Shire faces a delay in getting its new attention-deficit hyperactivity disorder drug Intuniv approved in the USA but the company is still confident of launching the treatment across the pond before the end of 2009.

The US Food and Drug Administration had issued a complete response letter for Intuniv (guanfacine) following labelling discussions between Shire and the agency. These talks “did not result in agreement in time to meet the Prescription Drug User Fee Act date" set for this month, the company said.

However Shire stressed that the FDA “did not identify safety concerns” regarding Intuniv in the letter, nor did it request new clinical studies. The firm added that it will work with the agency “to resolve the remaining labeling language over the next four to eight weeks”.

Mike Cola, president of Shire Specialty Pharmaceuticals, said that the company is confident that “we will quickly come to agreement on the final product label and anticipates a launch in the fourth quarter as planned”. If given the green light as a drug for children and adolescents aged six to 17, Intuniv, which is not a controlled substance and does not have a known mechanism for potential abuse or dependence, will be the first selective alpha-2A receptor agonist for the treatment of ADHD.

Guanfacine, then known as Connexyn, was filed with the FDA in August 2006 and the agency issued an approvable letter on the drug in June 2007.

Intuniv would join Vyvanse (lisdexamfetamine dimesylate) at the head of Shire’s ADHD franchise in the USA, and the firm will be hoping that it can help soften the blow of declining sales of its blockbuster Adderall XR (mixed amphetamine salts) which is now facing generic competition. Analysts at Collins Stewart are not overly concerned by the FDA letter and are not changing their current forecast of $211 million peak sales for Intuniv prior to patent expiry in 2015.