Pandemic (H1N1) 2009 Influenza Update: Initial results from first clinical trial of GSK’s H1N1 adjuvanted vaccine

London UK - GlaxoSmithKline (GSK) today announced results from its first clinical trial assessing use of its pandemic (H1N1) adjuvanted vaccine. The results demonstrate that after one dose the candidate vaccine can provide a strong immune response which exceeds the immunogenicity criteria as defined by international licensing authorities for a pandemic influenza vaccine.

The trial, which is taking place in Germany, involves 130 healthy volunteers aged 18 to 60 years old, and has been designed to evaluate the tolerability and immunogenicity of GSK’s split-virus pandemic (H1N1) adjuvanted vaccine in comparison with an unadjuvanted test study formulation.

In this trial, the antigen content of the adjuvanted vaccine is 5.25ug and in the unadjuvanted vaccine is 21ug. The antigen content of the adjuvanted vaccine is comparable to the expected final formulation of the adjuvanted vaccine of 3.75ug.

Results of the adjuvanted vaccine demonstrated that hemagglutination-inhibition titres exceeded the regulatory threshold, with a 1:40 seroconversion in more than 98% of subjects receiving the first dose. In the unadjuvanted group, 95% of the subjects reached the same threshold. These results were obtained 3 weeks following vaccination. Further characterisation of the immune response is being studied and how this may relate to prediction of efficacy.

“This trial provides encouraging data on the potential use of a single dose of our pandemic vaccine.” said Jean Stephenne, President GlaxoSmithKline Biologicals. "We have shared these data with both regulatory authorities and governments who are making key decisions on urgent global public healthcare at this time. Our next step is to complete this trial, as well as 15 other studies in our clinical development programme for the vaccine.”

GSK is conducting a further 15 studies in over 9000 subjects including healthy adults, the elderly and children (including infants) across Europe, Canada and the US to evaluate its pandemic (H1N1) adjuvanted vaccine. All the data from this clinical development programme will be submitted to the regulators as soon as they are available and they will also be posted on GSK’s Clinical Study Register.

GSK will continue to work closely with regulators, governments and health authorities around the world, providing them with clinical data which may help them to determine the most appropriate strategy to address the H1N1 pandemic.

Further information on GSK’s development of a vaccine to protect against pandemic (H1N1) 2009, including explanation of the vaccine development process and background information on adjuvants is available on: http://www.gsk.com/media/pandemic-flu.htm

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

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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.

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