Endo, Penwest File Lawsuit Against Impax

Endo Pharmaceuticals and Penwest Pharmaceuticals have filed a lawsuit against Impax in the U.S. District Court for the District of Delaware in connection with Impax’s abbreviated new drug application (ANDA) for Opana ER tablets.

The lawsuit is in response to a series of Paragraph IV certification notices Endo and Penwest said were wrongfully served by Impax. These notices said Impax had submitted an ANDA seeking approval to market generic versions of the four dosage strengths of Opana ER (oxymorphone HCl), Endo said.

The lawsuit alleges infringement of certain patents and also seeks declaratory judgment that Impax has no legitimate basis to trigger the Hatch-Waxman ANDA patent litigation process because the FDA has rescinded its acceptance of the ANDA.