Boston Scientific, Medtronic tout stent trial results

In a head-to-head trial, Boston Scientific's new drug-coated stent for blocked vessels in the legs — the Eluvia, designed in Maple Grove — did a better job keeping blood vessels open after a year than an industry standard stent for treating peripheral artery disease.

Meanwhile, Medtronic's advanced "workhorse" cardiac stent, the Resolute Onyx, was proved to work just as well as a competitor device that has a specialized drug coating during another head-to-head trial, this one featuring 2,500 patients and an independent, noncorporate sponsor.

Medtronic's Resolute Onyx went on the U.S. market last year, while a decision is expected soon from the Food and Drug Administration on whether the Eluvia from Boston Scientific will be approved in the U.S. The clinical trial results for both devices were announced Saturday at the annual Transcatheter Cardiovascular Therapeutics (TCT) meeting in San Diego.

The two randomized clinical trials pitted devices from companies with large Minnesota operations against similar devices that are already widely used the market. Such "head-to-head" trial designs are relatively uncommon in health care, but there is growing emphasis on the evidence they can provide.

"Head-to-head comparisons comprise a very small proportion of the industry-sponsored clinical trials agenda," Italian researchers wrote in the Journal of Clinical Epidemiology in 2015. "However, comparative evidence from head-to-head randomized comparisons may be indispensable to capture the relative benefits and harms of alternative interventions."

Boston Scientific's president of peripheral interventions, Jeff Mirviss, said the Imperial study examining the performance of the Eluvia leg stent vs. the Cook Medical Zilver PTX leg stent was a first for peripheral stents used in the legs. Although the trial's primary goal was only to confirm that the Eluvia was "noninferior" to the Zilver, the statistics came back showing statistical superiority.

"I believe that is what hospitals and physicians want to see, in order to make evidence-based medicine decisions," Mirviss said. "We're showing statistically significantly superior results when it comes to the primary patency rate."

The Eluvia group recorded one major adverse event — a limb amputation — and one stent fracture among 309 patients. The Zilver had neither of those among 156 patients. But the Zilver had double the rate of early stent blockage known as "stent thrombosis," at 4 percent vs. 1.7 percent for the Eluvia. The study authors found what they called "significant symptomatic, functional, and hemodynamic improvement" with both devices after a year.

Mirviss attributed Eluvia's better performance in patency to its special drug coating, which was designed and partly manufactured at Boston Scientific's campus in Maple Grove.

The Eluvia is coated with a polymer that releases an anti-inflammatory drug at a predictable rate over time to prevent the vessel from re-closing over the course of a full year. The Zilver PTX is also a drug-eluting stent, but it doesn't have the polymer.

"We took the polymer from our coronary [drug-eluting stent] and applied it to the peripheral stent," Mirviss said. "The technology is very tunable, so you can make the drug come off very quickly, or slowly."

The study was sponsored by Boston Scientific and conducted at dozens of sites around the world, including the Mayo Clinic in Rochester and Allina Health's Mercy Hospital in Coon Rapids. Imperial was the study Boston Scientific ran to try to gain FDA approval for the device.

The device was put to the test in a head-to-head comparison the Bionyx trial. The results, revealed Saturday at TCT, showed that the Resolute Onyx had roughly the same low rate of "target vessel failure" as a European competitor stent after one year among a relatively large group of patients who were randomized to get one of the devices.

The study's sponsor, a health care provider called Thorax Centrum Twente, set out to study the Resolute Onyx, which has a permanent drug-eluting coating, vs. Biotronik's Orsiro stent, which has a coating that completely disappears over time. The study came about in response to concerns among doctors that non-biodegradeable coatings like the Resolute Onyx' could trigger tissue inflammation.

After testing the two stents in almost 2,500 people, the study documented target vessel failure in 4.5 percent of the Resolute Onyx patients, vs. 4.7 percent of Orsiro patients.

"We have yet to see any meaningful clinical benefit with the introduction of biodegradable stent technologies," Medtronic coronary Vice President Dave Moeller said in a statement. "We are pleased to see that the combination of visibility [on medical imaging], thin struts, conformability, and biocompatibility resulted in a very low stent thrombosis rate in this study."

Joe Carlson • 612-673-4779