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Polycythemia vera (PV) is a chronic myeloproliferative neoplasm. Virtually all PV patients are iron deficient at presentation and/or during the course of their disease. The co-existence of iron deficiency and polycythemia presents a physiological disconnect. Hepcidin, the master regulator of iron metabolism, is regulated by circulating iron levels, erythroblast secretion of erythroferrone, and inflammation. Both decreased circulating iron and increased erythroferrone levels, which occur as a consequence of erythroid hyperplasia in PV, are anticipated to suppress hepcidin and enable recovery from iron deficiency. Inflammation which accompanies PV is likely to counteract hepcidin suppression, but the relatively low serum ferritin levels observed suggest that inflammation is not a major contributor to the dysregulated iron metabolism. Furthermore, potential defects in iron absorption, aberrant hypoxia sensing and signaling, and frequency of bleeding to account for iron deficiency in PV patients have not been fully elucidated. Insufficiently suppressed hepcidin given the degree of iron deficiency in PV patients strongly suggests that disordered iron metabolism is an important component of the pathobiology of PV. Normalization of hematocrit levels using therapeutic phlebotomy is the most common approach for reducing the incidence of thrombotic complications, a therapy which exacerbates iron deficiency, contributing to a variety of non-hematological symptoms. The use of cytoreductive therapy in high-risk PV patients frequently works more effectively to reverse PV-associated symptoms in iron-deficient relative to iron-replete patients. Lastly, differences in iron-related parameters between PV patients and mice with JAK2 V617F and JAK2 exon 12 mutations suggest that specific regions in JAK2 may influence iron metabolism by nuanced changes of erythropoietin receptor signaling. In this review, we comprehensively discuss the clinical consequences of iron deficiency in PV, provide a framework for understanding the potential dysregulation of iron metabolism, and present a rationale for additional therapeutic options for iron-deficient PV patients.

Myelofibrosis is the advanced stage of the Philadelphia chromosome-negative myeloproliferative neoplasms (MPNs), characterized by systemic inflammation, hematopoietic failure in the bone marrow, and development of extramedullary hematopoiesis, mainly in the spleen. The only potentially curative therapy for this disease is hematopoietic stem cell transplantation, an option that may be offered only to those patients with a compatible donor and with an age and functional status that may face its toxicity. By contrast, with the Philadelphia-positive MPNs that can be dramatically modified by inhibitors of the novel BCR-ABL fusion-protein generated by its genetic lesion, the identification of the molecular lesions that lead to the development of myelofibrosis has not yet translated into a treatment that can modify the natural history of the disease. Therefore, the cure of myelofibrosis remains an unmet clinical need. However, the excitement raised by the discovery of the genetic lesions has inspired additional studies aimed at elucidating the mechanisms driving these neoplasms towards their final stage. These studies have generated the feeling that the cure of myelofibrosis will require targeting both the malignant stem cell clone and its supportive microenvironment. We will summarize here some of the biochemical alterations recently identified in MPNs and the novel therapeutic approaches currently under investigation inspired by these discoveries.

Anti-B-cell maturation antigen (BCMA) chimeric antigen receptor T-cell (CAR T) therapy shows remarkable efficacy in patients with relapsed and/or refractory (R/R) multiple myeloma (MM). HBI0101, a novel second generation optimized anti- BCMA CAR T-cell therapy, was developed in an academic setting. We conducted a phase I dose-escalation study of HBI0101 (cohort 1: 150x106 CAR T cells, n=6; cohort 2: 450x106 CAR T cells, n=7; cohort 3: 800x106 CAR T cells, n=7) in 20 heavily pre-treated R/R MM patients. Grade 1-2 cytokine release syndrome (CRS) was reported in 18 patients (90%). Neither grade 3-4 CRS nor neurotoxicity of any grade were observed. No dose-limiting toxicities were observed in any cohort. The overall response rate (ORR), (stringent) complete response (CR/sCR), and very good partial response rates were 75%, 50%, and 25%, respectively. Response rates were dose-dependent with 85% ORR, 71% CR, and 57% minimal residual disease negativity in the high-dose cohort 3. Across all cohorts, the median overall survival (OS) was 308 days (range 25-466+), with an estimated OS of 55% as of June 27th (data cut-off). The median progression-free survival was 160 days, with 6 subjects remaining progression free at the time of data cut-off. Our findings demonstrate the manageable safety profile and efficacy of HBI0101. These encouraging data support the decentralization of CAR T production in an academic setting, ensuring sufficient CAR T supply to satisfy the increasing local demand. Clinicaltrials.gov NCT04720313.