GlaxoSmithKline and Human Genome Sciences announce FDA priority review designation for Benlysta® (belimumab) as a potential treatment for systemic lupus erythematosus

Issued: London UK & Rockville, Maryland, US

GlaxoSmithKline PLC (GSK) and Human Genome Sciences, Inc. today announced that the U.S. Food and Drug Administration (FDA) has granted a priority review designation to Benlysta^® (belimumab) as a potential treatment for systemic lupus erythematosus (SLE). A priority review designation is granted to drugs that, if approved, offer major advances in treatment or provide a treatment where no adequate therapy exists. The FDA has assigned belimumab a Prescription Drug User Fee Act (PDUFA) target date of 9 December 2010.

The Biologics License Application (BLA) for belimumab was submitted to the FDA on 9 June 2010, and includes the results of two pivotal Phase 3 clinical trials that treated a total of 1,684 autoantibody-positive patients with SLE. HGS designed the Phase 3 programme for belimumab in collaboration with GSK and leading international SLE experts, and in consultation with the FDA.

“We are very pleased that FDA has chosen to grant priority review to belimumab, the first in a new class of drugs called BLyS-specific inhibitors,” said H. Thomas Watkins, President and Chief Executive Officer, HGS. “We believe that the priority review designation speaks both to the significant medical need of people living with lupus and to the potential belimumab may hold as a new treatment option for these patients.”

Carlo Russo, M.D., Senior Vice President, Biopharm Development, GSK, said, “Belimumab is the first medicine for lupus that has completed Phase 3 trials with positive results. We look forward to continuing to work together with HGS to progress regulatory files and we hope that we will be able to deliver a new treatment option for patients living with lupus.”

GSK submitted a Marketing Authorisation Application for belimumab to the European Medicines Agency (EMA) on 4 June 2010.

About the HGS/GSK Collaboration

In 2006, HGS and GSK entered into a definitive co-development and commercialisation agreement under which HGS has conducted the belimumab Phase 3 trials, with assistance from GSK. The companies will share equally in Phase 3/4 development costs, sales and marketing expenses, and profits of any product commercialised under the agreement.

About GlaxoSmithKline

GSK Biopharm R&D is employing novel approaches to harness the therapeutic potential of biopharmaceuticals for the benefit of patients with serious autoimmune disease.

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

About Human Genome Sciences

The mission of HGS is to apply great science and great medicine to bring innovative drugs to patients with unmet medical needs. For more information about HGS, please visit the Company’s web site at www.hgsi.com

HGS, Human Genome Sciences, and BENLYSTA are trademarks of Human Genome Sciences, Inc. Other trademarks referenced are the property of their respective owners.

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 2009.

HGS Safe Harbor Statement

This announcement contains forward-looking statements within the meaning of Section 27A of the Securities Act of 1933, as amended, and Section 21E of the Securities Exchange Act of 1934, as amended. The forward-looking statements are based on Human Genome Sciences’ current intent, belief and expectations. These statements are not guarantees of future performance and are subject to certain risks and uncertainties that are difficult to predict. Actual results may differ materially from these forward-looking statements because of Human Genome Sciences’ unproven business model, its dependence on new technologies, the uncertainty and timing of clinical trials and regulatory approvals, Human Genome Sciences’ ability to develop and commercialize products, its dependence on collaborators for services and revenue, its substantial indebtedness and lease obligations, its changing requirements and costs associated with facilities, intense competition, the uncertainty of patent and intellectual property protection, Human Genome Sciences’ dependence on key management and key suppliers, the uncertainty of regulation of products, the impact of future alliances or transactions and other risks described in the Company’s filings with the SEC. Existing and prospective investors are cautioned not to place undue reliance on these forward-looking statements, which speak only as of today’s date. Human Genome Sciences undertakes no obligation to update or revise the information contained in this announcement whether as a result of new information, future events or circumstances or otherwise.