New approaches to tackle cytopenic myelofibrosis

Abstract

Myelofibrosis (MF) is a clonal hematopoietic stem cell neoplasm characterized by constitutional symptoms, splenomegaly, and risks of marrow failure or leukemic transformation and is universally driven by Jak/STAT pathway activation. Despite sharing this pathogenic feature, MF disease behavior can vary widely. MF can generally be categorized into 2 distinct subgroups based on clinical phenotype: proliferative MF and cytopenic (myelodepletive) MF. Compared to proliferative phenotypes, cytopenic MF is characterized by lower blood counts (specifically anemia and thrombocytopenia), more frequent additional somatic mutations outside the Jak/STAT pathway, and a worse prognosis. Cytopenic MF presents unique therapeutic challenges. The first approved Jak inhibitors, ruxolitinib and fedratinib, can both improve constitutional symptoms and splenomegaly but carry on-target risks of worsening anemia and thrombocytopenia, limiting their use in patients with cytopenic MF. Supportive care measures that aim to improve anemia or thrombocytopenia are often ineffective. Fortunately, new treatment strategies for cytopenic MF are on the horizon. Pacritinib, selective Jak2 inhibitor, was approved in 2022 to treat patients with symptomatic MF and a platelet count lower than 50 × 109/L. Several other Jak inhibitors are in development to extend therapeutic benefits to those with either anemia or thrombocytopenia. While many other novel non–Jak inhibitor therapies are in development for MF, most carry a risk of hematologic toxicities and often exclude patients with baseline thrombocytopenia. As a result, significant unmet needs remain for cytopenic MF. Here, we discuss clinical implications of the cytopenic MF phenotype and present existing and future strategies to tackle this challenging disease.

Association of Myelofibrosis Phenotypes with Clinical Manifestations, Molecular Profiles, and Treatments

“…We are in an exciting and dynamic era in MF treatment in light of multiple approved or emerging JAK inhibitors to treat patients presenting with the myeloproliferative and myelodepletive phenotypes [ 155 , 156 ] and the explosive growth of novel agents in advanced clinical development [ 117 , 118 ]. The wide range of new treatments will allow tailored regimens based on the heterogeneous clinical manifestations and molecular markers encountered in the myeloproliferative and myelodepletive phenotypes.…”

Delayed Hemolytic Transfusion Reaction With Hyperhemolysis Syndrome Due to Anti-M Alloantibody in Myelofibrosis: A Case Report

“…PMF is the most aggressive type of myeloproliferative neoplasms. Anemia, constitutional symptoms, and splenomegaly are the cardinal features, and generally, PMF is categorized into two subgroups: proliferative and cytopenic types [ 9 , 10 ].…”

Exploring the Molecular Landscape of Myelofibrosis, with a Focus on Ras and Mitogen-Activated Protein (MAP) Kinase Signaling

“…Mutations in CALR, lastly, induce constitutive activation of Mpl and Jak/Stat signaling, particularly in myeloproliferative neoplasms [37]. Various small molecular inhibitors against targets in the Ras/MAPK pathway or JAK/Stat pathway are included in text boxes in red font [38]. [35,36].…”