Issued – Friday 6 June 2008, London, UK, Philadelphia, PA, Cambridge, MA

GlaxoSmithKline (GSK) announced today that it has completed its acquisition of Sirtris Pharmaceuticals, Inc. (Sirtris) for approximately USD720 million (or approx. GBP362 million) through a cash tender offer of USD22.50 (or approx. GBP11.33) per share.

Through the acquisition of Sirtris, GSK has significantly enhanced its metabolic, neurology, immunology and inflammation research efforts by establishing a presence in the field of sirtuins, a recently discovered class of enzymes that is believed to be involved in the ageing process.

Sirtris will become part of GSK’s Drug Discovery organisation, while continuing to operate from laboratories in Cambridge, Massachusetts as an autonomous drug discovery unit. Christoph Westphal, CEO and Vice Chair of Sirtris, and the management team will continue to lead this autonomous unit.

About GSK

GSK – 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 company information including a copy of this announcement and details of the company’s updated product development pipeline, visit GSK at www.gsk.com.

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