TO THE EDITOR:

Essential thrombocythemia (ET) is a myeloproliferative neoplasm (MPN) defined by thrombocytosis, increased risk of vascular thrombosis,1,2  hemorrhage, and progression to myelofibrosis4,5  and acute myeloid leukemia.4,5  Patients are risk-stratified to identify those who might benefit from cytoreduction to reduce the risk of vascular complications. Resistance/intolerance to hydroxycarbamide (HC-RES/INT), a first-line cytoreductive treatment, develops in 20% of high-risk patients with increased risk of disease progression and reduced survival. New approaches are needed to predict disease-transformation risk in these patients, together with development of therapies that reduce this risk.

Following the discovery of the Janus kinase 2 (JAK2) mutation (JAK2V617F), present in ∼50% of ET, the first approved JAK1/JAK2 inhibitor, ruxolitinib (RUX), is now widely used for treatment of myelofibrosis10  and polycythemia vera.11  The MAJIC-ET trial explored...

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