JAK2-positive Essential Thrombocythemia Research Articles

Assessing the Feasibility of Thromboprophylaxis with Apixaban in JAK2-Positive Myeloproliferative Neoplasm Patients: The Airport-MPN Trial

Introduction: Thrombosis is a major cause of mortality and morbidity in myeloproliferative neoplasms (MPN). In patients classified as high-risk for thrombosis, current guidelines recommend the use of cytoreduction therapy and low-dose aspirin (e.g., ASA 81 mg daily) to decrease the risk of thrombotic events. However, use of low-dose aspirin is based on limited evidence and is associated with a significant failure rate. Thromboprophylaxis with low-dose direct oral anticoagulants (e.g., apixaban 2.5 mg BID) is an appealing option in MPN, specifically when patients carry the JAK2 mutation, based on the pathophysiology of thrombus formation associated with this driver mutation. In other populations, thromboprophylaxis with a low-dose direct oral anticoagulant has been associated with a reduced risk of arterial and venous thrombotic complications, when compared to low-dose aspirin. Hence, we conducted a pilot trial to assess the feasibility of conducting a randomized controlled trial evaluating the efficacy and safety of apixaban (2.5 mg BID) compared to aspirin (81 mg daily) to prevent thrombotic complications in patients with JAK2-positive MPN (JAK2MPN). Methods: This was a multi-centre, prospective, open-label, blinded endpoint pilot trial (NCT04243122), conducted in three Canadian centers (Ottawa, Calgary, Sherbrooke). Adult patients with a confirmed diagnosis of polycythemia vera, JAK2-positive essential thrombocythemia or JAK2-positive pre-fibrotic myelofibrosis (per local clinical definitions) requiring low-dose aspirin for thromboprophylaxis were eligible. Both patients with an incident diagnosis of JAK2MPN (defined as diagnosed within 1 year) and patients with prevalent disease were targeted for recruitment. Exclusion criteria included a contraindication to thromboprophylaxis or the need for a specific anticoagulant or non-aspirin anti-platelet agent. Patients with a prior history of venous thromboembolism were eligible if they had completed a minimum of 6 months of anticoagulation therapy. Participants were randomized 1:1 to receive apixaban 2.5mg BID or aspirin 81mg daily, along with cytoreductive therapy (per guidelines). The study treatment duration was 6 months. Follow-up occurred at 3, 6 and 7 months after allocation of the study medication. The primary study outcome for feasibility was the monthly recruitment rate per study site over a 6-month follow-up period. Secondary outcomes included rates of thrombotic and bleeding complications. The total estimated sample size was 44 participants (22 per arm). Due to the COVID-19 pandemic, not all sites were able to start recruitment at the same time and the total recruitment period spanned over 24 months. Results: During this 24-month recruitment period, 93 JAK2MPN patients were screened for eligibility. Of these, 69 were eligible and 64% of eligible patients consented to participate. We therefore recruited 44 participants, for a recruitment rate of 0.8 patient per centre per month. Baseline characteristics of participants are presented in Table 1. A total of 29 prevalent cases and 15 incident cases were included. Secondary efficacy, safety, and feasibility outcomes (relating to thrombotic events, bleeding complications, and study compliance) will be available at the ASH Meeting, since all participants will have completed the 6-month treatment duration by October 2023. Discussion: Despite the challenges of the COVID-19 pandemic, we have recruited 100% of our target population. Given the chronicity of MPN, most outpatient clinics functioned remotely during the pandemic, precluding recruitment. Nevertheless, by adapting to the realities of the pandemic, we achieved our recruitment target demonstrating feasibility of a larger trial. The strategies adopted during this pilot trial to recruit participants, such as active screening of clinic lists for potential participants and direct communication with MPN specialists, will be applied to our larger scale trial. Conclusion: This pilot trial demonstrated the feasibility of conducting a large-scale trial evaluating the superiority of apixaban over aspirin for the thromboprophylaxis of JAK2MPN patients. As JAK2MPN are rare diseases, we have partnered with counterparts in France to conduct an international study on the efficacy and safety of direct oral anticoagulant thromboprophylaxis in JAK2MPN patients.

Abstract 15274: STEMI as Initial Manifestation of Essential Thrombocythemia

Background: Essential thrombocythemia (ET) is a myeloproliferative neoplasm of myeloid cell expansion, mainly excessive platelet production, associated with thrombotic complications. Myocardial infarction (MI) in the setting of ET can result from thrombosis in the absence of coronary atherosclerosis. Here we present a case of ST elevation MI in the setting of previously undiagnosed ET. Case Report: A 59-year-old male with hypertension presented to the ED with left upper extremity weakness which started upon waking. On exam, he was in acute distress and diaphoretic. EKG revealed sinus rhythm with ST elevation in II, III, aVF, V5, and V6 suggesting inferolateral STEMI (Figure 1A). Labs were notable for Hgb 8.5g/dL, white blood cell count 33k/μL, and platelets 1.9million/μL. Decision Making: He was loaded with aspirin and clopidogrel (dual antiplatelet therapy-DAPT) and taken for coronary angiogram which revealed 80-90% thrombotic occlusion of the left circumflex artery (Figure 1b). Thrombectomy was performed and a drug-eluting stent was placed. A bone marrow biopsy showed JAK2 positive ET with myelofibrosis. He was immediately started on hydroxyurea. Platelets remained elevated, thus pegylated IFN alpha-2a was started which normalized platelet count. He remained on DAPT through discharge with no recurrent ischemic events or in-stent thrombosis during the 45-day hospitalization post stent placement. Conclusion: Patients with ET are at high risk for arterial thrombosis regardless of the presence of traditional atherosclerotic risk factors. High-risk patients, which includes those age over 60 with JAK2 mutation or history of arterial thrombosis, should be treated prophylactically with aspirin and hydroxyurea for cytoreduction. MI may be the first clinical manifestation of ET, even in patients without atherosclerotic risk factors. Initial management in patients with ET presenting with STEMI includes PCI with DAPT and early cytoreductive therapy.

Mixed phenotype acute leukemia and lineage switch from lymphoblastic leukemia to myeloid leukemia in the course of Philadelphia-negative myeloproliferative neoplasm – case reports and literature review

AbstractPhiladelphia-negative myeloproliferative neoplasms (Ph-neg MPNs) are characterized by clonal hematopoiesis derived from a mutated hematopoietic stem cell. Ph-neg MPNs rarely transforms into acute leukemia, and in most cases, the transformation leads to the development of acute myeloid leukemia (AML). The incidence of mixed-phenotype leukemia (MPAL) or acute lymphoblastic leukemia (ALL) with lineage switch is much rarer. The unidentified lineage of blast cells is due to the immaturity of their undifferentiated progenitors with co-expression of myeloid and lymphoid antigens. The prognosis of secondary acute leukemia transformed from Ph-neg MPN is very unfavorable, especially in MPAL or lineage switch from ALL to AML cases. Moreover, there are no therapeutic protocols for these specific leukemia subtypes. Therefore, we believe that all cases of MPAL or lineage switch leukemia should be reported. This article presents the case of a patient with JAK2-positive essential thrombocythemia (ET) transformed to MPAL, and a patient with triple-negative primary myelofibrosis (PMF) (negative for JAK2, CALR, and MPL) transformed to ALL with subsequent lineage switch to AML.

JAK-2 V617F mutation increases heparanase procoagulant activity.

Patients with polycythaemia vera (PV), essential thrombocythaemia (ET) and primary myelofibrosis (PMF) are at increased risk of arterial and venous thrombosis. In patients with ET a positive correlation was observed between JAK-2 V617F mutation, that facilitates erythropoietin receptor signalling, and thrombotic events, although the mechanism involved is not clear. We previously demonstrated that heparanase protein forms a complex and enhances the activity of the blood coagulation initiator tissue factor (TF) which leads to increased factor Xa production and subsequent activation of the coagulation system. The present study was aimed to evaluate heparanase procoagulant activity in myeloproliferative neoplasms. Forty bone marrow biopsies of patients with ET, PV, PMF and chronic myelogenous leukaemia (CML) were immunostained to heparanase, TF and TF pathway inhibitor (TFPI). Erythropoietin receptor positive cell lines U87 human glioma and MCF-7 human breast carcinoma were studied. Heparanase and TFPI staining were more prominent in ET, PV and PMF compared to CML. The strongest staining was in JAK-2 positive ET biopsies. Heparanase level and procoagulant activity were higher in U87 cells transfected to over express JAK-2 V617F mutation compared to control and the effect was reversed using JAK-2 inhibitors (Ruxolitinib, VZ3) and hydroxyurea, although the latter drug did not inhibit JAK-2 phosphorylation. Erythropoietin increased while JAK-2 inhibitors decreased the heparanase level and procoagulant activity in U87 and MCF-7 parental cells. In conclusion, JAK-2 is involved in heparanase up-regulation via the erythropoietin receptor. The present findings may potentially point to a new mechanism of thrombosis in JAK-2 positive ET patients.

Microarray and Proteomic Analyses of Myeloproliferative Neoplasms with a Highlight on the mTOR Signaling Pathway.

The gene and protein expression profiles in myeloproliferative neoplasms (MPNs) may reveal gene and protein markers of a potential clinical relevance in diagnosis, treatment and prediction of response to therapy. Using cDNA microarray analysis of 25,100 unique genes, we studied the gene expression profile of CD34+ cells and granulocytes obtained from peripheral blood of subjects with essential thrombocythemia (ET), polycythemia vera (PV) and primary myelofibrosis (PMF). The microarray analyses of the CD34+ cells and granulocytes were performed from 20 de novo MPN subjects: JAK2 positive ET, PV, PMF subjects, and JAK2 negative ET/PMF subjects. The granulocytes for proteomic studies were pooled in 4 groups: PV with JAK2 mutant allele burden above 80%, ET with JAK2 mutation, PMF with JAK2 mutation and ET/PMF with no JAK2 mutation. The number of differentially regulated genes was about two fold larger in CD34+ cells compared to granulocytes. Thirty-six genes (including RUNX1, TNFRSF19) were persistently highly expressed, while 42 genes (including FOXD4, PDE4A) were underexpressed both in CD34+ cells and granulocytes. Using proteomic studies, significant up-regulation was observed for MAPK and PI3K/AKT signaling regulators that control myeloid cell apoptosis and proliferation: RAC2, MNDA, S100A8/9, CORO1A, and GNAI2. When the status of the mTOR signaling pathway related genes was analyzed, PI3K/AKT regulators were preferentially up-regulated in CD34+ cells of MPNs, with down-regulated major components of the protein complex EIF4F. Molecular profiling of CD34+ cells and granulocytes of MPN determined gene expression patterns beyond their recognized function in disease pathogenesis that included dominant up-regulation of PI3K/AKT signaling.

Acquired von Willebrand syndrome type 2A in a JAK2-positive essential thrombocythaemia -affected member of a large von Willebrand disease family with a novel autosomal dominant A1716P mutation

Acquired von Willebrand syndrome type 2A in a JAK2-positive essential thrombocythaemia-affected member of a large von Willebrand disease family with a novel autosomal dominant A1716P mutation -

Observation versus antiplatelet therapy as primary prophylaxis for thrombosis in low-risk essential thrombocythemia

AbstractThe effectiveness of antiplatelet therapy as primary prophylaxis for thrombosis in low-risk essential thrombocythemia (ET) is not proven. In this study, the incidence rates of arterial and venous thrombosis were retrospectively analyzed in 300 low-risk patients with ET treated with antiplatelet drugs as monotherapy (n = 198) or followed with careful observation (n = 102). Follow-up was 802 and 848 person-years for antiplatelet therapy and observation, respectively. Rates of thrombotic events were 21.2 and 17.7 per 1000 person-years for antiplatelet therapy and observation, respectively (P = .6). JAK2 V617F–positive patients not receiving antiplatelet medication showed an increased risk of venous thrombosis (incidence rate ratio [IRR]: 4.0; 95% CI: 1.2-12.9; P = .02). Patients with cardiovascular risk factors had increased rates of arterial thrombosis while on observation (IRR: 2.5; 95% CI: 1.02-6.1; P = .047). An increased risk of major bleeding was observed in patients with platelet count greater than 1000 × 109/L under antiplatelet therapy (IRR: 5.4; 95% CI: 1.7-17.2; P = .004). In conclusion, antiplatelet therapy reduces the incidence of venous thrombosis in patients with JAK2-positive ET and the rate of arterial thrombosis in patients with associated cardiovascular risk factors. In the remaining low-risk patients, this therapy is not effective as primary prophylaxis of thrombosis, and observation may be an adequate option.

Multiple myeloma with concomitant JAK2-positive essential thrombocythemia post-successful autologous peripheral blood hematopoietic stem cell transplant

Multiple myeloma with concomitant JAK2-positive essential thrombocythemia post-successful autologous peripheral blood hematopoietic stem cell transplant

Blast phase of essential thrombocythemia: A single center study

Blast phase (BP) may occur as a late event in essential thrombocythemia (ET). This study includes 19 patients with post-ET BP diagnosed and followed in a single institution. At BP, 63% of patients had leukocytosis (white blood cell count >10 x 10(9)/L), 74% had anemia (hemoglobin value <10 g/dL), 74% had thrombocytopenia (platelet count <100 x 10(9)/L), and 84% were over 65 years of age. Cytogenetic analysis was available in 10 patients: six had karyotype aberrations. According to cytogenetic-based risk stratification of de novo acute leukemia (AL), all patients had an unfavorable profile. JAK2 (V617F) mutational status was evaluated in five patients. In two of them, the JAK2 mutation was undetectable in blast cells (one with JAK2-positive ET), whereas in three both granulocytes and blast cells displayed the mutation. Treatment of BP was patient-based according to the performance status and co-morbidities and consisted of palliation in 14 patients, and of induction of remission in five. Median survival was 2.3 months (range 0.2-22.3), irrespective of the treatment received. In conclusion, this study indicates that AL evolved from ET has unfavorable clinical and biological features. JAK2 (V617F)-positive ET may evolve in few instances into JAK2-negative leukemia. The outcome of patients is poor whatever the treatment used.

Impact of JAK2V617F Mutational Status on Clinical and Laboratory Phenotype at Diagnosis and during Follow-up in Patients with Essential Thrombocythemia

BACKGROUND: Essential thrombocythemia (ET) is thought to derive from the transformation of a multipotent hematopoietic stem cell, but its molecular pathogenesis remains obscure. An acquired mutation in exon 14 of the Janus tyrosine kinase 2 gene (JAK2) leading to a valine –> phenylalanine change at position 617 (JAK2V617F) in the JH2 pseudokinase domain, has been described in Ph negative chronic myeloproliferative disorders (MPD). It can be found in approximately 95% of polycythemia vera (PV) and in approximately 50–60% of essential thrombocythemia (ET) or primary myelofibrosis. The impact of this mutation on clinical phenotype is still debated. We investigated the frequency of JAK2 mutation and its possible impact and correlation with clinical and laboratory features at diagnosis and during follow-up in ET patients (pts), screened for JAK2 mutational status, referred to our division between 1987 and 2008.METHODS and PATIENTS: JAK2V617F mutation analysis was performed on genomic DNA from bone marrow cells or peripheral blood granulocytes in 115 ET (49 males, 66 females) pts, using allele-specific PCR. Clinical and laboratory features were evaluated at diagnosis and during follow-up, in order to compare ET pts harbouring JAK2 mutation versus (vs) pts harbouring wildtype (WT) gene. For statistical analysis, data were processed using the Graph Pad PRISM 5 DEMO Software. Correlations between clinical variables and JAK2 V617F mutational status were tested for significance (p value < 0,05) by using non-parametric methods, in particular the chi-square test or Fisher's exact test (two by two table) for categorical nominal variables and the Mann-Whitney rank test for ordinal variables. The log-rank (Mantel-Cox) test applied to Kaplan-Meyer method was employed to estimate thrombotic risk and thrombotic event-free-survival (TEFS)RESULTS: 66 ET pts (57,4%) were JAK2V617 positive. JAK2 mutated pts were older (median age 59 vs 48 years, p = 0,0016) and presented at diagnosis significantly higher hemoglobin levels (Hb 14,3 g/dl vs 13,3 g/dl, p= 0,0027), higher hematocrit (Ht 43% vs 39,8%, p < 0,0001) and lower PLT count (PLT 725 vs 841 ×109/L, p = 0,005) respect to WT group. These PV-like features have also maintained during the course of disease, with statistical significance. No difference was observed in term of gender, white blood count, LDH, progression or entity of splenomegaly, and need of cytoreductive therapy between JAK2 mutated and WT ET pts. A highly significant increase of thrombotic complications was registered for JAK2 positive pts. Considering JAK2 WT ET as reference group, the relative risk (RR) of primary thrombotic event was 2,143 (95% CI: 1.053–4.360, p = 0,035) for JAK2 mutated pts (TEFS at 15 years of 60% in JAK2 mutated group vs 75% in WT group, respectively). Arterial events were more frequent than venous events without statistical difference between two ET groups. A trend of higher risk of recurrent thrombosis (p = 0,056) was also showed for JAK2 mutated respect to WT ET pts. There was no difference about the risk of haemorragic complications, time and incidence of evolution in myelofibrosis between JAK2 mutated or WT ET pts.CONCLUSION: In our population, 57,4% ET pts harbor JAK2V617F mutation. This mutation divides ET pts into two distinct subtypes. JAK2 mutated ET pts present older age and laboratory features at diagnosis and during follow-up, compatible with PV-like phenotype. An increased risk of thrombosis, at diagnosis and during the course of disease, has been showed in mutated ET group, in term of recurrent thrombosis too. These observations seem to confirm a phenotype more aggressive since the diagnosis in JAK2 mutated ET group. A possible biological continuum between JAK2 mutated ET and PV, or more in general between JAK2 positive ET and MPD may be supposed.

High prevalence of arterial thrombosis in JAK2 mutated essential thrombocythaemia: independence of the V617F allele burden

Approximately half of the patients with essential thrombocythaemia (ET) harbor the JAK2 V617F mutation. Despite a phenotypic mimicry of JAK2 V617F positive ET and polycythaemia vera (PV), the data on thromboembolic risk and correlation to JAK2 mutation status are ambiguous. On a strictly WHO defined ET cohort we evaluated possible clinical correlations to the JAK2 mutation status including a history of previous thrombosis. We used a highly sensitive quantitative real-time PCR (qPCR) assay for JAK2 V617F detection and allele burden quantification in a single institution study of 55 patients. A significantly increased prevalence of arterial thrombosis was recorded in JAK2 positive ET (p=0·001). There was no association between the mutational load and thrombosis. As compared to their JAK2 V617F negative counterparts, the JAK2 V617F positive patients had PV-like biochemical characteristics such as higher haemoglobin levels (p=0·02), lower platelet counts (p=0·002) and lower plasma EPO levels (p=0·04). The JAK2 V617F mutation per se but not the mutational load in patients with ET is associated with a PV-like phenotype and a higher prevalence of previous arterial thrombosis. This study adds further support to the contention of the JAK2 V617F mutation as a marker of increased risk of thrombosis.

Bone marrow histomorphology and JAK2 mutation status in essential thrombocythemia

A retrospective study of 38 essential thrombocythemia (ET) patients was conducted, reviewing bone marrow biopsies according to WHO criteria using a semiquantitative scoring system. Four patients did not fulfil the WHO criteria for a myeloproliferative disorder and one biopsy was insufficient for evaluation. 14 patients were reclassified as having prefibrotic idiopathic myelofibrosis (IMF), whilst the ET diagnosis was sustained in 19 patients. The individual bone marrow parameters of the reviewed diagnosis showed no correlation with JAK2 V617F mutation status, which was determined by a highly sensitive quantitative real-time PCR (qPCR) method. However, we could confirm previous findings of higher haemoglobin and lower platelet levels in the JAK2 V617F positive patients. Thus, the well-established phenotypic relationship of JAK2-positive ET and PV at the biochemical and molecular level was not recorded as regards bone marrow morphology according to the WHO criteria. Accordingly, the WHO concept of two distinct entities, ET and prefibrotic IMF, does not seem to fit the model of JAK2-positive ET as part of a biological continuum of JAK2 V617F-positive chronic myeloproliferative disorders.

Risk of thrombosis in patients with essential thrombocythemia and polycythemia vera according to JAK2 V617F mutation status

We compared the laboratory and clinical findings of 179 patients with essential thrombocythemia (ET) and 77 with polycythemia vera (PV) classified according to the presence of the JAK2 V617F mutation. A gradient was observed in laboratory values between patients with JAK2 wild-type ET, JAK2 V617F ET and PV (all of whom carried the JAK2 mutation). The rate of thrombotic complications in JAK2-positive ET patients was significantly higher than that in wild-type ET patients and not statistically different from that in PV patients.