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New Class of Osteoporosis Drugs Rebuilds Bone
Geriatric Times September/October 2001 Vol. II Issue 5
Medications currently available for osteoporosis, such as estrogens and bisphosphonates, can help prevent its onset and slow its progress, but they increase bone density only slightly over many years. A new class of drugs on the horizon may actually increase new bone formation and bone mass much more quickly and effectively.
These new drugs are based on parathyroid hormone (PTH), the hormone secreted by the parathyroid gland in the neck that regulates blood calcium levels. When the active component of PTH, called 1-34 (Forteo), is given in a daily injection, it alters the signals given to osteoblasts, which build bone, and osteoclasts, which break bone down. The result is substantially increased bone formation compared to other osteoporosis treatments.
In a study published in the May 10 issue of the New England Journal of Medicine, 1,637 women with osteoporosis and prior vertebral fractures were treated with 1-34 in 20 µg and 40 µg doses over approximately 21 months. Women who received either dosage of 1-34 had a 65% and 69% reduced risk of one or more new vertebral fractures, and a 35% and 40% reduction in nonvertebral fractures, respectively, compared to those who received placebo. Protective effects of 1-34 were apparent after nine to 12 months of treatment. Women receiving 1-34 also experienced significantly less back pain, as well as 9% and 13% respective gains in bone mineral density of the spine, hip and total body, compared to placebo.
Side effects included nausea and headache and were primarily associated with the higher dosage. At least one incidence of mild hypercalcemia (high blood calcium levels) was reported upon injection in 28% of those in the 40 µg 1-34 group and 11% of those in the 20 µg group, compared to 2% in the placebo group. Manufacturer Eli Lilly and Co. stopped the study early to evaluate the finding that long-term exposure to high doses of PTH produced osteosarcomas in rats. Osteosarcoma is rare in adult humans, however, and no cases were found in women in this study.
Parathyroid hormone has also been shown effective in combination with estrogens to treat postmenopausal osteoporosis. Women receiving hormone therapy alone typically experience about a 6% total increase in bone mass. But in a two-year, randomized, placebo-controlled trial of 58 women, those receiving PTH in addition to estrogen showed a striking 30% increase in the density of their vertebrae. In a separate randomized study of 52 women, these benefits were maintained for one year after the women discontinued PTH and continued hormone replacement therapy.
The U.S. Food and Drug Administration is expected to review 1-34 for approval this summer--JH
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