FDA Advisory Panel Backs Approval of Abbott Bioresorbable Stent

Patrice Wendling

March 15, 2016

GAITHERSBURG, MD — A US Food and Drug Administration (FDA) advisory panel gave near-unanimous support for approval of the Absorb GT1 bioresorbable vascular scaffold (BVS) system (Abbott Vascular).

If approved, Absorb would be the first drug-eluting coronary stent in the US with a fully resorbable vascular scaffold.

"I do believe this is a novel breakthrough technology for patients undergoing PCI," Circulatory System Devices panel member Dr Ralph Brindis (Oakland Kaiser Medical Center, San Francisco, CA) said.

Panel chair Dr Richard Page (University of Wisconsin-Madison) commented, "The holy grail is the idea of putting in a stent that stays open, elutes a drug to keep it open, and then disappears. People have been talking about this sort of thing for the past 2 decades as far as I'm aware, and I consider the technology potentially transformative."

Absorb BVS has a standard delivery system, but differs from other drug-eluting stents in that it has a polymeric scaffold that absorbs within about 36 months. Thus patients also aren't locked into a lifelong metal stent or, as is often the case, multiple stents, and their associated adverse events.

The proposed indication for Absorb BVS is to improve coronary luminal diameter in patients with ischemic heart disease due to at least two de novo coronary artery lesions (length 24 mm) with a reference vessel diameter (RVD) of ≥2 mm and ≤3.75 mm. 

The panel voted on the safety (9 yes, 1 nay), efficacy (10 yes, 0 nay), and risk/benefit profile (9 yes, 1 abstain) of Absorb based on data from the ABSORB III study.

As previously reported by heartwire from Medscape, the pivotal ABSORB III trial showed similar rates of target lesion failure at 1 year between Absorb and Abbott's latest-generation everolimus-eluting stent (Xience). Rates of cardiac death, MI, and stent thrombosis were numerically higher in the BVS group.

Dr Warren Laskey (University of New Mexico, Albuquerque, NM) said he felt comfortable with the decision making overall but voted nay for the safety because of the noninferiority study design composite end point and "various components going in the wrong direction."

Questions were also raised by the panel over whether the study's 4.5% noninferiority margin was too generous.

Several panel members and FDA representatives expressed safety concerns for Absorb BVS for small vessels. About half of scaffold thromboses occurred in small vessels.

Abbott proposed adding a warning to the label against implanting a BVS in vessels with an RVD of <2.5 mm and a precaution statement strongly recommending online quantitative coronary angiography or intravascular imaging for small vessels visually assessed as as ≤2.75 mm.

Panel members also suggested tweaking the warning and precaution language, making the warning a boxed warning, and adding information on use in diabetics.

ABSORB III principal investigator Dr Gregg Stone (Columbia University Medical Center, New York, NY) told the panel that use of Absorb BVS in Europe has imparted several lessons, such as more careful vessel sizing and routine postdilation that have dramatically reduced thrombosis rates. This is reflected in ABSORB IV and the recent MICAT study.

"I think we've shown that there is reasonable effectiveness; we just have to ensure that it is implanted in the right patients," he added.

Abbott is also strongly recommending routine postdilation and will require mandatory comprehensive education and training during a phased commercial roll-out to take place over 1 year. Education would include three online training modules, in-person education with Absorb experts, and monitoring for the operator's first three to five cases.

ABSORB III was funded by Abbott Vascular. Stone was a principal investigator for ABSORB III.

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