Watson Pharmaceuticals Inc. said Friday it is challenging Takeda Pharmaceutical Co.'s patent on the insomnia treatment Rozerem.
Watson said it asked the Food and Drug Administration to approve 8-milligram ramelteon tablets, a generic version of Rozerem, prior to the drug's patent expiration.
Japan-based Takeda filed a lawsuit against Watson on Wednesday, Watson said. That lawsuit seeks to prevent Watson from selling a generic version of Rozerem prior to the drug's patent expiration. That lawsuit automatically halts final FDA approval of the generic version for up to 30 months, or until a court makes a final decision.
Watson said Rozerem had U.S. sales of about $91 million during the 12-month period ending Sept. 30, according to IMS Health data.