Modafinil's patent history involves several key developments. The original patent, , was granted to Laboratoire L. Lafon in 1990, covering the chemical compound of modafinil. This patent expired in 2010. In 1994, Cephalon filed a patent for modafinil in the form of particles of a defined size, represented by , which expired in 2015.
Following the nearing expiration of marketing rights in 2002, generic manufacturers, including Mylan and Teva, applied for FDA approval to market a generic form of modafinil, leading to legal challenges by Cephalon regarding the particle size patent. The patent RE 37,516 was declared invalid and unenforceable in 2011.
In addition, Cephalon entered agreements with several generic drug manufacturers to delay the sale of generic modafinil in the US. These agreements were subject to legal scrutiny and antitrust investigations, culminating in a ruling by the Court of Appeals in 2016, which found that the settlements did not violate antitrust laws.