GSK, XenoPort Unveil Gabapentin Enacarbil Phase II Trial Results

GlaxoSmithKline and XenoPort have reported top-line results from a phase II clinical trial evaluating GSK1838262/XP13512 (gabapentin enacarbil) in adult patients with neuropathic pain associated with post-herpetic neuralgia (PHN) who have had a history of inadequate response to gabapentin doses of 1800mg/day or higher.

In the double-blind, two-period cross-over study, 3600mg/day of GSK1838262 has demonstrated a significant improvement over 1200mg/day of GSK1838262 on the primary endpoint, which was the change from baseline to the end of the treatment period in the 24-hour average pain intensity score.

Reportedly, a greater reduction in the 24-hour average pain score was observed for the 3600mg/day dose than for the 1200mg/day dose.

The study enrolled 138 subjects diagnosed with PHN who had been experiencing pain for at least three months following healing of the herpes zoster skin rash. Subjects with a history of inadequate response to gabapentin entered a baseline period where they received a dose of 1800mg/day of gabapentin for two weeks.

However, the subjects who had a 24-hour average pain score of at least four on the 11-point pain intensity rating scale were then randomised to receive either 1200mg/day of GSK1838262 for the first 28-day treatment period followed by 3600mg/day for the second 28-day treatment period, or 3600mg/day followed by 1200mg/day. Subjects received 2400mg/day of GSK1838262 for four days in between the two treatment periods.

Atul Pande, senior vice president at GlaxoSmithKline Neurosciences Medicines Development Center, said: “These results from another positive study of GSK1838262 in the treatment of PHN will be important as we evaluate our next steps in the development program for neuropathic pain.”