Abbott said Thursday it's starting a clinical trial to assess its breakthrough device-designated drug-eluting resorbable scaffold, called Esprit, in the treatment of peripheral artery disease patients with blocked arteries below the knee (BTK), also known as critical limb ischemia.
There are no stents or drug-coated balloons already approved for this indication, Abbott said, adding that its study is the first U.S. IDE trial to evaluate a fully resorbable device.
The announcement comes 10 months after researchers found 91% of patients who received the now-discontinued Absorb BVS to treat BTK arteries were free from clinically driven target lesion revascularization (TLR) after five years. That data appears to have emboldened Abbott to repurpose its bioresorbable scaffold technology — which it stopped selling due to "low commercial sales" and amid evidence it increased the risk of major adverse cardiac events — to target an untapped BTK opportunity pursued by rivals such as BD, Medtronic and Philips.
Balloon angioplasty can spare some people with critical limb ischemia from pain and amputation. However, the vessels can become blocked again. Physicians have explored the use of stents, be they drug eluting, drug coated or bare metal, as a way to keep vessels open but have found some patients then suffer problems including vessel wall effects and incomplete endothelialization. Stenting is also a barrier to future revascularization.
The shortcomings of existing approaches led Abbott to start testing Absorb BVS in BTK patients in 2011. At that time, Absorb BVS was a recently CE-marked product based on a resorbable technology that Abbott thought could treat coronary artery disease without the complications associated with permanent metallic implants.
Six years later, Abbott stopped selling the device against a backdrop of safety concerns but the investigators running the BTK study continued to track patients and provide annual updates on their findings. Last November, the investigators revealed 95% of subjects had sustained clinical improvement out to five years. Ninety percent of patients treated for tissue loss had complete wound healing, with no amputations. No patients suffered late or very late scaffold thromboses, an event linked to the use of Absorb BVS in coronary artery disease.
The data compare favorably to the results of other studies of BTK devices, although differences in the designs of trials mean such comparisons can be unreliable. Intact Vascular, which Philips is set to buy for $275 million, linked its Tack implant to a 83% rate of freedom from clinically driven reintervention at one year. Tack claimed the first FDA approval for a vascular implant used in below-the-knee post-angioplasty dissection repair.
Abbott and Philips are far from the only companies interested in BTK opportunities. BD has sought FDA approval for its Lutonix drug-coated balloon device in BTK applications, but its submission was rebuffed by the agency last year amid a need for additional clinical evidence. Medtronic also remains interested in the market.
Abbott’s clinical trial, LIFE-BTK, is set to enroll 225 patients at sites in countries including Australia, Japan, New Zealand, Singapore and the U.S. and randomize them to receive Esprit BTK or percutaneous transluminal angioplasty. The co-primary endpoints are looking at a composite of limb salvage and primary patency, and freedom from major adverse limb events and peri-operative death.