Immune thrombocytopenia (ITP) is an autoimmune bleeding disorder in which the immune system destroys platelets and decreases platelet production, which results in low numbers of platelets within the blood. The platelet counts do not correlate with bleeding severity, and it is challenging to predict therapeutic responses, which may result in overtreatment with increased side effects and bleeding in non-responding and treatment-resistant patients. Thus, there is an unmet clinical need to predict the bleeding risk and its therapeutic management in ITP patients. In this project, we focus on the role of extracellular vesicles (EVs) from activated platelets, which may promote coagulation or inflammation. Such EVs are present in blood from ITP patients but they are poorly characterized with regards to presence, composition and functionality. We will systematically characterize and functionally analyze the role of platelet EVs in active chronic ITP and in therapy (non)-responders, using clinical samples of ITP patients and a clinically-relevant ITP animal model. This may pave the way for personalized approaches regarding assessment of bleeding risk and therapeutic management in ITP patients.