The myeloproliferative neoplasm of essential thrombocythemia is characterized by a sustained peripheral blood thrombocytosis, increased numbers of morphologically abnormal megakaryocytes in the bone marrow and clinically by episodes of thrombosis or hemorrhage and the propensity to transform into myelofibrosis or acute myeloid leukemia. The main treatment goals are therefore to prevent thrombotic events and to inhibit transformation with antiplatelet and myelosuppressive drugs, respectively. The pathogenesis of essential thrombocythemia is largely defined by three types of driver mutation, namely the JAK2 V617F, CALR exon 9 and MPL exon 10 mutations. Significant improvements have been in the treatment of the related myeloproliferative neoplasm of primary myelofibrosis with JAK1/2 inhibitors, but agents such as interferon and anagrelide remain relevant therapeutic options in the modern treatment algorithm for essential thrombocythemia. While hydroxyurea appears to have no effect in inducing molecular responses, reductions in the CALR mutation allele burden have been described in some essential thrombocythemia patients treated with interferon alpha and the JAK1/2 inhibitor ruxolitinib. Any effect of anagrelide on the mutant CALR allele burden in any essential thrombocythemia patients has not been previously described.