Shire has come to an agreement with drugmakers Actavis and Watson that lays to rest all pending litigation over their attempts to launch a generic form of the attention-deficit hyperactivity drug (ADHD) Intuniv (guanfacine hydrochloride) in the US.

Under the settlement, Shire has granted Actavis a license to make and market its version of Intuniv in the US from December 1 next year, in return for a 25% royalty on gross profit during the 180 day period of exclusivity.

Watson has been given a license to market its own copycat version of the drug the day after Actavis' exclusivity period ends, although its products have yet to receive final approval from the US Food and Drug Administration.

Shire took Actavis to court after it won the US green light for a generic form of the pill, arguing that Intuniv's patents were still valid and enforceable. 

Indeed, under the settlement, both Actavis and Watson have admitted that their products infringe key patents on Shire's drug, for which it booked sales of nearly $288 million last year.

The agreements will be submitted to the US Justice Department and Federal Trade Commission for review.