ABT Abbott Laboratories

For nearly 15 years, Abbott Laboratories has been developing a new type of stent made of biodegradable material that gradually disappears after restoring blood flow to the heart. The device has been closely watched by physicians for its potential to improve on currently available stents by reducing long-term complications of coronary artery disease.

In a large clinical study presented Monday, Abbott's device showed mixed results. The stent, called Absorb, performed about as well as an already marketed stent at preventing deaths, heart attacks and repeat stent procedures. Some 7.8% of patients who received Absorb experienced such events, compared with 6.1% of patients in the control group. Though the rate was numerically higher with Absorb, the difference was small enough that the device was shown to be statistically noninferior.

Abbott's device failed to show a significant advantage on other measures, including a reduction in chest pain, after one year.

The study data were presented Monday at the annual Transcatheter Cardiovascular Therapeutics conference, and published simultaneously in the New England Journal of Medicine. Abbott funded the study, which is intended to support U.S. regulatory approval of the device.

Charles Simonton, vice president of Abbott's vascular division, attributed the device's numerically higher rates of events like heart attacks to "variability you see in any trial." Over time, he said, Abbott expects the stent to provide significant improvement to patients if it makes it to market, including a reduced need to take blood thinners.

"We're going to have to prove that with long term data," Dr. Simonton said. "But there's an intuitive element of this that many patients and doctors already understand, and I think that's going to drive a lot of the adoption."

The techniques used to implant the device are more challenging than with other stents, wrote Robert A. Byrne, cardiologist at the German Heart Centre in Munich, in an editorial accompanying the study results in the New England Journal of Medicine. Selecting the appropriate patients to receive the Abbott stent is also complex, he said.

"Although the concept of self-degrading stents is intuitively attractive, promise alone is not enough to make us unconditionally embrace this technology," Dr. Byrne wrote.

Stents are tiny metal tubes that help prop open clogged arteries to help restore the flow of blood to the heart, and reduce the risk of heart attack. It is estimated that one million Americans annually are implanted with the devices.

The world-wide market for drug-eluting stents is projected to reach $3.82 billion in global sales this year, according to EvaluateMedTech. About a third of global sales come from the U.S.

Abbott's stent is made of polylactic acid, and is gradually broken down by water contained in body tissue, said Dr. Simonton. Patients' blood vessels gradually absorb the material, and the stent completely disappears in about three years, he said.

Blood clotting is a rare, but serious side effect associated with current stents. It has been hypothesized by some physicians that the Absorb stent, by dissolving over time, could reduce the risk of blood clotting. But in the study presented on Monday, some 1.4% of patients receiving the Absorb stent experienced blood clotting, compared with 0.7% of patients receiving a currently available stent. The difference wasn't statistically significant.

The study data will make it difficult to compel many doctors to choose Absorb, if it is approved, over current stents, which are generally thought to be effective and safe, said Sanjay Kaul, a cardiologist at Cedars-Sinai Medical Center in Los Angeles, who wasn't involved in the study.

"Unless Absorb offers some tangible evidence of benefit in terms of cost, convenience, or complications including stent thrombosis, why would I bother putting it in my patients?" Dr. Kaul, who has consulted for Abbott competitor Biotronik SE, said in an email.

Write to Joseph Walker at joseph.walker@wsj.com

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(END) Dow Jones Newswires

October 12, 2015 15:45 ET (19:45 GMT)

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