Human Genome Sciences Announces Results of Randomized Phase 2 Trial of Mapatumumab in Non-Small Cell Lung Cancer

Human Genome Sciences, Inc. (Nasdaq: HGSI) today announced the results of its randomized Phase 2 trial of mapatumumab (HGS-ETR1) in combination with the chemotherapy agents paclitaxel and carboplatin as first-line therapy in advanced non-small cell lung cancer (NSCLC).

The results showed no difference in disease response or progression-free survival for the combination that included mapatumumab vs. the control group, and showed that mapatumumab was well tolerated in this study. HGS expects to present the results in full at an appropriate scientific meeting later in 2010.

About the HGS Oncology Program

Mapatumumab is an agonistic human monoclonal antibody that directly induces cancer cell death by specifically binding to and activating the protein known as TRAIL receptor 1. It is the most advanced of any product in development that targets the TRAIL apoptosis pathway. Randomized Phase 2 chemotherapy combination trials are currently underway to evaluate mapatumumab’s potential in the treatment of advanced multiple myeloma and hepatocellular cancer. HGS expects to have progression-free survival data available from the multiple myeloma study in mid-2010, and expects to initiate the randomization stage of the hepatocellular cancer study before the end of 2010. The Company is investing strategically to expand and advance its oncology portfolio around its expertise in the apoptosis, or programmed cell death, pathway.

In November 2009, HGS and Aegera Therapeutics announced the initiation of a Phase 1 trial of HGS’ lead IAP inhibitor, HGS1029, as monotherapy in patients with advanced lymphoid tumors. HGS1029 as monotherapy is also being studied in an ongoing Phase 1 study initiated in 2008 in patients with advanced solid tumors. The IAP inhibitors are a novel class of compounds that block the activity of IAP (inhibitor of apoptosis) proteins, allowing apoptosis to proceed and causing the cancer cells to die. When IAP proteins are over-expressed in cancer cells, they can help cancer cells resist apoptosis and resume growth and proliferation. HGS plans to continue the study of HGS1029 both alone and in combination with other anti-cancer agents, including mapatumumab.

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 lupus, hepatitis C, inhalation anthrax and cancer.

The Company’s primary focus is rapid progress toward the commercialization of its two lead drugs, BENLYSTA™ (belimumab) for systemic lupus and ZALBIN™ (albinterferon alfa-2b) for hepatitis C. Phase 3 development has been completed successfully for both BENLYSTA and ZALBIN. The submission of marketing applications for BENLYSTA is planned in the U.S., Europe and other regions in the second quarter of 2010. A BLA has been submitted for ZALBIN to the FDA in the United States, and an MAA has been submitted under the brand name JOULFERON® to the EMEA in Europe.

In April 2009, HGS completed the delivery of 20,000 doses of raxibacumab to the U.S. Strategic National Stockpile for use in the event of an emergency to treat inhalation anthrax. In July 2009, HGS secured a new purchase order for 45,000 doses, and the Company delivered the first 5,600 doses to the Stockpile under the new order in November 2009.

HGS also has several drugs in earlier stages of development for treatment of cancer, led by the TRAIL receptor antibody mapatumumab and a small-molecule antagonist of inhibitor-of-apoptosis proteins. In addition, HGS has substantial financial rights to certain products in the GSK clinical pipeline including darapladib, in Phase 3 development in patients with coronary heart disease, and Syncria® (albiglutide), in Phase 3 development in patients with 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 medinfo@hgsi.com or by calling HGS at (877) 822-8472.

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

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, 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.