JAK2 and acquired polycythemia vera: The most commonly used cytoreductive treatments in the front-line setting include hydroxyurea and recombinant interferon (pegylated interferon alfa-2a or ropeginterferon alfa-2b), for both PV and ET, and the JAK1/JAK2 inhibitor ruxolitinib in PV patients who are hydroxyurea resistant or intolerant.