PARIS – A unique polymer- and carrier-free drug-eluting stent demonstrated a highly desirable early healing profile and a mere 4% target vessel revascularization rate at 9 months of follow-up in a 100-patient study presented at the annual congress of the European Association of Percutaneous Cardiovascular Interventions.
“This study is a proof of concept of the polymer-free approach. The stent retains neointimal suppression and antiproliferative efficacy like any other drug-eluting stent. If supported by long-term clinical results, this concept could have a major impact on future new stent platform development,” said Dr. Stephen Lee, professor of cardiology at the University of Hong Kong.
Dr. Stephen Lee
The BioFreedom stent was designed to avoid the chronic inflammation caused by the polymers and drug carriers utilized in other drug-eluting stents (DES), which necessitates long-term dual antiplatelet therapy (DAPT). The novel stent is a bare metal stent whose outer surface of stainless steel contains microstructural crevasses harboring a proprietary antirestenosis drug known as Biolimus A9. This is a highly lipophilic agent and hence has a strong affinity for the vessel wall. All of the drug elutes into the arterial tissue within 1 month, at which point the BioFreedom device becomes a bare metal stent – the type of stent that doesn’t require prolonged DAPT, with its attendant increased bleeding risks, Dr. Lee explained.
The 100-patient study, featuring a 100% follow-up rate at 12 months, utilized optical coherence tomography to assess the primary endpoint, which was stent strut coverage through 9 months as an indicator of early healing post intervention. At 1 month post-PCI, 85.8% of all struts were covered, as were 96.8% at 4 months, 97.1% at 5 months, and 99.6% at 9 months.
Neointimal thickness as assessed in a core laboratory increased minimally and slowly, confirming the drug’s antiproliferative effect. Neointimal thickness was 0.04 mm at 1 month, 0.06 mm at 5 months, and 1 mm at 9 months.
“This is the most important message of the study,” according to Dr. Lee. “It confirms the efficacy of the BioFreedom stent as a DES. If it didn’t curb neointimal thickness and just acted like a bare metal stent, there would be no point in using this mechanism.”
In-stent neointimal volume increased from 4.3% at 1 month to 13% at 9 months, which is “still very low” compared to other stent types, he added.
Four of 100 patients experienced asymptomatic in-stent restenosis requiring intervention within the first 9 months. With a mean follow-up duration of 468 days, there have been no additional cases of in-stent restenosis requiring treatment, no cases of late stent thrombosis, and indeed no other major adverse cardiovascular events.
Now well underway is a vastly larger clinical trial designed to confirm that the BioFreedom stent is as safe as a bare metal stent in patients at high risk of bleeding, while at the same time delivering the antirestenosis benefits of a DES. The LEADERS FREE trial is a 2,466-patient, prospective, randomized, double-blind clinical trial employing a 1-month course of DAPT following implantation of the BioFreedom stent or a bare metal stent. Results are anticipated late this year.
Dr. Lee received a research grant from Biosensors International, which sponsored the proof-of-concept study and is funding the LEADERS FREE trial.