Source: DGNews  |  Posted 3 years ago

By Emma Hitt, PhD

HONOLULU -- February 2, 2009 -- An experimental treatment for restless legs syndrome (RLS), XP13512, was found to improve symptoms in all patients and reduced pain associated with RLS compared with placebo, according to results of a study presented here at the American Academy of Pain Medicine (AAPM) 25th Annual Meeting.

"Pain is not a criterion for diagnosis of RLS, but many patients report pain with RLS, and about 1 in 5 say it is their most troublesome symptom," said lead author Ron Barrett, PhD, XenoPort, Inc., Santa Clara, California, in a presentation on January 30.

XP13512 is a novel transported prodrug of gabapentin in development for the treatment of RLS, postherpetic neuralgia, painful diabetic neuropathy, and migraine prophylaxis. The current study included 222 patients with moderate to severe RLS, who were randomised to receive once-daily XP13512 at a dose of 1,200 mg, or placebo, taken with food.

Treatment response was defined as a response of "much improved" or "very much improved" according to the Clinical Global Impression-Improvement (CGI-I) scale.

Results showed that XP13512 improved significantly the mean International Restless Legs Scale (IRLS) total score compared with placebo at week 12 (P = .0003) and significantly more patients were responders according to the CGI-I scale (76.1% vs 38.9%; P < .0001).

In addition, among patients with a baseline pain score of 4 or greater, more patients treated with XP13512 reported at least a 50% pain reduction versus placebo (75% vs 33%; P < .0001), indicating that the magnitude of the treatment effect is greater among patients with more severe pain at baseline.

The most common treatment-related adverse events included somnolence (26% vs 8%) and dizziness (21% vs 5%) for XP13512 vs placebo, respectively. No clinically significant changes in vital signs, electrocardiogram, or laboratory parameters were observed.

"These findings suggest that XP13512 is effective in this setting and that if approved, it will represent another useful treatment option for patients with RLS," Dr. Barrett said.

Funding for the study was provided by XenoPort, Inc.

[Presentation title: XP13512/GSK1838262 Treats the Pain Associated With Restless Legs Syndrome. Abstract 210]