Shire files suit against Impax and Watson over Intuniv patent

Ireland-headquartered specialty pharma firm Shire plc (LSE: SHP) has filed a lawsuit in the US District Court for the Northern District of California against Impax Laboratories (Nasdaq: IPXL) and Watson Pharmaceuticals (NYSE: WPI) for the infringement of US Patent numbers. 5,854,290, 6,287,599 and 6,811,794, covering the firm’s attention-deficit hyperactivity disorder (ADHD) drug Intuniv (guanfacine HCl) extended release tablets.

The law suit results from Abbreviated New Drug Applications filed by Impax and Watson for generic versions of 4mgI guanfacine, which seek to market such generic products before the expiration of the '290, '599, and '794 patents. The regulatory exclusivity period for Intuniv runs through September 2, 2012, says Shire. US sales of the drug for the 12 months to September 30, 2010, were $14 million, according to data from Wolters Kluwer.

Shire had previously reported in March 2010 receipt of a Paragraph IV Letter from Teva Pharmaceuticals USA and, in April, of a Paragraph IV Letters from Actavis and Anchen Pharmaceuticals, both  regarding ANDAs for generic versions of Shire’s 1mg, 2mg, 3mg, and 4mg guanfacine extended release tablets.