Chronic Eosinophilic Leukemia Research Articles

Synthesis and biological activity evaluation of novel 2,6,9-trisubstituted purine conjugates as potential protein kinases inhibitors

Deregulation of protein kinases is often associated with uncontrolled cell proliferation in various tumours and the inhibition of kinase activity remains an important target for anti-tumour drug development. Here, we report a novel series of 2-aminocyclohexylamino-6-(substituted benzylamino/anilino)-9-cyclopentylpurine derivatives conjugated with putrescine, spermidine or spermine moiety in an effort to expand library of highly potent 2,6,9-trisubstituted purine kinase inhibitors. Presented aniline-type conjugates exhibit significant cytotoxic activity in MV4-11 and EOL-1 cell lines which correlates with FLT3-ITD and PDGFRα inhibition. Furthermore, 6-anilinopurines affected MAPK and STAT pathways in the treated MV4-11 cells and induced cell cycle arrest in the G1 phase. 6-Benzylaminopurines showed comparable CDK2 inhibitory activity to 6-anilinopurines, however, the PDGFRα and FLT3-ITD inhibition was strongly suppressed. Our results show that novel compounds containing aniline in the structure can be involved in the development of potent tyrosine kinase inhibitors with strong activity toward acute myeloid leukemia or chronic eosinophilic leukemia.

The Classification of Myeloproliferative Neoplasms: Rationale, Historical Background and Future Perspectives with Focus on Unclassifiable Cases.

Simple SummaryMyeloproliferative neoplasms (MPNs) are clonal hematological disorders, characterized by increased proliferation of the myeloid lineages in the bone marrow. Since their original recognition by William Damashek in 1951, MPNs have been extensively investigated at a clinical-pathological and molecular level. This prompted a progressive refinement of their classification and diagnostic criteria. Uncertainties nonetheless remain in a small (yet consistent) subset of cases, characterized by unconventional and/or overlapping clinical-pathological features. Such cases (referred to as MPN, unclassifiable [MPN-U]) encompass a broad spectrum of entities, including early phase MPNs, terminal (i.e., fibrotic) MPNs, MPNs associated with inflammatory or neoplastic disorders, and poorly characterized MPNs with clinical-pathological mismatch or atypical molecular features. In this review, we discuss the rationale behind the classification and diagnostic criteria of MPNs, focusing on the still open issues concerning MPN-U.Myeloproliferative neoplasms (MPNs) are a heterogeneous group of clonal hematopoietic stem cell disorders, characterized by increased proliferation of one or more myeloid lineages in the bone marrow. The classification and diagnostic criteria of MPNs have undergone relevant changes over the years, reflecting the increased awareness on these conditions and a better understanding of their biological and clinical-pathological features. The current World Health Organization (WHO) Classification acknowledges four main sub-groups of MPNs: (i) Chronic Myeloid Leukemia; (ii) classical Philadelphia-negative MPNs (Polycythemia Vera; Essential Thrombocythemia; Primary Myelofibrosis); (iii) non-classical Philadelphia-negative MPNs (Chronic Neutrophilic Leukemia; Chronic Eosinophilic Leukemia); and (iv) MPNs, unclassifiable (MPN-U). The latter are currently defined as MPNs with clinical-pathological findings not fulfilling the diagnostic criteria for any other entity. The MPN-U spectrum traditionally encompasses early phase MPNs, terminal (i.e., advanced fibrotic) MPNs, and cases associated with inflammatory or neoplastic disorders that obscure the clinical-histological picture. Several lines of evidence and clinical practice suggest the existence of additional myeloid neoplasms that may expand the spectrum of MPN-U. To gain insight into such disorders, this review addresses the history of MPN classification, the evolution of their diagnostic criteria and the complex clinical-pathological and biological features of MPN-U.

Upfront Targeted Tyrosine Kinase Inhibitor Therapy Improves Outcome in Patients with Myeloid/Lymphoid Neoplasms with Eosinophilia

▪BackgroundTo recognize the growing list of recurrent genetically defined eosinophilia driven by constitutively active tyrosine kinase fusion genes, the World Health Organization (WHO) created a provisional entity of myeloid/lymphoid neoplasms with eosinophilia (MLN-Eo) with rearrangement of PFGFRA, PDGFRB or FGFR1, or with PCM1- JAK2. These eosinophilic disorders are clinically and genetically heterogeneous. Annotating additional somatic mutations and relevant clinical features may have an impact on treatment selection and refine prognostication. In this study, we aim to describe the clinicopathologic characteristics and outcome with upfront targeted tyrosine kinase inhibitor (TKI) therapy in patients (pts) with MLN-Eo.MethodsWe retrospectively reviewed clinical and molecular data on 39 pts with newly diagnosed MLN-Eo with PDGFRA, PDGFRB, FGFR1, JAK2 or FLT3 rearrangement at Moffitt Cancer Center, Duke Cancer Center, and the UCSF Comprehensive Cancer Center. Clinical data was abstracted in accordance with institutional review board approved protocol. Pts were divided to two categories based on morphologic classification of the disease at diagnosis or at transformation: chronic phase and blastic phase disease. Each category was then divided into two subgroups: Cohort A) upfront TKI +/- other systemic therapy and Cohort B) no upfront TKI arm. Median time from chronic phase disease to blastic phase and median overall survival (mOS) (in whole cohort) were calculated using Kaplan Meier method and compared with log-rank test. Cox proportional hazards (PH) model was used to calculate hazard ratio (HR) in univariate analyses.ResultAmong the 39 pts included in the analysis, 22 pts had PDGFRA fusion (20)/activating mutations (2), 4 had PDGFRB, 7 had FGFR1, 2 had JAK2 (PCM1-JAK2 and BCR-JAK2), and 4 had FLT3 (3 ETV6-FLT3 and 1 FLT-3-TRIP11). Median age at first diagnosis of myeloid/lymphoid neoplasm was 54.5 years (range 9-76). Seventy-seven percents (30/39) were male. Chronic eosinophilic leukemia (CEL) was the most common clinical diagnosis and occurred in 11 pts (28%). Seven (18%) pts had both myeloid and lymphoid neoplasms either concurrently or sequentially. Sixteen (41%) pts presented with de-novo blastic phase at time of initial diagnosis.Among 23 pts who presented with chronic phase disease at diagnosis, nine patients did not receive TKI upfront. Five out of the nine patients (55%) developed blastic phase disease with a median follow up of 73 months. The median time to blastic phase was 45 months. No patients in the upfront TKI arm (n=14) had blastic transformation during follow up (Figure 1a, p<0.001).Among 21 pts who had blastic phase disease (16 pts with de-novo diagnosis and 5 pts with blastic transformations), 95% of them (20/21 pts) had treatment information and follow-up data available. At a median follow up of 37 months, 11 pts (55%) were deceased, and median OS was 44 months. Seven pts (35%) underwent allogeneic stem cell transplant (alloHSCT). Four patients received upfront TKI, and all of them achieved complete remission and were alive at the time of the study (Figure 1b). Among those pts, 2 had FLT3-ETV6 rearrangement, 1 with PDGFRA rearrangement and 1 with FGFR1 rearrangement. Two pts received single agent TKI only and two pts received TKIs followed by alloHSCT.In the univariate analysis, upfront TKI use was significantly associated with improved OS (HR 0.067, 95% CI [0.009-0.512], p=0.009). Complex cytogenetics at the time of initial diagnosis was associated with inferior OS, though statistical significance was not reached (table II).ConclusionOur data suggests that upfront TKI therapy is associated improved survival outcomes in pts with MLN-eo and is effective in preventing blastic transformation from chronic phase disease. As proposed, the driver oncogene most likely occurs in hematopoietic stem cells/progenitor cells in this entity. Upfront TKI can potentially suppress, even in some cases eradicate the malignant clone. The study is limited due to small sample size and retrospective nature, and larger study is needed to validate our observation. [Display omitted] DisclosuresSokol: Kyowa-Kirin: Membership on an entity's Board of Directors or advisory committees; Dren Bio: Membership on an entity's Board of Directors or advisory committees. Shah: Novartis: Consultancy, Other: Expenses; Pfizer: Consultancy, Other: Expenses; Amgen: Consultancy; Precision Biosciences: Consultancy; Kite, a Gilead Company: Consultancy, Honoraria, Other: Expenses, Research Funding; Pharmacyclics/Janssen: Honoraria, Other: Expenses; Acrotech/Spectrum: Honoraria; BeiGene: Consultancy, Honoraria; Incyte: Research Funding; Jazz Pharmaceuticals: Research Funding; Servier Genetics: Other; Bristol-Myers Squibb/Celgene: Consultancy, Other: Expenses; Adaptive Biotechnologies: Consultancy. Lancet: Agios: Consultancy; AbbVie: Consultancy; Celgene/BMS: Consultancy; Daiichi Sankyo: Consultancy; Astellas: Consultancy; BerGenBio: Consultancy; Millenium Pharma/Takeda: Consultancy; ElevateBio Management: Consultancy; Jazz: Consultancy. Kuykendall: Protagonist: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; BluePrint Medicines: Honoraria, Speakers Bureau; Prelude: Research Funding; Abbvie: Honoraria; Incyte: Consultancy; Novartis: Honoraria, Speakers Bureau; PharmaEssentia: Honoraria; Celgene/BMS: Honoraria, Speakers Bureau; CTI Biopharma: Honoraria. Padron: Stemline: Honoraria; BMS: Research Funding; Kura: Research Funding; Blueprint: Honoraria; Incyte: Research Funding; Taiho: Honoraria.

Comprehensive characterization of central BCL-2 family members in aberrant eosinophils and their impact on therapeutic strategies

PurposeHypereosinophilia represents a heterogenous group of severe medical conditions characterized by elevated numbers of eosinophil granulocytes in peripheral blood, bone marrow or tissue. Treatment options for hypereosinophilia remain limited despite recent approaches including IL-5-targeted monoclonal antibodies and tyrosine kinase inhibitors.MethodsTo understand aberrant survival patterns and options for pharmacologic intervention, we characterized BCL-2-regulated apoptosis signaling by testing for BCL-2 family expression levels as well as pharmacologic inhibition using primary patient samples from diverse subtypes of hypereosinophilia (hypereosinophilic syndrome n = 18, chronic eosinophilic leukemia not otherwise specified n = 9, lymphocyte-variant hypereosinophilia n = 2, myeloproliferative neoplasm with eosinophilia n = 2, eosinophilic granulomatosis with polyangiitis n = 11, reactive eosinophilia n = 3).ResultsContrary to published literature, we found no difference in the levels of the lncRNA Morrbid and its target BIM. Yet, we identified a near complete loss of expression of pro-apoptotic PUMA as well as a reduction in anti-apoptotic BCL-2. Accordingly, BCL-2 inhibition using venetoclax failed to achieve cell death induction in eosinophil granulocytes and bone marrow mononuclear cells from patients with hypereosinophilia. In contrast, MCL1 inhibition using S63845 specifically decreased the viability of bone marrow progenitor cells in patients with hypereosinophilia. In patients diagnosed with Chronic Eosinophilic Leukemia (CEL-NOS) or Myeloid and Lymphatic Neoplasia with hypereosinophilia (MLN-Eo) repression of survival was specifically powerful.ConclusionOur study shows that MCL1 inhibition might be a promising therapeutic option for hypereosinophilia patients specifically for CEL-NOS and MLN-Eo.

World Health Organization-defined eosinophilic disorders: 2022 update on diagnosis, risk stratification, and management.

The eosinophilias encompass a broad range of nonhematologic (secondary or reactive) and hematologic (primary or clonal) disorders with potential for end-organ damage. Hypereosinophilia (HE) has generally been defined as a peripheral blood eosinophil count greater than 1.5 × 109 /L. After exclusion of secondary causes of eosinophilia, diagnostic evaluation of primary eosinophilias relies on morphologic review of the blood and marrow, standard cytogenetics, fluorescence in situ hybridization, next generation sequencing gene assays, and flow immunophenotyping to detect histopathologic or clonal evidence for an acute or chronic hematolymphoid neoplasm. Disease prognosis relies on identifying the subtype of eosinophilia. After evaluation of secondary causes of eosinophilia, the 2016 World Health Organization endorses a semi-molecular classification scheme of disease subtypes. This includes the major category "myeloid/lymphoid neoplasms with eosinophilia and rearrangement of PDGFRA, PDGFRB, or FGFR1 or with PCM1-JAK2", and the myeloproliferative neoplasm subtype, "chronic eosinophilic leukemia, not otherwise specified" (CEL, NOS). Lymphocyte-variant HE is an aberrant T-cell clone-driven reactive eosinophila, and idiopathic hypereosinophilic syndrome (HES) is a diagnosis of exclusion. The goal of therapy is to mitigate eosinophil-mediated organ damage. For patients with milder forms of eosinophilia (eg, < 1.5 × 109 /L) without symptoms or signs of organ involvement, a watch and wait approach with close follow-up may be undertaken. Identification of rearranged PDGFRA or PDGFRB is critical because of the exquisite responsiveness of these diseases to imatinib. Corticosteroids are first-line therapy for patients with lymphocyte-variant HE and HES. Hydroxyurea and interferon-α have demonstrated efficacy as initial treatment and in steroid-refractory cases of HES. Mepolizumab, an interleukin-5 (IL-5) antagonist monoclonal antibody, was recently approved by the US Food and Drug Administration for patients with idiopathic HES. The use of the IL-5 receptor antibody benralizumab, as well as other targeted therapies such as JAK2 and FGFR1 inhibitors, is under active investigation.

A novel activating JAK1 mutation in chronic eosinophilic leukemia

AbstractHypereosinophilia (HE) has been defined as persistent eosinophilia >1.5 × 109/L; it is broadly divided into primary HE (clonal or neoplastic; HEN), secondary/reactive HE (HER), or HE of undetermined significance (HEUS) when no cause is identified. The use of myeloid next-generation sequencing (NGS) panels has led to the detection of several mutations in patients previously diagnosed with HEUS, reassigning some patients to the category of HEN, specifically the World Health Organization category of chronic eosinophilic leukemia, not otherwise specified (CEL, NOS). Here, we describe a novel somatic JAK1 pseudokinase domain mutation (R629_S632delinsSA) in a patient with HE that had initially been characterized as a variant of uncertain significance. We performed functional studies that demonstrated that this mutation results in growth factor independence of Ba/F3 cells in vitro and activation of the JAK-STAT pathway. These effects were abrogated by the JAK1/JAK2 inhibitor ruxolitinib. R629_S632delinsSA is the first known somatic mutation in JAK1 linked to a clonal eosinophilic neoplasm, and highlights the importance of the JAK-STAT pathway in eosinophil survival.

Chronic Eosinophilic Leukemia: Diagnosis and Therapy

Introduction In the 2017 World Health Organization (WHO) classification, chronic eosinophilic leukemia, not otherwise specified (CEL, NOS), is included as one of 7 distinct diagnostic entities under the major category of myeloproliferative neoplasms (MPNs).1 WHO defining criteria for CEL, NOS include: (a) peripheral blood eosinophilia >1.5×109/L; (b) evidence of clonal cytogenetic or molecular genetic abnormality, and/or (c) presence of excess myeloblasts (

Myeloid/lymphoid neoplasms with FLT3 rearrangement.

Myeloid/lymphoid neoplasms (M/LN) with 13q12/FLT3 rearrangement have been suggested as candidates for possible inclusion in the World Health Organization classification group of M/LN with eosinophilia (M/LN-eo). We report 12 patients with confirmed FLT3 rearrangement, six with t(12;13)/ETV6-FLT3; one with ins(13;22)/BCR-FLT3; and five with an unconfirmed partner gene located on chromosome bands 2p16, 3q27, 5q15, 5q35, and 7q36. Disease presentations were heterogeneous, including lymphoblastic leukemia/lymphoma, myeloid sarcoma, chronic eosinophilic leukemia, chronic myelomonocytic leukemia, and myelodysplastic syndrome. However, some common features were observed, such as extramedullary involvement (n = 7, 58%), associated eosinophilia in blood, bone marrow, or tissue (n = 8, 67%), multilineage involvement, either as biphasic myeloid/lymphoid neoplasms (n = 2) or mixed phenotype acute leukemia (n = 2). Mutations were detected in 4/8 (50%) patients by next-generation sequencing. None (0/10) had FLT3 or KIT mutations. Eleven patients received disease-based chemotherapy or hypomethylating agents, three received FLT3 inhibitors, and five patients proceeded to hematopoietic stem cell transplant. Together with a review of 16 cases published in the literature, it is apparent that M/LNs with FLT3 rearrangement show disease features reminiscent of members in the category of M/LN-eo with PDGFRA, PDGFRB, FGFR1, and PCM1/JAK2 rearrangement, characterized by a specific gene rearrangement, frequent eosinophilia, multi-lineage involvement and therapeutic benefit from kinase inhibitors.

ATG5 promotes eosinopoiesis but inhibits eosinophil effector functions

AbstractEosinophils are white blood cells that contribute to the regulation of immunity and are involved in the pathogenesis of numerous inflammatory diseases. In contrast to other cells of the immune system, no information is available regarding the role of autophagy in eosinophil differentiation and functions. To study the autophagic pathway in eosinophils, we generated conditional knockout mice in which Atg5 is deleted within the eosinophil lineage only (designated Atg5eoΔ mice). Eosinophilia was provoked by crossbreeding Atg5eoΔ mice with Il5 (IL-5) overexpressing transgenic mice (designated Atg5eoΔIl5tg mice). Deletion of Atg5 in eosinophils resulted in a dramatic reduction in the number of mature eosinophils in blood and an increase of immature eosinophils in the bone marrow. Atg5-knockout eosinophil precursors exhibited reduced proliferation under both in vitro and in vivo conditions but no increased cell death. Moreover, reduced differentiation of eosinophils in the absence of Atg5 was also observed in mouse and human models of chronic eosinophilic leukemia. Atg5-knockout blood eosinophils exhibited augmented levels of degranulation and bacterial killing in vitro. Moreover, in an experimental in vivo model, we observed that Atg5eoΔ mice achieve better clearance of the local and systemic bacterial infection with Citrobacter rodentium. Evidence for increased degranulation of ATG5low-expressing human eosinophils was also obtained in both tissues and blood. Taken together, mouse and human eosinophil hematopoiesis and effector functions are regulated by ATG5, which controls the amplitude of overall antibacterial eosinophil immune responses.

Severe Eosinophilia Associated with FIP1L1/PDGFRA Rearrangement Presenting with Yamaguchi Syndrome

FIP1L1/PDGFRA is a rare genetic rearrangement, presenting most commonly as Chronic Eosinophilic Leukemia (CEL), but may also be associated with other myeloid and lymphoid neoplasms. The peripheral blood and bone marrow exhibit a striking eosinophilia, often associated with an increased number of mast cells on trephine biopsy. Tissue infiltration by eosinophils and release of cytokines from eosinophilic granules mediate multi-organ tissue damage. The tyrosine kinase inhibitor Imatinib has been shown to induce rapid and complete clinical and haematological responses in patients harboring the mutation. We present the case of a young patient with CEL associated with PDGFRA rearrangement, presenting with severe eosinophilia and evidence of multi-organ damage (cardiac, renal, endocrine and respiratory). The peripheral blood and bone marrow displayed a striking eosinophila, and FISH analysis for FIP1L1/PDGFRA revealed a positive fusion signal in 92% of the nuclei examined. Echocardiography showed left ventricular apical hypertrophy (Yamaguchi syndrome), which has previously not been reported in this subset of patients. He was managed with supportive care, along with low-dose imatinib (100mg/day initially), to which he achieved a rapid clinical and haematological response. Currently, five months from the initial diagnosis, he is doing well on low dose imatinib (100 mg) twice a week.

FIP1L1- platelet-derived growth factor receptor A -positive chronic eosinophilic leukemia showing dramatic response to imatinib

Abstract Introduction: Eosinophilia associated with FIP1L1- platelet-derived growth factor receptor A (PDGFRA) rearrangement is one of a subgroup of chronic eosinophilic leukemia, The 2008 World Health Organization classification of tumors of hematopoietic and lymphoid tissues established a new category for myeloid and lymphoid neoplasms with eosinophilia and abnormalities in PDGFRA, platelet-derived growth factor receptor Beta (PDGFRB) or Fibroblast growth factor receptor 1. The number of reported cases is limited worldwide, with limited data on the best modality of treatment of such disease. Patient concerns: A 48-year-old male patient with recurrent visits to the hospital presenting with multiple vague symptoms but found to have persistent marked eosinophilia. Diagnosis: The patient was diagnosed as a case of Myeloid/lymphoid neoplasms with eosinophilia and rearrangement of PDGFRA Interventions: The patient was started on Tyrosine kinase inhibitor (Imatinib) 100 mg daily. Outcomes: The patient eosinophilia has improved markedly, and the patient's eosinophils levels dropped to normal levels within 3 weeks period. Conclusion: This case indicates that in the era of Tyrosine Kinase inhibitors such as imatinib, the prognosis of Eosinophilia associated with FIP1L1-PDGFRA rearrangement has significantly improved And Prompt treatment with imatinib can lead to complete hematological response and resolution of any organ damage involved with this disease.

Eosinophilia/Hypereosinophilia in the Setting of Reactive and Idiopathic Causes, Well-Defined Myeloid or Lymphoid Leukemias, or Germline Disorders.

To report the findings of the 2019 Society for Hematopathology/European Association for Haematopathology Workshop within the categories of reactive eosinophilia, hypereosinophilic syndrome (HES), germline disorders with eosinophilia (GDE), and myeloid and lymphoid neoplasms associated with eosinophilia (excluding entities covered by other studies in this series). The workshop panel reviewed 109 cases, assigned consensus diagnosis, and created diagnosis-specific sessions. The most frequent diagnosis was reactive eosinophilia (35), followed by acute leukemia (24). Myeloproliferative neoplasms (MPNs) received 17 submissions, including chronic eosinophilic leukemia, not otherwise specified (CEL, NOS). Myelodysplastic syndrome (MDS), MDS/MPN, and therapy-related myeloid neoplasms received 11, while GDE and HES received 12 and 11 submissions, respectively. Hypereosinophilia and HES are defined by specific clinical and laboratory criteria. Eosinophilia is commonly reactive. An acute leukemic onset with eosinophilia may suggest core-binding factor acute myeloid leukemia, blast phase of chronic myeloid leukemia, BCR-ABL1-positive leukemia, or t(5;14) B-lymphoblastic leukemia. Eosinophilia is rare in MDS but common in MDS/MPN. CEL, NOS is a clinically aggressive MPN with eosinophilia as the dominant feature. Bone marrow morphology and cytogenetic and/or molecular clonality may distinguish CEL from HES. Molecular testing helps to better subclassify myeloid neoplasms with eosinophilia and to identify patients for targeted treatments.

Re-Evaluating the Prognosis and Transformation Risk of Chronic Eosinophilic Leukemia

Chronic eosinophilic leukemia, not otherwise specified, (CEL-NOS) is a rare myeloproliferative neoplasm defined by an autonomous clonal expansion of eosinophil precursors. CEL-NOS has long been considered an aggressive disease with a poor prognosis and high risk of transformation to blast phase. This impression was reinforced by a case series of 10 patients with CEL-NOS in which median overall survival was 22 months and in which one half of patients transformed to acute leukemia at a median of 20 months from time of diagnosis (Helbig et al, American Journal of Hematology, 2012). However, this has not been confirmed in any population-based or large cohort studies. We sought to evaluate whether this poor prognosis is consistent across a larger patient database. We identified 487 patients with CEL-NOS in the Surveillance Epidemiology and End Result-18 database. Patients were predominantly male (60.5%) with a median age of 57 at time of diagnosis. Overall survival at 2 years from diagnosis for the cohort was 92.7% with a disease-specific survival of 97.2%. At 5 years overall survival remained relatively high (88.7%) as did disease-specific survival (95.6%). Median follow-up was 56.5 months (range 0-191 months). Median survival for patients who died of CEL was 5 months (range 0-46 months). This raises the possibility of a dichotomous patient population wherein there is one group of patients with a good prognosis, and a second group with aggressive disease and significantly poorer prognosis. Of note, the majority of the patients who died from CEL-NOS (21/23) died within two years of diagnosis. Only three of the patients studied developed acute leukemia, two with acute myeloid leukemia and one acute lymphoblastic leukemia; all three died of their second malignancy within 28-60 months. An additional 11 patients developed lymphoma, 2 Hodgkin lymphoma and 9 non-Hodgkin lymphoma (NHL), including peripheral T-cell lymphoma (3/9), diffuse large B-cell lymphoma (3/9), angioimmunoblastic T-cell lymphoma (2/9), and Burkitt's lymphoma (1/9). This data suggests that the current impression of CEL-NOS as a rare and aggressive disease with a poor prognosis may be more nuanced than previously appreciated. The limitations of SEER data are significant and include concerns regarding both accuracy of diagnosis and collection bias. However, the incongruence between current disease perception and the large-scale data available suggest that further study is both warranted and necessary. Next steps would include the creation of a prospective national registry of patients with CEL-NOS. This would assist both in giving appropriate disease-counseling for patients and in better assessing which patients might benefit from treatment with chemotherapy. Disclosures No relevant conflicts of interest to declare.

Rates of Thrombotic Events in Hypereosinophilic Syndrome and the Effect of Molecular Aberrations in Thrombotic Risk

Background: Idiopathic hypereosinophilia and hypereosinophilic syndrome (HES) comprise a rare, heterogeneous group of hematologic disorders characterized by the overproduction of eosinophils leading to tissue eosinophilic infiltration and damage. Hypereosinophilia can be primary - due to a clonal or malignant process - or secondary to a non-clonal process. Primary eosinophilia can be accompanied by clonal markers, such as in myeloid/lymphoid neoplasms with eosinophilia and rearrangement of PDGFRA/B, FGFR1 or PCM1-JAK2, genetic mutations or chromosomal abnormalities leading to a diagnosis of chronic eosinophilic leukemia. Without easily identifiable clonal markers, a diagnosis of idiopathic HES is made after secondary causes are excluded. Thrombotic complications in clonal eosinophilic disorders have been described in case reports but the prevalence of thrombosis has not been extensively studied. We hypothesized that HES is associated with an increased thrombotic risk compared to the general population. Additionally, given the known increased thrombotic risk in patients with clonal hematopoiesis of indeterminate potential, we also hypothesized that the risk of thrombosis is greatest in HES patients with evidence of an underlying clonal process. Methods: Using an institutional database, we retrospectively analyzed 44 patients with HES who had undergone molecular testing with a DNA based next generation sequencing (NGS) assay (Heme SnapShot) and an RNA based NGS assay (Heme fusion) as part of their work up for HES at Massachusetts General Hospital from 2016 to 2020. Patients with secondary eosinophilia were excluded. We used Fisher's exact test to compare rates of thrombotic events or death between patients with and without molecular aberration. Relative risk and corresponding 95% CI was estimated by fitting a log-binomial regression model. Results: Among the 44 patients analyzed, 16 (36.4%) had a molecular aberration detected on NGS. Of the patients with molecular aberrations detected, 4 (25%) had PGFRA, PGFRB, or FGFR1 fusions. Other pathogenic mutations were as follows - 1 (6.3%) JAK2 mutation, 3 (18.8%) TET2, 1 (6.3%) DNMT3A and 9 (56.4%) had mutations in other genes. White blood cell count, absolute eosinophil count, hematocrit, platelet count, tryptase and vitamin B12 levels at diagnosis of HES were similar between the two groups. After a median follow-up time of 29 months (IQR 19.3, 52), 9 (20.5%) of all HES patients had a thrombotic event after diagnosis of HES (4 venous and 5 arterial) with a median time to first thrombotic event of 14.0 months (IQR 3.5, 28.0). HES patients with a molecular aberration had increased number of thrombotic events compared to HES patients with no molecular aberrations, 37.5% versus 10.7% respectively (p = 0.053, risk ratio 3.5, 95% CI 1.01 - 12.12). Three patients with molecular aberrations died versus 1 patient with no molecular aberrations (p = 0.129, risk ratio 5.25, 95% CI 0.59 - 46.36). Among patients with at least 12 months of follow-up (n = 40, 14 with and 26 without molecular aberrations), the one-year cumulative incidence of thrombotic events was 42.9% in patients with molecular aberrations vs 11.5% without (p = 0.044, RR 3.7 95% CI 1.2-12.0). HES patients who had thrombotic events had an increased risk of death compared to those without thrombotic events (p = 0.0226, RR 11.7, 95% CI 1.8 - 75.2). Conclusions: Thrombotic complications are common in the current study of patients with HES and are associated with an increased risk of death. Although our patient cohort was small, presence of molecular aberrations had increased rates of thrombotic events and mortality, suggesting an area of further study including possible therapeutic trials. Figure 1 Disclosures Brunner: Takeda: Research Funding; Celgene: Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Research Funding; AstraZeneca: Research Funding; Forty-Seven Inc: Membership on an entity's Board of Directors or advisory committees; Jazz Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees. Al-Samkari:Argenx: Consultancy; Amgen: Research Funding; Dova: Consultancy, Research Funding; Agios: Consultancy, Research Funding; Rigel: Consultancy. Rosovsky:Bristol-Myers Squibb, Janssen: Research Funding; Bristol-Myers Squibb, Dova, Janssen, Portola: Consultancy. Fathi:PTC Therapeutics: Consultancy; Takeda: Consultancy; TrovaGene: Consultancy; Amgen: Consultancy; Bristol-Myers Squibb: Consultancy, Research Funding; Celgene: Consultancy, Research Funding; Astellas: Consultancy; Novartis: Consultancy; NewLink Genetics: Consultancy, Honoraria; Daiichi Sankyo: Consultancy; Forty Seven: Consultancy; Jazz: Consultancy, Honoraria; Kite: Consultancy, Honoraria; Trillium: Consultancy; Seattle Genetics: Consultancy, Research Funding; Pfizer: Consultancy; Kura: Consultancy; Boston Biomedical: Consultancy; Blue Print Oncology: Consultancy; AbbVie: Consultancy; Agios: Consultancy, Research Funding; Amphivena: Consultancy, Honoraria. Weitzman:Abbvie: Consultancy. Hobbs:Incyte: Research Funding; Bayer: Research Funding; Novartis: Honoraria; Celgene/BMS: Honoraria; Merck: Research Funding; Constellation: Honoraria, Research Funding; Jazz: Honoraria.

Myeloid/lymphoid neoplasms with eosinophilia and FLT3 rearrangement

Myeloid/lymphoid neoplasms with eosinophilia and gene rearrangement are a unique category in the WHO classification, and include cases with rearrangement of PDGFRA, PDGFRB, FGFR1, and PCM1-JAK2. We report three patients presented with eosinophilia and FLT3 rearrangement: the first case with chronic eosinophilic leukemia, not otherwise specified and T-lymphoblastic leukemia/lymphoma; the second case with myeloid sarcoma; and the last case with high-grade myelodysplastic syndrome. The first case showed t(13;14)(q12;q32), which encoded FLT3-TRIP11. The patient was treated with intense chemotherapy and subsequently sorafenib with clinical improvement. Unfortunately, the patient showed persistent residual disease and passed away 9 months after the diagnosis from pneumonia. The other two cases both showed ETV6-FLT3. The second patient was treated with local radiation and systemic chemotherapy including sorafenib and was alive. The third patient was treated with chemotherapy but showed transformation to acute myeloid leukemia and died 15 months after diagnosis. These cases are among a growing number of cases with FLT3 rearrangement that all showed similar clinicopathologic features characterized by myeloproliferative neoplasm with eosinophilia and frequent T lymphoblastic leukemia/lymphoma. Therefore, we propose that the myeloid/lymphoid neoplasms with eosinophilia and FLT3 rearrangement be included in the WHO category of myeloid/lymphoid neoplasms with eosinophilia and gene rearrangement.

Update on CML-Like Disorders

Chronic myeloid leukemia (CML) is defined for many years as BCR-ABL1 positive disease, but older publications refer to a poor prognosis, clinically heterogeneous entity termed ‘BCR-ABL1 negative CML’ constituting about 5% of CML cases. Apart from very rare CML cases with cytogenetically cryptic, atypical variant BCR-ABL1 fusions that had been inadvertently missed during the diagnostic work up, most of these cases would now be classified as a subtype of myelodysplastic/myeloproliferative neoplasm (MDS/MPN), such as atypical CML (aCML), chronic myelomonocytic leukemia (CMML), or chronic neutrophilic leukemia (CNL). A minority would be classified as systemic mastocytosis with associated hematological neoplasm (SM-AHN), myeloid/lymphoid neoplasms associated with eosinophilia and rearrangement of PDGFRA, PDGFRB, FGFR1 or with PCM1-JAK2 (MLN-eo), or chronic eosinophilic leukemia not otherwise specified (CEL-NOS).1

An unusual presentation of chronic eosinophilic leukemia as pulmonary arterial hypertension- A Case Report

An unusual presentation of chronic eosinophilic leukemia as pulmonary arterial hypertension- A Case Report

S100A8 and S100A9 Promote Apoptosis of Chronic Eosinophilic Leukemia Cells.

S100A8 and S100A9 function as essential factors in inflammation and also exert antitumor or tumorigenic activity depending on the type of cancer. Chronic eosinophilic leukemia (CEL) is a rare hematological malignancy having elevated levels of eosinophils and characterized by the presence of the FIP1L1-PDGFRA fusion gene. In this study, we examined the pro-apoptotic mechanisms of S100A8 and S100A9 in FIP1L1-PDGFRα+ eosinophilic cells and hypereosinophilic patient cells. S100A8 and S100A9 induce apoptosis of the FIP1L1-PDGFRα+ EoL-1 cells via TLR4. The surface TLR4 expression increased after exposure to S100A8 and S100A9 although total TLR4 expression decreased. S100A8 and S100A9 suppressed the FIP1L1-PDGFRα-mediated signaling pathway by downregulating FIP1L1-PDGFRα mRNA and protein expression and triggered cell apoptosis by regulating caspase 9/3 pathway and Bcl family proteins. S100A8 and S100A9 also induced apoptosis of imatinib-resistant EoL-1 cells (EoL-1-IR). S100A8 and S100A9 blocked tumor progression of xenografted EoL-1 and EoL-1-IR cells in NOD-SCID mice and evoked apoptosis of eosinophils derived from hypereosinophilic syndrome as well as chronic eosinophilic leukemia. These findings may contribute to a progressive understanding of S100A8 and S100A9 in the pathogenic and therapeutic mechanism of hematological malignancy.

ETV6-ACSL6 fusion gene in myeloid neoplasms: clinical spectrum, current practice, and outcomes

BackgroundETV6-ACSL6 is a fusion gene rarely reported in myeloid malignancies, and its clinical characteristics, proper treatment strategies, and effect on prognosis are poorly understood.ResultsSixteen patients with the ETV6-ACSL6 fusion gene were identified, with a median age of 50 years. Twelve patients were male. Clinical diagnoses included chronic eosinophilic leukemia, not otherwise specified, acute myeloid leukemia, and other types of myeloproliferative and myelodysplastic disorders. Ten out of 12 patients had increased levels of eosinophils, and four out of five had increased levels of basophils in peripheral blood. Treatment with tyrosine kinase inhibitors was ineffective. The prognosis of the patients was poor, with seven patients dying within 1 year.ConclusionsPatients with the ETV6-ACSL6 fusion gene mainly present with myeloproliferative and myelodysplastic disorders, typically with increased eosinophils and/or basophils and poor survival. Intensive therapies such as allogenic stem cell transplantation should be an initial consideration for eligible patients.

Chronic eosinophilic leukemia associated with the &lt;i&gt;FIP1L1&lt;/i&gt;-&lt;i&gt;PDGFRA&lt;/i&gt; fusion gene

Chronic eosinophilic leukemia associated with the &lt;i&gt;FIP1L1&lt;/i&gt;-&lt;i&gt;PDGFRA&lt;/i&gt; fusion gene