Rebound platelet activation after termination of prasugrel and aspirin therapy due to confirmed non-compliance in patient enrolled in the JUMBO Trial

Therapy with aspirin and/or adenosine diphosphate (ADP) receptor blockers is associated with better outcomes via inhibition of platelet activity, and subsequent reduction of ischemic vascular events. Non-compliance (NC) is a well-recognised hazard limiting the clinical utility of antiplatelet agents, and, probably worsening outcomes. However, comprehensive platelet characteristics of a confirmed NC patient after acute vascular event have never been reported within a major randomised trial with ADP-receptor antagonists. A 48-year-old male patient, well-educated, was among patients enrolled in the platelet sub-study for the JUMBO trial. He received 325 mg of aspirin daily for 9 months, presented with unstable angina for urgent coronary intervention, and was successfully reperfused with two intracoronary stents. The patient was randomised to a 60 mg prasugrel loading dose, and 10 mg of prasugrel daily for 30 days. Platelets were assessed at baseline, 4 and 24 h, and at 30 days after acute coronary event utilising ADP-, and collagen-induced conventional aggregometry, rapid cartridge-based analyser and flow cytometry. Loading with prasugrel resulted in significant inhibition of platelet activity during and after stenting. However, after assessing platelet biomarkers at 30 days, voluntary withdrawal from the antiplatelet agents was suspected. Based on the platelet activity characteristics, NC was later confirmed, and the patient admitted that he stopped taking both prasugrel and aspirin shortly after discharge due to minor bleeding episodes after shaving. Major platelet activity biomarkers of the index NC patient were compared with those from compliant prasugrel-, clopidogrel-treated patients, and healthy controls. The platelet tests uniformly revealed rebound activation by all platelet measures (at least twofold increase) while being especially high for ADP-, and collagen-induced aggregation, platelet/ endothelial cell adhesion molecule-1 (PECAM-1), glycoprotein (GP)Ib, GPIIb/IIIa activity, P-selectin, protease activated receptor (PAR)-l thrombin receptor (activated and intact epitopes), and thrombospondin expression. The clinical benefits of antiplatelet agents are not only denied in NC outpatients, but may put them at additional risk for worsened vascular outcomes due to the rebound platelet activation. Proclaimed 'resistance' to antiplatelet agents may at least in part be a result of NC, especially in the chronic uncontrolled setting. Enforcing compliance will improve outcomes in the clinical trials, and save lives of patients really receiving antiplatelet therapy.