NEWS

WIRES

OTHER

Regulatory Update: GSK and XenoPort Submit Supplemental New Drug Application to FDA for Horizant in Postherpetic Neuralgia

Notes to Editors

Horizant is not approved or licensed anywhere in the world for PHN. For information about the current licensed indication for Horizant, which is in the United States only, please visit http://www.gsk.com/products/prescription-medicines/horizant.htm for full Prescribing Information and Medication Guide.

About GlaxoSmithKline

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

About XenoPort

XenoPort is a biopharmaceutical company focused on developing a portfolio of internally discovered product candidates that utilize the body's nutrient transport mechanisms to improve the therapeutic benefits of existing drugs. Horizant is XenoPort's first approved product. GlaxoSmithKline holds commercialization rights and certain development rights for gabapentin enacarbil in the United States. Gabapentin enacarbil is also being developed in partnership with Astellas Pharma Inc. for the potential treatment of Restless Legs Syndrome in Japan. XenoPort holds all other world-wide rights and has co-promotion and certain development rights to gabapentin enacarbil in the United States. XenoPort's pipeline of product candidates includes potential treatments for patients with neuropathic pain, spasticity and Parkinson's disease. To learn more about XenoPort, please visit the Web site at www.XenoPort.com.

GlaxoSmithKline Forward-Looking Statement

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 2010.

XenoPort is a registered trademark of XenoPort, Inc.

Horizant is a U.S. trademark of GSK.

GlaxoSmithKline Enquiries:
UK Media enquiries:
David Mawdsley, (020) 8047 5502
Stephen Rea, (020) 8047 5502
Sarah Spencer, (020) 8047 5502
Janet Morgan, (020) 8047 5502
David Daley, (020) 8047 5502
or
US Media enquiries:
Nancy Pekarek, 919-483-2839
Mary Anne Rhyne, 919-483-2839
Kevin Colgan, 919-483-2839
Sarah Alspach, 919-483-2839
or
European Analyst/Investor enquiries:
Sally Ferguson, (020) 8047 5543
Gary Davies, (020) 8047 5503
Ziba Shamsi, (020) 8047 3289
or
US Analyst/ Investor enquiries:
Tom Curry, 215-751-5419
Jeff McLaughlin, 215-751-7002
or
XenoPort Enquiries:
Analyst/Investor and Media enquiries:
Jackie Cossmon, 408-616-7220