Human Genome Sciences and GlaxoSmithKline are celebrating the news that the US Food and Drug Administration has given the green light to Benlysta, making it the first new treatment to be approved for lupus in 56 years.

The agency has approved Benlysta (belimumab) for the treatment of adults with active, autoantibody-positive systemic lupus erythematosus who are receiving standard therapy, including corticosteroids, antimalarials, immunosuppressives and nonsteroidal anti-inflammatory drugs. The thumbs-up was widely anticipated given that the FDA's Arthritis Advisory Committee voted 13 to 2 to recommend approval in November.

However in December, the Prescription Drug User Fee Act target date for a priority review of Benlysta was put back, with a request of additional information and the approval comes with conditions.

The FDA noted that African American patients and those of African heritage participating in the two studies involving 1,684 lupus sufferers that made up the filing did not appear to respond to treatment with Benlysta. The studies "lacked sufficient numbers to establish a definite conclusion", said the agency, so to address this concern, HGS has agreed to conduct an additional study of people with those backgrounds.

Also the regulator noted that those receiving Benlysta during clinical studies reported more deaths and serious infections compared with placebo. The drug should not be administered with live vaccines and the manufacturer is required to provide a medication guide to inform patients of the risks associated with the treatment.

Benlysta is delivered directly into a vein and is the first inhibitor designed to target B-lymphocyte stimulator (BLyS) protein, which may reduce the number of abnormal B cells thought to be a problem in lupus. The signifcance of the approval is clear, given that the FDA last approved drugs to treat lupus, Plaquenil (hydroxychloroquine) and corticosteroids, in 1955; aspirin was approved to treat the potentially fatal, autoimmune disease that attacks healthy tissues in 1948.

HGS and co-marketing partner GSK are unsurprisingly delighted as are patient associations. Sandra Raymond, head of the Lupus Foundation of America, said the approval "marks the beginning of a new era of improved diagnosis, prevention, and treatment for the disease", and she hopes the decision "will further stimulate additional companies to invest in new therapies for lupus".

Analysts are pretty unanimous that Benlysta is going to be a blockbuster  and HGS is highly likely to attract attention from bigger players looking at acquisitions, with GSK seemingly the most likely candidate.