Cytochrome P450 2C19*2 polymorphism and cardiovascular recurrences in patients taking clopidogrel: a meta-analysis

Several polymorphisms in genes that encode platelet components (receptors or enzymes), or cytochrome P450 enzyme isoforms, involved in clopidogrel metabolism, have been proposed as possible mechanisms for nonresponsiveness to clopidogrel. Among them, a great deal of attention has been focused on the loss-of-function CYP2C19*2 (or 681 G>A) polymorphism. We performed a meta-analysis of all the prospective studies that have been published, which analyze the role of such a polymorphism in recurrent cardiovascular events in patients with coronary artery disease (CAD) being treated with clopidogrel. Studies were searched in MedLine, Embase, Web of Science, The Cochrane Systematic Review Database, Google Scholar and bibliographies of retrieved articles up to January 2010. The principal underlying hypothesis was that the presence of the *2 variant allele of the polymorphism would be associated with an increased risk of clinical recurrence. Data were available for a total of 8043 patients from seven cohort prospective studies, who were followed for a period of time ranging from 6 months to 8.3 years. The summary risk ratios (RRs) for the prospective cohort studies included showed a significant association between the CYP2C19*2 polymorphism and an increased risk of major adverse cardiovascular events in the follow-up (RR: 1.96 (1.14–3.37); P=0.02). When studies evaluating stent thrombosis (n=4) for a total of 4975 patients were considered, the presence of the variant allele was associated with an increased risk of stent thrombosis (RR: 3.82 (2.23–6.54); P=0.0001). The current meta-analysis, carried out on nearly 8000 patients with CAD undergoing clopidogrel treatment, shows that the CYP2C19*2 polymorphism is associated with an increased risk of major adverse cardiovascular events and stent thrombosis.