Abbott presented mixed results from the latest trial of its bioresorbable stent at the American College of Cardiology meeting Saturday. The FDA warned care providers of a higher rate of cardiac events in patients receiving the Absorb stent compared to those treated with a drug-eluting metal stent.
At ACC, Abbott presented data from its ABSORB III trial, which pitted the Absorb GT1 Bioresorbable Vascular Scaffold against Abbott’s Xience drug-eluting metal stent. Between one and two years post-implantation, there was “no statistically significant difference” in rates of target lesion failure (TLF)—an endpoint that includes cardiac death, heart attack and the need for another procedure to re-open the artery, according to Abbott. The TLF rate for Absorb was 3.7%, while the rate for Xience was 2.5%. Stent thrombosis—blood clotting near the stent, which can block blood flow—for Absorb was low, at 0.3%, compared to 0% for Xience.
However, cumulative two-year TLF rates were higher for Absorb (11%) than for Xience (7.9%). The higher rates of adverse events were more likely in patients who had the Absorb stent placed in small arteries, the FDA said.
The Absorb stent earned FDA approval in 2016 and is indicated for the treatment of coronary artery disease. CAD, where cholesterol deposits accumulate along arterial walls and reduce blood supply to the heart, is usually treated with a metallic stent, which is placed to prop an artery open. But these stents are permanent and carry a risk of scar tissue forming and causing the artery to narrow again.
The Absorb stent supports the artery and elutes a drug that reduces inflammation and scar tissue formation. The stent reabsorbs once it’s helped the artery heal, usually within three years of placement, according to Abbott. The Absorb stent has instructions to avoid using the device in "very small arteries."
The ABSORB III trial launched in 2012, four years before approval. Implantation technique has changed in the intervening time, Abbott said.
“The FDA is working with Abbott Vascular, Inc. to conduct additional analyses to better understand the cause(s) of the higher cardiac event and device thrombosis rates in patients treated with BVS compared to the XIENCE stent,” the agency said in its letter. “The FDA will continue to monitor the performance of the BVS in ongoing clinical studies and in reports submitted to FDA through MedWatch.”
“The FDA’s letter to healthcare providers emphasized the importance of following instructions for use when implanting Absorb,” Abbott said in a statement. “When implanted in appropriately sized vessel sizes and following current instructions for use, the results for Absorb are comparable to the leading metallic drug-eluting stent—with the added feature of leaving no metal behind once it dissolves.”