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Published on: November 8, 2024
Dosing clopidogrel based on CYP2C19 genotype and the effect on platelet reactivity in patients with stable
Jessica L Mega1, Willibald Hochholzer, Andrew L Frelinger
1TIMI Study Group, Cardiovascular Division, Department of Medicine, Brigham and Women's Hospital, 75 Francis St, Boston, MA 02115, USA. jmega@partners.org
Insights
Higher clopidogrel doses improve antiplatelet response in CYP2C19*2 heterozygotes. Tripling the dose to 225 mg daily normalized platelet reactivity, but homozygotes showed limited response even at 300 mg.
Area of Science:
- Pharmacogenomics
- Cardiovascular Medicine
- Clinical Pharmacology
Background:
- CYP2C19 gene variants significantly impact patient response to clopidogrel, a standard antiplatelet medication.
- Understanding these genetic influences is crucial for optimizing antiplatelet therapy and preventing thrombotic events.
Purpose of the Study:
- To evaluate the efficacy of increased clopidogrel maintenance doses (up to 300 mg daily) in patients with loss-of-function CYP2C19 genotypes.
- To determine if higher doses can overcome genetic variations affecting clopidogrel response.
Main Methods:
- ELEVATE-TIMI 56 was a multicenter, randomized, double-blind trial involving 333 patients with cardiovascular disease.
- Patients were genotyped for CYP2C19*2 loss-of-function alleles and received varying clopidogrel doses (75-300 mg daily) over four treatment periods.
- Platelet function was assessed using VASP phosphorylation and VerifyNow P2Y(12) assays.
Main Results:
- CYP2C19*2 heterozygotes exhibited higher platelet reactivity on standard 75 mg clopidogrel compared to noncarriers.
- Increasing clopidogrel doses up to 300 mg significantly reduced platelet reactivity in heterozygotes, with 225 mg achieving levels similar to 75 mg in noncarriers.
- A substantial reduction in non-responders was observed with higher doses in heterozygotes (52% to 10%).
- CYP2C19*2 homozygotes showed limited platelet inhibition even with 300 mg clopidogrel.
Conclusions:
- A 225 mg daily dose of clopidogrel effectively normalized platelet reactivity in CYP2C19*2 heterozygotes, similar to the standard dose in noncarriers.
- Higher clopidogrel doses (up to 300 mg) were insufficient to achieve comparable platelet inhibition in CYP2C19*2 homozygotes.
- Dose adjustment based on CYP2C19 genotype may be a strategy to optimize clopidogrel therapy in specific patient populations.
Context:
Variants in the CYP2C19 gene influence the pharmacologic and clinical response to the standard 75-mg daily maintenance dose of the antiplatelet drug clopidogrel.
Objective:
To test whether higher doses (up to 300 mg daily) improve the response to clopidogrel in the setting of loss-of-function CYP2C19 genotypes.
Design, Setting, And Patients:
ELEVATE-TIMI 56 was a multicenter, randomized, double-blind trial that enrolled and genotyped 333 patients with cardiovascular disease across 32 sites from October 2010 until September 2011.
Interventions:
Maintenance doses of clopidogrel for 4 treatment periods, each lasting approximately 14 days, based on genotype. In total, 247 noncarriers of a CYP2C19*2 loss-of-function allele were to receive 75 and 150 mg daily of clopidogrel (2 periods each), whereas 86 carriers (80 heterozygotes, 6 homozygotes) were to receive 75, 150, 225, and 300 mg daily.
Main Outcome Measures:
Platelet function test results (vasodilator-stimulated phosphoprotein [VASP] phosphorylation and VerifyNow P2Y(12) assays) and adverse events.
Results:
With 75 mg daily, CYP2C19*2 heterozygotes had significantly higher on-treatment platelet reactivity than did noncarriers (VASP platelet reactivity index [PRI]: mean, 70.0%; 95% CI, 66.0%-74.0%, vs 57.5%; 95% CI, 55.1%-59.9%, and VerifyNow P2Y(12) reaction units [PRU]: mean, 225.6; 95% CI, 207.7-243.4, vs 163.6; 95% CI, 154.4-173.9; P < .001 for both comparisons). Among CYP2C19*2 heterozygotes, doses up to 300 mg daily significantly reduced platelet reactivity, with VASP PRI decreasing to 48.9% (95% CI, 44.6%-53.2%) and PRU to 127.5 (95% CI, 109.9-145.2) (P < .001 for trend across doses for both). Whereas 52% of CYP2C19*2 heterozygotes were nonresponders (≥230 PRU) with 75 mg of clopidogrel, only 10% were nonresponders with 225 or 300 mg (P < .001 for both). Clopidogrel, 225 mg daily, reduced platelet reactivity in CYP2C19*2 heterozygotes to levels achieved with standard clopidogrel, 75 mg, in noncarriers (mean ratios of platelet reactivity, VASP PRI, 0.92; 90% CI, 0.85-0.99, and PRU, 0.94; 90% CI, 0.84-1.04). In CYP2C19*2 homozygotes, even with 300 mg daily of clopidogrel, mean VASP PRI was 68.3% (95% CI, 44.9%-91.6%) and mean PRU, 287.0 (95% CI, 170.2-403.8).
Conclusion:
Among patients with stable cardiovascular disease, tripling the maintenance dose of clopidogrel to 225 mg daily in CYP2C19*2 heterozygotes achieved levels of platelet reactivity similar to that seen with the standard 75-mg dose in noncarriers; in contrast, for CYP2C19*2 homozygotes, doses as high as 300 mg daily did not result in comparable degrees of platelet inhibition.
Trial Registration:
clinicaltrials.gov Identifier: NCT01235351.
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