Days after announcing plans to sue Teva Pharmaceutical Industries over patent infringement of Intuniv, Shire has been informed that another company is hoping to launch its generic version of the attention-deficit hyperactivity disorder drug.

The company has received a Paragraph IV notice letter from Anchen Pharmaceuticals which has filed an Abbreviated New Drug Application for a number of generic version of Intuniv (guanfacine) extended-release tablets. The drug was only launched by Shire in the USA, where it is approved for the treatment of ADHD in children and adolescents aged six to 17, at the end of 2009.

Anchen’s submission comes after two earlier ANDAs containing a Paragraph IV certification issued by Teva (in March) and in early April 2010 by Actavis. A few days ago, Shire filed a lawsuit against the Israeli generics giant concerning two patents and the company says that three patents on Intuniv are valid and expire in 2015, 2020 and 2022, respectively.

Shire also noted that the Hatch-Waxman exclusivity period for Intuniv runs until September 2, 2012, therefore any ANDAs for generic versions cannot be approved by the US Food and Drug Admininstration until then.