Drug-coated stents offer new approach to treatment

Restenosis is the formation of new blockages at the site of the angioplasty or stent placement.In the fall of 2000, Vice President Richard B. Cheney was admitted to a hospital with unstable angina. As part of his care, he received …

Restenosis is the formation of new blockages at the site of the angioplasty or stent placement.In the fall of 2000, Vice President Richard B. Cheney was admitted to a hospital with unstable angina. As part of his care, he received a stent placement or angioplasty, which entails a balloon being passed across an atherosclerotic plaque in a coronary artery. The balloon is then inflated – thus compressing the plaque, and widening the opening of the artery. Compression of the plaque is a far from gentle process, and nearly always creates trauma to the blood vessel wall.

In March 2001, Cheney was found to have restenosis at the site of his stent placement. Restenosis is the formation of new blockages at the site of the angioplasty or stent placement and occurs in 40- 50 percent of patients who have undergone the procedure within three to six months.

There are two major mechanisms responsible for restenosis. One of these is thrombosis, or clotting at the site of the treatment. The risk of its occurrence is highest immediately after angioplasty, and the condition is treatable with anti-clotting drugs. The other issue is the growth of tissue at the site of the treatment. The use of “inhibitors” reduces this risk.

A new approach holding out great promise is the use of drug-coated stents. The most commonly mentioned are sirolimus-coated stents, rapamycin-coated stents, and paclitaxel-coated stents. At the Congress of the European Society of Cardiology in Stockholm, in the second week of September, investigators reported early results from the RAVEL trial, which examined the efficacy of a drug-coated stent made by Johnson & Johnson.

In the follow-up period of 210 days, there was no restenosis in patients receiving the drug-coated stent in the RAVEL trial. Despite the remarkable early results with the sirolimus-coated stent, release of this product for general clinical use is not expected until 2002 in Europe, and in 2003 in the United States.

Johnson & Johnson has launched a new set of clinical trials, which include 35 medical centers in Europe and Israel. The two hospitals participating in Israel are the Hadassah Medical Center in Jerusalem and Haifa’s Rambam Medical Center. The results of the trials will be viewed initially after eight months and the study will include a five-year follow-up.

“The clinical trials that we are embarking on are somewhat different then those reported on in Stockholm. First, the stents will be somewhat smaller in diameter and the lesions being treated will be longer. Essentially, we will be performing trials on patients who would tend to have a higher incidence of restenosis then the previous group,” said Louis Gruberg, a participating cardiologist at the Invasive Cardiology Center at the Rambam Medical Center, in Haifa.

The Israel High-Tech & Investment Report in 1992 obtained its first insights and information in angioplasty from Hylton Miller, a cardiologist and director of the catheterization unit at Tel-Aviv’s Sourasky Medical Center. The vision was then formed that the rapidly developing field of stents, as an adjunct to conventional balloon angioplasty, was well on its way to becoming one of the fastest growing fields among medical devices. Over the years, nearly every type of interventional angioplasty procedure has been carried out at the Sourasky Medical Center. Approximately 1,000 procedures are carried out yearly at the center.

According to a Morgan Stanley Dean Witter report on coronary stents, 770,000 angioplasty procedures were carried out in the United States last year. Of these, more than 80 percent included stents. Clinical work currently being carried out in Israel and in European medical centers will determine whether medicated stents will assume the lead in a new generation of restenosis-free cardiac treatment.

Industry estimates put the annual world market for stents at $1.2 billion. However, this figure may increase dramatically if the new stents gain an important segment of the total stent market. Conventional stents can cost as much as $1,000 each, while the coated stents may triple in cost.

Israeli medical researchers were at the forefront of medical stent research and development. Professor Rafael Beyar, the Israeli inventor of the stent, now serves as the dean of the Technion Medical School and continues to oversee a range of medical projects. The stent developed and produced by the Israeli Medinol Ltd. is marketed by the Boston Scientific Company, which commands about 30 percent of the U.S. stent market.