Endo Pharmaceuticals Holdings Inc. and Penwest Pharmaceuticals Co. said they have received a notice from Actavis South Atlantic LLC advising of the filing by Actavis of an Abbreviated New Drug Application (ANDA) containing a Paragraph IV certification for oxymorphone hydrochloride extended-release tablets CII.

The Actavis Paragraph IV certification notice under 21 U.S.C. Section 355(j) refers to Penwest's US Patent Nos. 5,128,143, 5,662,933, 5,958,456, and 7,276,250, which cover the formulation of OPANA ER. These patents are listed in the FDA's Orange Book and expire in 2008, 2013, 2013, and 2023, respectively. In addition to these patents, OPANA ER has a new dosage form (NDA) exclusivity that prevents final approval of any ANDA by the FDA until the exclusivity expires on June 22, 2009.

Endo and Penwest are currently reviewing the details of this notice from Actavis. Endo and Penwest note that they intend to pursue all available legal and regulatory avenues in defense of OPANA ER, including enforcement of their intellectual property rights and approved labeling.

As previously disclosed, Endo and Penwest also have been notified by IMPAX Laboratories Inc. of its filing of an ANDA containing Paragraph IV certifications for OPANA ER in late 2007. Patent infringement suits against IMPAX are pending in the US District Court for the District of Delaware.