Bone-Building Drugs May Also Beef Up Cartilage
June 15, 2001 -- A drug being developed to prevent the breakdown of bone caused by a type of cancer may also be able to prevent or slow the deterioration of cartilage in joints, a condition that can lead to painful and disabling osteoarthritis and rheumatoid arthritis, report French researchers in a small study published in the May issue of the journal Bone.
In a study of 26 patients with Paget's disease of bone, a disorder marked by breakdown of bone and abnormal attempts by the body to repair it, the drug Zometa appeared to at least partially prevent the deterioration of type II collagen, the protein that is the primary component of cartilage in joints.
Their findings suggest that Zometa and similar drugs used to treat osteoporosis and related conditions may also have a protective effect on cartilage in general, say Patrick Garnero, MD, and colleagues with the French National Institute of Health and Medical Research.
Zometa belongs to a class of drugs known as bisphosphonates, which includes the FDA-approved osteoporosis drugs Actonel and Fosamax; Zometa has not been approved for either osteoporosis or Paget's disease but may be in the near future, according to a spokesperson for the Paget Foundation. Currently, its intended purpose is the aforementioned treatment of a condition brought about by cancer that has spread to bones.
Throughout life, new bone is constantly being formed by cells called osteoblasts; the bone-building action is balanced by bone breakdown or "resorption," which is performed by another class of cells called osteoclasts. Paget's disease and osteoporosis are caused by an imbalance in the bone formation/breakdown cycle. Bisphosphonates help to preserve bone by interfering with the action of osteoclasts, thereby allowing a more normal bone growth pattern to occur.
Because studies of bisphosphonates in animals had suggested that the drugs could also have an effect on the formation of joint tissues, Garnero and colleagues looked for evidence of a similar effect on cartilage in humans. They looked for signs of type II collagen destruction in the urine of 26 patients with Paget's disease and a comparison group, both before and after a single injection of either Zometa or a placebo.
They found that the patients treated with Zometa had significantly lower levels in their urine of an indicator for collagen type II breakdown. "[Zometa] not only reduces bone turnover, but also directly decreases type II collagen degradation in patient's with Paget's disease, suggesting that bisphosphonates may have [cartilage-protective] effects in humans," the researchers write.
"[Zometa] is a powerful drug that we hope we can use in Paget's disease, but the company has not done studies to get it approved for Paget's although I'm desperately trying to push them to do it," says Frederick Singer, MD, clinical professor of medicine at the University of California at Los Angeles.
Singer, who was not involved in the study, tells WebMD that "if there is a decrease in breakdown of type II or cartilage-type collagen, that suggests one thing immediately to me: that part of the deterioration of the cartilage may be from cells which break down cartilage. ... It's possible that if their observation is significant, it suggests there might be some benefit from the Paget's drugs on the joints, but this is a very long way from any kind of reality."