THERE鈥橲 new hope for old bones: a bone-building drug about to be approved in the US not only stops bones wasting away, but actually reverses the process.
Old bone is constantly reabsorbed by cells called osteoclasts, while new bone is built up by osteoblasts. When more is lost than replaced, bones become fragile as the spaces inside them grow. Such bone wasting affects tens of millions of people worldwide, especially postmenopausal women, and half of all women will eventually suffer broken bones because of osteoporosis.
Most drugs for treating osteoporosis inhibit osteoclasts. But teriparatide, a synthetic version of parathyroid hormone made by Eli Lilly and marketed as Forteo, stimulates the bone-building osteoblasts. After trials involving 2800 men and women with osteoporosis, an FDA advisory committee unanimously recommended the drug for postmenopausal women.
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鈥淵ou get bone rebuilding,鈥� says Robert Neer of Massachusetts General Hospital in Boston, who led the research. 鈥淵ou can see it and you can measure it.鈥� Felicia Cosman, an osteoporosis specialist at Helen Hayes Hospital in West Haverstraw, New York, is impressed by the results: 鈥淚t restores bone architecture, something we haven鈥檛 been able to touch before,鈥� she says.
After 18 months, the density of bone mineral in women given the drug had increased by up to 13 per cent compared with those given a placebo. The drug reduced the risk of fractures by up to 69 per cent, and the risk of multiple spinal fractures by up to 86 per cent-better than any other osteoporosis treatment.
Though the committee has not yet recommended Forteo for men, Neer says that the findings were similar. Initially, it will only be available by daily injection, but Eli Lilly is developing patches, tablets and inhalers.
However, the FDA committee raised concerns that in animals the drug had increased the risk of a rare type of bone cancer, osteosarcoma. Strict follow-up studies may be required as a condition of the approval.