Thrombopoietin is a major cytokine involved in the regulation of megakaryopoiesis and platelet formation and is the endogenous ligand for thrombopoietin receptors. Eltrombopag interacts with the transmembrane domain of human thrombopoietin receptors and initiates a signaling cascade similar but not identical to that triggered by endogenous thrombopoietin, inducing the proliferation and differentiation of megakaryocytes from progenitor cells in the bone marrow.