GSK Moves to Stop Generic Valtrex Launch

While Indian firm Ranbaxy said this week its generic of GlaxoSmithKline’s Valtrex was OK’d for U.S. sales, the drug’s launch may have to wait.

GSK said Friday it would go to court to ask for a preliminary injunction barring the generic drug’s launch to the U.S. market, pending the outcome of GSK’s pending patent-infringement suit against Ranbaxy.

Filed in 2003, GSK’s lawsuit alleges that Ranbaxy’s generic product infringes the composition of matter patent for Valtrex, which expires in June 2009, unless GSK wins a patent extension by conducting pediatric studies of the drug.

A trial date for the infringement action has not been set, GSK said.

Under a prior agreement, if GSK applies for a preliminary injunction within 45 days of the FDA’s approval of Ranbaxy’s generic, Ranbaxy agreed not to launch its product until the court either rules on the injunction or decides the pending court case.

GSK said in a statement it remains confident in the strength of its intellectual property for Valtrex and the product’s exclusivity, afforded by the basic ‘composition of matter’ patent to June 2009.

GSK said a number of drug makers have applied for approval of generic versions of Valtrex but that only Ranbaxy has directly challenged the basic Valtrex patent.

Valtrex is approved for the treatment and suppression of genital herpes, herpes zoster — also called shingles — and cold sores.