Study shows Boston Scientific's bioabsorbable-polymer drug-eluting stent yields fewer blood clots than its Promus stent.

Nancy Crotti

EVOLVE II data showed Boston Scientific's Synergy bioabsorbable-polymer-coated drug-eluting stent is safer than the company's Promus Element Plus stent, which is coated with a permanent polymer.

A drug-eluting stent coated with a bioabsorbable polymer may reduce the likelihood of blood clot formation and heart attack one year or more after implantation.

EVOLVE II, a three-year, randomized clinical trial, compared outcomes of patients implanted with Boston Scientific's Synergy bioabsorbable-polymer-coated, drug-eluting stent and the company's Promus Element Plus, which is coated with a permanent polymer. Permanent polymers have been associated with  chronic inflammation, delayed arterial healing, and increased risk of late cardiac events. Resorbable polymers may reduce inflammation and mitigate late/ very-late adverse outcomes.

The study showed that Synergy and Promus were about equally effective, and that Synergy is safer for patients than Promus beyond the first 24 hours after implantation. Three years after implantation, the risk of thrombosis with Synergy is "virtually nil," said international principal investigator Dean J. Kereiakes.

Kereiakes presented the findings at the recent American College of Cardiology scientific session and expo in Washington. FDA approved Synergy in 2015 as the first bioabsorbable drug-eluting stent in the United States, allowing Boston Scientific to beat Abbott to market with such a device. Everolimus, which coats only the interior of the platinum chromium stent, and the polymer, which modulates the drug's release, are fully absorbed after drug elution is complete around three months, according to Boston Scientific.

EVOLVE II enrolled 1,684 patients with an average of 1.3 lesions, including 203 diabetics, noted Kereiakes, medical director of The Christ Hospital Heart and Vascular Center in Cincinnati.

"The EVOLVE II population was the overall most complex demographically and angiographically group of patients ever enrolled in a trial for new stent approval in the U.S.," he added. "This was not easy, simple-lesion types of patients."

One patient developed scar tissue within the Synergy stent 840 days after implantation. Sixty-one days after treatment with a kissing-balloon angioplasty and paclitaxel, the patient developed a blood clot. It was unclear whether the clot was attributable to the Synergy stent, Kereiakes said. Even counting that event, the rate of stent thrombosis was .06% per year, and 0.2% after three years, Kereiakes  noted. He also found Synergy easier to insert and safer for the patient.

"It really is striking," he said. "It makes me comfortable that I can do the case easier. I won't say that I don't worry anymore, but fortunately, the worries are not founded."

The Bio-Resort trial, a one-year study of 3500 Dutch patients in 2016, found that Synergy demonstrated equal results to Medtronic's conventional durable-polymer Resolute Integrity stent, and Biotronik's bioabsorbable, drug-eluting Orsiro stent.

Orsiro is expected to earn FDA approval in 2018. Synergy is more expensive than its durable-polymer counterparts, the Star Tribune of Minneapolis reported in 2016.

Nancy Crotti is a contributor to Qmed.