June 21, 2012 in Cardiology A new investigational
platelet blocker reduces the rate of clotted arteries and the need for
artery-opening revascularization procedures in the legs in people with
peripheral artery disease (PAD), according to new research presented in the
American Heart Association’s Emerging Science Series webinar. “Much of the focus on PAD therapies has been on lowering patients’ risk of
heart attack and stroke, but this shows that there can be therapies that reduce
limb-threatening blood clots and the need for revascularization procedures in
the legs,” said Marc P. Bonaca, M.D., M.P.H., Instructor of medicine at Harvard Medical
School and Brigham and Women’s
Hospital in Boston , Mass. , and an investigator with the
Thrombolysis in Myocardial Infarction (TIMI) study group. In the study,
researchers randomized 3,787 patients with PAD to receive standard care or
standard care plus vorapaxar, the first in a new class of anti-platelet drugs
called PAR-1 antagonists. Participants were part of the 26,449-patient
TRA2P-TIMI 50 trial testing 2.5 milligrams per day (mg/day) of vorapaxar in
people with a history of heart attack, stroke or PAD. The TRA2P-TIMI 50 trial
main results presented earlier this year showed a statistically significant
reduction in cardiovascular events including heart attack, stroke, and
cardiovascular death with vorapaxar. In this substudy focused on participants
with PAD, 11.3 percent of those taking vorapaxar experienced these major
cardiovascular events compared with 11.9 percent of those taking a placebo – a
numeric reduction consistent with the overall trial findings that did not reach
statistical significance on its own. However, they found benefits of vorapaxar
on limb events. Compared to those not receiving the drug: Fewer vorapaxar
patients were hospitalized for blood clots in the limbs (2.3 percent vs. 3.9
percent). Fewer vorapaxar patients required revascularization to restore full
blood flow in narrowed or blocked vessels in the limbs (18.4 percent vs. 22.2
percent). “This is the first outpatient therapy that
has been shown to reduce the risk of blood clots and the need for artery
opening revascularization procedures in the legs in patients with PAD,” Bonaca
said. The reduction in both urgent blood clots as well as the need for surgery
to treat worsening atherosclerosis suggests that the drug may be working in
more than one way. “The target for this therapy is expressed on platelets but
also on cells in the artery walls that are important for normal artery
function. The benefits observed may be due to drug activity at both sites,”
noted Bonaca. Moderate and severe bleeding was increased in patients on
vorapaxar compared to those on standard care (7.4 percent vs. 4.5 percent
consistent with the overall trial); however, there was no increase in fatal
bleeding. “For clinicians and researchers, these data show the potential for
therapies that can reduce leg problems in patients with PAD rather than just
overall cardiovascular risk,” Bonaca said. The investigators are analyzing
whether vorapaxar treatment improves circulation in the lower body, or allows
patients to walk further without pain due to insufficient blood flow to leg
muscles (claudication). All of the PAD patients in the study initially had
symptoms of claudication, and either poor leg circulation or a previous
vessel-opening procedure. Co-authors are David A. Morrow, M.D., M.P.H., and
Eugene Braunwald, M.D. Merck funded the study. Provided by American Heart
Association
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