Australian patients with peripheral arterial disease could soon have access to a new type of stent called Esprit BTK, a mechanical scaffold designed to be inserted into blocked lower leg arteries.
The scaffold, developed by a team from the University of NSW and the Prince of Wales Hospital, is made from poly-l-lactic acid, which safely dissolves in the body over 18-24 months, and is coated with everolimus, a drug that prevents the blood vessel from narrowing.
Lead author, Associate Professor Ramon Varcoe, from UNSW Medicine & Health and PWH, said that in a phase 3 randomised clinical trial, Esprit BTK was shown to be more effective than the current standard procedure, with the treated blood vessels more likely to remain open, reducing the need for limb amputation.
“The Esprit scaffold gives mechanical support to the recently opened artery, it delivers a drug to the blood vessel wall that prevents re-narrowing, and then it dissolves, leaving nothing behind to irritate the blood vessel and induce scar tissue formation,” Associate Professor Varcoe said.
“This is a useful quality as the artery only needs to be held open for a limited time to restore blood flow and resolve the blockage. It also avoids burning bridges should the patient require bypass surgery in the future.”
During the trial, 261 patients with CLTI and infrapopliteal artery disease were randomly assigned in a 2:1 ratio to receive treatment with an everolimus-eluting resorbable scaffold or angioplasty.
“The primary efficacy end point was freedom from the following events at one year: amputation above the ankle of the target limb, occlusion of the target vessel, clinically driven revascularization of the target lesion, and binary restenosis of the target lesion,” Associate Professor Varcoe said.
No events occurred in 135 of 173 patients in the scaffold group (74%) and 48 of 88 (54%) patients in the angioplasty group.
“The primary safety end point was freedom from major adverse limb events at 6 months and from perioperative death… and was observed in 165 of 170 patients in the scaffold group and 90 of 90 patients in the angioplasty group,” Associate Professor Varcoe said.
Serious adverse events related to the procedure occurred in only 2% of the patients in the scaffold group and 3% of those in the angioplasty group, with the results recently published in the New England Journal of Medicine.
Associate Professor Varcoe was hopeful that the device would be approved for widespread use in Australia by the TGA to expand the treatment options for patients suffering from PAD, which most commonly affects the lower limbs and involves the build-up of plaque in the peripheral arteries, which in severe cases leads to chronic limb-threatening ischemia.
Patients with CTLI experience severe pain, gangrene, non-healing ulcers and may require limb amputation, with poor survival rates, and while there is no national data for Australia, according to the AIHW, PAD was the primary cause of almost 60,000 hospitalisations in 2020-21.
“The prognosis after amputation is worse than most cancers,” Associate Professor Varcoe said.
“Currently, we use angioplasty, but this has no mechanical scaffolding properties and usually doesn’t stay open very long, and on many cases, after balloon angioplasty, the treated blood vessel becomes narrower, and the balloon doesn’t stay inflated for long enough, resulting in the blood vessel becoming blocked again over time.”
Following the success of the Phase 3 RCT, the researchers are working to make Esprit BTK available for patients in multiple countries and the stent will be submitted to the Food and Drug Administration for approval in the US initially, followed by further submissions in Europe, Japan, and Australia.
“Once approved, I expect it will become the standard of care,” Associate Professor Varcoe concluded.