In panel documents released ahead of this week’s meeting, the FDA asked its advisory committee to keep in mind that the Watchman permanent left atrial appendage closure device failed in a recent study to meet a primary goal for effectiveness and that previous trials have raised questions about the risks surrounding implantation surgery.
The Watchman implant, already available in 30 countries, is introduced via catheter and threaded into the heart to close off the left atrial appendage and capture any blood clots that may form there.
A December 11 meeting of the FDA’s Circulatory System Devices Panel will discuss whether the Watchman device is safe and effective enough to recommend for FDA approval. Although the FDA is not bound by the recommendations of its advisory panels, it often follows their lead.
The FDA asked panel members to consider Watchman data from a variety of analyses, including the early PROTECT AF study, the newer PREVAIL trial and the CAP patient registry. The federal watchdog agency highlighted that results from the PREVAIL study failed to support the primary effectiveness endpoint, the same benchmark that researchers met in the earlier PROTECT trial.
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In March, Natick, Mass.-based Boston Scientific unveiled results from the Prevail clinical trial of the Watchman device, saying it met 2 of 3 co-primary endpoints for safety and effectiveness compared with drug therapy. Watchman achieved its 2 safety endpoints, but researchers found no differences in rates of stroke, systemic embolism and cardiovascular or unexplained death at 18 months between patients who received the Watchman device and those who were treated only with warfarin, a blood thinner.
The Prevail trial was launched in order to address safety concerns raised by a previous Watchman trial, Boston Scientific noted. The Protect AF trial showed that treatment with the Watchman device reduced a patient’s risk of hemorrhagic stroke compared with warfarin, but also showed an increase in procedure-related adverse events.
Wall Street seemed unperturbed by focus on the missed endpoint and surgical risks, with a Wells Fargo analyst optimistic on the outcome of this week’s panel.
"The FDA stresses a number of times in the briefing documents that the panel members should consider the totality of the data, which we think is a positive sign," Wells Fargo medtech analyst Larry Biegelsen wrote in a note to investors. "The FDA documents were more mixed than we anticipated which leads us to believe that the panel will be contentious but we still expect a positive outcome and approval."
Boston Scientific acquired the Watchman device along with AtriTech in a deal valued at $375 million in 2011. In August the device won expanded CE Mark approval in the European Union for the catheter-based clot-capture system, to patients with atrial fibrillation who can’t be treated with warfarin or new oral anticoagulants.
Boston Scientific’s stock slipped a bit in afternoon trading, with shares down 1.3% to $11.70 apiece as of about 2:50 p.m.