AT THE AHA SCIENTIFIC SESSIONS
CHICAGO (FRONTLINE MEDICAL NEWS) – A drug-eluting coronary stent with a bioabsorbable polymer that dissolves nearly completely by 4 months after placement proved noninferior for safety and efficacy, compared with a conventional drug-eluting stent for 1 year, in a pivotal U.S. study with 1,684 patients.
If this new drug-eluting coronary stent, Synergy – which uses a bioabsorbable polymer to hold and slowly release the stent’s antirestenosis drug everolimus – were to receive Food and Drug Administration approval in 2015 based on these pivotal trial results, it would become the first such stent on the U.S. market. Some experts hailed the Synergy stent as an incremental improvement over prior devices in its combination of excellent deliverability as well as the ability of the stent’s drug-carrying polymer to vanish once it’s no longer needed, a feature that in theory could reduce the risk for late stent thrombosis and thereby reduce the necessary duration of dual-antiplatelet therapy (DAPT).
“We need to continue to evolve [stents] by improving and enhancing them and reducing the period of mandatory DAPT during the first year” following stent placement, commented Dr. Roxana Mehran , a professor of medicine and interventional cardiologist at Mount Sinai Hospital in New York. The Synergy everolimus-eluting stent with a bioabsorbable polymer is “a little step in the right direction,” she said as designated discussant for the study when its results were reported at the American Heart Association Scientific Sessions.
But others questioned the added value of a new stent that merely shows noninferiority but not superiority to comparator stents when it comes to preventing late stent thrombosis. “The major difference we’ve seen in the different bioabsorbable polymer stents is in their deliverability, which keeps getting better,” said Dr. Christoph Kaiser , professor and head of interventional cardiology at the University of Bern, Switzerland.
EVOLVE II
The EVOLVE II trial enrolled patients who required percutaneous coronary intervention (PCI) with at least one stent at 125 centers in 16 countries during November 2012–December 2013. The investigators randomized patients to PCI with either the Synergy stent or the Promus Element Plus everolimus drug-eluting coronary stent that uses a durable polymer to hold and release everolimus. A third of the patients had unstable angina, and more than a quarter had an acute myocardial infarction. Virtually all patients were on DAPT for at least 6 months, and more than 85% were still on DAPT at 12 months.
After 12 months of follow-up, the combined rate of cardiac death, myocardial infarction caused by a lesion in a stented artery, or ischemia-driven target-vessel revascularization – the trial’s primary endpoint – was 6.7% in patients who received the stent with a bioabsorbable polymer and 6.5% in the durable-polymer stent, a nonsignificant difference that met the trials prespecified definition of noninferiority, reported Dr. Dean Kereiakes , lead investigator for the study and medical director of the Christ Hospital Heart and Vascular Center in Cincinnati.
The safety analysis showed a small but statistically nonsignificant reduction in episodes of definite or probably stent thrombosis, with three such events occurring among the patients who received a bioabsorbable-polymer stent and five in patients who received a durable-polymer stent. “We would need a trial with 20,000 patients to prove superiority” of the bioabsorbable-polymer stent for an endpoint of late stent thrombosis, Dr. Kereiakes said.
The only statistically significant difference in outcomes reported in the EVOLVE II trial between the two stent types tested was in immediate procedural success, which occurred in 98.3% of patients treated with the bioabsorbable-polymer stent and in 96.9% of those treated with a durable-polymer stent, a 1.4% absolute difference.
“As a high-volume operator doing complex cases, the [Synergy] stent is more deliverable and user friendly, with a lower profile and more flexibility. It makes complicated cases easier,” Dr. Kereiakes said.
These technical advantages “will resonate with the interventional community,” commented Dr. Robert Harrington , professor and chairman of medicine and an interventional cardiologist at Stanford (Calif.) University.
Results from a second, similar study that used different bioabsorbable- and durable-polymer stents and reported at the same session showed largely similar results.
BASKET-PROVE II
The BASKET-PROVE II (Basel Stent Kosten Effektivitäts Trial-Prospective Validation Examination Part II) trial randomized 2,291 patients at any of eight centers in four European countries. Patients received a biolimus-eluting stent with a bioabsorbable-polymer ( Nobori ), an everolimus-eluting stent with a durable polymer ( Xience Prime ), or a bare-metal stent ( PRO-Kinetic ), and were followed for 24 months.
The study’s primary efficacy outcome was the same as in EVOLVE II, a combination of cardiac death, myocardial infarction, or need for target-vessel revascularization, but in this study, it was tallied after 24 months. The rates were 7.6% in patients who received stents with a bioabsorbable polymer, and 6.8% in those who got stents with a durable polymer, a difference that was not statistically significant, and which also met the study’s prespecified definition of noninferiority in the intention-to-treat analysis.
The study’s safety endpoint compared patients who received bioabsorbable-polymer stents with those who received bare-metal stents for rates of cardiac death, myocardial infarction, or definite or probable stent thrombosis, which occurred in 5.0% of patients who received bare-metal stents and in 3.7% of those who received stents with a bioabsorbable polymer, a difference that was not statistically significant. Notably, the rates of stent thrombosis during months 13-24 of follow-up were completely identical in patients who received the drug-eluting stent with a bioabsorbable polymer and in those who received bare-metal stents, reported Dr. Kaiser, a coprincipal investigator on the study. Concurrent with his report at the meeting, an article with the results appeared online (Circulation 2014 [ doi:10.1161/CIRCULATIONAHA.114.013520/-/DC1 ]).
These findings “challenge the concept” that polymers are a key issue for any difference in the rate of late stent thrombosis, said Dr. Kaiser.
But another interventionalist, who cochaired the session where the results from both studies were reported, disagreed. “I think it is a step forward to get rid of the polymers. There is no use to having them” once the antirestenosis drug a stent carries is fully released, “so it is good to get rid of them,” said Dr. Stefan James , a cardiologist at Uppsala University in Sweden.
“In our registry [ Swedish Coronary Angiography and Angioplasty Registry ] we see that the [Synergy] stent has excellent results, with a very low stent thrombosis rate similar to what was shown” on the EVOLVE II trial. “So I think that the [bioabsorbable-polymer] stents are a step forward. After 20 years with drug-eluting stents, we are improving these devices step by step,” Dr. James said.
EVOLVE II was sponsored by Boston Scientific. Dr. Kereiakes is a consultant to and speaker for Boston Scientific, and a consultant to Abbott Vascular and Reva Medical. Dr. Mehran has received honoraria from and has been a consultant to Boston Scientific as well as to several other device and drug companies. Dr. Harrington had been an investigator for several trials that tested drugs patients take following stenting. The BASKET-PROVE II trial had no commercial sponsorship, but the study organizers received the prasugrel that patients took in the study following stenting for free from the manufacturers. Dr. Kaiser has received remuneration for being the advisory boards for Eli Lilly and Daiichi Sankyo. Dr. James had served on an advisory board for Medtronic and has received institutional research grants from Medtronic, Terumo, and Vascular Solutions.
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