A new US study suggests that the osteoporosis drug Forteo (made by Eli Lilly) was more effective than Fosamax (made by Merck) at increasing bone density in arthritis patients with osteoporosis caused by taking corticosteroids such as prednisone.

The study is the work of Dr Kenneth Saag, a professor in the Division of Clinical Immunology and Rheumatology at the University of Alabama at Birmingham (UAB) and colleagues, and is published in the 15th November issue of the New England Journal of Medicine.

The study showed that patients taking Forteo (teriparatide), a parathyroid hormone, more than doubled their bone density and significantly reduced their risk of new spinal fractures compared to those who took Fosamax (alendronate).

A great number of arthritis and other patients use prednisone and other glucocorticoids to lessen inflammation and reduce swelling in tissue and joints. However there is a downside to the drugs, the possibility of bone loss and osteoporosis, a bone disease that results in bones becoming fragile and prone to fracture.

Saag said that patients with arthritis need to be on medication for their condition, but it is also important that they reduce the risk of hip fracture or spinal compression from taking their medication, thus “patients and their doctors need more bone-building options,” he said.

“This study significantly improves our understanding of treatment options for secondary osteoporosis, which is osteoporosis caused by taking glucocorticoid drugs like prednisone,” explained Saag.

Current international guidelines recommend the class of drugs that includes Fosamax, called bisphosphonates, for the treatment of glucocorticoid-induced osteoporosis, but according to Saag, many doctors are hoping Forteo is part of the “new wave” of drugs to treat the condition, and there was insufficient evidence of how it compared to the currently recommended ones.

In the 18-month, randomized, double-blind trial, Saag and colleagues recruited 428 men and women with osteoporosis who were aged between 22 and 89 years to take either Forteo or Fosamax. All the participants had been taking glucocorticoids for at least 3 months, at a daily minimum dose of 5 mg of prednisone or its equivalent.

Once a day, 214 patients took 20 micrograms of Forteo (by injection) and 214 patients took 10 mg of Fosamax (oral pill). The researchers measured changes in bone mineral density of the lower lumbar spine and total hip, and also examined markers of bone turnover, the time it took for changes in density to occur, the number of breaks and also measures of safety.

Bone density was measured in the spine and hips using DEXA scans, a low-level X-ray that shows small changes in bone density.

The results showed that:

  • The final set of measurements showed that the lumbar spine mean bone mineral density had increased more in the Forteo patients than the Fosamax patients.
  • The increase was 7.2 plus or minus 0.7 per cent for Forteo and 3.4 plus or minus 0.7 per cent for Fosamax.
  • The figures showed there was a significant difference between the groups by the 6 month mark.
  • At the 12 month mark, total hip bone mineral density had also increased more in the Forteo group.
  • The Forteo group also had fewer new vertebral fractures (0.6 per cent versus 6.1 per cent).
  • The rate of nonvertebral fractures was similar in both groups (5.6 per cent versus 3.7 per cent).
  • Forteo also increased calcium levels in more patients compared to Fosamax.
  • There was a significantly higher number of patients in the Forteo group with at least one elevated measure of serum calcium.

Saag and colleagues concluded that:

“Among patients with osteoporosis who were at high risk for fracture, bone mineral density increased more in patients receiving teriparatide [Forteo] than in those receiving alendronate [Fosamax]”.

In terms of side effects, the differences between the two drugs was insignificant said the researchers.

Explaining the effect of Forteo, the researchers suggested that because it was a parathyroid hormone, it stimulated the growth of bone-forming cells called osteoblasts, effectively counteracting the bone diminishing effect of glucocorticoids, whereas Fosamax works through a different cell pathway, with a lower impact on bone regeneration.

Eli Lilly is waiting for the US Food and Drug Administration (FDA) to add Forteo to the list of drugs approved for use in patients with glucocorticoid-induced osteoporosis.

At present, Forteo is only FDA approved for treating women with postmenopausal osteoporosis, or men with primary osteoporosis or hormone-related osteoporosis.

The study was funded by Eli Lilly, while Saag is a consultant to both Eli Lilly and Merck.

“Teriparatide or Alendronate in Glucocorticoid-Induced Osteoporosis.”
Saag, Kenneth G., Shane, Elizabeth, Boonen, Steven, Marin, Fernando, Donley, David W., Taylor, Kathleen A., Dalsky, Gail P., Marcus, Robert.
N Engl J Med 2007 357: 2028-2039.
Volume 357:2028-2039, November 15, 2007, Number 20

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Written by: Catharine Paddock