In elderly or low-weight patients with acute coronary syndrome (ACS), a reduced dose of prasugrel relative to a full-dose of ticagrelor is associated with lower numerical rates of ischemic events and bleeding events, according to a prespecified substudy of the ISAR-REACT 5 trial.
“The present study provides the strongest support for reduced-dose prasugrel as the standard for elderly and low-weight patients with ACS undergoing an invasive treatment strategy,” according to the senior author, Adnan Kastrati, MD, professor of cardiology and head of the Catheterization Laboratory at Deutsches Herzzentrum, Technical University of Munich.
The main results of ISAR-REACT 5, an open-label, head-to-head comparison of prasugrel and ticagrelor in patients with ACS, showed that the risk of the composite primary endpoint of death, myocardial infarction, or stroke 1 year after randomization was significantly higher for those on ticagrelor than prasugrel (hazard ratio, 1.39; P = .006). The bleeding risk on ticagrelor was also higher but not significantly different (5.4% vs. 4.8%; P = .46) (Schüpke S et al. N Engl J Med. 2019 Oct;381:1524-34).
In this substudy newly published in Annals of Internal Medicine, outcomes were compared in the 1,099 patients who were 75 years or older or weighed less than 60 kg. In this group, unlike those younger or weighing more, patients were randomized to receive a reduced maintenance dose of 5 mg of once-daily prasugrel (rather than 10 mg) or full dose ticagrelor (90 mg twice daily).
At 1 year, the low-dose prasugrel strategy relative to ticagrelor was associated with a lower rate of events (12.7% vs. 14.6%) and a lower rate of bleeding (8.1% vs. 10.6%), defined as Bleeding Academic Research Consortium (BARC) type 3-5 events.
Neither the 18% reduction for the efficacy endpoint (HR, 0.82; 95% CI 0.60-1.14) nor the 28% reduction in the bleeding endpoint (HR, 0.72; 95% CI 0.46-1.12) reached significance, but Dr. Kastrati reported that there was a significant “treatment effect-by-study-group interaction” for BARC 1-5 bleeding (P = .004) favoring prasugrel. This supports low-dose prasugrel as a strategy to prevent the excess bleeding risk previously observed with the standard 10-mg dose of prasugrel.
In other words, a reduced dose of prasugrel, compared with the standard dose of ticagrelor, in low-weight and elderly patients “is associated with maintained anti-ischemic efficacy while protecting these patients against the excess risk of bleeding,” he and his coinvestigators concluded.
Low-weight and older patients represented 27% of those enrolled in ISAR-REACT 5. When compared to the study population as a whole, the risk for both ischemic and bleeding events was at least twice as high, the authors of an accompanying editorial observed. They praised this effort to refine the optimal antiplatelet regimen in a very-high-risk ACS population.
“The current analysis suggests that the prasugrel dose reduction regimen for elderly or underweight patients with ACS is effective and safe,” according to the editorial coauthors, David Conen, MD, and P.J. Devereaux, MD, PhD, who are affiliated with the Population Health Research Institute, Hamilton, Ontario.
This substudy was underpowered to show superiority for the efficacy and safety outcomes in elderly and low-weight ACS patients, which makes these results “hypothesis generating,” but the authors believe that they provide the best available evidence for selecting antiplatelet therapy in this challenging subgroup. Although the exclusion of patients at very high risk of bleeding from ISAR-REACT 5 suggest findings might not be relevant to all elderly and low-weight individuals, the investigators believe the data do inform clinical practice.
“Our study is the first head-to-head randomized comparison of the reduced dose of prasugrel against standard dose of ticagrelor in elderly and low-weight patients,” said Dr. Kastrati in an interview. “Specifically designed studies for this subset of patients are very unlikely to be conducted in the future.”
Dr. Kastrati reported no potential conflicts of interest relevant to this study.
SOURCE: Menichelli M et al. Ann Intern Med. 2020 Jul 21. doi: 10.7326/M20-1806.
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