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When arteries carrying blood to the heart muscles become blocked, doctors often clear them by performing an angioplasty (inserting a balloon to open the narrowing passageways) and then inserting a mesh metal tube called a stent. This conduit is designed to act as scaffolding to keep the artery open. Because this procedure was introduced three decades ago, researchers have been searching for ways to coat such stents to protect patients from allergic reactions to the metal and keep surrounding tissue from growing through the mesh and reclogging the artery.
One biotech company believes it may have come up with a way to do both by covering its stents with hydroxyapatite, a ceramiclike substance found in tooth enamel. Atlanta-based MIV Therapeutics, Inc., says such devices are just as good as bare metal stents at keeping arteries open and less likely than polymer-coated stents—which typically administer a drug to keep tissue growth at bay—to contribute to blood clotting, irritation and inflammation, says MIV's chief executive officer Mark Landy.
MIV recently began recruiting heart patients for a 120-person trial designed to test how well the technology works. If the trial is successful, MIV plans to use the data to apply for marketing approval in Europe. This data will be used to help MIV gain approval for its VESTAsync stent from the U.S. Food and Drug Administration, a process that is longer and more complicated. The current trial follows a nine-month safety and efficacy trial conducted last year at the Institute Dante Pazzanese of Cardiology in São Paulo, Brazil, on 15 patients that proved VESTAsync works safely in people, Landy says.
"We have developed a drug delivery system that can be used on stents and other implantable medical devices that is polymer-free and can administer medication to the local tissue" to keep an artery from reclosing, Landy says. Patients who receive drug-coated polymer stents are generally required to take Plavix or another anticoagulant for at least a year after an angioplasty, in addition to the medicine dispensed by the stents. "Our hope is to reduce the need for this oral blood-clotting drug," he says. "That is probably the most desirable outcome of what MIV is pursuing."
MIV is hoping its use of hydroxyapatite will give the company an edge in a stent market worth nearly $2 billion in U.S. sales in 2007 and already crowded with medical supply heavyweights such as Johnson & Johnson and Boston Scientific Corporation as well as newer competitors Medtronic, Inc., and Abbott Laboratories. The U.S. Food and Drug Administration approved use of Johnson & Johnson's Cypher stent in early 2003, and approved Boston Scientific's Taxus a year later.
Landy would not speculate on the price tag of the stents, developed with researchers at the University of British Columbia. But he says they probably would cost about the same as—if not less than—polymer-coated stents now on the market. The company's ultimate goal, says Landy: to develop a stent that will dissolve once it is no longer needed, which would eliminate concerns about ingrown tissue and chronic inflammation. But he says such technology is still at least a decade away.
