Study on the of Anagrelide on Platelet Factor 4 and Vascular Endothelial Growth Factor Levels in Patients with Essential Thrombocythemia

Essential Thrombocythemia (ET) is a myeloproliferative neoplasm characterized by high platelet count and platelet activation linked to angiogenesis. It is reported that vascular endothelial growth factor (VEGF) promotes platelet activation and that activated platelets release VEGF. Anagrelide (ANA) represents a emerging drug which decresaes platelets and inhibits platelet activation. Therefore, were studied platelet count, platelet factor 4 (PF4) levels, as indicator of platelet activation, and corrected platelet VEGF (VEGFPLT), as indicator of angiogenesis-related platelet activation, in ET patients treated either with hydroxyurea (HU) and interferon-a (IFN-a) or ANA in combination with antiaggregants. Before treatment all patients had high platelets and higher PF4 and VEGFPLT than controls. After treatment all patients had decreased platelets whereas PF4 and VEGFPLT were elevated in the HU and IFN-a group compared with controls and normal in the ANA group. There was no correlation between PF4 and platelets whereas a positive correlation there was between PF4 and VEGFPLT. These results, if confirmed in larger studies, might indicate that ANA has anti-platelet and anti-angiogenic properties.