Barr has filed its abbreviated new drug application (ANDA) containing a paragraph IV certification for a generic version of Opana ER with the FDA, and following receipt of the notice from the FDA that Barr’s ANDA had been accepted for filing, Barr notified the new drug application and patent holder.
On October 20, 2008, Endo Pharmaceuticals and Penwest Pharmaceuticals have filed suit in the US District Court of Delaware to prevent Barr from proceeding with the commercialization of its product. This action formally initiates the patent challenge process under the Hatch-Waxman Act.