Major Win For Glaxo with Xenoport for Restless Legs syndrome -- Next Blockbuster?

The most common treatments include dopamine agonists, Requip and Mirapex, both effective, but limited because of the development of augmentation (worsening of symptoms with time) and rare but worrisome side effects of compulsive behaviors and sudden attacks of hypersomnia.  As a consequence, there is a tendency for primary care to defer treatment to sleep specialists and neurologists.  As a consequence, most patients with RLS  remain untreated.

Gabapentin, marketed initially by Pfizer as Neurontin in 1993, with 2004 sales of $2.7 billion dollars, is now sold by multiple generic companies.  The  absorption of gabapentin is limited to a short portion of the intestine, and as such, patients require frequent dosing and have variable and limited absorption.  XP1512 is a transported prodrug of gabapentin, targeting high-capacity nutrient transporter mechanisms expressed throughout the length of the intestinges, which overcome many of Neurontin's shortcomings.

XP13512, when absorbed becomes gabapentin (Neurontin), a drug familiar and widely used by primary care physicians for diabetic peripheral neuropathy and other forms of neuropathic pain.  As such, I would anticipate minimal resistance from primary care to prescribe XP13512, a factor critical to have the drug widely utilized for this very common and disabling condition.  The combination of excellent tolerability and efficacy for both restless legs, shown in these trials, and for pain, shown in trials for Neurontin, should translate into rapid market entry for XP13512, and make XP13512 GlaxoSmithKline's next blockbuster drug.