A shot to fight osteoporosis
Bone loss can be insidious, going unnoticed in millions of people -- most of them women -- until spinal damage becomes severe or until a hip fracture starts a spiraling physical decline.
Drugs can fight the often-debilitating condition, known as osteoporosis, but they can cause unpleasant side effects. As a result, many people stop taking them, leaving their bones to become ever more brittle and more likely to break.
An experimental treatment called AMG-162 seems to cause fewer side effects than traditional medications and -- possibly even more promising -- would need to be injected only once every six months. “This could be a very appealing approach for people who can’t tolerate the current treatments, and it may be more convenient to use,” says Dr. Felicia Cosman, an endocrinologist and clinical director of the National Osteoporosis Foundation.
More than 10 million Americans have osteoporosis, a disease that strikes four times as many women as men, and an additional 34 million are estimated to have low bone mass, which increases the risk for developing the disease.
The condition occurs when bone’s natural regeneration process is upset, usually as part of the natural aging process, causing existing bone cells to break down more quickly than new tissue can be created. In postmenopausal women, the rate difference is especially pronounced. The most widely prescribed treatments, such as Fosamax (alendronate), slow bone loss by dampening the effects of osteoclasts, the cells that spark bone destruction. But the drugs require a complicated dosing regimen to be effective. They must be taken every day or once a week, they can’t be combined with food or beverages, which weaken their potency, and they can cause nausea, cramping and stomach upsets.
Because of these difficulties, research indicates, more than half of the people who get a prescription for these medications stop taking them within a year.
“All these factors conspire to undermine compliance -- and even under ideal conditions, these drugs aren’t well absorbed,” says Dr. Michael McClung, director of the Oregon Osteoporosis Center in Portland who has tested AMG-162.
In contrast, the experimental drug needs only be injected twice yearly to have the same effect. The drug is composed of an antibody that cripples the protein responsible for the formation, activation and survival of osteoclasts.
“It doesn’t stop bone turnover completely, but it does put on the brakes and keeps the bone loss process in check,” says Dr. David L. Lacey, a scientist at Amgen Inc. in Thousand Oaks who helped devise this medication.
In a 2004 study, 411 women with osteoporosis were divided into nine groups; eight groups were injected with various doses of AMG-162 or a placebo (dummy shot) over 12 months while one group received weekly doses of alendronate. Test results indicated that the antibody circulated in the blood stream and slowly degraded so the medication’s effects lasted for at least six months.
And it seemed to curb bone loss: Volunteers experienced increases in bone mineral density that were comparable to alendronate. Further, the injectable drug didn’t cause any more stomach upsets than the placebo.
The medication is now in the midst of large-scale tests.
“Although drugs like Fosamax are the mainstays of current osteoporosis therapy, there are problems with them,” says Cosman. “It would be great to have another potent drug that is better tolerated to pick up the slack.”
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New ways to save bones
Osteoporosis sufferers may soon have several treatment options. A new pill called Boniva, similar to Fosamax and received government approval earlier this year, is the first once-a-month treatment to inhibit bone loss. An injectable version of Boniva, which could last for three months, is under development.
Also in the research pipeline is Protos, which dampens the effects of bone-destroying osteoclasts and spurs the production of bone-building osteoblasts. It could become the first medication to increase formation of new strong bone while reducing bone loss.
