These agents include among others IFN-alpha2 and JAK2-inhibitors, which as monotherapies have been very promising with induction of deep and sustained molecular remissions in ET and PV patients, even after discontinuation of therapy (IFN-alpha2), rapid resolution of huge splenomegaly and constitutional symptoms (JAK2-inhibitor) and also resolution of bone marrow fibrosis after long term treatment (IFN-alpha2 and JAK2-inhibitor). Here, JAK2 is linked to essential thrombocythemia.