U.S. stent market: Steps to shedding the metal start in Cincinnati

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 - Stent

Two ongoing trials are looking to make strides on the U.S. market to use less metal in cardiac stents—one with thinner metal struts and a bioabsorbable polymer drug-eluting stent (DES) and the other with an entirely bioabsorbable stent. Dean J. Kereiakes, MD, of The Christ Hospital in Cincinnati, who serves as principal investigator for both trials, spoke with Cardiovascular Business about the varied trial designs and stent profiles, including a few caveats.

First, Kereiakes, medical director of the Lindner Research Center at The Christ Hospital, explained that the ABSORB trial, a pivotal trial for FDA approval, is seeking to enroll approximately 2,250 patients, the majority in the U.S. This randomized, controlled study will compare the performance of the Absorb Bioresorbable Vascular Scaffold (BVS, Abbott) with Xience metal-platform DES.

Dean J. Kereiakes, MD, speaks about the ABSORB trial and bioabsorbable stents from TriMed Media Group on Vimeo.

Of those 2,250 patients, 50 patients are included in the study roll-in phase using a single size (3.0 mm diameter X 18 mm length) BVS device. Also, 200 patients will be treated with BVS (nonrandomized) in an imaging substudy, with serial late imaging (angiography, intravascular ultrasound, optical coherence tomography). Then, 2,000 participants will be randomized to receive either BVS or Xience DES. In the randomized phase of the trial, patients may have up to two lesions in two separate vessels treated with lesion lengths of up to 24 mm.   

The primary endpoint of ABSORB is target lesion failure (cardiac death, target-vessel MI or clinically indicated target-lesion revascularization [TLR]) at one year—the same endpoint in the SPIRIT trials, which were used to evaluate Xience. The hypothesis, according to Kereiakes, is that BVS will not be inferior to Xience at one year with respect to the incidence of target lesion failure.

“This one-year endpoint will be used to submit for FDA approval, and will be followed by a landmark analysis between years one and five to evaluate late adverse events which are predicted to diverge in favor of BVS,” said Kereiakes. “Ischemic-driven TLR and stent thrombosis should be far less with  the BVS patients.”

Also, he added that if the device is gone (absorbed), there would be no risk of stent fracture, which has been observed in at least 2 to 3 percent of Xience DES in in the late-term follow-up. Also, the problems with stent erosion may eliminated.

However, the Absorb BVS may not be appropriate for all patients, including those with heavy calcification. “The Absorb is a thick strut device at 59,000 of an inch, compared with the Synergy stent, which is 29,000 of an inch, or the Xience Expedition, which is 32,000 of an inch,” Kereiakes said. “Also, having implanted a few of these devices, it does not feel like a high-performance device, meaning one used to treat torturous and complex coronary anatomy.”

He pointed to research being conducted outside of the ABSORB trial that is evaluating the use of  these stents in complex coronary anatomy following adequate pretreatment of the vessel. “In patients with complex anatomies, operators really need to take the time to adequately dilate the veessel prior to deploying the BVS device. We really don’t know what type of impediment that calcium will present. To be a workhorse device, BVS has to perform.”

Concomitantly with the ABSORB trial, the EVOLVE II trial, for which Kereiakes also is the principal investigator, is seeking to enroll approximately 2,000 patients at up to 160 sites worldwide, including the U.S., Canada, Europe, Australia, New Zealand, Japan, India, Brazil and Singapore. The first patient was enrolled at the Christ Hospital in November 2012. Researchers will follow enrolled patients for five years.

“We at Christ Hospital have placed 19 of the 74 Synergy stents that have been deployed to date in EVOLVE with 10 active centers, and we have placed four of the five Absorb stents deployed in the U.S. to date” Kereiakes added.

The Synergy stent, which received CE Mark approval in October 2012, uses the everolimus drug and features a thin bioabsorbable polymer coating, which is completely absorbed shortly following the end of drug elution, at three months.

Synergy an “excellent performing, flexible device, with a low profile,” Kereiakes said. “I have taken some liberty with the Synergy stent in complex anatomy, and it performs well. Conversely, with Absorb, we have been limited to relatively simple anatomy by protocol. Although both (ABSORB and EVOLVE) protocols require target lesion predilatation before stent deployment, Synergy is likely to eventually be used for primary stenting (without predilatation) after it is approved but the Absorb BVS will not.”

“The Absorb BVS will probably be approved with the caveat of adequate/definite pretreatment of the target lesion before deployment of the device. Most of the work with BVS is front-loaded in vessel preparation and there is often no need to postdilate. Conversely, with metal-platform stents, there is minimal upfront work, but they  require postdilation more often.”

While no one can predict decision or timelines made by the FDA, these trials likely may allow for a more diverse stent market in the U.S.