Avatrombopag, also known as AKR-501, YM477, AS 1670542 or E5501, is a novel orally-active thrombopoietin (TPO) receptor agonist. AKR-501 specifically targeted the TPO receptor and stimulated megakaryocytopoiesis throughout the development and maturation of megakaryocytes just as rhTPO did. AKR-501 is an orally-active TPO receptor agonist that may be useful in the treatment of patients with thrombocytopenia.