An experimental drug developed by AVI BioPharma prevented clogging of heart arteries in an animal study, researchers said Wednesday, paving the way for human clinical trials.
The Portland-based biotechnology startup is racing many others to develop drugs to keep heart arteries open after angioplasty. Because hundreds of thousands of people undergo the procedure each year worldwide, the market could be worth billions to companies that succeed in human tests.
AVI and its competitors are coating the drugs onto stents, the wire mesh tubes that heart specialists place inside arteries to prop them open after angioplasty, the procedure to restore blood flow to the heart. About one in four patients require repeat angioplasty or bypass surgery within six months because an overgrowth of scar tissue causes arteries to become dangerously clogged again.
AVI is collaborating with Minneapolis-based Medtronic, the second-biggest seller of stents in the United States.
The current leader in drug-coating technology is Cordis, a unit of Johnson & Johnson, with a stent that slowly releases the drug sirolimus, also called Rapamune. In a European study that astounded heart experts earlier this year, patients who received the coated stents experienced no detectable narrowing of treated arteries. Most had no further heart trouble within six months. Researchers continue to follow the patients to determine ongoing effectiveness.
AVI said that based on the positive animal results with its drug, Resten-NG, the company plans to begin human clinical trials with the coated stent early next year. Dr. Nicholas Kipshidze, a scientist at the Lenox Hill Heart & Vascular Institute in New York City and lead researcher on the AVI study, reported the results at this week's American Heart Association's scientific meeting.
Dr. Andrew Carter, a cardiologist who worked on the development of the Cordis stent, said AVI's approach is unique and that the animal results look promising.
"It proves the concept; it demonstrates that they can do this," said Carter, who recently left a post at Stanford University Medical Center to became medical director of interventional cardiology at Providence St. Vincent Medical Center in Portland.
None of the new drug coatings has gained regulatory approval, the next step after successful human clinical trials. Carter said an important unknown is whether the drugs will prevent restenosis, or artery clogging, for the long-term or just temporarily delay the process.
AVI's Resten-NG blocks the action of a specific gene, called c-myc. When the gene is active, it contributes to the cell growth spurt that clogs stented arteries.
Scientists placed stents coated with Resten-NG in the arteries of pigs. Tests showed that the drug blocked gene activity as intended. Dissection of the pigs 28 days later showed that the drug had also prevented the re-clogging of stented arteries but hadn't interfered with the healing of scrapes inside arteries caused by stent placement.
AVI BioPharma has received $10 million from stent-maker Medtronic. To gain exclusive rights to AVI drugs, Medtronic also has agreed to invest close to $100 million over time if AVI reaches all the milestones in the deal. Medtronic's sales of stents and related products exceeded $790 million last year.