Human Genome Sciences to Receive $9 Million Milestone Payment Related to GlaxoSmithKline Initiation of Phase 3 Clinical Trial of Syncria(R) in Type 2 Diabetes

ROCKVILLE, Md., Feb. 17 /PRNewswire-FirstCall/ — Human Genome Sciences, Inc. (Nasdaq: HGSI) today announced that GlaxoSmithKline (NYSE: GSK) has initiated a Phase 3 clinical trial program to evaluate the efficacy, safety and tolerability of Syncria(R) (albiglutide) in the long-term treatment of type 2 diabetes mellitus. As a result, HGS will receive a $9 million milestone payment in the first quarter of 2009.

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“We are delighted that GSK has advanced Syncria to Phase 3 development, and we look forward to the future progress of this important program,” said H. Thomas Watkins, President and Chief Executive Officer, HGS.

Syncria is the fifth product to which HGS has substantial financial rights that has entered late-stage clinical development. It is a biological product generated from the genetic fusion of human albumin and modified human GLP-1 peptide, and is designed to act throughout the body to help maintain normal blood-sugar levels and to control appetite. Syncria was created by HGS using its proprietary albumin-fusion technology, and licensed to GSK in 2004. HGS is entitled to fees and milestone payments that could amount to as much as $183 million – including $24 million received to date – in addition to single-digit royalties on worldwide sales if Syncria is commercialized.

Attached is a press release issued earlier this morning by GSK (http://tinyurl.com/crprkt) announcing initiation of the Phase 3 program for Syncria. All inquiries regarding the development of Syncria should be directed to the contacts provided by GSK.

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. The HGS clinical development pipeline includes novel drugs to treat hepatitis C, lupus, inhalation anthrax and cancer.

The Company’s primary focus is rapid progress toward the commercialization of its two key lead drugs, Albuferon(R) (albinterferon alfa-2b) for hepatitis C and LymphoStat-B(R) (belimumab) for lupus. Albuferon successfully met its primary endpoint in the first of two Phase 3 trials in chronic hepatitis C; results of the second Albuferon Phase 3 trial are expected in March 2009. Two Phase 3 clinical trials of LymphoStat-B are ongoing, with results expected in July and November 2009.

In February 2009, HGS began delivery of 20,000 doses of ABthrax(TM) (raxibacumab) to the U.S. Strategic National Stockpile for use in the event of an emergency for the treatment of inhalation anthrax. The Company also has three drugs in clinical development for the treatment of cancer, including two TRAIL receptor antibodies and a small-molecule antagonist of IAP (inhibitor of apoptosis) proteins. In addition, HGS has substantial financial rights to certain products in the GSK clinical pipeline including darapladib, currently in Phase 3 development as a potential treatment for coronary heart disease, and Syncria(R) (albiglutide), currently in Phase 3 development as a potential treatment for type 2 diabetes.

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 clinical_trials@hgsi.com This e-mail address is being protected from spam bots, you need JavaScript enabled to view it or by calling HGS at (301) 610-5790, extension 3550.

HGS and Human Genome Sciences are trademarks of Human Genome Sciences, Inc.

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 the Company’s unproven business model, its dependence on new technologies, the uncertainty and timing of clinical trials, the Company’s 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, the Company’s 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 Securities and Exchange Commission. In addition, while the Company has begun shipment of ABthrax to the U.S. Strategic National Stockpile, the Company will continue to face risks related to acceptance of future shipments and FDA’s approval of the Company’s Biologics License Application for ABthrax, if and when it is submitted. If the Company is unable to meet requirements associated with the ABthrax contract, future revenues from the sale of ABthrax to the U.S. Government will not occur. 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.

SOURCE Human Genome Sciences, Inc.