Human Genome Sciences, Inc. reported results from a double-blind, placebo-controlled, multi-center Phase II clinical trial indicating that LymphoStat-B (belimumab) administered intravenously is safe, well tolerated, and results in a statistically significant reduction in the signs and symptoms of rheumatoid arthritis (RA).

Two-hundred eighty three patients with active, moderate-to-severe RA who had failed prior treatment (including, in some cases, at least one TNF-α inhibitor) were enrolled and randomly assigned to one of three doses of the study agent. The rate of ACR 20 response at week 24 was 36% in the 1 mg/kg low-dose, active-treatment cohort, and 31% in all active-treatment groups combined, versus an ACR 20 of 17% observed for the placebo group.

Belimumab is a human monoclonal antibody that neutralizes the activity of B-lymphocyte stimulator, or BLyS, a protein required for the development of B-lymphocytes into mature plasma B cells. Human Genome Sciences is developing LymphoStat-B as a potential treatment for systemic lupus erythematosus and other autoimmune diseases in addition to RA.