The histone deacetylase (HDAC) inhibitor ITF2357 can inhibit the removal of acetyl groups and the process that leads to chromatin condensation and transcriptional repression. As a consequence, ITF2357 blocks the clonogenic activity of peripheral blood progenitor cells isolated from patients bearing the JAK2V617F mutation (Panel A). Moreover, exposure to ITF2357 (250 nM) is followed by rapid degradation of either total and phosphorylated JAK2 protein in JAK2V617F-mutated HEL cells (Panel B). Finally, at the same concentration, ITF2357 increases the proportion of apoptotic cells and reduces cells in M phase (Panel C).