MPL and autoimmune thrombocytopenic purpura: Thrombopoietin (TPO) and its receptor c‐Mpl play critical roles in hematopoietic stem cell renewal, megakaryocyte (MK) differentiation, and platelet formation.[7] As thrombopoietic agents, rhTPO and TPO‐RAs have been used as widespread therapies for ITP.