GlaxoSmithKline and partner XenoPort are celebrating positive Phase IIb results for gabapentin enacarbil for neuropathic pain associated with post-herpetic neuralgia.

In the 376-patient study, people with PHN who had experienced pain for at least three months following healing of the herpes zoster (shingles) skin rash were randomised to receive one of three twice-daily doses of the compound, known as GSK1838262/XP13512 or placebo for 14 weeks. All three doses of gabapentin enacarbil (1,200, 2,400 or 3,600 mg/day) demonstrated statistically significant improvements over placebo on the primary endpoint, ie the change on a pain-intensity score from baseline to the end of maintenance treatment.

GSK's senior vice president of neurosciences, Atul Pande, said the companies “are currently evaluating the next steps” for development of the drug in neuropathic pain. The compound, which utilises high-capacity transport mechanisms in the gastrointestinal tract to improve absorption, has already been filed with the US Food and Drug Administration for restless legs syndrome with the proposed brandname Solzira.

News of the data provided a major boost to XenoPort’s share price which rose 25.6% to $24.75.