Mumbai: Eli Lilly and Company, the US-based multinational pharmaceutical major, has sued Indian company Sun Pharmaceuticals in the US, alleging infringement on its patent on Gemzar, a blockbuster cancer drug.

The suit, filed with the Southern District of Indiana, is in response to Sun''s abbreviated new drugs application (ANDA) filed with the US FDA in October 2006 seeking approval for a generic process to manufacture the drug Gemcitabine.

While Eli Lilly''s basic patent on the active pharmaceutical ingredient Gemcitabine hydrochloride will expire on November 15, 2010, another patent on the method to manufacture the drug is valid until 2013. Sun Pharma claimed that the 2013 patent is invalid.

Gemzar, a commonly used cancer drug to treat non-small cell lung cancer, pancreatic, bladder and breast cancer, is one among the top selling drugs of Eli Lilly. The drug had worldwide sales of US $ 1.408 billion in 2006, including sales worth $609.8 million coming from the US market.

Sources said Eli Lilly had earlier sued Sicor In February 2006, Eli Lilly filed a lawsuit against Sicor in the U.S. District Court for the Southern District of Indiana, and in response, Sicor filed a declaratory judgment action in the US District Court for the Central District of California demanding to dismiss the suit, asserting the Indiana court lacks jurisdiction. However, the California court dismissed that case.

Patent experts said the litigations initiated by Eli Lilly will prevent launch of any generic versions of Gemzar by another 30 months, as per the US patent rules.