ticagrelor and Syndrome

Platelets possess three P2 receptors for adenine nucleotides: P2Y1 and P2Y12, which interact with ADP, and P2X1, which interacts with ATP. The interaction of adenine nucleotides with their platelet receptors plays an important role in thrombogenesis. The thienopyridine ticlopidine, an antagonist of the platelet P2Y12 ADP receptor, reduces the incidence of vascular events in patients at risk, but it also has some important drawbacks: a relatively high incidence of toxic effects; delayed onset of action; high inter-individual variability in response. Another thienopyridine, clopidogrel, has superseded ticlopidine, because it is an efficacious antithrombotic drug and is less toxic than ticlopidine. However, the high inter-patient variability in response still remains an important issue. These drawbacks justify the continuing search for agents that can further improve the clinical outcome of patients with atherosclerosis through greater efficacy and/or safety. A new thienopyridyl compound prasugrel, which is characterized by higher potency and faster onset of action compared with clopidogrel, is currently under clinical evaluation. Two direct and reversible P2Y12 antagonists, cangrelor and AZD6140, have very rapid onset and reversal of platelet inhibition, which make them attractive alternatives to thienopyridines, especially when rapid inhibition of platelet aggregation or its quick reversal are required. Along with new P2Y12 antagonists, inhibitors of the other platelet receptor for ADP, P2Y1, and of the receptor for ATP, P2X1, are under development and may prove to be effective antithrombotic agents.

Topics: Adenosine; Adenosine Monophosphate; Angina, Unstable; Animals; Blood Platelets; Clopidogrel; Coronary Disease; Coronary Thrombosis; Drug Interactions; Fibrinolytic Agents; Humans; Myocardial Infarction; Piperazines; Platelet Aggregation; Platelet Aggregation Inhibitors; Prasugrel Hydrochloride; Purinergic P2 Receptor Antagonists; Randomized Controlled Trials as Topic; Receptors, Purinergic P2; Receptors, Purinergic P2X; Syndrome; Thiophenes; Ticagrelor; Ticlopidine

There may be a universal mechanism explaining dyspnea after ticagrelor and elinogrel, namely, transfusion-related acute lung injury (TRALI). Indeed, recent clinical trials with ticagrelor (DISPERSE, DISPERSE-II, and PLATO), and elinogrel (INNOVATE PCI) revealed double-digit rates of dyspnea after novel reversible antiplatelet agents. In contrast, dyspnea is not associated with conventional non-reversible agents such as aspirin, or thienopyridines (ticlopidine, clopidogrel, or prasugrel) suggesting distinct mechanism of shortness of breath after ticagrelor and elinogrel. The adenosine hypothesis has been offered to explain such adverse association. However, despite obvious similarity between ticagrelor and adenosine molecules, the chemical structure of elinogrel is entirely different. In fact, ticagrelor is a cyclopentyl-triazolo-pyrimidine, while elinogrel is a quinazolinedione. Since both agents cause dyspnea, the adenosine hypothesis is no longer valid. In contrast, the reversible nature of platelet inhibition attributable to both ticagrelor and elinogrel causing premature cell ageing, apoptosis, impaired turnover due to sequestration of overloaded, exhausted platelets in the pulmonary circulation are among potential autoimmune mechanism(s) resulting in the development of a TRALI-like reaction, and frequent dyspnea. Despite expected benefit for better bleeding control, further development of reversible antithrombins is severely limited due to the existence of a potentially universal serious adverse event, such as TRALI-syndrome with dyspnea as a predominant clinical manifestation. Since TRALI is an established number one contributor to mortality after blood transfusions, ticagrelor death "benefit" in PLATO is challenged further.

Topics: Acute Lung Injury; Adenosine; Blood Platelets; Dyspnea; Humans; Models, Biological; Platelet Aggregation Inhibitors; Quinazolinones; Sulfonamides; Syndrome; Ticagrelor; Transfusion Reaction