Resolute Onyx Fares Well Against Thin-Strut Orsiro Stent in BIONYX All-Comers Study

SAN DIEGO, CA—Resolute Onyx, a thin-strut wire stent designed with enhanced radiographic visibility in mind, fared just as well in a head-to-head trial as another thin-strut stent, with investigators reporting excellent safety and clinical outcomes for both devices.

At 1-year follow-up, the primary endpoint of target vessel failure—a composite that included cardiac death, target vessel-related MI, or clinically indicated target vessel revascularization—occurred in 4.5% of patients treated with Resolute Onyx (Medtronic) and 4.7% of patients treated with Orsiro (Biotronik), which met the statistical definition for noninferiority (P = 0.0005).

The BIONYX study, which was presented during the late-breaking trial session at TCT 2018 and published simultaneously in the Lancet, included 2,516 “all-comers” patients undergoing PCI for acute coronary syndrome and stable angina.

Last year, the Orsiro stent surprised many by being better than the Xience everolimus-eluting stent (Abbott Vascular) in the BIOFLOW V study. Orsiro is a thin-strut stent—60 µm for stents 3.0 mm and smaller—but it has a bioresorbable polymer. Comparatively, the Resolute Onyx stent, which has struts 81 µm thick for devices 4.0 mm or smaller, has a durable polymer.

“The majority of contemporary drug-eluting stents use platforms with a cobalt-chromium alloy, a metal that has limited radiographic visibility,” said lead investigator Clemens von Birgelen, MD, PhD (Thoraxcentrum Twente, Enschede, the Netherlands). “The Resolute Onyx, a zotarolimus-eluting stent, uses a thin, composite wire strut with a dense platinum-iridium core. The core material improves the visibility and allows us to lower the strut thickness.”

To TCTMD, von Birgelen said BIONYX reassures physicians about the clinical safety and efficacy of both stents, but he doesn’t suspect it will shift physicians from one device to the other. Orsiro had been tested in previous randomized clinical trials, and had proven its mettle in multiple all-comers studies, but this is the first all-comers study with the new Resolute Onyx. “It’s surprising because stents do the work,” said von Birgelen, referring to absence of data. “They achieve the result that should be maintained and preserved by drug released from the coating. The stent is essential.”

Making Hay of Stent Thrombosis Rates

In BIONYX, the individual components of the primary endpoint were similar between the two stents. Death from cardiac causes occurred in 0.6% of patients treated with Resolute Onyx and 1.1% of patients treated with Orsiro (P = 0.18). The rate of target-vessel revascularization was nearly identical in both stent arms—3.2% with Resolute Onyx versus 3.1% with Orsiro—as was the rate of target-vessel MI. Interestingly, the risk of stent thrombosis was very low in both groups, but the advantage went to Resolute Onyx. Among the 1,243 patients treated with the thin-wire stent, there was just one case of definite or probable stent thrombosis compared with nine cases in the Orsiro-treated patients (0.1% vs 0.7%; P = 0.01).

Speaking with the media, von Birgelen cautioned that the study was not powered for stent thrombosis and that numbers are small. These results will need to be confirmed in larger clinical studies, he said. However, investigators believe thinner struts, as well as the shape of the stent—a single strand of cobalt alloy is formed into a sinusoid and then wrapped in a helical pattern—could potentially lower the risk of adverse events.

“Thinner struts are known to be better in terms of restenosis and stent thrombosis,” said von Birgelen. “Also, the shallow shape of the stent might facilitate migration of endothelial cells so there could be some advantage. Nevertheless, the advantage we saw here exceeds our expectations by far. We’re dealing with events that are so rare that we must be very careful that a play of chance could play a role.”    

To TCTMD, Sripal Bangalore, MD (NYU Langone Medical Center, New York, NY), noted just one more case of stent thrombosis in the patients treated with Resolute Onyx would have shifted the statistics such that the difference between stents wouldn’t be statistically significant.     

Sunil Rao, MD (Duke University, Durham, NC), who participated in the morning press conference, said the rate of target vessel failure was quite good in both stent arms and agreed with von Birgelen’s take on the rates of stent thrombosis between stents. “As a clinician and a clinical researcher, I probably wouldn’t put a lot of stock in those numbers,” he told TCTMD. “If I had to put an industry hat on, I have no doubt they’ll try to make a lot of hay out of it, but the reality is that these are really small numbers. A few events in either arm would change things.”

That said, Rao pointed out that rapidly decreasing strut thickness is making stents more and more difficult to see on X-ray fluoroscopy. Given the potential technical challenges these newer-generation, thin-strut stents pose when it comes to implantation and postdilatation, “it’s an advantage” to have newly designed stent with enhanced visibility on X-ray fluoroscopy, he said.

David Cohen, MD (Saint Luke’s Mid America Heart Institute, Kansas City, MO), another panelist during the morning press conference, said the Resolute Onyx, which was approved by the US Food and Drug Administration in 2017, is a device used in clinical practice given the enhanced radiographic visibility. “It does help,” he said. “Many of my partners using the previous version of Resolute, which was almost completely invisible, really didn’t enjoy implanting or postdilating it, or retrieving it afterwards.”

Commoditized Stents

Speaking during the press conference, Roxana Mehran, MD (Icahn School of Medicine at Mount Sinai, New York, NY), said it was a little like “back to the future,” with several head-to-head stent studies presented during the opening late-breaking trial session at TCT 2018.

“I think drug-eluting stents are becoming commoditized, which is why we’re seeing a lot of these head-to-head trials,” Rao told TCTMD. “People really want to have some data on which to make a decision. What we’re seeing is a lot of noninferiority. At the end of the day, it comes down a lot to your hospital contracts. I think Xience and Resolute Onyx, as well as Promus and Synergy [both Boston Scientific], are still the fundamental stents being used in the United States.”

The Orsiro stent has CE Mark approval in Europe but is not commercially available in the United States.