XenoPort, Inc. has announced results from a phase 2a clinical trial demonstrating that its most advanced product candidate, known as XP13512, provided statistically significant and clinically relevant benefits to patients with Restless Legs Syndrome (RLS).

The phase 2a clinical trial was a randomized, double-blind, placebo-controlled, cross-over, multi-centre study of XP13512 taken twice daily. Patients were randomized to receive either XP13512 or placebo for two weeks. After a one-week washout period, the patients were switched to the alternate treatment for another two weeks. Objective polysomnographic assessments were conducted at baseline and at the end of each treatment period. Four patients did not complete the clinical trial due to reasons that were not treatment-related.

Compared to placebo, treatment with XP13512 was associated with a highly statistically significant improvement (p<0.0001) in the International Restless Legs Scale (IRLS) score at the end of 14 days of treatment, the primary endpoint of the clinical trial. Compared to placebo, XP13512 was associated with statistically significant improvements in a number of objective sleep measures, including an increase in total sleep time (TST), an increase in the amount of slow-wave sleep (deep sleep), a reduction in the amount of time awake after sleep onset (WASO) and a reduction in the number of times periodic limb movements woke patients from sleep (PLMSA). XP13512 was well tolerated. The most common side effects of XP13512 were dizziness and somnolence, according to the company release.

" RLS symptoms, particularly disturbance of sleep, can have a significant negative impact on patient quality of life," Clete A. Kushida, associate professor and director of the Stanford University Centre for Human Sleep Research and an investigator on the XP13512 RLS clinical trial said adding, "This initial investigation of XP13512 in patients with RLS is very encouraging, both in terms of the magnitude of clinical improvement and the favourable tolerability of XP3512."


Ronald W. Barrett, XenoPort's chief executive officer added, "This study's demonstration that XP13512 can improve both symptoms and sleep quality in patients with RLS suggests that XP13512's combination of mechanism of action and ability to maintain effective drug levels throughout the night may provide an effective treatment for RLS."

Restless legs syndrome is a common, under-diagnosed neurological disorder that frequently manifests itself as a sleep disorder. Patients who suffer from RLS experience an irresistible urge to move their legs. This urge is usually accompanied by unpleasant sensations of burning, creeping, tugging or tingling inside the patients' legs, ranging in severity from uncomfortable to painful. Left untreated, RLS may cause exhaustion, daytime fatigue, inability to concentrate and impaired memory.

XP13512 is a Transported Prodrug of gabapentin, a drug that has been sold by Pfizer Inc as Neurontin since 1993 and is currently sold as a generic drug by a number of companies.

XenoPort, Inc., based in Santa Clara, California, is a privately held biopharmaceutical company focused on developing a portfolio of internally discovered product candidates that utilize the body's natural nutrient transporter mechanisms to improve existing drugs.