada outweighed its side effects, the Paris-based company said in a statement today. The company said it disagreed with the conclusion and planned to appeal.

''We are extremely disappointed with the outcome of the review and the implications for patients in the US suffering with multiple sclerosis who remain in need of alternative therapies,'' Genzyme chairman and chief executive David Meeker said in the statement.

He said, "We strongly believe that the clinical development program--which was designed to demonstrate how Lemtrada compares against an active comparator as opposed to placebo--provides robust evidence of efficacy and a favorable benefit-risk profile.

"This evidence was also the basis for the approvals of Lemtrada by other regulatory agencies around the world," he added.

Lemtrada, which gained approval in the EU in September, and in Australia and Canada this month, formed a key part of Sanofi's $20.1 billion acquisition of Genzyme in 2011 (See: Sanofi-Aventis extends Genzyme offer, terms unchanged).

According to the company, the FDA indicated one or more additional trials of different design and execution comparing Lemtrada with another drug were needed for approval.

Bloomberg quoted Eric Le Berrigaud, an analyst at Bryan Garnier in Paris as saying it was a big blow for Sanofi, as Lemtrada would have provided a significant growth engine for the company as early as 2014.

Lemtrada, which is an injectable drug also known as alemtuzumab, is meant for use in the treatment of relapsing remitting multiple sclerosis, the most common form of the disease. The drug gained approval in September from European regulators for a  market dominated by rivals Biogen Idec , Novartis and Teva Pharmaceutical Industries .

According to commentators, the FDA ruling could also impact the value of Sanofi's Genzyme takeover since Genzyme shareholders had received so-called contingent value rights (CVRs), which entitled them to future payments of up to $14 a share if certain goals were met.

The company said today it did not expect to meet the CVR milestone of US approval for Lemtrada by the end of March.

Shares in Sanofi retreated 0.8 per cent in early trading at €75.95, giving France's second-biggest listed company a market value of around €101 billion ($139 billion).

US law firm Lieff Cabraser Heimann & Bernstein, LLP, said earlier this month it was launching a class action against Sanofi on behalf of purchasers of the CVRs between 6 March, 2012 and 7 November, 2013.

According to the law firm, Sanofi and some of its senior executives made false and misleading statements about its business and prospects for Lemtrada between 6 March 2012 and 7 November 2013 and had misled investors over the design of its clinical trials on the drug.