Summary Antithrombotic drugs, which include antiplatelet and anticoagulant therapies, prevent and treat many cardiovascular disorders and, as such, are some of the most commonly prescribed drugs ...worldwide. The first drugs designed to inhibit platelets or coagulation factors, such as the antiplatelet clopidogrel and the anticoagulant warfarin, significantly reduced the risk of thrombotic events at the cost of increased bleeding in patients. However, both clopidogrel and warfarin have some pharmacological limitations including interpatient variability in antithrombotic effects in part due to the metabolism, interactions (eg, drug, environment, and genetic), or targets of the drugs. Increased knowledge of the pharmacology of antithrombotic drugs and the mechanisms underlying thrombosis has led to the development of newer drugs with faster onset of action, fewer interactions, and less interpatient variability in their antithrombotic effects than previous antithrombotic drugs. Treatment options now include the next-generation antiplatelet drugs prasugrel and ticagrelor, and, in terms of anticoagulants, inhibitors that directly target factor IIa (dabigatran) or Xa (rivaroxaban, apixaban, edoxaban) are available. In this Series paper we review the pharmacological properties of these most commonly used oral antithrombotic drugs, and explore the development of antiplatelet and anticoagulant therapies.
Summary Background Clopidogrel and prasugrel are subject to efflux via P-glycoprotein (encoded by ABCB1 , also known as MDR1 ). ABCB1 polymorphisms, particularly 3435C→T, may affect drug transport ...and efficacy. We aimed to assess the effect of this polymorphism by itself and alongside variants in CYP2C19 on cardiovascular outcomes in patients treated with clopidogrel or prasugrel in TRITON–TIMI 38. We also assessed the effect of genotype on the pharmacodynamic and pharmacokinetic properties of these drugs in healthy individuals. Methods We genotyped ABCB1 in 2932 patients with acute coronary syndromes undergoing percutaneous intervention who were treated with clopidogrel (n=1471) or prasugrel (n=1461) in the TRITON–TIMI 38 trial. We evaluated the association between ABCB1 3435C→T and rates of the primary efficacy endpoint (cardiovascular death, myocardial infarction, or stroke) until 15 months. We then assessed the combined effect of ABCB1 3435C→T genotype and reduced-function alleles of CYP2C19 . 321 healthy individuals were also genotyped, and we tested the association of genetic variants with reduction in maximum platelet aggregation and plasma concentrations of active drug metabolites. Findings In patients treated with clopidogrel, ABCB1 3435C→T genotype was significantly associated with the risk of cardiovascular death, myocardial infarction, or stroke (p=0·0064). TT homozygotes had a 72% increased risk of the primary endpoint compared with CT/CC individuals (Kaplan-Meier event rates 12·9% 52 of 414 vs 7·8% 80 of 1057 participants; HR 1·72, 95% CI 1·22–2·44, p=0·002). ABCB1 3435C→T and CYP2C19 genotypes were significant, independent predictors of the primary endpoint, and 681 (47%) of the 1454 genotyped patients taking clopidogrel who were either CYP2C19 reduced-function allele carriers, ABCB1 3435 TT homozygotes, or both were at increased risk of the primary endpoint (HR 1·97, 95% CI 1·38–2·82, p=0·0002). In healthy participants, 3435 TT homozygotes had an absolute reduction in maximum platelet aggregation with clopidogrel that was 7·3 percentage points less than for CT/CC individuals (p=0·0127). ABCB1 genotypes were not significantly associated with clinical or pharmacological outcomes in patients with an acute coronary syndrome or healthy individuals treated with prasugrel, respectively. Interpretation Individuals with the ABCB1 3435 TT genotype have reduced platelet inhibition and are at increased risk of recurrent ischaemic events during clopidogrel treatment. In patients with acute coronary syndromes who have undergone percutaneous intervention, when both ABCB1 and CYP2C19 are taken into account, nearly half of the population carries a genotype associated with increased risk of major adverse cardiovascular events while on standard doses of clopidogrel. Funding Daiichi Sankyo Company Ltd and Eli Lilly and Company.
Summary Background Proton-pump inhibitors (PPIs) are often prescribed in combination with thienopyridines. Conflicting data exist as to whether PPIs diminish the efficacy of clopidogrel. We assessed ...the association between PPI use, measures of platelet function, and clinical outcomes for patients treated with clopidogrel or prasugrel. Methods In the PRINCIPLE-TIMI 44 trial, the primary outcome was inhibition of platelet aggregation at 6 h assessed by light-transmission aggregometry. In the TRITON-TIMI 38 trial, the primary endpoint was the composite of cardiovascular death, myocardial infarction, or stroke. In both studies, PPI use was at physician's discretion. We used a multivariable Cox model with propensity score to assess the association of PPI use with clinical outcomes. Findings In the PRINCIPLE-TIMI 44 trial, 201 patients undergoing elective percutaneous coronary intervention were randomly assigned to prasugrel (n=102) or high-dose clopidogrel (n=99). Mean inhibition of platelet aggregation was significantly lower for patients on a PPI than for those not on a PPI at 6 h after a 600 mg clopidogrel loading dose (23·2±19·5% vs 35·2±20·9%, p=0·02), whereas a more modest difference was seen with and without a PPI after a 60 mg loading dose of prasugrel (69·6±13·5% vs 76·7±12·4%, p=0·054). In the TRITON-TIMI 38 trial, 13 608 patients with an acute coronary syndrome were randomly assigned to prasugrel (n=6813) or clopidogrel (n=6795). In this study, 33% (n=4529) of patients were on a PPI at randomisation. No association existed between PPI use and risk of the primary endpoint for patients treated with clopidogrel (adjusted hazard ratio HR 0·94, 95% CI 0·80–1·11) or prasugrel (1·00, 0·84–1·20). Interpretation The current findings do not support the need to avoid concomitant use of PPIs, when clinically indicated, in patients receiving clopidogrel or prasugrel. Funding Daiichi Sankyo Company Limited and Eli Lilly and Company sponsored the trials. This analysis had no funding.
Summary Background Warfarin is the most widely used oral anticoagulant worldwide, but serious bleeding complications are common. We tested whether genetic variants can identify patients who are at ...increased risk of bleeding with warfarin and, consequently, those who would derive a greater safety benefit with a direct oral anticoagulant rather than warfarin. Methods ENGAGE AF-TIMI 48 was a randomised, double-blind trial in which patients with atrial fibrillation were assigned to warfarin to achieve a target international normalised ratio of 2·0–3·0, or to higher-dose (60 mg) or lower-dose (30 mg) edoxaban once daily. A subgroup of patients was included in a prespecified genetic analysis and genotyped for variants in CYP2C9 and VKORC1 . The results were used to create three genotype functional bins (normal, sensitive, and highly sensitive responders to warfarin). This trial is registered with ClinicalTrials.gov , number NCT00781391. Findings 14 348 patients were included in the genetic analysis. Of 4833 taking warfarin, 2982 (61·7%) were classified as normal responders, 1711 (35·4%) as sensitive responders, and 140 (2·9%) as highly sensitive responders. Compared with normal responders, sensitive and highly sensitive responders spent greater proportions of time over-anticoagulated in the first 90 days of treatment (median 2·2%, IQR 0–20·2; 8·4%, 0–25·8; and 18·3%, 0–32·6; ptrend <0·0001) and had increased risks of bleeding with warfarin (sensitive responders hazard ratio 1·31, 95% CI 1·05–1·64, p=0·0179; highly sensitive responders 2·66, 1·69–4·19, p<0·0001). Genotype added independent information beyond clinical risk scoring. During the first 90 days, when compared with warfarin, treatment with edoxaban reduced bleeding more so in sensitive and highly sensitive responders than in normal responders (higher-dose edoxaban pinteraction =0·0066; lower-dose edoxaban pinteraction =0·0036). After 90 days, the reduction in bleeding risk with edoxaban versus warfarin was similarly beneficial across genotypes. Interpretation CYP2C9 and VKORC1 genotypes identify patients who are more likely to experience early bleeding with warfarin and who derive a greater early safety benefit from edoxaban compared with warfarin. Funding Daiichi Sankyo.
Summary Background Genetic variants have been associated with the risk of coronary heart disease. In this study, we tested whether or not a composite of these variants could ascertain the risk of ...both incident and recurrent coronary heart disease events and identify those individuals who derive greater clinical benefit from statin therapy. Methods A community-based cohort study (the Malmo Diet and Cancer Study) and four randomised controlled trials of both primary prevention (JUPITER and ASCOT) and secondary prevention (CARE and PROVE IT-TIMI 22) with statin therapy, comprising a total of 48 421 individuals and 3477 events, were included in these analyses. We studied the association of a genetic risk score based on 27 genetic variants with incident or recurrent coronary heart disease, adjusting for traditional clinical risk factors. We then investigated the relative and absolute risk reductions in coronary heart disease events with statin therapy stratified by genetic risk. We combined data from the different studies using a meta-analysis. Findings When individuals were divided into low (quintile 1), intermediate (quintiles 2–4), and high (quintile 5) genetic risk categories, a significant gradient in risk for incident or recurrent coronary heart disease was shown. Compared with the low genetic risk category, the multivariable-adjusted hazard ratio for coronary heart disease for the intermediate genetic risk category was 1·34 (95% CI 1·22–1·47, p<0·0001) and that for the high genetic risk category was 1·72 (1·55–1·92, p<0·0001). In terms of the benefit of statin therapy in the four randomised trials, we noted a significant gradient (p=0·0277) of increasing relative risk reductions across the low (13%), intermediate (29%), and high (48%) genetic risk categories. Similarly, we noted greater absolute risk reductions in those individuals in higher genetic risk categories (p=0·0101), resulting in a roughly threefold decrease in the number needed to treat to prevent one coronary heart disease event in the primary prevention trials. Specifically, in the primary prevention trials, the number needed to treat to prevent one such event in 10 years was 66 in people at low genetic risk, 42 in those at intermediate genetic risk, and 25 in those at high genetic risk in JUPITER, and 57, 47, and 20, respectively, in ASCOT. Interpretation A genetic risk score identified individuals at increased risk for both incident and recurrent coronary heart disease events. People with the highest burden of genetic risk derived the largest relative and absolute clinical benefit from statin therapy. Funding National Institutes of Health.
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