In this study, we investigated the effect of the selective JAK2 inhibitor Fedratinib 10, in mouse models of MPN driven by JAK2V617F or TPO/MPL/JAK2 with increasing disease severity mimicking human PV, human PV with its evolution into PPMF and human ET with a rapid evolution into PTMF. The gene discussed is JAK2; the disease is acquired polycythemia vera.