Sanofi-Aventis says that it is bringing a lawsuit against Novopharm in Canada in a bid to protect the patent on its top-selling clot-busting therapy, Lovenox (enoxaparin).

In a statement, Sanofi-Aventis said it had seen on the Canadian Ministry of Health’s website that Novopharm had won marketing approval for a product claiming to be a generic version of the 1.7 billion euros-a-year drug. The French drug giant said it would “vigorously defend its legal rights with respect to [the] patent.”

This is not the first time that the company has faced the threat of generic competition to this key drug. Back in 2003, Aventis - which was acquired by Sanofi-Synthelabo last year - filed patent infringement lawsuits in the US after generics companies Amphastar and Teva sought approval for their copycat versions of Lovenox, asserting that the main patent covering the drug – due to expire in 2012 – was invalid [[05/08/03c]], [[26/06/03a]], [[28/07/03d]].