Coronary stents that secrete drugs to prevent scarring are a standard medical treatment, with more than one million implanted in U.S. patients every year. But some studies indicate that these stents--coated with a polymer that holds the drugs--may present their own problems. In March, for example, a study released by University Hospital in Basel, Switzerland, found that some patients who received them suffered higher rates of blood clotting than those using bare-metal stents.

Now, Conor Medsystems of Menlo Park, CA, believes it has a safer drug-­releasing stent. Hundreds of tiny holes run along the branches of Conor's metal stent, which is made from stainless steel and cobalt chrome. Each hole acts as a reservoir for the drug-and-polymer mixture, whose proportions can be altered from one reservoir to the next. That allows different medications to be released far more precisely than is possible with today's technology, in which one coating covers the whole stent, says Conor's founder and chief technology officer, John Shanley. What's more, polymers in embedded reservoirs can be more biodegradable than existing coatings, which need to be tougher to withstand the friction of insertion. The stent has passed European trials; Conor is now conducting U.S. human trials that are expected to be complete next year.