Spectrum Pharmaceuticals, Inc. has initiated challenge of the patent listed by GlaxoSmithKline in connection with GlaxoSmithKline's Imitrex injection 6mg/0.5mL.

The exclusivity afforded the patent listed in the Orange Book for Imitrex injection expires on February 6, 2009. Spectrum's Abbreviated New Application (ANDA) for sumatriptan succinate injection alleges that the Orange Book listed patent is invalid, unenforceable and/or would not be infringed by Spectrum's product.

Spectrum submitted its ANDA containing a Paragraph IV certification for a generic Imitrex injection product with the US FDA in October 2004, and received notification of acceptance with Paragraph IV certification in January 2005. Following receipt of the notice from the FDA, Spectrum notified GlaxoSmithKline, the patent owner. On February 18, 2005, GlaxoSmithKline filed suit in US federal court to prevent Spectrum from proceeding with the commercialization of its product. This action formally initiates the patent challenge process under the Hatch-Waxman Act, Spectrum said in a release.

Sumatriptan succinate injection is marketed by GlaxoSmithKline under the brand name Imitrex and is used for the acute treatment of migraine attacks with or without aura and the acute treatment of cluster headache episodes in adults.