Boston Scientific (NYSE:BSX) this week unveiled full results from the PREVAIL clinical trial of the Watchman anti-stroke implant, largely agreeing with earlier reports that the device missed a co-primary endpoint for efficacy.
Watchman is a percutaneously delivered cardiac device permanently implanted in the heart’s left atrial appendage to capture clots that may form there. The device aims to reduce the risk of stroke and may potentially eliminate the need for long-term use of blood-thinning medications.
The implant is already available in 30 countries but is not yet approved for use in the U.S. An FDA panel late last year gave its voted to recommend approval for Watchman, but the FDA wants another hearing.
In the PREVAIL study, the Watchman device met endpoints for safety but missed one for efficacy, as researchers had also reported last year in a presentation that was pulled from the lineup at the 2013 American College of Cardiology conference after Boston Scientific inadvertently leaked the data ahead of time.
Researchers said that Watchman proved non-inferior to the blood-thinner warfarin in preventing ischemic stroke and systemic embolism up to 1 week following implantation, but non-inferiority wasn’t achieved overall at 18 months.
In an editorial accompanying the study, University of California’s Dr. Randall Lee noted that that rate of incidents in the control arm was very low, contributing to the failure of warfarin to improve outcomes. Although initial stroke and adverse event risks with Watchman may match those of anti-coagulants, the drugs pose a lifetime bleeding risk that can’t be ignored.
"The initial embolic risks and adverse events associated with the Watchman device implantation cannot outweigh the long-term bleeding risks of the newer oral anticoagulation drugs," Lee wrote.
The PREVAIL trial was launched in order to address safety concerns raised by a previous Watchman trial. 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.
Natick, Mass.-based Boston Scientific acquired the Watchman device along with AtriTech for up to $375 million in 2011. The technology has gone a few rounds with FDA regulators since 2009, and a recent decision to conduct another panel hearing may push back the approval time line to next year.
Despite the 1st panel’s 2009 approval recommendation, the FDA in March 2010 issued a "not approvable" letter for the Watchman device. A 2nd panel voted 13-1 last year that the Watchman implant meets safety and efficacy goals.