Journal
JOURNAL OF THROMBOSIS AND HAEMOSTASIS
Volume 12, Issue 8, Pages 1320-1330Publisher
WILEY-BLACKWELL
DOI: 10.1111/jth.12637
Keywords
11-dehydro-thromboxane B-2; acetylsalicylic acid; antiplatelet drugs; cyclooxygenase-1; proteomics; thromboxane A(2)
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Funding
- Bayer Pharma AG
- Ministero dell'Istruzione, dell'Universita e della Ricerca (MIUR) (Grant PRIN) [2010FHH32M]
- Associazione Italiana per la Ricerca sul Cancro [IG-12111]
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Background: Even though the acetylation of platelet cyclooxygenase (COX)-1 at serine-529 is the direct mechanism of action of low-dose aspirin, its antiplatelet effect has been characterized using indirect indexes of COX-1 activity. Objectives: We performed a clinical study with enteric-coated low-dose aspirin (EC-aspirin), in healthy subjects, to evaluate the effects on the extent and duration of platelet COX-1 acetylation, using a novel proteomic strategy for absolute protein quantification (termed AQUA), as compared with traditional pharmacokinetic and pharmacodynamic parameters. Subjects and methods: In a phase I, single-arm, open-label study of EC aspirin (100 mg day(-1)) administered to 24 healthy subjects, we compared, over a 24 h-period on day 1 and 7, % platelet acetylated COX-1 (AceCOX-1) with traditional pharmacokinetic and pharmacodynamics [i.e. serum thromboxane (TX) B-2, platelet function by monitoring CEPI(collagen/epinephrine) closure time (CT) using whole-blood PFA-100 and urinary excretion of 11-dehydro-TXB2] parameters. Results: Acetylation of platelet COX-1 was measurable before detection of aspirin levels in the systemic circulation and increased in a cumulative fashion upon repeated dosing. After the last dose of EC-aspirin, %AceCOX-1, serum TXB2 and CEPI-CT values were maximally and persistently modified throughout 24 h; they averaged 76 +/- 2%, 99.0 +/- 0.4% and 271 +/- 5 s, respectively. EC-aspirin caused 75% reduction in urinary 11-dehydro-TXB2 excretion. After chronic dosing with aspirin, the pharmacokinetics of acetylsalicylic acid was completely dissociated from pharmacodynamics. Conclusions: The demonstrated feasibility of quantifying the extent and duration of platelet COX-1 acetylation will allow characterizing the genetic, pharmacokinetic and pharmacodynamic determinants of the inter-individual variability in the antiplatelet response to low-dose aspirin as well as identifying extra-platelet sites of drug action.
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