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Prasugrel vs. clopidogrel linked with lower platelet reactivity in select patients
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LOS ANGELES — The platelet function substudy of the TRILOGY ACS trial has shown that among patients with ACS without ST-segment elevation who were not treated with revascularization, prasugrel use was associated with lower platelet reactivity compared with clopidogrel, irrespective of age, weight and dose.
The substudy included patients enrolled in the TRILOGY ACS trial (n=2,564; 27.5%) who had medically managed unstable angina or non-STEMI. Patients were treated with either prasugrel (Effient, Daiichi Sankyo/Eli Lilly; n=1,286) or clopidogrel (Plavix, Sanofi-Aventis; n=1,278).
Platelet reactivity was measured in P2Y12 reaction units (PRUs) at baseline and 2 hours, and 1, 3, 6, 12, 18, 24 and 30 months after randomization. Researchers defined the primary efficacy endpoint as a composite of CV death, MI or stroke through 30 months.
At 30 days, patients aged younger than 75 years and weighing 60 kg or more had median PRU values of 64 in the prasugrel group compared with 200 in the clopidogrel group (P<.001); this difference persisted through all subsequent time periods. For those aged younger than 75 years and weighing less than 60 kg, median 30-day PRU values were 139 in the prasugrel group vs. 209 in the clopidogrel group (P<.001), while for participants 75 years or older, the median PRU values were also lower in the prasugrel group (164 vs. 222; P<.001).
In addition, follow-up at 30 months revealed the difference in the primary efficacy endpoint did not reach statistical significance between groups (prasugrel, 17.2% vs. clopidogrel, 18.9%; P=.29). The researchers also reported no significant differences in the continuous distributions of 30-day PRU values for patients with a primary efficacy end point event after 30 days (n=214) compared with participants without an event (n=1794; P=.07) and no significant relationship between the occurrence of the primary efficacy endpoint and continuous PRU values (adjusted HR for increase of 60 PRUs=1.03; 95% CI, 0.96-1.11).
“This is the longest longitudinal assessment of on-treatment platelet reactivity for both clopidogrel- and prasugrel-treated patients,” Paul A. Gurbel, MD, director of the Sinai Center for Thrombosis Research at the Sinai Hospital of Baltimore and associate professor of medicine at Johns Hopkins University School of Medicine, said at the American Heart Association Scientific Sessions 2012. “The lack of independent association between platelet association between platelet reactivity and ischemic outcomes may explain the comparable clinical outcomes in TRILOGY ACS.” – by Brian Ellis and Katie Kalvaitis
For more information:
Gurbel PA. Late-breaking clinical trials: Practice implications for CAD and VTE. Presented at: the American Heart Association Scientific Sessions 2012; Nov. 3-7, 2012; Los Angeles.
Gurbel PA. JAMA. 2012;308:1785-1794.
Disclosure: Gurbel reports consulting, grants, stock and other financial interests in a number of companies. See the study for a full list of disclosures.