BioABSORBable Stents: A New Era or Pie in the Sky?

March 27, 2007

March 27, 2007 (New Orleans, LA) – The first-ever human trial of a new fully bioabsorbable everolimus-eluting stent (Abbott Vascular) has shown promising results, although a second generation of the device will need to be developed because there was some shrinkage of the stent during the six-month follow-up.

Dr Patrick Serruys (Thoraxcenter, Rotterdam, the Netherlands) presented results of the ABSORB trial during a late-breaking session at the American College of Cardiology 2007 Scientific Sessions today. In the trial, 26 patients received the new stent--which, it is hoped, will completely dissolve after 12 to 18 months--and there was no evidence of stent thrombosis after six months, together with a low rate (3.3%) of ischemia-driven major adverse cardiac events (MACE). 

But late loss and restenosis were greater with the bioabsorbable stent than with current drug-eluting stents, and Serruys said the 15% shrinkage seen with the new stent may be to blame for these findings. He is hoping that the modification of the stent design--due to be completed by the end of the summer--will solve this problem. "This may be the beginning of a new era. I'm convinced of it," he commented.

However, chair of the late-breaking press conference, Dr Spencer King (Emory University School of Medicine, Atlanta, GA), was more circumspect: "Our early experience with polymer stents was terrible in experiments in pigs. This trial is in only 30 patients, with short follow-up. However, on the plus side, we didn't see any inflammation. Time will tell."

Time to full absorption of stent unknown

Serruys explained the new fully bioabsorbable stent is made from a polylactic acid (PLA) backbone, with an everolimus/PLA coating and a range of release of drug similar to the Cypher stent. "It's a wonderful reservoir," he explained to heartwire , adding that although the everolimus is currently only in the coating, it might be possible in future to also put the drug into the backbone of the stent.

Serruys says the bioabsorbable stent behaves like a metal stent in terms of scaffolding, but the hope is that when it disappears "it will give the vessel back its flexibility." The stent is known to dissolve to carbon dioxide and water in around 12 to 18 months in animals, but he said the exact time frame for degradation of the device in humans is not known.

In this prospective open-label trial, stents of 3.0 mm by 12.0 mm were used, and 26 patients ultimately received a stent. The patients received clopidogrel for six months, although Serruys admitted to heartwire : "We don't have the slightest idea how long we should give clopidogrel with this stent.

The 3.3% MACE rate was the result of a single event--a non-Q-wave MI. The same patient underwent a repeat intervention that occurred at the site of the original procedure, resulting in an overall target lesion revascularization rate of 3.3%.

Late loss and revascularization were greater with the bioabsorbable stent at 180 days than with drug-eluting stents, but lower than rates seen with bare-metal stents. "We believe if we work on the stent design itself we could further reduce this late loss and restenosis," he said.

Serruys told heartwire that the second-generation device will be ready for testing later this year, with the first results available early in 2008.

Angiographic results (per-treatment evaluable)

6-month follow-up 26 lesions
In-stent diameter stenosis (%) 27
In-stent late loss (mm) 0.44
In-stent restenosis (%) 11.5



The ABSORB study is continuing--it is designed to enroll up to 60 patients in Belgium, Denmark, France, New Zealand, Poland, and the Netherlands. Key end points of the study include assessments of safety--MACE and stent-thrombosis rates--at 30, 180, and 270 days, with an annual follow-up for up to five years. Other key end points of the study include follow-up measurements assessed by angiography, IVUS, and state-of-the-art imaging modalities at 180 days and two years.

The complete contents of Heartwire , a professional news service of WebMD, can be found at www.theheart.org, a Web site for cardiovascular healthcare professionals.

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