ROCKVILLE, Maryland, and LONDON, UK – November 16, 2010 – Human Genome Sciences, Inc. (Nasdaq: HGSI) and GlaxoSmithKline PLC (GSK) today announced that the Arthritis Advisory Committee of the U.S. Food and Drug Administration (FDA) has voted 13 to 2 to recommend that the FDA approve BENLYSTA® (belimumab) for the treatment of autoantibody-positive patients with active systemic lupus erythematosus (SLE).

The FDA Arthritis Advisory Committee is convened to provide the FDA with independent expert advice on a broad range of issues related to rheumatology drug products. The committee provides non-binding recommendations for consideration by FDA, with the final decision on approval made by FDA. The FDA has assigned BENLYSTA a Prescription Drug User Fee Act target date of December 9, 2010.

Belimumab is an investigational drug and the first in a new class of drugs called BLyS-specific inhibitors. HGS and GSK are developing belimumab under a definitive co-development and co-commercialization agreement entered into in 2006. Under the agreement, HGS has responsibility for conducting 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 commercialized under the current agreement.

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.

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

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. Health professionals and patients interested in clinical trials of HGS products may inquire via e-mail to medinfo@hgsi.com or by calling HGS at (877) 822-8472.

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

HGS contacts

Media:

Jerry Parrott

Vice President, Corporate Communications

301-315-2777

Investors:

Claudine Prowse, Ph.D.

Executive Director, Investor Relations

301-315-1785

Peter Vozzo

Senior Director, Investor Relations

301-251-6003

GSK contacts

U.K. Media Inquiries:

David Mawdsley, (020) 8047-5502

Claire Brough, (020) 8047-5502

Stephen Rea, (020) 8047-5502

Alexandra Harrison, (020) 8047-5502

Jo Revill, (020) 8047-5502

U.S. Media Inquiries:

Holly Russell, 919-483-2839

Mary Anne Rhyne, 919-483-2839

European Analyst/Investor Inquiries:

Sally Ferguson, (020) 8047-5543

Gary Davies, (020) 8047-5503

U.S. Analyst/Investor Inquiries:

Tom Curry, 215-751-5419

Jen Hill Baxter, 215-751-7002

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.

GlaxoSmithKline forward-looking statements

Under the safe harbor provisions of the US 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 GSK's Annual Report on Form 20-F for 2009.