* Thoratec shares up as much as 16.7 pct
* HeartWare shares down as much as 21 pct
* Share moves follow release of data on Friday
* Data showed high thrombosis risk with HeartWare device
By Toni Clarke
BOSTON, April 18 Shares of Thoratec Corp
THOR.O rose as much as 16.7 percent on Monday while those of
rival HeartWare International Inc HTWR.O fell as much as 21.0
percent after data from a trial of HeartWare's heart device
showed a higher-than-expected rate of blood clots.
Data released late on Friday showed patients implanted with
HeartWare's mechanical heart-assist device, known as the HVAD,
had an unexpectedly high 9.2 percent chance of developing a
potentially life-threatening blood clot per year.
A rival device made by Thoratec, known as HeartMate II,
carries an estimated risk of heart-pump-related thrombosis of
about 3 percent. [ID:nN18123042]
HeartWare's device is approved in Europe and awaiting
approval in the United States as a bridge-to-transplant (BTT),
or to keep patients alive while they wait for heart transplant.
The company is currently enrolling patients in a trial to test
the device as a long-term treatment for patients who are not
eligible for a heart transplant -- known as destination therapy
While analysts said they do not expect Friday's data to
stop U.S. regulators approving the device as a
bridge-to-transplant, some said it could slow enrollment in the
ongoing destination therapy trial, and others said it could
increase the risk that U.S. regulators would require more data
before approving the device.
Data showed that the 250 patients in the trial contributed
a total of 174 patient years, for an overall thrombosis rate of
9.2 percent per patient year. There were 16 cases of
pump-related blood clots, of which 11 required the device to be
HeartWare said it is confident that rate will decline in
future because its analysis showed that a subset of patients
who took 325 milligrams of aspirin, rather than the previously
recommended 81 milligrams, had a far lower risk of developing a
blood clot. The company recently changed its clinical trial
protocol to boost the recommended aspirin dose to 325
milligrams. Aspirin helps thin the blood and can potentially
Analysts at UBS, who maintain their "buy" recommendation on
HeartWare's stock, said that although a post-hoc analysis
suggests a strong relationship between device replacement due
to pump-related thrombosis and aspirin, the theory remains
unproven, which could cause the U.S. Food and Drug
Administration to require additional data.
"Our instinct is that these pump thrombus issues will be
adequately addressed over time," they said. However, they said,
"to the extent the FDA takes a conservative view of pump
exchange, biologic plausibility may not be satisfactory and
additional data may conceivably be required."
Sean Lavin, an analyst at Lazard Capital Markets, said he
expects the rate of enrollment in the destination trial to
slow, and market share in Europe and the U.S. in future to be
lower than he previously thought.
"With this in mind, our HeartWare revenue forecasts fall
while our Thoratec forecasts pick up extra pumps," he said.
One added cause for concern, he said, is that the
thrombosis rate with HeartWare's device increased over time.
"If the rate keeps increasing, the pump would likely not be
viable for the DT market, which is likely to be much larger
than BTT," he said. "It will be imperative to see if patients
on higher aspirin show a strongly increasing thrombi rate over
time, or if their rates remain relatively low."
Analysts at J.P. Morgan said that while thrombus concerns
are likely to weigh on HeartWare's shares, the company's
competitive position remains strong.
"In the end, we expect this weekend's results to temper
Street expectations for rapid adoption of the HVAD following
its US approval (anticipated by year end) and HeartWare's
shares are likely to come under some pressure Monday as a
result," they said. "Our own view, however, is that the HVAD
remains a compelling option for patients, with this latest
issue just one piece of a multifaceted decision clinicians will
face between two very good pumps."
HeartWare's shares fell 15.3 percent to $71.05 in
late-morning trading on Nasdaq. Earlier in the day they fell as
low as $66.15. Thoratec's shares rose 12.6 percent to $30.88.
Earlier they rose as high as $32.00 a share.
(Reporting by Toni Clarke, editing by Dave Zimmerman)