The role of clinical parameters and of CYP2C19 G681 and CYP4F2 G1347A polymorphisms on platelet reactivity during dual antiplatelet therapy

Pharmacogenetic considerations in therapy with novel antiplatelet and anticoagulant agents

Antiplatelets and anticoagulants are extensively used in cardiovascular medicine for the prevention and treatment of thrombosis in the venous and arterial circulations. Wide inter-individual variability has been observed in response to antiplatelets and anticoagulants, which triggered researchers to investigate the genetic basis of this variability. Data from extensive pharmacogenetic studies pointed to strong evidence of association between polymorphisms in candidate genes and the pharmacokinetics and pharmacodynamic action and clinical response of the antiplatelets clopidogrel and the anticoagulant warfarin. In this review, we conducted an extensive search on Medline for the time period of 2009-2023. We also searched the PharmGKB website for levels of evidence of variant-drug combinations and for drug labels and clinical guidelines. We focus on the pharmacogenetics of novel antiplatelets and anticoagulants while excluding acetylsalicylic acid, warfarin and heparins, and discuss the current knowledge with emphasis on the level of evidence.

Advances and Perspectives in methods for identifying high platelet reactivity

Antiplatelet therapy is the foundational treatment for the prevention and treatment of coronary and cerebrovascular ischemic events in patients with coronary heart disease, ischemic stroke, and transient ischemic attack (TIA). However, with more and more studies reporting an increased risk of thrombosis in some patients due to poor response to therapeutic agents, the selection of appropriate P2Y12 inhibitors has become a major challenge that needs to be addressed urgently. Currently, commonly used oral P2Y12 inhibitors include clopidogrel, ticagrelor, and prasugrel. Assessing patients' risk factors before the development of treatment regimens by effectively predicting the risk of high platelet reactivity with specific P2Y12 inhibitors in advance to avert the occurrence of major adverse cardiovascular and cerebrovascular events (MACCE) is the key point to the problem. Up to now, methods available for predicting platelet reactivity include genetic testing, platelet function testing, and risk scores. This review provides a summarization of the existent available identification methods and analyzes the advantages and drawbacks of different methods in specific clinical settings, intending to guide the rational clinical application of P2Y12 receptor inhibitors.

Individualized medication based on pharmacogenomics and treatment progress in children with IgAV nephritis

Immunoglobulin A vasculitis (IgAV) nephritis, also known as Henoch-Schönlein purpura nephritis (HSPN), is a condition in which small blood vessel inflammation and perivascular IgA deposition in the kidney caused by neutrophil activation, which more often leads to chronic kidney disease and accounts for 1%–2% of children with end-stage renal disease (ESRD). The treatment principles recommended by the current management guidelines include general drug treatment, support measures and prevention of sequelae, among which the therapeutic drugs include corticosteroids, immunosuppressive agents and angiotensin system inhibitors. However, the concentration range of immunosuppressive therapy is narrow and the individualized difference is large, and the use of corticosteroids does not seem to improve the persistent nephropathy and prognosis of children with IgAV. Therefore, individualized maintenance treatment of the disease and stable renal prognosis are still difficult problems. Genetic information helps to predict drug response in advance. It has been proved that most gene polymorphisms of cytochrome oxidase P450 and drug transporter can affect drug efficacy and adverse reactions (ADR). Drug therapy based on genetics and pharmacogenomics is beneficial to providing safer and more effective treatment for children. Based on the pathogenesis of IgAV, this paper summarizes the current therapeutic drugs, explores potential therapeutic drugs, and focuses on the therapeutic significance of corticosteroids and immunosuppressants in children with IgAV nephritis at the level of pharmacogenomics. In addition, the individualized application of corticosteroids and immunosuppressants in children with different genotypes was analyzed, in order to provide a more comprehensive reference for the individualized treatment of IgAV nephritis in children.

Blood direct PCR: impact of CYP2C19 and CYP4F2 variants for bleeding prediction in ST-elevation myocardial infarction patients with ticagrelor

Aims: The goals of this study were to develop a new technique that could pave the way for a quicker determination of CYP4F2 rs3093135 and CYP2C19 rs4244285 variants directly from a patient's blood and to attempt to apply this technique in clinical practice. Patients & methods: The study included 144 consecutive patients admitted with ST elevation myocardial infarction. A blood-direct PCR and real-time PCR were used to detect variants of interest. Results & conclusion: Patients with bleeding events had the CYP2C19 GG (*1*1) variant more frequently than patients without bleeding events. The CYP4F2 TT variant was more frequently detected in patients with bleeding events 3 months after hospitalization.

The impact of CYP2C19 and CYP4F2 variants and clinical factors on treatment outcomes during antiplatelet therapy

Aim: The aim of this study was to determine the impact of genetic and nongenetic factors on treatment outcomes in patients receiving dual antiplatelet therapy after percutaneous coronary intervention and stent implantation. Materials & methods: Patients (n = 628) used clopidogrel or ticagrelor for at least 1 week before platelet aggregation test. Results: Multivariate binary regression analysis demonstrated that aspirin use and CYP4F2 T allele significantly increased odds for bleeding in clopidogrel users (OR: 2.488, 95% CI: 1.452-4.265; p = 0.001 and OR: 1.573, 95% CI: 1.066-2.320; respectively; p = 0.022). CYP4F2 T allele significantly increased odds for bleeding in ticagrelor users (OR: 8.270, 95% CI: 3.917-17.462; p < 0.001). Conclusion: Aspirin use and CYP4F2 T allele were significantly associated with bleeding during dual antiplatelet therapy.

The impact of CYP2C19*2, CYP4F2*3, and clinical factors on platelet aggregation, CYP4F2 enzyme activity, and 20-hydroxyeicosatetraenoic acid concentration in patients treated with dual antiplatelet therapy

: The aim of the current study was to evaluate the impact of CYP2C192 (rs4244285), CYP4F23 (rs2108622), and nongenetic factors on platelet aggregation and to investigate the mechanism of CYP4F2's effect on platelet aggregation in the patients treated with dual antiplatelet therapy. A total of 146 patients were included in this study. Ticagrelor or clopidogrel were administered in a loading dose of 180 mg and 600 mg, respectively, in combination with aspirin (300 mg). Blood samples for analysis were taken the next morning after antiplatelet therapy induction. Clopidogrel users with the CYP2C1912 variant had higher platelet aggregation values (median 43, range 30-54%) compared with 11 wild-type carriers (median 33, range 15-77%; P = 0.009). Carriers of the CYP4F213 variant had higher platelet aggregation values than carriers of the 33 variant (median 34, range 8-70% vs. median 24.5, range 10-47%, P = 0.016, respectively). Higher CYP4F2 concentrations were detected in clopidogrel users than in ticagrelor users (median 3.6, range 1.6-22.0 ng/ml vs. median 2.3, range 1.6-27.2 ng/ml, P = 0.056, respectively) and in carriers of the CYP4F213 variant compared with carriers of the 11 variant (median 4.3, range 1.6-27.2 ng/ml vs. median 2.4, range 1.6-22.0 ng/ml, P = 0.009, respectively). No correlation between plasma 20-hydroxyeicosatetraenoic acid and CYP4F2 enzyme concentrations were detected (r = -0.045, P = 0.587). Our results proved that CYP2C192 might significantly affect antiplatelet function of clopidogrel. Plasma CYP4F2 concentrations were significantly lower in ticagrelor users than in clopidogrel users.

A novel ultrasonic method for evaluation of blood clotting parameters

PURPOSE

For long time, blood clot retraction was measured only by thromboelastographic or platelet contractile force measurement techniques. The purpose of the present study was development of a novel ultrasonic method based on simultaneous monitoring of variations in the ultrasound velocity and the frequency spectrum of the signal propagating in clotting blood and its application for automatic evaluation of blood clotting parameters.

METHODS

Simultaneous measurement of ultrasound velocity and variations in the frequency spectrum of wideband ultrasonic signals in clotting blood samples was performed. All measurements were performed in pulse-echo mode. Standard clinical data were obtained using routine clinical laboratory methods.

RESULTS

The amplitudes of ultrasonic signals during native blood coagulation varied up to ten times for different frequencies. The measurement results of the start and duration of blood clot retraction differed between patient samples: different components of the blood coagulation system had significant impact on the blood clot retraction process.

CONCLUSIONS

Our results showed that during blood clotting, the ultrasound velocity and variations in frequency spectrum should be used simultaneously to determine the beginning and duration of blood clot retraction. Our results also showed that blood clot retraction is controlled by the activity of factor XIII.

The impact of clinical and genetic factors on ticagrelor and clopidogrel antiplatelet therapy

Aim: To determine clinically significant factors which may alter the effect of dual antiplatelet therapy with aspirin and ticagrelor or clopidogrel in patients who had undergone percutaneous coronary intervention and stent implantation. Materials & methods: The study included 378 patients. All the patients had undergone percutaneous coronary intervention and stent implantation. Platelet aggregation and genotyping for CYP2C19 *2 (rs4244285) and CYP4F2 (rs2108622, rs1558139, rs3093135 and rs2074902) was performed. Results: Significantly lower platelet aggregation values (%agr) were detected in ticagrelor users who carried CYP4F2 rs3093135 TT variant (14.67 ± 5.07%agr) versus AA (22.88 ± 6.30%agr), p = 0.0004, or AT (20.56 ± 6.51%agr), p = 0.0126. Conclusion: Results of the current study showed that CYP4F2 rs3093135 TT variant carriers had a higher antiplatelet effect of ticagrelor, and more frequently had nonprocedural bleeding during ticagrelor therapy, as compared with AA and AT variant carriers.

Influence of Cyp2c19*2 Gene Variant on Therapeutic Response During Clopidogrel Treatment in Patients with Carotid Artery Stenosis

BACKGROUND

Despite the proven clinical effect of oral antiplatelet drugs, a considerable number of patients do not have an adequate response to clopidogrel. The aim of our study was to determine the influence of CYP2C19*2 loss-of-function variant allele on clopidogrel responsiveness in patients with carotid artery stenosis.

METHODS

One hundred and twelve patients with carotid artery stenosis undergoing endarterectomy were included in this one-year prospective study. All of them received clopidogrel (75 mg daily) for at least 30 days after the intervention. They were followed from the moment of hospital admission. CYP2C19*2 genotyping was performed by TaqMan Assay. The influence of CYP2C19*2 variant allele on clopidogrel platelet reactivity was determined using multiple-electrode aggregometry (MEA).

RESULTS

Genotyping results showed that 82 (73.2%) patients were homozygous for wild type, 29 (25.9%) were heterozygous for the CYP2C19*2 allele and 1 (0.9%) was CYP2C19*2 homozygous. After 24 hours, among those with the wild type 29.3% were clopidogrel responders, and in those with the CYP2C19*2 alleles 10%. In the wild type group, 74.4% were clopidogrel responders after 7 days of taking the drug; 82.9% after 30 days of clopidogrel introduction, respectively. In patients with the CYP2C19*2 alleles the number of responders increased up to 46.7% after 7 days; 53.3% after 30 days of taking the drug, respectively. The risk for being a low-responder is higher for the patients heterozygous for the CYP2C19*2 allele vs. wild-type (OR 4.250, 95% CI 1.695-10.658, P<0.01).

CONCLUSIONS

The CYP2C19*2 loss-of-function variant allele has significant influence on clopidogrel response in patients with carotid artery stenosis undergoing endarterectomy.

Effect of clinical factors and gene polymorphism of CYP2C19*2, *17 and CYP4F2*3 on early stent thrombosis

Aim: To determine the main clinical and genetic factors having impact on early coronary stent thrombosis. Materials & methods: Genotyping of CYP2C19*2, *17 and CYP4F2*3 in patients with (n = 31) and without stent thrombosis (n = 456) was performed. Clinical and genetic data were analyzed by binary logistic regression. Results: Smoking (OR: 0.317; 95% CI: 0.131–0.767), high-density lipoprotein level in mmol/l (OR: 0.142; 95% CI: 0.040–0.506), CYP2C19*2*2 versus *1*1 and *1*2 genotype (OR: 11.625; 95% CI: 3.498–38.633), CYP4F2 AA versus GA and GG genotype (OR: 3.532; 95% CI: 1.153–10.822) were associated with early stent thrombosis. Conclusion: For the first time we have identified a clinically important polymorphism (CYP4F2 G1347A) that was independently associated with early stent thrombosis.

Original submitted 18 August 2014; Revision submitted 10 November 2014

Performance of exome sequencing for pharmacogenomics

AIM

We present the potential false-negative rate of exome sequencing for the detection of pharmacogenomic variants.

MATERIALS & METHODS

Depth of coverage of 1928 pharmacogenomically relevant variant positions was ascertained from 62 exome-sequenced samples.

RESULTS

Approximately 14% of the 1928 variant locations examined had inadequate depth of coverage (<20x). The variants with inadequate coverage were predominantly located outside of protein-coding portions and included some clinically relevant variant positions, such as the warfarin VKORC1 variant.

CONCLUSION

While the use of exome sequencing is becoming more prevalent in fundamental research, clinical trials and clinical use; there is a possibility of false-negative results. The possible quality issues such as false-negative rate should be considered with the use of exome sequencing.