Human Genome Sciences and partner GlaxoSmithKline have presented more promising late-stage data on the lupus drug Benlysta, which the firms believe represents a major breakthrough in the difficult-to-treat disease.

The companies say that Benlysta (belimumab) formerly known as LymphoStat-B, met the primary endpoint in BLISS-52, the first of two Phase III trials in patients with systemic lupus erythematosus (SLE). The 865-patient year-long study showed that “a clinically and statistically significant improvement” was shown in patient response rate for belimumab plus standard of care, versus placebo plus standard of care (57.6% for 10 mg/kg Benlysta, 51.7% for 1 mg/kg Benlysta) and 43.6% for placebo).

Belimumab is the first in a new class of drugs called BLyS-specific inhibitors and the firms noted that no new drug for lupus has been approved by regulatory authorities in more than 50 years. Carlo Russo, senior vice president of biopharm development at GSK, said that Benlysta is “the first medicine being developed specifically for lupus that has reached this late stage of clinical development with positive results”.

The second of two Phase III trials, BLISS-76, is due to be reported by the end of the year. If everything goes well, HGS and GSK will file for approval in the USA, Europe and other regions in the first half of 2010.

It is estimated that 1.5 million people in the USA, and five million worldwide, suffer from various forms of lupus, including SLE.