The first member of a new class of osteoporosis drugs reduced spinal fractures by about two-thirds in post-menopausal women and in men undergoing hormone-deprivation therapy for prostate cancer, according to two studies released online Tuesday by the .
The drug, called denosumab, blocks production of cells called osteoclasts that break down bones, and physicians have high hopes for it because of its efficacy, ease of administration and apparent lack of severe side effects. But it's a biological agent rather than a chemical, meaning it's difficult to produce, and it is likely to be the highest-priced osteoporosis drug in an already-crowded marketplace.
The most well-known osteoporosis drug, Fosamax, is in a class known as bisphosphonates. Those drugs actually kill osteoclasts but carry the risk of stomach and esophageal irritation and have been linked to some cases of jaw necrosis.
Amgen, the manufacturer of denosumab, has not said how much the drug will cost, but analysts expect it to be at least $2,000 a year -- and potentially much higher -- and predict yearly sales of $2 billion to $3 billion.
Already, many insurance companies are pushing physicians to the generic version of Fosamax, alendronate, which costs about $100 a year.
Some medical experts think a high price would discourage the use of denosumab.
"If it is going to be quite a bit higher than the next-most-expensive drug, I don't see that it is going to be used so widely," said Dr. Frederick R. Singer, director of the endocrine/bone disease program at John Wayne Cancer Institute in Santa Monica, who was not involved in the research.
An advisory committee of the Food and Drug Administration will meet Thursday to consider Amgen's application for approval of the drug, to be called Prolia, for treating osteoporosis in women and in men being treated for prostate cancer. If approved, it would be the first drug specifically approved for treating such men.
As many as half of women and 30% of men will suffer an osteoporosis-related fracture during their lifetime, according to the International Osteoporosis Foundation. About a third of the 2 million American men with prostate cancer undergo hormone-deprivation therapy to prevent release of the hormones that fuel the tumors, which sharply increases their risk of osteoporosis.
The two new trials were designed and funded by Amgen, and most of the researchers were Amgen employees or recipients of funds from the company. Nonetheless, osteoporosis experts were impressed.
"From a scientific standpoint, these are outstanding publications," Singer said.
The first study included 7,686 women ages 60 to 90. Half were given an injection of denosumab every six months for three years, and half received a placebo. Overall, 2.3% of women receiving the drug had a spinal fracture and 0.7% had a hip fracture, compared with 7.2% and 1.2% in the placebo group.
That is similar to or slightly better than results with bisphosphonates, although the drugs have not been compared head to head.
The drug "does everything you would want a drug to do in women to prevent fractures," said Dr. John S. Adams, an orthopedic surgeon at UCLA's Geffen School of Medicine.
The second study involved 1,468 prostate cancer patients receiving hormone-deprivation therapy. They underwent the same protocol as the women. Overall, 1.5% of men receiving the drug had a spinal fracture, compared with 3.9% of those in the placebo group. Men receiving the drug also had a 5.6% increase in bone mineral density, while those receiving placebo had a 1% decline.
There was no decline in non-spinal fractures.
Many of the patients in both studies reported soreness at the injection site and transient bone pain similar to arthritis. The drug caused eczema, an inflammation of the epidermis, in a few patients, and about 12 of the women got a serious skin infection called cellulitis.
Some earlier, small studies showed an apparent small increase in tumors in treated patients, but that was not observed in either of the new studies. Such potentially severe side effects will be a focus of the FDA panel.
"This appears to be the most potent of the osteoporosis drugs," Singer said, "but it will require very careful monitoring to look for rare side effects," which did not show up for other drugs until large numbers of people took them.