Potent P2Y12 receptor inhibitors in patients with acute coronary syndrome

Coadministration of ticagrelor and ritonavir: Toward prospective dose adjustment to maintain an optimal platelet inhibition using the PBPK approach

Ticagrelor is a potent antiplatelet drug metabolized by cytochrome (CYP)3A. It is contraindicated in patients with human immunodeficiency virus (HIV) because of the expected CYP3A inhibition by most protease inhibitors, such as ritonavir and an increased bleeding risk. In this study, a physiologically based pharmacokinetic (PBPK) model was created for ticagrelor and its active metabolite (AM). Based on the simulated interaction between ticagrelor 180 mg and ritonavir 100 mg, a lower dose of ticagrelor was calculated to obtain, when coadministered with ritonavir, the same pharmacokinetic (PK) and platelet inhibition as ticagrelor administered alone. A clinical study was thereafter conducted in healthy volunteers. Observed PK profiles of ticagrelor and its AM were successfully predicted with the model. Platelet inhibition was nearly complete in both sessions despite administration of a fourfold lower dose of ticagrelor in the second session. This PBPK model could be prospectively used to broaden the usage of ticagrelor in patients with ritonavir-treated HIV regardless of the CYP3A inhibition.

Antiplatelet Therapy Considerations in Ischemic Cardiogenic Shock

Dual antiplatelet therapy with aspirin and a P2Y12 receptor antagonist remains a mainstay in the prevention of ischemic events following coronary stent placement. Significant controversy exists regarding the optimal management of high platelet reactivity despite antiplatelet therapy; however this finding has been consistently associated with poor clinical outcomes including greater risk of stent thrombosis and myocardial infarction. Variability in antiplatelet effects of clopidogrel and prasugrel has been linked to genetic polymorphisms and potential drug–drug interactions. Both of these factors have significant influence on the cytochrome P-450 enzyme system activity of the liver responsible for their biotransformation to the active form of both drugs. Very little has been publicized regarding differences in antiplatelet effects which may be associated with conditions in which the functional capacity of the liver may be temporarily compromised. Patients who present with cardiogenic shock due to acute coronary syndromes have evidence of multiorgan dysfunction including liver dysfunction that may affect the activity of these drugs. This review aims to explore existing evidence and propose additional considerations to the selection of antiplatelet therapy in patients with cardiogenic shock who receive catheter-based revascularization and stent placement.

SAR216471, an alternative to the use of currently available P2Y₁₂ receptor inhibitors?

P2Y12 antagonism is a key therapeutic strategy in the management and prevention of arterial thrombosis. The objective of this study was to characterize the pharmacodynamic (PD) and pharmacokinetic (PK) properties of SAR216471, a novel P2Y12 receptor antagonist. SAR216471 blocks the binding of 2MeSADP to P2Y12 receptors in vitro (IC50=17 nM). This inhibition was shown to be reversible. It potently antagonized ADP-induced platelet aggregation in human and rat platelet-rich plasma (IC50=108 and 62 nM, respectively). It also inhibited platelet aggregation when blood was exposed to collagen or thromboxane A2. Its high selectivity was demonstrated against a large panel of receptors, enzymes, and ion channels. Despite its moderate bioavailability in rats, oral administration of SAR216471 resulted in a fast, potent, and sustained inhibition of platelet aggregation where the extent and duration of platelet inhibition were directly proportional to its circulating plasma levels. Pre-clinical study of SAR216471 in a rat shunt thrombosis model demonstrated a dose-dependent antithrombotic activity after oral administration (ED50=6.7 mg/kg). By comparison, ED50 values for clopidogrel, prasugrel and ticagrelor were 6.3, 0.35 and 2.6 mg/kg, respectively. Finally, the anti-hemostatic effect of SAR216471 and its competitors was investigated in a rat tail bleeding model, revealing a favorable safety profile of SAR216471. Together, these findings have established a reliable antiplatelet profile of SAR216471, and support its potential use in clinical practice as an alternative to currently available P2Y12 receptor antagonists.

Direct oral anticoagulants and antiplatelet agents. Clinical relevance and options for laboratory testing

Oral anticoagulants and platelet receptor blockers are widely used in clinical practice with the aim of reducing the risk of thrombotic complications in patients with cardiovascular diseases. Their regular intake and adequate antithrombotic action is vital and this is way numerous assays have been developed for laboratory testing and monitoring of these agents. Available assays can be stratified into pharmacokinetic and pharmacodynamic assays. Such assays are increasingly used in clinical routine and their daily use is triggered by the advent of the novel direct oral anticoagulants (DOACs) as an alternative for vitamin K antagonist (VKA) treatment, which are dabigatran, rivaroxaban and apixaban, and by the advent of prasugrel or ticagrelor as an alternative for clopidogrel with regard to platelet P2Y12 receptor inhibition. In this review the most important and most commonly used laboratory assays are summarized as well as their clinical implications with the focus on DOACs as an alternative for VKAs and the different P2Y12 receptor blockers for antiplatelet treatment.