In a Phase II study, Acute Coronary Syndrome (ACS) patients on maintenance clopidogrel/aspirin therapy who were switched to prasugrel (Efient – either 10mg maintenance dose [MD] or 60mg loading dose [LD] followed by 10mg MD) plus aspirin demonstrated a statistically significant greater reduction in Maximal Platelet Aggregation (MPA) after one week when compared to patients who remained on maintenance therapy (MD) with clopidogrel.
The study, published today in the Journal of the American College of Cardiology, evaluated the level of platelet aggregation achieved after switching from clopidogrel 75mg once daily MD plus aspirin, to prasugrel 10mg once daily MD in patients with acute coronary syndrome. The Switching Anti Platelet Study (SWAP) was sponsored by Daiichi Sankyo Co, Ltd and Eli Lilly and Company.
Platelet aggregation is a critical step in the formation of blood clots, which pose a significant risk to patients following an ACS event, including heart attack and heart-related chest pain. The study provides further evidence to suggest that prasugrel can reduce platelet aggregation to a greater extent among ACS patients compared with clopidogrel.
Of the 128 patients who completed the study, 100 patients with evaluable data were eligible to be included in the platelet function analysis. After a 10-14 day run-in phase with open label clopidogrel 75mg once daily plus aspirin, patients were randomised to either remain on clopidogrel 75mg plus aspirin for seven days (n=33), switch to prasugrel 10mg plus aspirin for seven days (n=36), or switch to prasugrel 60mg loading dose plus aspirin followed by prasugrel 10mg plus aspirin daily for 6 days (n=31).
At day seven, MPA (as measured using 20 mM ADP) was significantly lower in patients switched to prasugrel MD 10mg plus aspirin when compared to the patients who remained on clopidogrel MD (41.1 percent vs. 55.0 percent, p<0.0001). It was also significantly lower in those patients switched to prasugrel 60mg LD followed by prasugrel 10mg MD compared to clopidogrel MD (41.0 percent vs. 55.0 percent, p<0.0001).
“These findings are important because they provide new insights into potential differences in the levels of platelet inhibition that can be achieved with dual oral antiplatelet therapy in patients with ACS,” said Dominick J. Angiolillo, MD, Assistant Professor, Department of Medicine, Division of Cardiology, University of Florida College of Medicine, Jacksonville, and lead author of the paper.
“The data showed that prasugrel plus aspirin may be able to provide additional reduction in platelet aggregation in ACS patients over those taking standard dose clopidogrel plus aspirin. However, a larger study would be needed to assess the potential impact of switching on cardiovascular outcomes.”
The SWAP study was not designed to evaluate efficacy or safety endpoints. The clinical safety and efficacy of switching from clopidogrel to prasugrel has not been studied.