HGS, GSK BEGIN STUDY OF LUPUS TREATMENT

Human Genome Sciences (HGS) and GlaxoSmithKline (GSK) have begun patient dosing in BLISS-76, one of two pivotal Phase III clinical trials of LymphoStat-B (belimumab) in patients with active systemic lupus erythematosus (SLE). LymphoStat-B is being developed by HGS and GSK under a definitive development and commercialization agreement entered into in August 2006.

HGS designed the Phase III development program for LymphoStat-B in collaboration with GSK and leading international SLE experts. The program includes two double-blind, placebo-controlled, multicenter superiority trials to evaluate the efficacy and safety of LymphoStat-B plus standard of care versus placebo plus standard of care in the treatment of patients with active SLE. HGS has initiated dosing in the first trial, BLISS-76, in which the duration of therapy will be 76 weeks. The data from BLISS-76 will be analyzed after 52 weeks to support a potential biologics license application. The second trial, BLISS-52, is expected to begin in the first half of 2007.

The primary efficacy endpoint of both studies is the patient response rate at week 52. Important secondary endpoints will include the patient response rate at week 76, the SF-36 Health Survey physical component summary score, fatigue measures and the percentage of patients with reduction from baseline in average prednisone dose at weeks 40 to 52. Safety and tolerability will be evaluated by an independent data monitoring committee throughout both studies.

In each of the trials, approximately 810 patients will be enrolled and randomized to one of three treatment groups: 1 mg/kg LymphoStat-B, 10 mg/kg LymphoStat-B or placebo. Patients will be dosed intravenously on days zero, 14 and 28, then every 28 days for the duration of the study.

LymphoStat-B is a human monoclonal antibody that specifically recognizes and inhibits the biological activity of B-lymphocyte stimulator, or BLyS. BLyS is a naturally occurring protein discovered by HGS that is required for the development of B-lymphocyte cells into mature plasma B cells. Plasma B cells produce antibodies, the body's first line of defense against infection. In lupus, rheumatoid arthritis and certain other autoimmune diseases, elevated levels of BLyS are believed to contribute to the production of autoantibodies -- antibodies that attack and destroy the body's own healthy tissues.