Data from 1 of the studies, presented yesterday at the International Society for Heart & Lung Transplantation’s annual meeting by Dr. Simon Maltais of the Vanderbilt University Medical Center, showed that the hemorrhagic stroke rate increase to 6.5% at 6 months for the full 600-patient cohort. The trial is a post-approval study of HeartWare’s HVAD left ventricular-assist device, an implantable heart pump.
The 6.5% rate was higher than the 5.8% rate reported with the study’s interim data from the 1st 308 patients, which was presented at the ISHLT meeting last year, and more than the 4.5% rate reported in the BTT continued access protocol study.
Data from the Endurance I study were presented today at ISHLT in Nice, France, by co-principal investigator Dr. Francis Pagani of the University of Michigan Health System. Although the HVAD device met the Endurance I trial’s primary endpoint of noninferiority in stroke-free survival at 2 years, coming in at 55.0% compared with 57.4% for rival Thoratec‘s (NSDQ:THOR) HeartMate II device, the combined rate of ischemic and hemorrhagic stroke rate was also elevated.
The HVAD device’s combined stroke rate was 31.1%, compared with 12.7% for HeartMate II. Investors reacted by sending HTWR shares down 4.0% to a $87.24 close yesterday and paring another 3.2% off the stock today. HTWR shares were trading at $84.42 apiece in mid-day activity today, down 3.2%. The stock is down 8.3% since the 1st study results were revealed.
Leerink Partners analyst Danielle Antalffy said a few factors may have affected both studies’ stroke rates. Prior studies have shown that the implanting physician’s experience with the device plays a role, as well as surgeons failing to comply with the studies’ protocols.
"We’d also highlight the importance of looking at the totality of data presented today, including the Revolve registry and EU registries, which demonstrated significantly lower rates of stroke with HVAD in a real-world commercial setting in Europe. Still, THOR could undoubtedly attempt to gain some ground vs. HTWR by pointing to a nearly 3x higher stroke rate in this initial trial cohort. This data will clearly create some noise in the market and could give THOR at least a temporary leg up, in our view, particularly as HeartMate III enrolls its U.S. pivotal study with the safety phase already underway," Antalffy wrote in a note to investors.
"As the largest, randomized, destination therapy trial to date involving ventricular assist devices, the observations from Endurance demonstrate the potential of the HeartWare system as a longer-term treatment option for advanced heart failure patients who have exhausted medical therapy and are ineligible for a heart transplant," Pagani said in prepared remarks. "Survival with the HVAD Pump at two years was comparable to the control device. HVAD device and design improvements, including sintering of the inflow cannula, resulted in improvements in outcomes, including a marked reduction in pump thrombosis."