This press release is intended for business journalists and analysts/investors. Please note that this release may not have been issued in every market in which GSK operates.

Issued: Thursday 13 September 2012, London, UK

GlaxoSmithKline plc (LSE: GSK) today announces that it has acquired five million newly issued shares of Response Genetics Inc. (RGI) (NASDAQ: RGDX) common stock at a purchase price of US$1.10 per share in cash. As a result, GSK now owns approximately 15.2% of the expanded share capital of RGI.

This transaction builds on the relationship GSK and RGI have been building over the years in the diagnostics field of oncology and vaccines. RGI performs companion diagnostic tests and other related activities for GSK's immunotherapies and oncology pipeline candidates.

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

GlaxoSmithKline Enquiries:

UK Media enquiries:

David Mawdsley

+44 (0) 20 8047 5502

(London)

Stephen Rea

+44 (0) 20 8047 5502

(London)

Sarah Spencer

+44 (0) 20 8047 5502

(London)

David Daley

+44 (0) 20 8047 5502

(London)

US Media enquiries:

Kevin Colgan

+1 919 483 2933

(North Carolina)

Melinda Stubbee

+1 919 483 2510

(North Carolina)

Sarah Alspach

+1 202 715 1048

(Washington, DC)

Jennifer Armstrong

+1 215 751 5664

(Philadelphia)

Analyst/Investor enquiries:

Sally Ferguson

+44 (0) 20 8047 5543

(London)

Tom Curry

+ 1 215 751 5419

(Philadelphia)

Gary Davies

+ 44 (0) 20 8047 5503

(London)

James Dodwell

+ 44 (0) 20 8047 2406

(London)

Jeff McLaughlin

+ 1 215 751 7002

(Philadelphia)

Ziba Shamsi

+ 44 (0) 20 8047 3289

(London)

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 'Financial review & risk' section in the company's Annual Report 2011 included as exhibit 15.2 to the company's Annual Report on Form 20-F for 2011.

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