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1.  Treatment and management of myelofibrosis in the era of JAK inhibitors 
Myelofibrosis (MF) can present as a primary disorder or evolve from polycythemia vera (PV) or essential thrombocythemia (ET) to post-PV MF or post-ET MF, respectively. MF is characterized by bone marrow fibrosis, splenomegaly, leukoerythroblastosis, extramedullary hematopoiesis, and a collection of debilitating symptoms. Until recently, the therapeutic options for patients with MF consisted of allogeneic hematopoietic stem cell transplant (alloHSCT), the use of cytoreductive agents (ie, hydroxyurea), splenectomy and splenic irradiation for treatment of splenomegaly, and management of anemia with transfusions, erythropoiesis-stimulating agents (ESAs), androgens, and immunomodulatory agents. However, with increased understanding of the pathogenesis of MF resulting from dysregulated Janus kinase (JAK) signaling, new targeted JAK inhibitor therapies, such as ruxolitinib, are now available. The purpose of this article is to review the clinical features of MF, discuss the use and future of JAK inhibitors, reassess when and how to use conventional MF treatments in the context of JAK inhibitors, and provide a perspective on the future of MF treatment.
doi:10.2147/BTT.S34942
PMCID: PMC3753053  PMID: 23990704
myelofibrosis; ruxolitinib; JAK inhibitor
2.  Disseminated tuberculosis in a patient treated with a JAK2 selective inhibitor: a case report 
BMC Research Notes  2012;5:552.
Background
Primary myelofibrosis is a myeloproliferative disorder characterized by bone marrow fibrosis, abnormal cytokine expression, splenomegaly and anemia. The activation of JAK2 and the increased levels of circulating proinflammatory cytokines seem to play an important role in the pathogenesis of myelofibrosis. Novel therapeutic agents targeting JAKs have been developed for the treatment of myeloproliferative disorders. Ruxolitinib (INCB018424) is the most recent among them.
Case presentation
To our knowledge, there is no evidence from clinical trials of an increased risk of tuberculosis during treatment with JAK inhibitors. Here we describe the first case of tuberculosis in a patient treated with Ruxolitinib, a male with a 12-year history of chronic idiopathic myelofibrosis admitted to our Institute because of fever, night sweats, weight loss and an enlarging mass in the left inguinal area for two months.
Conclusion
Treatment with Ruxolitinib may have triggered the reactivation of latent tuberculosis because of an inhibition of Th1 response. Our case highlights the importance of an accurate screening for latent tuberculosis before starting an anti-JAK 2 treatment.
doi:10.1186/1756-0500-5-552
PMCID: PMC3515333  PMID: 23039051
Tuberculosis; Myelofibrosis; Ruxolitinib
3.  Targeting hedgehog signaling in myelofibrosis and other hematologic malignancies 
Treatment of myelofibrosis (MF), a BCR-ABL–negative myeloproliferative neoplasm, is challenging. The only current potentially curative option, allogeneic hematopoietic stem cell transplant, is recommended for few patients. The remaining patients are treated with palliative therapies to manage MF-related anemia and splenomegaly. Identification of a mutation in the Janus kinase 2 (JAK2) gene (JAK2 V617F) in more than half of all patients with MF has prompted the discovery and clinical development of inhibitors that target JAK2. Although treatment with JAK2 inhibitors has been shown to improve symptom response and quality of life in patients with MF, these drugs do not alter the underlying disease; therefore, novel therapies are needed. The hedgehog (Hh) signaling pathway has been shown to play a role in normal hematopoiesis and in the tumorigenesis of hematologic malignancies. Moreover, inhibitors of the Hh pathway have been shown to inhibit growth and self-renewal capacity in preclinical models of MF. In a mouse model of MF, combined inhibition of the Hh and JAK pathways reduced JAK2 mutant allele burden, reduced bone marrow fibrosis, and reduced white blood cell and platelet counts. Preliminary clinical data also suggest that inhibition of the Hh pathway, alone or in combination with JAK2 inhibition, may enable disease modification in patients with MF. Future studies, including one combining the Hh pathway inhibitor sonidegib and the JAK2 inhibitor ruxolitinib, are underway in patients with MF and will inform whether this combination approach can lead to true disease modification.
doi:10.1186/1756-8722-7-18
PMCID: PMC3975838  PMID: 24598114
Myelofibrosis; Targeted therapy; Hedgehog pathway inhibitors; Janus kinase inhibitors
4.  Biology and Clinical Management of Myeloproliferative Neoplasms and Development of the JAK Inhibitor Ruxolitinib 
Current Medicinal Chemistry  2012;19(26):4399-4413.
Myeloproliferative neoplasms (MPN) are debilitating stem cell-derived clonal myeloid malignancies. Conventional treatments for the BCR-ABL1-negative MPN including polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF) have, so far, been unsatisfactory. Following the discovery of dysregulated JAK-STAT signaling in patients with MPN, many efforts have been directed toward the development of molecularly targeted therapies, including inhibitors of JAK1 and JAK2. Ruxolitinib (previously known as INCB018424; Incyte Corporation, Wilmington, Delaware, USA) is a rationally designed potent oral JAK1 and JAK2 inhibitor that has undergone clinical trials in patients with PV, ET, and PMF. Ruxolitinib was approved on November 16, 2011 by the United States Food and Drug Administration for the treatment of intermediate or high-risk myelofibrosis (MF), including patients with PMF, post-PV MF, and post-ET MF. In randomized phase III studies, ruxolitinib treatment resulted in significant and durable reductions in splenomegaly and improvements in disease-related symptoms in patients with MF compared with placebo or best available therapy. The most common adverse events were anemia and thrombocytopenia, which were manageable and rarely led to discontinuation. This review addresses the cellular and molecular biology, and the clinical management of MPN.
doi:10.2174/092986712803251511
PMCID: PMC3480698  PMID: 22830345
Essential thrombocythemia; janus kinase; JAK inhibitor; JAK-STAT; myelofibrosis; myeloproliferative neoplasms; polycythemia vera; primary myelofibrosis; quality of life; ruxolitinib; splenomegaly; symptoms.
5.  Ruxolitinib for the treatment of myelofibrosis: its clinical potential 
Ruxolitinib is an orally bioavailable, selective Janus kinase (JAK) 1 and 2 inhibitor approved for the treatment of myelofibrosis (MF), a bone marrow disease in which the JAK pathway is dysregulated, leading to impaired hematopoiesis and immune function. By inhibiting JAK1 and JAK2, ruxolitinib modulates cytokine-stimulated intracellular signaling. In a phase II clinical trial in patients with MF, ruxolitinib recipients exhibited durable reductions in spleen size, reductions in circulating pro-inflammatory cytokines, improvements in physical activity, weight gain, and alleviation of symptoms (including constitutional symptoms) in patients with and without JAK2 mutation. These findings were confirmed by two phase III clinical MF studies, in which a greater proportion of ruxolitinib recipients achieved a spleen volume reduction of ≥35% from baseline at week 24, compared with placebo in one study (41.9% versus 0.7%; P < 0.0001) and with best available therapy in the other (31.9% versus 0%; P < 0.0001). Alleviation of MF symptoms and improvements in quality of life were also significantly greater in ruxolitinib recipients. Overall survival of patients treated with ruxolitinib was significantly longer than of those receiving the placebo. Owing to risks of potentially serious adverse effects, eg, myelosuppression, ruxolitinib should be used under close physician supervision. Longer follow-up of the phase III MF studies is needed to reach firm conclusions regarding ruxolitinib’s capacity to modify the natural disease course.
doi:10.2147/TCRM.S23277
PMCID: PMC3295626  PMID: 22399854
myelofibrosis; JAK2 inhibitor; ruxolitinib
6.  Comprehensive review of JAK inhibitors in myeloproliferative neoplasms 
Myeloproliferative neoplasms (MPNs) are clonal hematopoietic stem-cell disorders, characterized phenotypically by the abnormal accumulation of mature-appearing myeloid cells. Polycythemia vera, essential thrombocythemia, primary myelofibrosis (also known as ‘BCR-ABL1-negative’ MPNs), and chronic myeloid leukemia (CML) are the primary types of MPNs. After the discovery of the BCR-ABL1 fusion protein in CML, several oncogenic tyrosine kinases have been identified in ‘BCR-ABL1-negative’ MPNs, most importantly, JAK2V617F mutation. The similarity in the clinical characteristics of the BCR-ABL1-negative MPN patients along with the prevalence of the Janus kinase mutation in this patient population provided a strong rationale for the development of a new class of pharmacologic inhibitors that target this pathway. The first of its class, ruxolitinib, has now been approved by the food and drug administration (FDA) for the management of patients with intermediate- to high-risk myelofibrosis. Ruxolitinib provides significant and sustained improvements in spleen related and constitutional symptoms secondary to the disease. Although noncurative, ruxolitinib represents a milestone in the treatment of myelofibrosis patients. Other types of JAK2 inhibitors are being tested in various clinical trials at this point and may provide better efficacy data and safety profile than its predecessor. In this article, we comprehensively reviewed and summarized the available preclinical and clinical trials pertaining to JAK inhibitors.
doi:10.1177/2040620712461047
PMCID: PMC3629759  PMID: 23610611
primary myelofibrosis; polycythemia vera; essential thrombocythemia; Janus kinase 2
7.  Splenomegaly in myelofibrosis—new options for therapy and the therapeutic potential of Janus kinase 2 inhibitors 
Splenomegaly is a common sign of primary myelofibrosis (PMF), post-polycythemia vera myelofibrosis (post-PV MF), and post-essential thrombocythemia myelofibrosis (post-ET MF) that is associated with bothersome symptoms, which have a significant negative impact on patients’ quality of life. It may also be present in patients with advanced polycythemia vera (PV) or essential thrombocythemia (ET). Until recently, none of the therapies used to treat MF were particularly effective in reducing splenomegaly. The discovery of an activating Janus kinase 2 (JAK2) activating mutation (JAK2V617F) that is present in almost all patients with PV and in about 50-60 % of patients with ET and PMF led to the initiation of several trials investigating the clinical effectiveness of various JAK2 (or JAK1/JAK2) inhibitors for the treatment of patients with ET, PV, and MF. Some of these trials have documented significant clinical benefit of JAK inhibitors, particularly in terms of regression of splenomegaly. In November 2011, the US Food and Drug Administration approved the use of the JAK1- and JAK2-selective inhibitor ruxolitinib for the treatment of patients with intermediate or high-risk myelofibrosis, including PMF, post-PV MF, and post-ET MF. This review discusses current therapeutic options for splenomegaly associated with primary or secondary MF and the treatment potential of the JAK inhibitors in this setting.
doi:10.1186/1756-8722-5-43
PMCID: PMC3464878  PMID: 22852872
JAK2 inhibitor; Myeloproliferative neoplasms; Myelofibrosis; JAK2V617F mutation; Splenomegaly
8.  Management of cytopenias in patients with myelofibrosis treated with ruxolitinib and effect of dose modifications on efficacy outcomes 
OncoTargets and therapy  2013;7:13-21.
Purpose
Ruxolitinib is an oral Janus kinase (JAK) 1/JAK2 inhibitor approved in the US for the treatment of intermediate-or high-risk myelofibrosis (MF). Because thrombopoietin and erythropoietin signal through JAK2, dose-dependent cytopenias are expected with treatment. In the COMFORT-I (COntrolled Myelofibrosis study with ORal JAK inhibitor Treatment I) trial, these cytopenias were effectively managed with dose adjustments. These analyses were conducted to evaluate the relationship between ruxolitinib titrated doses and changes in platelet count and hemoglobin level as well as efficacy measures.
Patients and methods
COMFORT-I was a randomized, placebo-controlled trial in 309 patients with intermediate-2 or high-risk MF and a platelet count ≥100 × 109/L. Ruxolitinib starting doses were 15 and 20 mg twice daily (bis in die [BID]) for patients with baseline platelet counts of 100–200 × 109/L and >200 × 109/L, respectively. Percentage changes from baseline to week 24 in spleen volume and MF-related symptoms were assessed in subgroups defined by final titrated dose (average daily dose during weeks 21 to 24).
Results
The median final titrated doses for patients starting at doses of 15 and 20 mg BID were 10 and 20 mg BID, respectively, at week 24. Most dose reductions occurred in the first 8–12 weeks of treatment and coincided with decreases in platelet count and hemoglobin level. Subsequently, platelet counts stabilized and hemoglobin levels gradually returned to near baseline levels (red blood cell transfusion rates followed a similar trend). Final titrated doses of ≥10 mg BID were associated with clinically meaningful improvements in MF-related symptoms that were comparable across doses, while marginally greater reductions in spleen volume were observed at higher doses.
Conclusion
This COMFORT-I analysis shows that dose-dependent cytopenias were effectively managed with ruxolitinib dose adjustments, and titrated doses of ≥10 mg BID were associated with clinically meaningful reductions in spleen volume and symptom improvement at week 24.
doi:10.2147/OTT.S53348
PMCID: PMC3869911  PMID: 24368888
COMFORT-I; dose titration; JAK2 inhibitor; myelofibrosis; ruxolitinib; treatment-related cytopenias
9.  JAK2 mutants (e.g., JAK2V617F) and their importance as drug targets in myeloproliferative neoplasms 
JAK-STAT  2013;2(3):e25025.
The Janus kinase 2 (JAK2) mutant V617F and other JAK mutants are found in patients with myeloproliferative neoplasms and leukemias. Due to their involvement in neoplasia and inflammatory disorders, Janus kinases are promising targets for kinase inhibitor therapy. Several small-molecule compounds are evaluated in clinical trials for myelofibrosis, and ruxolitinib (INCB018424, Jakafi®) was the first Janus kinase inhibitor to receive clinical approval. In this review we provide an overview of JAK2V617F signaling and its inhibition by small-molecule kinase inhibitors. In addition, myeloproliferative neoplasms are discussed regarding the role of JAK2V617F and other mutant proteins of possible relevance. We further give an overview about treatment options with special emphasis on possible combination therapies.
doi:10.4161/jkst.25025
PMCID: PMC3772115  PMID: 24069563
JAK2V617F; myeloproliferative neoplasms; polycythemia vera; essential thrombocythemia; primary myelofibrosis
10.  Molecular Pathogenesis and Therapy of Polycythemia Induced in Mice by JAK2 V617F 
PLoS ONE  2006;1(1):e18.
Background
A somatic activating mutation (V617F) in the JAK2 tyrosine kinase was recently discovered in the majority of patients with polycythemia vera (PV), and some with essential thrombocythemia (ET) and chronic idiopathic myelofibrosis. However, the role of mutant JAK2 in disease pathogenesis is unclear.
Methods and Findings
We expressed murine JAK2 WT or V617F via retroviral bone marrow transduction/transplantation in the hematopoietic system of two different inbred mouse strains, Balb/c and C57Bl/6 (B6). In both strains, JAK2 V617F, but not JAK2 WT, induced non-fatal polycythemia characterized by increased hematocrit and hemoglobin, reticulocytosis, splenomegaly, low plasma erythropoietin (Epo), and Epo-independent erythroid colonies. JAK2 V617F also induced leukocytosis and neutrophilia that was much more prominent in Balb/c mice than in B6. Platelet counts were not affected in either strain despite expression of JAK2 V617F in megakaryocytes and markedly prolonged tail bleeding times. The polycythemia tended to resolve after several months, coincident with increased spleen and marrow fibrosis, but was resurrected by transplantation to secondary recipients. Using donor mice with mutations in Lyn, Hck, and Fgr, we demonstrated that the polycythemia was independent of Src kinases. Polycythemia and reticulocytosis responded to treatment with imatinib or a JAK2 inhibitor, but were unresponsive to the Src inhibitor dasatinib.
Conclusions
These findings demonstrate that JAK2 V617F induces Epo-independent expansion of the erythroid lineage in vivo. The fact that the central erythroid features of PV are recapitulated by expression of JAK2 V617F argues that it is the primary and direct cause of human PV. The lack of thrombocytosis suggests that additional events may be required for JAK2 V617F to cause ET, but qualitative platelet abnormalities induced by JAK2 V617F may contribute to the hemostatic complications of PV. Despite the role of Src kinases in Epo signaling, our studies predict that Src inhibitors will be ineffective for therapy of PV. However, we provide proof-of-principle that a JAK2 inhibitor should have therapeutic effects on the polycythemia, and perhaps myelofibrosis and hemostatic abnormalities, suffered by MPD patients carrying the JAK2 V617F mutation.
doi:10.1371/journal.pone.0000018
PMCID: PMC1762384  PMID: 17183644
11.  The evolving treatment paradigm in myelofibrosis 
Leukemia & Lymphoma  2012;54(2):242-251.
Myelofibrosis (MF) is a BCR–ABL1-negative myeloproliferative neoplasm diagnosed de novo or developed from essential thrombocythemia (ET) or polycythemia vera (PV). Average survival of a patient with MF is 5–7 years. Disease complications include fatigue, early satiety, pruritus, painful splenic infarcts, infections and leukemic transformation. Allogeneic hematopoietic stem cell transplant (HSCT) is the only potentially curative option for MF, but carries a risk of treatment-related mortality and is reserved for the few high-risk patients fit enough to endure the procedure. Other traditional therapies are palliative and supported by few randomized, controlled trials; thus, novel treatment strategies are needed. Discovery of the Janus kinase 2 (JAK2) gain-of-function mutation, JAK2V617F, in the majority (50–60%) of patients with MF led to increased understanding of the biology underlying MF and the development of JAK2 inhibitors to treat MF. Recent Food and Drug Administration (FDA) approval of the first JAK2 inhibitor, ruxolitinib, signaled a new era for treatment of MF. Additional JAK2 inhibitors, such as SAR302503, may become commercially available in the near future, and their distinct pharmacologic and efficacy profiles will help determine their use across the patient population. Data on JAK2 inhibitors, their role in an evolving treatment paradigm, and future directions for treatment of MF are discussed.
doi:10.3109/10428194.2012.710905
PMCID: PMC3545544  PMID: 22793267
Dysplasias; myeloid leukemias; Janus kinase 2 (JAK2); JAK2V617F; myelofibrosis; myeloproliferative disorders; signaling therapies
12.  Molecular approach to diagnose BCR/ABL negative chronic myeloproliferative neoplasms 
Chronic myeloproliferative neoplasms arise from clonal proliferation of hematopoietic stem cells. According to the World Health Organization myeloproliferative neoplasms are classified as: chronic myelogenous leukemia, polycythemia vera, essential thrombocythemia, primary myelofibrosis, chronic neutrophilic leukemia, chronic eosinophilic leukemia, hypereosinophilic syndrome, mast cell disease, and unclassifiable myeloproliferative neoplasms. In the revised 2008 WHO diagnostic criteria for myeloproliferative neoplasms, mutation screening for JAK2V617F is considered a major criterion for polycythemia vera diagnosis and also for essential thrombocythemia and primary myelofibrosis, the presence of this mutation represents a clonal marker. There are currently two hypotheses explaining the role of the JAK2V617F mutation in chronic myeloproliferative neoplasms. According to these theories, the mutation plays either a primary or secondary role in disease development. The discovery of the JAK2V617F mutation has been essential in understanding the genetic basis of chronic myeloproliferative neoplasms, providing some idea on how a single mutation can result in three different chronic myeloproliferative neoplasm phenotypes. But there are still some issues to be clarified. Thus, studies are still needed to determine specific molecular markers for each subtype of chronic myeloproliferative neoplasm.
doi:10.5581/1516-8484.20110079
PMCID: PMC3415756  PMID: 23049320
Myelodysplastic-Myeloproliferative diseases; Hematologic neoplasm; Mutation; AK2V617F
13.  Janus kinase Inhibitors in autoimmune diseases 
Annals of the rheumatic diseases  2013;72(0 2):ii111-ii115.
Biological therapies directed at proinflammatory cytokines have irrevocably changed the landscape of treatment of rheumatoid arthritis (RA) and other autoimmune diseases. With the advances in our knowledge in cytokine signaling, the question emerges whether targeting intracellular signaling might also be a safe and efficacious strategy. Janus kinases or Jaks are critical for a large family of cytokines and the first Jak inhibitor has been approved by the FDA for the treatment of myelofibrosis. Late phase clinical trials have been completed for another Jakinib in RA. It is therefore timely to consider this new category of drugs and reflect on their potential roles, present and future, in the treatment of RA and related disorders.
doi:10.1136/annrheumdis-2012-202576
PMCID: PMC3616338  PMID: 23532440
14.  Erlotinib Effectively Inhibits JAK2V617F Activity and Polycythemia Vera Cell Growth 
The Journal of biological chemistry  2006;282(6):3428-3432.
JAK2V617F, a mutant of tyrosine kinase JAK2, is found in most patients with polycythemia vera (PV) and a substantial proportion of patients with idiopathic myelofibrosis or essential thrombocythemia. The JAK2 mutant displays a much increased kinase activity and generates a PV-like phenotype in mouse bone marrow transplant models. This study shows that the anti-cancer drug erlotinib (Traceva™) is a potent inhibitor of JAK2V617F activity. In vitro colony culture assays revealed that erlotinib at micro-molar concentrations effectively suppresses the growth and expansion of PV hematopoietic progenitor cells while having little effect on normal cells. Furthermore, JAK2V617F-positive cells from PV patients show greater susceptibility to the inhibitor than their negative counterparts. Similar inhibitory effects were found with the JAK2V617F-positive human erythroleukemia HEL cell line. These data suggest that erlotinib may be used for treatment of JAK2V617F-positive PV and other myeloproliferative disorders.
doi:10.1074/jbc.C600277200
PMCID: PMC2096634  PMID: 17178722
15.  JAK Inhibitors and other Novel Agents in Myeloproliferative Neoplasms: Are We Hitting the Target? 
The discovery of somatic mutations in the JAK-STAT signaling pathway was a major breakthrough in our understanding of the molecular pathogenesis of the myeloproliferative neoplasms (MPNs) polycythemia vera, essential thrombocytosis, and primary myelofibrosis. This finding led to the development of small molecule inhibitors targeting Janus kinase (JAK) 2 and other JAK family members. Currently, there are a number of research and clinical trials ongoing with JAK inhibitors. While the appeal of inhibiting JAK2 is clear, studies to date suggest that JAK2 inhibitor monotherapy might not be sufficient to cause reductions in disease allele burden in MPN patients. There is compelling evidence that JAK inhibitors are improving symptoms and therefore quality of life for patients. It will be important to investigate the efficacy of JAK inhibitors in preclinical and clinical studies to better understand their effects, while at the same time pursuing alternative therapies which might offer benefit to MPN patients alone and in combination with JAK inhibitors.
doi:10.1177/2040620711410095
PMCID: PMC3573410  PMID: 23556090
JAK kinases; myeloproliferative disorder; JAK inhibitor; essential thrombocytosis; polycythemia vera; myelofibrosis
16.  CXCR4-Independent Rescue of the Myeloproliferative Defect of the Gata1low Myelofibrosis Mouse Model by Aplidin® 
Journal of cellular physiology  2010;225(2):490-499.
The discovery of JAK2 mutations in Philadelphia-negative myeloproliferative neoplasms has prompted investigators to evaluate mutation-targeted treatments to restore hematopoietic cell functions in these diseases. However, the results of the first clinical trials with JAK2 inhibitors are not as promising as expected, prompting a search for additional drugable targets to treat these disorders. In this paper, we used the hypomorphic Gata1low mouse model of primary myelofibrosis (PMF), the most severe of these neoplasms, to test the hypothesis that defective marrow hemopoiesis and development of extramedullary hematopoiesis in myelofibrosis is due to insufficient p27Kip 1 activity and is treatable by Aplidin®, a cyclic depsipeptide that activates p27 kip 1 in several cancer cells. Aplidin® restored expression of Gata1 and p27Kip 1 in Gata1 low hematopoietic cells, proliferation of marrow progenitor cells in vitro and maturation of megakaryocytes in vivo (reducing TGF-β/VEGF levels released in the microenvironment by immature Gata1 low megakaryocytes). Microvessel density, fibrosis, bone growth, and marrow cellularity were normal in Aplidin®-treated mice and extramedullary hematopoiesis did not develop in liver although CXCR4 expression in Gata1low progenitor cells remained low. These results indicate that Aplidin® effectively alters the natural history of myelofibrosis in Gata1low mice and suggest this drug as candidate for clinical evaluation in PMF.
doi:10.1002/jcp.22228
PMCID: PMC3780594  PMID: 20458749
17.  Symptom burden and splenomegaly in patients with myelofibrosis in the United States: a retrospective medical record review 
Cancer Medicine  2013;2(6):889-898.
Myelofibrosis (MF) is a clonal hematopoietic malignancy characterized by constitutional and localized symptoms, progressive splenomegaly, bone marrow fibrosis, and cytopenias. Although MF is well studied, few studies exist regarding its symptomatic burden in routine clinical practice. This study aimed to characterize symptoms and other clinical features of MF among patients in the United States. We conducted a retrospective medical record review of adult patients with an MF diagnosis between 1 January 2005 and 31 March 2010, stratified by the presence of palpable splenomegaly. Eligible patients had 12 months or more of follow-up after diagnosis (or after detection of splenomegaly, if present) unless death occurred. Demographic and clinical characteristics, MF-related symptoms, and treatments were reported by treating physicians. We report on 180 MF patients: 102 with splenomegaly, 78 without. Median age was 66 years, 63% were male, and 82% had intermediate-2 or high-risk MF (International Prognostic Scoring System). Fatigue was reported by ∼85% of patients; weight loss, night sweats, and fever (any grade) were each reported by 50% or more of patients. Generalized abdominal pain, left subcostal pain, and early satiety occurred more frequently among patients with splenomegaly. Multiple symptoms were reported by 95% of patients. Common comorbidities were hypertension, diabetes, and chronic pulmonary disease. Symptoms are common in MF patients, regardless of the presence of palpable splenomegaly. Careful assessment of symptom burden is an important aspect of the clinical evaluation of patients with MF.
doi:10.1002/cam4.136
PMCID: PMC3892393  PMID: 24403262
Comorbidities; myelofibrosis; myeloproliferative neoplasm; splenomegaly; symptoms
18.  Serious Adverse Events During Ruxolitinib Treatment Discontinuation in Patients With Myelofibrosis 
Mayo Clinic Proceedings  2011;86(12):1188-1191.
Ruxolitinib (INCB018424) is a JAK1 and JAK2 inhibitor recently evaluated for the treatment of myelofibrosis (MF) in early- and advanced-phase clinical trials. In 2 recent communications that focused on short-term and long-term ruxolitinib treatment outcome, respectively, the drug was shown to be effective in controlling constitutional symptoms and splenomegaly but was also associated with important adverse effects, including moderate to severe thrombocytopenia and anemia. The most recent of the 2 communications focused on 51 Mayo Clinic patients who participated in the original phase 1/2 ruxolitinib clinical trial and highlighted a high treatment discontinuation rate (92% after a median time of 9.2 months), primarily for loss of treatment benefit but also because of drug-associated adverse effects. The report also discussed the occurrence of sometimes severe withdrawal symptoms during ruxolitinib treatment discontinuation. This “ruxolitinib withdrawal syndrome” was characterized by acute relapse of disease symptoms, accelerated splenomegaly, worsening of cytopenias, and occasional hemodynamic decompensation, including a septic shocklike syndrome. In the current sponsor-independent analysis, we describe the details of these events in 5 severely affected cases (11%) among 47 Mayo Clinic patients with MF in whom ruxolitinib therapy had been discontinued. Our experience calls for full disclosure of the ruxolitinib withdrawal syndrome to patients with MF before initiating ruxolitinib therapy, and treatment discontinuation must be done under close physician supervision and preferably in a tapering schedule.
doi:10.4065/mcp.2011.0518
PMCID: PMC3228619  PMID: 22034658
19.  Identification of a novel inhibitor of JAK2 tyrosine kinase by structure-based virtual screening 
Janus kinase 2 (JAK2) plays a crucial role in the pathomechanism of myeloproliferative disorders and hematologic malignancies. A somatic mutation of JAK2 (Val617Phe) was previously shown to occur in 98% of patients with polycythemia vera and 50% of patients with essential thrombocythemia and primary myelofibrosis. Thus, effective JAK2 kinase inhibitors may be of significant therapeutic importance. Here, we applied a structure-based virtual screen to identify novel JAK2 inhibitors. One JAK2 inhibitor in particular, G6, demonstrated remarkable potency as well as specificity, which makes it as a potential lead candidate against diseases related to elevated JAK2 tyrosine kinase activity.
doi:10.1016/j.bmcl.2009.04.138
PMCID: PMC2812898  PMID: 19447617
Janus kinase 2; Virtual screening; Inhibitor; Pharmacological evaluation
20.  Effect of NS-018, a selective JAK2V617F inhibitor, in a murine model of myelofibrosis 
Blood Cancer Journal  2014;4(1):e174-.
A single somatic mutation, V617F, in Janus kinase 2 (JAK2) is one of the causes of myeloproliferative neoplasms (MPNs), including primary myelofibrosis, and the JAK2V617F mutant kinase is a therapeutic target in MPN. However, inhibition of wild-type (WT) JAK2 can decrease the erythrocyte or platelet (PLT) count. Our selective JAK2 inhibitor, NS-018, suppressed the growth of Ba/F3 cells harboring JAK2V617F more strongly than that of cells harboring WT JAK2. The 4.3-fold JAK2V617F selectivity of NS-018 is higher than the 1.0- to 2.9-fold selectivity of seven existing JAK2 inhibitors. NS-018 also inhibited erythroid colony formation in JAK2V617F transgenic mice at significantly lower concentrations than in WT mice. In keeping with the above results, in a JAK2V617F bone marrow transplantation mouse model with a myelofibrosis-like disease, NS-018 reduced leukocytosis and splenomegaly, improved bone marrow fibrosis and prolonged survival without decreasing the erythrocyte or PLT count in the peripheral blood. By exploring the X-ray co-crystal structure of NS-018 bound to JAK2, we identified unique hydrogen-bonding interactions between NS-018 and Gly993 as a plausible explanation for its JAK2V617F selectivity. These results suggest that NS-018 will have therapeutic benefit for MPN patients through both its efficacy and its reduced hematologic adverse effects.
doi:10.1038/bcj.2013.73
PMCID: PMC3913942  PMID: 24413068
JAK2; V617F; myelofibrosis; kinase inhibitor; NS-018
21.  Myelofibrosis-associated complications: pathogenesis, clinical manifestations, and effects on outcomes 
Myelofibrosis (MF) is a rare chronic BCR-ABL1 (breakpoint cluster region-Abelson murine leukemia viral oncogene homologue 1)-negative myeloproliferative neoplasm characterized by progressive bone marrow fibrosis, inefficient hematopoiesis, and shortened survival. The clinical manifestations of MF include splenomegaly, consequent to extramedullary hematopoiesis, cytopenias, and an array of potentially debilitating abdominal and constitutional symptoms. Dysregulated Janus kinase (JAK)-signal transducer and activator of transcription signaling underlies secondary disease-associated effects in MF, such as myeloproliferation, bone marrow fibrosis, constitutional symptoms, and cachexia. Common fatal complications of MF include transformation to acute leukemia, thrombohemorrhagic events, organ failure, and infections. Potential complications from hepatosplenomegaly include portal hypertension and variceal bleeding, whereas extramedullary hematopoiesis outside the spleen and liver – depending on the affected organ – may result in intracranial hypertension, spinal cord compression, pulmonary hypertension, pleural effusions, lymphadenopathy, skin lesions, and/or exacerbation of abdominal symptoms. Although allogeneic stem cell transplantation is the only potentially curative therapy, it is suitable for few patients. The JAK1/JAK2 inhibitor ruxolitinib is effective in improving splenomegaly, MF-related symptoms, and quality-of-life measures. Emerging evidence that ruxolitinib may be associated with a survival benefit in intermediate- or high-risk MF suggests the possibility of a disease-modifying effect. Consequently, ruxolitinib could provide a treatment backbone to which other (conventional and novel) therapies may be added for the prevention and effective management of specific MF-associated complications.
doi:10.2147/IJGM.S51800
PMCID: PMC3912063  PMID: 24501543
extramedullary hematopoiesis; JAK inhibitor; myelofibrosis; myeloproliferative neoplasm; ruxolitinib
22.  JAK2 V617F, MPL W515L and JAK2 Exon 12 Mutations in Chinese Patients with Primary Myelofibrosis 
Objective
JAK2 V617F, MPL W515L and JAK2 exon 12 mutations are novel acquired mutations that induce constitutive cytokine-independent activation of the JAK-STAT pathway in myeloproliferative disorders (MPD). The discovery of these mutations provides novel mechanism for activation of signal transduction in hematopoietic malignancies. This research was to investigate their prevalence in Chinese patients with primary myelofibrosis (PMF).
Methods
We introduced allele-specific PCR (AS-PCR) combined with sequence analysis to simultaneously screen JAK2 V617F, MPL W515L and JAK2 exon 12 mutations in 30 patients with PMF.
Results
Fifteen PMF patients (50.0%) carried JAK2 V617F mutation, and only two JAK2 V617F-negative patients (6.7%) harbored MPL W515L mutation. None had JAK2 exon 12 mutations. Furthermore, these three mutations were not detected in 50 healthy controls.
Conclusion
MPL W515L and JAK2 V617F mutations existed in PMF patients but JAK2 exon 12 mutations not. JAK2 V617F and MPL W515L and mutations might contribute to the primary molecular pathogenesis in patients with PMF.
doi:10.1007/s11670-012-0072-4
PMCID: PMC3555257  PMID: 23359764
Primary myelofibrosis; JAK2 V617F; MPL W515L; JAK2 exon 12; mutation
23.  Differential Biological Activity of Disease-Associated JAK2 Mutants 
FEBS letters  2011;585(7):1007-1013.
The JAK2V617F mutation has been identified in most patients with myeloproliferative neoplasms (MPNs), including polycythemia vera, essential thrombocythemia and primary myelofibrosis. Although JAK2V617F is the predominant allele associated with MPNs, other activating JAK2 alleles (such as K539L, T875N) also have been identified in distinct MPNs. The basis for the differences in the in vivo effects of different JAK2 alleles remains unclear. We have characterized three different classes of disease-associated JAK2 mutants (JAK2V617F, JAK2K539L and JAK2T875N) and found significant differences in biochemical, signaling and transforming properties among these different classes of JAK2 mutants.
doi:10.1016/j.febslet.2011.02.032
PMCID: PMC3070755  PMID: 21362419
24.  MPLW515L Is a Novel Somatic Activating Mutation in Myelofibrosis with Myeloid Metaplasia  
PLoS Medicine  2006;3(7):e270.
Background
The JAK2V617F allele has recently been identified in patients with polycythemia vera (PV), essential thrombocytosis (ET), and myelofibrosis with myeloid metaplasia (MF). Subsequent analysis has shown that constitutive activation of the JAK-STAT signal transduction pathway is an important pathogenetic event in these patients, and that enzymatic inhibition of JAK2V617F may be of therapeutic benefit in this context. However, a significant proportion of patients with ET or MF are JAK2V617F-negative. We hypothesized that activation of the JAK-STAT pathway might also occur as a consequence of activating mutations in certain hematopoietic-specific cytokine receptors, including the erythropoietin receptor (EPOR), the thrombopoietin receptor (MPL), or the granulocyte-colony stimulating factor receptor (GCSFR).
Methods and Findings
DNA sequence analysis of the exons encoding the transmembrane and juxtamembrane domains of EPOR, MPL, and GCSFR, and comparison with germline DNA derived from buccal swabs, identified a somatic activating mutation in the transmembrane domain of MPL (W515L) in 9% (4/45) of JAKV617F-negative MF. Expression of MPLW515L in 32D, UT7, or Ba/F3 cells conferred cytokine-independent growth and thrombopoietin hypersensitivity, and resulted in constitutive phosphorylation of JAK2, STAT3, STAT5, AKT, and ERK. Furthermore, a small molecule JAK kinase inhibitor inhibited MPLW515L-mediated proliferation and JAK-STAT signaling in vitro. In a murine bone marrow transplant assay, expression of MPLW515L, but not wild-type MPL, resulted in a fully penetrant myeloproliferative disorder characterized by marked thrombocytosis (Plt count 1.9–4.0 × 10 12/L), marked splenomegaly due to extramedullary hematopoiesis, and increased reticulin fibrosis.
Conclusions
Activation of JAK-STAT signaling via MPLW515L is an important pathogenetic event in patients with JAK2V617F-negative MF. The bone marrow transplant model of MPLW515L-mediated myeloproliferative disorders (MPD) exhibits certain features of human MF, including extramedullary hematopoiesis, splenomegaly, and megakaryocytic proliferation. Further analysis of positive and negative regulators of the JAK-STAT pathway is warranted in JAK2V617F-negative MPD.
Editors' Summary
Background.
Myelofibrosis with myeloid metaplasia (MF) is one of a group of chronic blood disorders, known as chronic myeloproliferative disorders. These disorders sometimes turn into acute leukemia. The main abnormality in myelofibrosis is for the bone marrow to become filled with fibrous (scar) tissue (hence the name myelofibrosis), which stops it from producing normal blood cells efficiently. In addition, the white blood cells that remain are abnormal (that is, metaplastic). The clinical effect of these abnormalities are that patients are anemic (they have low numbers of red cells), are more likely to get infections because of the abnormal white cells which cannot fight infections normally, and may bleed more easily because of a lack of the platelets that help the blood to clot. Scientists who study this disorder believe that the disease starts from just one abnormal cell, which divides to replace all the other cells—that is, all the abnormal cells are part of one clone.
Why Was This Study Done?
In two similar diseases, polycythemia vera (in which the bone marrow produces too many red blood cells) and essential thrombocytosis (in which the bone marrow produces too many platelets), and in some patients with MF, scientists have found genetic changes which seem to trigger these diseases. However, there are some patients with MF in which no abnormal gene has been found. The scientists here wanted to look at other genes to see if they could find any changes that might trigger MF.
What Did the Researchers Do and Find?
They decoded the DNA sequence of three genes that are known to be involved in how blood cells develop for 45 patients with MF. They looked at DNA from white blood cells, and also from normal cheek cells for comparison. They found that in four of the 45 patients the DNA in the bone marrow, but not the cheek, carried a mutation in a gene for the thrombopoietin receptor (also called MPL). This gene is necessary for the cells that make platelets to grow correctly. The mutation was not present in any samples from patients with diseases related to MF, nor in 270 normal samples. The mutation that was identified was at position 515 in the MPL gene sequence, hence the name MPLW515L—the W and the L are the shorthand way of indicating exactly which change occurred. The change meant that the gene became abnormally active. The researchers tested the effect of the abnormal gene by putting it into cells grown in culture in the laboratory; they found that it made the cells grow more than was normal. In addition, when cells with the abnormal gene were put into mice, the mice developed a blood disorder similar to that seen in humans with MF.
What Do These Findings Mean?
It seems likely that the genetic change that has been identified here is responsible for the MF that develops in some patients. The MPL gene is known to be part of a pathway of genes that control how certain blood cells develop. However, it is not yet clear exactly how the genetic change found here causes the blood cells to grow abnormally, or how it causes the other clinical effects of MF. Further work will also need to be done to see if it is possible to develop drugs that can act on this gene mutation, or on the other genes that it affects so as to return the cells to normal.
Additional Information.
Please access these Web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.0030270.
• MedlinePlus, a Web site of the US National Library of Health, has pages of information on myelofibrosis and related diseases
• The National Cancer Institute, which funds research into many cancers, has information for patients on myelofibrosis, including information on clinical trials
• The MPD Foundation has information for patients with myelofibrosis and related diseases
Activation of JAK-STAT signaling via a mutation - MPLW515L- in the thrombopoietin receptor seems to have a role in the pathogenesis of some patients with myelofibrosis.
doi:10.1371/journal.pmed.0030270
PMCID: PMC1502153  PMID: 16834459
25.  JAK2V617F allele burden in polycythemia vera correlates with grade of myelofibrosis, but is not substantially affected by therapy 
Leukemia research  2010;35(2):177-182.
In a series of 105 patients with polycythemia vera, we retrospectively determined whether the JAK2V617F mutation correlated with severity of disease phenotype. Higher JAK2V617F allele burden correlated with more advanced myelofibrosis, greater splenomegaly, and higher white blood cell count, but not with age, gender, hematocrit level, or frequency of phlebotomy prior to cytoreductive therapy. Although a subgroup at increased risk for thrombosis was not clearly defined, there was a suggestion that frequency of thrombosis increased as the JAK2V617F allele burden increased. The JAK2V617F allele burden did not change significantly in treated patients with serial JAK2 analyses.
doi:10.1016/j.leukres.2010.06.017
PMCID: PMC3626091  PMID: 20650526
Myeloproliferative disorders; Treatment of polycythemia vera; JAK2V617F mutation; Allele burden; Splenomegaly; Myelofibrosis

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