A phase II study of 5-azacitidine for patients with primary and post-essential thrombocythemia/polycythemia vera myelofibrosis

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

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

Azacitidine and cytarabine induce sustained lymphopenia with abnormal differentiation of common lymphoid progenitors and prolonged suppression of Dnmt3a and Dnmt3b expression in mice

Myelosuppression is a major side effect of chemotherapy. Although decreased blood cells are restored with the recovery of bone marrow cells, insufficient recovery of decreased lymphocytes was observed in mice given azacitidine (AZA), a DNA methyltransferase (DNMT) inhibitor, even following the restoration of bone marrow cells. To understand the mechanisms behind this sustained lymphopenia, we examined AZA's impact on the hematopoietic progenitor cells and the expression of Dnmts and differentiation-related genes. An antimetabolite of cytidine analog, cytarabine (Ara-C), was used as a reference compound. Decreases in almost all blood parameters and common lymphoid progenitors (CLPs) and the downregulation of Dnmts and differentiation-related genes in Lineage-Sca-1+c-kit+ (LSK) cells were observed in mice administered AZA or Ara-C for 7 d. In the posttreatment observation, all parameters, except for lymphocytes and monocytes, exhibited recovery within 3 wk after the final dosing in both treated groups. However, no recovery from the decreases in lymphocytes, especially B cells, and monocytes occurred even after 5 wk. The number of CLPs was elevated after 3 wk. There was a tendency toward recovery from the decreased expression of Dnmt1 and differentiation-related genes, but the expression levels of Dnmt3a and Dnmt3b did not fully recover even 5 wk after the final dosing. Taken together, the findings revealed that the mechanism of sustained lymphopenia observed in mice treated with AZA or Ara-C is associated, at least in part, with the abnormal differentiation of CLPs into B cells accompanied by the prolonged suppression of Dnmt3a and Dnmt3b expression on LSK cells.

Thrombocytopenia in Patients With Myelofibrosis: A Practical Management Guide

Patients with myelofibrosis (MF) frequently develop thrombocytopenia as a consequence of bone marrow fibrosis, splenic sequestration, and myelosuppression from an inflammatory microenvironmental milieu. Thrombocytopenia occurs frequently at diagnosis, worsens with disease progression, is an independent adverse prognostic factor, and limits effective dosing of JAK2 inhibitors. Recently, pacritinib was approved for patients with MF and extreme thrombocytopenia. However, this JAK2/IRAK1 inhibitor is not primarily used to attain improvement in platelet count. In this narrative review, we discuss strategies to specifically address thrombocytopenia in MF patients including immunomodulatory drugs, synthetic androgens, hypomethylating agents and splenectomy, all of which have only modest efficacy in alleviating thrombocytopenia. We also detail transfusion approaches, including diagnostic and therapeutic consideration for platelet transfusion refractoriness. We end by discussing novel therapies, including TGFβ traps and recombinant pentraxin-2, which may increase platelet counts in MF patients. Despite recent therapeutic advancements in MF, there remains a near paucity of agents that can effectively alleviate thrombocytopenia.

Thrombocytopenia in Patients With Myelofibrosis: Pathogenesis, Prevalence, Prognostic Impact, and Treatment

Myelofibrosis (MF) is a clonal hematopoietic stem cell neoplasm, characterized by pathologic myeloproliferation associated with inflammatory and pro-angiogenic cytokine release, that results in functional compromise of the bone marrow. Thrombocytopenia is a disease-related feature of MF, which portends a poor prognosis impacting overall survival (OS) and leukemia free survival. Thrombocytopenia in MF has multiple causes including ineffective hematopoiesis, splenic sequestration, and treatment-related effects. Presently, allogeneic hematopoietic stem cell transplantation (HSCT) remains the only curable treatment for MF, which, unfortunately, is only a viable option for a minority of patients. All other currently available therapies are either focused on improving cytopenias or the alleviating systemic symptoms and burdensome splenomegaly. While JAK2 inhibitors have moved to the forefront of MF therapy, available JAK inhibitors are advised against in patients with severe thrombocytopenia (platelets < 50 × 10⁹/L). In this review, we describe the pathogenesis, prevalence, and prognostic significance of thrombocytopenia in MF. We also explore the value and limitations of treatments directed at addressing cytopenias, splenomegaly and symptom burden, and those with potential disease modification. We conclude by proposing a treatment algorithm for patients with MF and severe thrombocytopenia.

Epigenetic Dysregulation of Myeloproliferative Neoplasms

This article reviews the genetic data on epigenetic modifying mutations in myeloproliferative neoplasms and their clinical implications, preclinical studies exploring our current understanding of how mutations in epigenetic modifying proteins cooperate with myeloproliferative neoplasms drivers to promote disease progression, and recent advances in novel therapeutics supporting the role of targeting epigenetic pathways to treat fibrotic progression.

Salvage Therapy Using Azacitidine for Relapsed Primary Myelofibrosis after Cord Blood Transplantation

We present the case of a 53-year-old woman with prefibrotic stage primary myelofibrosis (PMF) who underwent cord blood transplantation. Nine years after transplantation, she relapsed, which was confirmed by a bone marrow examination. We decided to treat her using azacitidine. After three courses of azacitidine, a partial cytogenetic response was confirmed. Azacitidine maintenance therapy successfully maintained a low level of recipient-origin peripheral blood cells with a stable hematological condition. Azacitidine may therefore be a promising therapeutic option for PMF patients who relapse after allogeneic stem cell transplantation.

Novel Concepts of Treatment for Patients with Myelofibrosis and Related Neoplasms

Simple Summary

Myelofibrosis (MF) is an advanced form of a group of rare, related bone marrow cancers termed myeloproliferative neoplasms (MPNs). Some patients develop myelofibrosis from the outset, while in others, it occurs as a complication of the more indolent MPNs, polycythemia vera (PV) or essential thrombocythemia (ET). Patients with PV or ET who require drug treatment are typically treated with the chemotherapy drug hydroxyurea, while in MF, the targeted therapies termed Janus kinase (JAK) inhibitors form the mainstay of treatment. However, these and other drugs (e.g., interferons) have important limitations. No drug has been shown to reliably prevent the progression of PV or ET to MF or transformation of MPNs to acute myeloid leukemia. In PV, it is not conclusively known if JAK inhibitors reduce the risk of blood clots, and in MF, these drugs do not improve low blood counts. New approaches to treating MF and related MPNs are, therefore, necessary.

Abstract

Janus kinase (JAK) inhibition forms the cornerstone of the treatment of myelofibrosis (MF), and the JAK inhibitor ruxolitinib is often used as a second-line agent in patients with polycythemia vera (PV) who fail hydroxyurea (HU). In addition, ruxolitinib continues to be studied in patients with essential thrombocythemia (ET). The benefits of JAK inhibition in terms of splenomegaly and symptoms in patients with MF are undeniable, and ruxolitinib prolongs the survival of persons with higher risk MF. Despite this, however, “disease-modifying” effects of JAK inhibitors in MF, i.e., bone marrow fibrosis and mutant allele burden reduction, are limited. Similarly, in HU-resistant/intolerant PV, while ruxolitinib provides excellent control of the hematocrit, symptoms and splenomegaly, reduction in the rate of thromboembolic events has not been convincingly demonstrated. Furthermore, JAK inhibitors do not prevent disease evolution to MF or acute myeloid leukemia (AML). Frontline cytoreductive therapy for PV generally comprises HU and interferons, which have their own limitations. Numerous novel agents, representing diverse mechanisms of action, are in development for the treatment of these three classic myeloproliferative neoplasms (MPNs). JAK inhibitor-based combinations, all of which are currently under study for MF, have been covered elsewhere in this issue. In this article, we focus on agents that have been studied as monotherapy in patients with MF, generally after JAK inhibitor resistance/intolerance, as well as several novel compounds in development for PV/ET.

Management of challenging myelofibrosis after JAK inhibitor failure and/or progression

The myeloproliferative neoplasms (MPNs) encompass a heterogenous set of diseases that have variable survival, but in the setting of treatment refractory and progressive disease, prognosis has been characteristically poor. JAK inhibition with ruxolitinib or fedratinib therapy has become the first line treatment for symptomatic or intermediate to high risk myelofibrosis. However, after three years of ruxolitinib therapy, approximately half of all patients with myelofibrosis will likely have stopped treatment. JAK inhibition failure represents a mixture of etiologies, including drug intolerance, suboptimal dosing, drug resistance, or progression of disease. JAK inhibition failure and accelerated/blast phase have now become the primary clinical challenges in the treatment of myelofibrosis and high risk polycythemia vera, and no phase III trials or clear treatment guidelines exist to guide management strategies in this setting. On the other hand, this represents an exciting time in treatment of JAK inhibitor failure and accelerated phase MPNs due to the advent of recently approved drugs as well as new targeted agents currently under investigation. In this article, we review the management options for these challenging clinical scenarios. We discuss the options for JAK inhibitor dose optimization and overcoming resistance by utilizing combinations of JAK inhibition, primarily ruxolitinib, with alternative commercially available therapies. For patients who have progressed, we discuss recent data regarding targeted therapy options approved for AML that represent potentially efficacious options in the progressive MPN setting. We also discuss the new clinical agents under development in MF and accelerated MPNs that may offer new therapeutic options in the years to come.

Current and future therapies for myelofibrosis

Myelofibrosis is classified as a 'Philadelphia-chromosome negative' clonal myeloproliferative disorder. The heterogeneity of this condition and patient population and array of often challenging clinical manifestations can frequently make therapeutic decisions challenging. Despite many advances in therapy with targeted and combination approaches, following an enhanced understanding of underlying disease pathogenesis, cure only remains achievable with allogeneic stem cell transplant. This option is often limited to a small group of younger transplant-eligible patients with more advanced disease who have both a suitable donor and no or few co-morbidities. In this article, we will discuss up-to-date disease prognostication, common clinical challenges associated with myelofibrosis and both standard and novel therapeutic approaches. Increasingly complex prognostic modelling utilises patient-specific, haematological and genomic parameters to improve the accuracy of risk assessment and predict disease progression. We will also focus on difficult clinical scenarios such as disease-associated anaemia, thrombocytopenia and extremes of age. Future and evolving therapies within this field are highly anticipated and novel JAK inhibitor and non-JAK inhibitor-based therapy will also be discussed, including the new challenge of how to switch from one JAK inhibitor therapy to another.

A provider's guide to primary myelofibrosis: pathophysiology, diagnosis, and management

Although understanding of the pathogenesis and molecular biology of primary myelofibrosis continues to improve, treatment options are limited, and several biological features remain unexplained. With an appropriate clinical history, exam, laboratory evaluation, and bone marrow biopsy, the diagnosis can often be established. Recent studies have better characterized prognostic factors and driver mutations in myelofibrosis, facilitated by use of next-generation sequencing. These advances have facilitated development of a management strategy that is based on both risk factors and clinical phenotype. For low-risk patients, treatment will depend on symptom severity. For patients with higher-risk disease, several treatments are available including JAK inhibitors, allogeneic hematopoietic stem cell transplant, and clinical trials using novel molecularly targeted therapies and rational drug combinations. In this review, we outline what is known about the disease pathogenesis, discuss an approach to reaching the diagnosis, review the prognosis of myelofibrosis, and detail current therapeutic strategies.

Novel strategies for the treatment of myelofibrosis driven by recent advances in understanding the role of the microenvironment in its etiology

Myelofibrosis is the advanced stage of the Philadelphia chromosome-negative myeloproliferative neoplasms (MPNs), characterized by systemic inflammation, hematopoietic failure in the bone marrow, and development of extramedullary hematopoiesis, mainly in the spleen. The only potentially curative therapy for this disease is hematopoietic stem cell transplantation, an option that may be offered only to those patients with a compatible donor and with an age and functional status that may face its toxicity. By contrast, with the Philadelphia-positive MPNs that can be dramatically modified by inhibitors of the novel BCR-ABL fusion-protein generated by its genetic lesion, the identification of the molecular lesions that lead to the development of myelofibrosis has not yet translated into a treatment that can modify the natural history of the disease. Therefore, the cure of myelofibrosis remains an unmet clinical need. However, the excitement raised by the discovery of the genetic lesions has inspired additional studies aimed at elucidating the mechanisms driving these neoplasms towards their final stage. These studies have generated the feeling that the cure of myelofibrosis will require targeting both the malignant stem cell clone and its supportive microenvironment. We will summarize here some of the biochemical alterations recently identified in MPNs and the novel therapeutic approaches currently under investigation inspired by these discoveries.

Overview of the Mutational Landscape in Primary Myelofibrosis and Advances in Novel Therapeutics

Primary Myelofibrosis is a BCR-ABL negative myeloproliferative neoplasm with a variety of hematological presentations, including thrombosis, bleeding diathesis and marrow fibrosis. It is estimated to have an incidence of 1.5 per 100,000 people each year. Although JAK2 or MPL mutations are seen in PMF, several other mutations have recently been documented, including mutations in CALR, epigenetic regulators like TET, ASXL1, and 13q deletions. The identification of these mutations has improved the ability to develop novel treatment options. These include JAK inhibitors like ruxolitinib, heat shock protein-90 inhibitors like ganetespib, histone deacetylase inhibitors including panobinostat, pracinostat, vorinostat and givinostat, hypomethylating agents like decitabine, hedgehog inhibitors like glasdegib, PI3K, AKT and mTOR inhibitors like everolimus as well as telomerase inhibitors like imtelstat. Research on novel therapeutic options is being actively pursued in order to expand treatment options for primary myelofibrosis however currently, there is no curative therapy other than allogenic hematopoietic stem cell transplantation (ASCT) which is possible in select patients.

SOHO State of the Art Updates and Next Questions: Myelofibrosis

The discovery of a mutation in the Janus Kinase 2 gene in 2005 spurred significant progress in the field of myeloproliferative neoplasms. A comprehensive description of genomic factors at play in the malignant clone in myeloproliferative neoplasms, particularly myelofibrosis (MF), have recently led to more precise, personalized prognostic tools. Despite this, understanding of the disease pathogenesis remains relatively limited. We continue to lack a detailed description of the interaction between the hematopoietic stem cell clone, abnormal bone marrow niche cells, and circulating signaling molecules and an understanding of how they cooperate to promote cell proliferation, fibrogenesis, and extramedullary hematopoiesis. Despite our knowledge gaps, recent research in MF has led to promising clinical translation. In this article, we summarize recent insights into MF pathophysiology, progress in the development of novel therapeutics, and opportunities for further advancement of the field.

Pharmacotherapy of Myelofibrosis

Myelofibrosis (MF) is a myeloproliferative neoplasm that is pathologically characterized by bone marrow myeloproliferation, reticulin and collagen fibrosis, and extramedullary hematopoiesis. Constitutive activation of the Janus associated kinase (JAK)-signal transducers and activators of transcription signaling pathway with resultant elevation in pro-inflammatory cytokine levels is the pathogenic hallmark of MF. JAK inhibitors, namely ruxolitinib, have been successful in alleviating symptoms and reducing splenomegaly, but therapy-related myelosuppression has led to the further development of highly selective JAK2 inhibitors. Additionally, ruxolitinib does not appear to affect the malignant hematopoietic clone substantially, evidenced by lack of molecular remissions, bone marrow histopathologic responses, and a proportion of treated patients developing progressive disease and leukemic transformation while receiving therapy. A number of other pharmacotherapeutic strategies are currently being explored in the clinic. Non-JAK inhibitor strategies being evaluated in MF include non-JAK signaling pathway inhibitors, epigenetic-directed therapies, immune-modulating agents, anti-fibrotic agents, and telomerase inhibitors. This review highlights the current landscape of MF pharmacotherapy and explores therapeutic advances underway.

Managing myelofibrosis (MF) that "blasts" through: advancements in the treatment of relapsed/refractory and blast-phase MF

Myelofibrosis (MF) is the most aggressive form of Philadelphia chromosome-negative myeloproliferative neoplasm, and it is complicated by severe symptom burden, thrombotic events, infections, cytopenias, and transformation to acute myeloid leukemia (AML). Ruxolitinib, the first-line therapy for symptomatic or intermediate- and high-prognostic risk MF, has improved overall survival for this population. However, approximately one-half of MF patients will discontinue ruxolitinib by the first few years of therapy due to a spectrum of resistance, intolerance, relapse, or progression to blast phase disease. Danazol, erythropoietin-stimulating agents, and spleen-directed therapies can be useful in the ruxolitinib-resistant setting. In the ruxolitinib-refractory or -intolerant setting, commercial and novel therapies, either alone or in combination with ruxolitinib, have shown clinical utility. For blast-phase MF, the recent advancements in available AML therapies have increased the options with targeted and more tolerable therapies. In this article, we will discuss our paradigm for the management of relapsed/refractory and blast-phase MF in the context of therapeutic advancements in both AML and MF.

Novel treatments to tackle myelofibrosis

INTRODUCTION

Despite the dramatic progress made in the treatment of patients with myelofibrosis since the introduction of the JAK1/2 inhibitor ruxolitinib, a therapeutic option that can modify the natural history of the disease and prevent evolution to blast-phase is still lacking. Recent investigational treatments including immunomodulatory drugs and histone deacetylase inhibitors benefit some patients but these effects have proven modest at best. Several novel agents do show promising activity in preclinical studies and early-phase clinical trials. We will illustrate a snapshot view of where the management of myelofibrosis is evolving, in an era of personalized medicine and advanced molecular diagnostics. Areas covered: A literature search using MEDLINE and recent meeting abstracts was performed using the keywords below. It focused on therapies in active phases of development based on their scientific and preclinical rationale with the intent to highlight agents that have novel biological effects. Expert commentary: The most mature advances in treatment of myelofibrosis are the development of second-generation JAK1/2 inhibitors and improvements in expanding access to donors for transplantation. In addition, there are efforts to identify drugs that target pathways other than JAK/STAT signaling that might improve the survival of myelofibrosis patients, and limit the need for stem-cell transplantation.

A phase 2 study of ruxolitinib in combination with azacitidine in patients with myelofibrosis

Ruxolitinib (RUX)-based combinations may provide benefit for patients with myelofibrosis (MF). In this open-label, nonrandomized, prospective phase 2 study, patients with MF initially received RUX twice per day continuously in 28-day cycles for the first 3 cycles. Azacitidine (AZA) 25 mg/m² (days 1-5) was added starting with cycle 4 and could be subsequently increased to 75 mg/m² (days 1-5). Forty-six patients were enrolled with a median follow-up of 28 months (range, 4-50+ months). An International Working Group for Myelofibrosis Research and Treatment (IWG-MRT) response was achieved in 33 patients (72%), with a median time to response of 1.8 months (range, 0.7-19.0 months). One-fourth (7 of 33) of the IWG-MRT responses occurred after the addition of AZA. A reduction of >50% in palpable spleen length at 24 weeks and at any time on the study was achieved in 62% and 71% of the evaluable patients, respectively. Among patients who achieved a >50% reduction in spleen length at 24 weeks, 95% had maintained it at 48 weeks. Notably, improvements in bone marrow reticulin fibrosis grade occurred in 57% of the patients at 24 months. Treatment discontinuations as a result of drug-related toxicities occurred in 4 patients (9%), all as a result of cytopenias. New onset grade 3 to 4 anemia and thrombocytopenia occurred in 35% and 26% of patients, respectively. RUX and AZA were safe, with encouraging spleen response rates and improvement in bone marrow fibrosis in patients with MF. This trial was registered at www.clinicaltrials.gov as #NCT01787487.

Acute Myeloid Leukemia: The Good, the Bad, and the Ugly

Acute myeloid leukemia (AML) was initially subdivided according to morphology (the French-American-British system), which proved helpful in pathologic categorization. Subsequently, clinical and genomic factors were found to correlate with response to chemotherapy and with overall survival. These included a history of antecedent hematologic disease, a history of chemotherapy or radiation therapy, the presence of various recurrent cytogenetic abnormalities, and, more recently, the presence of specific point mutations. This article reviews the biology and responses of one AML subgroup with consistent response and good outcomes following chemotherapy (core-binding factor leukemia), and two subgroups with persistently bad, and even ugly, outcomes (secondary AML and TP53-mutated AML).

Epigenetic regulation of NFE2 overexpression in myeloproliferative neoplasms

The transcription factor "nuclear factor erythroid 2" (NFE2) is overexpressed in the majority of patients with myeloproliferative neoplasms (MPNs). In murine models, elevated NFE2 levels cause an MPN phenotype with spontaneous leukemic transformation. However, both the molecular mechanisms leading to NFE2 overexpression and its downstream targets remain incompletely understood. Here, we show that the histone demethylase JMJD1C constitutes a novel NFE2 target gene. JMJD1C levels are significantly elevated in polycythemia vera (PV) and primary myelofibrosis patients; concomitantly, global H3K9me1 and H3K9me2 levels are significantly decreased. JMJD1C binding to the NFE2 promoter is increased in PV patients, decreasing both H3K9me2 levels and binding of the repressive heterochromatin protein-1α (HP1α). Hence, JMJD1C and NFE2 participate in a novel autoregulatory loop. Depleting JMJD1C expression significantly reduced cytokine-independent growth of an MPN cell line. Independently, NFE2 is regulated through the epigenetic JAK2 pathway by phosphorylation of H3Y41. This likewise inhibits HP1α binding. Treatment with decitabine lowered H3Y41ph and augmented H3K9me2 levels at the NFE2 locus in HEL cells, thereby increasing HP1α binding, which normalized NFE2 expression selectively in JAK2V617F-positive cell lines.

Effect of MeCP2 on TGF-β1-induced Extracellular Matrix Production in Nasal Polyp-derived Fibroblasts

Purpose

Methyl-CpG-binding protein 2 (MeCP2), known as a transcriptional regulator, has been suggested to play an important role in myofibroblast differentiation in the lung. The purpose of this study was to investigate the role of MeCP2 in transforming growth factor (TGF)- β1-induced myofibroblast differentiation and extracellular matrix (ECM) production in nasal polyp-derived fibroblasts (NPDFs).

Methods

To identify the expression of MeCP2 in nasal polyp tissues, immunohistochemistry staining and Western blot were performed. TGF- β1-induced NPDFs were treated with 5-azacytidine, a DNA methylation inhibitor, and the expression levels of α-SMA and fibronectin were determined by semiquantitative reverse transcription polymerase chain reaction, immunofluorescent staining, and Western blotting. The total soluble collagen was analyzed by the Sircol collagen assay. MeCP2 silenced by MeCP2-specific small interference ( si) RNA was verified by Western blot.

Results

The expression levels of MeCP2 increased in nasal polyp tissues compared to normal inferior turbinate tissues. 5-Azacytidine significantly inhibited the expression of α-SMA and fibronectin mRNA in a dose-dependent manner. In addition, 5-azacytidine suppressed collagen production and the expression of MeCP2 in the same manner. The expression levels of a-SMA and collagen production were significantly blocked by MeCP2 silencing in TGF- β1-induced NPDFs.

Conclusions

Our data suggest that MeCP2 plays an essential role in TGF- β1-induced myofibroblast differentiation and ECM production in NPDFs.

A phase II trial of ruxolitinib in combination with azacytidine in myelodysplastic syndrome/myeloproliferative neoplasms

Ruxolitinib and azacytidine target distinct disease manifestations of myelodysplastic syndrome/myeloproliferative neoplasms (MDS/MPNs). Patients with MDS/MPNs initially received ruxolitinib BID (doses based on platelets count), continuously in 28-day cycles for the first 3 cycles. Azacytidine 25 mg/m² (Day 1-5) intravenously or subcutaneously was recommended to be added to each cycle starting cycle 4 and could be increased to 75 mg/m² (Days 1-5) for disease control. Azacytidine could be started earlier than cycle 4 and/or at higher dose in patients with rapidly proliferative disease or with elevated blasts. Thirty-five patients were treated (MDS/MPN-U, n =14; CMML, n =17; aCML, n =4), with a median follow-up of 15.2 months (range, 1.0-41.5). All patients were evaluable by the 2015 international consortium proposal of response criteria for MDS/MPNs (ICP MDS/MPN) and 20 (57%) responded. Nine patients (45%) responded after the addition of azacytidine. A greater than 50% reduction in palpable splenomegaly at 24 weeks was noted in 9/14 (64%) patients. Responders more frequently were JAK2-mutated (P = .02) and had splenomegaly (P = .03) compared to nonresponders. New onset grade 3/4 anemia and thrombocytopenia occurred in 18 (51%) and 19 (54%) patients, respectively, but required therapy discontinuation in only 1 (3%) patient. Patients with MDS/MPN-U had better median survival compared to CMML and aCML (26.5 vs 15.1 vs 8 months; P = .034). The combination of ruxolitinib and azacytidine was well-tolerated with an ICP MDS/MPN-response rate of 57% in patients with MDS/MPNs. The survival benefit was most prominent in patients with MDS/MPN-U.

JAK inhibitors for the treatment of myeloproliferative neoplasms and other disorders

JAK inhibitors have been developed following the discovery of the JAK2V617F in 2005 as the driver mutation of the majority of non- BCR-ABL1 myeloproliferative neoplasms (MPNs). Subsequently, the search for JAK2 inhibitors continued with the discovery that the other driver mutations ( CALR and MPL) also exhibited persistent JAK2 activation. Several type I ATP-competitive JAK inhibitors with different specificities were assessed in clinical trials and exhibited minimal hematologic toxicity. Interestingly, these JAK inhibitors display potent anti-inflammatory activity. Thus, JAK inhibitors targeting preferentially JAK1 and JAK3 have been developed to treat inflammation, autoimmune diseases, and graft-versus-host disease. Ten years after the beginning of clinical trials, only two drugs have been approved by the US Food and Drug Administration: one JAK2/JAK1 inhibitor (ruxolitinib) in intermediate-2 and high-risk myelofibrosis and hydroxyurea-resistant or -intolerant polycythemia vera and one JAK1/JAK3 inhibitor (tofacitinib) in methotrexate-resistant rheumatoid arthritis. The non-approved compounds exhibited many off-target effects leading to neurological and gastrointestinal toxicities, as seen in clinical trials for MPNs. Ruxolitinib is a well-tolerated drug with mostly anti-inflammatory properties. Despite a weak effect on the cause of the disease itself in MPNs, it improves the clinical state of patients and increases survival in myelofibrosis. This limited effect is related to the fact that ruxolitinib, like the other type I JAK2 inhibitors, inhibits equally mutated and wild-type JAK2 (JAK2WT) and also the JAK2 oncogenic activation. Thus, other approaches need to be developed and could be based on either (1) the development of new inhibitors specifically targeting JAK2V617F or (2) the combination of the actual JAK2 inhibitors with other therapies, in particular with molecules targeting pathways downstream of JAK2 activation or the stability of JAK2 molecule. In contrast, the strong anti-inflammatory effects of the JAK inhibitors appear as a very promising therapeutic approach for many inflammatory and auto-immune diseases.

Current treatment algorithm for the management of patients with myelofibrosis, JAK inhibitors, and beyond

Myelofibrosis (MF) is a heterogeneous disorder characterized by splenomegaly, constitutional symptoms, ineffective hematopoiesis, and an inherent risk of leukemic transformation. The past decade has seen a massive shift in available therapeutic options for our patients and we are learning how and when to use novel agents, either alone or in combination, during the disease course. This has translated into improved management of splenomegaly, significant amelioration in disease-related symptom burden for many, and may lead to improved survival. But limitations in the therapeutic options remain. Moreover, enhanced delineation of the mutational landscape of MF has offered both increasingly complex prognostic algorithms and yielded further potential therapeutic avenues. In this review, we will focus on stratifying both standard and experimental therapeutic management in 2017 and 2018 and postulate on the emerging treatments that will likely become part of our increasingly complex treatment algorithm.

Novel Therapies for Myelofibrosis

PURPOSE OF REVIEW

The purpose of the review was to provide a contemporary update of novel agents and targets under investigation in myelofibrosis in the Janus kinase (JAK) inhibitor era.

RECENT FINDINGS

Myelofibrosis (MF) is a clonal stem cell disease characterized by marrow fibrosis and a heterogeneous disease phenotype with a variable degree of splenomegaly, cytopenias, and constitutional symptoms that significantly impact quality of life and survival. Overactive JAK/STAT signaling is a hallmark of MF. The only approved therapy for MF, JAK1/2 inhibitor ruxolitinib, can ameliorate splenomegaly, improve symptoms, and prolong survival in some patients. Therapeutic challenges remain, however. Myelosuppression limits the use of ruxolitinib in some patients, eventual drug resistance is common, and the underlying malignant clone persists despite therapy. A deeper understanding of the pathogenesis of MF has informed the development of additional agents. Promising targets under investigation include JAK1 and JAK2 and downstream intermediates in related signaling pathways, epigenetic modifiers, pro-inflammatory cytokines, and immune regulators.

Effective treatment of low-dose decitabine in myelodysplastic syndrome/myeloproliferative neoplasms

Objective

Primary myelofibrosis (PMF) is one of the Philadelphia negative myeloproliferative neoplasms (MPN). The main clinical features are obvious physical symptoms and symptomatic splenomegaly. It may be converse to leukemia and has a shortened life expectancy. Nowadays, the therapy for PMF is aimed at maintaining comfort and there is no curative treatment. PMF with myelodysplastic syndrome (MDS), called MDS/MPN-u, is rare and the treatment is complex. In this study, we want to discuss an effective treatment for MDS/MPN via a case report and literature review.

Materials and methods

A female patient was diagnosed with MDS/MPN through bone marrow cytology, immunology, cell genetics, molecular biology, and pathology. She received thalidomide and prednisone as initial treatment. Ten months later, the first-line therapy had failed, she presented with clinically relevant pancytopenia and increased blasts in bone marrow. Because decitabine is one of the first-line treatments for MDS and the patient was frail, she received low-dose decitabine as second-line therapy. Decitabine was administered at 15 mg/m² once a week for 3 weeks, in a 4 week cycle. If there was improvement the treatment interval was prolonged.

Result

After one cycle, the blasts in bone marrow were decreased to 0.5%. After four cycles, she felt comfortable and hematological improvement was achieved. The treatment interval was prolonged. After eight cycles, the spleen reduced to 2 cm under the rib, and she achieved complete hematological remission. After ten cycles, the mutation of JAK2/V617F expression was decreased from 60.63% to 0.01%. During the therapy, the patient presented with grade III–IV hematological toxicity after the first two cycles, but there were no side effects after subsequent cycles.

Conclusion

Our research showed that low-dose decitabine may be an effective treatment for MDS/MPN, especially in improving physical symptoms and achieving hematological remission. Besides, it may be possible to reverse positive JAK2 mutation.

JAK2 inhibitors for myeloproliferative neoplasms: what is next?

Since its approval in 2011, the Janus kinase 1/2 (JAK1/2) inhibitor ruxolitinib has evolved to become the centerpiece of therapy for myelofibrosis (MF), and its use in patients with hydroxyurea resistant or intolerant polycythemia vera (PV) is steadily increasing. Several other JAK2 inhibitors have entered clinical testing, but none have been approved and many have been discontinued. Importantly, the activity of these agents is not restricted to patients with JAK2 V617F or exon 12 mutations. Although JAK2 inhibitors provide substantial clinical benefit, their disease-modifying activity is limited, and rational combinations with other targeted agents are needed, particularly in MF, in which survival is short. Many such combinations are being explored, as are other novel agents, some of which could successfully be combined with JAK2 inhibitors in the future. In addition, new JAK2 inhibitors with the potential for less myelosuppression continue to be investigated. Given the proven safety and efficacy of ruxolitinib, it is likely that ruxolitinib-based combinations will be a major way forward in drug development for MF. If approved, less myelosuppressive JAK2 inhibitors such as pacritinib or NS-018 could prove to be very useful additions to the therapeutic armamentarium in MF. In PV, inhibitors of histone deacetylases and human double minute 2 have activity, but their role, if any, in the future treatment algorithm is uncertain, given the availability of ruxolitinib and renewed interest in interferons. Ruxolitinib is in late-phase clinical trials in essential thrombocythemia, in which it could fill an important void for patients with troublesome symptoms.

Management of myelofibrosis: JAK inhibition and beyond

INTRODUCTION

Myelofibrosis (MF) is characterized by bone marrow fibrosis with subsequent extramedullary hematopoiesis and abnormal cytokine expression leading to splenomegaly, constitutional symptoms and cytopenias. The discovery of the JAK2 V617F mutation in the majority of MF patients has been followed by significant progress in drug development for MF. Areas covered: In this article, we review advances in the understanding of the underlying disease biology, prognostic assessment and therapeutic modalities for MF. We provide clinical trial evidence behind using the JAK2 inhibitor ruxolitinib, erythropoiesis stimulating agents, androgens, immunomodulatory drugs, interferon, cytoreductive drugs and hypomethylating agents in MF. Finally, we review novel therapeutic options for MF including the new JAK1/2 inhibitors, ruxolitinib based combination approaches as well as novel therapeutic agents. Expert commentary: Despite significant reduction of splenomegaly and improvement of symptom burden and a signal for survival improvement, ruxolitinib does not lead to major reductions in JAK2 V617F allele burden and bone marrow fibrosis. No ruxolitinib-based combination approach has so far demonstrated superiority over ruxolitinib monotherapy. The novel JAK2 inhibitors pacritinib and momelotinib, other JAK inhibitors, telomerase inhibitors, anti-fibrosis agents and hsp90 inhibitors are in different stages of development.

Treatment of Myelofibrosis: Old and New Strategies

Myelofibrosis (MF) is a BCR-ABL1-negative myeloproliferative neoplasm that is mainly characterised by reactive bone marrow fibrosis, extramedullary haematopoiesis, anaemia, hepatosplenomegaly, constitutional symptoms, leukaemic progression, and shortened survival. As such, this malignancy is still orphan of curative treatments; indeed, the only treatment that has a clearly demonstrated impact on disease progression is allogeneic haematopoietic stem cell transplantation, but only a minority of patients are eligible for such intensive therapy. However, more recently, the discovery of JAK2 mutations has also led to the development of small-molecule JAK1/2 inhibitors, the first of which, ruxolitinib, has been approved for the treatment of MF in the United States and Europe. In this article, we report on old and new therapeutic strategies that proved effective in early preclinical and clinical trials, and subsequently in the daily clinical practice, for patients with MF, particularly concerning the topics of anaemia, splenomegaly, iron overload, and allogeneic stem cell transplantation.

Emerging treatments for classical myeloproliferative neoplasms

There has been a major revolution in the management of patients with myeloproliferative neoplasms (MPN), and in particular those with myelofibrosis and extensive splenomegaly and symptomatic burden, after the introduction of the JAK1 and JAK2 inhibitor ruxolitinib. The drug also has been approved as second-line therapy for polycythemia vera (PV). However, the therapeutic armamentarium for MPN is still largely inadequate for coping with patients' major unmet needs, which include normalization of life span (myelofibrosis and some patients with PV), reduction of cardiovascular complications (mainly PV and essential thrombocythemia), prevention of hematological progression, and improved quality of life (all MPN). In fact, none of the available drugs has shown clear evidence of disease-modifying activity, even if some patients treated with interferon and ruxolitinib showed reduction of mutated allele burden, and ruxolitinib might extend survival of patients with higher-risk myelofibrosis. Raised awareness of the molecular abnormalities and cellular pathways involved in the pathogenesis of MPN is facilitating the development of clinical trials with novel target drugs, either alone or in combination with ruxolitinib. Although for most of these molecules a convincing preclinical rationale was provided, the results of early phase 1 and 2 clinical trials have been quite disappointing to date, and toxicities sometimes have been limiting. In this review, we critically illustrate the current landscape of novel therapies that are under evaluation for patients with MPN on the basis of current guidelines, patient risk stratification criteria, and previous experience, looking ahead to the chance of a cure for these disorders.

Myelofibrosis: an update on drug therapy in 2016

INTRODUCTION

Primary myelofibrosis (PMF) is the least common but the most aggressive of the classic Philadelphia chromosome-negative myeloproliferative neoplasms. Survival is much shorter in PMF than in polycythemia vera (PV) or essential thrombocythemia (ET). Post-PV/ET myelofibrosis (MF) is clinically indistinguishable from PMF and approached similarly. Areas covered: Current pharmacologic therapy of MF revolves around the Janus kinase 1/2 (JAK1/2) inhibitor ruxolitinib, which dramatically improves constitutional symptoms and splenomegaly in the majority of patients, and improves overall survival (OS). However, allogeneic stem cell transplantation remains the only potential cure. Other JAK inhibitors continue to be developed for MF, and momelotinib and pacritinib are in phase III clinical trials. Anemia is common in MF, and initially worsened by ruxolitinib. Momelotinib and pacritinib may prove advantageous in this regard. Current strategies for managing anemia of MF include danazol, immunomodulatory drugs and erythroid stimulating agents, either alone or in combination with ruxolitinib. Expert opinion: A number of other agents, representing diverse drug classes, are in various stages of development for MF. These include newer JAK inhibitors, other signaling inhibitors, epigenetic modifiers, anti-fibrotic agents, telomerase inhibitors, and activin receptor ligand traps (for anemia). Hopefully, these novel therapies will further extend the clinical benefits of ruxolitinib.

Treatment of Myelofibrosis: A Moving Target

Myelofibrosis (MF) is a myeloproliferative neoplasm that presents either as a primary disease or evolves secondarily from polycythemia vera or essential thrombocythemia to post-polycythemia vera MF or post-essential thrombocythemia MF, respectively. Myelofibrosis is characterized by stem cell-derived clonal myeloproliferation, abnormal cytokine expression, bone marrow fibrosis, anemia, splenomegaly, extramedullary hematopoiesis, constitutional symptoms, cachexia, leukemic progression, and shortened survival. Therapeutic options for patients with MF have been limited to the use of cytoreductive agents, predominantly hydroxyurea; splenectomy and splenic irradiation for treatment of splenomegaly; and management of anemia with transfusions, erythropoiesis-stimulating agents, androgens, and immunomodulatory agents along with steroids. The only curative option is allogeneic stem cell transplantation (ASCT), which is associated with high morbidity and mortality risks. Recently, JAK (Janus kinase) inhibitor therapies have become available and proven to be palliative in primary MF patients with hydroxyurea-refractory splenomegaly and severe constitutional symptoms. The purpose of this article is to review the clinical features of MF; discuss different treatment strategies, including ASCT; and discuss the potential danger and benefit of using JAK inhibitors prior to ASCT.

Pharmacologic management of myelofibrosis

Myelofibrosis is a BCR-ABL-negative myeloproliferative neoplasm characterized by abnormal hematopoiesis. Alterations to the Janus kinase-signal transducer and activator of transcription pathway result in dysregulation of gene transcription and cell proliferation. Patients with symptomatic myelofibrosis present with a variety of signs and symptoms including, but not limited to myelosuppression, marked splenomegaly, abdominal discomfort, fatigue, and blood transfusion-dependence. Traditional myelosuppressive therapies including hydroxyurea, azacitidine, and cladribine aim to reduce constitutional symptoms and control the burden of disease. Immunomodulators can potentially reverse anemia associated with myelofibrosis, but are poorly tolerated by most patients. The novel Janus kinase 2 (JAK2) inhibitor, ruxolitinib, has demonstrated marked improvements to constitutional symptoms and splenomegaly. While survival benefit has not yet been demonstrated, continued research into pharmacologic management of myelofibrosis offers the promise of altering the course of disease progression.

Clinical use of ruxolitinib in an academic medical center in unselected patients with myeloproliferative neoplasms not on clinical study

Ruxolitinib is the only approved therapy for myelofibrosis (MF). However, its use in patients with myeloproliferative neoplasms (MPN) not participating in clinical studies has been poorly described. We reviewed the medical records of 45 patients (35 MF, 10 others) treated with ruxolitinib at our center, off clinical study, during the year after its approval. Patients had advanced features and were refractory to multiple therapies. Ruxolitinib was effective in reducing splenomegaly (51% response rate) and constitutional symptoms (42% response rate). It controlled blood counts in patients with polycythemia and thrombocythemia but was not effective in patients with non-classic MPNs. Ruxolitinib was an active therapy in patients previously treated with a JAK inhibitor and was safely combined with hypomethylating agents in patients with elevated blasts. Median overall survival was 24 months; 10 patients transformed to acute leukemia. Its use in combination with other active agents should be further explored in clinical studies.

Proteostasis alterations in myeloproliferative neoplasms: Oncogenic relevance and therapeutic opportunities

Myeloproliferative neoplasms (MPNs) represent a frequently occurring group of heterogeneous hematologic malignancies. In the last decade, the identification of JAK2-activating mutations in a significant proportion of MPN patients gave rise to the first molecularly driven therapy for BCR-ABL-negative patients. Nevertheless, current efforts are still focused on the identification of novel therapeutic targets to achieve permanent remission. In this perspective, we focus on the recent findings in this field and highlight new evidence linking proteostasis deregulation with myeloid transformation. We recently reported that the proteostasis regulator AIRAPL acts as a tumor suppressor in MPNs through the modulation of insulin-like growth factor receptor levels at the endoplasmic reticulum. This finding paves the way for new therapeutic approaches to these neoplasms and indicates the importance of protein homeostasis maintenance for normal hematopoiesis.

Therapeutic approaches in myelofibrosis and myelodysplastic/myeloproliferative overlap syndromes

The discovery of JAK2 (V617F) a decade ago led to optimism for a rapidly developing treatment revolution in Ph(-) myeloproliferative neoplasms. Unlike BCR-ABL, however, JAK2 was found to have a more heterogeneous role in carcinogenesis. Therefore, for years, development of new therapies was slow, despite standard treatment options that did not address the overwhelming symptom burden in patients with primary myelofibrosis (MF), post-essential thrombocythemia MF, post-polycythemia vera MF, and myelodysplastic syndrome (MDS)/myeloproliferative neoplasm (MPN) syndromes. JAK-STAT inhibitors have changed this, drastically ameliorating symptoms and ultimately beginning to show evidence of impact on survival. Now, the genetic foundations of myelofibrosis and MDS/MPN are rapidly being elucidated and contributing to targeted therapy development. This has been empowered through updated response criteria for MDS/MPN and refined prognostic scoring systems in these diseases. The aim of this article is to summarize concisely the current and rationally designed investigational therapeutics directed at JAK-STAT, hedgehog, PI3K-Akt, bone marrow fibrosis, telomerase, and rogue epigenetic signaling. The revolution in immunotherapy and novel treatments aimed at previously untargeted signaling pathways provides hope for considerable advancement in therapy options for those with chronic myeloid disease.

New Strategies in Myeloproliferative Neoplasms: The Evolving Genetic and Therapeutic Landscape

The classical BCR-ABL1-negative myeloproliferative neoplasms (MPN) include essential thrombocythemia (ET), polycythemia vera (PV), and myelofibrosis (MF). Although these clonal disorders share certain clinical and genetic features, MF in particular is distinct for its complex mutational landscape, severe disease phenotype, and poor prognosis. The genetic complexity inherent to MF has made this disease extremely challenging to treat. Pharmacologic JAK inhibition has proven to be a transformative therapy in MPNs, alleviating symptom burden and improving survival, but has been hampered by off-target toxicities and, as monotherapy, has shown limited effects on mutant allele burden. In this review, we discuss the genetic heterogeneity contributing to the pathogenesis of MPNs, focusing on novel driver and epigenetic mutations and how they relate to combination therapeutic strategies. We discuss results from ongoing studies of new JAK inhibitors and report on new drugs and drug combinations that have demonstrated success in early preclinical and clinical trials, including type II JAK inhibitors, antifibrotic agents, and telomerase inhibitors.

Evolving Therapeutic Strategies for the Classic Philadelphia-Negative Myeloproliferative Neoplasms

Despite the emergence of JAK inhibitors, there is a need for disease-modifying treatments for Philadelphia-negative myeloproliferative neoplasms (MPNs). JAK inhibitors ameliorate symptoms and address splenomegaly, but because of the heterogeneous contributors to the disease process, JAK inhibitor monotherapy incompletely addresses the burden of disease. The ever-growing understanding of MPN pathogenesis has provided the rationale for testing novel and targeted therapeutic agents, as monotherapies or in combination, in preclinical and clinical settings. A number of intriguing options have emerged, and it is hoped that further progress will lead to significant changes in the natural history of MPNs.

Emerging drugs for the treatment of myelofibrosis

INTRODUCTION

Myelofibrosis (MF) is a myeloproliferative neoplasm associated with significant disease burden composed of splenomegaly, constitutional symptoms and a reduced life expectancy. The advent of targeted treatments has provided new means by which to improve MF associated splenomegaly, symptoms, health-related quality of life and even mortality.

AREAS COVERED

We discuss the spectrum of targeted treatments currently under investigation for MF. We furthermore compare their effects on improving anemia, reducing fibrosis and splenomegaly and enhancing symptom control.

EXPERT OPINION

MF is a complex disorder, partly attributable to its heterogeneity. Although the severity of patient symptoms correlates with risk category, high symptom burden may also be observed in low-risk patients. Serial use of PRO tools allows clinicians to objectively evaluate the MF symptom burden, compare efficacy of therapies and adjust medications to improve symptom control. Novel targeted agents have proven superior to historic treatment regimens for symptom management. Promising treatment categories include JAK2 inhibitors, histone deacetylase inhibitors, hypomethylating agents, heat shock protein-90 inhibitors, hedgehog inhibitors, PI3-AKT-mTOR inhibitors, antifibrosing agents and telomerase inhibitors. The majority of therapies remain under investigation, either alone or in combination with other treatments. It is anticipated that these agents will be increasingly integrated into standard treatment algorithms for MF symptom management.

Therapeutic benefit of decitabine, a hypomethylating agent, in patients with high-risk primary myelofibrosis and myeloproliferative neoplasm in accelerated or blastic/acute myeloid leukemia phase

Myeloproliferative neoplasm (MPN) transformed to acute myeloid leukemia (MPN-AML), MPN in accelerated phase (MPN-AP), and high-risk primary myelofibrosis (PMF) are associated with a poor response to therapy and very short survival. Several reports have suggested clinical activity of hypomethylating agents in these patients. We conducted a retrospective study of 21 patients with MPN-AML, 13 with MPN-AP and 11 with DIPSS-plus high-risk PMF treated with decitabine at our institution over the last 7 years and evaluated their clinical outcomes. Six patients (29%) with MPN-AML responded to decitabine (3 CR, 2 CRi, and 1 PR); median response duration was 7 months. The median overall survival (OS) was significantly higher in those who responded (10.5 vs 4 months). Among patients with MPN-AP, 8 patients (62%) benefited; the median response duration was 6.5 months. The median OS was 11.8 months in responders vs 4.7 months in non-responders. Among patients with DIPSS-plus high-risk PMF, 9 (82%) benefited; the median response duration was 9 months. The median OS was 32 months in responders vs 16.3 months in non-responders. Decitabine is a viable therapeutic option for patients with MPN-AML, MP-AP and high-risk PMF. Prospective clinical studies combining decitabine with other clinically active agents are needed to improve overall outcome.

Novel therapies for myelofibrosis

Myelofibrosis (MF), including primary, post-essential thrombocythemia and post-polycythemia vera MF, associates with a reduced quality of life and shortened life expectancy. Dysregulation of the Janus kinase (JAK)/signal transducer and activator of transcription (STAT) pathway is prominent, even in the absence of the JAK2(V617F) mutation. Therefore, all symptomatic MF patients may potentially derive benefit from JAK inhibitors. Despite the efficacy of JAK inhibitors in controlling signs and symptoms of MF, they do not eradicate the disease. Therefore, JAK inhibitors are currently being tested in combination with other novel therapies, a strategy which may be more effective in reducing disease burden, either by overcoming JAK inhibitor resistance or targeting additional mechanisms of pathogenesis. Additional targets include modulators of epigenetic regulation, pathways that work downstream from JAK/STAT (i.e. mammalian target of rapamycin/AKT/phosphoinositide 3-kinase) heat shock protein 90, hedgehog signaling, pro-fibrotic factors, abnormal megakaryocytes and telomerase. In this review, we discuss novel MF therapeutic strategies.

Allo-SCT for myelofibrosis: reversing the chronic phase in the JAK inhibitor era?

At present, allo-SCT is the only curative treatment for patients with myelofibrosis (MF). Unfortunately, a significant proportion of candidate patients are considered transplant ineligible due to their poor general condition and advanced age at the time of diagnosis. The approval of the first JAK inhibitor, ruxolitinib, for patients with advanced MF in 2011 has had a qualified impact on the treatment algorithm. The drug affords substantial improvement in MF-associated symptoms and splenomegaly but no major effect on the natural history. There has, therefore, been considerable support for assessing the drug's candidacy in the peritransplant period. The drug's precise impact on clinical outcome following allo-SCT is currently not known; nor are the drug's long-term efficacy and safety known. Considering the rarity of MF and the small proportion of patients who undergo allo-SCT, well designed collaborative efforts are required. In order to address some of the principal challenges, an expert panel of laboratory and clinical experts in this field was established, and an independent workshop held during the 54th American Society of Hematology Annual Meeting in New Orleans, USA on 6 December 2013, and the European Hematology Association's Annual Meeting in Milan, Italy on 13 June 2014. This document summarizes the results of these efforts.

Definition and management of ruxolitinib treatment failure in myelofibrosis

Ruxolitinib, a Janus kinase (JAK)-1 and JAK-2 inhibitor, is the first-in-class drug to be licensed in the United States for the treatment of high- and intermediate-risk myelofibrosis (MF). Several other JAK inhibitors are in development with some currently undergoing phase-3 clinical trial testing. None of the currently available JAK inhibitors are specific to mutant JAK2; their mechanism of action involves attenuation of JAK-STAT signaling with downregulation of proinflammatory cytokines, rather than selective suppression of the disease clone. Accordingly, while ruxolitinib and other JAK inhibitors are effective in controlling splenomegaly and alleviating constitutional symptoms, their benefit in terms of reversing bone marrow fibrosis or inducing complete or partial remissions appears to be limited. The experience to date with ruxolitinib shows that despite its salutary effects on quality of life, over half of the patients discontinue treatment within 2-3 years. In the current perspective, we examine the incidence and causes of ruxolitinib 'treatment failure' in MF patients based on our personal experience as well as a review of the published literature. We also discuss the challenges in defining and classifying ruxolitinib failure, and within the context of several clinical scenarios, we provide recommendations for the post-ruxolitinib management of MF patients.

Epigenetic diversity in hematopoietic neoplasms

Tumor cell populations display a remarkable extent of variability in non-genetic characteristics such as DNA methylation, histone modification patterns, and differentiation levels of individual cells. It remains to be elucidated whether non-genetic heterogeneity is simply a byproduct of tumor evolution or instead a manifestation of a higher-order tissue organization that is maintained within the neoplasm to establish a differentiation hierarchy, a favorable microenvironment, or a buffer against changing selection pressures during tumorigenesis. Here, we review recent findings on epigenetic diversity, particularly heterogeneity in DNA methylation patterns in hematologic malignancies. We also address the implications of epigenetic heterogeneity for the clonal evolution of tumors and discuss its effects on gene expression and other genome functions in cancer.