September 2, 2008

Human Genome Sciences Reports Initial Results of Randomized Phase 2 Trial of HGS-ETR1 in Combination With Bortezomib in Advanced Multiple Myeloma

ROCKVILLE, Md., Sept. 2 /PRNewswire-FirstCall/ -- Human Genome Sciences, Inc. today reported initial topline results from an ongoing randomized Phase 2 clinical trial of its TRAIL receptor antibody HGS-ETR1 (mapatumumab) in combination with bortezomib (Velcade) in patients with advanced multiple myeloma. The initial data from the multiple myeloma study show that HGS-ETR1 was well tolerated and suggest that disease response was comparable for this combination vs. bortezomib alone.

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"We continue to be excited about HGS-ETR1 and our TRAIL receptor antibody program," said David C. Stump, M.D., Executive Vice President, Research and Development, HGS. "The TRAIL-mediated apoptosis pathway is an important area of cancer research, and agonistic antibodies to this target offer great promise. HGS-ETR1 is the most advanced of any product in development that targets this pathway, with three randomized chemotherapy combination trials currently ongoing to evaluate its potential for the treatment of specific cancers. We look forward to maturing results from all three trials. Taken together, these results will inform our decision on whether to advance HGS- ETR1 to Phase 3 development."

Key Findings

The trial in advanced multiple myeloma is a randomized, multi-center, open-label Phase 2 study to evaluate the efficacy and safety of HGS-ETR1 (mapatumumab) in combination with bortezomib in these patients. 104 patients are being treated in the study, which is being conducted in the United States, Canada, Australia and India. Patients were randomized into three treatment groups, with one group receiving bortezomib alone and two groups receiving bortezomib in combination with mapatumumab (10 mg/kg or 20 mg/kg). Approximately 43% (15/35) of the patients in the group receiving bortezomib alone were randomized contemporaneously with randomization of the group receiving a combination of bortezomib and mapatumumab at 10 mg/kg. The remaining 57% (20/35) of the patients in the group receiving bortezomib alone were randomized contemporaneously with randomization of the group receiving a combination of bortezomib and mapatumumab at 20 mg/kg. The primary objective of the study is to evaluate disease response to mapatumumab in combination with bortezomib, versus bortezomib alone, in patients with relapsed or refractory multiple myeloma. Secondary objectives include evaluation of progression-free survival, safety and tolerability, and plasma concentrations of mapatumumab for use in a population pharmacokinetic analysis.

Patients participating in the study had received a median of 2 previous cancer treatment regimens. At baseline, 17.1% (6/35) of patients in the treatment group receiving bortezomib alone had Stage 3 disease, vs. 40.6% (13/33) in the group receiving the combination of bortezomib and mapatumumab at 10 mg/kg, and 19.4% (7/36) in the group receiving the combination of bortezomib and mapatumumab at 20 mg/kg. The initial data show that mapatumumab was well tolerated and could be administered safely and repetitively in combination with bortezomib, with no evidence of increased toxicity in patients receiving the combination of bortezomib and mapatumumab, vs. patients receiving bortezomib alone.

Overall, based on initial data, disease response was comparable among the three treatment groups, including the following findings:

-- Three complete responses (8.3%; N=36) were observed among patients in the treatment group receiving the combination of bortezomib and mapatumumab at 20 mg/kg, vs. no complete responses in the group receiving bortezomib alone.

-- Clinical responses were observed in 51.4% (18/35) of patients in the treatment group receiving bortezomib alone (0 complete and 18 partial). The response rate observed for bortezomib in the current study compares with a response rate identified in the FDA-approved bortezomib label of approximately 38%.

-- Clinical responses were observed in 50.0% (18/36) of patients in the treatment group receiving the combination of bortezomib and mapatumumab at 20 mg/kg (3 complete and 15 partial).

-- Clinical responses were observed in 30.3% (10/33) of patients in the treatment group receiving the combination of bortezomib and mapatumumab at 10 mg/kg (0 complete and 10 partial).

-- Stable disease was observed in approximately a third of the patients on study and was comparable across all treatment groups.

The multiple myeloma study is ongoing, and 58 patients in this study have not yet experienced disease progression and continue to be treated and/or followed.

About the HGS-ETR1 Proof-of-Concept Trials

The HGS-ETR1 proof-of-concept phase currently includes three randomized trials to evaluate its potential in combination with chemotherapy for the treatment of specific cancers:

-- Patients in the multiple myeloma trial will continue on treatment until the progression of disease, and HGS expects to have final data available from this study in 2009, including data on the important secondary endpoint of progression-free survival.

-- In August 2008, the Company completed the enrollment and initial dosing of patients in a randomized Phase 2 trial of HGS-ETR1 (10 mg/kg or 30 mg/kg) in combination with paclitaxel and carboplatin as first-line therapy in patients with advanced non-small cell lung cancer (NSCLC); initial data from the study are anticipated in 2009.

-- In July 2008, HGS initiated dosing in the safety lead-in to a randomized Phase 2 trial of HGS-ETR1 in combination with Nexavar (sorafenib) in patients with advanced hepatocellular cancer, which accounts for 80-90% of all liver cancers.

These three trials, taken together, will support a decision on whether to advance HGS-ETR1 to Phase 3 development. It also is possible that a sufficiently positive result from any one of the trials could lead to a Phase 3 decision for that specific indication.

About Multiple Myeloma

Multiple myeloma is a cancer of the plasma cells in bone marrow. In the United States each year, there are approximately 11,000 deaths from multiple myeloma, with approximately 16,000 new cases diagnosed. It accounts for about 10% of all hematologic cancers.

About HGS-ETR1

HGS-ETR1 (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. Using genomic techniques, HGS originally identified the TRAIL receptor 1 protein. The HGS-ETR1 antibody was generated by HGS through collaboration with Cambridge Antibody Technology. HGS is developing HGS-ETR1 as a potential treatment for a broad range of cancers.

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, cancer and other immune-mediated diseases. 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. Phase 3 clinical trials of both drugs are ongoing.

ABthrax(TM) (raxibacumab) is in late-stage development for the treatment of inhalation anthrax, and the Company is on track to begin the delivery in fall 2008 of 20,000 doses of ABthrax to the Strategic National Stockpile under a contract entered into with the U.S. Government in June 2006. HGS 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 development pipeline.

For more information about HGS, please visit the Company's web site at Health professionals and patients interested in clinical trials of HGS products may inquire via e-mail to [email protected] 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, Human Genome Sciences, ABthrax, Albuferon and LymphoStat-B 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, the Company will continue to face risks related to animal and human testing, to the manufacture of ABthrax and to FDA concurrence that ABthrax meets the requirements of the ABthrax contract. If the Company is unable to meet the product requirements associated with the ABthrax contract, the U.S. government will not be required to reimburse the Company for the costs incurred or to purchase any ABthrax doses, and we will not receive any of the expected revenues relative to ABthrax. 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.

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Human Genome Sciences, Inc.

CONTACT: Media, Jerry Parrott, Vice President, Corporate Communications,+1-301-315-2777; Investors, Tim Barabe, Senior Vice President and ChiefFinancial Officer, +1-301-315-1780, both of Human Genome Sciences, Inc.

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