Three reasons to be optimistic about bioresorbable stents

by Eric Distad, Senior Director, Medical Device & Diagnostics, Novella Clinical

In a December 2015 blog post, I quoted a report by Technavio stating that bioresorbable coronary stents would be a key technology to watch over the next five years. Those in clinical development are either made of lactic acid polymers or use magnesium-based scaffolds, which break down naturally. More than a dozen companies have programs developing such products, which Forbes recently described as “the science-fiction-like promise to return damaged arteries to their natural state.” Two of these devices have CE mark, and both are working toward FDA clearance.

The appeal is clear. Bioresorbable alternatives to metal stents promise the same medical benefits but degrade naturally in blood vessels to leave behind a healed artery instead of hardware. Though little is known about the late-stage outcomes of patients with bioresorbable stents, gathering evidence points to an optimistic future. Here are three of those reasons below, including what to look forward to:

1. Complete healing. Dr. Robert Byrne of Deutsches Herzzentrum München in Munich, Germany told Medscape in 2015 that the area occupied by a bioresorbable stent “after 5 years or so is not discernably different from the surrounding tissue.” This is remarkable, considering that inhibited vasomotion after stenting has been a stubborn obstacle facing individuals living with a metal stent. After traditional stenting, the blood vessel never regains its full ability to move or dilate, whether for further surgical intervention or in response to changes in blood flow. Incomplete healing can also lead to a chronic inflammatory state, which might increase the risk of blood clots. And although stents have vastly improved coronary health for people who need them, in some cases they become focal points for future adverse conditions. Such conditions include arterial thickening and reclosure of the blood vessel.

What to look forward to: Current bioresorbable models degrade in two to four years, even though full vasomotion in theory can be recovered in 12 months. That’s not to say vasomotion is the only factor when determining a time frame for scaffold degradation, but expect companies to continue to refine and identify the ideal timing – long enough to ensure complete healing and prevent occlusion and restenosis but short enough to maximize this advantage over traditional materials. Also, differences in long-term outcomes are still being researched. Studies of 5-year outcomes which could corroborate Dr. Byrne’s observations are still pending, and results aren’t expected until 2020.

2. Enhanced imaging. Metal stents can disrupt some imaging techniques, most notably CT, which has historically limited post-procedure evaluation. Materials developed for bioresorbable stents, on the other hand, present no such problems, and reports of both clear multi-slice CT and angiography show that the new technology will expand care providers’ options for evaluating the implant site.

What to look forward to: In one sense, bioresorbable technology works too well – providers may reasonably want to evaluate the site of an implanted stent after it has degraded. One solution presented has been to provide a long-term reference point by including small, platinum studs that remain in place after the scaffold has degraded.

3: Thinner, stronger struts. Conventional stents have not yet relinquished their title for strength, but advances have brought bioresorbable devices very close to the standards set by their predecessors. Metal struts are typically around 80 microns thick. Their CE-marked bioresorbable counterparts, by contrast, are 100-150 microns, and are getting thinner with each successive iteration. These new stents also lag standard metal stents in their ability to minimize recoil after placement. The difference in profile chiefly impacts their use in very small blood vessels. Of course, metal stents have decades of R&D to credit for their remarkable design and, as bioresorbable stents have been doing, followed a path to become thinner, safer and more versatile. The fact that bioresorbable stents have advanced so quickly gives plenty of reason to believe they will close the “bulkiness” gap over the next several years.

What to look forward to: Clinical applications will depend on what limitations new stents may or may not have, and will continue to be reevaluated as we see new improvements and new devices hit the market. As with any technology, a truly universal tool for vascular intervention is unlikely, and we will need continuous research to determine the best place for these scaffolds in the clinic. Some initial reports suggest bioresorbable stents might be particularly useful for bifurcation lesions – where injury has arisen on both branches at a junction of blood vessels – or where there is extensive injury along a long stretch of blood vessel. While some interventional cardiologists predict that bioresorbable stents will completely replace traditional technology, the more likely scenario is that physicians will use one or the other depending on the patient’s needs.

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Eric Distad, Senior Director, Medical Device and Diagnostics Division at Novella Clinical. Mr. Distad has over 17 years’ experience in all facets of clinical research including 13 years in medical device clinical research, ranging from one of the top three medical device companies to startup companies. Geographically, he has significant experience managing trials in the United States, Canada, Europe, and Hong Kong/China. He can be reached at edistad@novellaclinical.com.

The opinions expressed in this blog post are the author’s only and do not necessarily reflect those of MassDevice.com or its employees.

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