TOKYO, JAPAN and SANTA CLARA, CA- March 2, 2009 - Astellas Pharma Inc. (Astellas) and XenoPort, Inc. (NASDAQ: XNPT) today announced preliminary top-line results from a Phase 2 clinical trial of ASP8825/XP13512 for the treatment of symptoms in moderate-to-severe primary restless legs syndrome (RLS) patients. The trial was conducted by Astellas in Japan. ASP8825/XP13512 demonstrated statistically significant improvements compared to placebo on the primary endpoint of the trial and was well tolerated.

This 12-week, double-blind, placebo-controlled Phase 2 clinical trial (Study 8825-CL-0003) enrolled 474 patients who were diagnosed with RLS. Patients were treated with 600, 900 or 1200 mg of ASP8825/XP13512 or placebo, given once per day after the evening meal. The primary endpoint for the clinical trial was the change from baseline for the International RLS (IRLS) rating scale score at end of treatment.

Treatment with 1200 mg of ASP8825/XP13512 was associated with a statistically significant improvement in the primary endpoint compared to placebo. Statistically significant improvements over placebo were also observed on some secondary endpoints, including the investigator-rated clinical global impression of improvement scale (CGI-I), which achieved statistical significance for each of the 600 mg, 900 mg and 1200 mg dosing cohorts. 

The most commonly reported adverse events for ASP8825/XP13512 were somnolence and dizziness, which were generally transient and mild to moderate in severity. There were no treatment-emergent serious adverse events during the study period in ASP8825/XP13512-treated subjects.

“We believe that there is a substantial unmet medical need for a medicine to treat RLS patients and are very pleased with the quality and consistency of data in this Phase 2 trial showing statistically significant improvements,” said Masafumi Nogimori, president and chief executive officer of Astellas. “We look forward to meeting with the regulatory agency to discuss the development path for ASP8825/XP13512 and continuing our great partnership with XenoPort.”  

“We are pleased by the outcome of this trial, which is consistent with the results of XenoPort’s trials of ASP8825/XP13512 conducted in RLS patients in the U.S.,” said Ronald W. Barrett, Ph.D., chief executive officer of XenoPort. “We look forward to working with Astellas to advance the development of ASP8825/XP13512 within the Astellas territory and moving closer to achieving our objective of making a new therapy available to RLS sufferers throughout the world.”

Astellas/XenoPort Collaboration Arrangement
In 2005, Astellas obtained exclusive rights to develop and commercialize ASP8825/XP13512 in Japan, Korea, the Philippines, Indonesia, Thailand and Taiwan. XenoPort has received payments of $40 million to date under the collaboration agreement. In addition, XenoPort is eligible to receive clinical and regulatory milestone payments totaling up to $45 million. XenoPort is also eligible to receive royalties on any sales of ASP8825/XP13512 in the Astellas territory at a royalty rate in the mid-teens on a percentage basis.

About Astellas
Astellas Pharma Inc., located in Tokyo, Japan, is a pharmaceutical company dedicated to improving the health of people around the world through the provision of innovative and reliable pharmaceutical products. The organization is committed to becoming a global pharmaceutical company by combining outstanding R&D and marketing capabilities and continuing to grow in the world pharmaceutical market. For more information about Astellas Pharma Inc., please visit our website at

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 is developing its lead product candidate in collaboration with Astellas and GlaxoSmithKline, or GSK. GSK has filed with the U.S. Food and Drug Administration a new drug application for XP13512 (known as Solzira in the U.S. and ASP8825 in the Astellas territory) for the treatment of RLS. XenoPort’s product candidates are also being studied for the potential treatment of gastroesophageal reflux disease, migraine headaches, neuropathic pain, spasticity related to spinal cord injury, acute back spasms and Parkinson’s disease. To learn more about XenoPort, please visit the Web site at

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