Bioabsorbable Scaffolds: A Revolution Below the Knee?
Recent and forthcoming trials of bioabsorbable scaffolds were outlined this morning by Eric A. Secemsky, Director of the Vascular Intervention Department at the Beth Israel Deaconess Medical Center in Boston, Massachusetts. An interventional cardiologist, Dr Secemsky was involved in the LIFE-BTK clinical trial,1 which brought the first bioabsorbable scaffold, the ESPRIT DRS (Abbott Vascular) to the U.S. market. “I was fortunate to have a small role in the conduction of this trial and have now had the opportunity to observe the utilization of this technology in clinical practice,” he told LINC Today. “It’s impressive to see how bioabsorbables have emerged as a cornerstone of infrapopliteal intervention in U.S. clinical practice, and I am excited to watch how the expansion of these devices and introduction of novel iterations can change how we perform lower extremity intervention.”
LIFE-BTK was the first landmark trial in the U.S. peripheral vascular space, said Dr Secemsky. “ESPRIT DRS is the only below-the-knee [BTK] scaffold that has a Food and Drug Administration [FDA] indication for primary and provisional stenting.” Getting FDA approval was a challenge, however, following a history of disappointments and failures, primarily in the drug-coated balloon space. “To be able to finally bring an effective device for the infrapopliteal arteries to market through conduction of a successful randomized clinical trial in the U.S. is quite an achievement,” added Dr Secemsky.
Before ESPRIT, balloon angioplasty catheters were the most sophisticated product approved by the FDA in this space. Even so, operators were reticent about implanting anything BTK because of the inherent anatomical challenges, noted Dr Secemsky: “There are a lot of external forces, torsion and compression, and there’s always a concern that you’re taking away vessels that can potentially be bypassed later.” Overall, the goal was to keep this area scaffold-free, he added.
With bioabsorbable scaffolds, however, physicians have been presented with a new treatment option. “There really are no downsides,” stressed Dr Secemsky. “I think integrity, and the ability to prevent against lesion recoil, dissection, or vessel trauma are importantly addressed with this device.”
Indeed, this is what’s driving a lot of the benefits seen in LIFE-BTK. “You have a device that offers important vascular patency early on but will no longer be there in 18 to 24 months,” said Dr Secemsky. “As such, it won’t limit options if patients do need bypass or other treatments down the line.”
Consequently, ESPRIT, a first-generation device, has opened a new field. It has important characteristics that helped it succeed in the trial, including a predictable resorption profile and enough resilience to external compression to allow it to be effective, Dr Secemsky underlined. Subsequent generations of devices are therefore building on the strengths of this first device. “We’re looking at bioabsorbable scaffolds that have thinner struts, have more resilience to compression, and are able to accommodate longer lesion lengths and larger diameters—lesion types that we observe in everyday practice,” he said. “These iterative changes will reflect the devices we will be using in clinical practice for the BTK space.”
Dr Secemsky also spoke about the new generation of devices being tested today. REVA Medical has been trialing the MOTIV Bioresorbable Scaffold in the U.S., for example, and has completed their pivotal trial. Additionally, the Magnitude drug-eluting bioresorbable scaffold, made by R3 Vascular, is about to enter a pivotal trial in the U.S., following its first in-human trial in Austria, Canada, and Italy.2 “Magnitude has the ability to absorb over a predictable amount of time,” explained Dr Secemsky, who is also serving as the principal investigator on the pivotal trial. In addition, the scaffold has more properties that are conducive for the BTK interventional space. “This scaffold has <100-micron strut sizes, longer lengths, as well as improved resilience to external pressure,” he said.
Importantly, Dr Secemsky discussed preliminary data from the RESOLV1 trial, the first in-human data on Magnitude. Based on angiography as well as duplex ultrasound, Magnitude has demonstrated good efficacy, including >90% freedom from restenosis or occlusion at 6 months across patients presenting with many different types of BTK pathology. “We saw very little late lumen loss, very few clinical events, and superb outcomes for a novel scaffold overall,” said Dr Secemsky.
While LIFE-BTK trial focused on shorter, proximal BTK lesions, R3’s platform can advance the lesion subset being treated. “LIFE-BTK was designed for shorter lesions, and the scaffolds only go to 38 mm, so you have to be able to stack them or overlap them if needed,” said Dr Secemsky. “The next stage is to look at these newer devices that can go to 58 mm or even 98 mm in length and can maintain less than 100-micron strut thickness while preserving its radial strength.”
It’s these properties that will make a resorbable scaffold device competitive over the long term, commented Dr Secemsky. “It’s kind of how the coronary market evolved with coronary metallic stents,” he explained, adding that those devices are just starting to make their presence known in clinical practice in the U.S. and even abroad.
The pivotal trial of Magnitude, ELITE-BTK, therefore will build on lessons learned from the LIFE-BTK trial, particularly those related to the regulatory process. “That will help us be effective in getting a second scaffold on the market,” he said. “But the ‘secret sauce’ is not necessarily in the trial, it’s in the technology.”
ELITE-BTK plans to enroll 264 subjects randomized 2:1 to the R3 scaffold vs the standard of care—balloon angioplasty—at 60 global clinical sites. As with typical patients involved in these BTK trials, inclusion will stipulate Rutherford 4 or 5 disease. “That is, rest pain or minor tissue loss, and it’ll be looking at the standard composite endpoints,” noted Dr Secemsky. That will include a combination of limb salvage and primary patency at 12 months (freedom from amputation above the ankle of the target limb, binary restenosis, and target vessel occlusion, as well as clinically driven target lesion revascularization).
The future of bioabsorbable scaffolds, then, will be about dealing with increasingly complex lesions. “We regularly encounter complex lesions that extend the full length of the tibial vessel,” he said. Today, clinicians are forced to leave a lot behind, he went on, but there is hope that the future will hold the right combination of tools to treat all pathology. “We will eventually be entering a clinical environment where bioabsorbables can be deployed for appropriate proximal vessels, and distal disease can be treated with drug-coated balloon angioplasty. We lack all the needed tools to be able to manage the typical tibial lesion in current U.S. practice.”
“We’re still seeing a lot of emerging, newer, longer-term data from clinical trials,” he emphasized. “More devices are going into clinical trials too, so it will be very exciting for the next few years.”
References
1. Varcoe RL, DeRubertis BG, Kolluri R, et al. Drug-eluting resorbable scaffold versus angioplasty for infrapopliteal artery disease. N Engl J Med. 2024;390(1):9-19.
2. ClinicalTrials.gov. Study of the R3 Vascular Drug-Eluting Bioresorbable Scaffold in Treating Below the Knee Arterial Disease (RESOLV I). Available at: https://www.clinicaltrials.gov/study/NCT04912323; accessed January 2025.
