Watson Pharmaceuticals Inc. (WPI) said it became the latest drug maker to win a license to sell a generic version of Opana extended-release pain-relief tablets in coming years after a patent dispute settlement with Endo Pharmaceuticals Holdings Inc. (ENDP).

Opana ER has been a source of continuing patent litigation for the developers. Endo and Penwest Pharmaceuticals Co. (PPCO) earlier this year agreed to grant separate licenses for Novartis AG's (NVS, NOVN.VX) Sandoz Inc. unit and Impax Laboratories Inc. (IPXL) to sell generic versions of the drug in 2012 and 2013, respectively.

Watson will have the right to launch its version--at various dosing levels--starting in September 2012, it said.

Sales for the Opana franchise rose 34% in the latest quarter for Endo to $73.8 million.

Opana ER is used to relieve moderate to severe pain in patients requiring around-the-clock treatment for an extended period of time, according to a website for the drug.

Watson shares closed Wednesday at $44.25 while Endo finished at $34.14. Neither was active premarket.

 
   -By Matt Jarzemsky, Dow Jones Newswires; 212-416-2240; matthew.jarzemsky@dowjones.com