Derivation, Validation, and Prognostic Utility of a Prediction Rule for Nonresponse to Clopidogrel

Platelet Inhibition with Ticagrelor versus Clopidogrel in Diabetic Patients after Percutaneous Coronary Intervention for Chronic Coronary Syndromes

BACKGROUND

 Clopidogrel is currently the only P2Y₁₂ inhibitor with class I recommendation in patients after percutaneous coronary intervention (PCI) for chronic coronary syndromes (CCS). Diabetic patients have reduced therapeutic response to clopidogrel.

PURPOSE

 This study assessed the antiplatelet effect of ticagrelor versus clopidogrel in diabetic patients after recent PCI for CCS.

METHODS

 Eligible patients were randomly assigned to receive ticagrelor 90 mg twice daily or clopidogrel 75 mg once daily, in addition to aspirin 100 mg once daily for 15 days. P2Y₁₂ reaction unit (PRU) and percent inhibition were measured by VerifyNow P2Y₁₂ assay. High on-treatment platelet reactivity (HOPR) was defined as PRU > 208. Bleeding was assessed by the Platelet Inhibition and Patient Outcomes criteria. Cardiac ischemic events were evaluated as adverse events.

RESULTS

 The baseline characteristics of the patients (n = 39) were well balanced between the two groups. Both before and 2 to 4 hours after the final study dose on day 15, PRU was lower (41.3 ± 35.8 vs. 192.6 ± 49.5, p < 0.001; 36.6 ± 25.8 vs. 187.6 ± 70.9, p < 0.001), percent inhibition was higher (83.0% [70.5%, 96.0%] vs. 16.0% [0%, 25.0%], p < 0.001; 85.0% [76.0%, 96.5%] vs. 25.0% [0%, 39.0%], p < 0.001), and HOPR occurred less frequently (0% [0/20] vs. 26.3% [5/19], p = 0.020; 0% [0/20] vs. 31.6% [6/19], p = 0.008) in the ticagrelor group (n = 20) compared with the clopidogrel group (n = 19). No major or minor bleeding, or serious adverse events occurred in both groups.

CONCLUSION

 Ticagrelor achieved greater peak and trough platelet inhibition than did clopidogrel in diabetic patients after recent PCI for CCS, which suggests the potential use of ticagrelor in this clinical setting.

Genomewide Association Study of Platelet Reactivity and Cardiovascular Response in Patients Treated With Clopidogrel: A Study by the International Clopidogrel Pharmacogenomics Consortium

Antiplatelet response to clopidogrel shows wide variation, and poor response is correlated with adverse clinical outcomes. CYP2C19 loss‐of‐function alleles play an important role in this response, but account for only a small proportion of variability in response to clopidogrel. An aim of the International Clopidogrel Pharmacogenomics Consortium (ICPC) is to identify other genetic determinants of clopidogrel pharmacodynamics and clinical response. A genomewide association study (GWAS) was performed using DNA from 2,750 European ancestry individuals, using adenosine diphosphate‐induced platelet reactivity and major cardiovascular and cerebrovascular events as outcome parameters. GWAS for platelet reactivity revealed a strong signal for CYP2C19*2 (P value = 1.67e−33). After correction for CYP2C19*2 no other single‐nucleotide polymorphism reached genomewide significance. GWAS for a combined clinical end point of cardiovascular death, myocardial infarction, or stroke (5.0% event rate), or a combined end point of cardiovascular death or myocardial infarction (4.7% event rate) showed no significant results, although in coronary artery disease, percutaneous coronary intervention, and acute coronary syndrome subgroups, mutations in SCOS5P1, CDC42BPA, and CTRAC1 showed genomewide significance (lowest P values: 1.07e−09, 4.53e−08, and 2.60e−10, respectively). CYP2C19*2 is the strongest genetic determinant of on‐clopidogrel platelet reactivity. We identified three novel associations in clinical outcome subgroups, suggestive for each of these outcomes.