The UK’s Shire has filed a lawsuit in the USA against generic drugmaker Colony Pharmaceuticals, as well as Actavis, over alleged infringement of patents protecting its best-selling attention deficit and hyperactivity disorder Adderall XR.

Shire said it is taking legal action in the US District Court of Maryland in response to an Abbreviated New Drug Application filed by Colony in November 2004 for generic versions of various doses of Adderall XR (mixed amphetamine salts), and the UK firm says that all of them infringe the three patents in suit. It is not the first time that Shire has headed to the courts over Adderall XR and it has previously sued Barr Laboratories, Impax Laboratories, Teva and Andrx Pharmaceuticals.

However the firm cut a deal with Barr last summer preventing the latter from launching its copycat version until 2009, or until another firm launches a generic form of Adderall XR. In return, Shire took out a licence for a vaginal drug delivery technology developed by Barr's Duramed subsidiary, as well as a licence for Duramed's oral contraceptive Seasonique (levonorgestrel/ethinyl estradiol). A settlement was also reached with Impax, in a deal which allows the latter to market its version of Adderall XR 181 days after any launch by Barr, which holds first-to-file status in the USA.

Shire’s determination to defend the drug is hardly surprising given that Adderall XR sales in 2006 advanced 18% to $864 million, almost half the firm’s total revenues. However it will now be looking to switch patients to its follow-up ADHD product Vyvanse (lisdexamfetamine dimesylate), which has just been approved by the US Food and Drug Administration, before the Adderall patents run out the year after next.