On November 2, 2011, Finnegan client Cephalon filed suit against Breckenridge Pharmaceutical Inc. and Natco Ltd. for infringing a patent for Nuvigil®. The suit is in response to an abbreviated new drug application (ANDA) and a filed Paragraph IV certification claiming that Cephalon's patent either was invalid or would not be infringed by their generic product. Cephalon asked the court to block the defendants from selling their generic drug before its patent expires.