Astellas and XenoPort Announce Submission of a New Drug Application in Japan Requesting PMDA Approval of ASP8825/XP13512 for Restless Legs Syndrome

Astellas Pharma Inc. and XenoPort, Inc. (NASDAQ:XNPT) today announced that a new drug application (NDA) has been filed with the Pharmaceuticals and Medical Device Agency (PMDA) in Japan for ASP8825 (gabapentin enacarbil), also known as XP13512, as a potential treatment for restless legs syndrome (RLS). The data supporting safety and efficacy in the NDA filing comes from the successful Phase 2 study in RLS patients and long-term safety study conducted by Astellas in Japan and the RLS clinical program conducted by XenoPort in the United States. The acceptance of filing of the NDA triggers a $5 million milestone payment from Astellas to XenoPort.

"We are pleased to submit the NDA for ASP8825 in Japan,” said Masafumi Nogimori, Astellas’ president and chief executive officer. "We look forward to delivering this new treatment to patients suffering from RLS in Japan.”

"Astellas has made great progress in advancing its RLS development program,” said Ronald W. Barrett, Ph.D., XenoPort’s chief executive officer. "If approved, ASP8825 could be an important new treatment for patients with RLS in Japan.”

About ASP8825

Discovered by XenoPort, ASP8825 is a new chemical entity that utilizes naturally-occurring, high-capacity nutrient transporters in the gastrointestinal tract to generate active, efficient absorption into the body. Once absorbed, ASP8825 is rapidly converted into gabapentin, a compound thought to work by binding to certain calcium channels in the central nervous system. As compared to oral gabapentin, ASP8825 provides dose-proportional and extended exposure of gabapentin.

About RLS

RLS is a neurological condition that is characterized by unpleasant and sometimes painful sensations in the legs that result in a compelling urge to move and can result in distressing symptoms that disrupt sleep and significantly impact daily activities. These RLS-related symptoms typically begin or worsen during periods of rest or inactivity, particularly when lying down or sitting, and may be temporarily relieved by movement.

Astellas/XenoPort Collaboration Arrangement

In 2005, Astellas obtained exclusive rights to develop and commercialize ASP8825 in Japan, Korea, the Philippines, Indonesia, Thailand and Taiwan. XenoPort has received payments of $43 million to date under the collaboration agreement. In addition, XenoPort is eligible to receive clinical and regulatory milestone payments totaling up to $42 million. XenoPort is also eligible to receive royalties on any sales of ASP8825 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 category leader by rapidly establishing a business model in urology, immunology & infectious diseases, neuroscience, DM complications & metabolic diseases and oncology. For more information on Astellas Pharma Inc., please visit our website at http://www.astellas.com/en.

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, XP13512, in collaboration with Astellas and GlaxoSmithKline (GSK). The U.S. Food and Drug Administration is currently reviewing GSK’s NDA for XP13512 as a potential treatment for moderate-to-severe primary RLS in the United States. XenoPort’s product candidates are also being studied for the potential treatment of gastroesophageal reflux disease, migraine headaches, neuropathic pain, spasticity and Parkinson’s disease. To learn more about XenoPort, please visit the Web site at www.XenoPort.com.

Forward-Looking Statements

This press release contains "forward-looking” statements, including, without limitation, all statements related to XenoPort’s and its partners’ future clinical development and commercialization of XP13512 and the timing thereof; the therapeutic and commercial potential of XP13512; the suitability of XP13512 as a treatment for RLS; U.S. and Japanese regulatory processes and the timing thereof; and potential milestone payments and royalties and the timing thereof. Any statements contained in this press release that are not statements of historical fact may be deemed to be forward-looking statements. Words such as "could,” "may,” "potential” and similar expressions are intended to identify forward-looking statements. These forward-looking statements are based upon XenoPort's current expectations. Forward-looking statements involve risks and uncertainties. XenoPort's actual results and the timing of events could differ materially from those anticipated in such forward-looking statements as a result of these risks and uncertainties, which include, without limitation, risks related to the uncertainty of regulatory approval processes and regulatory requirements; XenoPort’s dependence on its current and additional collaborative partners; and the uncertain therapeutic and commercial value of XenoPort’s compounds. These and other risk factors are discussed under the heading "Risk Factors” in XenoPort’s Annual Report on Form 10-Q filed with the Securities and Exchange Commission on November 4, 2009. XenoPort expressly disclaims any obligation or undertaking to release publicly any updates or revisions to any forward-looking statements contained herein to reflect any change in the company's expectations with regard thereto or any change in events, conditions or circumstances on which any such statements are based.

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XenoPort is a registered trademark of XenoPort, Inc.