FDA Approves First Drug to Build Bone

[WASHINGTON, DC] - A new drug approved by the Food and Drug Administration is the first to combat osteoporosis, the brittle-bone disease, by causing the body to form new, healthy bone tissue.

Approved Tuesday, the drug works by stimulating osteoblasts, the body's bone-building cells, which often are inactive among the 10 million Americans with osteoporosis. Active osteoblasts increase bone density and its resistance to fractures.

The chemical name of the new drug is teriparatide. It will be marketed by Eli Lilly and Co. of Indianapolis under the brand name Forteo.

FDA officials said the drug, given by injection daily, will carry a special warning because in laboratory tests teriparatide caused cancerous bone tumors in rats. Such tumors have not been seen in 2,000 people who tested the drug in clinical trials, officials said.

"We feel this is an important drug," said Dr. Eric Colman, a team leader in the FDA division of metabolic and endocrine drug products. "It is the first approved that stimulates bone formation instead of slowing the breakdown of bone."

As people age, their risk for osteoporosis increases. Over a person's lifetime, bone is built up and broken down by special cells. The osteoblast cell forms new bone, while osteoclast dissolves old, worn-out bone tissue. So long as this process remains in balance, bones stay strong and dense.

But in many women after menopause and in some men, age brings an imbalance of action by the two bone-sculpting cells. Osteoclasts tend to become more active, dissolving old bone faster than osteoblasts can build new bone. The result is that bones become thin and brittle, leading to fractures, particularly of the spine.

Since 1995, drugs like Fosamax have attacked this problem by slowing the action of osteoclasts, thus helping bones retain density.

The new drug takes a different approach by stimulating the osteoblasts and restoring the body's ability to build new bone.

Colman said that to bolster the effect, patients may use teriparatide with the older approved drugs because the drugs work by different mechanisms in the body.

Labels and instructions issued with teriparatide will carry a "black box" warning, a device used by the FDA to highlight special concerns about a drug.

Colman said the warning will discuss rat studies that showed some animals injected with teriparatide developed osteosarcomas, a rare and serious cancer of the bone. However, he said that teriparatide was testing for 19 months in 1,637 women and for 10 months in 437 men. None of those patients developed bone cancer.

In the test patients there were significant increases in bone density at the spine and hip when compared with patients who took only calcium pills and vitamin D. The studies also found in women a reduction in bone fractures among patients taking teriparatide when compared to a placebo. The effect on fracture risk in men was not studied, according to an FDA statement.

The FDA said that in teriparatide clinical trials some patients developed mild side effects, including nausea, dizziness and leg cramps.

Robert Marcus, a medical adviser for Lilly, said the cancer that occurred in the rats would be highly unlikely in humans for several reasons, including that rat skeletons are significantly different from human skeletons.

To lower the risk of cancer, Marcus said, Lilly is recommending the drug not be prescribed for patients with an increased risk of osteosarcoma, including those with Paget's disease or unexplained elevations of alkaline phosphate. Also, he said, children, growing adults and those who have had radiation therapy involving the skeleton should not receive the drug.

Osteoporosis affects around 10 million Americans, 80 percent of them women. Brittle bones can lead to small fractures of the vertebrae and a gradual slumping, leading to the distinctive hump frequently seen in elderly women and in some men. The fractures can also cause pain and crippling.