Shire has filed a lawsuit in the USA against Teva Pharmaceutical Industries for alleged infringement of two of its US patents on attention deficit hyperactivity disorder (ADHD) drug Adderall XR.

In a statement, the UK drugmaker said the lawsuit was sparked by Teva’s filing of Abbreviated New Drug Applications for two generic versions of Adderall XR. The lawsuit alleges that all of Teva's generic strengths infringe the patents in suit.

The suit was filed by Shire’s subsidiary, Shire Laboratories, in the US District Court for Eastern Pennsylvania.

Shire has been busily defending Adderall XR from cut price generic competition as it tries to reduce its reliance on the product, its top seller, through the launch of new products.

The UK company has already negotiated a settlement with Impax Laboratories that prevents the generics company from launching a copycat version until 2010, and it is also suing Barr Laboratories, another generics firm which would have six months’ marketing exclusivity for its version on approval under the first-to-file legislation in the USA.

Adderall XR brought in $730 million out of total sales of $1.6 billion at Shire last year. Shire is developing NRP104, a patch-based drug for ADHD that could reach the market next year and has been tipped to make sales in excess of $1 billion.