PON1 Q192R genetic variant and response to clopidogrel and prasugrel: pharmacokinetics, pharmacodynamics, and a meta-analysis of clinical outcomes
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Clopidogrel and prasugrel are antiplatelet therapies commonly used to treat patients with cardiovascular disease. They are both pro-drugs requiring biotransformation into active metabolites. It has been proposed that a genetic variant Q192R (rs662 A>G) in PON1 significantly alters the biotransformation of clopidogrel and affects clinical outcomes; however, this assertion has limited support. The relationship between this variant and clinical outcomes with prasugrel has not been studied. We genotyped PON1 Q192R in 275 healthy subjects treated with clopidogrel or prasugrel and 2922 patients with an ACS undergoing PCI randomized to treatment with clopidogrel or prasugrel in the TRITON-TIMI 38 trial. A meta-analysis was performed including 13 studies and 16,760 clopidogrel-treated patients. Among clopidogrel-treated subjects, there were no associations between Q192R and active drug metabolite levels (P = 0.62) or change in platelet aggregation (P = 0.51). Consistent with these results, in clopidogrel-treated patients in TRITON-TIMI 38, there was no association between Q192R and the rates of CV death, myocardial infarction, or stroke (RR 11.2 %, QR 8.6 %, and QQ 9.3 %; P = 0.66) or stent thrombosis (RR 2.4 %, QR 0.7 %, and QQ 1.6 %, P = 0.30), with patients with the putative at-risk Q variant having numerically lower event rates. Likewise, among prasugrel-treated subjects, there were no associations between Q192R and active drug metabolite levels (P = 0.88), change in platelet aggregation (P = 0.97), or clinical outcomes (P = 0.72). In a meta-analysis, the Q variant was not significantly associated with MACE (QQ vs. RR 1.22, 95 % CI 0.84-1.76) or stent thrombosis (QQ vs. RR OR 1.36, 95 % CI 0.77-2.38). Furthermore, when restricted to the validation studies, the OR (95 % CI) for MACE and stent thrombosis were 0.99 (0.77-1.27) and 1.23 (0.74-2.03), respectively. In the present study, the Q192R genetic variant in PON1 was not associated with the pharmacologic or clinical response to clopidogrel, nor was it associated with the response to prasugrel. The meta-analysis reinforced a lack of a significant association between Q192R and cardiovascular outcomes in clopidogrel-treated patients.
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