Endo and Penwest File Lawsuit Against Impax Laboratories Relating to Opana ER

CHADDS FORD, PA and DANBURY, CT, Jan 25, 2008 (MARKET WIRE via COMTEX News Network) -- Endo Pharmaceuticals Inc., a subsidiary of Endo Pharmaceuticals Holdings Inc. (NASDAQ: ENDP), and Penwest Pharmaceuticals Co. (NASDAQ: PPCO) announced today that they have filed a lawsuit against Impax Laboratories, Inc. in the United States District Court for the District of Delaware in connection with Impax's Abbreviated New Drug Application (ANDA) for Opana ER (oxymorphone HCl) extended-release tablets CII. The lawsuit is in response to IMPAX's notice to Endo and Penwest, announced on December 17, 2007, advising of the FDA's acceptance for substantive review, as of November 23, 2007, of IMPAX's ANDA containing a Paragraph IV certification under 21 U.S.C. Section 355(j) for oxymorphone hydrochloride extended-release tablets CII. IMPAX stated in its Paragraph IV certification notice letter that the FDA requested IMPAX to provide notification to Endo and Penwest of this certification.
IMPAX's Paragraph IV certification notice refers to certain Penwest patents listed in the FDA's Orange Book relating to the formulation of OPANA ER. The complaint filed today alleges infringement of certain of these Orange Book-listed patents.

As previously disclosed, Endo and Penwest filed a lawsuit against IMPAX on November 15, 2007 in the United States District Court for the District of Delaware in response to a series of Paragraph IV certification notices that Endo and Penwest assert were wrongfully served on them by IMPAX. These prior Paragraph IV Certification Notices related to the same Orange Book-listed patents for OPANA ER and were served on Endo and Penwest after the acceptance of IMPAX's ANDA was rescinded by the FDA. Endo and Penwest continue to believe that these prior Paragraph IV Certification Notices are null, void and of no legal effect.

OPANA ER has been granted new dosage form regulatory exclusivity that prevents the FDA from approving any ANDA for a generic version of OPANA ER for launch prior to June 22, 2009, the date such regulatory exclusivity expires.