The Future of Stent Technology Highlighted at TCT 2009
Standard drug-eluting stent technology seemed to have taken a backseat at this year’s TCT as cardiologists look forward to the next-generation DES using bioresorbable polymer coatings and totally bioresorbable stents.
The big news in DES at TCT included results of the SPIRIT IV trial, which showed XIENVE V outperformed TAXUS Express, the former market leader. However, the study results basically boil down to splitting hairs over very low MACE and TLR rates that occur in less than 7 percent of patients. The study clearly shows even the lower-performing TAXUS Express performed very well and great advancements in stent technology have been made over the past 10 years. However, with the advent of bioabsorbable polymers and stents, some cardiologists hope to see the near elimination of MACE, TLR and late-stent thrombosis.
DES with bioabsorbable polymers that took over the limelight at TCT included the Cordis NEVO, Boston Scientific’s JACTAX and Biosensor’s Biolimus A9 stent. Cordis expects to submit an application for FDA review for the NEVO by the end of 2011. Boston Scientific hopes to begin its FDA trial for the JACTAX in 2010.
During the TCT Drug-Eluting Stent Summit Renu Virmani, M.D., CVPath Institute, Gaithersburg, Md., explained some of the reasons why today’s DES are inadequate. In animal studies, he said 90 days after stenting it is still typical to find non-enodotheliaized stent struts. Also, he showed electron microscopy images of stent polymer flaking off of TAXUS, XIENCE and Endeavor stents, which he said may contribute to myocardial embolization.
“We need a new generation of stents,” said Antonio Colombo, M.D., Columbus Hospital/San Raffaele Hospital, Milan, Italy, after reviewing some of the clinical shortcomings of current DES technology. He said the main issues with today’s stents include thrombus and restenosis, and while the incidence is very low (he cited rates of 1.6 percent with Endeavor and less than 1 percent with TAXUS), he said next-generation stents need to address these areas more effectively. Dr. Colombo said the next generation stents include those with bioabsorbable polymers used to load the nonproliferative drugs onto the scaffolding. He pointed to the Cordis NEVO, which early studies show promising results with much lower late-loss at six months when compared to TAXUS.
Speakers also highlighted another direction in stent technology using new coatings to promote rapid endothelialization to allow quick healing of the vessel. The idea is to eliminate the need for polymer and anti-proliferative drugs all together. Robert de Winter, M.D., Ph.D., Academisch Medisch Centrum, Amsterdam, highlighted trial data on the Genous Bioengineered R Stent, being developed by OrbusNeich. It uses the antibody CP34 as a surface coating to attract and capture endothelial progenerator cells (EPCs). The 5,000-patient e-HEALING registry compares Genous with the CYPHER and Biometrix stents. At one year Dr. de Winter said myocardial infarction, MACE, and stent thrombus were all much lower for the Genous stent. But, he did point out TLR was comparable. “It has an excellent 12-month outcome,” Dr. de Winter said.
Abbott’s totally bioabsorbable BVS stent, currently in trials in Europe, also gained significant attention at TCT. It was cited in several sessions and in the company’s works in progress section of its booth. Examples of the stent, made of 100 percent polymer, were on display at Abbott’s booth, and engineers working on the project had a steady stream of cardiologists who were very interested in their research.
Revisions to the stent’s chemistry were made since the first in-human trials in hopes of reducing recoil. A second prototype is now going through trials in 65 patients. If this new version of the BVS has positive outcomes, the company plans to use the findings as a basis to apply for CE mark approval in Europe.
“We hope this will act as a metal stent,” said Chuck Simonton, M.D., Abbott Vascular’s chief medical officer and division vice president of medical science, during TCT. “It will allow patients vessels to heal more normally.”
He said it is possible FDA trials on the stent could begin as early as 2012, possibly putting the stent on track for an FDA approval by 2015.