(Reuters) - Allergan Plc said it and Adamas Pharmaceuticals Inc settled a patent infringement lawsuit with Amneal Pharmaceuticals over their Alzheimer's drug.

Allergan said its Forest Labs unit and Adamas had filed a lawsuit against privately owned Amneal, which was seeking regulatory approval for generic versions of Namzaric.

The drug, which has been licensed to Forest by Adamas, had U.S. sales of $12.8 million for the quarter ended June 30.

Under the settlement terms, Forest and Adamas will grant Amneal a license to market generic versions of Namzaric from January 1, 2025.

Other terms of the settlement were not disclosed.

Allergan and Adamas have also sued Amerigen Pharmaceuticals, which seeks to market generic versions of the drug.

(Reporting by Shailesh Kuber; Editing by Anil D'Silva)