The stumbling block is that the vessels close up again in at least one-fifth of the patients who've had stents implanted. And the potential answer -- scientists are hopeful, but stress that the results are early -- is now approved in this country for a different purpose: to prevent transplant patients from rejecting their new organs.
The formal name of the new device is a "sirolimus-eluting stent." A stent is a small, expanding tube that is put into an artery after bypass surgery or angioplasty to keep blood flowing through the treated artery.Stents themselves are not new. The American Heart Association estimates that they were implanted in almost half the 1 million patients who underwent angioplasty in 1999, the last year for which data are available. What's new about the stent used in Europe is the "sirolimus-eluting" business. This means that the stent is coated with an unusual chemical called sirolimus, which elutes -- diffuses -- into the wall of the artery for about a month after implantation.
Sirolimus is sold by Wyeth-Ayerst as Rapamune, named in part after what native Easter Islanders call their remote South Pacific enclave -- Rapa Nui.
The idea is that eluting sirolimus will prevent the growth of new tissue that often causes the treated artery to close up again. And a report in tomorrow's New England Journal of Medicine, by cardiologists at 19 European medical centers, says that it works.
In a study of 238 patients who underwent angioplasty, more than a quarter of those who received ordinary, uncoated stents had their arteries narrow by at least 50 percent after six months. None of the coated-stent recipients had that degree of closure. And in a one-year follow-up, only 5.8 percent of the coated-stent recipients had major cardiac events, such as heart attacks, compared to 28.8 of those who got standard stents.
The information in the report was used to gain approval for routine use of the coated stent by European regulators, says Marty Schildhouse, a spokesman for Cordis Corp., a Johnson & Johnson subsidiary that makes the device and funded the study. That approval was given on April 12. Now the U.S. Food and Drug Administration is being asked to give the same approval.
"The submission is currently under review by the FDA," says Schildhouse. "We anticipate approval somewhere in the March-April 2003 period."
That's just an estimate, because FDA action is always somewhat unpredictable. An FDA spokesperson says it is agency policy never to comment on the status of approval submissions.
Schildhouse adds that, if the device wins FDA approval, "We expect there will be a movement of patients from both bypass surgery and medical therapy to eluting stents."
The newly published report is only part of the ongoing coated stent story, says Dr. Gregory D. Curfman, executive editor of the journal, who wrote an accompanying commentary.
"The research we covered provided only a six-month follow-up," he says. "There are other studies in progress that I think will answer the questions very quickly. And the follow-up data that extends beyond six months looks quite good."
Sirolimus itself has a fascinating history, Curfman adds. It is produced by a species of bacteria discovered in 1975 on Easter Island and has been used as an antibiotic and to prevent rejection of organ transplants.
If the early results hold up, he writes, "a new chapter will be opened in the story of this drug, which traces its origin to one of the most remote places on earth."
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