Paris (FRONTLINE MEDICAL NEWS) – A unique drug-eluting coronary stent showed positive interim results in the DESSOLVE III trial presented at the annual congress of the European Association of Percutaneous Cardiovascular Interventions.

In DESSOLVE III , 1,398 patients undergoing percutaneous coronary intervention were randomized to the widely used Xience everolimus-eluting stent or to MiStent, a novel thin-strut stent with a polymer coating that is quickly absorbed after delivering microcrystalline sirolimus into the vessel wall for prolonged release at a near-linear rate.

At an interim analysis at 12 months of follow-up, the primary endpoint – a composite of cardiac death, target vessel MI, and clinically indicated target lesion revascularization – had occurred in 5.8% of the MiStent group and 6.5% of Xience recipients in the study, which was designed as a noninferiority trial, reported Robbert J. de Winter, MD , professor of clinical cardiology at the Academic Medical Center in Amsterdam.

The overall interim results showing noninferiority were mirrored in all examined subgroups.

“The data support the hypothesis that long-term cytostatic inhibition of early neointima could prevent the late neointimal growth seen at medium and long term with conventional drug-eluting stents,” he said.

MiStent is designed to overcome a shortcoming of conventional drug-eluting stents: namely, their durable polymer coating sticks around after the cytostatic drug is finished being released. It is believed that this residual polymer, which may not disappear for 6-9 months, induces inflammation in the vessel wall, eventually leading to intimal growth, restenosis, and new atherosclerosis.

“The unique feature of the MiStent is that the polymer is bioabsorbable and is fully absorbed at 3 months, whereas the drug is present in the vessel wall out to 9 months, well after the coating has disappeared. So in theory you would expect that any inflammatory response caused by the polymer coating will be counteracted by the drug. This was seen in animal models. And in the DESSOLVE I and II studies, angiographic follow-up showed that late luminal loss was flat after 6 months, in contrast to other drug-eluting stents, which show accrual of late neointimal growth after 6 months to a year,” according to the cardiologist.

DESSOLVE III is planned as a 3-year study. Already by 6 months the curves for target lesion revascularization started to separate, with a 12-month rate of 2.6% in the MiStent group versus 3.8% for Xience. And while this difference is not yet statistically significant, Dr. de Winter and his coinvestigators expect that by 3 years the separation will have grown to the point that the difference becomes statistically significant and clinically meaningful.

The MiStent platform is composed of a cobalt/chromium alloy. The stent strut thickness is only 64 microns, in contrast to 81 microns for the Xience stent. Thinner stent struts have previously been shown to be less injurious to the vessel wall.

DESSOLVE III is an all-comers trial conducted at 20 sites in four European countries. Participants had to have a reference vessel diameter of 2.5-3.5 mm. Roughly 60% of patients had an acute coronary syndrome as their indication for PCI. The study population included, among others, patients with left main coronary artery lesions, restenotic lesions, and failed saphenous vein grafts. Dual-antiplatelet therapy was given for 6 months in patients with stable angina and 12 months for those with ACS, in accordance with European Society of Cardiology guidelines.

Discussant Robert A. Byrne, MD , of the German Heart Center in Munich, declared: “For me, this is a potentially interesting device. It’s the only device where we have a drug elution that’s more prolonged than the polymer, and this does offer the potential for later benefit.”

Dr. Byrne was a member of a European Commission–backed task force that developed European regulatory guidance for the evaluation of new coronary stents. “This MiStent trial program ticks off a lot of boxes: We had a successful first human use study, then we had a modest-size angiographic endpoint study where the late lumen loss looked good, and now we have a clinical endpoint study. This is what we want to see in the regulatory space.”

Another discussant, Chaim Lotan, MD , pronounced the MiStent “definitely another good stent on the shelf.”

It’s impossible to say whether the excellent 1-year outcomes seen with MiStent in DESSOLVE III were due to the prolonged-release microcrystalline sirolimus, the ultrathin stent struts, or both. In any case, the major adverse cardiovascular event rates seen in DESSOLVE III are so low by historical standards that it will become extremely difficult to show superiority for one contemporary drug-eluting stent over another, predicted Dr. Lotan of Hadassah Medical Center in Jerusalem.

Dr. de Winter concurred.

“I think we can now say that the benchmark for present day drug-eluting stents is a target lesion failure rate of about 6% at 12 months and a stent thrombosis rate below 1% at 12 months. It’s going to be increasingly more difficult to improve on that,” he said.

The MiStent, manufactured by Micell Technologies, is commercially available in Europe but investigational in the United States.

DESSOLVE III was sponsored by the European Cardiovascular Research Institute and supported by grants from Micell Technologies and Stentys.

Dr. de Winter reported receiving research grants from OrbusNeich, Abbott Vascular, AstraZeneca, Stentys, and Tryton.