[Recent advances in the treatment of myelofibrosis]

Primary myelofibrosis (PMF) is classified as a clonal myeloproliferative neoplasm (MPN) characterized by bone marrow fibrosis and subsequent extramedullary hematopoiesis that causes progressive anemia, symptomatic splenomegaly, and various constitutional symptoms and eventual transformation into acute leukemia. The main MPN pathophysiology is the constitutive activation of JAK2/STAT signaling. JAK2, MPL, and CALR mutations, known as phenotypic driver mutations, are directly implicated in the disease pathogenesis by the activation of JAK2/STAT signaling. Moreover, other gene mutations, including methylation-related regulators, histone modification-related factors, and RNA splicing molecules, also contribute to the pathogenesis of MPN development. Patients with PMF, unlike other MPNs, experience a significantly worse prognosis. Thus, the risk of disease should be evaluated individually, and a tailored treatment plan should be developed based on each patient's disease risk. Gene mutation information is becoming more important in evaluating the risk of disease and determining treatment options. Allogeneic hematopoietic stem cell transplantation is the only curative treatment, but its indication is limited because of the age of onset. A JAK2 inhibitor, ruxolitinib, improves splenomegaly and disease-related constitutive symptoms. To date, new JAK2 inhibitors and drugs that delay the progression of fibrosis and leukemic transformation are under development and are expected to improve the prognosis for PMF.