Platelet inhibitory activity and pharmacokinetics of prasugrel (CS-747) a novel thienopyridine P2Y12 inhibitor: A single ascending dose study in healthy humans

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Abstract
We assessed the tolerability, pharmacodynamics as measured by inhibition of platelet aggregation (IPA), and pharmacokinetics of prasugrel (CS-747, LY640315), a novel thienopyridine antiplatelet agent in healthy volunteers. Twenty-four subjects were randomized into four groups of six in a double-blind, placebo-controlled trial. One subject in each group received placebo and five subjects received prasugrel orally at single doses of 2.5, 10, 30, or 75 mg. The IPA, assessed using 5 and 20 microM ADP, was periodically measured over a 7-day period by light transmission aggregometry. Plasma concentrations for three major metabolites, R-95913, R-106583, and R-100932, were measured. There were no serious adverse events and no clinically significant changes noted in any laboratory or clinical evaluations in any subject. At 1 h after prasugrel 30 and 75 mg, platelet aggregation induced by 20 microM ADP was inhibited by 43.5 +/- 7.8 and 43.2 +/- 15.7%, respectively, and this inhibition was significantly greater than that following placebo (5.9 +/- 3.5%) (P < 0.05 for both doses). The degree of inhibition observed at 2 h was slightly higher with both prasugrel 30 and 75 mg (59.8 +/- 9.9 and 57.0 +/- 7.2%) and was maintained through the subsequent 22 h. At 24 h, maximal platelet aggregation induced by 20 microM ADP was reduced to 0.05 for 2.5 and 10 mg prasugrel vs. placebo). With prasugrel 75 mg at 4 h postdose, there was a significant increase in the mean bleeding time compared to placebo (682 vs. 161 s; P < 0.05). Prasugrel metabolites obeyed linear pharmacokinetics and the three metabolites appeared in the plasma soon after administration, reaching maximum levels at approximately 1 h. In conclusion, prasugrel 30 and 75 mg were well tolerated and achieved a consistently high level of platelet inhibition with a fast onset of action.