(Reuters) - U.S. government scientists have raised questions about the potential risks to patients of heart attacks and blood clots from Abbott Laboratories' novel coronary stent that dissolves after it is implanted.
Abbott is seeking U.S. approval to sell the stent, called Absorb, as an alternative to metal stents currently used in percutaneous coronary intervention. Unlike traditional stents that remain in place after implantation, Absorb is designed to disappear within three years of the procedure.
U.S. Food and Drug Administration staff, in documents released before an advisory panel meets on Tuesday to consider whether to recommend approval of the device, said they would ask the outside experts about data showing more heart attack and stent-related blood clots compared with Abbott's drug-coated metal Xience stent.
FDA said it also will ask the panel to address risks associated with the device when used in smaller arteries.
A large clinical trial released in October concluded that the Absorb stent, which is made of a plastic similar to dissolving sutures, was comparable to Xience in overall safety and effectiveness. Although Xience appeared to be numerically better than Absorb at one year on a variety of secondary measures, the differences were not considered statistically significant.
"These results are from physicians using a new therapy for the first time. Consequently, we expect them to improve with time and experience," said Abbott spokesman Jonathon Hamilton.
In the Absorb III clinical study, patients with small vessels comprised less than 20 percent of the total and experienced relatively low rates of adverse events even though many had known risk factors, including diabetes, Hamilton said.
More than 125,000 patients already have been treated with Absorb in more than 100 countries where it is commercially available.
If approved in the United States, Absorb would compete with Xience, the market-leading stent, and with Medtronic Plc's Resolute stent and Boston Scientific's Synergy and Promus stents. Synergy's polymer coating used to deliver a drug disappears over time, leaving a bare metal stent in place.
Wells Fargo analyst Larry Biegelsen said he expects Absorb to get a positive recommendation from the advisory panel, followed by FDA approval later this year.
"In the U.S., we estimate Absorb will capture about 5 percent of the total drug-eluting stent market, although our estimate may prove conservative if the post-approval data and experience with Absorb improves," Biegelsen wrote in a note to clients.