Shire Pharmaceuticals has said it will not sue Teva Pharmaceutical after the latter filed for regulatory approval of a generic version of Adderall XR (amphetamine salts extended release), Shire’s once-daily treatment for attention-deficit hyperactivity disorder, in the USA [[23/02/05b]].

Adderall remains Shire’s top-selling product and has patent protection out to 2018, so at first glance the company’s decision not to sue Teva seems surprising. But the UK company believes that the launch of any generic hinges on ongoing legal disputes with two other generics companies, Barr Laboratories and IMPAX Laboratories, and additional lawsuits will not help protect its product. Shire took a similar stance after Colony Pharmaceuticals filed for its own version late last year [[03/12/04d]].

Barr was the first company to file for approval of generic Adderall XR [[10/01/03b]], so would be entitled to 180 days’ marketing exclusivity under current US law. “Impax, Colony or Teva will not be able to lawfully launch a generic version of Adderall XR without the necessary final approval from the FDA and the expiration of the ‘first to file’s’ exclusivity rights,” said Shire in a statement. The Impax lawsuit is scheduled to come to trial in October this year, with Barr’s case set for January 2006.

Aside from the threat of generic competition, Adderall XR’s sales could also be impacted by the decision by Canada’s regulatory authorities earlier this year to suspend sales of the product over concerns it had been linked to cases of sudden death [[10/02/05a]].

Last year, Adderall XR brought in $607 million dollars to Shire’s coffers, a rise of 28% over the prior year, and won a quarter share of the US market for ADHD treatments. But the uncertainties surrounding the product have led the UK firm to forecast flat sales in 2005 [[03/03/05d]].