The US market for Sanofi/Bristol-Myers Squibb's Plavix has been blown wide open after regulators across the Atlantic gave the green light to copycat versions of the companies' mega-blockbuster bloodthinner.

On the day the treatment's patent expired, the US Food and Drug Administration approved generic versions from a number of firms for Plavix (clopidogrel), which treats patients who have had a recent heart attack or a stroke, or have partial or total blockage of an artery. It has been a clinical and commercial success with US sales of $6.7 billion for the year ended March 31, the second biggest-seller behind Pfizer's cholesterol drug Lipitor (atorvastatin).

Now the floodgates have opened and the FDA noted that Dr Reddy's Laboratories, Gate Pharmaceuticals, Mylan and Teva Pharmaceuticals have gained approval for 300mg clopidogrel. Apotex Corp, Aurobindo Pharma,  Roxane Laboratories, Sun Pharma, Torrent Pharmaceuticals, plus Teva and Mylan can now market the 75mg version.

The Apotex case

Apotex had originally been granted exclusivity to sell its generic version but that right was forfeited after the Canadian firm flooded the market in with unauthorised generic Plavix in 2006. B-MS and Sanofi had previously signed a pact with Apotex that would have prevented the launch of the latter’s generic until 2011; B-MS' handling of the situation resulted in civil and criminal fines imposed in the US courts and cost the jobs of senior  management, including chief executive Peter Dolan.

Keith Webber, deputy director of the Office of Pharmaceutical Science in the FDA’s Center for Drug Evaluation and Research, said that "for people who must manage chronic health conditions, having effective and affordable treatment options is important. The generic products approved will expand those options for patients".

B-MS and Sanofi are going to lose a lot of cash, though they have introduced schemes to offer branded Plavix at heavily-discounted rates. Nevertheless, both firms seem to have prepared well for the US patent expiry (generics have been available in Europe for over a year) on the drug.

AZ's Brilinta to benefit?

Observers are watching keenly to see what effect the disappearance of branded Plavix will have on newer agents which have shown superiority to clopidogrel in certain settings, such as Eli Lilly/Daiichi Sankyo's Efient (prasugrel) and, perhaps more notably, AstraZeneca's Brilinta (ticagrelor).

For patients with acute coronary syndrome, the latter has proved to be a effective treatment than clopidogrel in reducing the rate of heart attack and cardiovascular death. AstraZeneca has has just signed a deal with The Medicines Company which will see the firms co-promote Brilinta across the Atlantic, and it will be interesting to see whether the drug's market share  will rise despite the flood of generic Plavix.