Pharma major Pfizer has filed a lawsuit against Ranbaxy and Teva, alleging infringement on its product Accupril (generic Quinapril). Teva and Ranbaxy together launched this product in the US market last December.

Teva is already learnt to have captured close to 45% market share in this product. Quinapril’s total sales are estimated to be around $550m.

Pfizer reportedly filed the lawsuit in the last week of January in the district court of New Jersey, claiming infringement on its ’450 patent’. Pfizer has claimed that Ranbaxy’s formulation contains an ingredient which leads to infringement.

Quinapril, belonging to a class of drugs called ACE inhibitors, is indicated for treating hypertension. An analyst report issued recently said the lawsuit filed by Pfizer puts Ranbaxy/Teva’s launch at risk and a loss in the litigation will lead to damages.

Teva was granted six-month marketing exclusivity for this product by the US Food and Drug Administration (USFDA) last year. As the Israeli generics company’s product was facing an infringement challenge from Pfizer, it relinquished its exclusive rights and entered into an agreement with Ranbaxy, under which the latter manufactures and supplies the product to Teva, which markets the product under its own brand name.

Ranbaxy has also obtained a USFDA approval for this drug and its product was not facing any legal challenge from the originator earlier. Pfizer’s original patent was supposed to expire in February ’07.