By Kim Dixon

WASHINGTON (Reuters) - A U.S. federal court on Wednesday affirmed a ruling that Sanofi-Aventis SA (SASY.PA: Quote, Profile, Research) intended to deceive the patent office in its dispute over generic versions of its blockbuster drug Lovenox.

Sanofi, the world's third-biggest drugmaker, has sued Teva Pharmaceutical Industries Ltd (TEVA.O: Quote, Profile, Research) and Amphastar Pharmaceuticals over their bid to sell a generic version of Sanofi's Lovenox, a blood-thinning drug that had sales of about $1.1 billion in the first quarter of 2008.

The U.S. Court of Appeals for the Federal Circuit ruled that French drugmaker Sanofi-Aventis had committed "inequitable conduct" for failing to inform the U.S. patent office of information relevant to patentability.

The federal court affirmed the ruling by a district court in California that there was an intent to deceive by Sanofi-Aventis in its failing to disclose dosages of the drug in certain studies.

"After a trial on the matter, the district court found there was intent to deceive and held the patents unenforceable for inequitable conduct," the court wrote.

"Because we find no abuse of discretion by the district court in its holding of inequitable conduct, we affirm."

One judge dissented the ruling, arguing that inequitable conduct should be reserved for only the most extreme cases of fraud and deception, which he said did not apply in this case.

The dissent said the failure to disclose details on certain data by an Aventis scientist "may have been careless, but hardly culpable."