Previous studies have documented that a slow-release polymeric sirolimus-eluting stent (Cypher, Cordis) and paclitaxel-eluting stent (Taxus, Boston Scientific) reduce neointimal formation and result in decrease of angiographic restenosis and target lesion revascularization at 1-3 years in the multicenter randomized clinical trials RAVEL, SIRIUS, and TAXUS I-VI.From these studies, the two leading drug-eluting stents (DESs) of the Cypher and Taxus have been widely and rapidly accepted as a standard treatment of coronary lesions.

Recently, randomized studies were conducted to reveal different outcomes of the different two DESs. These studies showed that the sirolimus-eluting stent was better than the paclitaxel-eluting stent in terms of lower angiographic restenosis rate or the two DESs were similar in angiographic outcomes. A recent meta-analysis supported results of the former randomized studies. Patients receiving sirolimus-eluting stent had a significantly lower risk of restenosis and target vessel revascularization compared with those receiving paclitaxel-eluting stent.

With a recent approval of new DES, ABT-578-eluting stent (Endeavor, Medtronic, Minneapolis, MN), other comparison studies have been conducted to compare Endeavor ABT-578-eluting stent with the sirolimus-eluting stent and paclitaxel-eluting stent. ABT-578 and sirolimus share some common structural and biological properties. The ENDEAVOR clinical trials are currently in progress to evaluate a phosphoryl choline (PC)-coated ABT-578-eluting stent for the prevention of restenosis. The Endeavor ABT-578-eluting stent utilizes a cobalt alloy balloon-expandable stent (Driver; Medtronic) with a geometry similar to the stainless steel stent used in this preliminary study (S7; Medtronic). The Endeavor ABT-578-eluting stent also employees a PC strut surface coating as the drug delivery reservoir with a dose of 10 ug/mm of ABT-578. The Endeavor ABT-578-eluting stent, however, differs from the stent used in this experimental study by the addition of a drug-free PC coating to serve as a diffusion barrier to retard drug release from the polymer reservoir. Angiographic analysis at 4 months in the 100-patient focal de novo lesion ENDEAVOR I feasibility study demonstrated a mean in-stent percent diameter stenosis of approximately 14% and a late lumen loss of 0.3 mm with a low frequency of target lesion revascularization (1%). The clinical outcomes from the ENDEAVOR II (1,500 patients randomized to ABT-578 or bare metal stent) and the ENDEAVOR III (436 patients randomized 3:1 to ABT-578 or Cypher) trials as well as other ongoing studies showed efficacy of the PC-coated ABT-578-eluting stent. In ENDEAVOR III study, the Endeavor stent had larger late loss and higher binary restenosis in both the analysis segment and stented segment. In contrast, the TLR rates are not statistically different between the Endeavor (6.0%) and the Cypher (5.3%, p=1.0) stents. This result of this study raised several questions to warrant further randomized studies 1) is the angiographic superiority of Cypher stent applied to the more complex lesions, 2) why is the TLR rate similar in spite of significantly different angiographic outcomes, 3) which is better in the Endeavor and the Taxus stents, etc. The ENDEAVOR IV study is being conducted to compare the safety and efficacy of the Endeavor stent versus the Taxus stent. However, the inclusion of ENDEAVOR IV study was also limited that this study did not include all complex lesions. Because of the limitations of current ENDEAVOR series, a further large randomized study for the concurrent comparison of the three DESs in the treatment of real-world practice would be needed.