Any remaining bears on Human Genome Sciences and GlaxoSmithKline’s chances of getting approval for their treatment for lupus, Benlysta, could be facing a lonely time after the drug sailed through a phase III trial in patients with serologically active systemic lupus erythematosus, showing a significant reduction in symptoms and the need for patients to use steroids. But while investors may be jumping on the bandwagon, sending HGS shares up three-fold in morning trading to $9.66, it should be remembered that the drug still has to pass its final test in the form of the 76-week, Bliss-76, data expected in November, and that HGS has disappointed in the past.

What people seem to be taking a punt on at the moment, however, is the sheer size of opportunity for Benlysta. As frequently trotted out, there has been no new approved treatment for Lupus in the last 50 years (Therapeutic Focus - Lupus needs shots on goal to hit the mark, June 12, 2009). With one potentially on the horizon, analysts and investors are gleefully rubbing their hands together in anticipation of sales. Citigroup are conservatively estimating that if the drug is priced at a similar level to other antibody therapies, approximately $15,000 a year, and mops up 50% of the market, peak US sales could hit $1.4bn, with worldwide sales increasing to $2.5bn, potentially adding 3% to Glaxo’s 2014 earnings per share.