* FDA issues complete response letter for Intuniv
* Delay due to labeling discussions over ADHD drug
* Shire still sees launch in Q4 as planned
(Adds details, background)
LONDON, July 28 (Reuters) - U.S. regulators have delayed approval of Shire's (SHP.L) new extended-release hyperactivity drug Intuniv but the British company still expects it to be launched in the United States before the end of the year.
Shire said on Tuesday the Food and Drug Administration had issued a so-called complete response letter following lengthy labeling discussions that caused the agency to miss its original target date of deciding on the medicine by July.
If approved, Intuniv will be the first selective alpha-2A receptor agonist for the treatment of attention deficit hyperactivity disorder (ADHD). It is designed to be given to children and adolescents aged 6 to 17 years.
Shire said the FDA had not identified safety concerns over the drug or requested new clinical studies.
"Shire is confident that we will quickly come to agreement on the final product label and anticipates a launch in the fourth quarter as planned," said Mike Cola, President of Shire Specialty Pharmaceuticals.
Intuniv, along with another already launched new ADHD drug drug called Vyvanse, represents the future of Shire's hyperactivity business as its former blockbuster Adderall XR faces generic competition.
The company, which is Britain's third largest drugmaker, is also pinning its hopes on a new human genetic therapies division that makes medicines to treat a range of rare diseases.
(Reporting by Ben Hirschler; editing by John Stonestreet)