Drug-Coated Stents Show Use Risk

Study Says Devices by J&J, Boston Scientific Present A Higher Danger of Clots

October 24, 2006
By Sylvia Pagán Westphal
Wall Street Journal

Both major brands of drug-coated stent pose a higher risk for patients of developing blood clots months later than do traditional metal stents, according to data presented at a big cardiology meeting this week.

Boston Scientific Corp., the largest manufacturer by market share of cardiac stents, had already acknowledged a small but statistically higher risk of clots for its Taxus stent. But Johnson & Johnson, second in the stent market, had stated that, while the number of stent clots was numerically higher for its Cypher stent, the difference wasn't statistically significant.

In response to the latest findings, a J&J spokesman said the data "are subject to interpretation by a number of methodologies, some of which may yield significant differences at certain time points." The company also said that data from the company's trials would be presented today based on "new standardized definitions" of stent clots, known in medical parlance as stent thrombosis. The definitions have been created by a consortium of academics, manufacturers and regulators, and the analysis "will provide important insights into the thrombosis rates for the Cypher stent," the company said.

The results add fuel to an already heated debate over the formation of blood clots inside drug-coated stents. Stents are tiny wire meshes deployed inside arteries after clearing blockages.

Unlike metal stents, those coated with drugs prevent the gradual growth of scar tissue in the artery, a process called restenosis. But a body of evidence is growing that they also increase the incidence of blood clots inside the stents, which often lead to major heart attacks.

At the Transcatheter Cardiovascular Therapeutics meeting in Washington, D.C., updated thrombosis figures were presented for Boston Scientific and J&J's drug-coated stents, showing a similar and statistically significant risk of clots happening months after implantation.

J&J, New Brunswick, N.J., and Boston Scientific, Natick, Mass., provided raw data for the four major Cypher clinical trials, involving about 1,800 patients, and the five major Taxus trials, involving about 3,500 patients, to Gregg Stone and Martin Leon, researchers at Columbia University and co-organizers of the meeting. Dr. Stone is also principal investigator of the major Taxus trials, while Dr. Leon has played a similar role with the Cypher studies.

The researchers' analysis of the thrombosis data, presented by Dr. Stone, showed that between one and four years after implantation the Cypher stent had a statistically significant, additional clot risk of 0.6% while the Taxus' risk was 0.4%. That's an extra two to three people per 500 suffering from a stent blood clot compared with bare-metal stents.

The risk, while small, is meaningful on a public-health level since some four million people have had the devices implanted world-wide and stent blood clots are believed to cause major heart attacks and deaths about 70% of the time.

Some of the new definitions to be unveiled today, which consider certain deaths and heart attacks as thrombosis-related without actual confirmation that the events were caused by a blood clot, could add enough "noise" to companies' thrombosis tallies to minimize the differences between metal stents and drug-coated stents. But Dr. Stone says he believes the risk of thrombosis "looks real" and warned against using definitions "that obscure" this effect.

According to Boston Scientific, the benefits of its drug-coated stent in preventing restenosis offset the higher risk of thrombosis. The stent's ability to reduce restenosis spares many patients from heart attacks, it says.

As of 4 p.m. composite trading yesterday on the New York Stock Exchange, J&J was at $69.10, up 48 cents, and Boston Scientific was at $16.14, off 10 cents.

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