Modulators of the Hepcidin Pathway in Polycythemia Vera and Myelofibrosis

The peptide hepcidin is produced by the liver and serves as the central negative regulator of iron trafficking. Recently, drugs that affect the hepcidin pathway have been evaluated as potential treatment options for both controlling the degree of erythrocytosis in polycythemia vera (PV) patients as well as correcting anemia associated with myelofibrosis (MF). Under normal conditions, increased hepcidin levels limit iron absorption from the gastrointestinal tract and iron recycling from liver and splenic macrophages, thus decreasing plasma iron levels and restricting iron availability for erythropoiesis. In PV, however, unrestricted erythropoiesis occurs despite low systemic iron levels. Since hepcidin levels are relatively low in PV patients, hepcidin agonists (rusfertide, divesiran, sapablursen) are undergoing clinical development to control PV associated erythrocytosis, thereby reducing the need for therapeutic phlebotomies and myelosuppressive therapeutic options. By contrast, hepcidin levels are increased in MF patients leading to the trapping of iron in tissue macrophages which creates a picture which resembles the anemia of chronic inflammation. A number of strategies to lower hepcidin levels (the JAK2 inhibitors pacritinib and momelotinib, anti-hemojuvelin monoclonal antibody DISC-0974C) are currently undergoing clinical development to make systemic iron available for erythropoiesis and alleviate the degree of MF associated anemia. These new therapeutic options that modulate iron trafficking in PV and MF patients represent the application of greater knowledge of iron trafficking to create novel therapeutic options to treat patients with hematological malignancies.