Amgen shares havesoared after the firm presented impressive late-stage data which shows that thejewel in its portfolio, denosumab significantly improved bone metastasis-freesurvival in men with prostate cancer compared to placebo.

The US biotech has unveiled top-line results from a Phase III trialevaluating Xgeva (denosumab) versus placebo in 1,432 men withcastrate-resistant prostate cancer (CRPC). The study showed that the drug significantlyimproved median bone metastasis-free survival by 4.2 months compared to placebo(the primary endpoint), and significantly improved time to first occurrence ofbone metastases. Overall survival was similar between both arms.

Overall rates of adverse events and serious adverse events weregenerally similar between Xgeva and placebo, although hypocalcaemia andosteonecrosis of the jaw was observed at increased frequencies in the formerarm. 

Roger Perlmutter, head of R&D at Amgen, said the data demonstratethat Xgeva, a fully human monoclonalantibody designed to target RANK ligand, limits the ability oftumours to colonise bone, “an important finding for men at risk for bonemetastases and their healthcare providers”. He added that “these landmark data”will be presented at an upcoming medical conference.

Analysts have reacted excitedly and Joshua Schimmer at Leerink & Co,said it was a positive result “for astudy we did not think would succeed”. However he noted, as did other analysts,that the study did not show overall survival benefit, and Xgeva may have to demonstratesome other clear indication of benefit, such as time to skeletal-relatedevents, if it is to get approval.

However, Baird &Co analyst Christopher Raymond argued that any focus on the lack of an overallsurvival benefit “misses the point that this drug will be used immediately inthe CRPC setting as a preventive agent, and ignores tangible confoundingfactors that we think adequately explain this artifact”. Eric Schmidt at Cowen& Co was also impressed, claiming that approval in this indication and forbreast cancer (trials began in June) could boost US sales of denosumab by asmuch as $4 billion a year,

Last month, the US Food andDrug Administration approved Xgeva for the prevention of skeletal-relatedevents in patients with bone metastases from solid tumours, while denosumab, underthe brandname Prolia, was approved by the FDA in May for postmenopausal womenwith osteoporosis who are at high risk for fractures.