Adverse effects were largely similar between treatment groups in both studies, though the male patients showed slightly higher rates (34.6 percent versus 30.6 percent for serious events and 5.9 percent versus 4.6 percent for serious events related to infections). But notably absent from the list of adverse events was osteonecrosis of the jaw, a rare but worrisome side effect of bisphosphonate drugs.
Although the data do not rule out the possibility that osteonecrosis could occur with denosumab, it was encouraging to see no cases thus far, Cummings suggested. He said follow-up of FREEDOM participants would continue for 10 years, which may provide a more definitive view of the risk.
Denosumab's manufacturer, Amgen, has not yet announced the pricing for the drug. Nevertheless, as a biologic drug, denosumab is widely expected to be relatively expensive.
But another academic specialist contacted by MedPage Today and ABC News suggested a higher price could be acceptable given denosumab's potential advantages.
Endocrinologist Dr. Roberto Pacifici of Emory University in Atlanta said the "number needed to treat" in preventing fractures has been low in the denosumab studies reported to date.
"Therefore the cost of the drug is likely to be [worthwhile] in many patients," he said. "Guidelines will have to be developed in order to use this agent in the most cost-effective way."
Cummings said that if the drug is approved, he would consider it primarily for patients with a poor history on bisphosphonates.
"Those who have had trouble with oral drugs," because of side effects or compliance problems, would be the main candidates for denosumab, he said.
Another point in denosumab's favor, Cummings said, is that it is less persistent in bone than many bisphosphonates, making its activity potentially reversible — an important point for patients experiencing adverse effects.
In addition, Dr. Khosla pointed out, "since bisphosphonates are cleared by the kidney and contraindicated in patients with renal insufficiency, denosumab (which is cleared by nonrenal metabolism) may prove to be a safe drug in these patients, although studies that directly address this issue need to be done."
Amgen filed last December for FDA approval of the agent for treatment and prevention of postmenopausal osteoporosis in women and treatment and prevention of bone loss in patients undergoing hormone ablation therapy for either prostate or breast cancer. The two trials were funded by Amgen.
This article was developed in collaboration with ABC News.