JAK2 and acquired polycythemia vera: JAK2-activating alterations may predict sensitivity to HDAC inhibitors [156,157,158]; a phase I/II study of givinostat for patients with JAK2 V617F-mutated polycythemia vera reported ORRs from 72.7% (8/11, 1 CR) to 80.7% (25/31, 3 CRs) across trial arms [159].