Next-Gen Bioresorbable Scaffold Gets Hesitant Enthusiasm

A second-generation bioresorbable scaffold (BRS) performed angiographically on par with a drug-eluting stent (DES) in the FUTURE-II trial, yet there was little to indicate that this BRS would fare better than the original Absorb.

The thinner-strut, sirolimus-eluting Firesorb was noninferior to the Xience everolimus-eluting metallic stent in terms of angiographic in-segment late loss 1 year after elective percutaneous coronary intervention (PCI; average 0.17 vs 0.18 mm, P<0.0001 for noninferiority), reported Bo Xu, MBBS, of Fu Wai Hospital and the Chinese Academy of Medical Sciences in Beijing.

Xu presented the 433-person FUTURE-II trial during the virtual European Association of Percutaneous Cardiovascular Interventions (EuroPCR) meeting, and a full manuscript was published simultaneously in JACC: Cardiovascular Interventions.

In addition to late loss, Firesorb also matched Xience for the proportion of covered struts at 1 year in an optical coherence tomography (OCT) subgroup analysis of 80 people (99.3% vs 98.8%, P<0.0001 for noninferiority), Xu reported.

Rates of target lesion failure were 0.9% with Firesorb versus 1.9% with Xience by 365 days — growing in both arms to 1.9% and 3.3%, respectively, by 393 days.

“The present trial demonstrated the safety and efficacy of this newer-generation thinner-strut BRS, with a dedicated implantation technique, and may give a new opportunity to the comeback of PLLA [poly-L-lactic acid]-based BRS, with improved physical and mechanical properties,” the study authors wrote.

Firesorb comes in 100- or 125-μm strut thicknesses and is meant to be resorbed in approximately 3 years after implantation.

The device had been designed to overcome the issues that plagued the thicker-strut Absorb, an older BRS that was pulled from the market in 2017 due to unexpected device thrombosis and adverse clinical events at longer follow-up.

Yet the magnitude of late loss with the Firesorb suggests little, if any, improvement over first-generation BRS: Absorb’s late loss had ranged from 0.13 mm to 0.18 mm in the older ABSORB studies, the FUTURE-II investigators noted.

Neither recoil nor device thrombosis was observed in either group at 1 year in the present trial.

“Most physicians believed that [Absorb’s] design could be improved upon, so it is nice to see that a newer thinner device has been tested in a randomized trial. It is promising that there does not seem to be a problem with recoil despite the thickness being reduced to 100-125 (which is two thirds the thickness of Absorb),” commented Cindy Grines, MD, of Northside Hospital Cardiovascular Institute in Atlanta.

Overall, the angiographic, OCT, and clinical outcomes of the Firesorb BRS are “impressive” in this study, said David Cohen, MD, MSc, of St. Francis Hospital and the Cardiovascular Research Foundation in New York City, who was not part of the FUTURE-II group.

“Given the issues seen with earlier generation BRS with thicker struts, both the imaging outcomes and 1-year clinical outcomes are quite reassuring and suggest that the thinner strut design of the Firesorb-BRS may overcome some of these earlier limitations including higher rates of periprocedural MI [myocardial infarction] and stent thrombosis,” he added.

But will BRS make a comeback? It’s hard to say, and the data don’t support a comeback at this time, Grines told MedPage Today.

“Many of the ABSORB events occurred after the 12 month time period. The backbone of Firesorb is designed to be absorbed in 3 years, so we really need longer follow-up and more patients to be sure that the resorption does not disrupt the scaffold and obstruct the coronary lumen,” she said.

“Given the extensive experience we have with current-generation metallic DES, I would want to see some evidence of clinical benefit with BRS prior to incorporating them broadly into my PCI practice,” said Cohen.

Prior research indicates that the window of excess risk for the first-generation Absorb ends after 3 years.

FUTURE-II was an open-label trial that randomized 433 adults to the Firesorb BRS or Xience DES in 2017-2019. Patients, enrolled at 28 Chinese centers and underwent elective PCI on one or two de novo, non-complex lesions.

A higher frequency of post-dilatation during Firesorb placement (96% vs 81%) did not prevent the BRS from being inferior to DES with regards to in-device minimal lumen diameters, diameters stenosis, or acute gain after PCI.

In-segment late loss varied significantly between Firesorb BRS with smaller versus larger diameters such that smaller devices performed worse, Xu’s group added.

These two problems had also been observed with Absorb, Grines noted. “I am not sure that physicians will accept that, unless clinical outcomes are superior.”

Xu and colleagues acknowledged that the study was not powered to detect differences in clinical events. Angiographic follow-up scheduled for 1 year had been delayed in some patients due to COVID-19, the researchers said.

Grines added that significant between-group differences in pre- and post-dilatation may have influenced the results of the trial.

In any case, Xu said at a EuroPCR news conference, FUTURE-II marks a first step to testing the Firesorb in more studies.