A new osteoporosis treatment called Prolia (chemical name: denosumab) has been approved by the U.S. Food and Drug Administration (FDA). Prolia is approved to treat postmenopausal women diagnosed with osteoporosis who are at high risk of breaking a bone or who can't take or haven't gotten any benefits from other osteoporosis treatments.
Bone strength is a delicate balance between the body's work to build bone (to strengthen bones) and to break down bones (to help maintain normal calcium levels in the blood stream). The hormone estrogen plays an important role in this balance. When estrogen levels drop during and after menopause, this balance can be upset, which can lead to weaker bones over time.
Weakened bones can be seen on an x-ray and measured by a bone mineral density (BMD) test. When bones drop below a certain density level, osteoporosis is diagnosed. Osteoporosis increases the risk of breaking a bone either spontaneously or because of a fall.
Two other types of medicines are already used to reduce the risk of or treat osteoporosis: bisphosphonates and selective estrogen receptor modulators (SERMs).
Bisphosphonates used to prevent or treat osteoporosis include:
- Actonel (chemical name: risedronate)
- Boniva (chemical name: ibandronate)
- Fosamax (chemical name: alendronate)
- Reclast (chemical name: zoledronic acid)
Reclast is given intravenously once a year. The others are pills taken by mouth.
The SERM used to treat osteoporosis is Evista (chemical name: raloxifene). Evista also is used to reduce the risk of breast cancer in women diagnosed with osteoporosis.
Tamoxifen also is a SERM. Although tamoxifen can strengthen bones, tamoxifen generally is used only to reduce the risk of and treat breast cancer.
Prolia is a targeted therapy, which means it targets specific characteristics of cells. Some targeted therapies, including Prolia, are antibodies that work like the antibodies made naturally by your body's immune system. Prolia targets a protein called RANK ligand (RANKL). RANKL affects the activity of certain bone cells called osteoclasts. Osteoclasts help with normal bone breakdown activity to regulate calcium levels. Prolia blocks RANKL activity and limits osteoclast activity. So Prolia treats osteoporosis by restoring a healthier balance of bone building and bone breakdown.
Prolia is given as an injection under the skin once every 6 months. A twice-per-year treatment schedule may make Prolia more attractive to some women compared to other osteoporosis treatments. Possible side effects of Prolia include back, arm, and leg pain; high cholesterol levels; and urinary infections. More serious but much less common side effects include low blood calcium levels, rashes, and severe infections. Like bisphosphonates, in rare cases Prolia can cause breakdown of the jaw bone (called osteonecrosis of the jaw). Because of these risks, the FDA requires that anyone considering taking Prolia be carefully evaluated and educated to make sure that Prolia is used appropriately.
The FDA also is considering approving Prolia to reduce the risk of broken bones and bone pain in people diagnosed with cancer (including breast cancer) that has spread (metastasized) to the bones. Osteoclasts tend to be overactive when cancer spreads to the bones. Overactive osteoclasts can cause bone pain and increase the risk of breaking a bone. Prolia can lower the activity level of these overactive osteoclasts and reduce the risk of pain and other bone complications.