Reduced-function CYP2C19 Research Articles

ACCF/ACG/AHA 2010 Expert Consensus Document on the Concomitant Use of Proton Pump Inhibitors and Thienopyridines: A Focused Update of the ACCF/ACG/AHA 2008 Expert Consensus Document on Reducing the Gastrointestinal Risks of Antiplatelet Therapy and NSAID Use

This expert consensus document was developed by the American College of Cardiology Foundation (ACCF), the American College of Gastroenterology (ACG), and the American Heart Association (AHA). Expert consensus documents inform practitioners, payers, and other interested parties of the opinion of ACCF and document cosponsors concerning evolving areas of clinical practice or medical technologies. Expert consensus documents cover topics for which the evidence base, experience with technology, or clinical practice is not considered sufficiently well developed to be evaluated by the formal ACCF/AHA Practice Guidelines process. Often, the topic is the subject of considerable ongoing investigation. Thus, the reader should view the expert consensus document as the best attempt of the ACCF and document cosponsors to inform clinical practice in areas where rigorous evidence may not yet be available. To avoid actual, potential, or perceived conflicts of interest that may arise as a result of industry relationships or personal interests among the writing committee, all members of the writing committee, as well as peer reviewers of the document, are asked to disclose all current healthcare-related relationships and those existing 12 months before initiation of the writing effort. The ACCF Task Force on Clinical Expert Consensus Documents (CECD) reviews these disclosures to determine which companies make products (on market or in development) that pertain to the document under development. Based on this information, a writing committee is formed to include a majority of members with no relevant relationships with industry (RWI), led by a chair with no relevant RWI. Authors with relevant RWI are not permitted to draft or vote on text or recommendations pertaining to their RWI. RWI are reviewed on all conference calls and updated as changes occur. Author and peer reviewer RWI pertinent to this document are disclosed in Appendixes 1 and 2, respectively. Additionally, to ensure complete transparency, …

Reduced-Function CYP2C19 Genotype and Risk of Adverse Clinical Outcomes Among Patients Treated With Clopidogrel Predominantly for PCI

Clopidogrel, one of the most commonly prescribed medications, is a prodrug requiring CYP450 biotransformation. Data suggest its pharmacologic effect varies based on CYP2C19 genotype, but there is uncertainty regarding the clinical risk imparted by specific genotypes. To define the risk of major adverse cardiovascular outcomes among carriers of 1 (≈ 26% prevalence in whites) and carriers of 2 (≈ 2% prevalence in whites) reduced-function CYP2C19 genetic variants in patients treated with clopidogrel. A literature search was conducted (January 2000-August 2010) in MEDLINE, Cochrane Database of Systematic Reviews, and EMBASE. Genetic studies were included in which clopidogrel was initiated in predominantly invasively managed patients in a manner consistent with the current guideline recommendations and in which clinical outcomes were ascertained. Investigators from 9 studies evaluating CYP2C19 genotype and clinical outcomes in patients treated with clopidogrel contributed the relevant hazard ratios (HRs) and 95% confidence intervals (CIs) for specific cardiovascular outcomes by genotype. Among 9685 patients (91.3% who underwent percutaneous coronary intervention and 54.5% who had an acute coronary syndrome), 863 experienced the composite end point of cardiovascular death, myocardial infarction, or stroke; and 84 patients had stent thrombosis among the 5894 evaluated for such. Overall, 71.5% were noncarriers, 26.3% had 1 reduced-function CYP2C19 allele, and 2.2% had 2 reduced-function CYP2C19 alleles. A significantly increased risk of the composite end point was evident in both carriers of 1 (HR, 1.55; 95% CI, 1.11-2.17; P = .01) and 2 (HR, 1.76; 95% CI, 1.24-2.50; P = .002) reduced-function CYP2C19 alleles, as compared with noncarriers. Similarly, there was a significantly increased risk of stent thrombosis in both carriers of 1 (HR, 2.67; 95% CI, 1.69-4.22; P < .0001) and 2 (HR, 3.97; 95% CI, 1.75-9.02; P = .001) CYP2C19 reduced-function alleles, as compared with noncarriers. Among patients treated with clopidogrel for percutaneous coronary intervention, carriage of even 1 reduced-function CYP2C19 allele appears to be associated with a significantly increased risk of major adverse cardiovascular events, particularly stent thrombosis.

Clopidogrel and the Reduced-Function CYP2C19 Genetic Variant

FFECTIVE PLATELET INHIBITION HAS BECOME A CORnerstone in the management of patients with acute coronary syndrome (ACS). The addition of clopidogrel to aspirin has provided significant reductions in major cardiovascular events in patients with ACS in general, and particularly among those treated invasively by percutaneous coronary intervention (PCI). 1 Yet studies have demonstrated that the therapeutic response of clopidogrel is variable among patients, 2 and low or incomplete platelet inhibition has been associated with increased risk

New P2Y12 antagonists

The P2Y12 antagonist clopidogrel has a well established role as an antithrombotic agent in the settings of percutaneous coronary intervention and acute coronary syndromes. However, clopidogrel has a number of disadvantages that have led to the development of new P2Y12 antagonists. This article reviews the current status of clopidogrel and these new P2Y12 antagonists. A poor response to clopidogrel as measured by in-vitro platelet function assays is associated with a poor clinical response to clopidogrel. A patient's response to clopidogrel is partly dependent on factors that decrease (reduced-function CYP2C19 allele; omeprazole) or increase (cigarette smoking) the metabolism of clopidogrel through cytochrome P450 in the liver. Novel P2Y12 antagonists (prasugrel, ticagrelor, cangrelor, and elinogrel) that have advantages over clopidogrel - including more rapid, less variable, and more complete inhibition of platelet function - are in various phases of development. The clinical benefit of changing clopidogrel treatment based on platelet function tests, single-nucleotide polymorphisms, or both is as yet unproven. Novel P2Y12 antagonists are under investigation to determine whether they can result in better, more rapid, or both, antithrombotic effects than clopidogrel, without an unacceptable increase in hemorrhagic or other side effects.

Cytochrome P-450 Polymorphisms and Response to Clopidogrel

Clopidogrel requires transformation into an active metabolite by cytochrome P-450 (CYP) enzymes for its antiplatelet effect. The genes encoding CYP enzymes are polymorphic, with common alleles conferring reduced function.We tested the association between functional genetic variants in CYP genes, plasma concentrations of active drug metabolite, and platelet inhibition in response to clopidogrel in 162 healthy subjects. We then examined the association between these genetic variants and cardiovascular outcomes in a separate cohort of 1477 subjects with acute coronary syndromes who were treated with clopidogrel in the Trial to Assess Improvement in Therapeutic Outcomes by Optimizing Platelet Inhibition with Prasugrel-Thrombolysis in Myocardial Infarction (TRITON-TIMI) 38.In healthy subjects who were treated with clopidogrel, carriers of at least one CYP2C19 reduced-function allele (approximately 30% of the study population) had a relative reduction of 32.4% in plasma exposure to the active metabolite of clopidogrel, as compared with noncarriers (P<0.001). Carriers also had an absolute reduction in maximal platelet aggregation in response to clopidogrel that was 9 percentage points less than that seen in noncarriers (P<0.001). Among clopidogrel-treated subjects in TRITON-TIMI 38, carriers had a relative increase of 53% in the composite primary efficacy outcome of the risk of death from cardiovascular causes, myocardial infarction, or stroke, as compared with noncarriers (12.1% vs. 8.0%; hazard ratio for carriers, 1.53; 95% confidence interval [CI], 1.07 to 2.19; P=0.01) and an increase by a factor of 3 in the risk of stent thrombosis (2.6% vs. 0.8%; hazard ratio, 3.09; 95% CI, 1.19 to 8.00; P=0.02).Among persons treated with clopidogrel, carriers of a reduced-function CYP2C19 allele had significantly lower levels of the active metabolite of clopidogrel, diminished platelet inhibition, and a higher rate of major adverse cardiovascular events, including stent thrombosis, than did noncarriers.

Germline Pharmacogenetics of Tamoxifen Response: Have We Learned Enough?

Germline Pharmacogenetics of Tamoxifen Response: Have We Learned Enough?