Shire Pharmaceuticals has received conditional approval from US regulators for SPD465, yet another compound from its stable of attention deficit hyperactivity disorder drugs.

The UK firm has received an approvable letter from the US Food and Drug Administration for SPD465, which has the same active ingredient as Shire’s best-seller Adderall XR (mixed amphetamine salts) but is designed to provide ADHD symptom control for adults for up to 16 hours, as opposed to Adderall’s 12. When asked about the contents of the FDA’s letter by PharmaTimes World News, a Shire spokeswoman said that the firm was still evaluating its options as it was only informed of the agency’s decision late on Friday and so it is too early to say if the company needs to take any particular action.

If SPD465 does get approved, it will be a welcome boost to Shire’s ADHD portfolio but getting the drug to market is not a priority at the moment and the delay caused by the FDA’s letter is not a concern for investors who were told last month by Shire that a launch this year was unlikely. The company is devoting its energies to getting Vyvanse (lisdexamfetamine dimesylate) to market.

The ADHD drug, which is intended to be a safer, more abuse-resistant and more effective alternative to currently-marketed opioids, was approved by the FDA in February and a launch is expected before the end of the second quarter in three once-daily dosage strengths of 30mg, 50mg and 70mg for children aged six to 12. Earlier this year, chief executive Matthew Emmens said that Vyvanse, the follow-up treatment to Adderall XR (which becomes genericised in 2009) is now "our top promotional priority within our ADHD portfolio”.

Apart from the aforementioned compounds, Shire also markets the ADHD patch product Daytrana (methylphenidate), which was launched in the USA last June and contributed $11.9 million to first-quarter sales.