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Human Genome Sciences Reports Growing Evidence That Its TRAILReceptor Antibodies Have Significant Potential in the Treatment ofa Broad Range of Cancers

- Journal of Clinical Oncology publishes first clinical study of HGS-ETR1 -

ROCKVILLE, Md., April 27, 2007 /PRNewswire-FirstCall/ -- Human Genome Sciences, Inc. today reported that clinical and preclinical evidence continues to emerge demonstrating that its TRAIL receptor antibodies, HGS-ETR1 (mapatumumab) and HGS-ETR2 (lexatumumab), have significant potential for use in the treatment of a broad range of cancers.

"We believe that HGS-ETR1 and HGS-ETR2 could offer novel, highly targeted therapeutic options that may prove useful in the treatment of a number of cancers," said Gilles Gallant, B. Pharm., Ph.D., Vice President, Clinical Research - Oncology, HGS. "We note with pride that the Journal of Clinical Oncology, one of the field's most prestigious peer-reviewed publications, chose to publish the first human study of HGS-ETR1 earlier this month with an accompanying editorial - and, last week at AACR 2007, approximately 1500 cancer scientists and researchers attended our oral presentation of research results to date."

Results in the Journal of Clinical Oncology

The results of the first Phase 1 clinical trial of mapatumumab (HGS-ETR1) appeared in the April 10 issue of the Journal of Clinical Oncology (JCO), the official journal of the American Society of Clinical Oncology (ASCO). These results in 49 patients demonstrated that mapatumumab could be administered safely and repetitively to patients with advanced solid malignancies. The authors concluded that the absence of severe toxicities, and mapatumumab's ability to achieve blood levels consistent with antitumor activity in laboratory models, warrant further study of mapatumumab as a single agent and in combination with chemotherapy in a broad array of tumors.

Based on the initial Phase 1 results, along with extensive preclinical data, HGS initiated a broad clinical development program that included Phase 2 trials of HGS-ETR1 as a single agent in advanced non-small cell lung cancer, colorectal cancer and non-Hodgkin's lymphoma. It was demonstrated that HGS-ETR1 has single-agent antitumor activity (complete and partial responses) in non-Hodgkin's follicular B-cell lymphoma. The Company is also conducting Phase 1b studies of HGS-ETR1 in combination with chemotherapy.

An accompanying editorial in JCO commented that, "The main goals ahead with these agents will be increasing our understanding of the biologic mechanisms underlying tumor response versus resistance, pursuing logical combinations that counter these resistant mechanisms, and considering appropriate patient selection to enrich for a responsive population."

Presentations at AACR 2007

At the Annual Meeting of the American Association of Cancer Research last week, Robin C. Humphrey, Ph.D., Senior Scientist and preclinical lead, HGS oncology research, presented an overview of preclinical and clinical studies to date for both of the HGS TRAIL receptor antibodies. Results to date show that HGS-ETR1 and HGS-ETR2 specifically bind to TRAIL receptor 1 or TRAIL receptor 2, respectively, and directly induce programmed cell death, or apoptosis, in a broad array of cancer cell lines and primary cancer cells derived from both solid and hematologic human tumors. Results of studies in tumor cell xenografts demonstrate that HGS-ETR1 and HGS-ETR2 cause significant inhibition of tumor growth, including rapid tumor regression in a number of models. Studies have also shown that both of the HGS TRAIL receptor antibodies are active in combination with a spectrum of conventional or novel therapeutic agents, including chemotherapy, radiation and proteosome inhibitors. Both HGS-ETR1 and HGS-ETR2 are currently being evaluated in clinical trials in a variety of human tumors.

In a separate poster presentation, results were reported from a preclinical study, which demonstrated that low concentrations of Velcade (bortezomib) can be used to sensitize certain non-small cell lung cancer cell lines that are resistant to killing by TRAIL receptor-activated apoptosis, making it possible for HGS-ETR1 or HGS-ETR2 to activate cell death.

About HGS-ETR1 and HGS-ETR2

HGS-ETR1 and HGS-ETR2 are agonistic human monoclonal antibodies to TRAIL receptors 1 and 2, respectively. Both were generated by HGS through a collaboration with Cambridge Antibody Technology. HGS is developing HGS-ETR1 and HGS-ETR2 as potential treatments for a broad range of cancers.

GlaxoSmithKline (GSK) has exercised its option under a June 1996 agreement to develop and commercialize HGS-ETR1 jointly with HGS. Under the terms of the agreement, GSK and HGS will share equally in Phase 3/4 development costs, and will share equally in sales and marketing expenses and profits of any product commercialized under the agreement, under a co-development and co- promotion agreement, the remaining terms of which are being negotiated by the parties.

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, anthrax disease, cancer, rheumatoid arthritis and HIV/AIDS. The Company's primary focus is rapid progress toward the commercialization of its two lead compounds, Albuferon(R) for hepatitis C, and LymphoStat-B(R) for lupus. Phase 3 clinical trials of both compounds are now underway.

In June 2006, HGS announced that the U.S. Government exercised its option under an existing contract to purchase 20,000 doses of ABthrax(TM) for the treatment of anthrax disease. Other HGS drugs in clinical development include two TRAIL receptor antibodies for the treatment of hematologic and solid malignancies, in addition to an antibody to the CCR5 receptor for the treatment of HIV/AIDS.

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. 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.

Posted: April 2007