ACC: Bioabsorbable Stent Just Barely Exceeds Bare-Metal Devices

NEW ORLEANS, March 25 -- An investigational bioabsorbable coronary artery stent, in its first human trials, showed acceptable safety, with efficacy better than bare-metal devices but well short of drug-eluting devices, Dutch researchers said here.

When the Bioabsorable Everolimus-Eluting Coronary Stent System was used to treat de novo coronary artery lesions in 26 patients, the in-stent late loss was 0.44 mm at six months and the restenosis rate was 11.5%, said Patrick Serruys, M.D., Ph.D., of Thoraxcenter-Erasmus University in Rotterdam.

Bare-metal stents, he said at the American College of Cardiology meeting, typically have a late loss of about 0.85 mm while late loss averages about 0.10 to 0.20 mm with drug-eluting stents.

Additional studies are going forward with a new stent design that "we hope will cut the late loss by about 50%." That redesign should also correct what Dr. Serruys said was the most unexpected finding of the study-stent shrinkage.

Shrinkage problem -- the stent was shorter after it was fully expanded -- probably contributed to both late loss and restenosis rates, said Dr. Serruys, who was the principal investigator of the ABSORB trial. The 26 patients in the study were treated with 3.0 mm by 12.0 mm stents.

Dr. Serruys said the researchers had no idea how long dual antiplatelet therapy should be used for these patients, if at all. Nonetheless all patients were maintained on clopidogrel (Plavix) plus aspirin for the duration of the trial.

But Dr. Serruys maintained that the most important finding was "we have taken a small step toward a future in which vessels will be free from the 'metal cage' of traditional stents."

Those metal cages, he said, "cannot react to stress in the same way as the natural endothelium." By contrast, a stent that is fully absorbed into the vessel "makes a certain physiologic sense."

The new stent "has a polylactic acid backbone, with an everolimus-polylactic acid coating," he said. The stent releases everolimus (anti-proliferative drug) over about 30 days.

The stent itself is "fully digested, metabolized in water," he said. In animal studies full dissolution took about 12 to 18 months. "We don't know what will happen with human endothelium."

Spencer King III, M.D., of Emory and the Fuqua Heart Center of Piedmont Hospital in Atlanta, who chaired an ACC press conference where Dr. Serruys discussed the new stent, said he would reserve judgment because the study was too small and the follow-up too short to become too enthusiastic.

He pointed out that early animal trials of similar polymers "had just awful results, but maybe this time it will be different." He noted that in this small study the stent appeared safe since there were no deaths and the only major adverse cardiac event was a non Q-wave myocardial infarction in one patient.

Dr. Serruys agreed that the data should be very cautiously interpreted adding "we really need about seven years of data on any new stent before we can really assess its safety and efficacy."