Paris, France - It appears that a generic version of the low-molecular-weight heparin enoxaparin (Lovenox, Sanofi-Aventis) may be on the horizon in the US.

The US Court of Appeals has upheld a ruling made last year that the patents on Lovenox are unenforceable, Sanofi-Aventis reports [1]. The 2007 case, which was heard in the US District Court for the Central District of California, was brought by generics companies Teva Pharmaceuticals and Amphastar Pharmaceuticals, which have applied for FDA approval of generic versions of Lovenox. Sanofi-Aventis says it is "considering all its legal options."

"While several generic manufacturers have requested marketing approval from the FDA for their products alleged to be generic versions of Lovenox, Sanofi-Aventis has not learned of any FDA approval of these requests," the company added.

The Wall Street Journal reports that in the 2007 hearing, the patents for Lovenox were ruled unenforceable "because Sanofi-Aventis had engaged in "inequitable conduct when it initially sought issuance of the patents from the US Patent and Trademark Office. [2]" The court found that the company intended to deceive the patent office by failing to disclose certain information, the newspaper notes.

A key patent for Lovenox, which had sales of $4 billion last year, is set to expire in 2012.

This is the second major patent setback for Sanofi-Aventis in recent days. Last week, Swiss company Schweizerhall announced that it was launching a generic version of clopidogrel (Plavix, Sanofi-Aventis) in Europe, which it claimed did not infringe the Plavix patent. Clopidogrel is the second-best-selling drug in the world, with worldwide sales last year of $7.3 billion.