Genetic Determinants of Dabigatran Plasma Levels and Their Relation to Bleeding
ABSTRACT BACKGROUND: Fixed-dose unmonitored treatment with dabigatran etexilate is effective and has a favorable safety profile in prevention of stroke in atrial fibrillation patients compared to warfarin. We hypothesized that genetic variants could contribute to inter-individual variability in blood concentrations of the active metabolite of dabigatran etexilate, and influence the safety and efficacy of dabigatran. METHODS AND RESULTS: We successfully conducted a genome-wide association study in 2,944 RE-LY participants. The CES1 SNP rs2244613 was associated with trough concentrations, and the ABCB1 SNP rs4148738 and CES1 SNP rs8192935 were associated with peak concentrations at genome-wide significance (P<9 x 10-8) with a gene-dose effect. Each minor allele of the CES1 SNP rs2244613 was associated with lower trough concentrations (15% decrease per allele, 95%CI 10-19%; P=1.2 x 10-8) and a lower risk of any bleeding (OR=0.67, 95%CI 0.55-0.82; P=7 x 10-5) in dabigatran-treated participants, with a consistent but non-significant lower risk of major bleeding (OR=0.66, 95%CI 0.43-1.01). The interaction between treatment (warfarin versus all dabigatran) and carrier status was statistically significant (P=0.002) with carriers having less bleeding with dabigatran than warfarin (HR=0.59, 95%CI 0.46-0.76; P=5.2 x 10-5) in contrast to no difference in noncarriers (HR=0.96, 95%CI 0.81-1.14; P=0.65). There was no association with ischemic events, and neither rs4148738 nor rs8192935 was associated with bleeding or ischemic events. CONCLUSIONS: Genome-wide association analysis identified that carriage of CES1 rs2244613 minor allele occurred in 32.8% of patients in RELY and was associated with lower exposure to active dabigatran metabolite. The presence of the polymorphism was associated with a lower risk of bleeding. CLINICAL TRIAL REGISTRATION INFORMATION: ClinicalTrials.gov; Identifier: NCT00262600.
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ABSTRACT: The past decade has seen tremendous advances in our understanding of the genetic factors influencing response to a variety of drugs, including those targeted at treatment of cardiovascular diseases. In the case of clopidogrel, warfarin, and statins, the literature has become sufficiently strong that guidelines are now available describing the use of genetic information to guide treatment with these therapies, and some health centers are using this information in the care of their patients. There are many challenges in moving from research data to translation to practice; we discuss some of these barriers and the approaches some health systems are taking to overcome them. The body of literature that has led to the clinical implementation of CYP2C19 genotyping for clopidogrel, VKORC1, CYP2C9; and CYP4F2 for warfarin; and SLCO1B1 for statins is comprehensively described. We also provide clarity for other genes that have been extensively studied relative to these drugs, but for which the data are conflicting. Finally, we comment briefly on pharmacogenetics of other cardiovascular drugs and highlight β-blockers as the drug class with strong data that has not yet seen clinical implementation. It is anticipated that genetic information will increasingly be available on patients, and it is important to identify those examples where the evidence is sufficiently robust and predictive to use genetic information to guide clinical decisions. The review herein provides several examples of the accumulation of evidence and eventual clinical translation in cardiovascular pharmacogenetics.Pharmacological reviews 04/2013; 65(3):987-1009. DOI:10.1124/pr.112.007252 · 18.55 Impact Factor
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ABSTRACT: Warfarin has been the mainstay oral anticoagulant (OAC) medication prescribed for stroke prevention in atrial fibrillation (AF) patients. However, warfarin therapy is challenging because of marked interindividual variability in dose and response, requiring frequent monitoring and dose titration. These limitations have prompted the clinical development of new OACs (NOACs) that directly target the coagulation cascade with rapid onset/offset of action, lower risk for drug-drug interactions, and more predictable response. Recently, NOACs dabigatran (direct thrombin inhibitor), and rivaroxaban and apixaban (factor Xa [FXa] inhibitors) have gained regulatory approval as alternative therapies to warfarin. Though the anticoagulation efficacy of these NOACs has been characterized, differences in their pharmacokinetic and pharmacodynamic profiles have become a significant consideration in terms of drug selection and dosing. In this review, we outline key pharmacokinetic and pharmacodynamic features of each compound and provide guidance on selection and dosing of the 3 NOACs relative to warfarin when considering OAC therapy for AF patients. Importantly, we show that by better understanding the effect of clinical variables such as age, renal function, dosing interval, and drug metabolism (CYP3A4) and transport (P-glycoprotein), we might be able to better predict the risk for sub- and supratherapeutic anticoagulation response and individualize OAC selection and dosing.The Canadian journal of cardiology 07/2013; 29(7 Suppl):S24-33. DOI:10.1016/j.cjca.2013.04.002 · 3.94 Impact Factor
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ABSTRACT: Warfarin is effective for the prevention and treatment of thromboembolism but produces variable anticoagulant effects and requires routine monitoring of the international normalized ratio (INR) to optimize the balance between efficacy and safety. The new oral anticoagulants (NOACs) have a more predictable anticoagulant effect and were recently demonstrated to be at least as efficacious and safe as warfarin despite being administered in fixed doses without routine coagulation monitoring. Specific laboratory tests have been developed to measure the anticoagulant effect of the NOACs but are not yet widely available, and the relation between drug levels and both coagulation test results and outcomes is uncertain. It remains to be demonstrated whether adjustment of the dose of NOACs, according to the results of laboratory testing, may lead to even greater efficacy and safety. The principles of bleeding management in patients treated with NOACs compared with patients receiving warfarin are similar. Most patients can be safely managed by interrupting drug treatment, performing local measures to stem the bleeding, and providing transfusion support as required. In patients with major or life-threatening bleeding and those requiring surgery, the anticoagulant effects of warfarin can be reversed using oral or intravenous vitamin K, fresh frozen plasma (FFP), and prothrombin complex concentrates (PCCs). Specific antidotes are under development for the NOACs but are not yet approved for clinical use. PCCs and recombinant factor VIIa may improve hemostasis in patients in whom bleeding develops during treatment with a NOAC, but their efficacy is unproven.The Canadian journal of cardiology 07/2013; 29(7 Suppl):S34-44. DOI:10.1016/j.cjca.2013.04.013 · 3.94 Impact Factor