Human Genome Sciences and GlaxoSmithKline to present Phase 3 trial results of BENLYSTA

Human Genome Sciences, Inc. (Nasdaq: HGSI) and GlaxoSmithKline PLC (GSK) today announced the full presentation of results from BLISS-52, the first of two pivotal Phase 3 trials of BENLYSTA™ (belimumab) in seropositive patients with systemic lupus erythematosus (SLE). The data, which will be presented today in Philadelphia at the 73^rd Annual Scientific Meeting of the American College of Rheumatology (ACR), demonstrate that, in BLISS-52, belimumab plus standard of care achieved a clinically and statistically significant improvement in patient response rate as measured by the SLE Responder Index at Week 52, compared with placebo plus standard of care. Study results also show that belimumab was generally well tolerated, with adverse event rates comparable between belimumab and placebo treatment groups.

“The BLISS-52 Phase 3 results presented at ACR demonstrate that the efficacy of treatment with BENLYSTA plus standard of care was superior to that of placebo plus standard of care,” said David C. Stump, M.D., Executive Vice President, Research and Development, HGS. “These data were statistically significant and were strongly supported across multiple measures of clinical effect and multiple time-points. Of note, a greater percentage of patients receiving BENLYSTA were able to reduce their use of steroids.”

Carlo Russo, M.D., Senior Vice President, Biopharm Development, GSK, said, “We have been pleased by the consistency of benefit demonstrated by belimumab in the BLISS-52 study, and we hope to confirm these results in the second Phase 3 study which is to report shortly. We very much hope that we will be able to deliver a new option for the treatment of this debilitating disease.”

Belimumab is an investigational drug and the first in a new class of drugs called BLyS-specific inhibitors. No new drug for lupus has been approved by regulatory authorities in more than 50 years. Belimumab is being developed by HGS and GSK under a co-development and commercialization agreement entered into in August 2006. Results from BLISS-76, the second Phase 3 trial of belimumab, will be announced on November 2, 2009. Assuming the results from BLISS-76 are positive, HGS and GSK plan to submit marketing applications in the United States, Europe and other regions in the first half of 2010.