Human Genome Sciences and GlaxoSmithKline have presented more promising data on Benlysta late-stage data which the companies hope will be the first treatment to receive approval for lupus in over 50 years.

They have revealed this morning that Benlysta (belimumab) formerly known as LymphoStat-B, met the primary endpoint in BLISS-76, the second of two Phase III trials in patients with systemic lupus erythematosus (SLE). The 819-patient study showed that a statistically significant improvement was shown in patient response rate for belimumab plus standard of care, versus placebo plus standard of care (43.2% for 10 mg/kg Benlysta, 40.6% for 1 mg/kg Benlysta) and 33.8% for placebo).

The drug also met “prespecified major secondary efficacy endpoints”. For example, 46.9% and 42.8% of patients taking Benlysta 10mg/kg and 1mg/kg respectively, experienced an improvement in symptoms as measured by the Selena Sledai scale, compared with 35.6% of patients on standard of care, plus placebo. Belimumab, the first in a new class of drugs called BLyS-specific inhibitors, was generally well-tolerated, with rates of overall adverse events and infections being comparable between treatment groups.

David Stump, executive vice president of R&D at HGS, said the firms will present the full results from BLISS-76 “at an appropriate scientific meeting, hopefully in the first half of 2010”. It has 24 weeks more to run and follows the presentation in July of positive data from BLISS-52.

Joan Merrill, a study investigator from the University of Oklahoma Health Sciences Center, said “the lupus community has waited for decades for one positive Phase III trial of an investigative drug developed for lupus. Now we have two. Based on the data we now have in hand, we have cause for hope that belimumab may emerge as a significant new treatment”. Her enthusiasm was echoed by Sandra Raymond, chief executive of the Lupus Foundation of America, who said that conducting clinical trials in lupus “has been extremely difficult due to many factors including the heterogeneity of the disease, the selection of appropriate clinical trial endpoints, and the confounding role of required background medications given to clinical trial participants”.

She added that HGS and GSK “have proven that these barriers, while formidable, can be overcome”. The companies will now submit marketing applications in the USA, Europe and other regions during the first half of 2010.

Analysts believe that Benlysta could be worth as much as $3 billion a year, and it is highly likely that HGS shares will soar later today once the market opens across the Atlantic. The companies will share equally in Phase III/IV development costs, sales and marketing expenses, and then profits.