Drugs giant AstraZeneca has filed a legal case in the US to protect its best-selling schizophrenia treatment. The Anglo-Swedish company has begun the action against an Israeli firm, Teva Pharmaceuticals, for alleged patent infringement of its Seroquel drug. The Anglo-Swedish company said it had begun action in U.S. District Court in New Jersey against Teva for “willful infringement” of the substance patent that protects its best-selling schizophrenia treatment Seroquel. The lawsuit is a response to an application filed by Teva in late September with the U.S. Food and Drug Administration to market a generic version of a 25 milligram tablet version of the drug in the United States before AstraZeneca’s patent expires in 2011.