Ruxolitinib, a JAK1/2 inhibitor, has been approved for the treatment of patients with intermediate- and high-risk MF, and as a second-line therapy for PV.4 Although ruxolitinib can provide some clinical benefits, including superior reduction of splenomegaly and symptom improvement,5,6 it has several drawbacks. This evidence concerns the gene JAK1 and acquired polycythemia vera.