Shire has finally bagged approval in the US for its long-acting attention deficit hyperactivity disorder drug (ADHD) Mydayis.

The drug, which was first submitted in the country back in 2006, has the same active ingredient as the firm's Adderall XR (mixed amphetamine salts), but is designed to provide symptom control for adults with ADHD for up to 16 hours as opposed to the 12 to 14 hours currently offered by alternative treatments.

The submission includes data from 16 clinical studies evaluating the drug (previously SHP465) in more than 1,600 subjects, including results of a short-term efficacy and safety study in paediatric patients with ADHD (aged six-17) requested by the US Food and Drug Administration.

In pivotal, placebo-controlled clinical studies, Mydayis significantly improved symptoms of ADHD, as measured by the ADHD-RS-IV and the Permanent Product Measure of Performance (PERMP), in adults and adolescents, the firm noted.

ADHD is a neuro-developmental disorder that manifests as a persistent pattern of inattention and/or hyperactivity-impulsivity. An estimated 4.4 percent of adults have the condition in the US.

While Mydayis is restricted for use in patients aged 12 years and over, it is expected to most benefit adult and some younger patients currently taking two doses of various treatments to achieve symptom control throughout the day, note analysts at Deutsche Bank.

Shire said it expects to make Mydayis commercially available in the US in the third quarter of 2017, and previously indicated that the drug could hit peak sales of $500 million.