May 10, 2001 (HealthScout) -- A new era of osteoporosis treatment, based on a parathyroid hormone derivative that promotes bone growth, is on the horizon, researchers say.
Osteoporosis affects an estimated 10 million Americans, mostly postmenopausal women, whose bones are weakened by a lack of the hormone estrogen, which is chiefly produced by the ovaries. The disease makes people vulnerable to crippling, even life-threatening fractures.
While osteoporosis treatment today relies mostly on medications to prevent bone loss, the new drug acts on bone cells called osteoblasts to increase the rate of bone formation. Given by injection, the drug is derived from a hormone produced by the parathyroid glands, located in the neck.
"Our company supplied all the data to the Food and Drug Administration (FDA) last year, and we expect a decision by the end of this year," says Dr. Bruce H. Mitlak, global medical director for Eli Lilly, Inc., which plans to market the medication as Forteo. "If the decision is favorable, it could be available as early as the end of this year."
Mitlak led a Lilly-sponsored international study of the parathyroid hormone (PTH) treatment for 1,637 postmenopausal women with osteoporosis. All had fractured bones in the spinal column. Some got daily injections of PTH; others received placebo treatments.
PTH reduced the incidence of new vertebral fractures more than 65 percent, compared with those getting placebo treatment, a greater reduction than achieved by existing medications, says a report in the May 10 New England Journal of Medicine.
"We think this really establishes the value of a drug that stimulates bone formation," says Mitlak. "It translates to a two-thirds reduction of vertebral fractures, and an analysis shows a greater reduction in the more severe kinds of deforming fractures."
If approved by the FDA, the drug's use will be limited to about 30 percent of osteoporosis patients, says Dr. Felicia Cosman, associate professor of clinical medicine at Columbia University in New York City and medical director of the National Osteoporosis Foundation.
"It's going to be used for people with severe osteoporosis, for people who have more severe bone loss or who have had fractures despite standard therapy," Cosman says.
PTH may be given either alone, or with another drug to prevent bone loss, for no more than two years, partly because there is no information about the long-term effects of PTH use and because "you don't get as much of an increase in bone mass after one or two years," Cosman says. "You get the biggest bang for the buck in the first year."
The need to take daily injections of PTH also limits the recommended length of therapy, she says.
The Lilly-funded PTH study was interrupted briefly near the end of 1998 when laboratory studies found that rats given high doses of the hormone for two years developed bone cancer. Intensive study of the laboratory data "led us to the conclusion that the finding in animals did not pose a risk for human patients," Mitlak says. There is no increased incidence of bone cancer in persons with hyperparathyroidism, overproduction of PTH, and none of the women in the PTH osteoporosis study developed bone cancer during a 21-month follow-up period, the researchers say.
The Lilly product uses only part of the parathyroid hormone molecule, the segment that is biologically most important, Mitlak says. Another form of PTH is now in other osteoporosis studies sponsored by the National Institutes of Health, Cosman says.
What To Do
Appropriate patients with severe osteoporosis must await FDA approval of PTH before seeking the treatment.
For a rundown on osteoporosis and its treatment, try the International Osteoporosis Foundation or the National Institutes of Health.
