STUDY: What to do about our aging bones? More Info

JOURNAL: The New England Journal of Medicine

AUTHORS: Dennis Black

ABSTRACT: Combining an experimental calcium-controlling hormone that builds bone with a popular osteoporosis drug does not increase bone density any more than the hormone alone.

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COMMENTARY: The interim results come from a one-year study, sponsored by the National Institutes of Health, in 238 post-menopausal women.

Some received only Preos, a bioengineered full-length version of human parathyroid hormone, some only Fosamax, an osteoporosis drug sold by Merck & Co., while others were treated with both drugs.

Bone mineral density at the spine increased in all the treatment groups, but was highest, at a rate of 6.3 percent, in the parathyroid hormone group. The volume of spongy bone at the center of the spine also increased, but the 24 percent increase in the parathyroid hormone group was about twice that found in either of the other groups.



Increased bone density at the hip was highest with Fosamax, but the volume of bone was actually higher with Preos.



For previously untreated patients, the data now suggest that if therapy with parathyroid hormone is contemplated, it should be used alone

An aging U.S. population is becoming more susceptible to bone-thinning osteoporosis, which affects 8 million women and 2 million men and causes more than 1.5 million fractures a year.

Preos, under development by NPS Pharmaceuticals Inc., is part of a new class of injected osteoporosis drugs that build bone rather than simply prevent bone loss as patients age.

Older drugs like Fosamax are part of a class called biphosphonates that work by stopping or slowing bone loss.

Earlier research had suggested that dual use of the drugs might improve outcomes since they have different mechanisms of action.

Parathyroid hormone-induced increases in bone size are perhaps more important in terms of mechanical strength, and the addition of Fosamax to the regimen impairs the ability of the hormone to induce these changes.



In the study's second year, patients on Preos will discontinue injections, and will be given either Fosamax or a placebo to see if bone gains are maintained.

If the bone-building effects of Preos are shown to continue even after a patient stops the therapy, it would make sense to treat more moderately affected osteoporosis patients.

The company expects in November to have results from a study in rats of whether Preos raises the risk of bone cancer. Forteo carries a warning that rats developed bone cancer after taking high doses of the drug for most of their lives. Neither drug has been linked to tumors in humans.