MONDAY, Oct. 18, 2004 (HealthDayNews) -- An experimental drug injected twice a year may prevent bone loss in postmenopausal women with low bone density, claims a new study funded by the drug's maker.

The injectable treatment, called AMG 162, works by suppressing the activity of osteoclasts, the cells involved in absorbing and removing old bone so that new bone tissue can take its place.

Osteoporosis sufferers have a high rate of bone turnover due to the hyperactivity of osteoclasts, a common occurrence after menopause, said study author Dr. Stanley B. Cohen. "It eats away at bone like a little Pac Man," he explained.

But in the study, patients who got injections of AMG 162 had detectable improvements in bone mineral density compared with women taking the osteoporosis drug alendronate.

In a separate study, an international team of investigators has found that strontium ranelate, a long-shelved oral medication that recently has sparked new interest, may reduce fractures in older women with osteoporosis.

Both therapies, if approved for use in the United States, could provide new treatment options for the 18 million Americans who suffer from either osteoporosis or low bone density, and the 2 million who have rheumatoid arthritis, a condition that can lead to bone erosion, the researchers said.

The researchers were to present their respective studies Oct. 19 at the American College of Rheumatology's annual meeting in San Antonio.

Eight million women and 2 million men in the United States have osteoporosis, a disease that weakens bones and makes them susceptible to fractures, according to the National Institutes of Health (NIH). Another 18 million people have low bone mass, putting them at heightened risk for the disease.

Normally, the tissues that form bone are constantly being created and resorbed by the body. In adolescence and early adulthood, there is significantly greater new bone formation, compared with bone resorption. But as people age, more bone is lost than can be replaced.

Women can lose up to 20 percent of their bone mass in the five to seven years following menopause, making them more susceptible to the disease, according to the NIH.

Although there's no cure for osteoporosis, the U.S. Food and Drug Administration has approved a number of medications to prevent or treat it in postmenopausal women. Therapies such as strontium ranelate and AMG 162 -- made by California-based Amgen -- may expand the arsenal of available treatments.

Cohen, a clinical associate professor at the University of Texas Southwestern Medical School in Dallas, led the study examining the effectiveness of different doses of AMG 162 given over a 12-month period. A total of 411 women, whose average age was 63, participated in the ongoing study. Eight groups of women randomly received injections of AMG 162 at 6-, 14- or 30-milligram doses every three months; 14 got 60, 100 or 210 milligrams every six months, or a placebo. A ninth group received 70 milligrams of oral alendronate once weekly.

Urine and blood tests were performed and X-rays were taken to evaluate the results. Overall, AMG 162 was well-tolerated and caused a rapid, dose-dependent increase in bone formation and bone density.

For example, when given every six months, the drug increased total hip bone mineral density by up to 4 percent, compared with a placebo, after 12 months. Bone mineral density of the lower spine increased by 4 percent to 7 percent across all dose amounts and intervals, similar to the 5 percent increase for the alendronate group after 12 months of treatment, Cohen said.

"We did not look at fracture risk, so that's the next big hurdle," he noted. But if ongoing studies show continued benefits and a reduction in fractures, he believes the twice-a-year injectable therapy could result in a dramatic improvement in patients complying with their recommended drug regimens.

At the same meeting, researchers were to present results of safety and effectiveness testing of strontium ranelate in women with low bone density. One set of tests, involving 1,650 women whose average age was 69, focused on the potential to reduce spine fractures. Other tests looked at non-spinal fractures in more than 5,000 women whose average age was 76.

Both studies showed significant reductions in fracture risk. Over three years, 36 percent of women aged 74 and older suffered hip fractures. But spinal and non-spinal fractures fell 32 percent and 31 percent, respectively, among women 80 and older taking the drug, the researchers said.

"Strontium ranelate is the first compound to simultaneously decrease bone resorption and stimulate bone formation," co-investigator Dr. Jean Yves Reginster, director of the World Health Organization Collaborating Center for Public Health Aspects of Rheumatic Diseases, said in a prepared statement.

"Given this and its outstanding safety profile, strontium ranelate could prove to be a first-line treatment option for women with low bone density with or without prevalent fractures as well as for elderly women with increased risk factors of hip fractures," he said.

The evidence in favor of strontium ranelate appears to be building. A study published in January in the New England Journal of Medicine showed the drug decreases the risk of vertebrae fractures in women with osteoporosis. The study was supported by Servier, the French pharmaceutical company that developed the drug.

More information

To learn more about osteoporosis, visit the National Osteoporosis Foundation.

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