Shire Pharmaceuticals says it has filed a second lawsuit against Impax Laboratories, which is trying to win clearance of a copycat version of the UK company’s top-selling ADHD treatment, Adderall XR (amphetamine salts extended-release).

Shire had already filed one lawsuit against Impax after the latter filed a 30mg dose version with the US Food and Drug Administration [[19/11/03b]], [[05/01/04d]]. The UK firm has stepped up its offensive because of Impax’ announcement last month that it was also seeking clearance of doses ranging from between 5mg and 25mg [[08/12/04e]]. It also has lawsuits pending against Barr Laboratories – the first company to announce its intent to win the green light for a generic copy of the million-a-year drug [[10/01/03b]], [[26/02/03d]], [[18/12/03a]] – but has decided not to sue Colony Pharmaceuticals, which filed a notice letter last month [[03/12/04d]].

The UK company has reiterated that Adderall XR is covered by two patents that are not set to expire until 2018 and notes that Barr cannot launch its drug before the expiration of the currently pending 30-month stays – triggered by the lawsuits – or a court ruling in its favor. Impax and Colony will have to wait until Barr’s first-to-file rights expire, which could include 180 days of generic market exclusivity.

The Barr court case is scheduled to go to trial in January 2006, while the Impax trial could be heard in October this year.