PRESS RELEASE: Human Genome Sciences Completes Enrollment Ahead of Schedule in Second Phase 3 Albuferon(R) Trial

Human Genome Sciences Completes Enrollment Ahead of Schedule in Second Phase 3 Albuferon(R) Trial

ROCKVILLE, Md., Nov. 1  -- Human Genome Sciences, Inc. today announced that it has completed enrollment and initial dosing ahead of schedule in ACHIEVE 2/3, the second of two pivotal global Phase 3 trials of Albuferon(R) (albinterferon alfa-2b) in combination with ribavirin in treatment-naive patients with chronic hepatitis C. ACHIEVE 2/3 is being conducted in patients with genotypes 2 and 3 chronic hepatitis C.

(Logo: http://www.newscom.com/cgi-bin/prnh/20010612/HGSLOGO )

"We are ahead of our original schedule with both Phase 3 trials of Albuferon and we expect the filing of global marketing applications by fall 2009," said H. Thomas Watkins, President and Chief Executive Officer, HGS. "If the results of our Phase 2 trials are confirmed in Phase 3, we believe Albuferon could become the interferon of choice for the treatment of chronic hepatitis C.

ACHIEVE 2/3 enrolled 933 treatment-naive patients with genotypes 2 and 3 chronic hepatitis C. ACHIEVE 1, the first of the two Phase 3 trials, completed enrollment of 1331 treatment-naive patients with genotype 1 chronic hepatitis C in August 2007. HGS originally projected enrollment of the Phase 3 trials by the end of 2007. Albuferon is being developed by HGS and Novartis under an exclusive worldwide co-development and commercialization agreement entered into in 2006.

"Albuferon requires half as many injections as the long-acting interferons that are currently in use," said David Nelson, M.D., lead investigator of the ACHIEVE 2/3 trial, and Associate Professor of Medicine, Medical Director of Liver Transplantation, and Chief of the Hepatobiliary Disease Section, University of Florida. "In previous studies, Albuferon showed efficacy at least comparable to the pegylated interferons, with comparable safety and significant potential for improving quality of life on treatment. Albuferon could play an important role in the treatment of chronic hepatitis C, and we look forward to completing the Phase 3 studies."

About the Albuferon Phase 3 Development Program

The Albuferon Phase 3 clinical development program includes two randomized, open-label, active-controlled, multi-center, non-inferiority trials -- ACHIEVE 1 and ACHIEVE 2/3 -- to evaluate the efficacy, safety and impact on health-related quality of life of Albuferon in combination with ribavirin versus Pegasys (peginterferon alfa-2a) in combination with ribavirin.

"We are pleased with the rapid progress of enrollment in both Phase 3 trials of Albuferon, and consider it evidence of the high level of interest among those who treat hepatitis C," said Mani Subramanian, M.D., Ph.D., Senior Director of Clinical Research, Infectious Diseases, HGS.

Higher doses of Albuferon administered monthly, in combination with ribavirin, will be explored in a separate Phase 2b trial conducted by Novartis, which is expected to begin by year-end 2007.

About Albuferon

Albuferon is a novel long-acting form of interferon alpha created by HGS using its proprietary albumin fusion technology. Albuferon results from the genetic fusion of human albumin and interferon alpha. Human albumin is the most prevalent naturally occurring blood protein in the human circulatory system, persisting in circulation in the body for more than 20 days. Research shows that genetic fusion of therapeutic proteins to human albumin decreases clearance and prolongs the half-life of the proteins. Recombinant interferon alpha is approved for the treatment of hepatitis C, hepatitis B and a number of cancers.

Under the worldwide co-development and commercialization agreement entered into in June 2006, HGS and Novartis will co-commercialize Albuferon in the United States and will share clinical development costs, U.S. commercialization costs and U.S. profits equally. Novartis will be responsible for commercialization in the rest of the world and will pay HGS a royalty on those sales. Clinical development, commercial milestone and other payments to HGS could total as much as $507.5 million, including $132.5 million received to date.

About Hepatitis C

Hepatitis C is an inflammation of the liver caused by the hepatitis C virus. An estimated 170 million people worldwide are infected with the virus, including nearly 4 million people in the United States. When detectable levels of the hepatitis C virus persist in the blood for at least six months, a person is diagnosed with chronic hepatitis C. The hepatitis C virus can cause serious liver disease, leading to cirrhosis, primary liver cancer and even death.

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 and other immune-mediated diseases. The Company's primary focus is rapid progress toward the commercialization of its two key lead drugs, Albuferon 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 anthrax disease, and the Company is on track to begin the delivery in 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. Other HGS drugs in clinical development include two TRAIL receptor antibodies for the treatment of cancers.

For more information about HGS, please visit the Company's web site at www.hgsi.com. For more information about Albuferon, please visit www.hgsi.com/products/albuferon.html. Health professionals or patients interested in Albuferon clinical trials or other studies involving HGS products may inquire via the "Contact Us" section of the Company's web site, www.hgsi.com/products/request.html, or by calling (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. 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.