Boston Scientific (NYSE:BSX) today unveiled new results from a clinical trial of its Watchman stroke prevention device, reporting that the cardiac implant met 2 of 3 co-primary endpoints for safety and effectiveness compared with drug therapy.
The company’s PREVAIL trial 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 with warfarin, a blood thinner.
The device had success in more success in demonstrating lowered rates of acute death or serious vascular complications related to the procedure in the 7 days following implantation, as well as low rates of ischemic stroke or systemic embolism more than 7 days and up to 18 months following implantation, Boston Scientific announced.
The results were unveiled in a late-breaking trial presentation at the American College of Cardiology conference in San Francisco.
The Watchman device, which is 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. The device aims to reduce the risk of stroke and may potentially eliminate the need for long-term use of blood-thinning medications.
Boston Scientific was pressured into releasing its PREVAIL full study results this weekend, after conference organizers and Wall Street analysts balked at the company’s announcement that it would unveil only the acute procedural safety results from the trial.
The exclusion made headlines, and Boston Scientific reported shortly after that it would scramble to ensure that results for all 3 co-primary endpoints were ready for presentation.
The failure to meet comparative effectiveness endpoints may bode ill for the Watchman device as it aims for FDA approval, but the researchers appeared confident with the new results.
"I believe this information will reassure the FDA and the cardiovascular community about the improved safety and efficacy of this procedure and device, which has been implanted in more than 2,000 patients world-wide," co-principal investigator and Mayo Clinic professor Dr. David Holmes said in prepared remarks. "This is an important part of the journey to develop new strategies for stroke prevention in atrial fibrillation to avoid the need for long-term or life-long anticoagulation in some patients. Such a device can make a tremendous difference for patients with atrial fibrillation."
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.
Natick, Mass.-based Boston Scientific acquired the Watchman device along with AtriTech for up to $375 million in 2011. Last summer the company closed enrollment in a 2nd trial of the device, with more than 2,000 subjects signing on for the randomized comparison of Watchman with warfarin in high-risk patients with atrial fibrillation. 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.