XenoPort Announces Positive Phase IIa Results With XP13512

XenoPort has announced results from a Phase IIa clinical trial demonstrating that its most advanced product candidate, known as XP13512, provided statistically significant and clinically relevant benefits to patients with post-herpetic neuralgia (PHN) when administered twice a day. XP13512 is a transported prodrug of gabapentin, a drug that has been sold by Pfizer as Neurontin since 1993 and is currently sold as a generic drug by a number of companies.

The Phase IIa clinical trial was a randomized, double-blind, placebo-controlled, multicenter study to assess the safety, tolerability, pharmacokinetics and efficacy of XP13512 in patients with PHN. The study was conducted at 18 clinical sites in the U.S. and enrolled 101 adult PHN patients. After establishing baseline measures and prior to entering the randomized treatment period, all patients were titrated up to 1,800 mg/day (600 mg three times a day) of oral Neurontin and were maintained at this dose for seven days. At the end of this Neurontin treatment period, pharmacokinetics and clinical endpoints were assessed. Patients were then immediately randomized to oral XP13512 (1,200 mg twice daily) or placebo treatment. Treatment continued for an additional 14 days, at which time pharmacokinetics and clinical endpoints were again assessed.

The primary endpoint for the clinical trial was the change in average pain score between the seven days of baseline assessment to the final seven days of XP13512 or placebo treatment using an 11-point numerical pain scale. Compared to placebo, treatment with XP13512 was associated with a statistically significant reduction in pain as measured by this pain scale (p= 0.032). Statistically significant improvements in pain were also observed using the Short-Form McGill Pain Questionnaire. Additionally, XP13512 treatment was associated with a statistically significant reduction in sleep interference when compared to placebo.