Mumbai: After moving court against Indian generic drug maker Wockhardt Ltd and three global copy drug makers in early November, US drug multinational Eli Lilly and Co. Ltd is litigating against two more Indian drug makers—Aurobindo Pharma Ltd and Lupin Ltd—on charges of patent infringement.

These firms had filed the so-called Para 4 applications to the US Food and Drug Administration in June, seeking copy marketing approval for Lilly’s top selling anti-depressant drug Cymbalta in the US.

In a petition filed on 24 November at the US district court for the southern districts of Indiana, against Lupin and its local subsidiary Lupin Pharmaceuticals Inc., Lilly has said US patent no. 5023269, which expires on 11 June 2013, was issued to it by the US patent and trademark office. The expiration date includes a five-year term extension. Cymbalta, the second largest revenue earner for Eli Lilly with about $2.3 billion sales in 12 months ended September, has been patented by the company in 1991 in the US.

Eli Lilly’s petition against Aurobindo was also filed on the same day on charges of Cymbalta patent infringement.

A spokeswoman for Aurobindo confirmed the development but Lupin, as policy, does not comment on such matters. Cobalt Laboratories Inc., Impax Laboratories Inc. and Sandoz Inc. were the other three generic drug companies, which had been sued by Eli Lilly in the second week of November on charges of infringing Cymbalta patent in the US.

The six companies against whom Lilly moved court had applied for marketing approval of copy version under an abbreviated new drug application in June.

Though litigation against generic applicants is not uncommon, Lilly’s argument on patent extension on a new drug application is dubbed by generic lobbies as a strategy to prevent cheap copies.