ROCKVILLE, Maryland and LONDON, England—Benlysta™ (belimumab, formerly LymphoStat-B^®) met the primary endpoint in BLISS-52, the first of two pivotal Phase 3 trials in patients with active systemic lupus erythematosus (SLE), and is on track to be the first new lupus treatment in more than 50 years, according to a company announcement.

Human Genome Sciences, Inc and GlaxoSmithKline PLC announced that the placebo-controlled BLISS-52 results showed that belimumab plus standard of care achieved a clinically and statistically significant improvement in patient response rate at Week 52, compared with standard of care alone. Study results also showed that belimumab was generally well tolerated, with adverse event rates comparable to placebo.

“The BLISS-52 results demonstrated that Benlysta has the potential to become the first new approved drug in decades for people living with systemic lupus,” said H. Thomas Watkins, President and Chief Executive Officer, HGS. “Given the limited treatment options currently available, patients would benefit greatly from potential new treatments...Assuming positive results in November from our second Phase 3 trial of BENLYSTA, we and GSK plan to submit marketing applications in the United States, Europe and other regions in the first half of 2010.”

A greater percentage of patients receiving Benlysta achieved a clinically meaningful reduction in steroid dose. Based on an intention-to-treat (ITT) analysis, belimumab met its primary efficacy endpoint of superiority versus placebo at Week 52, and produced clinically and statistically significant improvements in patient response rate for belimumab plus standard of care, versus placebo plus standard of care.

Professor Sandra V. Navarra, MD, a principal investigator and Head of Rheumatology at the University of Santo Tomas, Manila, Philippines, said, “Given the limitations of available therapies, there is a great need for well tolerated and effective treatments for lupus. We are very encouraged by the findings of BLISS-52, and look forward to presenting these results later in the year. We also look forward to the results of BLISS-76 later this year.”

Belimumab is the first in a new class of drugs called BLyS-specific inhibitors and is being developed by HGS and GSK under a co-development and commercialization agreement entered into in August 2006. Belimumab is an investigational human monoclonal antibody drug that specifically recognizes and inhibits the biological activity of B-lymphocyte stimulator, or BLyS^®. BLyS is a naturally occurring protein that is required for the development of B-lymphocyte cells into mature, antibody-producing plasma B cells.

The Human Genome Sciences Inc stock price more than tripled in New York trading after the announcement.

If Benlysta succeeds in the second phase 3 trial, the companies expect to apply for marketing approval in the US and in Europe in 2010.