GlaxoSmithKline and XenoPort Announce Extension of GSK1838262 (XP13512) FDA Review Date to February 9, 2010

GlaxoSmithKline (NYSE: GSK) and XenoPort, Inc. (Nasdaq: XNPT) today announced that the U.S. Food and Drug Administration (FDA) has extended the original Prescription Drug User Fee Act (PDUFA) goal date for its review of the New Drug Application (NDA) for GSK1838262/XP13512 (gabapentin enacarbil) to February 9, 2010. The original PDUFA date for this NDA review was November 9, 2009.

The FDA determined that a Risk Evaluation and Mitigation Strategy (REMS) was necessary for GSK1838262. In response to FDA's request, GSK submitted a proposed REMS. The FDA accepted this submission as a solicited major amendment to the GSK1838262 NDA. The FDA has the option to extend the PDUFA goal date when a sponsor submits a major amendment that provides a substantial amount of new data not previously reviewed by the FDA.

GlaxoSmithKline -- one of the world's leading research-based pharmaceutical and healthcare companies -- is committed to improving the quality of human life by enabling people to do more, feel better and live longer. For further information please visit www.gsk.com.

XenoPort 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 partnership with Astellas Pharma Inc. and GSK. XenoPort's product candidates are being studied for the potential treatment of restless legs syndrome, gastroesophageal reflux disease, migraine headaches, neuropathic pain, spasticity related to spinal cord injury and Parkinson's disease. To learn more about XenoPort, please visit the Web site at www.XenoPort.com.

GlaxoSmithKline cautionary statement regarding forward-looking statements

Under the safe harbor provisions of the U.S. Private Securities Litigation Reform Act of 1995, GSK cautions investors that any forward-looking statements or projections made by GSK, including those made in this announcement, are subject to risks and uncertainties that may cause actual results to differ materially from those projected. Factors that may affect GSK' s operations are described under 'Risk Factors' in the 'Business Review' in the company' s Annual Report on Form 20-F for 2008.

XenoPort Forward-Looking Statement

This press release contains "forward-looking" statements, including, without limitation, all statements related to the PDUFA goal date extension. 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 "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, the uncertainty of the FDA approval process and other regulatory requirements; XenoPort' s dependence on its current and additional collaborative partners; and the therapeutic and commercial value of the company' s compounds. These and other risk factors are discussed under the heading "Risk Factors " in XenoPort' s Quarterly 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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SOURCE: XenoPort, Inc.

GlaxoSmithKline Enquiries: 
UK Media enquiries: 
Philip Thomson, (020) 8047 5502 
Claire Brough, (020) 8047 5502 
Alexandra Harrison, (020) 8047 5502 
or 
US Media enquiries: 
Kevin Colgan, 919-483-2839 
Holly Russell, 919-483-2839 
Mary Anne Rhyne, 919-483-2839 
Sarah Alspach, 215-751-7709 
or 
European Analyst/Investor enquiries: 
David Mawdsley, (020) 8047 5564 
Sally Ferguson, (020) 8047 5543 
Gary Davies, (020) 8047 5503 
or 
US Analyst/Investor enquiries: 
Tom Curry, 215-751-5419 
Jen Baxter, 215-751-7002 
or 
XenoPort Enquiries: 
XenoPort Analyst/Investor and Media enquiries: 
Jackie Cossmon, 408-616-7220

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