Shire has refiled its experimental attention deficit hyperactivity disorder drug SHP 465 in the US, having garnered new data further backing its safety and efficacy.

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 its predecessor's 12.

The filing includes data from 16 clinical studies evaluating 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.

Also included findings from the 306 study, which involved 275 adults with ADHD aged 18-55 years and showed that primary endpoints were met for both doses of SHP465 being tested (12.5mg and 37.5mg, administered once daily), indicating superiority over placebo symptom improvement. Significant improvement in those treated with the drug over placebo was also observed in patients' global functioning.

"Since our first submission, our understanding of ADHD and adult patients' needs has evolved, and we believe the additional studies in our filing fulfill the request from the FDA," noted Philip Vickers, Shire's global head of R&D. "With the potential of once-daily dosing, SHP465, if approved, could help patients address the ongoing challenges of ADHD symptoms."

The company is seeking approval for the drug as a once-daily treatment for the condition; the US Food and Food and Drug Administration is expected to provide a decision on or around June 20.

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 ADHD in the US.