Delivering Heart Drugs From the Inside
New stent with biodegradable coating could advance cardiovascular treatment
MONDAY, May 3, 2004 (HealthDayNews) -- German researchers are reporting the successful test of a biodegradable coating for stents, the flexible mesh tubes used to keep arteries open in heart patients.
Coated stents release drugs designed to prevent arteries from becoming clogged again, and they're widely used because they are clearly more effective than plain metal stents. The drugs are contained in polymers that stay on the stents permanently.
The advantage of the new biodegradable polymer tested by the German scientists is that it provides a potential way of delivering other drugs into the arteries, something existing permanent polymers can't do, the researchers said.
The still experimental stent, made by Guidant Corp., uses a biodegradable polymer that disappears once it has delivered the drug. The German scientists report in the May 4 issue of Circulation that the new stent is at least as effective as existing coated stents, said Dr. Peter M. Fitzgerald, an associate professor of medicine and engineering at Stanford University Medical Center. He was also leader of the group that analyzed the data from the study.
The point of the study was not to show that the new coating is more effective at keeping arteries open than existing polymers, Fitzgerald said. "The rates [of unclogged arteries] are so incredible [for any type of coated stent] in terms of efficacy that you would need tens of thousands of patients to know whether they can improve on them," he said.
The Guidant stent releases everolimus, which inhibits cell growth and reproduction. It is a chemical relative of serolimus, one of two drugs used in coated stents that gained U.S. Food and Drug Administration approval in the last year.
To Fitzgerald, the important thing is not the drug that is being released from the stent, but the nature of the biodegradable compound that carries it and then dissolves harmlessly after the drug is released.
There is the convenience of "timing the vehicle with its job, knowing that once you deliver the drug it goes away," Fitzgerald said.
More important, there is the concept of "delivering other drugs [that currently must be delivered in pill form] with a biodegradable polymer," he said. "Once you show that it works, you can think of expanding treatments that take advantage of a polymer that delivers a drug on the inside rather than the outside. You can treat a broader range of cardiovascular sites that we need to deal with."
The new study included 42 patients who had artery-opening procedures, such as balloon angioplasty, at the Heart Center in Siegberg, Germany.
Fifteen patients had plain metal stents implanted after the procedures. The other 27 got stents coated with the biodegradable polymer that released everolimus.
At the start of the trial, the coated-stent patients had artery narrowing averaging 64.1 percent; after six months, the narrowing was only 2.6 percent. In patients who got the plain metal stents, narrowing was reduced from 62.1 percent to 27.8 percent.
Guidant executives reported last November that the company planned to start two trials in 2004 -- an 800-patient study aimed at getting approval of the new stent in Europe, and a 975-patient study with a similar goal in the United States.