The FDA approved a Canadian company’s application to produce a generic version of Bristol-Myers Squibb’s best-selling drug Plavix.The approval means generic maker Apotex could bring a generic form of the heart medication to market before a key Plavix patent expires in 2011.However, BMS and Sanofi-Aventis have sued Apotex over the validity and enforceability of the patent. A federal trial is scheduled for April.BMS “continues to believe that the patent is valid and that it is infringed, and with its alliance partner and patent-holder Sanofi-Aventis, is vigorously pursuing these cases,” BMS said in a statement.If the patent is held invalid, Apotex — the first generic to file with the FDA — stands to gain 180 days of generic market exclusivity on clopidogrel bisulfate. Plavix had 2005 US net sales of $3.2 billion.