The genetic architecture of the MHC class II region in British Texel sheep

Understanding the structure of the major histocompatibility complex, especially the number and frequency of alleles, loci and haplotypes, is crucial for efficient investigation of the way in which the MHC influences susceptibility to disease. Nematode infection is one of the most important diseases suffered by sheep, and the class II region has been repeatedly associated with differences in susceptibility and resistance to infection. Texel sheep are widely used in many different countries and are relatively resistant to infection. This study determined the number and frequency of MHC class II genes in a small flock of Texel sheep. There were 18 alleles at DRB1, 9 alleles at DQA1, 13 alleles at DQB1, 8 alleles at DQA2 and 16 alleles at DQB2. Several haplotypes had no detectable gene products at DQA1, DQB1 or DQB2, and these were defined as null alleles. Despite the large numbers of alleles, there were only 21 distinct haplotypes in the population. The relatively small number of observed haplotypes will simplify finding disease associations because common haplotypes provide more statistical power but complicate the discrimination of causative mutations from linked marker loci

CYP2C19 genotype-guided antiplatelet therapy in ST-segment elevation myocardial infarction patients-Rationale and design of the Patient Outcome after primary PCI (POPular) Genetics study

RATIONALE: In patients with ST-segment elevation myocardial infarction (STEMI) who undergo primary percutaneous coronary intervention (pPCI), the use of dual antiplatelet therapy is essential to prevent atherothrombotic complications. Therefore, patients are treated with acetylsalicylic acid and clopidogrel, prasugrel, or ticagrelor. Clopidogrel, however, shows a major interindividual variation in antiplatelet effect, which is correlated to an increase in atherothrombotic events in patients with high platelet reactivity. This interindividual variation is partly a result of CYP2C19 genetic variants. Ticagrelor and prasugrel reduce atherothrombotic events but increase bleeding rate and drug costs, as compared with clopidogrel. CYP2C19-based tailoring of antiplatelet therapy might be beneficial to STEMI patients. STUDY DESIGN: POPular Genetics (NCT01761786) is a randomized, open-label, multicenter trial involving 2,700 STEMI patients who undergo pPCI. Patients are randomized to CYP2C19 genotyping or routine ticagrelor or prasugrel treatment. In the genotyping group, *1/*1 (wild-type) patients receive clopidogrel, and patients carrying 1 or 2 *2 or *3 loss-of-function alleles receive ticagrelor or prasugrel. The primary net clinical benefit end point is the composite of death, (recurrent) myocardial infarction, definite stent thrombosis, stroke, and Platelet Inhibition and Patient Outcomes (PLATO) major bleeding at 1 year. Primary safety end point is the composite of (PLATO) major and minor bleeding. Cost-effectiveness and quality of life will be assessed by calculating quality-adjusted life-years, net costs per life-year, and per quality-adjusted life-year gained. CONCLUSION: The POPular Genetics study is the first large-scale trial comparing CYP2C19 genotype-guided antiplatelet therapy to a nontailored strategy in terms of net clinical benefit, safety, and cost-effectiveness

Clopidogrel Versus Ticagrelor or Prasugrel after Primary Percutaneous Coronary Intervention According to CYP2C19 Genotype: A POPular Genetics Subanalysis

Background: Guidelines favor ticagrelor or prasugrel over clopidogrel in patients with myocardial infarction. However, the POPular Genetics trial (Patient Outcome After Primary Percutaneous Coronary Intervention [PCI]) showed that in patients with primary PCI, a CYP2C19 genotype-guided strategy was associated with a lower bleeding risk without increasing thrombotic risk, compared with routine ticagrelor/prasugrel treatment. Nevertheless, optimal P2Y12 inhibitor treatment in specific CYP2C19 genetic subgroups is still a subject of debate. Methods: A prespecified subanalysis of the POPular Genetics trial was performed, using patients in whom CYP2C19∗2, ∗3, and ∗17 genotypes was determined. Two different analyses were planned. The first assessed the effect of the CYP2C19∗17 allele in clopidogrel-treated patients. The second compared the effect of clopidogrel in noncarriers of a loss-of-function allele with ticagrelor/prasugrel-treated patients, irrespective of CYP2C19 genotype. Main outcomes were a thrombotic outcome (cardiovascular death, myocardial infarction, stent thrombosis, and stroke) and a bleeding outcome (PLATO [Platelet Inhibition and Patient Outcomes] major and minor bleeding) after 12 months. Results: A total of 2429 patients were used for analyses. In the first analysis, the CYP2C19∗17 polymorphism was not found to have a significant influence on thrombotic (adjusted hazard ratio, 0.95 [95% CI, 0.45-2.02]) or bleeding outcomes (adjusted hazard ratio, 0.74 [95% CI, 0.48-1.18]). In the second analysis, clopidogrel was associated with a lower number of bleeding events compared with ticagrelor/prasugrel (9.9% versus 11.7%, adjusted hazard ratio, 0.74 [95% CI, 0.56-0.96]), without a significant increase in thrombotic events (3.4% versus 2.5%, adjusted hazard ratio, 1.14 [95% CI, 0.68-1.90]). Conclusions: In patients with primary PCI not carrying a CYP2C19 loss-of-function allele, the use of clopidogrel compared with ticagrelor or prasugrel was associated with lower bleeding rates, without an increase in thrombotic events. No effect on clinical outcomes was found for the CYP2C19∗17 polymorphism

A genotype-guided strategy for oral P2Y12 inhibitors in primary PCI

BACKGROUND: It is unknown whether patients undergoing primary percutaneous coronary intervention (PCI) benefit from genotype-guided selection of oral P2Y 12 inhibitors. METHODS: We conducted a randomized, open-label, assessor-blinded trial in which patients undergoing primary PCI with stent implantation were assigned in a 1:1 ratio to receive either a P2Y 12 inhibitor on the basis of early CYP2C19 genetic testing (genotype-guided group) or standard treatment with either ticagrelor or prasugrel (standard-treatment group) for 12 months. In the genotype-guided group, carriers of CYP2C19*2 or CYP2C19*3 loss-of-function alleles received ticagrelor or prasugrel, and noncarriers received clopidogrel. The two primary outcomes were net adverse clinical events - defined as death from any cause, myocardial infarction, definite stent thrombosis, stroke, or major bleeding defined according to Platelet Inhibition and Patient Outcomes (PLATO) criteria - at 12 months (primary combined outcome; tested for noninferiority, with a noninferiority margin of 2 percentage points for the absolute difference) and PLATO major or minor bleeding at 12 months (primary bleeding outcome). RESULTS: For the primary analysis, 2488 patients were included: 1242 in the genotype-guided group and 1246 in the standard-treatment group. The primary combined outcome occurred in 63 patients (5.1%) in the genotype-guided group and in 73 patients (5.9%) in the standard-treatment group (absolute difference, -0.7 percentage points; 95% confidence interval [CI], -2.0 to 0.7; P<0.001 for noninferiority). The primary bleeding outcome occurred in 122 patients (9.8%) in the genotype-guided group and in 156 patients (12.5%) in the standard-treatment group (hazard ratio, 0.78; 95% CI, 0.61 to 0.98; P = 0.04). CONCLUSIONS: In patients undergoing primary PCI, a CYP2C19 genotype-guided strategy for selection of oral P2Y 12 inhibitor therapy was noninferior to standard treatment with ticagrelor or prasugrel at 12 months with respect to thrombotic events and resulted in a lower incidence of bleeding. (Funded by the Netherlands Organization for Health Research and Development; POPular Genetics ClinicalTrials.gov number, NCT01761786; Netherlands Trial Register number, NL2872.)

A genotype-guided strategy for oral P2Y12 inhibitors in primary PCI

BACKGROUND: It is unknown whether patients undergoing primary percutaneous coronary intervention (PCI) benefit from genotype-guided selection of oral P2Y 12 inhibitors. METHODS: We conducted a randomized, open-label, assessor-blinded trial in which patients undergoing primary PCI with stent implantation were assigned in a 1:1 ratio to receive either a P2Y 12 inhibitor on the basis of early CYP2C19 genetic testing (genotype-guided group) or standard treatment with either ticagrelor or prasugrel (standard-treatment group) for 12 months. In the genotype-guided group, carriers of CYP2C19*2 or CYP2C19*3 loss-of-function alleles received ticagrelor or prasugrel, and noncarriers received clopidogrel. The two primary outcomes were net adverse clinical events - defined as death from any cause, myocardial infarction, definite stent thrombosis, stroke, or major bleeding defined according to Platelet Inhibition and Patient Outcomes (PLATO) criteria - at 12 months (primary combined outcome; tested for noninferiority, with a noninferiority margin of 2 percentage points for the absolute difference) and PLATO major or minor bleeding at 12 months (primary bleeding outcome). RESULTS: For the primary analysis, 2488 patients were included: 1242 in the genotype-guided group and 1246 in the standard-treatment group. The primary combined outcome occurred in 63 patients (5.1%) in the genotype-guided group and in 73 patients (5.9%) in the standard-treatment group (absolute difference, -0.7 percentage points; 95% confidence interval [CI], -2.0 to 0.7; P<0.001 for noninferiority). The primary bleeding outcome occurred in 122 patients (9.8%) in the genotype-guided group and in 156 patients (12.5%) in the standard-treatment group (hazard ratio, 0.78; 95% CI, 0.61 to 0.98; P = 0.04). CONCLUSIONS: In patients undergoing primary PCI, a CYP2C19 genotype-guided strategy for selection of oral P2Y 12 inhibitor therapy was noninferior to standard treatment with ticagrelor or prasugrel at 12 months with respect to thrombotic events and resulted in a lower incidence of bleeding. (Funded by the Netherlands Organization for Health Research and Development; POPular Genetics ClinicalTrials.gov number, NCT01761786; Netherlands Trial Register number, NL2872.)

Clopidogrel Versus Ticagrelor or Prasugrel After Primary Percutaneous Coronary Intervention According to CYP2C19 Genotype:A POPular Genetics Subanalysis

BACKGROUND: Guidelines favor ticagrelor or prasugrel over clopidogrel in patients with myocardial infarction. However, the POPular Genetics trial (Patient Outcome After Primary Percutaneous Coronary Intervention [PCI]) showed that in patients with primary PCI, a CYP2C19 genotype-guided strategy was associated with a lower bleeding risk without increasing thrombotic risk, compared with routine ticagrelor/prasugrel treatment. Nevertheless, optimal P2Y(12) inhibitor treatment in specific CYP2C19 genetic subgroups is still a subject of debate. METHODS: A prespecified subanalysis of the POPular Genetics trial was performed, using patients in whom CYP2C19*2, *3, and *17 genotypes was determined. Two different analyses were planned. The first assessed the effect of the CYP2C19*17 allele in clopidogrel-treated patients. The second compared the effect of clopidogrel in noncarriers of a loss-of-function allele with ticagrelor/prasugrel-treated patients, irrespective of CYP2C19 genotype. Main outcomes were a thrombotic outcome (cardiovascular death, myocardial infarction, stent thrombosis, and stroke) and a bleeding outcome (PLATO [Platelet Inhibition and Patient Outcomes] major and minor bleeding) after 12 months. RESULTS: A total of 2429 patients were used for analyses. In the first analysis, the CYP2C19*17 polymorphism was not found to have a significant influence on thrombotic (adjusted hazard ratio, 0.95 [95% CI, 0.45-2.02]) or bleeding outcomes (adjusted hazard ratio, 0.74 [95% CI, 0.48-1.18]). In the second analysis, clopidogrel was associated with a lower number of bleeding events compared with ticagrelor/prasugrel (9.9% versus 11.7%, adjusted hazard ratio, 0.74 [95% CI, 0.56-0.96]), without a significant increase in thrombotic events (3.4% versus 2.5%, adjusted hazard ratio, 1.14 [95% CI, 0.68-1.90]). CONCLUSIONS: In patients with primary PCI not carrying a CYP2C19 loss-of-function allele, the use of clopidogrel compared with ticagrelor or prasugrel was associated with lower bleeding rates, without an increase in thrombotic events. No effect on clinical outcomes was found for the CYP2C19*17 polymorphism. REGISTRATION: URL: https://www.clinicaltrials.gov; Unique identifier: NCT01761786. URL: https://www.trialregister.nl/; Unique identifier: NL2872. GRAPHIC ABSTRACT: A graphic abstract is available for this article

A Genotype-Guided Strategy for Oral P2Y12 Inhibitors in Primary PCI

BACKGROUND: It is unknown whether patients undergoing primary percutaneous coronary intervention (PCI) benefit from genotype-guided selection of oral P2Y12 inhibitors. METHODS: We conducted a randomized, open-label, assessor-blinded trial in which patients undergoing primary PCI with stent implantation were assigned in a 1:1 ratio to receive either a P2Y12 inhibitor on the basis of early CYP2C19 genetic testing (genotype-guided group) or standard treatment with either ticagrelor or prasugrel (standard-treatment group) for 12 months. In the genotype-guided group, carriers of CYP2C19*2 or CYP2C19*3 loss-of-function alleles received ticagrelor or prasugrel, and noncarriers received clopidogrel. The two primary outcomes were net adverse clinical events - defined as death from any cause, myocardial infarction, definite stent thrombosis, stroke, or major bleeding defined according to Platelet Inhibition and Patient Outcomes (PLATO) criteria - at 12 months (primary combined outcome; tested for noninferiority, with a noninferiority margin of 2 percentage points for the absolute difference) and PLATO major or minor bleeding at 12 months (primary bleeding outcome). RESULTS: For the primary analysis, 2488 patients were included: 1242 in the genotype-guided group and 1246 in the standard-treatment group. The primary combined outcome occurred in 63 patients (5.1%) in the genotype-guided group and in 73 patients (5.9%) in the standard-treatment group (absolute difference, -0.7 percentage points; 95% confidence interval [CI], -2.0 to 0.7; P<0.001 for noninferiority). The primary bleeding outcome occurred in 122 patients (9.8%) in the genotype-guided group and in 156 patients (12.5%) in the standard-treatment group (hazard ratio, 0.78; 95% CI, 0.61 to 0.98; P = 0.04). CONCLUSIONS: In patients undergoing primary PCI, a CYP2C19 genotype-guided strategy for selection of oral P2Y12 inhibitor therapy was noninferior to standard treatment with ticagrelor or prasugrel at 12 months with respect to thrombotic events and resulted in a lower incidence of bleeding. (Funded by the Netherlands Organization for Health Research and Development; POPular Genetics ClinicalTrials.gov number, NCT01761786; Netherlands Trial Register number, NL2872.)