Key LIFE-BTK trial findings

Between August 2020 and September 2022, 261 patients at 50 sites in six countries were randomized 2:1 to receive the Esprit everolimus-eluting resorbable scaffold from Abbott or percutaneous transluminal angioplasty (PTA). A total of 173 patients (with 179 target lesions) received the scaffold and 88 patients (with 92 target lesions) were assigned to receive angioplasty. All angioplasties were performed per standard of care. For scaffold implantation, a protocol-prescribed implantation strategy, including lesion pre-dilatation, careful vessel, and scaffold sizing, and post-dilatation of the scaffold was followed. 

Core-lab angiographic assessment demonstrated that 91% of the patients who received the scaffold had successful treatment immediately after the index procedure compared to 70% of the patients who received angioplasty. The primary efficacy endpoint, comprised of a composite of freedom from above ankle amputation in the treated leg, occlusion of the target vessel, binary restenosis of the target lesion, and clinically-driven target lesion revascularization at one year occurred in 135 of 173 patients for the scaffold group and 48 out of 88 patients in the angioplasty group. The Kaplan–Meier estimate was 75% vs. 44%, with an absolute difference of 30 percentage points.

The primary safety endpoint of freedom from major adverse limb events (MALE) at six months and peri-operative death (POD) occurred in 97% patients who received the scaffold and 100% for those who underwent angioplasty. In addition, the powered secondary endpoint of freedom from binary restenosis of the target lesion at one year occurred in 77% in the scaffold group and 49% in the angioplasty group.

The trial also introduced an innovative approach to leg and foot wound assessment, classifying wounds based on etiology and utilizing an iPad-based device to track them over time through photos. This meticulous assessment revealed substantial improvements in wound healing post-revascularization, particularly in patients with arterial insufficiency and various wound etiologie. 

New life for bioresorbable stent technology

The trial focused on the efficacy of a drug-eluting, fully bioresorbable scaffold designed for infrapopliteal lesions. It is based on Abbott's former Absorb stent for the coronaries, which was cleared by the FDA in 2016 and was withdrawn from the market just a year later in 2017 due to poor sales. This was partly due to the thick struts of the device, which made it perform like a first-generation stent rather than a current-generation, thin-strut stent. The technology was redesigned with thinner struts and longer lengths to use in BTK lesions. This area is a hostile environment for stents, so balloon angioplasty has been the front-line therapy.

"The infrapopliteal arteries are incredibly different from coronary arteries. We have long length disease and heavy calcification. When you do angioplasty, they're particularly prone to residual stenosis or dissection that can be flow limiting. So they really do need some sort of mechanical support. Angioplasty works, but you really do need a stent-like result to keep it all open. This is where the bioresorbable scaffold comes in. The thing about this is, you don't want a permanent metallic implant, because if you do put something in there permanently, it acts as an impediment to future surgery or attempts at revascularization," Varcoe said.

He said the new scaffold did an excellent job with helping patients avoid many complications, and has very similar design characteristics of current coronary stents. 

"The Esprit struts are now down to 99 microns, which is equivalent to most modern day coronary DES. The everolimus coating is also important when it comes to bioresorbables. You need to be able to settle down the inflammatory process around the absorption," he explained. 

Bioresorbable stents may fill unmet need for a better device in BTK lesions

Chronic limb threatening ischemia (CLTI) is a severe manifestation of PAD, characterized by ischemic rest pain and non-healing ulceration or gangrene. This serious condition is associated with high rates of amputation and poor quality of life. However, current treatment options for patients suffering from CLTI are limited and are prone to high rates of restenosis. Clinical trials and new devices have sought a device superior to or equal to angioplasty, but the goal has remained elusive. 

Varcoe said PAD affects over 230 million people globally, so it is a serious problem. But, he said the LIFE-BTK trial success has sparked optimism for regulatory approval.

"We've been having conversations with FDA all the way along this process. We've been keeping them well informed ... we recently had a conversation with them where we shared the results. Everyone seems very positive about it. Me personally, as a clinician that deals with a lot of patients with CLI, I can't wait to start using these in my patients. It's going to make a huge difference," Varcoe said.