New Drug-Eluting Stent Technology Shows Encouraging Results

Originally Published MDDI July 2004

NEWSTRENDS

Erik Swain

The battle for the lucrative drug-eluting stent market heated up at a May conference in Paris as the various players came out with new clinical results. But the event may have been most notable for the announcement of the first clinical findings on a small firm's technology that works quite different from the competition.

Conor Medsystems Inc. (Menlo Park, CA) has produced a stent that, unlike others that elute drugs, is not surface coated. Instead, it has been designed with nondeforming polymer reservoirs. The company says the reservoirs provide the stent with as much as six times the drug-dose capacity of surface-coated stents. They also enable delivery of the drug with specific release kinetics and spatial and directional control. That means the stent can deliver multiple drugs with independent release rates and directionality. 

Also unique to the Conor stent is a feature of its contours called ductile hinges. These hinges absorb expansion forces to preserve the shape of the reservoirs. That, the company says, prevents polymer deformation or extrusion during stent expansion. And, in preclinical studies, there was no residual polymer or drug after the specified release period, so a smaller than usual initial dose was needed.
At the EuroPCR meeting in Paris, Conor presented encouraging results for a pilot study of its stainless-steel MedStent, which was eluting paclitaxel to prevent restenosis. The study evaluated 191 patients in six different groups organized by amount of dose, drug-release rate, and directionality of dose.

After 4 months, all six formulations were determined to be safe. The best outcomes came for the two groups with stents that released the drug over 30 days and delivered the drug to the vessel wall. One group, which had a 10-µg dosage, had a target-lesion revascularization rate of 2.6%. (A high revascularization rate indicates a need for retreatment.) The other, with a 30-µg dosage, had a rate of 3.3%. Results for groups whose stents had release kinetics of 5–10 days were not quite as good. 

“For the first time, we have a clear indication of the benefits of kinetic release and controlled dosing in improving patient outcomes,” said Frank Litvack, Conor's chairman and CEO. “The validation of the benefits of kinetic release has positive implications for the broad application of our platform for vascular drug delivery.” 

Conor is also conducting trials in North America and Europe testing a paclitaxel-eluting cobalt-chromium stent, called Costar. 

Also at EuroPCR, Conor announced that it will collaborate with Biotronik AG (Bulach, Switzerland) on research and development of bioabsorbable drug-eluting stent technologies. These efforts would combine Conor's reservoir drug-delivery platform with Biotronik's absorbable metal stent. Launch of Biotronik's first absorbable stent product is projected in mid-2005. Biotronik also signed an agreement to distribute Costar internationally. 

The conference produced plenty of news from the sector's bigger players as well. Cordis Corp. (Miami), a Johnson & Johnson company, presented new data to address its Cypher stent's perceived disadvantage in diabetic patients. A postmarket surveillance study showed that a large number of diabetic patients using Cypher have not had to be treated for restenosis. After 6 months, the overall diabetic population had a 1.4% target-lesion revascularization rate, and the insulindependent diabetic population had a 1.5% rate. These compared with a 1% rate for the general patient population.

Major cardiac adverse-event rates after six months were 4.2% for all diabetics, 5.9% for insulin-dependent diabetics, and 2.5% for the general population. 

Diabetic patients are considered particularly hard to treat because they are more likely to suffer from hypertension, multivessel disease, narrower vessels, and obesity. 

Boston Scientific Corp. (Natick, MA), Cordis's only competitor in the U.S. market, discussed the results of a European trial of its device in 448 high-risk patients. The trial found a 6.8% target-lesion revascularization rate, compared with an 18.9% rate for bare-metal-stent patients. Diabetic patients had a 2.6% rate, compared with 22% for the bare-metal-stent control group. The average lesion length was more than 20 mm. In previous studies, it was much lower.

Medtronic Inc. (Minneapolis) reported 1-year data of a 100-patient study of its Endeavor stent. The target-lesion revascularization rate after 12 months was 1.0%, and the major cardiac adverse-event rate was 2.0%. It also reported 30-day safety data for a 1200-patient study in Europe, Asia, and the Middle East. Target-lesion revascularization at 30 days was 0.2% for one group and 0.3% for another. Major cardiac-adverse event rates were 2.9% in the first group and 3.5% in the second.

Guidant Corp. (Indianapolis) reported that its everolimus-eluting stent did not cause any new major cardiac adverse events in patients between 6 and 12 months after deployment. The rate remained at 4.8%.

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