ABSORB trial shows DES is absorbed within two years

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WASHINGTON—Two-year data from 30 patients in Abbott Vascular’s ABSORB clinical trial demonstrate that the company’s bioabsorbable drug-eluting stent (DES) successfully treated coronary artery disease and was absorbed into the walls of treated arteries within two years, leaving behind blood vessels that appeared to move and function similarly to unstented arteries.

Patients experienced no stent thrombosis out to two years and no new major adverse cardiac events (MACE) between six months and two years, according to John Ormiston, MD, principal investigator in the ABSORB trial and medical director at Mercy Angiography in Auckland, New Zealand.

The results were presented Monday at the 20th annual Transcatheter Cardiovascular Therapeutics (TCT) scientific symposium. The results also confirm earlier positive one-year clinical results with Abbott's bioabsorbable DES.

“Clinical safety and effectiveness were sustained at two years, and the previously stented portion of arteries demonstrated the ability to expand and contract in a manner similar to a vessel that has never been stented,” Ormiston said. “These are very exciting results that represent a potential major breakthrough in the future treatment of patients with coronary artery disease.”

Trends were observed in data from tests of artery movement and function, demonstrating a potential restoration of unstented artery movement to coronary blood vessels after the stent was absorbed—something that is not possible with permanent metal-based stent implants, he said.

The ABSORB trial is a prospective, non-randomized (open label) study designed to enroll up to 110 patients in Belgium, Denmark, France, New Zealand, Poland and the Netherlands.

Key endpoints of the study include assessments of safety—MACE (defined as any event that resulted in re-treatment of the treated artery, heart attack or cardiac death) and stent thrombosis (blood clot formation) rates—at 30, 180 and 270 days, with additional annual follow-up for up to five years, as well as an assessment of the acute performance of the bioabsorbable drug eluting stent.

Other key endpoints of the study include successful deployment of the bioabsorbable DES, follow-up measurements assessed by angiography, intravascular ultrasound (IVUS), and state-of-the-art imaging modalities at 180 days and two years.

Two-year data from the first 30 patients enrolled in the ABSORB clinical trial demonstrated a low (3.6 percent, n=28) MACE rate, which was consistent with results at one year (3.4 percent, n=29) and before six-months (3.3 percent, n=30). One patient had a minor heart attack due to lack of blood supply at six-months, another was electively lost to follow up at one year, and one patient died from a non-cardiac cause at two years.

A zero percent stent thrombosis rate persisted for all patients across all time points in the ABSORB trial. Potential restoration of unstented artery movement to coronary blood vessels after the bioabsorbable stent was absorbed was revealed at two years with the drugs acetylcholine and nitroglycerin used in nine patients, showing vasodilation in the previously stented area, and methergine used in seven patients, showing vasoconstriction in the previously stented area.

Abbott’s bioabsorbable everolimus-eluting coronary stent is made of polylactic acid, a proven biocompatible material that is commonly used in medical implants such as dissolvable sutures. The bioabsorbable stent is designed to be slowly metabolized by the body and completely absorbed over time.