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New type of sirolimus-eluting stent demonstrates superior results

September 22, 2009

A new type of sirolimus-eluting stent (SES) successfully showed significantly greater neointimal suppression than the paclitaxel-eluting stent (PES) with greater vessel wall integrity surrounding the stent, confirming the finding of superiority of the SES over the PES stent for the trial's primary endpoint of in-stent late loss.

Results from the RES-ELUTION I Trial on the safety and effectiveness of a new sirolimus-eluting stent in the treatment of coronary artery disease (a single atherosclerotic lesion) in native coronary arteries will be presented at the 21st annual Transcatheter Cardiovascular Therapeutics (TCT) scientific symposium, sponsored by the Cardiovascular Research Foundation (CRF).

RES-ELUTION I, which began in March 2008, is a multi-center, randomized, single-blind controlled trial comparing the sirolimus-eluting reservoir-based stent (SES) with a paclitaxel-eluting stent (PES) system in de novo native coronary artery lesions. A total of 394 subjects were randomized to treatment with either the sirolimus-eluting or paclitaxel-eluting stents. Principal investigators of the trial included Alexandre Abizaid, MD, John Ormiston, MD and Christian Spaulding, MD.

Clinical results will be presented by John A. Spertus, MD on Thursday, September 24 at 2:45 p.m. during the Featured Clinical Trials: First Report Investigations session in Room 131. In addition to the oral presentation, a detailed intravascular ultrasound (IVUS) analysis will be on display as a poster abstract (TCT-360) on Tuesday, September 22 between 8:00 a.m. and 10:00 a.m. in Hall D of The Moscone Center. The poster will be presented by Hiromasa Otake, MD of Stanford University (Stanford, Calif.) on behalf of the RES-ELUTION I investigators.

This new sirolimus-eluting stent (SES) utilizes a reservoir technology that incorporates a number of small wells, each acting as a depot into which drug-polymer compositions are loaded. The stent's design achieves both a significant reduction in total polymer load as well as a reduction in tissue-polymer contact by more than 75% compared to conventional DES in which the entire stent surface is coated with polymer. Its use of a bioresorbable polymer is another theoretical advantage from the safety perspective, allowing the drug-eluting stent to become simple bare metal within the vessel wall approximately 3 months after deployment.

In this clinical trial, detailed arterial responses to the new DES technology were also investigated in vivo using intravascular ultrasound (IVUS). With IVUS, a tiny catheter is inserted into a coronary vessel where high-frequency sound waves reflect off tissue or vessel walls. The reflected waves create a cross-sectional image from within the vessel to aid in visualizing its structure, thereby providing both quantitative and qualitative information on vessel reaction after stenting.

Serial IVUS (immediately post-stenting and 6-month follow-up) was performed in a pre-defined IVUS subset of 100 patients (52 SES in 50 patients; 52 PES in 50 patients). Volumetric IVUS analysis demonstrated significantly less neointimal proliferation in the sirolimus-eluting stent (% neointimal volume: 5.5±11.0 vs. 11.5±9.7, p=0.016), resulting in less late lumen area loss and smaller maximum cross-sectional narrowing (neointimal area/stent area) than PES. In addition, serial IVUS analysis revealed significantly less outward vessel remodeling in the SES than in PES. The incidence of late-acquired incomplete stent apposition (ISA) was similar between the SES and PES. However, SES was associated with less outward vessel remodeling at the ISA segment, possibly suggesting different underlying mechanisms of this phenomenon.

"Our study is the first report investigating the detailed arterial responses to this new DES technology, with a randomized, blinded comparison of sirolimus-eluting stents with paclitaxel-eluting stents in human de novo native coronary lesions," said Dr. Otake.

"The combination of a different formulation strategy with different types of drug appeared to impact arterial response after DES therapy," Dr. Otake added. "Our study confirmed that the advanced formulation strategy of this new DES can perform with efficacy exceeding a first-generation DES with the potential for improved long-term safety because it turns into a bare metal stent within 3 months. This stent may be a promising DES option to treat the patients with coronary artery disease while embracing the long-term safety of bare metal stents."

Cardiovascular Research Foundation