TCT: Polymer-free DES shows promise for safety at one year; larger studies to follow

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BioFreedom polymer-free drug-eluting stent. Image source: Biosensors International

WASHINGTON, D.C.--BioFreedom, a polymer-free drug-eluting stent (DES) from Biosensors International, showed a strong safety profile, compared with the Taxus paclitaxel-eluting stent (Boston Scientific), which contains a durable polymer, based on the one-year results of the first-in-man BioFreedom presented as a late-breaking trial at the annual Transcatheter Cardiovascular Therapeutics (TCT) conference.

The BioFreedom features a micro-structured abluminal surface, which allows the release of Biolimus A9 without the use of a polymer. There were two versions of the stent used in the trial--the BioFreedom low dose and the BioFreedom standard dose.

Principal investigator Eberhard Grube, MD, from the International Heart Center Essen in Germany, said that he and the BioFreedom investigators hypothesized that a polymer-free drug release via porous-eluting stents may reduce late events caused by polymer stent coatings.

The researchers speculated that with this new stent design the potential advantages could be:

  • Avoiding long-term late adverse effects that might be attributable to the polymer;
  • Improved surface integrity since there is no polymer to be sheared or peeled away from the stent struts; and
  • Possible shorter need of dual-antiplatelet therapy.

The trial enrolled 182 patients. The first cohort of 75 participants were randomized to the BioFreedom standard dose of 15.6 µg/mm (25 patients), the BioFreedom low dose of 7.8 µg/mm (26 patients) or the Taxus Liberté (24 patients) for a four-month angiographic follow-up. The second cohort of 107 participants were randomized to the BioFreedom standard dose of 15.6 µg/mm (35 patients), the BioFreedom low dose of 7.8 µg/mm (36 patients) or the Taxus Liberté (36 patients) for a 12-month angiographic follow-up. The angiographic follow-up rate in both cohorts was 92 percent.

The primary endpoint was in-stent late lumen loss at 12 months in the second cohort. (The non-inferiority margin was 0.24 mm.) The secondary endpoint was in-stent late lumen loss at four months in the second cohort, the results of which were reported at the 2009 TCT conference. Another secondary endpoint was the 12-month major adverse cardiac event (MACE) rate—which included death, MI emergent bypass or target lesion revascularization—in both cohorts.

Dual-antiplatelet therapy was recommended for a minimum of six months.

The in-stent late lumen loss of the second cohort met “our non-inferior criteria,” Grube noted.  For the primary endpoint, the rates were 1.7 in the BioFreedom standard dose arm, 0.22 in the BioFreedom low dose arm and 0.35 in the Taxus arm. Therefore, the BioFreedom standard dose, compared with the Taxus stent met the statistically significance of non-inferiority, with a trend toward superiority.

For the secondary endpoint of the one-year MACE for both cohorts, the rates were 6.1 percent in the BioFreedom standard dose arm, 11.6 percent in the BioFreedom low dose arm and 5.5 percent in the Taxus arm.

“Both BioFreedom standard dose and BioFreedom low dose demonstrated sustained safety up to 12 months, including an absence of stent thrombosis,” Grube reported. “The BioFreedom polymer-free drug-coated stent demonstrated comparable efficacy in inhibiting neointimal hyperplasia (as assessed by independent QCA analysis) compared with the paclitaxel-eluting stent at 12 months."

Grube acknowledged that the BioFreedom would be "intriguing" to compare to the market-dominant Xience V everolimus-eluting stent. At the time this trial began, Taxus was the most commonly used and considered superior among the first-generation stents. 

However, he added that larger trials with longer term follow-up are warranted to confirm these encouraging results.