GlaxoSmithKline and Human Genome Sciences reported that the companies' experimental lupus drug Benlysta (belimumab) failed to meet its secondary endpoint in a Phase III study. The drug did not achieve a statistically significant difference in response rates at 76 weeks in seropositive patients with systemic lupus erythematosus taking belimumab versus those receiving the placebo.

Eight hundred nineteen patients with serologically active lupus were enrolled in the BLISS-76 study, and were randomized to receive either a placebo or one or two doses of belimumab for 76 weeks. After 76 weeks, Human Genome Sciences announced that 38.5% of patients responded to treatment with a high dose of belimumab compared to 32.4% of patients taking placebo.

Human Genome's shares fell almost 10% following the results announcement. Executives from the company minimized the importance of the results, as the primary endpoint has already been met in other Phase III studies, along with several other secondary endpoints. Human Genome and GSK are still slated to submit regulatory applications for Benlysta in the US and Europe later this year.