XenoPort, Inc. (Nasdaq: XNPT) today announced top-line results from a Phase 3 clinical trial of XP13512 for the treatment of symptoms of primary restless legs syndrome (RLS). XP13512 demonstrated statistically significant improvements compared to placebo on both of the co-primary endpoints of the trial and was well tolerated."These results are very encouraging and represent a major advance for XenoPort, its partners and, potentially, RLS patients," said Ronald W. Barrett, Ph.D., chief executive officer of XenoPort.
This XenoPort study was a 12-week, double-blind, placebo-controlled Phase 3 clinical trial that enrolled 222 patients who were diagnosed with moderate-to-severe primary RLS. Patients were treated with either 1200 mg of XP13512 or placebo, given once per day. The co-primary endpoints for the clinical trial were the change from baseline for the International RLS (IRLS) rating scale score at end of treatment and the percentage of patients showing significant improvement on the Clinical Global Impression of Improvement (CGI-I) scale at end of treatment.
Treatment with 1200 mg of XP13512 was associated with a statistically significant improvement in the co-primary endpoints compared to placebo. Improvements in the IRLS Scale were significantly greater for XP13512 than for placebo (-13.2 vs. -8.8: p=0.0002). At the end of treatment, significantly more patients treated with XP13512 were reported as "much improved" or "very much improved" on the CGI-I scale compared to those treated with placebo (76% vs. 39%: p less than 0.0001).
During treatment over the 12-week period, the most commonly reported adverse events for XP13512 versus placebo were somnolence (26.5% XP13512; 7.4% placebo) and dizziness (19.5% XP13512; 4.6% placebo). There were no reported serious adverse events in XP13512-treated patients.
Dr. Barrett stated, "XP13512 works by a different mechanism than currently approved RLS drugs, and therefore may offer an alternative treatment option for patients whose lives are disrupted by RLS symptoms. In addition to the robust efficacy results in this clinical trial, we are happy to see that XP13512 continues to be well tolerated as we expand the number of RLS patients who have been treated with XP13512. We intend to present further data from this clinical trial at a future medical conference."
About XP13512
XP13512 is a patented, new chemical entity that is designed to improve upon the clinical utility of gabapentin by taking advantage of high-capacity transport mechanisms in the gastrointestinal tract to improve absorption.
About RLS
According to the National Institutes of Health, up to 12 million people in the U.S. are afflicted with RLS. The syndrome is characterized by disturbing, unpleasant and sometimes painful sensations in the legs that result in a compelling urge to move. The discomfort is often temporarily relieved by movement. Because symptoms typically occur at night, RLS patients often suffer from sleep disruption. RLS symptoms can be debilitating - published data suggest that RLS can have an impact on quality of life equivalent to, or worse than, major chronic medical disorders such as diabetes and osteoarthritis.
Additional XP13512 Phase 3 Clinical Trials in RLS
XenoPort is conducting two additional Phase 3 clinical trials, including a second 12-week, double-blind, placebo-controlled Phase 3 clinical trial with the same co-primary and similar secondary endpoints as the trial for which results were announced today. In addition to 1200 mg of XP13512, this trial is also evaluating 600 mg of XP13512. The trial is expected to enroll approximately 300 RLS patients.
XenoPort is also conducting a Phase 3 clinical trial assessing the long-term efficacy of XP13512 using a placebo-controlled, "randomized withdrawal" design to evaluate relapse of RLS symptoms in XP13512-treated or placebo-treated patients who had previously achieved clinical improvement while taking 1200 mg of XP13512 for 24 weeks.
About XP13512 Collaborations
In December 2005, XenoPort licensed to Astellas Pharma Inc. rights to develop and commercialize XP13512 in Japan, Korea, the Philippines, Indonesia, Thailand and Taiwan. In February 2007, XenoPort entered into a collaboration with GlaxoSmithKline (GSK) for the development and commercialization of XP13512 in all countries of the world, excluding the Astellas territory.
XenoPort has received up-front and milestone payments totaling $110 million from these collaborations. It is eligible to receive additional potential milestone payments of up to $615 million, including a $5 million milestone payment from Astellas for the completion of the Phase 3 clinical trial for which results were announced today.
Results of XP13512 in Restless Legs Syndrome
XenoPort is entitled to receive royalties on any product sales under both collaborations and has an option to share profits and co-promote XP13512 with GSK in the United States. The GSK agreement provides that XenoPort will complete its Phase 3 clinical development program of XP13512 for the treatment of RLS and that GSK will file the NDA in the U.S. for this indication. GSK is responsible for all other clinical development and commercialization of XP13512, outside the Astellas territory.
About XenoPort
XenoPort, Inc. is a biopharmaceutical company focused on developing a portfolio of internally discovered product candidates that utilize the body's natural nutrient transport mechanisms to improve the therapeutic benefits of existing drugs. XenoPort's most advanced product candidate, XP13512, is the subject of a Phase 3 clinical program for the treatment of RLS, and has successfully completed a Phase 2a clinical trial for the management of post-herpetic neuralgia. XenoPort has also reported positive results from a Phase 2a clinical trial of its second product candidate, XP19986, in patients with gastroesophageal reflux disease.
To learn more about XenoPort, please visit the web site at www.XenoPort.com
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