A Canadian court ruled in favor of Sanofi-Aventis, maker of the top-selling blood thinner Plavix, preventing Apotex from selling a generic version of Plavix in Canada. Plavix is one of the three top-selling drugs in the world with sales of $5.4 billion. Sanofi has a similar suit against Aptoex and Dr. Reddy in the U.S. Apotex and Dr. Reddy argue that the United States patent for active ingredient in Plavix, which expires in 2011, is not sufficiently different from another Sanofi patent that expired two years ago. This could effect Bristol-Myers Squibb’s sales since they divide the profits from Plavix with Sanofi.

Plavix was approved by the FDA in 1997 as the (+)-enantiomer, and its five-year exclusivity period, granted for all New Chemical Entities, expired last year. The first patent covering Sanofi’s oral antiplatelet chiral drug clopidogrel bisulfate (US 4,529,596), was filed in 1983 and expired in July 2003, and claims both enantiomers and their mixture, whereas a later patent (US 4,847,265), due to expire in 2011, claims only the (+)-enantiomer.

The earlier patent claimed, but did not describe, the (+)- and (–)-enantiomers, although it states that “the invention relates both to each enantiomer and their mixture”. In the description of the activities of each enantiomer in the ‘265 patent, data show that the (+)-enantiomer is pharmacologically superior in activity and less toxic than both the (–)-form and the racemate.

Was the development of Plavix as a single enantiomer in the 1980s nonobvious? A problem for Sanofi is that in the 1980s, single enantiomers were already a significant and important component of approved drugs.

See the story here.

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