Biological drivers of clinical phenotype in myelofibrosis

Emerging Therapeutic Approaches for Anemia in Myelofibrosis

PURPOSE OF REVIEW

In this review, we highlight conventional agents and novel emerging therapeutic strategies to treat anemia in MF.

RECENT FINDINGS

Anemia is a common and challenging feature of myelofibrosis (MF). The pathobiology of anemia is multifactorial, including progressive bone marrow fibrosis, decreased erythropoiesis due to high hepcidin levels leading to iron sequestration in the reticuloendothelial system, hypersplenism, erythropoiesis inhibition by myelosuppressive JAK inhibitors (ruxolitinib, fedratinib), and others. MF-associated anemia has a negative impact on survival. Conventional agents to manage anemia include erythropoiesis-stimulating agents, danazol, corticosteroids, and immunomodulatory agents, but responses are infrequent and lack durability. Notable advancements have emerged in developing novel treatments for anemia in MF, including the regulatory approval of momelotinib (ACVR1/JAK1/2 inhibitor) in 2023 and development of novel promising agents targeting hemojuvelin and activins. Momelotinib and pacritinib (ACVR1/JAK2 inhibitor) are the preferred JAK inhibitors for patients with cytopenias (anemia, thrombocytopenia). Luspatercept and elritercept are activin receptor ligand traps, promoting erythroid maturation and late-stage erythropoiesis. Currently, luspatercept is being evaluated in a phase 3 trial (INDEPENDENCE™) for anemia in MF patients who are on a JAK2 inhibitor and require transfusions, and in a phase 2 trial (ODYSSEY) in combination with momelotinib in MF patients who are transfusion dependent, whether or not on a JAK inhibitor. Interim results of the RESTORE trial demonstrated that elritercept significantly decreased transfusions in MF patients. DISC-0974 is a first-in-class anti-hemojuvelin (positive hepcidin regulator) monoclonal antibody that decreased hepcidin expression, increased serum iron, and enhanced erythropoiesis in anemic patients with MF in a phase 1b/2 study. Burgeoning studies of novel anemia-targeted agents and combinations are significantly improving the quality of life and outcomes of patients with MF. The recent approval of momelotinib to treat MF with anemia and the emerging novel anemia-directed strategies in early and advanced clinical development have ushered in a new era in the treatment of MF-related anemia.

SOHO State of the Art Updates and Next Questions | Updates on Myelofibrosis With Cytopenia

Myelofibrosis (MF) is a rare hematologic malignancy that is characterized by dysregulation of the JAK-STAT pathway resulting in fibrosis of the bone marrow, splenomegaly, and abnormalities in peripheral blood counts including anemia, leukocytosis, and thrombocytopenia. This disease has 2 phenotypic extremes - myeloproliferative and cytopenic. Cytopenic myelofibrosis presents with pronounced cytopenia and a different landscape of genetic mutations which results in worse clinical outcomes and a poor prognosis. Patients with cytopenic MF are at high risk of developing various complications like bleeding, infections, and transfusion dependency. Historically, the only Federal Drug Administration (FDA) approved therapy was ruxolitinib, a JAK1/2 inhibitor, which improved constitutional symptoms and splenomegaly, however, exacerbated anemia and thrombocytopenia.1,2 There were very few options for patients with anemia and thrombocytopenia, and supportive treatments for these problems lack efficacy. Fortunately, there are newer treatment options which may allow for treatment of the symptoms and splenomegaly in the setting of cytopenias and even improve cytopenias. This up-to-date review not only highlights the prevalent options in therapeutic marketplace, but also sheds light on the significant unmet need of addressing anemia and thrombocytopenia in cytopenic MF.

How I individualize selection of JAK inhibitors for patients with myelofibrosis

ABSTRACT

The advent of Janus kinase inhibitors (JAKis) inaugurated a novel era in the treatment of myelofibrosis (MF), a myeloproliferative neoplasm with heterogeneous clinical manifestations. Four JAKis have been approved for intermediate or high-risk MF, in the United States. Regulatory approval of the first JAK1/2 inhibitor, ruxolitinib, in 2011, transformed the landscape of MF by markedly controlling splenomegaly and constitutional symptoms, improving patients' quality of life, and prolonging survival. Fedratinib, the second approved JAKi, is preferred in the second-line setting. Ruxolitinib and fedratinib can cause myelosuppression and are recommended for patients with the myeloproliferative phenotype. The approval of 2 less-myelosuppressive JAKis, pacritinib and momelotinib, provided essential treatment options for patients with severe thrombocytopenia and anemia, respectively. Momelotinib and pacritinib are potent activin A receptor, type 1 inhibitors with consequent significant benefits for patients with anemia. Transfusion independence was achieved with momelotinib in patients who were severely anemic, and the association of transfusion independence with prolonged overall survival was demonstrated. Judicious treatment decisions regarding JAKis can be made with in-depth understanding of the pivotal clinical trials that evaluated JAKis and their therapeutic attributes and should be guided by the dominant clinical manifestations and the type/degree of cytopenia(s) (myeloproliferative/cytopenic phenotypes). This article reviews our clinical approach to treatment with JAKis and their sequencing in patients with MF by presenting 3 clinical vignettes.

Selinexor plus ruxolitinib in JAK inhibitor treatment-naïve myelofibrosis: SENTRY Phase 3 study design

Selinexor is an investigational, selective oral XPO1 inhibitor that may inhibit myelofibrosis (MF)-relevant JAK/STAT and non-JAK/STAT pathways with potential synergy with ruxolitinib. SENTRY (XPORT-MF-034; NCT04562389) is a Phase 1/3 study evaluating safety and efficacy of selinexor plus ruxolitinib for treatment of patients with JAK inhibitor (JAKi) treatment-naïve MF. The Phase 1 open label portion of the study included a 3 + 3 dose escalation and dose expansion, with no dose limiting toxicities observed. Described here is the Phase 3 randomized, double-blind, placebo-controlled study designed to evaluate selinexor+ruxolitinib versus placebo+ruxolitinib in patients with JAKi treatment-naïve MF. Approximately 350 patients will be enrolled. Primary endpoints will evaluate spleen volume reduction ≥ 35% and absolute mean change in total symptom score from baseline to week 24.Clinical Trial Registration: NCT04562389 (ClinicalTrials.Gov).

Clearance of Driver Mutations after Transplantation for Myelofibrosis

BACKGROUND

Allogeneic hematopoietic stem-cell transplantation is the only curative treatment for myelofibrosis. Driver mutations are the pathophysiological hallmark of the disease, but the role of mutation clearance after transplantation is unclear.

METHODS

We used highly sensitive polymerase-chain-reaction technology to analyze the dynamics of driver mutations in peripheral-blood samples from 324 patients with myelofibrosis (73% with JAK2 mutations, 23% with CALR mutations, and 4% with MPL mutations) who were undergoing transplantation after reduced-intensity conditioning. Mutations were detected before transplantation and at 30, 100, and 180 days after transplantation to measure clearance and its effect on relapse and cure. The two primary end points were relapse and disease-free survival.

RESULTS

At day 30 after transplantation, mutation clearance was found in 42% of the patients who had JAK2 mutations, 73% of those who had CALR mutations, and 54% of those who had MPL mutations; the corresponding percentages at day 100 were 63%, 82%, and 100%. The cumulative incidence of relapse at 1 year was 6% (95% confidence interval [CI], 2 to 10) among patients with mutation clearance at day 30 after transplantation and 21% (95% CI, 15 to 27) among those without mutation clearance at day 30. Disease-free and overall survival at 6 years were 61% and 74%, respectively, among patients with mutation clearance at day 30 after transplantation and 41% and 60%, respectively, among those without mutation clearance at day 30. Mutation clearance at day 30 appeared to outperform traditional donor chimerism as a measure of response; it was independently associated with a reduced risk of relapse or progression (hazard ratio, 0.36; 95% CI, 0.21 to 0.61) and appeared to overcome differences in prognosis based on the type of driver mutation (JAK2 vs. MPL or CALR).

CONCLUSIONS

In patients with myelofibrosis, clearance of driver mutations at day 30 after transplantation appeared to influence relapse and survival, irrespective of the underlying driver mutation.

18F-FDG PET/CT findings in a mucosa-associated lymphoid tissue lymphoma patient coexisting with primary myelofibrosis

A 61-year-old male presented with hematemesis and melena. Biopsy and immunohistochemistry confirmed mucosa-associated lymphoid tissue (MALT) lymphoma in the posterior wall of the gastric antrum, prompting further evaluation with 18F-fluorodeoxyglucose (18F-FDG) positron emission tomography/computed tomography (PET/CT). In addition to elevated uptake in the gastric antrum, 18F-FDG PET/CT showed diffuse uptake in multiple bone marrow, initially suspected to indicate bone marrow involvement by lymphoma. Further examination identified it as primary myelofibrosis (PMF). Following concurrent therapies, 18F-FDG PET/CT demonstrated negative uptake in gastric antrum, indicating complete remission of the lymphoma, while the elevated bone marrow uptake suggested progression of PMF. The coexistence of MALT lymphoma and PMF is very rare. This case highlights the image characteristics and potential diagnostic and therapeutic monitoring value of 18F-FDG PET/CT in patients with concurrent MALT lymphoma and PMF.

Pacritinib prevents inflammation-driven myelofibrosis-like phenotype in a miR-146a-/- murine model

Chronic proinflammatory signaling is a characteristic trait in myeloproliferative neoplasms (MPN), particularly myelofibrosis (MF). Aberrant inflammatory signaling, particularly from NF-κB pathway, exacerbates the progression of MPN. Previously, we identified a critical role of miR-146a, a negative regulator of the TLR/NF-κB axis, in MF development. MPN patients carrying the miR-146a rs2431697-TT genotype, associated with lower miR-146a expression levels, have a higher risk of progression to overt-MF from chronic-phase disease. Using miR-146a-/- (KO) mice, a MF-like model lacking MPN driver mutations, we here investigate whether pacritinib, a dual JAK/NF-κB pathways inhibitor (via JAK2/IRAK1, respectively), prevents the age-associated myelofibrotic phenotype of these mice. Young miR-146a-/- mice were treated either with or without pacritinib, for 3 or 6 months. Notably, pacritinib prevented the splenomegaly, reticulin fibrosis and osteosclerosis observed in untreated KO mice. Pacritinib also avoided the myeloproliferation, loss of splenic architecture, and extramedullary hematopoiesis observed in age-matched untreated KO mice. Pharmacological targeting of IRAK1/JAK2 attenuated the pro-inflammatory environment, preventing the increase of inflammatory cytokines, particularly CXCL1 and TNF-α, without inducing cytopenias but rather the opposite. Compared to age-matched untreated KO mice, treated mice showed higher platelet counts irrespective of treatment duration, and higher erythrocyte counts with the longer treatment. Additionally, pacritinib preventive treatment reduced COL1A1 production in an in vitro model mimicking JAK2-driven fibrosis. These findings highlight that dual inhibition of JAK2/IRAK1 with pacritinib, by delaying or attenuating the myelofibrotic progression, could be a potential modifier of the natural course of MPN.

Genetic and immunologic features associated with thrombocytopenia progression and poor prognosis in patients with myelofibrosis

Introduction

Myelofibrosis, which includes primary myelofibrosis (PMF) and secondary myelofibrosis (SMF), can exhibit cytopenic features associated with poor outcomes; however, the underlying mechanisms are unclear. Moreover, characterized by its aggressive nature and limited therapeutic options, myelofibrosis poses a major clinical challenge in hematology. Therefore, in this study, we aimed to identify genetic and immunologic features associated with thrombocytopenia progression and poor prognosis.

Methods

The study involved 226 patients with PMF or SMF, who were categorized into three groups: platelet count ≥ 100 × 109/L (PLT ≥ 100 group; n = 131), progression to thrombocytopenia (PROG group; n = 64), and platelet count < 100 × 109/L (PLT < 100 group; n = 31).

Results

Survival analysis revealed 4-year overall survival rate of 57.7%, 89.4%, and 93.9% for the PLT < 100, PROG, and PLT ≥ 100 groups, respectively. Time-dependent covariate analysis of the PLT ≥ 100 and PROG groups revealed inferior overall survival rate of the PROG group. Multivariate analysis indicated that progression to thrombocytopenia and ASXL1 and IDH1 mutations were associated with poor overall survival. Flow cytometry revealed fewer CD45RA+CD4+ T cells in the PROG group than in the PLT ≥ 100 group. ASXL1 mutations were more prevalent in the PROG group than in the other groups, correlating with a reduced number of CD45RA+CD4+ T cells.

Discussion

ASXL1 mutation and low CD45RA+CD4+ T-cell counts correlated with progression to thrombocytopenia. Our findings underscore the clinical significance of thrombocytopenia dynamics in MF progression and prognosis, with implications for patient management and therapeutic interventions.

Consistency of Spleen and Symptom Reduction Regardless of Cytopenia in Patients With Myelofibrosis Treated With Pacritinib

BACKGROUND

Pacritinib is a JAK2/IRAK1/ACVR1 inhibitor that is approved in the United States for the treatment of patients with myelofibrosis who have a platelet count < 50 × 109/L. Phase 3 clinical studies of pacritinib included patients across a wide range of baseline platelet and hemoglobin levels.

PATIENTS AND METHODS

In order to assess the impact of baseline blood counts on pacritinib efficacy, an analysis of efficacy outcomes by baseline platelet and hemoglobin levels was performed using data pooled from 2 Phase 3 studies of pacritinib in patients with MF (PERSIST-1 and PERSIST-2).

RESULTS

Of 276 patients evaluable for spleen response, spleen volume reduction occurred consistently across platelet subgroups (< 100 × 109/L or ≥ 100 × 109/L) and hemoglobin subgroups (< 8 g/dL, ≥ 8 to < 10 g/dL, or > 10 g/dL), with no diminution in treatment effect in patients with severe thrombocytopenia or anemia. Among 159 patients evaluable for symptoms response, improvement in total symptom score (TTS) was similar across platelet subgroups. A ≥ 50% improvement of TSS occurred more frequently in patients with baseline hemoglobin < 8 g/dL compared with those with baseline hemoglobin ≥ 8 to < 10 g/dL or > 10 g/dL. Patients with baseline hemoglobin < 8 g/dL also experienced improved hemoglobin sustained over 24 weeks, whereas subgroups with less severe anemia had stable hemoglobin levels over time. Symptom improvement as assessed using the Patient Global Impression of Change instrument was generally consistent across platelet and hemoglobin subgroups.

CONCLUSION

Pacritinib demonstrates consistent efficacy in patients with MF regardless of baseline platelet and hemoglobin counts.

Spatial-transcriptomic profiling: a new lens for understanding myelofibrosis pathophysiology

Myelofibrosis (MF) is a complex myeloproliferative neoplasm characterized by abnormal hematopoietic stem cell proliferation and subsequent bone marrow (BM) fibrosis. First documented in the late 19th century, MF has since been extensively studied to unravel its pathophysiology, clinical phenotypes, and therapeutic interventions. MF can be classified into primary and secondary forms, both driven by mutations in genes such as JAK2, CALR, and MPL, which activate the JAK-STAT signaling pathway. These driver mutations are frequently accompanied by additional non-driver mutations in genes like TET2, SRSF2, and TP53, contributing to disease complexity. The BM microenvironment, consisting of stromal cells, extracellular matrix, and cytokines such as TGF-β and TNF-α, plays a critical role in fibrosis and aberrant hematopoiesis. Clinically, MF manifests with symptoms ranging from anemia, splenomegaly, and fatigue to severe complications such as leukemic transformation. Splenomegaly, caused by extramedullary hematopoiesis, leads to abdominal discomfort and early satiety. Current therapeutic strategies include JAK inhibitors like Ruxolitinib, which target the JAK-STAT pathway, alongside supportive treatments such as blood transfusions, erythropoiesis-stimulating agents and developing combinatorial approaches. Allogeneic hematopoietic stem cell transplantation remains the only curative option, though it is limited to younger, high-risk patients. Recently approved JAK inhibitors, including Fedratinib, Pacritinib, and Momelotinib, have expanded the therapeutic landscape. Spatially Resolved Transcriptomics (SRT) has revolutionized the study of gene expression within the spatial context of tissues, providing unprecedented insights into cellular heterogeneity, spatial gene regulation, and microenvironmental interactions, including stromal-hematopoietic dynamics. SRT enables high-resolution mapping of gene expression in the BM and spleen, revealing molecular signatures, spatial heterogeneity, and pathological niches that drive disease progression. These technologies elucidate the role of the spleen in MF, highlighting its transformation into a site of abnormal hematopoietic activity, fibrotic changes, and immune cell infiltration, functioning as a "tumor surrogate." By profiling diverse cell populations and molecular alterations within the BM and spleen, SRT facilitates a deeper understanding of MF pathophysiology, helping identify novel therapeutic targets and biomarkers. Ultimately, integrating spatial transcriptomics into MF research promises to enhance diagnostic precision and therapeutic innovation, addressing the multifaceted challenges of this disease.

Immune-dysregulation harnessing in myeloid neoplasms

Myeloid malignancies arise in bone marrow microenvironments and shape these microenvironments in favor of malignant development. Immune suppression is one of the most important stages in myeloid leukemia progression. Leukemic clone expansion and immune dysregulation occur simultaneously in bone marrow microenvironments. Complex interactions emerge between normal immune system elements and leukemic clones in the bone marrow. In recent years, researchers have identified several of these pathological interactions. For instance, recent works shows that the secretion of inflammatory cytokines such as tumor necrosis factor-α (TNF-α), from bone marrow stromal cells contributes to immune dysregulation and the selective proliferation of JAK2V617F+ clones in myeloproliferative neoplasms. Moreover, inflammasome activation and sterile inflammation result in inflamed microenvironments and the development of myelodysplastic syndromes. Additional immune dysregulations, such as exhaustion of T and NK cells, an increase in regulatory T cells, and impairments in antigen presentation are common findings in myeloid malignancies. In this review, we discuss the role of altered bone marrow microenvironments in the induction of immune dysregulations that accompany myeloid malignancies. We also consider both current and novel therapeutic strategies to restore normal immune system function in the context of myeloid malignancies.

miR-146a-/- mice model reveals that NF-κB inhibition reverts inflammation-driven myelofibrosis-like phenotype

Emerging evidence shows the crucial role of inflammation (particularly NF-κB pathway) in the development and progression of myelofibrosis (MF), becoming a promising therapeutic target. Furthermore, tailoring treatment with currently available JAK inhibitors (such as ruxolitinib or fedratinib) does not modify the natural history of the disease and has important limitations, including cytopenias. Since recent studies have highlighted the role of miR-146a, a negative regulator of the NF-κB pathway, in the pathogenesis of MF; here we used miR-146a-/- (KO) mice, a MF-like model lacking driver mutations, to investigate whether pharmacological inhibition of JAK/STAT and/or NF-κB pathways may reverse the myelofibrotic phenotype of these mice. Specifically, we tested the JAK1/2 inhibitor, ruxolitinib; the NF-κB inhibitor via IKKα/β, BMS-345541; both inhibitors in combination; or a dual inhibitor of both pathways (JAK2/IRAK1), pacritinib. Although all treatments decreased spleen size and partially recovered its architecture, only NF-κB inhibition, either using BMS-345541 (alone or in combination) or pacritinib, resulted in a reduction of extramedullary hematopoiesis, bone marrow (BM) fibrosis and osteosclerosis, along with an attenuation of the exacerbated inflammatory state (via IL-1β and TNFα). However, although dual inhibitor improved anemia and reversed thrombocytopenia, the combined therapy worsened anemia by inducing BM hypoplasia. Both therapeutic options reduced NF-κB and JAK/STAT signaling in a context of JAK2V617F-driven clonal hematopoiesis. Additionally, combined treatment reduced both COL1A1 and IL-6 production in an in vitro model mimicking JAK2-driven fibrosis. In conclusion, NF-κB inhibition reduces, in vitro and in vivo, disease burden and BM fibrosis, which could provide benefits in myelofibrosis patients.

Recent Advances in IRAK1: Pharmacological and Therapeutic Aspects

Interleukin receptor-associated kinase (IRAK) proteins are pivotal in interleukin-1 and Toll-like receptor-mediated signaling pathways. They play essential roles in innate immunity and inflammation. This review analyzes and discusses the physiological functions of IRAK1 and its associated diseases. IRAK1 is involved in a wide range of diseases such as dry eye, which highlights its potential as a therapeutic target under various conditions. Various IRAK1 inhibitors, including Pacritinib and Rosoxacin, show therapeutic potential against malignancies and inflammatory diseases. The covalent IRAK1 inhibitor JH-X-119-01 shows promise in B-cell lymphomas, emphasizing the significance of covalent bonds in its activity. Additionally, the emergence of selective IRAK1 degraders, such as JNJ-101, provides a novel strategy by targeting the scaffolding function of IRAK1. Thus, the evolving landscape of IRAK1-targeted approaches provides promising avenues for increasingly safe and effective therapeutic interventions for various diseases.

African swine fever virus A137R protein inhibits NF-κB activation via suppression of MyD88 signaling in PK15 and 3D4/21 cells in vitro

African swine fever (ASF) is an infectious disease with high mortality caused by African swine fever virus (ASFV), which poses a great threat to the global swine industry. ASFV has evolved multiple strategies to evade host antiviral innate immunity by perturbing inflammatory responses and interferon production. However, the molecular mechanisms underlying manipulation of inflammatory responses by ASFV proteins are not fully understood. Here, we report that A137R protein of ASFV is a key suppressor of host inflammatory responses. Ectopic expression of ASFV A137R in HEK293T cells significantly inhibited the activation of IL-8 and NF-κB promoters triggered by Sendai virus (SeV), influenza A virus (IAV), or vesicular stomatitis virus (VSV). Accordingly, forced A137R expression caused a significant decrease in the production of several inflammatory cytokines such as IL-8, IL-6 and TNF-α in the cells infected with SeV or IAV. Similar results were obtained from experiments using A137R overexpressing PK15 and 3D4/21 cells infected with SeV or VSV. Furthermore, we observed that A137R impaired the activation of MAPK and NF-κB signaling pathways, as enhanced expression of A137R significantly decreased the phosphorylation of JNK, p38 and p65 respectively upon viral infection (SeV or IAV) and IL-1β treatment. Mechanistically, we found that A137R interacted with MyD88, and dampened MyD88-mediated activation of MAPK and NF-κB signaling. Together, these findings uncover a critical role of A137R in restraining host inflammatory responses, and improve our understanding of complicated mechanisms whereby ASFV evades innate immunity.

Splenic irradiation for myelofibrosis prior to hematopoietic cell transplantation: A global collaborative analysis

Splenomegaly is the clinical hallmark of myelofibrosis. Splenomegaly at the time of allogeneic hematopoietic cell transplantation (HCT) is associated with graft failure and poor graft function. Strategies to reduce spleen size before HCT especially after failure to Janus kinase (JAK) inhibition represent unmet clinical needs in the field. Here, we leveraged a global collaboration to investigate the safety and efficacy of splenic irradiation as part of the HCT platform for patients with myelofibrosis. We included 59 patients, receiving irradiation within a median of 2 weeks (range, 0.9-12 weeks) before HCT. Overall, the median spleen size prior to irradiation was 23 cm (range, 14-35). Splenic irradiation resulted in a significant and rapid spleen size reduction in 97% of patients (57/59), with a median decrease of 5.0 cm (95% confidence interval, 4.1-6.3 cm). The most frequent adverse event was thrombocytopenia, with no correlation between irradiation dose and hematological toxicities. The 3-year overall survival was 62% (95% CI, 48%-76%) and 1-year non-relapse mortality was 26% (95% CI, 14%-38%). Independent predictors for survival were severe thrombocytopenia and anemia before irradiation, transplant-specific risk score, higher-intensity conditioning, and present portal vein thrombosis. When using a propensity score matching adjusted for common confounders, splenic irradiation was associated with significantly reduced relapse (p = .01), showing a 3-year incidence of 12% for splenic irradiation versus 29% for patients with immediate HCT and 38% for patients receiving splenectomy. In conclusion, splenic irradiation immediately before HCT is a reasonable approach in patients experiencing JAK inhibition failure and is associated with a low incidence of relapse.

Evaluation of Absolute Neutrophil, Lymphocyte and Platelet Count and Their Ratios as Predictors of Thrombotic Risk in Patients with Prefibrotic and Overt Myelofibrosis

AIM

To investigate the prognostic contribution of absolute neutrophil (ANC), lymphocyte (ALC), platelet count and their ratios, neutrophil-lymphocyte ratio (NLR) and platelet-lymphocyte ratio (PLR), to thrombotic risk in patients with prefibrotic and overt fibrotic myelofibrosis (MF).

METHODS

We retrospectively analyzed a cohort of 256 patients with prefibrotic (85 patients) and overt fibrotic MF (171 patients) treated in six Croatian hematological centers.

RESULTS

Prefibrotic compared to overt fibrotic MF patients presented with significantly higher ALC, platelet count and PLR, and experienced longer time to thrombosis (TTT). Among prefibrotic patients, ANC > 8.33 × 109/L (HR 13.08, p = 0.036), ALC > 2.58 × 109/L (HR 20.63, p = 0.049) and platelet count > 752 × 109/L (HR 10.5, p = 0.043) remained independently associated with shorter TTT. Among overt fibrotic patients, ANC > 8.8 × 109/L (HR 4.49, p = 0.004), ALC ≤ 1.43 × 109/L (HR 4.15, p = 0.003), platelet count ≤ 385 × 109/L (HR 4.68, p = 0.004) and chronic kidney disease (HR 9.07, p < 0.001) remained independently associated with shorter TTT.

CONCLUSIONS

Prognostic properties of ANC, ALC and platelet count are mutually independent and exceed those of NLR and PLR regarding thrombotic risk stratification. ALC and platelet count associate in opposite directions with thrombotic risk in prefibrotic and overt fibrotic MF patients.

STAT5a and SH2B3 novel mutations display malignancy roles in a triple-negative primary myelofibrosis patient

Primary myelofibrosis (PMF) patients frequently have JAK2 (V617F), CALR (exon 9), or MPL (W515 or exon 10) strong driver gene mutation, which triggers abnormal activation of the JAK2-STATs signaling pathway that plays a complex role in the occurrence of PMF. However, about 10-15% of PMF patients have no above typical mutations in these strong driver genes, known as being "triple-negative", which are associated with poor prognosis. In this paper, we reported a unique secondary acute myeloid leukemia (sAML) case transformed from triple-negative PMF combined with lung cancer and erythroderma occurrence at the same time, which has not been reported so far. Through whole blood exome sequencing, four novel noncanonical mutations were detected in key regulatory genes SH2B3 (Q748 and S710) and STAT5a (C350 and K354). Meanwhile, STAT5a-S710 and SH2B3-K354 noncanonical mutations gained strong malignant biofunction on promoting cell growth and tumorigenesis by accelerating the G1/S transition. In the mechanistic study, these pernicious phenotypes driven by noncanonical mutations might be initial PMF by activating p-STAT5a/c-Myc/CyclinD1 and p-STAT3/p-AKT/p-ERK1/2 signaling axes. Therefore, our study explored the deleterious roles of novel noncanonical mutations in STAT5a and SH2B3, which may serve as susceptibility genes and display the oncogenic biofunction in the progression of PMF to acute myeloid leukemia-M2a (AML-M2a).

Myeloproliferative Neoplasms: Contemporary Review and Molecular Landscape

Myelofibrosis (MF), Myeloproliferative neoplasms (MPNs), and MDS/MPN overlap syndromes have a broad range of clinical presentations and molecular abnormalities, making their diagnosis and classification complex. This paper reviews molecular aberration, epigenetic modifications, chromosomal anomalies, and their interactions with cellular and other immune mechanisms in the manifestations of these disease spectra, clinical features, classification, and treatment modalities. The advent of new-generation sequencing has broadened the understanding of the genetic factors involved. However, while great strides have been made in the pharmacological treatment of these diseases, treatment of advanced disease remains hematopoietic stem cell transplant.

Inflammation and bone marrow fibrosis: novel immunotherapeutic targets

PURPOSE OF REVIEW

Myelofibrosis (MF) is primarily driven by constitutive activation of the Janus kinase/signal transducer of activators of transcription (JAK/STAT) pathway. While JAK inhibitors have shown to alleviate disease symptoms, their disease-modifying effects in MF are limited. The only curative treatment remains allogeneic stem cell transplantation, which can be applied to a minority of patients. As a result, there is a need to explore novel targets in MF to facilitate appropriate drug development and therapeutic pathways.

RECENT FINDINGS

Recent research has focused on identifying novel signals that contribute to the abnormal cross-talk between hematopoietic and stromal cells, which promotes MF and disease progression. Inflammation and immune dysregulation have emerged as key drivers of both the initiation and progression of MF. A growing number of actionable targets has been identified, including cytokines, transcription factors, signalling networks and cell surface-associated molecules. These targets exhibit dysfunctions in malignant and nonmalignant hematopoietic cells, but also in nonhematopoietic cells of the bone marrow. The study of these inflammation-related molecules, in preclinical models and MF patient's samples, is providing novel therapeutic targets.

SUMMARY

The identification of immunotherapeutic targets is expanding the therapeutic landscape of MF. This review provides a summary of the most recent advancements in the study of immunotherapeutic targets in MF.

Pacritinib is a potent ACVR1 inhibitor with significant anemia benefit in patients with myelofibrosis

In patients with cytopenic myelofibrosis, treatment with the JAK2/IRAK1 inhibitor pacritinib was associated with anemia benefit in the phase 3 PERSIST-2 study. The impact of pacritinib on transfusion independence (TI) has not been previously described, nor has the mechanism by which pacritinib improves anemia been elucidated. Because it has been previously postulated that inhibition of activin A receptor, type 1 (ACVR1)/activin receptor-like kinase-2 improves anemia in patients with myelofibrosis via suppression of hepcidin production, we assessed the relative inhibitory potency of pacritinib compared with other JAK2 inhibitors against ACVR1. Pacritinib inhibited ACVR1 with greater potency (half-maximal inhibitory concentration [IC50] = 16.7 nM; Cmax:IC50 = 12.7) than momelotinib (IC50 = 52.5 nM; Cmax:IC50 = 3.2), fedratinib (IC50 = 273 nM; Cmax:IC50 = 1.0), or ruxolitinib (IC50 > 1000; Cmax:IC50 < 0.01). Pacritinib's inhibitory activity against ACVR1 was corroborated via inhibition of downstream SMAD signaling in conjunction with marked suppression of hepcidin production. Among patients on PERSIST-2 who were not transfusion independent at baseline based on Gale criteria, a significantly greater proportion achieved TI on pacritinib compared with those treated on best available therapy (37% vs 7%, P = .001), and significantly more had a ≥50% reduction in transfusion burden (49% vs 9%, P < .0001). These data indicate that the anemia benefit of the JAK2/IRAK1 inhibitor pacritinib may be a function of potent ACVR1 inhibition.

Cross-Study Comparisons of JAK2 Inhibitors in Myelofibrosis: Risks and Recommendations

With multiple Janus Kinase (JAK) inhibitors approved or in late development for myelofibrosis, there is a logical desire in the field for comparative efficacy and safety data among these agents in order to inform treatment selection. However, due to the highly disparate nature of patient populations enrolled in different JAK inhibitor trials, as well as key differences in study design, any cross-study comparative analyses should be undertaken with a high degree of caution. Here, we show how differences in enrolled populations can impact both efficacy and safety conclusions and why quantitative comparisons of outcomes across studies is prone to spurious conclusions. We conclude by offering guidance on how to approach comparative analyses in the absence of direct head-to-head data based on a thorough understanding of how study design impacts outcomes. Ultimately there is enough room in the myelofibrosis treatment landscape for multiple JAK inhibitors, and sequencing of therapies should depend on how each agent was studied and where it showed the most benefit, both in trials and in real-world practice.

Recent advances in therapies for primary myelofibrosis

Primary myelofibrosis (PMF), polycythemia vera (PV) and essential thrombocythemia (ET) form the classical BCR-ABL1-negative myeloproliferative neoplasms (MPNs) that are driven by a constitutive activation of JAK2 signaling. PMF as well as secondary MF (post-ET and post-PV MF) are the most aggressive MPNs. Presently, there is no curative treatment, except allogenic hematopoietic stem cell transplantation. JAK inhibitors, essentially ruxolitinib, are the therapy of reference for intermediate and high-risk MF. However, presently the current JAK inhibitors behave mainly as anti-inflammatory drugs, improving general symptoms and spleen size without major impact on disease progression. A better understanding of the genetics of MF, the biology of its leukemic stem cells (LSCs), the mechanisms of fibrosis and of cytopenia and the role of inflammatory cytokines has led to new approaches with the development of numerous therapeutic agents that target epigenetic regulation, telomerase, apoptosis, cell cycle, cytokines and signaling. Furthermore, the use of a new less toxic form of interferon-α has been revived, as it is presently one of the only molecules that targets the mutated clone. These new approaches have different aims: (a) to provide alternative therapy to JAK inhibition; (b) to correct cytopenia; and (c) to inhibit fibrosis development. However, the main important goal is to find new disease modifier treatments, which will profoundly modify the progression of the disease without major toxicity. Presently the most promising approaches consist of the inhibition of telomerase and the combination of JAK2 inhibitors (ruxolitinib) with either a BCL2/BCL-xL or BET inhibitor. Yet, the most straightforward future approaches can be considered to be the development of and/or selective inhibition of JAK2V617F and the targeting MPL and calreticulin mutants by immunotherapy. It can be expected that the therapy of MF will be significantly improved in the coming years.

A Phase Ib Trial of AVID200, a TGFβ 1/3 Trap, in Patients with Myelofibrosis

PURPOSE

Myelofibrosis (MF) is a clonal myeloproliferative neoplasm characterized by systemic symptoms, cytopenias, organomegaly, and bone marrow fibrosis. JAK2 inhibitors afford symptom and spleen burden reduction but do not alter the disease course and frequently lead to thrombocytopenia. TGFβ, a pleiotropic cytokine elaborated by the MF clone, negatively regulates normal hematopoiesis, downregulates antitumor immunity, and promotes bone marrow fibrosis. Our group previously showed that AVID200, a potent and selective TGFβ 1/3 trap, reduced TGFβ1-induced proliferation of human mesenchymal stromal cells, phosphorylation of SMAD2, and collagen expression. Moreover, treatment of MF mononuclear cells with AVID200 led to increased numbers of progenitor cells (PC) with wild-type JAK2 rather than JAK2V617F.

PATIENTS AND METHODS

We conducted an investigator-initiated, multicenter, phase Ib trial of AVID200 monotherapy in 21 patients with advanced MF.

RESULTS

No dose-limiting toxicity was identified at the three dose levels tested, and grade 3/4 anemia and thrombocytopenia occurred in 28.6% and 19.0% of treated patients, respectively. After six cycles of therapy, two patients attained a clinical benefit by IWG-MRT criteria. Spleen and symptom benefits were observed across treatment cycles. Unlike other MF-directed therapies, increases in platelet counts were noted in 81% of treated patients with three patients achieving normalization. Treatment with AVID200 resulted in potent suppression of plasma TGFβ1 levels and pSMAD2 in MF cells.

CONCLUSIONS

AVID200 is a well-tolerated, rational, therapeutic agent for the treatment of patients with MF and should be evaluated further in patients with thrombocytopenic MF in combination with agents that target aberrant MF intracellular signaling pathways.

Energy expenditure in myelofibrosis patients treated with a JAK1/2 inhibitor

Weight gain is a known adverse effect of ruxolitinib, a JAK1/2 inhibitor that is the mainstay of treatment for many patients with myelofibrosis. The mechanisms behind weight increase with ruxolitinib is incompletely understood, although decreased adipose tissue lipolysis and increased appetite due to blocking the effects of leptin in the hypothalamus have been proposed. In order to explore the metabolic changes in ruxolitinib-treated patients with myelofibrosis, we performed a pilot study to assess the feasibility of using a portable indirect calorimeter to quantify energy expenditure before and during ruxolitinib treatment and report the results of two patients. Waist circumference increased during ruxolitinib treatment in both patients. Energy expenditure initially increased followed by a decrease and then increase again, but to levels below baseline. These results suggest that weight gain secondary to ruxolitinib may be related to changes in whole body energy expenditure.

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

Myelofibrosis (MF) presents an array of clinical manifestations and molecular profiles. The two distinct phenotypes- myeloproliferative and myelodepletive or cytopenic- are situated at the two poles of the disease spectrum and are largely defined by different degrees of cytopenias, splenomegaly, and distinct molecular profiles. The myeloproliferative phenotype is characterized by normal/higher peripheral blood counts or mildly decreased hemoglobin, progressive splenomegaly, and constitutional symptoms. The myeloproliferative phenotype is typically associated with secondary MF, higher JAK2 V617F burden, fewer mutations, and superior overall survival (OS). The myelodepletive phenotype is usually associated with primary MF, ≥2 cytopenias, modest splenomegaly, lower JAK2 V617F burden, higher fibrosis, greater genomic complexity, and inferior OS. Cytopenias are associated with mutations in epigenetic regulators/splicing factors, clonal evolution, disease progression, and shorter OS. Clinical variables, in conjunction with the molecular profiles, inform integrated prognostication and disease management. Ruxolitinib/fedratinib and pacritinib/momelotinib may be more suitable to treat patients with the myeloproliferative and myelodepletive phenotypes, respectively. Appreciation of MF heterogeneity and two distinct phenotypes, the different clinical manifestations and molecular profiles associated with each phenotype alongside the growing treatment expertise, the development of non-myelosuppressive JAK inhibitors, and integrated prognostication are leading to a new era in patient management. Physicians can increasingly tailor personalized treatments that will address the unique unmet needs of MF patients, including those presenting with the myelodepletive phenotype, to elicit optimal outcomes and extended OS across the disease spectrum.

SOHO State of the Art Updates and Next Questions: Novel Therapeutic Strategies in Development for Myelofibrosis

Development of myelofibrosis (MF) therapeutics has reached fruition as the transformative impact of JAK2 inhibitors in the MPN landscape is complemented/expanded by a profusion of novel monotherapies and rational combinations in the frontline and second line settings. Agents in advanced clinical development span various mechanisms of action (eg, epigenetic or apoptotic regulation), may address urgent unmet clinical needs (cytopenias), increase the depth/duration of spleen and symptom responses elicited by ruxolitinib, improve other aspects of the disease besides splenomegaly/constitutional symptoms (eg, resistance to ruxolitinib, bone marrow fibrosis or disease course), provide personalized strategies, and extend overall survival (OS). Ruxolitinib had a dramatic impact on the quality of life and OS of MF patients. Recently, pacritinib received regulatory approval for severely thrombocytopenic MF patients. Momelotinib is advantageously poised among JAK inhibitors given its differentiated mode of action (suppression of hepcidin expression). Momelotinib demonstrated significant improvements in anemia measures, spleen responses, and MF-associated symptoms in MF patients with anemia; and will likely receive regulatory approval in 2023. An array of other novel agents combined with ruxolitinib, such as pelabresib, navitoclax, parsaclisib, or as monotherapies (navtemadlin) are evaluated in pivotal phase 3 trials. Imetelstat (telomerase inhibitor) is currently evaluated in the second line setting; OS was set as the primary endpoint, marking an unprecedented goal in MF trials, wherein SVR35 and TSS50 at 24 weeks have been typical endpoints heretofore. Transfusion independence may be considered another clinically meaningful endpoint in MF trials given its correlation with OS. Overall, therapeutics are at the cusp of an exponential expansion and advancements that will likely lead to the golden era in treatment of MF.