NEW YORK (AP) — Generic drug maker Mylan Inc. said Thursday it is seeking approval for four drugs, including low-cost versions of the sleep aid Lunesta and cancer pill Tarceva, and is being sued by the makers of each product. The Pittsburgh-based company said it was being sued for patent infringement after filing for Food and Drug Administration approval of the four drugs. Mylan requested approval for three doses each of Lunesta and Tarceva, as well as the kidney disease drug Fosrenol and Oracea, a treatment for rosacea. The suits variously name Mylan, its subsidiaries Mylan Pharmaceuticals and Alphapharm, and Matrix Laboratories, an Indian drug maker in which Mylan holds a majority stake. The company said it was the first company to file applications for generic versions of those drugs, which would give Mylan a period of marketing exclusivity after the drugs are approved. The lawsuits will likely prevent FDA approval of the generics for the next two and a half years, unless a district courts invalidates the patent or the companies choose to settle. Mylan filed an abbreviated new drug application for Lunesta in 1 mg, 2 mg and 3 mg strengths, and was sued by the drug's maker, Marlborough, Mass.-based Sepracor Inc. Mylan said U.S. sales of Lunesta totaled of $796 million in 2008. OSI Pharmaceuticals Inc., Pfizer Inc. and Genentech Inc. sued after Mylan asked for approval of its version of Tarceva, or erlotinib, in doses of 25 mg, 100 mg and 150 mg. Tarceva is approved to treat pancreatic cancer and lung cancer, and Mylan said U.S. sales were $492 million in 2008. OSI said last week it was suing Mylan and Teva Pharmaceutical Industries Ltd., the world's largest generic drug maker, for violating three patents supporting Tarceva. U.S. and Canadian subsidiaries of U.K.-based Shire PLC sued Mylan to uphold the patents behind 500 mg, 750 mg and 1000 mg chewable Fosrenol tablets. Mylan said U.S. sales reached $108 million last year. Mylan is also looking to market a generic version of 40 mg Oracea tablets, and was sued by Galderma Laboratories Inc., the Research Foundation of the State University of New York and New York University.