Differential effects of tyrosine kinase inhibitors in haemostasis, thrombosis and inflammation
Creators: name: Hamadi, Abdullah
Publisher: name: RMIT University
Year: 2024
Subjects: classificationCode: 320102
subject: Haematology

description: The detection of the Bcr-Abl gene in chronic myeloid leukaemia (CML) has resulted in the development of novel tyrosine kinase inhibitors (TKIs), such as imatinib that particularly interfere with the ATP binding pocket of the Abl kinase domain of the Bcr-Abl protein. Imatinib is currently used as a frontline therapy, with impressive outcomes at producing long-term clinical remission among many CML patients; however, resistance to imatinib has been reported in patients due to the development of Bcr-Abl mutations and/or intolerance to the drug. Potent second generation TKIs, namely nilotinib and dasatinib, have since been developed and approved to address this therapeutic challenge. With their prompt and noticeable deep molecular and haematological remission properties, dasatinib and nilotinib have provided a significant effect and efficiency against leukaemic cells. However, due to the side effects and challenges linked to dasatinib, imatinib, and nilotinib, ponatinib which is a new third generation TKI inhibitor multi-kinase drug has been developed to be effective against leukemic cells containing the Bcr-Abl resistance mutation T315I. Nevertheless, ponatinib can inhibit T315I Bcr-Abl mutant enzymes selectively especially the ones which are not sensitive to new Bcr-Abl inhibitors obtainable at clinics.<br><br>The management of malignancy in a significant proportion of patients and their survival is improved using these later generation drugs, therefore, recent studies have concentrated on their toxicity. For instance, in the case of ponatinib and nilotinib, clinical studies have revealed excessive and unnecessarily severe vascular problems, such as peripheral arterial occlusive disease (PAOD) and arterial occlusive events compared with other TKIs. Consequently, this had led to an increased desire to limit the pathophysiology of cardiovascular risk factors.<br><br>Cardiovascular disease is a major clinical issue and a leading cause of illness, disability and mortality in the world, specifically in industrialised countries. Platelets are essential in normal haemostasis as they prevent blood loss following trauma by blood clot formation and they sustain vascular integrity. They also play a crucial role in the pathophysiological processes of atherosclerotic plaque and arterial thrombotic disease by contributing to vaso-occlusive thrombotic mechanisms that generate ischaemic traumatic damage in cardiovascular and peripheral blood vessel disease. Platelets¿ attachment under some extreme conditions of excessive flow shear forces in stenotic blood arteries enhances the reaction of platelets leading to increased in vivo arterial coagulation.<br><br>In the context of vasculature, the pro-atherothrombotic role of platelets is presently well defined and involves pro-incendiary viscid particles in the interface between endothelium and platelets at sites of ruptured atherosclerosis plaques. This promotes the recruitment and adhesion of leukocytes, thereby leading to enhancement of atherosclerotic plaque formation and development of arterial thrombosis. The anti-leukaemic therapies, such as TKIs, are commonly associated with modifications of platelets and endothelial function that lead to the production of pathological thrombi.<br><br>The primary purpose of this study was to determine the effect of ponatinib, nilotinib, dasatinib and imatinib on the function of platelets and thrombus growth in mouse and human arteries by in vitro, ex vivo and in vivo methods. The overarching goal was to provide a comprehensive analysis that would improve the understanding of potential mechanisms by which the TKI, ponatinib, potentiates a prothrombotic state.<br><br>In vitro experiments demonstrated that dasatinib and imatinib, but not ponatinib or nilotinib, inhibited ADP-, CRP-, and collagen-induced platelet aggregation. Ponatinib also potentiated PAR-1-mediated alpha granule release, whilst imatinib and dasatinib showed inhibitory effects on platelet alpha granule exocytosis following agonist stimulation.<br><br>In this study, we demonstrated using intravital microscopy of vascular injury of mesenteric arterioles and carotid arteries induced by ferric chloride (FeCl3) that there was a significant increase in in vivo thrombus formation over time in mice treated with ponatinib (3 mg/kg), nilotinib (25 mg/kg), but not with imatinib (25 mg/kg) or dasatinib (5 mg/kg). In addition, the effect of ponatinib was independent of platelet glycoprotein surface expression. Ponatinib potentiated alpha granule exocytosis in humans and mice. <br><br>The data presented in this thesis confirmed the prothrombotic effects of ponatinib and nilotinib in humans where it was shown that in whole blood from drug-treated CML patients there was increased ex vivo platelet adhesion under flow conditions and increased plasma levels of soluble P-selectin (sP-selectin) and pro-inflammatory cytokines.<br><br>The results from this study also demonstrated that ponatinib and nilotinib TKIs have a prothrombotic effect that can be reversed by pretreatment with the L-type calcium channel blocker, diltiazem and the COX-2 inhibitor, diclofenac, and to a lesser extent by the eNOS synthase inhibitor, L-NNA. However, the study suggested that nilotinib or ponatinib-treated CML patients who develop vascular complications of coronary artery vasospasm or cerebrovascular accident (CVA) could potentially be treated with L-type calcium channel blockers to reduce arterial occlusive events. Further clinical trials are indicated to examine the efficacy and safety of using calcium channel blockers in the clinical setting of ponatinib and nilotinib-treated CML patients.