Oct. 16 (Bloomberg) -- Medtronic Inc.'s drug-coated heart stent Endeavor had more complications than Johnson & Johnson's rival device to prop open arteries and didn't reduce the need for future treatment.

The research presented at the Transcatheter Cardiovascular Therapeutics conference in Washington, D.C., raises questions about Endeavor's safety, which had been considered the device's edge in the intense battle for the $4 billion worldwide market for drug-coated stents. Medtronic is trying to revive Endeavor's sales, which slumped after Abbott Laboratories' Xience won U.S. approval in July and captured half the American market.

``Medtronic has done a good job promoting its safety, and this certainly calls that into question,'' said Alexandra J. Lansky, director of the Women's Health Initiative at the Cardiovascular Research Foundation, in an interview after she moderated a press conference about the findings today.

Lansky, a cardiologist at New York-Presbyterian Hospital- Columbia University Medical Center, said she would no longer choose Endeavor as a first option for her patients based on what she called the ``sobering results.''

Medtronic's shares fell 83 cents, or 2 percent, to $40.01 at 4 p.m. in New York Stock Exchange composite trading. The company sank 15 percent after the study was presented, then rose with the overall market.

Possible Explanations

The study, with two others presented today at the medical conference, is ongoing and may have been skewed by blood-thinning drugs or by sicker patients receiving Medtronic's version of the mesh sleeves aimed at keeping arteries open, said Jens Flensted Lassen, lead investigator in the trial named Sort-Out III.

The study results aren't likely ``a major game-changer'' because of the caveats, said Rick Wise, a Leerink Swann & Co. analyst in New York, in a note to clients. Still, the research is likely to cost Medtronic sales, said Jan David Wald, a Stanford Group Co. analyst in Boston, today in a telephone interview.

``To the extent that Medtronic has been making such a strong claim on safety, you know it can't help them, and it can't make investors and doctors feel more confidence about using their stent,'' Wald said.

Patients getting Endeavor had more heart attacks and deadly stent thrombosis blood clots than those getting Johnson & Johnson's older drug-coated Cypher stent, the registry of more than 2,000 patients treated in Denmark found. They also were more likely to have arteries that re-clogged and required additional treatment, the study showed.

Second Study

A second study, known as Western Denmark, also found higher rates of re-clogging, known as restenosis, and greater need for new surgery in Endeavor patients. Patients getting Medtronic's device also had higher death rates, though the researchers warned against making too much of the finding. A third trial showed Endeavor wasn't better than Xience at preventing clots.

The Western Denmark researchers through they would find Endeavor patients had a bit more restenosis, when the artery re- clogs, and significantly lower safety risks such as clotting than those getting Cypher, said Leif Thuesen, the lead investigator and director of the cardiac catheterization laboratory at Skejby Hospital in Aarhus.

``We were really surprised that the safety wasn't better than with Cypher,'' Thuesen said. ``We had expected the opposite. It's fair to have a bit higher restenosis rate in case the safety is better. This seems not to be the case here.''

Thuesen stopped using the Endeavor stent as a result of the trial. He now prefers a newer Medtronic device called Endeavor Resolute that is available in Europe.

Drug Treatments

Patients in the study have only been followed for about nine months and most are taking drugs including aspirin and Plavix from Bristol-Myers Squibb Co. and Sanofi-Aventis SA to prevent clots, said Lassen, lead investigator in the Sort-Out III study. Once they stop the medicine, more Cypher patients may develop problems, he said. In addition, the sickest patients may have been given Endeavor, skewing the findings, he said.

``We have to be careful, but I think there are some signals in what we have seen today,'' Lassen said during a press conference. ``It's only half the story,'' he said, with more information to come as the study continues. ``But the signal in the registry is still there. I think it's kind of a warning of a safety problem.''

Endeavor's portion of U.S. stent sales fell to 13 percent in the third quarter, down from 18 percent the prior three months, said Michael Weinstein, a J.P. Morgan Chase & Co. analyst, in an Oct. 8 note to clients. Xience and a copy sold by Boston Scientific called Promus are now the top-selling stents in the country, Abbott said this week.

`Far From Proof'

``These data are interesting, but they are far from extraordinary proof,'' said Daniel Beach, a spokesman for Minneapolis-based Medtronic, in an e-mail. He said the findings were unusually positive in the Cypher-treated patients.

Medtronic is conducting a three-year study known as Protect with 8,800 patients to definitively determine if Endeavor reduces the risk of blood clots more than a year after the device is implanted. The results will be available in 2011.

The third study presented today, Estrofa, found Endeavor did no better than Xience at preventing blood clots when used at Spanish hospitals. The rate of clotting among the 3,300 patients with Endeavor was 1.5 percent, compared with 1.4 percent for Xience, said lead investigator Jose de la Torre Hernandez at a news conference.

The results came one year after the stent was implanted and Hernandez cautioned longer-term data might change the picture. Endeavor's advantage over other stents has shown up at two years and beyond in other studies.

To contact the reporters on this story: Michelle Fay Cortez in Minneapolis at mcortez@bloomberg.net; Alex Nussbaum in New York anussbaum1@bloomberg.net;

Last Updated: October 16, 2008 17:07 EDT