Human Genome Sciences Announces Initiation of Phase 2b Trial 0f Albuferon Dosed Monthly in Chronic Hepatitis C

Trial conducted by Novartis to evaluate safety and efficacy of Albuferon administered every four weeks in combination with ribavirin in patients with genotypes 2 and 3 hepatitis C

Rockville, MD -- January 12, 2009 -- Human Genome Sciences, Inc. (Nasdaq: HGSI) today announced that Novartis has initiated dosing in a Phase 2b trial that will evaluate the safety and efficacy of Albuferon (albinterferon alfa-2b) administered monthly in combination with ribavirin in treatment-naive patients with genotypes 2 and 3 chronic hepatitis C. Albuferon is being developed by HGS and Novartis under an exclusive worldwide co-development and commercialization agreement entered into in June 2006.

"Patients undergoing treatment for chronic hepatitis C often find it challenging to participate in normal daily activities, especially in the days following dose administration," said Stephen Pianko, MD, FRACP, PhD, Monash University, Melbourne, Australia. "Pegylated interferons, the current standard of care, require administration once every week. Albinterferon alfa-2b dosed every four weeks with a total of six injections could offer an important treatment option, if it demonstrates comparable safety and efficacy vs. peginterferon alfa-2a dosed weekly with a total of 24 injections."

In December 2008, HGS announced that Albuferon met its primary endpoint of non-inferiority to peginterferon alfa-2a (Pegasys) in ACHIEVE 2/3, a Phase 3 clinical trial of Albuferon in combination with ribavirin in treatment-naive patients with genotypes 2 and 3 chronic hepatitis C. In these patients, the Phase 3 study showed that 900-mcg Albuferon administered every two weeks had efficacy comparable to peginterferon alfa-2a [Pegasys], with comparable rates of severe and/or serious adverse events and discontinuations due to adverse events.

"Hepatitis C is the most common chronic blood-borne infection in the developed world, and there continues to be a significant need for more effective and better tolerated treatments," said Mani Subramanian, MD, PhD, Executive Director, Clinical Research - Infectious Diseases, HGS. "Only an estimated 40% of U.S. patients diagnosed with chronic hepatitis C have undertaken treatment to date - in part due to the side effects associated with interferon injections, which are currently required on a weekly basis. A monthly dosing schedule with Albuferon may well result in more patients choosing to be treated."

About the Design of the Phase 2b Monthly Dosing Trial

This Phase 2b trial is a randomized, open-label, multi-center, active-controlled, adaptive-design dose-ranging study to evaluate the safety and efficacy of albinterferon alfa-2b administered every four weeks plus daily ribavirin in treatment-naive patients with genotypes 2 and 3 chronic hepatitis C. Approximately 375 patients will be randomized in a 4:4:4:3 ratio into four treatment groups, including three that will receive albinterferon alfa-2b administered once every four weeks (900 mcg, 1200 mcg or 1500 mcg), in addition to the active-control group, which will receive peginterferon alfa-2a at the standard 180-mcg dose once every week. All patients in the study will receive 800-mg daily oral ribavirin. The total duration of treatment will be 24 weeks. The primary efficacy endpoint is sustained virologic response (SVR) at Week 48 (24 weeks following the end of treatment).

About Albinterferon Alfa-2b (Albuferon)

Albinterferon alfa-2b is a novel, longer-acting form of interferon alfa that was created using the proprietary HGS albumin-fusion technology. Human albumin is the most prevalent naturally occurring blood protein in the human circulatory system, persisting in circulation in the body for approximately 19 days. Research has shown that genetic fusion of therapeutic proteins to human albumin decreases clearance and prolongs the half-life of the therapeutic proteins. Albuferon results from the genetic fusion of human albumin and interferon alfa.

Albuferon is being developed by HGS and Novartis for the treatment of chronic hepatitis C under an exclusive 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.