Thrombopoietin receptor agonists: a new immune modulatory strategy in immune thrombocytopenia?

In 2008, new drugs that mimic the effects of thrombopoietin became available for the treatment of primary immune thrombocytopenia, eg, romiplostim and eltrombopag. These drugs activate the thrombopoietin receptor, stimulate the production of megakaryocytes, and increase the production of platelets. Important clinical observation has been gained, such as unexpected long-term remission after stopping thrombopoietin receptor agonists. The pathophysiology of this unforeseen cure is currently the subject of discussion and is investigated in clinical trials and laboratory research projects. Here we evaluate the different hypotheses on how thrombopoietin receptor agonists can affect the immune system, particularly the induction of tolerance, and by which mechanisms this may be achieved.