The application of pegylated IFNα did cause a significant decrease of JAK2 allelic burden in JAK2V617F-mutant PV patients and after one year of treatment, all patients showed a hematologic and molecular response, including more than 90% of them being in complete remission with only mild adverse events (AEs) [119,120,121]. The gene discussed is JAK2; the disease is acquired polycythemia vera.