Persistent leukocytosis in polycythemia vera is associated with disease evolution but not thrombosis

The evolving landscape of polycythemia vera therapies

INTRODUCTION

The treatment landscape of polycythemia vera (PV) has seen major advancements within the last decade including approval of ruxolitinib in the second line setting after hydroxyurea, ropegylated interferon-α2b, and advanced clinical development of a novel class of agents called hepcidin mimetics.

AREAS COVERED

We provide a comprehensive review of the evidence discussing the risk stratification, treatment indications, role and limitations of phlebotomy only approach and pivotal trials covering nuances related to the use of interferon-α (IFN-α), ruxolitinib, hepcidin mimetics, and upcoming investigational agents including HDAC and LSD1 inhibitors.

EXPERT OPINION

The research paradigm in PV is slowly shifting from the sole focus on hematocrit control and moving toward disease modification. The discovery of hepcidin mimetics has come as a breakthrough in restoring iron homeostasis, achieving phlebotomy-independence and may lead to improved thrombosis-free survival with stricter hematocrit control. On the other hand, emerging data with IFN- α and ruxolitinib as well as combination of the two agents suggests the potential for achieving molecular remission in a subset of PV patients and long-term follow-up is awaited to validate the correlation of molecular responses with clinically relevant outcomes of progression-free and thrombosis-free survival.

The role of leukocytes in myeloproliferative neoplasm thromboinflammation

Classic myeloproliferative neoplasms lacking the Philadelphia chromosome are stem cell disorders characterized by the proliferation of myeloid cells in the bone marrow and increased counts of peripheral blood cells. The occurrence of thrombotic events is a common complication in myeloproliferative neoplasms. The heightened levels of cytokines play a substantial role in the morbidity and mortality of these patients, establishing a persistent proinflammatory condition that culminates in thrombosis. The etiology of thrombosis remains intricate and multifaceted, involving blood cells and endothelial dysfunction, the inflammatory state, and the coagulation cascade, leading to hypercoagulability. Leukocytes play a pivotal role in the thromboinflammatory process of myeloproliferative neoplasms by releasing various proinflammatory and prothrombotic factors as well as interacting with other cells, which contributes to the amplification of the clotting cascade and subsequent thrombosis. The correlation between increased leukocyte counts and thrombotic risk has been established. However, there is a need for an accurate biomarker to assess leukocyte activation. Lastly, tailored treatments to address the thrombotic risk in myeloproliferative neoplasms are needed. Therefore, this review aims to summarize the potential mechanisms of leukocyte involvement in myeloproliferative neoplasm thromboinflammation, propose potential biomarkers for leukocyte activation, and discuss promising treatment options for controlling myeloproliferative neoplasm thromboinflammation.

The clinical significance of TAT, PIC, TM, and t-PAIC in vascular events of BCR/ABL-negative myeloproliferative neoplasms

Predicting the likelihood vascular events in patients with BCR/ABL1-negative myeloproliferative neoplasms (MPN) is essential for the treatment of the disease. However, effective assessment methods are lacking. Thrombin-antithrombin complex (TAT), plasmin-α2- plasmininhibitor complex (PIC), thrombomodulin (TM), and tissue plasminogen activator-inhibitor complex (t-PAIC) are the new direct indicators for coagulation and fibrinolysis. The aim of this study was to investigate the changes of these four new indicators in thrombotic and hemorrhagic events in BCR/ABL1-negative MPN. The study cohort of 74 patients with BCR/ABL negative myeloproliferative disorders included essential thrombocythemia, polycythemia vera, and primary myelofibrosis (PMF). A panel of 4 biomarkers, including TAT, PIC, TM, and t-PAIC were determined using Sysmex HISCL5000 automated analyzers, whereas fibrin/fibrinogen degradation products (FDP), D-dimer and Antithrombin III (ATIII) were analyzed using Sysmex CS5100 coagulation analyzer. A total of 24 (32.4%) patients experienced thrombotic events and hemorrhagic events occurred in 8 patients (10.8%). Compared to patients without hemorrhagic-thrombotic events, patients with thrombotic events had higher fibrinogen (FIB) level, FDP level and lower ATIII activity, while patients with hemorrhagic events had lower white blood cell count and hemoglobin level, higher FDP level (P < 0.05). Patients with a JAK2V617F mutation were more likely to experience thrombotic events (P < 0.05). In addtion, patients with thrombotic events had higher TAT, PIC, TM, and t-PAIC levels than patients without hemorrhagic-thrombotic events (P < 0.05), whereas patients with hemorrhagic events had a lower median value in TAT and TM (no statistical difference, P > 0.05). Patients with higher TAT, TM and t-PAIC were more likely to experience thrombotic events (P < 0.05), and only TAT was positively correlated with thrombotic events (Spearman  r =0.287, P = 0.019). TAT, PIC, TM, and t-PAIC combined with ATIII and FDP have a certain value for predicting thrombosis in patients with BCR/ABL1-negative MPN. These 6 parameters are worth further exploration as predictive factors and prognostic markers for early thrombotic events.

Association between elevated white blood cell counts and thrombotic events in polycythemia vera: analysis from REVEAL

ABSTRACT

Polycythemia vera (PV) is a myeloproliferative neoplasm characterized by clonal proliferation of hematopoietic progenitor cells and is associated with an increased risk of thrombotic events (TEs). Established risk factors for TEs in patients with PV include advanced age, TE history, and elevated hematocrit. Although an association of TE with elevated white blood cell (WBC) counts has been suggested by retrospective studies, this relationship needs further validation. The prospective observational study of patients with polycythemia vera in US clinical practices (REVEAL) study collected prospective clinical data from 2510 patients with PV with a median follow-up of 44.7 months (range, 2-59 months) from enrollment. Using time-dependent covariate Cox proportional hazards models, blood counts were individually modeled with sex, age, disease duration, TE history at enrollment (baseline covariates), and treatment (time-dependent covariate). Analysis of 2271 participants identified 142 TEs in 106 patients. Significant associations with initial TE occurrence during the study period were observed for hematocrit level >45% (hazard ratio [HR], 1.84; 95% confidence interval [95% CI], 1.234-2.749; P = .0028) and WBCs >11 × 109/L (HR, 2.35; 95% CI, 1.598-3.465; P < .0001). Elevated WBC count was significantly associated with initial TE occurrence in both low-risk and high-risk PV. When hematocrit was controlled at ≤45%, WBC count >12 × 109/L was significantly associated with TE occurrence (HR, 1.95; 95% CI, 1.066-3.554; P = .0300). The results support incorporation of WBC count into PV risk stratification and studies of treatment strategies, and indicate the importance of controlling both hematocrit and WBC count in disease management. This trial was registered at www.clinicaltrials.gov as #NCT02252159.

A Review About the Assessment of the Bleeding and Thrombosis Risk for Patients With Myeloproliferative Neoplasms Scheduled for Surgery

Myeloproliferative neoplasms (MPNs) present a unique challenge in surgical management due to their inherent predisposition to both bleeding and thrombosis. MPNs are a heterogenous group of acquired clonal conditions. The three classic MPNs are essential thrombocythemia (ET), myelofibrosis (PMF), and polycythemia vera (PV). All subtypes of MPN are associated with both thrombotic and bleeding complications. There are four risk categories for thrombosis in MPN patients: age, thrombosis history, and JAK-2 mutation. They are further classified as very low, low, intermediate, and high risk. The genetic landscape of MPN is fascinating and complex like all myeloid disorders. Bleeding risk can be assessed through leukocytosis, thrombocytosis, acquired von Willebrand syndrome (AVWS), and a previous history of bleeding in a patient. Risk assessment and perioperative management are important aspects of improving the quality of life and preventing complications in surgeries. Preoperative management includes a risk assessment of venous thromboembolism, use of appropriate pharmacological treatment, platelet count control, and correction and cardiovascular risk factors. This review summarizes the assessment of bleeding and thrombosis risk for patients with MPNs scheduled for surgery. Furthermore, this review discusses various tools that can be used to identify MPN patients at risk of thrombosis prior to surgery.

Platelets and neutrophils cooperate to induce increased neutrophil extracellular trap formation in JAK2V617F myeloproliferative neoplasms

BACKGROUND

Neutrophils participate in the pathogenesis of thrombosis through the formation of neutrophil extracellular traps (NETs). Thrombosis is the main cause of morbidity and mortality in patients with myeloproliferative neoplasms (MPNs). Recent studies have shown an increase in NET formation (NETosis) both in patients with JAK2V617F neutrophils and in mouse models, and reported the participation of NETosis in the pathophysiology of thrombosis in mice.

OBJECTIVES

This study investigated whether JAK2V617F neutrophils are sufficient to promote thrombosis or whether their cooperation with other blood cell types is necessary.

METHODS

NETosis was studied in PF4iCre;Jak2V617F/WT mice expressing JAK2V617F in all hematopoietic lineages, as occurs in MPNs, and in MRP8Cre;Jak2V617F/WT mice in which JAK2V617F is expressed only in leukocytes.

RESULTS

In PF4iCre;Jak2V617F/WT mice, an increase in NETosis and spontaneous lung thrombosis abrogated by DNAse administration were observed. The absence of spontaneous NETosis or lung thrombosis in MRP8Cre;Jak2V617F/WT mice suggested that mutated neutrophils alone are not sufficient to induce thrombosis. Ex vivo experiments demonstrated that JAK2V617F-mutated platelets trigger NETosis by JAK2V617F-mutated neutrophils. Aspirin treatment in PF4iCre;Jak2V617F/WT mice reduced NETosis and reduced lung thrombosis. In cytoreductive-therapy-free patients with MPN treated with aspirin, plasma NET marker concentrations were lower than that in patients with MPN not treated with aspirin.

CONCLUSION

Our study demonstrates that JAK2V617F neutrophils alone are not sufficient to promote thrombosis; rather, platelets cooperate with neutrophils to promote NETosis in vivo. A new role for aspirin in thrombosis prevention in MPNs was also identified.

Cytoreduction for ET and PV: who, what, when, and how?

Thrombotic complications are the primary contributor to morbidity and mortality in essential thrombocythemia (ET) and polycythemia vera (PV). Cytoreductive therapy is the main tool for primary or tertiary thrombosis prevention in these diseases. In general, high-thrombotic-risk patients and those with symptoms that may be ameliorated from cytoreductive therapy are candidates for this treatment, although the decision is highly individualized. Approved options for cytoreduction in ET and PV include hydroxyurea, long-acting interferons, anagrelide in ET, and ruxolitinib in PV. Selecting the ideal agent requires careful consideration of the toxicity profiles and individual treatment goals. In this review the existing literature on cytoreductive decisions in ET and PV is summarized, with an emphasis on risk-stratification, highlighting the need for personalized care in order to maximize the benefit of these therapies while minimizing toxicities.

Moving toward disease modification in polycythemia vera

Polycythemia vera (PV) belongs to the BCR-ABL1-negative myeloproliferative neoplasms and is characterized by activating mutations in JAK2 and clinically presents with erythrocytosis, variable degrees of systemic and vasomotor symptoms, and an increased risk of both thromboembolic events and progression to myelofibrosis and acute myeloid leukemia (AML). Treatment selection is based on a patient's age and a history of thrombosis in patients with low-risk PV treated with therapeutic phlebotomy and aspirin alone, whereas cytoreductive therapy with either hydroxyurea or interferon alfa (IFN-α) is added for high-risk disease. However, other disease features such as significant disease-related symptoms and splenomegaly, concurrent thrombocytosis and leukocytosis, or intolerance of phlebotomy can constitute an indication for cytoreductive therapy in patients with otherwise low-risk disease. Additionally, recent studies demonstrating the safety and efficacy (ie, reduction in phlebotomy requirements and molecular responses) of ropegylated IFN-α2b support its use for patients with low-risk PV. Additionally, emerging data suggest that early treatment is associated with higher rates of molecular responses, which might eventually enable time-limited therapy. Nonetheless, longer follow-up is needed to assess whether molecular responses associate with clinically meaningful outcome measures such as thrombosis and progression to myelofibrosis or AML. In this article, we provide an overview of the current and evolving treatment landscape of PV and outline our vision for a patient-centered, phlebotomy-free, treatment approach using time-limited, disease-modifying treatment modalities early in the disease course, which could ultimately affect the natural history of the disease.

Polycythemia vera: 2024 update on diagnosis, risk-stratification, and management

DISEASE OVERVIEW

Polycythemia vera (PV) is a JAK2-mutated myeloproliferative neoplasm characterized by clonal erythrocytosis; other features include leukocytosis, thrombocytosis, splenomegaly, pruritus, constitutional symptoms, microcirculatory disturbances, and increased risk of thrombosis and progression into myelofibrosis (post-PV MF) or acute myeloid leukemia (AML).

DIAGNOSIS

A working diagnosis is considered in the presence of a JAK2 mutation associated with hemoglobin/hematocrit levels of >16.5 g/dL/49% in men or 16 g/dL/48% in women; morphologic confirmation by bone marrow examination is advised but not mandated.

CYTOGENETICS

Abnormal karyotype is seen in 15%-20% of patients with the most frequent sole abnormalities being +9 (5%), loss of chromosome Y (4%), +8 (3%), and 20q- (3%).

MUTATIONS

Over 50% of patients harbor DNA sequence variants/mutations other than JAK2, with the most frequent being TET2 (18%) and ASXL1 (15%). Prognostically adverse mutations include SRSF2, IDH2, RUNX1, and U2AF1, with a combined incidence of 5%-10%.

SURVIVAL AND PROGNOSIS

Median survival is ⁓15 years but exceeds 35 years for patients aged ≤40 years. Risk factors for survival include older age, leukocytosis, abnormal karyotype, and the presence of adverse mutations. Twenty-year risk for thrombosis, post-PV MF, or AML are ⁓26%, 16% and 4%, respectively.

RISK FACTORS FOR THROMBOSIS

Two risk categories are considered: high (age >60 years or thrombosis history) and low (absence of both risk factors). Additional predictors for arterial thrombosis include cardiovascular risk factors and for venous thrombosis higher absolute neutrophil count and JAK2V617F allele burden.

TREATMENT

Current goal of therapy is to prevent thrombosis. Periodic phlebotomy, with a hematocrit target of <45%, combined with once- or twice-daily aspirin (81 mg) therapy, absent contraindications, is the backbone of treatment in all patients, regardless of risk category. Cytoreductive therapy is reserved for high-risk disease with first-line drugs of choice being hydroxyurea and pegylated interferon-α and second-line busulfan and ruxolitinib. In addition, systemic anticoagulation is advised in patients with venous thrombosis history.

ADDITIONAL TREATMENT CONSIDERATIONS

At the present time, we do not consider a drug-induced reduction in JAK2V617F allele burden, which is often incomplete and seen not only with peg-IFN but also with ruxolitinib and busulfan, as an indicator of disease-modifying activity, unless accompanied by cytogenetic and independently-verified morphologic remission. Accordingly, we do not use the specific parameter to influence treatment choices. The current review also includes specific treatment strategies in the context of pregnancy, splanchnic vein thrombosis, pruritus, perioperative care, and post-PV MF.

Predictors of Response to Hydroxyurea and Switch to Ruxolitinib in HU-Resistant Polycythaemia VERA Patients: A Real-World PV-NET Study

In polycythemia vera (PV), the prognostic relevance of an ELN-defined complete response (CR) to hydroxyurea (HU), the predictors of response, and patients' triggers for switching to ruxolitinib are uncertain. In a real-world analysis, we evaluated the predictors of response, their impact on the clinical outcomes of CR to HU, and the correlations between partial or no response (PR/NR) and a patient switching to ruxolitinib. Among 563 PV patients receiving HU for ≥12 months, 166 (29.5%) achieved CR, 264 achieved PR, and 133 achieved NR. In a multivariate analysis, the absence of splenomegaly (p = 0.03), pruritus (p = 0.002), and a median HU dose of ≥1 g/day (p < 0.001) remained associated with CR. Adverse events were more frequent with a median HU dose of ≥1 g/day. Overall, 283 PR/NR patients (71.3%) continued HU, and 114 switched to ruxolitinib. In the 449 patients receiving only HU, rates of thrombosis, hemorrhages, progression, and overall survival were comparable among the CR, PR, and NR groups. Many PV patients received underdosed HU, leading to lower CR and toxicity rates. In addition, many patients continued HU despite a PR/NR; however, splenomegaly and other symptoms were the main drivers of an early switch. Better HU management, standardization of the criteria for and timing of responses to HU, and adequate intervention in poor responders should be advised.

JAK2V617F variant allele frequency, non-driver mutations, single-nucleotide variants and polycythemia vera outcome

INTRODUCTION

Despite comparatively favourable prognosis in polycythemia vera (PV) patients (pts), the overall survival is shorter compared to the age-matched general population. The aim of the study was to evaluate the impact of chosen laboratory and genetic factors on the individual disease outcome, i.e. risk of thrombosis, myelofibrosis/blastic transformation and death.

MATERIALS AND METHODS

The study group consisted of 151 pts and 57 healthy donors (HD).

RESULTS

JAK2V617F mutation was found in 96.7% (146/151) of the studied pts. JAK2 exon 12 mutations were identified in 2 individuals. The coexistence of JAK2V617F and JAK2 exon 12 mutation was confirmed in 2 other pts. In one case, neither JAK2V617F nor JAK2 exon 12 mutation was found. The presence of ten different non-driver mutations (ASXL1, SRSF2, U2AF1, IDH2) in eight of the analyzed pts (5.3%) was confirmed. The overall frequency of thrombotic events (TE) in the studied PV group was 23.8% (36/151). In patients with TE, median platelet count was lower than in pts without TE. Thrombotic risk did not depend on JAK2 rs12343867, TERT rs2736100, OBFC1 rs9420907 SNV, however, we found a novel strong tendency towards statistical significance between the CC genotype miR-146a rs2431697 and thrombosis. The disease progression to fibrotic phase was confirmed in 9% of the pts. Fibrotic transformation in PV pts was affected mainly by JAK2V617F variant allele frequency (VAF) and the presence of coexisting non-driver variants. The high JAK2V617F VAF and elevated white blood cell (WBC) count at the time of diagnosis were associated with an increased risk of death.

CONCLUSION

Therefore, in our opinion, complex, laboratory and genetic PV pts evaluation at the time of diagnosis should be incorporated into a new prognostic scoring system to more precisely define the PV prognosis and to optimize the therapeutic decision-making process.

Polycythemia Vera: Thinking Beyond the Hematocrit

Polycythemia vera is a Philadelphia chromosome-negative myeloproliferative neoplasm that results in increased myeloproliferation. It is a debilitating disease characterized by the overproduction of red blood cells, but it also can result in increased white blood cells and platelets. Patients experience a shortened overall survival due to an increased risk of thrombotic events, including stroke, myocardial infarction, pulmonary embolism, and deep vein thrombosis. Current treatment strategies in clinical practice are driven by mitigating the risk of these thrombotic events by reducing patients' hematocrit. In addition to thrombosis risk, polycythemia vera patients have constitutional symptoms such as fatigue, itching, bone pain, erythromelalgia, and splenomegaly. An increased risk of transformation of their disease to acute myeloid leukemia and/or myelofibrosis can also affect long-term survival in polycythemia vera. Additional research has identified other risk factors, such as increased white blood cells, increased platelet count, and cytokine levels, which can alter the prognosis of the disease. In this review, we will discuss the current treatment strategies in polycythemia vera and determine if incorporating additional biomarkers as endpoints is feasible in clinical practice.

Novel therapeutic strategies for essential thrombocythemia/polycythemia vera

Myeloproliferative neoplasms (MPNs) are clonal disorders of hematopoietic stem cells; these include polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF). MPNs are inflammatory cancers, wherein the malignant clone generates cytokines that sustain the inflammatory drive in a self-perpetuating vicious cycle. The course of MPNs follows a biological continuum, that is, from early cancer stages (ET/PV) to advanced myelofibrosis as well as impending leukemic transformation. MPN-related symptoms, e.g., fatigue, general weakness, and itching, are caused by inflammatory cytokines. Thrombosis and bleeding are also exacerbated by inflammatory cytokines in patients with MPN. Until recently, the primary objective of ET and PV therapy was to increase survival rates by preventing thrombosis. However, several medications have recently demonstrated the ability to modify the course of the disease; symptom relief is expected for most patients. In addition, there is increasing interest in the active treatment of patients at low risk with PV and ET. This review focuses on the ET/PV treatment strategies as well as novel treatment options for clinical development.

JAK2 V617F allele burden in polycythemia vera: burden of proof

Polycythemia vera (PV) is a hematopoietic stem cell neoplasm defined by activating somatic mutations in the JAK2 gene and characterized clinically by overproduction of red blood cells, platelets, and neutrophils; a significant burden of disease-specific symptoms; high rates of vascular events; and evolution to a myelofibrosis phase or acute leukemia. The JAK2V617F variant allele frequency (VAF) is a key determinant of outcomes in PV, including thrombosis and myelofibrotic progression. Here, we critically review the dynamic role of JAK2V617F mutation burden in the pathogenesis and natural history of PV, the suitability of JAK2V617F VAF as a diagnostic and prognostic biomarker, and the utility of JAK2V617F VAF reduction in PV treatment.

Masked polycythemia vera due to iron deficiency anemia

A 74-year-old Japanese woman was referred to our hospital for leukocytosis that occurred for the past one year. Oral iron supplementation was started as iron deficiency anemia (IDA), but three months later, physical examination revealed flushing of the skin on her hands. Finally polycythemia vera (PV) with IDA was diagnosed. There have been reports of PV combined with IDA, which can mask diagnosis and delay treatment because of the lack of symptoms and the anemic presentation. Several possibilities for the pathogenesis of IDA associated with PV have been proposed, including the presence of Helicobacter pylori.

Cytological Diagnosis of Classic Myeloproliferative Neoplasms at the Age of Molecular Biology

Myeloproliferative neoplasms (MPN) are clonal hematopoietic stem cell-derived disorders characterized by uncontrolled proliferation of differentiated myeloid cells. Two main groups of MPN, BCR::ABL1-positive (Chronic Myeloid Leukemia) and BCR::ABL1-negative (Polycythemia Vera, Essential Thrombocytosis, Primary Myelofibrosis) are distinguished. For many years, cytomorphologic and histologic features were the only proof of MPN and attempted to distinguish the different entities of the subgroup BCR::ABL1-negative MPN. World Health Organization (WHO) classification of myeloid neoplasms evolves over the years and increasingly considers molecular abnormalities to prove the clonal hematopoiesis. In addition to morphological clues, the detection of JAK2, MPL and CALR mutations are considered driver events belonging to the major diagnostic criteria of BCR::ABL1-negative MPN. This highlights the preponderant place of molecular features in the MPN diagnosis. Moreover, the advent of next-generation sequencing (NGS) allowed the identification of additional somatic mutations involved in clonal hematopoiesis and playing a role in the prognosis of MPN. Nowadays, careful cytomorphology and molecular biology are inseparable and complementary to provide a specific diagnosis and to permit the best follow-up of these diseases.

Leukocytosis and MPNs: Where do we stand?

The Philadelphia-negative myeloproliferative neoplasms (MPNs)-essential thrombocythemia (ET), polycythemia vera (PV) and myelofibrosis (MF), are characterized by a propensity for thrombotic events and variable risks for transformation to MF (for ET and PV) and acute leukemia. Leukocytosis, which serves a minor criterion for the diagnosis of MF, is present in a significant portion of patients with MPNs. The relation and impact of leukocytosis on disease course and outcomes of patients with MPNs has been studied in multiple, large retrospective and prospective studies. Despite this, the association of leukocytosis and thrombosis, fibrosis and leukemic transformation remains unclear. This article details the published investigations regarding the impact of leukocytosis in MPNs and explores the changing role of leukocytosis in disease prognostication as increasing emphasis is placed on molecular and genetic studies.

Management of polycythemia vera: A survey of treatment patterns in Italy

OBJECTIVES

Polycythemia vera (PV) is an acquired clonal hematopoietic stem cell disorder characterized by the overproduction of red blood cells. It has long been underlined that there are differences in treatment patterns in routine practice. Therapeutic strategies have also expanded, and in recent years the JAK1/JAK2 inhibitor ruxolitinib has emerged as a second-line therapeutic option in patients who are intolerant to or resistant to hydroxyurea. Determining the impact of changes on practice patterns is of interest, especially for aspects that lack detailed guidance for management.

METHODS

To gain insights into treatment patterns by clinicians treating patients with PV in Italy, we carried out a survey of 60 hematologists and transfusion specialists. The questions covered: treatment of low-risk patients, definition of significant leukocytosis, splenomegaly and excessive phlebotomies, resistance/intolerance to hydroxyurea, use of ruxolitinib, cytoreductive therapy, and vaccines.

RESULTS

In general, the results of the survey indicate that there is a large heterogeneity in management of patients with PV across these areas.

CONCLUSIONS

While helping to provide greater understanding of treatment patterns for patients with PV in Italy, our survey highlights the need for additional clinical studies to obtain more precise guidance for the routine care of patients with PV.

The international consensus classification of myeloid neoplasms and acute Leukemias: myeloproliferative neoplasms

A group of international experts, including hematopathologists, oncologists, and geneticists were recently summoned (September 2021, Chicago, IL, USA) to update the 2016/17 World Health Organization classification system for hematopoietic tumors. After careful deliberation, the group introduced the new International Consensus Classification (ICC) for Myeloid Neoplasms and Acute Leukemias. This current in-depth review focuses on the ICC-2022 category of JAK2 mutation-prevalent myeloproliferative neoplasms (MPNs): essential thrombocythemia, polycythemia vera, primary myelofibrosis, and MPN, unclassifiable. The ICC MPN subcommittee chose to preserve the primary role of bone marrow morphology in disease classification and diagnostics, while also acknowledging the complementary role of genetic markers for establishing clonality, facilitating MPN subtype designation, and disease prognostication.

Prognostic Role of Cell Blood Count in Chronic Myeloid Neoplasm and Acute Myeloid Leukemia and Its Possible Implications in Hematopoietic Stem Cell Transplantation

Numerous prognostic indexes have been developed in hematological diseases based on patient characteristics and genetic or molecular assessment. However, less attention was paid to more accessible parameters, such as neutrophils, lymphocytes, monocytes, and platelet counts. Although many studies have defined the role of neutrophil-to-lymphocyte or platelet-to-lymphocyte in lymphoid malignancies, few applications exist for myeloid neoplasm or hematopoietic stem cell transplantation procedures. In this review, we synthesized literature data on the prognostic value of count blood cells in myeloid malignancies and hematopoietic stem cell transplantation in the context of classical prognostic factors and clinical outcomes.

Towards a Personalized Definition of Prognosis in Philadelphia-Negative Myeloproliferative Neoplasms

Purpose of Review

Philadelphia-negative myeloproliferative neoplasms (MPNs) include polycythemia vera (PV), essential thrombocythemia (ET), prefibrotic (pre-), and overt-primary myelofibrosis (primary MF, PMF). PV and ET could evolve into secondary MF (SMF), whose early diagnosis relies on monitoring signs of possible progression. All MPNs have a risk of blast phase (BP), that is associated with a very dismal outcome. Overall survival (OS) is different among MPNs, and disease-specific prognostic scores should be applied for a correct clinical management. In this review, an overview of current prognostic scores in MPNs will be provided.

Recent Findings

The biological complexity of MPNs and its role on the trajectory of disease outcome have led to the design of integrated prognostic models that are nowadays of common use in PMF patients. As for PV and ET, splicing gene mutations could have a detrimental role, but with the limit of the not routinary recommended application of extensive molecular analysis in these diseases. SMF is recognized as a distinct entity compared to PMF, and OS estimates should be calculated by the MYSEC-PM (Myelofibrosis SECondary-prognostic model). Both in PMF and SMF, decisions as selection of patients potentially candidates to allogenic stem cell transplant or that could benefit from an early shift from standard treatment are based not only on conventional prognostic scores, but also on multivariable algorithms.

Summary

The expanding landscape of risk prediction for OS, evolution to BP, and SMF progression from PV/ET informs personalized approach to the management of patients affected by MPNs.

Advances in Risk Stratification and Treatment of Polycythemia Vera and Essential Thrombocythemia

PURPOSE OF REVIEW

Estimating and modifying thrombotic risk is currently the mainstay of care for patients with polycythemia vera (PV) and essential thrombocythemia (ET). In recent years, however, increased attention has shifted towards quality of life and disease modification. In this review, we discuss recent advances in risk stratification, present updated results for ruxolitinib and interferon randomized clinical trials, discuss new approaches in antiplatelet and anticoagulant treatment, and summarize early phase trials of novel agents and emerging therapeutic concepts for the treatment of PV and ET.

RECENT FINDINGS

International collaborations and novel technologies, i.e., next-generation sequencing and machine learning techniques, have demonstrated excellent abilities to improve thrombotic risk stratification in PV and ET. Updated results from ruxolitinib and interferon randomized clinical trials have confirmed excellent efficacy and safety of these agents, both as first- and second-line treatments. Early trials of novel agents (histone deacetylase inhibitors, telomerase inhibitors, lysine-specific demethylase-1 inhibitors, human double-minute 2 inhibitors, and hepcidin mimetics) have shown encouraging efficacy and safety in blood count control, reduction of splenomegaly, and alleviation of disease-related symptoms. Finally, accumulating evidence suggested that direct oral anticoagulants may be a valid therapeutic alternative to warfarin for prolonged thromboprophylaxis. International collaborations ("big data") with the help of new technologies represent an exciting new approach to analyze rare outcomes in rare diseases, especially for identifying novel prognostic biomarkers in PV and ET. Randomized clinical trials are also needed to fully elucidate whether novel agents may establish new standards of care.

Longitudinal trends of peripheral blood counts in polycythaemia vera and essential thrombocythemia patients in the UK

There is sparse evidence of how well haematological targets are met in practice for essential thrombocythemia (ET) and polycythaemia vera (PV) patients. Patient data was collected between 2008 and 2020 from two UK NHS Trusts for ET and PV patients. Longitudinal changes in peripheral blood counts, including the proportion of patients meeting peripheral blood count remission, was modelled. Relative risk of cardiovascular-related events for patients achieving remission within 3-months was estimated. A total of 620 ET and 429 PV patients were analysed. For high-risk patients, haematological parameters decreased in the first months of observation then stabilised within normal reference ranges until year 5. Total time spent in peripheral blood count remission was 39.2% for ET and 29.1% for PV. A lower proportion of ET patients reached target platelet counts (48.3%) compared to WBC (79.1%), whilst PV patients were less likely to reach target haematocrit levels (56.9%) compared to platelets (77.3%) or WBC (74.6%). There was no statistically significant association between reaching target blood counts within 3-months and cardiovascular risk. Complete haematological remission remains a challenging target in managing PV and ET, however this study was unable to show statistically-significant evidence that this was associated with increased risk of cardiovascular events.

Anagrelide for platelet-directed cytoreduction in polycythemia vera: Insights into utility and safety outcomes from a large multi-center database

Anagrelide (ANA) is a platelet-specific cytoreductive agent utilized in the guideline-directed management of high-risk essential thrombocythemia. In the context of polycythemia vera (PV), ANA is occasionally employed in clinical practice, although data has not consistently demonstrated a benefit to targeting a platelet goal as a therapeutic endpoint. The aim of the current study was to delineate the patterns of ANA use in PV, and to describe outcomes and toxicities. Within a multi-center cohort of 527 patients with PV, 48 received ANA (9 excluded for absent data). 27 (69.2%) had high-risk PV, 10 (25.6%) had prior thrombosis, and none had extreme thrombocytosis, acquired von Willebrand disease, and/or documented resistance to hydroxyurea. While ANA effectively lowered median platelet count, 43.5% of patients had an unresolved thrombocytosis at time of ANA discontinuation. Treatment-emergent adverse events-including headaches, cardiac palpitations and arrhythmias, nausea, vomiting and/or diarrhea-led to ANA discontinuation in 76.9% of patients. Further, three patients experienced arterial thromboses during a median duration of 27.5 months of ANA therapy. In conclusion, this study highlights ANA's restrictive tolerability profile which, compounded by the absence of clear advantage to strict platelet control in PV, suggests the use of ANA should be limited in this setting.

Treatment and Clinical Endpoints in Polycythemia Vera: Seeking the Best Obtainable Version of the Truth

Polycythemia vera (PV) is a Philadelphia chromosome-negative myeloproliferative neoplasm driven by the JAK2 V617F (or rarely exon 12) mutation. Its natural history can extend over a few decades, and therefore treatment planning is predicated on continual re-assessment of traditional risk features (age, prior thrombosis) to evaluate the need for cytoreduction besides foundational therapy with low-dose aspirin and stringent phlebotomy. Shorter- and longer-term patient goals should be considered in light of several variables such as co-morbid conditions (especially cardiovascular risk factors), disease symptoms, and the risk-benefit profile of available drugs. While hydroxyurea has been the pro forma choice of cytoreduction for many practitioners over the last half-century, the more recent regulatory approvals of ruxolitinib and ropeginterferon-alfa-2b, based on phase 3 randomized trials, highlight an expanding portfolio of active drugs. Obtaining high-level evidence for short-term clinical trial endpoints such as hematocrit control, symptom burden/quality of life, splenomegaly, and JAK2 V617F allele burden lies within the timeline of most studies. However, in many cases, it may not be possible to adequately power trials to capture significant differences in the typically low event rates of thrombosis, as well as longer-horizon endpoints such as evolution to myelofibrosis and acute myeloid leukemia, and survival. This Perspective highlights the challenges of addressing these data gaps and outstanding questions in the emerging treatment landscape of PV.

The MDM2 antagonist idasanutlin in patients with polycythemia vera: results from a single-arm phase 2 study

Idasanutlin, an MDM2 antagonist, showed clinical activity and a rapid reduction in JAK2 V617F allele burden in patients with polycythemia vera (PV) in a phase 1 study. This open-label phase 2 study evaluated idasanutlin in patients with hydroxyurea (HU)-resistant/-intolerant PV, per the European LeukemiaNet criteria, and phlebotomy dependence; prior ruxolitinib exposure was permitted. Idasanutlin was administered once daily on days 1 through 5 of each 28-day cycle. The primary end point was composite response (hematocrit control and spleen volume reduction > 35%) in patients with splenomegaly and hematocrit control in patients without splenomegaly at week 32. Key secondary end points included safety, complete hematologic response (CHR), patient-reported outcomes, and molecular responses. All patients (n = 27) received idasanutlin; 16 had response assessment (week 32). Among responders with baseline splenomegaly (n = 13), 9 (69%) attained any spleen volume reduction, and 1 achieved composite response. Nine patients (56%) achieved hematocrit control, and 8 patients (50%) achieved CHR. Overall, 43% of evaluable patients (6/14) showed a ≥50% reduction in the Myeloproliferative Neoplasm Symptom Assessment Form Total Symptom Score (week 32). Nausea (93%), diarrhea (78%), and vomiting (41%) were the most common adverse events, with grade ≥ 3 nausea or vomiting experienced by 3 patients (11%) and 1 patient (4%), respectively. Reduced JAK2 V617F allele burden occurred early (after 3 cycles), with a median reduction of 76%, and was associated with achieving CHR and hematocrit control. Overall, the idasanutlin dosing regimen showed clinical activity and rapidly reduced JAK2 allele burden in patients with HU-resistant/- intolerant PV but was associated with low-grade gastrointestinal toxicity, leading to poor long-term tolerability. This trial was registered at www.clinincaltrials.gov as #NCT03287245.

Neutrophil-to-lymphocyte ratio is a novel predictor of venous thrombosis in polycythemia vera

We investigated the neutrophil-to-lymphocyte ratio (NLR) as a predictor of thrombosis in polycythemia vera (PV). After a median follow-up of 2.51 years, of 1508 PV patients enrolled in the ECLAP study, 82 and 84 developed arterial and venous thrombosis, respectively. Absolute counts of total leukocytes, neutrophils, lymphocytes, platelets, and the NLR were tested by generalized additive models (GAM) to evaluate their trend in continuous scale of thrombotic risk. Only for venous thrombosis, we showed that baseline absolute neutrophil and lymphocyte counts were on average respectively higher (median: 6.8 × 10⁹/L, p = 0.002) and lower (median: 1.4 × 10⁹/L, p = 0.001), leading to increased NLR values (median: 5.1, p = 0.002). In multivariate analysis, the risk of venous thrombosis was independently associated with previous venous events (HR = 5.48, p ≤ 0.001) and NLR values ≥5 (HR = 2.13, p = 0.001). Moreover, the relative risk in both low- and high-standard risk groups was almost doubled in the presence of NLR ≥ 5. These findings were validated in two Italian independent external cohorts (Florence, n = 282 and Rome, n = 175) of contemporary PV patients. Our data support recent experimental work that venous thrombosis is controlled by innate immune cells and highlight that NLR is an inexpensive and easily accessible prognostic biomarker of venous thrombosis.

Advances in polycythemia vera and lessons for acute leukemia

The myeloproliferative neoplasms (MPN), polycythemia vera (PV), essential thrombocytosis and primary myelofibrosis, are an unusual group of myeloid neoplasms, which arise in a pluripotent hematopoietic stem cell (HSC) due to gain of function driver mutations in the JAK2, CALR and MPL genes that constitutively activate JAK2, the cognate tyrosine kinase of the type 1 hematopoietic growth factor (HGF) receptors. PV is the ultimate phenotypic expression of constitutive JAK2 activation since it alone of the three MPN is characterized by overproduction of normal red cells, white cells and platelets. Paradoxically, however, although PV is a panmyelopathy involving myeloid, erythroid and megakaryocytic progenitor cells, pluripotent HSC only express a single type of HGF receptor, the thrombopoietin receptor, MPL. In this review, the basis for how a pluripotent HSC with one type of HGF can give rise to three separate types of myeloid cells will be explained and it will be demonstrated that PV is actually a hormone-sensitive disorder, characterized by elevated thrombopoietin levels. Finally, it will be shown that the most common form of acute leukemia in PV is due to the inappropriate use of chemotherapy, including hydroxyurea, which facilitates expansion of DNA-damaged, mutated HSC at the expense of their normal counterparts.

Polycythemia vera: historical oversights, diagnostic details, and therapeutic views

Polycythemia vera (PV) is a relatively indolent myeloid neoplasm with median survival that exceeds 35 years in young patients, but its natural history might be interrupted by thrombotic, fibrotic, or leukemic events, with respective 20-year rates of 26%, 16%, and 4%. Current treatment strategies in PV have not been shown to prolong survival or lessen the risk of leukemic or fibrotic progression and instead are directed at preventing thrombotic complications. In the latter regard, two risk categories are considered: high (age >60 years or thrombosis history) and low (absence of both risk factors). All patients require phlebotomy to keep hematocrit below 45% and once-daily low-dose aspirin, in the absence of contraindications. Cytoreductive therapy is recommended for high-risk or symptomatic low-risk disease; our first-line drug of choice in this regard is hydroxyurea but we consider pegylated interferon as an alternative in certain situations, including in young women of reproductive age, in patients manifesting intolerance or resistance to hydroxyurea therapy, and in situations where treatment is indicated for curbing phlebotomy requirement rather than preventing thrombosis. Additional treatment options include busulfan and ruxolitinib; the former is preferred in older patients and the latter in the presence of symptoms reminiscent of post-PV myelofibrosis or protracted pruritus. Our drug choices reflect our appreciation for long-term track record of safety, evidence for reduction of thrombosis risk, and broader suppression of myeloproliferation. Controlled studies are needed to clarify the added value of twice- vs once-daily aspirin dosing and direct oral anticoagulants. In this invited review, we discuss our current approach to diagnosis, prognostication, and treatment of PV in general, as well as during specific situations, including pregnancy and splanchnic vein thrombosis.

Hematocrit to hemoglobin ratio as a prognostic marker in polycythemia vera

BACKGROUND

The hematocrit to hemoglobin ratio (HHR) is frequently used in everyday practice to measure hemoconcentration; however, clinical associations of HHR in the context of polycythemia vera (PV) have not been investigated so far.

PATIENTS AND METHODS

We retrospectively assessed HHR at the time of diagnosis in 107 PV and 40 secondary polycythemia (SP) patients from three community hospitals.

RESULTS

Median HHR was higher in PV than in SP patients (3.131 vs. 2.975, p = 0.041). Among PV patients, higher HHR correlated with splenomegaly, higher total leukocyte and absolute granulocyte counts, higher red blood cell counts, lower hemoglobin, higher red blood cell distribution width, lower mean corpuscular hemoglobin and lower ferritin levels, whereas in SP patients higher HHR correlated with older age, female sex and lower hemoglobin (p < 0.050 for all analyses). Using the receiver operating curve analysis-defined cut-off points, higher HHR in PV was associated with a shorter time to thrombosis (hazard ratio-HR 5.20, p = 0.022) independently of high-risk disease status (HR 4.48, p = 0.034) and shorter overall survival (HR 6.69, p = 0.009) independently of leukocytosis (HR 4.48, P = 0.034) and the absence of aspirin use (HR 15.53, p < 0.001).

CONCLUSION

Higher HHR may represent iron deficiency and a stronger clonal myeloproliferation in PV and could provide additional prognostic information to the classical risk assessment.

Kidney Dysfunction Is Associated with Thrombosis and Disease Severity in Myeloproliferative Neoplasms: Implications from the German Study Group for MPN Bioregistry

Simple Summary

In patients with myeloproliferative neoplasms (MPN) and in patients with kidney dysfunction, a higher rate of thrombosis has been reported compared with the general population. Furthermore, MPN patients are more prone to develop kidney dysfunction. In our study, we assessed the importance of specific risk factors for kidney dysfunction and thrombosis in MPN patients. We found that the rate of thrombosis is correlated with the degree of kidney dysfunction, especially in myelofibrosis. Significant associations for kidney dysfunction included arterial hypertension, MPN treatment, and increased inflammation, and those for thrombosis comprised arterial hypertension, non-excessive platelet counts, and antithrombotic therapy. The identified risk factor associations varied between MPN subtypes. Our data suggest that kidney dysfunction in MPN patients is associated with an increased risk of thrombosis, mandating closer monitoring, and, possibly, early thromboprophylaxis.

Abstract

Inflammation-induced thrombosis represents a severe complication in patients with myeloproliferative neoplasms (MPN) and in those with kidney dysfunction. Overlapping disease-specific attributes suggest common mechanisms involved in MPN pathogenesis, kidney dysfunction, and thrombosis. Data from 1420 patients with essential thrombocythemia (ET, 33.7%), polycythemia vera (PV, 38.5%), and myelofibrosis (MF, 27.9%) were extracted from the bioregistry of the German Study Group for MPN. The total cohort was subdivided according to the calculated estimated glomerular filtration rate (eGFR, (mL/min/1.73 m²)) into eGFR1 (≥90, 21%), eGFR2 (60–89, 56%), and eGFR3 (<60, 22%). A total of 29% of the patients had a history of thrombosis. A higher rate of thrombosis and longer MPN duration was observed in eGFR3 than in eGFR2 and eGFR1. Kidney dysfunction occurred earlier in ET than in PV or MF. Multiple logistic regression analysis identified arterial hypertension, MPN treatment, increased uric acid, and lactate dehydrogenase levels as risk factors for kidney dysfunction in MPN patients. Risk factors for thrombosis included arterial hypertension, non-excessive platelet counts, and antithrombotic therapy. The risk factors for kidney dysfunction and thrombosis varied between MPN subtypes. Physicians should be aware of the increased risk for kidney disease in MPN patients, which warrants closer monitoring and, possibly, early thromboprophylaxis.

Improving the investigative approach to polycythaemia vera: a critical assessment of current evidence and vision for the future

Polycythaemia vera is a challenging disease to study given its low prevalence and prolonged time-to-event for important clinical endpoints such as thrombosis, progression, and mortality. Although researchers in this space often rise to meet these challenges, there is considerable room for improvement in the analysis of retrospective data, the development of risk-stratification tools, and the design of randomised controlled trials. In this Viewpoint, we review the evidence behind the contemporary approach to risk stratification and treatment of polycythaemia vera. Frameworks for using data more efficiently, constructing more nuanced prognostic models, and overcoming challenges in clinical trial design are discussed.

Clinical insights into the origins of thrombosis in myeloproliferative neoplasms

Philadelphia chromosome-negative myeloproliferative neoplasms (MPNs), polycythemia vera, essential thrombocythemia, and primary myelofibrosis, are hematopoietic stem cell disorders that are defined by activating mutations in signal transduction pathways and are characterized clinically by the overproduction of platelets, red blood cells, and neutrophils, significant burden of disease-specific symptoms, and high rates of vascular events. The focus of this review is to critically reevaluate the clinical burden of thrombosis in MPNs, to review the clinical associations among clonal hematopoiesis, JAK2V617F burden, inflammation, and thrombosis, and to provide insights into novel primary and secondary thrombosis-prevention strategies.

Stepping out of antiquity: An update on emerging drugs for the treatment of polycythemia vera

Introduction: Polycythemia vera is a chronic hematologic malignancy frequently presented with constitutional symptoms and associated with an increased risk of thrombosis, hemorrhage, and progression to myelofibrosis or acute myeloid leukemia. Current treatment strategies reduce thrombohemorrhagic risk by controlling blood counts and inhibiting platelets, but often fail to address disease-related symptoms or biologically modify the disease.Areas covered: We review the current paradigm for treating polycythemia vera, highlight areas of unmet need, review therapeutic agents in late stage clinical development, and provide an overarching view of how these emerging agent may fit into the future armamentarium of polycythemia vera treatments.Expert opinion: The shift from focusing solely on secondary prevention of thrombohemorrhagic events to a comprehensive treatment strategy that additionally aims to improve quality of life and prevent disease progression has resulted in a rapidly evolving therapeutic landscape that promises to move the treatment of polycythemia vera out of antiquity into the modern age.

Interferon alpha therapy in essential thrombocythemia and polycythemia vera-a systematic review and meta-analysis

Data on the efficacy and safety of interferon (IFN)-α for the treatment of essential thrombocythemia (ET) and polycythemia vera (PV) are inconsistent. We conducted a systematic review and meta-analysis and searched MEDLINE and EMBASE via Ovid, Scopus, COCHRANE registry of clinical trials, and Web of Science from inception through 03/2019 for studies of pegylated IFN (peg-IFN) and non-pegylated IFN (non-peg-IFN) in PV and ET patients. Random-effects models were used to pool response rates for the primary outcome of overall response rate (ORR) defined as a composite of complete response, partial response, complete hematologic response (CHR) and partial hematologic response. Peg-IFN and non-peg-IFN were compared by meta-regression analyses. In total, 44 studies with 1359 patients (730 ET, 629 PV) were included. ORR were 80.6% (95% confidence interval: 76.6-84.1%, CHR: 59.0% [51.5%-66.1%]) and 76.7% (67.4-84.0%; CHR: 48.5% [37.8-59.4%]) for ET and PV patients, respectively. In meta-regression analyses results did not differ significantly for non-peg-IFN vs. peg-IFN. Annualized rates of thromboembolic complications and treatment discontinuation due to adverse events were low at 1.2% and 8.8% for ET and 0.5% and 6.5% for PV patients, respectively. Both peg-IFN and non-peg-IFN can be effective and safe long-term treatments for ET and PV.

Ruxolitinib discontinuation in polycythemia vera: Patient characteristics, outcomes, and salvage strategies from a large multi-institutional database

Ruxolitinib is approved for the treatment of patients with polycythemia vera (PV) who are intolerant or resistant to hydroxyurea. While ruxolitinib discontinuation in myelofibrosis is associated with dismal outcomes, the analogous experience in PV has not been reported. Using a large, multi-institutional database of PV patients, we identified 93 patients with PV who were treated with ruxolitinib, of whom 22 discontinued therapy. Adverse events were the primary reason for discontinuation. After a median follow-up of 18.2 months following ruxolitinib discontinuation, no patients experienced a thrombotic event. One patient died 20.8 months after discontinuation. As compared with the 71 patients who were still receiving treatment with ruxolitinib at last follow up, patients who discontinued ruxolitinib were older at time of treatment initiation (67.5 versus 64.8 years, p = 0.0058), but had similar patient and disease characteristics. After discontinuation, only 4 patients (18 %) received subsequent cytoreductive therapy, including hydroxyurea in one patient and pegylated interferon α-2a in three patients. In stark contrast to the experience in myelofibrosis, discontinuation of ruxolitinib in PV was associated with generally favorable outcomes. However, there is a lack of available salvage therapies, highlighting the need for further therapeutic development in PV.

The pathobiology of thrombosis, microvascular disease, and hemorrhage in the myeloproliferative neoplasms

Thrombotic, vascular, and bleeding complications are the most common causes of morbidity and mortality in the Philadelphia chromosome-negative myeloproliferative neoplasms (MPNs). In these disorders, circulating red cells, leukocytes, and platelets, as well as some vascular endothelial cells, each have abnormalities that are cell-intrinsic to the MPN driver mutations they harbor (eg, JAK2 V617F). When these cells are activated in the MPNs, their interactions with each other create a highly proadhesive and prothrombotic milieu in the circulation that predisposes patients with MPN to venous, arterial, and microvascular thrombosis and occlusive disease. Bleeding problems in the MPNs are caused by the MPN blood cell-initiated development of acquired von Willebrand disease. The inflammatory state created by MPN stem cells in their microenvironment extends systemically to amplify the clinical thrombotic tendency and, at the same time, preferentially promote further MPN stem cell clonal expansion, thereby generating a vicious cycle that favors a prothrombotic state in these diseases.

Pathogenesis of cardiovascular events in BCR-ABL1-negative myeloproliferative neoplasms

Thrombosis, both in arterial and venous territories, is the major complication of myeloproliferative neoplasms and is responsible for a high rate of morbidity and mortality. The currently accepted risk factors are an age over 60 years and a history of thrombosis. However, many complex mechanisms contribute to this increased prothrombotic risk, with involvement of all blood cell types, plasmatic factors, and endothelial cells. Besides, some cardiovascular events may originate from arterial vasospasm that could contribute to thrombotic complications. In this review, we discuss recent results obtained in mouse models in the light of data obtained from clinical studies. We emphasize on actors of thrombosis that are currently not targeted with current therapeutics but could be promising targets, i.e, neutrophil extracellular traps and vascular reactivity.

Thrombotic, Vascular, and Bleeding Complications of the Myeloproliferative Neoplasms

Thrombotic, vascular, and bleeding complications are the most frequent causes of morbidity and mortality in myeloproliferative neoplasms (MPNs). The interplay and reciprocal amplification between two factors are considered to lead to thrombosis in MPNs: (1) circulating blood cell-intrinsic abnormalities caused by an MPN driver mutation in their hematopoietic progenitor/stem cells, interacting with vascular endothelial cells, show prothrombotic and proadhesive phenotypes; and (2) a state of usually subclinical systemic inflammation that fuels the thrombotic tendency. Prevention and treatment require maintenance of hematocrit less than 45% and cytoreductive therapy in patients with a high risk for thrombotic and vascular complications.

Prevention of recurrent thromboembolism in myeloproliferative neoplasms: review of literature and focus on direct oral anticoagulants

Myeloproliferative neoplasms (MPNs), including polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (MF) are stem cell clonal neoplasms characterized by expansion of late myeloid cells. Thrombosis risk is elevated in MPNs and contributes significantly to morbidity and mortality. Current consensus guidelines make no specific recommendations regarding anticoagulant choice for the treatment of venous thromboembolism (VTE) in MPNs, with most evidence supporting the use of vitamin K antagonists (VKAs) for secondary prophylaxis. However, direct oral anticoagulants (DOACs) are now increasingly being used, although with limited data on safety and efficacy in MPNs specifically. The widespread adoption of DOACs is based on new, high-quality evidence demonstrating safety and efficacy of DOAC treatment for cancer-associated VTE. However, these studies include few if any MPN patients, and MPNs have disease-specific considerations that may elevate thrombosis and bleeding risk. The purpose of this review is to discuss evidence behind current treatment recommendations for thrombosis in MPNs, with special attention to the use of DOACs.

Emerging Role of Neutrophils in the Thrombosis of Chronic Myeloproliferative Neoplasms

Thrombosis is a major cause of morbimortality in patients with chronic Philadelphia chromosome-negative myeloproliferative neoplasms (MPN). In the last decade, multiple lines of evidence support the role of leukocytes in thrombosis of MPN patients. Besides the increase in the number of cells, neutrophils and monocytes of MPN patients show a pro-coagulant activated phenotype. Once activated, neutrophils release structures composed of DNA, histones, and granular proteins, called extracellular neutrophil traps (NETs), which in addition to killing pathogens, provide an ideal matrix for platelet activation and coagulation mechanisms. Herein, we review the published literature related to the involvement of NETs in the pathogenesis of thrombosis in the setting of MPN; the effect that cytoreductive therapies and JAK inhibitors can have on markers of NETosis, and, finally, the novel therapeutic strategies targeting NETs to reduce the thrombotic complications in these patients.

Ropeginterferon alfa-2b versus phlebotomy in low-risk patients with polycythaemia vera (Low-PV study): a multicentre, randomised phase 2 trial

BACKGROUND

There is no evidence that phlebotomy alone is sufficient to steadily maintain haematocrit on target level in low-risk patients with polycythaemia vera. This study aimed to compare the efficacy and safety of ropeginterferon alfa-2b on top of the standard phlebotomy regimen with phlebotomy alone.

METHODS

In 2017, we launched the Low-PV study, a multicentre, open-label, two-arm, parallel-group, investigator-initiated, phase 2 randomised trial with a group-sequential adaptive design. The study involved 21 haematological centres across Italy. Participants were recruited in a consecutive order. Participants enrolled in the study were patients, aged 18-60 years, with a diagnosis of polycythaemia vera according to 2008-16 WHO criteria. Eligible patients were randomly allocated (1:1) to receive either phlebotomy and low-dose aspirin (standard group) or ropeginterferon alfa-2b on top of the standard treatment (experimental group). Randomisation sequence was generated using five blocks of variable sizes proportional to elements of Pascal's triangle. Allocation was stratified by age and time from diagnosis. No masking was done. Patients randomly allocated to the standard group were treated with phlebotomy (300 mL for each phlebotomy to maintain the haematocrit values of lower than 45%) and low-dose aspirin (100 mg daily), if not contraindicated. Patients randomly allocated to the experimental group received ropeginterferon alfa-2b subcutaneously every 2 weeks in a fixed dose of 100 μg on top of the phlebotomy-only regimen. The primary endpoint was treatment response, defined as maintenance of the median haematocrit values of 45% or lower without progressive disease during a 12-month period. Analyses were done by intention-to-treat principle. The study was powered assuming a higher percentage of responders in the experimental group (75%) than in the standard group (50%). Here we report results from the second planned interim analysis when 50 patients had been recruited to each group. The trial is ongoing, and registered with ClinicalTrials.gov, NCT03003325.

FINDINGS

Between Feb 2, 2017, and March 13, 2020, 146 patients were screened, and 127 patients were randomly assigned to the standard group (n=63) or the experimental group (n=64). The median follow-up period was 12·1 months (IQR 12·0-12·6). For the second pre-planned interim analysis, a higher response rate in the experimental group was seen (42 [84%] of 50 patients) than in the standard group (30 [60%] of 50 patients; absolute difference 24%, 95% CI 7-41%, p=0·0075). The observed z value (2·6001) crossed the critical bound of efficacy (2·5262), and the stagewise adjusted p value early showed superiority of experimental treatment. Thus, the data safety monitoring board decided to stop patient accrual for overwhelming efficacy and to continue the follow-up, as per protocol, for 2 years. Under the safety profile, no statistically significant difference between groups in frequency of adverse events of grade 3 or higher was observed; the most frequently reported adverse events were neutropenia (four [8%] of 50 patients) in the experimental group and skin symptoms (two [4%] of 50 patients) in the standard group. No grade 4 or 5 adverse events occurred.

INTERPRETATION

Supplementing phlebotomy with ropeginterferon alfa-2b seems to be safe and effective in steadily maintaining haematocrit values on target in low-risk patients with polycythaemia vera. Findings from the current study might have implications for changing the current management of low-risk patients with polycythaemia vera.

FUNDING

AOP Orphan Pharmaceuticals, Associazione Italiana per la Ricerca sul Cancro.

Novel and combination therapies for polycythemia vera and essential thrombocythemia: the dawn of a new era

INTRODUCTION

Essential thrombocythemia (ET) and polycythemia vera (PV) belong to the BCR-ABL1-negative myeloproliferative neoplasms and are characterized by the clonal proliferation of hematopoietic stem and progenitor cells. The contribution of aberrant immune regulation within the bone marrow microenvironment to ET and PV pathogenesis as well as the underlying molecular landscape is becoming increasingly understood.

AREAS COVERED

Authors searched PubMed and conference abstracts in August 2020 for preclinical and clinical studies to provide an overview of the immune pathobiology in ET and PV and the rationale for several novel agents. A discussion of recent clinical trials on interferon and ruxolitinib in ET and PV patients is provided followed by an outline of the future challenges in the field particularly for novel therapeutics and an increasingly individualized, molecularly driven approach to treatment selection. Several novel agents are currently being actively evaluated and are reviewed herein as well.

EXPERT OPINION

While hydroxyurea remains the first-line treatment for cytoreduction in most high-risk ET and PV patients, the disease-modifying potential of IFN is promising and could make it a preferred option for selected patients. Advances in molecular testing will enable a more individualized approach to prognostication and treatment selection.