MPL and autoimmune thrombocytopenic purpura: Thrombopoietin receptor agonists (TPO-RA), such as romiplostim, eltrombopag and avatrombopag are thrombopoietin agents initially designed for the treatment of immune thrombocytopenia.11, –13 All three drugs interact with the TPO receptor, c-MpL, encouraging the differentiation and proliferation of megakaryocytes.14 Romiplostim is administered subcutaneously and is a recombinant Fc-peptide fusion protein.