Interferon alpha in myeloproliferative neoplasms: evidence and practical considerations for clinical care

Myeloproliferative neoplasms (MPNs) are a spectrum of clonal hematologic malignancies, characterized by an acquired somatic mutation in hematopoietic stem cells (HSC). Consequent constitutive activation of the JAK/STAT signaling pathway ultimately leads to HSC clonal expansion, a heightened inflammatory state, and aberrant trafficking of the malignant stem cells to sites of extramedullary hematopoiesis. While polycythemia vera (PV), essential thrombocythemia (ET), and myelofibrosis (MF) are distinct disease entities, each with their own diagnostic criteria, risk stratification, and molecular profiles, they share a common pathogenesis and exist on a spectrum, with overlapping clinical features, propensity for thrombohemorrhagic events, and risk for transformation to acute leukemia. Interferon alpha (IFN-α) has both anti-proliferative and immunomodulatory effects on MPN HSCs, and therefore is an effective treatment modality for PV, ET, and MF. In this review, we discuss the rationale for IFN-α use in MPNs, examine the evidence supporting its use, and convey practical considerations.