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ARCTIC-GENE: Clopidogrel monitoring failed to improve outcomes

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AMSTERDAM — Researchers of the ARCTIC-GENE study have reported that clopidogrel monitoring does not improve clinical outcomes in a cohort of patients with a demonstrated poor response to antiplatelet therapy.

The ARCTIC-GENE study included 2,440 patients who were scheduled for stent implantation. One cohort was assigned platelet function monitoring with drug adjustment and the other cohort received a conventional strategy without monitoring or drug adjustment.

Death, MI, stroke, stent thrombosis and urgent revascularization at 1 year after stent implantation served as the primary endpoint. Major bleeding evaluated according to the genetic metabolic profile and the strategy of platelet function testing served as the secondary safety outcome measure.

After obtaining DNA samples for 1,420 patients, the researchers genotyped patients for CYP2C19 genes related to platelet reactivity. They then classified the cohorts according to clopidogrel predicted metabolic phenotype.

Carriers of at least one loss-of-function allele (CYP2C19*2) were defined as slow or reduced metabolizers, and extensive or rapid metabolizers were carriers of at least one gain-of-function allele (CYP2C19*17) or carriers of both one gain and one loss-of-function allele (CYP2C19*2 and CYP2C19*17). There were 935 slow metabolizers and 459 rapid metabolizers included in the final analysis.

The rate of the composite primary endpoint was 32.7% among slow metabolizers and 32.2% in the rapid group (HR=0.99; 95% CI, 0.81-1.20). Death or MI occurred in 30.5% of the slow metabolizing group and 29.3% of the rapid group (HR=0.97; 95% CI, 0.79-1.18). The rates for stent thrombosis or urgent revascularization were 4.4% in the slow group and 5.7% in the rapid group (HR=1.31; 95% CI, 0.79-2.20).

Major or minor bleeding was reported in 3.5% of patients in the slow metabolizing group and 3.6% of the rapid metabolizing group (HR=1.05; 95% CI, 0.58-1.90). Major bleeding occurred in 3.1% of the slow arm and 2.2% of the rapid arm (HR=0.74; 95% CI, 0.38-1.45), and minor bleeding rates were 0.9% for slow metabolizers and 1.7% for rapid (HR=1.98; 95% CI, 0.66-5.93).

The researchers did not observe an improvement in clinical outcomes in the monitoring cohort. Slow metabolizers were more likely to have a poor response at randomization and at day 14, according to the findings. There also was low concordance and discrimination. Predicted clopidogrel metabolizer profile is not associated with treatment adjustment in poor responders.

For more information:

Collet JP. Clinical Trial Update Hot Line III: Updates on risk and outcome. Presented at: the European Society of Cardiology Congress; Aug. 31-Sept. 4, 2013; Amsterdam.

Disclosure: Collet reports financial relationships with Abbot Vascular, AstraZeneca, Bayer, Boston Scientific, Cordis, Daiichi Sankyo, Duke Institute, Eli Lilly, Europa, Federation Francaise de la Cardiologie, Fondation de France, GlaxoSmithKline, ICM, Inserm, Medtronic, Nanospheres, Sanofi-Aventis, Societe Francaise de Cardiologie, The Medicines Company and the TIMI Group.