Sanofi-Aventis said today it lost a patent infringement case against two generic drug makers involving its top-selling product, the blockbuster bloodthinner Lovenox. Amphastar Pharmaceuticals and Teva Pharmaceutical Industries have been planning to launch generic versions of Lovenox, even though the drug’s patent doesn’t expire until 2012. Yesterday’s trial results may assist those generics companies in achieving their goals. The trial, which took place in the US District Court for the Central District of California, was to determine whether Sanofi-Aventis engaged in inequitable conduct when it initially filed the Lovenox patent. Proving inequitable conduct, which may include submission of incomplete documents when applying for a patent, could invalidate the entire patent. Despite their court victory, Amphastar and Teva face difficulties in getting their versions of Lovenox approved by the FDA. The drug, derived from pig intestines, requires a complex manufacturing process that is difficult to replicate. Lovenox is also under threat by generic drugmaker Momenta Pharmaceuticals, which has reportedly teamed with Novartis’ generics unit Sandoz.Sanofi-Aventis said in a statement that it is “currently evaluating its options for further legal recourse” and will continue to “vigorously defend its intellectual property rights.”In addition to Lovenox, Sanofi-Aventis is also defending its second best selling product, the jointly-marketed antiplatelet agent Plavix, in a US court. Sanofi-Aventis markets Plavix with Bristol-Myers Squibb. Worldwide sales of Lovenox for 2005 were $2.5 billion. Global sales of Plavix were $3.8 billion in 2005.