The ENDEAVOR I and II trials show that drug-eluting stents coated with the sirolimus analogue ABT-578 are effective for up to 24 months in prevention of late stent thrombosis and need for revascularization of the target lesion, according to a presentation at the annual meeting of the European Society of Cardiology.

"The safety and efficacy data for ENDEAVOR I at 24 months and Endeavor II at 12 months confirm the clinical safety and efficacy of the Endeavor drug-eluting stent, " said Professor Martin T. Rothman, Consultant Interventional Cardiologist at Barts and the London NHS Trust. "The safety data suggest that the Endeavor stent is at least as good as the best in class drug eluting stent to date, and perhaps even better."

Professor Ian Meredith, MD, Monash Medical Centre, Melbourne, Australia, presented two-year results from the 100-patient ENDEAVOR I study conducted in Australia and New Zealand, while William Wijns, MD, Co-Director of the Cardiovascular Center, OLV Ziekenhuis, Aalst, Belgium, presented one-year data from the 1,200-patient ENDEAVOR II Pivotal study.

The ENDEAVOR I study showed a 24-month target lesion revascularization rate of 2.0 per cent, the same percentage the trial reported a year earlier. The rate represents retreatment of the previously stented lesion and is widely viewed by physicians as the most important measure of drug-eluting stent effectiveness. Also, there were no additional cases of stent thrombosis in the 97 study patients who received follow-up over the second 12-month period.

"There has been no increase in target lesion revascularization in the ENDEAVOR I study between 12 months and 24 months," said Meredith, the trial's primary investigator. "Only two patients required repeat interventions on the target lesion during the first 12 months and that number has remained constant at 24 months. These data show that the impressive early clinical results in ENDEAVOR I are sustainable to two years and the excellent safety record remains intact."

The ENDEAVOR II study, which compared Endeavor stents to the Medtronic Driver(R) bare metal stent, also demonstrated no observed cases of stent thrombosis between 9 and 12 months in either study arm. To date, there have been no reported late stent thromboses with the Endeavor stent in 700 patients who have 12-month or longer follow-up. The ENDEAVOR II study also demonstrated sustained efficacy, with a 12-month target lesion revascularization rate of just 6.0 per cent for Endeavor patients, compared with 13.2 percent for the bare metal control group. This means that 94 per cent of patients randomized to the drug-eluting stent remained free from repeat procedures of their stented vessels after one year.

"The major clinical parameters in ENDEAVOR II have remained low and stable in comparison to the Driver stent control arm, and the lack of late stent thrombosis observed in this trial with the Endeavor stent is notable," said Wijns, a Co-Principal Investigator of the ENDEAVOR II Pivotal Trial. "We are becoming increasingly concerned about the safety of drug-eluting stents with regard to late stent thrombosis, which can be quite serious and often manifest as an acute myocardial infarction or even death."

The Endeavor stent has been evaluated in approximately 1,000 patients to date. This includes nearly 300 patients with 9-month follow-up from the ENDEAVOR II Continued Access trial, a study designed to collect additional patient data. Of these 1,000 patients, only 4 have experienced stent thrombosis (0.004), with no cases occurring after 30 days.

The ENDEAVOR II Continued Access trial also evaluated direct stenting, which is placement of a stent without first using a balloon catheter to open the lesion. The Endeavor stent was successfully placed in 98 percent of patients undergoing direct stenting and in 99 percent of patients where vessels were pre-dilated.

The Endeavor drug-eluting stent is based on the market-leading Driver coronary stent, which is made of a cobalt alloy and has a unique modular architecture that provides enhanced deliverability over standard bare metal stents.