A third pivotal trial of Amgen's denosumab found that it delayed by 21 per cent the risk of fractures and other bone complications in men with advanced prostate cancer compared with current therapy.

Amgen filed last month for US Food and Drug Administration approval of the drug as a treatment for cancer patients. Earlier this week, the agency approved it, under the brand name Prolia, for use in post-menopausal women suffering from osteoporosis.

Denosumab, widely considered the most important growth driver in Amgen's development pipeline, is the first in a new class of drugs designed to inhibit proteins that activate bone-destroying cells.

Roy Baynes, head of hematology/oncology development at Amgen, said the latest trial results, to be presented here at a meeting of the American Society of Clinical Oncology, are "remarkably consistent" with previous trials in patients with advanced breast cancer, other solid tumors and multiple myeloma.

The 1,900-patient trial, which compared denosumab with Novartis AG's Zometa, showed that the Amgen drug significantly delayed by 3.6 months, or 21 percent, patients' first skeletal event, such as a fracture or the need for bone surgery.

There was no difference between the two groups in overall survival or the amount of time patients lived without their cancer getting worse.

Baynes said the rates of adverse events, including infections, were similar between the two treatment groups, but the incidence of low blood calcium levels was more frequent in the denosumab arm.

Osteonecrosis of the jaw -- death of jaw bone tissue -- was seen in 22 patients receiving denosumab, compared with 12 patients receiving Zometa. Baynes said encouraging information about those patients will be detailed at the oral presentation of the study here on Sunday.

Amgen expects to announce in the second half of this year results from a pivotal trial looking at whether use of denosumab in patients with earlier-stage prostate cancer can prevent the disease from spreading to the bones.

"We believe we have a molecule that has a very favorable profile," Baynes said.

The consensus analyst forecast is for denosumab to reach about $3.3 billion in sales in 2014, according to Thomson Reuters data. – Reuters