Sanofi-Aventis is facing another patent challenge to its second best-selling drug, the super-aspirin, Plavix (clopidogrel), this time in the UK. In a statement, the company said its patent in the UK covering the drug’s active ingredient had been challenged by Scotland’s Aircoat.

Plavix is already subject to patent challenges in the US from Dr Reddy’s Laboratories of India and Canada’s Apotex [[07/01/05c]] [[09/12/04e]], but this is believed to be the first time that a European patent on the drug has been threatened. Analysts were unsure how to gauge the threat to Plavix, given that Aircoat is a shell company, and it remains uncertain whether it is acting on its own behalf or one of the generics houses. Patent litigation in Canada is also ongoing.

Sanofi-Aventis said it believes Aircoat’s arguments to be without merit, and will vigorously defend its patent. Plavix accounted for 1.7 billion euros of Sanofi’s total sales of 6.6 billion euros in 2004 – up 29%. The UK market is estimated to account for around 2.5% of total sales of the drug. It is not due to lose patent protection in the US until 2011 and until 2013 in Europe.