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By Denise Mann
Primary-care doctors now have a new—and potentially more convenient—tool to fight the bone disease osteoporosis.
On Tuesday the Food and Drug Administration (FDA) approved a new drug, Prolia (denosumab), to promote bone strength and prevent fractures in postmenopausal women with osteoporosis who are at high risk.
Women at high risk for fractures include those who have already suffered an osteoporosis-related fracture or who haven't had success with other osteoporosis treatments. Roughly half of all women over age 50 will experience an osteoporosis-related fracture in their lifetime, according to the National Institutes of Health.
Prolia, the first osteoporosis drug of its kind, works by blocking a type of cell that breaks down bone. Unlike most osteoporosis drugs, which come in a pill or are delivered through a skin patch, Prolia is injected by a doctor every six months.
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“It's always wonderful for clinicians and patients to have more options,” says Ethel Siris, MD, the director of the Osteoporosis Center at Columbia University Medical Center, in New York. “It's a very potent agent and it is pretty clear that the reduction in fracture risk is quite robust."
Dr. Siris was one of the researchers on a key study of nearly 8,000 postmenopausal women with osteoporosis that served as the basis for the FDA's approval.
During the three-year study—which was funded by the drug's manufacturer, Amgen—the women who took Prolia were less likely than a placebo group to experience spine, hip, and other bone fractures. Roughly 2% of the women in the Prolia group suffered a spine fracture, for instance, compared to about 7% in the placebo group. (Dr. Siris, the past president of the National Osteoporosis Foundation, has served on a paid advisory board for Amgen.)
Prolia isn't the first injectable osteoporosis drug. Two bisphosphonate medications, Reclast and Boniva, are delivered intravenously in a doctor's office. Two other drugs, Forteo and Miacalcin, require self-injections every day and every other day, respectively.
Prolia is a new type of injectable drug, however. It’s the first biologic medication to be approved for the treatment of postmenopausal osteoporosis. Biologics, which are genetically engineered versions of human proteins (rather than synthetic chemicals), are also used to treat conditions such as rheumatoid arthritis and psoriasis.
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Since there are no pills to remember to take, Prolia will help ensure that osteoporosis patients get their medication, and the new drug may prove easier to use than other injectable options, says Dr. Siris. Reclast, for instance, requires doctors to have an infusion chair in their office and requires a test for kidney problems before each dose. Neither of those is necessary with Prolia.
“The idea that I can, at the end of a visit, pull out a syringe, swab some alcohol on a patients’ deltoid muscle, and do it myself without a nurse is attractive to me,” she says.
Prolia will also be the first biologic sold directly to primary care physicians (other than vaccines).
“The other biologic agents used today in medicine are prescribed by specialists such as rheumatologists, endocrinologists, hematologists, and oncologists," says Nancy Lane, MD, the director of the Center for Healthy Aging at the University of California, Davis. "But for the most part [postmenopausal osteoporosis] is treated by primary care physicians. So this will be an injection in the physician’s office—like a flu shot."
It is not clear whether Prolia is stronger or more effective than existing osteoporosis drugs, Dr. Lane says.
In the clinical trials submitted to the FDA, the most commonly reported side effects were various types of pain (including back pain), high cholesterol levels, and urinary bladder infections. Rare but more serious side effects included decreased blood calcium levels, infections, the skin infection cellulitis, and eczema. Prolia may also contribute to a severe bone disease (osteonecrosis) that affects the jaw, the FDA noted.
The bone-weakening cells targeted by Prolia also play a role in immunity, so the drug "has the potential to affect multiple layers of the immune system," according to the FDA's Center for Drug Evaluation and Research.
"It is also not known whether it will be safe in patients who are taking other biologic agents, like those with rheumatoid arthritis," says Dr. Lane.
The FDA will require patients who are considering Prolia to receive a guide that explains the risks of the drug.