New Drugs

Although many new drug eluting stent (DES) programs are underway, most are focusing on using existing drugs or their analogs with new stent technology (Figure 1). Thus, Eberhard Grube, MD, HELIOS Klinikum, Siegburg, Germany, does not see many new drugs on the horizon. One stent program that Prof. Grube felt was particularly promising involves using Biolimus A9® that is eluted from a biodegradable polylactic acid (PLA) polymer. Biolimus A9®, a rapamycin derivative, has immunosuppressive properties that are similar to those of sirolimus, but is more rapidly absorbed by the vessel wall, readily entering smooth muscle cell membranes and blocking cell proliferation [Grube & Buellesfeld. Exp Rev Med Dev 2006]. This stent is currently being tested in two clinical trials (STEALTH II and LEADERS).

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Figure 1.

Evolution of Intracoronary Stents.

Nanotechnology

One of the most exciting areas in interventional cardiology is the development of new therapies, procedures, and devices that are derived from nanotechnology. Nanotechnology allows researchers to combine materials (eg, proteins and metals) on a scale that could not have been combined previously. According to Steven R. Bailey, MD, University of Texas, San Antonio, TX, the result of these combinations is nanosynthesized metals that have fewer surface impurities and provide improved endothelial coverage, decreased protein deposition, improved stress, and fracture resistance. In addition, nanoscaffolds and nanoporous surfaces actually change the surface of the stent so that polymers are no longer needed for drug delivery.

Pro-Healing Approach

Endothelial progenitor cells (EPCs) are associated with new vessel formation and vessel repair. They accelerate the natural healing process after stent placement by forming an endothelial layer over the stent that provides protection against thrombus formation and restenosis. The e-Healing Study is a worldwide, prospective registry of patients (current enrollment ∼5000) who have been treated with a bioengineered, antibody-coated stent that captures circulating EPCs. Data presented by Robbert J. de Winter, MD, Academic Medical Center, Amsterdam, The Netherlands, showed that use of the stent resulted in low rates of major cardiac adverse events at 6 and 12 months (Table 1). The use of these stents might reduce the duration of dual platelet therapy.

Bioabsorbable Stents

Bioabsorbable stents, called “The Holy Grail” by some, have several theoretical advantages over permanent stents, including no chronic inflammation, short duration of platelet therapy after stenting, and avoidance of late thrombosis. Although the initial experience is promising [Erbel R et al. Lancet 2007; Ormiston JA et al. Lancet 2008], according to Ron Waksman, MD, Georgetown University, Washington, DC, bioabsorbable stents are not ready for mainstream use. He sees the remaining challenges as restenosis, radial strength, biocompatibility, radioopacity, and ability to combine the kinetics of stent degradation with the kinetics of drug elution.

Paclitaxel-Coated Balloon

Bruno Scheller, MD, Universität des Saarlandes, Homburg/Saar, Germany, presented results from several studies that evaluated the drug-eluting balloon (DEB), a new approach that is based on immediate, short-lasting drug release and homogeneous drug distribution along the vessel wall that can be used alone or in combination with a BMS. The DEB has been tested in patients with coronary in-stent restenosis and has shown positive results in terms of late lumen loss and event-free survival.

Many challenges remain in the development of new stent systems. It was clear, however, from the information presented at this session that researchers are well on their way to finding new and innovative solutions to some of the problems that are seen with the current generation of stents.