Genetics of Response to Antiplatelet Therapy

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.

Genotype-guided dual antiplatelet therapy in cerebrovascular disease: assessing the risk and benefits for ethnic populations

INTRODUCTION

Cerebrovascular disease is a leading cause of morbidity and mortality in the world and antiplatelet therapy is a main pharmacologic means of secondary prevention. Clinical information has accumulated about benefit of dual antiplatelet therapy in certain clinical scenarios, genetic causes of antiplatelet resistance and its effect on clinical outcomes, and ethnic and geographic distributions of genetic polymorphisms.

AREAS COVERED

This review covers literature related to the pharmacogenomics of antiplatelet agents with a focus on ethnic variability, antiplatelet resistance, and dual antiplatelet therapy in cerebrovascular disease.

EXPERT OPINION

Selecting patients for dual antiplatelet therapy and specific agents require consideration of multiple factors. Ethnic factors should be considered in certain circumstances, but additional research is needed to determine the generalizability of the findings.

P2Y12-inhibitor monotherapy after coronary stenting: are all P2Y12-inhibitors equal?

INTRODUCTION

P2Y₁₂-inhibitor monotherapy following 1-3 months of dual antiplatelet therapy (DAPT) reduces (major) bleeding without an apparent increase in ischemic events and has therefore emerged as an alternative to 6-12 months of DAPT following percutaneous coronary intervention (PCI). However, there are important differences between the available P2Y₁₂-inhibitors (clopidogrel, prasugrel, and ticagrelor) as agents of choice for P2Y₁₂-inhibitor monotherapy.

AREAS COVERED

This review critically appraises the evidence for P2Y₁₂-inhibitor monotherapy after PCI using either clopidogrel, prasugrel, or ticagrelor. Furthermore, we discuss ongoing trials and future directions for research.

EXPERT OPINION

P2Y₁₂-inhibitor monotherapy following 1-3 months of DAPT is an alternative to 6-12 months of DAPT following PCI. Ticagrelor may be considered the current preferred option due to its reliable effect on platelet reactivity and its predominant use in clinical trials. Prasugrel could serve as a useful substitute for those not tolerating ticagrelor, but more research into prasugrel monotherapy is warranted. Alternatively, clopidogrel can be used, although there are concerns of high platelet reactivity, especially when genotyping and/or platelet function testing are not used. Future research will need to address the minimal duration of DAPT before switching to P2Y₁₂-inhibitor monotherapy and what the optimal antithrombotic therapy beyond 12 months is.

P2Y12 blocker monotherapy after percutaneous coronary intervention

For secondary prevention of coronary artery disease (CAD) antiplatelet therapy is essential. For patients undergoing a percutaneous coronary intervention (PCI) temporary dual antiplatelet platelet therapy (DAPT: aspirin combined with a P2Y12 blocker) is mandatory, but leads to more bleeding than single antiplatelet therapy with aspirin. Therefore, to reduce bleeding after a PCI the duration of DAPT is usually kept as short as clinically acceptable; thereafter aspirin monotherapy is administered. Another option to reduce bleeding is to discontinue aspirin at the time of DAPT cessation and thereafter to administer P2Y12 blocker monotherapy. To date, five randomised trials have been published comparing DAPT with P2Y12 blocker monotherapy in 32,181 stented patients. Also two meta-analyses addressing this novel therapy have been presented. P2Y12 blocker monotherapy showed a 50-60% reduction in major bleeding when compared to DAPT without a significant increase in ischaemic outcomes, including stent thrombosis. This survey reviews the findings in the current literature concerning P2Y12 blocker monotherapy after PCI.

Antithrombotics: From Aspirin to DOACs in Coronary Artery Disease and Atrial Fibrillation (Part 3/5)

For secondary prevention of coronary artery disease (CAD), oral antiplatelet therapy is essential. In case of coronary intervention, temporary dual antiplatelet therapy is mandatory as well. Recently, low-dose oral anticoagulation has entered the CAD arena. Atrial fibrillation (AF) is often seen in CAD and vice versa. In most patients stroke prevention in AF consists of oral anticoagulation. In many cases of CAD in patients with AF, anticoagulation has to be combined with antiplatelet agents (so called, dual pathway antithrombotic therapy). Excess bleeding in these conditions is a rapidly rising problem. This review addresses the antithrombotic options in CAD alone, in AF alone, and in their combination, when either an invasive or a noninvasive approach has been chosen.

Effect of P2Y12 inhibitors on inflammation and immunity

Platelet P2Y12 inhibitors form a major part of the treatment strategy for patients with acute coronary syndromes (ACS) due to the importance of the platelet P2Y12 receptor in mediating the pathophysiology of arterial thrombosis. It has been increasingly recognised that platelets also have a critical role in inflammation and immune responses. P2Y12 inhibitors reduce platelet release of pro-inflammatory α-granule contents and the formation of pro-inflammatory platelet-leukocyte aggregates. These are important mediators of inflammation in a variety of different contexts. Clinical evidence shows that P2Y12 inhibition by clopidogrel is associated with a reduction in platelet-related mediators of inflammation, such as soluble P-selectin and CD40L, following atherothrombosis. Clopidogrel in addition to aspirin, compared to aspirin alone, also reduces markers of systemic inflammation such as tumour necrosis factor (TNF) α and C-reactive protein (CRP) following ACS. The more potent thienopyridine P2Y12 inhibitor, prasugrel, has been shown to decrease platelet P-selectin expression and platelet-leukocyte aggregate formation compared to clopidogrel. The PLATO study suggested that the novel P2Y12 inhibitor ticagrelor might improve clinical outcomes from pulmonary infections and sepsis compared to clopidogrel in patients with ACS. Ticagrelor is a more potent P2Y12 inhibitor than clopidogrel and also inhibits cellular adenosine uptake via equilibrative nucleoside transporter (ENT) 1, whereas clopidogrel does not. Further examination of the involvement of these mechanisms in inflammation and immunity is therefore warranted.

Dual Antiplatelet Therapy of Clopidogrel and Aspirin in Secondary Prevention of Ischemic Stroke: Evidence and Indications

Nowadays the dual antiplatelet therapy (DAPT) becomes more widely used in patients with ischemic stroke. Nevertheless, controversies exist for indications of DAPT. In view of evidence-based medicine analysis, patients with high-risk transient ischemic attack and minor stroke, severe symptomatic intracranial artery stenosis, symptomatic intracranial and extracranial artery stenosis causing artery-to-artery embolism, ischemic stroke attributed to aortic arch plaques, high-risk atrial fibrillation not suitable for oral anticoagulants, intracranial and extracranial stent implantation, and ischemic stroke with acute coronary syndrome may gain great benefit from DAPT of clopidogrel and aspirin. In clinical practice, individualized antiplatelet therapy strategies should be taken by weighing risks of ischemia and hemorrhage.