Abstract 3995: Comparison of the Effects of Prasugrel and High Dose Clopidogrel on In Vivo and In Vitro Platelet Activation: Results from PRINCIPLE-TIMI 44

Abstract

In PRINCIPLE-TIMI 44, a randomized study in 201 patients undergoing cardiac catheterization for planned PCI, we reported that prasugrel resulted in greater inhibition of in vitro ADP-stimulated platelet aggregation than clopidogrel 600 mg loading dose (LD) and 150 mg maintenance dose (MD). Here we compare the effects of prasugrel and clopidogrel on in vivo and in vitro platelet activation. As prespecified end points of PRINCIPLE-TIMI 44, we measured circulating platelet-monocyte aggregates (PMA), circulating platelet-neutrophil aggregates (PNA), circulating P-selectin-positive platelets (PSPP), plasma soluble CD40 ligand (sCD40L) and (because activated platelets induce its release from leukocytes) myeloperoxidase (MPO). We also evaluated in vitro ADP-stimulated PMA, PNA and PSPP. At 6 h post LD, clopidogrel and prasugrel resulted in similar reductions in circulating PMA (Fig. A ), PNA and PSPP. In vitro ADP-stimulated PMA (Fig. B ), PNA and PSPP were inhibited to a greater degree by prasugrel than clopidogrel during the LD and MD phases. At 6 h post LD, clopidogrel- but not prasugrel-treated patients had elevated plasma MPO compared to pre-treatment (Fig. C ). Plasma sCD40L was unaffected by time or treatment. In this randomized study: Prasugrel, like clopidogrel, inhibited in vivo platelet activation. Prasugrel, to a greater degree than clopidogrel, inhibited ADP-stimulated PMA, PNA and PSPP – which may be mechanistically important, given the high local concentrations of ADP at sites of thrombus formation. Prasugrel, unlike clopidogrel, prevented the post-PCI-induced increase in the inflammatory marker MPO.