By Deena Beasley
LOS ANGELES (Reuters) - A clinical trial of Amgen Inc's bone drug, Xgeva, found that it can significantly delay the time it takes for prostate cancer to cause bone pain -- a finding the company believes will help boost the drug's market potential.
Amgen said in December that monthly injections of Xgeva, also known as denosumab, added 4.2 months, compared with placebo injections, to the length of time patients lived without their cancer spreading.
But the trial did not demonstrate a survival advantage (it was not designed to do so) and investors have been eager to see the full safety results.
"We saw a 33 percent reduction in the risk of developing symptoms of bone metastases, mainly pain" said Roy Baynes, Amgen's vice president of global development.
Amgen also reported on Tuesday at a meeting of the American Urological Association that a cumulative 4.6 percent of denosumab patients were diagnosed with osteonecrosis of the jaw, or death of jawbone tissue.
Baynes said the rates of ONJ seen in the trial -- 1.1 percent at year one, 2.9 percent at year two and 4.2 percent at year three -- were consistent with those seen in earlier trials of the drug in patients with advanced cancer.
"ONJ is generally readily manageable," he said.
Baynes also said the rates of new malignancies were similar in both arms of the trial. Treatment with denosumab was associated with a higher risk of hypocalcemia, or too little calcium in the blood.
The Xgeva trial involved 1,432 men with prostate cancer who had stopped responding to hormone therapy.
A separate pivotal trial presented at the urological meeting showed that denosumab significantly delayed worsening of pain in prostate cancer patients compared with Novartis AG's Zometa.
Analysts, on average, have forecast annual denosumab sales of $2.5 billion by 2015, according to Thomson Pharma.
The drug is currently approved as a treatment for reducing fractures and other bone problems in certain cancer patients. It is also sold under the brand name Prolia as a treatment for osteoporosis.
(Editing by Steve Orlofsky)