Janus kinase-1 and Janus kinase-2 inhibitors for treating myelofibrosis

SO2 activates Th17 cells through the JAK1,2/STAT3 signaling pathway

OBJECTIVE

To investigate the effect of SO2 on Th1/Th2/Th17 cells in allergic rhinitis (AR) and the role of JAK1, 2/STAT3 signaling pathways.To Provide potential directions for the treatment of AR.

METHODS

Fifteen AR patients were enrolled as the experimental group, while 15 healthy volunteers served as the normal control group. After collecting venous blood, peripheral blood mononuclear cells (PBMCs) were isolated and cultured, followed by the addition of SO2 derivatives and the JAK inhibitor Ruxolitinib. Flow cytometry was employed to assess alterations in the Th1/Th2 and Th17/Treg cell balance upon stimulation with SO2 and Ruxolitinib. qRT-PCR was utilized to detect the expression of Th1-related cytokines IL-2 and IFN-γ, Th2-related cytokines IL-4 and IL-5, Th17-related cytokines IL-17A and RORγt, as well as genes JAK1, JAK2, and STAT3. Flow cytometric cytokine analysis was conducted for quantitative assessment of the expression levels of inflammation-related cytokines in PBMC culture supernatants after stimulation. In addition, we stimulated the Jurkat T lymphocyte cell line with SO2 derivatives, added Ruxolitinib as an inhibitor, and used Western blot analysis to further determine the effects of SO2 on Th cells and the role of the JAK1,2/STAT3 signaling pathway in this process.

RESULTS

Stimulation with SO2 derivatives upregulated the expression levels of Th2 cells and associated cytokines, as well as Th1 cells and associated cytokines. both AR patients and healthy individuals displayed increased percentages of Th17 cells and Th17/Treg ratios in PBMCs. The expression of IL-17A, RORγt, and IL-6 was also elevated. Under SO2 stimulation, the expression of JAK1, JAK2, STAT3, and RORγt in Jurkat cells increased. Moreover, after the application of Ruxolitinib, the JAK/STAT signaling pathway was inhibited. This led to a reduction in Th17 cells and IL-17A levels in both AR patients and healthy individuals, as well as a decrease in RORγt expression in Jurkat cells. Additionally, the expression of IL-5 decreased in healthy individuals.

CONCLUSION

SO2 exposure exacerbated Th1/Th2/Th17 inflammation in AR patients and induced Th1 and Th17 inflammation in healthy individuals. The stimulatory effect of SO2 on Th17 cell differentiation could be inhibited by Ruxolitinib. This suggests that the Th17 inflammation induced by SO2 stimulation may be related to the activation of the JAK/STAT signaling pathway, and this has been confirmed in the Jurkat cell line.

Addition of ruxolitinib to standard graft-versus-host disease prophylaxis for allogeneic stem cell transplantation in aplastic anemia patients

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) offers rapid hematopoietic and immune reconstitution for aplastic anemia (AA). As a non-malignant disorder, attenuation of GVHD remains a clinical priority in AA patients. Our study sought to investigate the safety and efficacy of the prophylactic use of ruxolitinib in allogeneic HSCT. A total of 35 AA patients were retrospectively consecutively treated with allo-HSCT whereby ruxolitinib was added to the standard GVHD prophylaxis regimen (rux group). The addition of peri-transplant ruxolitinib did not impact the engraftment and graft function, while better recovery of CD4+ Tregs in the rux group was observed. Interestingly, the rux group demonstrated significantly lower incidence of bacterial/fungal infections (17.14% vs 45.71%). Compared to the control group, the rux group exhibited significantly lower incidence of moderate to severe aGVHD (17.1% vs 48.6%) with a trend toward lower severe aGVHD (8.6% vs 20%) and cGVHD (26.2 vs 38.3). The rux group also demonstrated a trend toward higher GVHD and failure-free survival (GFFS: 85.7% vs 68.6%) and lower TRM (2.9% vs 14.3%). Addition of ruxolitinib to standard GVHD prophylaxis regimen, thus, represents a safe and highly efficient method for the attenuation of GVHD with better outcome of allo-HSCT.

Upfront allogeneic transplantation versus JAK inhibitor therapy for patients with myelofibrosis: a North American collaborative study

Allogeneic hematopoietic cell transplantation (HCT) is the only curative therapy for myelofibrosis (MF) and is recommended for patients with higher risk disease. However, there is a risk of early mortality, and optimal timing is unknown. JAK inhibitor (JAKi) therapy may offer durable improvement in symptoms, splenomegaly and quality of life. The aim of this multicentre, retrospective observational study was to compare outcomes of patients aged 70 years or below with MF in chronic phase who received upfront JAKi therapy vs. upfront HCT in dynamic international prognostic scoring system (DIPSS)-stratified categories. For the whole study cohort, median overall survival (OS) was longer for patients who received a JAKi vs. upfront HCT, 69 (95% CI 57-89) vs. 42 (95% CI 20-not reached, NR) months, respectively (p = 0.01). In patients with intermediate-2 and high-risk disease, median OS was 55 (95% CI 36-73) months with JAKi vs. 36 (95% CI 20-NR) months for HCT (p = 0.27). An upfront HCT strategy was associated with early mortality and difference in median OS was not observed in any risk group by 5 years of follow-up. Within the limitations of a retrospective observational study, we did not observe any benefit of a universal upfront HCT approach for higher-risk MF.

Emerging Treatment Options for Myelofibrosis: Focus on Anemia

Myelofibrosis (MF) is a hematologic malignancy characterized by abnormal proliferation of myeloid cells and the release of pro-inflammatory cytokines, leading to progressive bone marrow dysfunction. The introduction of ruxolitinib just over a decade ago marked a significant advancement in MF therapy, with JAK inhibitors now being the first-line treatment for reducing spleen size and managing symptoms. However, early JAK inhibitors (ruxolitinib and fedratinib) are often associated with cytopenias, particularly thrombocytopenia and anemia, which limit their tolerability. To address these complications, pacritinib has been developed and recently approved for patients with thrombocytopenia, while momelotinib is in development for those with anemia. Although JAK inhibitors have significantly improved the quality of life of MF patients, they have not demonstrated the ability to reduce leukemic transformation and their impact on survival is debated. Numerous drugs are currently being developed and investigated in clinical trials, both as standalone therapy and in combination with JAK inhibitors, with promising results enhancing the benefits of JAK inhibitors. In the near future, MF treatment strategies will involve selecting the most suitable JAK inhibitor based on individual patient characteristics and prior therapy. Ongoing and future clinical trials are crucial for advancing the field and expanding therapeutic options for MF patients.

Treating accelerated and blast phase myeloproliferative neoplasms: progress and challenges

Myeloproliferative neoplasms (MPNs) are a group of clonal hematologic malignancies that include polycythemia vera (PV), essential thrombocythemia (ET), and myelofibrosis (MF). MPNs are characterized by activating mutations in the JAK/STAT pathway and an increased risk of transformation to an aggressive form of acute leukemia, termed MPN-blast phase (MPN-BP). MPN-BP is characterized by the presence of ⩾20% blasts in the blood or bone marrow and is almost always preceded by an accelerated phase (MPN-AP) defined as ⩾10-19% blasts in the blood or bone marrow. These advanced forms of disease are associated with poor prognosis with a median overall survival (mOS) of 3-5 months in MPN-BP and 13 months in MPN-AP. MPN-AP/BP has a unique molecular landscape characterized by increased intratumoral complexity. Standard therapies used in de novo acute myeloid leukemia (AML) have not demonstrated improvement in OS. Allogeneic hematopoietic stem cell transplant (HSCT) remains the only curative therapy but is associated with significant morbidity and mortality and infrequently utilized in clinical practice. Therefore, an urgent unmet need persists for effective therapies in this advanced phase patient population. Here, we review the current management and future directions of therapy in MPN-AP/BP.

Novel Therapies in Myelofibrosis: Beyond JAK Inhibitors

PURPOSE OF REVIEW

To discuss the current treatment paradigm, review novel targets, and summarize completed and ongoing clinical trials that may lead to a paradigm shifts in the management of myelofibrosis (MF).

RECENT FINDINGS

In addition to the recent approval and ongoing late-stage development of multiple novel JAK inhibitors, recent clinical studies demonstrate therapeutic potential of targeting multiple alternate proteins and pathways including BET, MDM2, telomerase, BCL2, LSD1, PI3K, SMAC, and PTX2 in patients with MF. MF is a myeloproliferative neoplasm characterized by clonal proliferation of myeloid cells and bone marrow fibrosis often causing cytopenias, extramedullary hematopoiesis resulting in hepatosplenomegaly, and increased pro-inflammatory cytokine production driving systemic symptoms. A significant proportion of morbidity and mortality is related to the propensity to transform to acute leukemia. Allogeneic hematopoietic stem cell transplantation is the only curative therapy; however, due to the high associated mortality, this treatment is not an option for the majority of patients with MF. Currently, there are three targeted Food and Drug Administration (FDA)-approved therapies for MF which include ruxolitinib, fedratinib, and pacritinib, all part of the JAK inhibitor class. Many patients are unable to tolerate, do not respond, or develop resistance to existing therapies, leaving a large unmet medical need. In this review, we discuss the current treatment paradigm and novel therapies in development for the treatment of MF. We review the scientific rationale of each targeted pathway. We summarize updated clinical data and ongoing trials that may lead to FDA approval of these agents.

Role of JAK inhibitors in myeloproliferative neoplasms: current point of view and perspectives

Classic Philadelphia-negative myeloproliferative neoplasms (MPN) include polycythemia vera (PV), essential thrombocythemia (ET), and myelofibrosis (MF), classified as primary (PMF), or secondary to PV or ET. All MPN, regardless of the underlying driver mutation in JAK2/CALR/MPL, are invariably associated with dysregulation of JAK/STAT pathway. The discovery of JAK2V617F point mutation prompted the development of small molecules inhibitors of JAK tyrosine kinases (JAK inhibitors-JAKi). To date, among JAKi, ruxolitinib (RUX) and fedratinib (FEDR) are approved for intermediate and high-risk MF, and RUX is also an option for high-risk PV patients inadequately controlled by or intolerant to hydroxyurea. While not yet registered, pacritinib (PAC) and momelotinib (MMB), proved to be effective particularly in thrombocytopenic and anemic MF patients, respectively. In most cases, JAKi are effective in reducing splenomegaly and alleviating disease-related symptoms. However, almost 50% lose response by three years and dose-dependent toxicities may lead to suboptimal dosing or treatment discontinuation. To date, although not being disease-modifying agents, JAKi represent the therapeutic backbone particularly in MF patient. To optimize therapeutic strategies, many trials with drug combinations of JAKi with novel molecules are ongoing. This review critically discusses the role of JAKi in the modern management of patients with MPN.

Clinical Efficacy of Ruxolitinib in Patients with Myelofibrosis: A Nationwide Population-Based Study in Korea

Previous studies have reported the survival benefit after ruxolitinib treatment in patients with myelofibrosis (MF). However, population-based data of its efficacy are limited. We analyzed the effects of ruxolitinib in MF patients with data from the Korean National Health Insurance Database. In total, 1199 patients diagnosed with MF from January 2011 to December 2017 were identified, of which 731 were included in this study. Patients who received ruxolitinib (n = 224) were matched with those who did not receive the drug (n = 507) using the 1:1 greedy algorithm. Propensity scores were formulated using five variables: age, sex, previous history of arterial/venous thrombosis, and red blood cell (RBC) or platelet (PLT) transfusion dependence at the time of diagnosis. Cox regression analysis for overall survival (OS) revealed that ruxolitinib treatment (hazard ratio (HR), 0.67; p = 0.017) was significantly related to superior survival. In the multivariable analysis for OS, older age (HR, 1.07; p < 0.001), male sex (HR, 1.94; p = 0.021), and RBC (HR, 3.72; p < 0.001) or PLT (HR, 9.58; p = 0.001) transfusion dependence were significantly associated with poor survival, although type of MF did not significantly affect survival. Considering evidence supporting these results remains weak, further studies on the efficacy of ruxolitinib in other populations are needed.

Clinical Utility of Fedratinib in Myelofibrosis

Myelofibrosis (MF) is a clonal hematologic malignancy characterized by bone marrow fibrosis, extramedullary hematopoiesis, splenomegaly, and constitutional symptoms with a propensity towards leukemic transformation. Constitutive activation of the JAK/STAT pathway is a well-described pathogenic feature of MF. Allogeneic stem cell transplant is the only curative therapy, but due to high morbidity and mortality this option is not available for most patients. There are two approved targeted therapy options for MF, ruxolitinib and fedratinib. In this review, we discuss the clinical utility of fedratinib in the myelofibrosis treatment paradigm. Fedratinib has shown impressive pre-clinical and clinical efficacy in patients with untreated MF as well as in those with ruxolitinib intolerance and those with relapsed/refractory MF. Here, we review the pre-clinical and clinical trials that led to the approval of fedratinib, and the ongoing late-phase trials. We highlight several areas regarding the clinical utility of fedratinib that remain unanswered. We discuss the limitations of fedratinib and address areas that are understudied and require further clinical evaluation and research. The approval of fedratinib has provided a significant expansion to the very limited treatment armamentarium available to patients with MF.

A Broad Overview of Signaling in Ph-Negative Classic Myeloproliferative Neoplasms

Simple Summary

There is growing evidence that Ph-negative myeloproliferative neoplasms are disorders in which multiple signaling pathways are significantly disturbed. The heterogeneous phenotypes observed among patients have highlighted the importance of having a comprehensive knowledge of the molecular mechanisms behind these diseases. This review aims to show a broad overview of the signaling involved in myeloproliferative neoplasms (MPNs) and other processes that can modify them, which could be helpful to better understand these diseases and develop more effective targeted treatments.

Abstract

Ph-negative myeloproliferative neoplasms (polycythemia vera (PV), essential thrombocythemia (ET) and primary myelofibrosis (PMF)) are infrequent blood cancers characterized by signaling aberrations. Shortly after the discovery of the somatic mutations in JAK2, MPL, and CALR that cause these diseases, researchers extensively studied the aberrant functions of their mutant products. In all three cases, the main pathogenic mechanism appears to be the constitutive activation of JAK2/STAT signaling and JAK2-related pathways (MAPK/ERK, PI3K/AKT). However, some other non-canonical aberrant mechanisms derived from mutant JAK2 and CALR have also been described. Moreover, additional somatic mutations have been identified in other genes that affect epigenetic regulation, tumor suppression, transcription regulation, splicing and other signaling pathways, leading to the modification of some disease features and adding a layer of complexity to their molecular pathogenesis. All of these factors have highlighted the wide variety of cellular processes and pathways involved in the pathogenesis of MPNs. This review presents an overview of the complex signaling behind these diseases which could explain, at least in part, their phenotypic heterogeneity.

Challenges and Perspectives for Therapeutic Targeting of Myeloproliferative Neoplasms

Myeloproliferative neoplasms (MPNs) are hematopoietic stem cell disorders with dysregulated myeloid blood cell production and propensity for transformation to acute myeloid leukemia, thrombosis, and bleeding. Acquired mutations in JAK2, MPL, and CALR converge on hyperactivation of Janus kinase 2 (JAK2) signaling as a central feature of MPN. Accordingly, JAK2 inhibitors have held promise for therapeutic targeting. After the JAK1/2 inhibitor ruxolitinib, similar JAK2 inhibitors as fedratinib are entering clinical use. While patients benefit with reduced splenomegaly and symptoms, disease-modifying effects on MPN clone size and clonal evolution are modest. Importantly, response to ruxolitinib may be lost upon treatment suggesting the MPN clone acquires resistance. Resistance mutations, as seen with other tyrosine kinase inhibitors, have not been described in MPN patients suggesting that functional processes reactivate JAK2 signaling. Compensatory signaling, which bypasses JAK2 inhibition, and other processes contribute to intrinsic resistance of MPN cells restricting efficacy of JAK2 inhibition overall. Combinations of JAK2 inhibition with pegylated interferon-α, a well-established therapy of MPN, B-cell lymphoma 2 inhibition, and others are in clinical development with the potential to enhance therapeutic efficacy. Novel single-agent approaches targeting other molecules than JAK2 are being investigated clinically. Special focus should be placed on myelofibrosis patients with anemia and thrombocytopenia, a delicate patient population at high need for options. The extending range of new treatment approaches will increase the therapeutic options for MPN patients. This calls for concomitant improvement of our insight into MPN biology to inform tailored therapeutic strategies for individual MPN patients.

Clinical relevance of endpoints in clinical trials for acid sphingomyelinase deficiency enzyme replacement therapy

BACKGROUND

Acid sphingomyelinase deficiency (ASMD) also known as Niemann-Pick disease, is a rare lysosomal storage disorder with a diverse disease spectrum that includes slowly progressive, chronic visceral (type B) and neurovisceral forms (intermediate type A/B), in addition to infantile, rapidly progressive fatal neurovisceral disease (type A).

PURPOSE AND METHODS

We review the published evidence on the relevance of splenomegaly and reduced lung diffusion capacity to the clinical burden of chronic forms of ASMD. Targeted literature searches were conducted to identify relevant ASMD and non-ASMD studies for associations between diffusing capacity of the lungs for carbon monoxide (DL_CO) and splenomegaly, with clinical parameters and outcome measures.

RESULTS

Respiratory disease and organomegaly are primary and independent contributors to mortality, disease burden, and morbidity for patients with chronic ASMD. The degree of splenomegaly correlates with short stature, atherogenic lipid profile, and degree of abnormality of hematologic parameters, and thus may be considered a surrogate marker for bleeding risk, abnormal lipid profiles and possibly, liver fibrosis. Progressive lung disease is a prevalent clinical feature of chronic ASMD, contributing to a decreased quality of life (QoL) and an increased disease burden. In addition, respiratory-related complications are a major cause of mortality in ASMD.

CONCLUSIONS

The reviewed evidence from ASMD natural history and observational studies supports the use of lung function and spleen volume as clinically meaningful endpoints in ASMD trials that translate into important measures of disease burden for patients.

JAK Inhibition for the Treatment of Myelofibrosis: Limitations and Future Perspectives

The 2011 approval of ruxolitinib ushered in the Janus kinase (JAK) inhibitor era in the treatment of myelofibrosis (MF), and 2019 saw the US approval of fedratinib. The first therapeutic agents approved by regulatory authorities for MF, these drugs attenuate the overactive JAK-signal transducer and activator of transcription (STAT) signaling universally present in these patients, translating into major clinical benefits in terms of spleen shrinkage and symptom improvement. These, in turn, confer a survival advantage on patients with advanced disease, demonstrated in the case of ruxolitinib, for which long-term follow-up data are available. However, JAK inhibitors do not improve cytopenias in most patients, have relatively modest effects on bone marrow fibrosis and driver mutation allele burden, and clinical resistance eventually develops. Furthermore, they do not modify the risk of transformation to blast phase; indeed, their mechanism of action may be more anti-inflammatory than truly disease-modifying. This has spurred interest in rational combinations of JAK inhibitors with other agents that may improve cytopenias and drugs that could potentially modify the natural history of MF. Newer JAK inhibitors that are distinguished from ruxolitinib and fedratinib by their ability to improve anemia (eg, momelotinib) or safety and efficacy in severely thrombocytopenic patients (eg, pacritinib) are in phase 3 clinical trials. There is also interest in developing inhibitors that are highly selective for mutant JAK2, as well as "type II" JAK2 inhibitors. Overall, although current JAK inhibitors have limitations, they will likely continue to form the backbone of MF therapy for the foreseeable future.

Standard care and investigational drugs in the treatment of myelofibrosis

Myelofibrosis (MF) is a heterogeneous disorder characterized by splenomegaly, constitutional symptoms, ineffective hematopoiesis, and an increased risk of leukemic transformation. The ongoing research in understanding the pathophysiology of the disease has allowed for the development of targeted drugs optimizing patient management. Furthermore, disease prognostication has significantly improved. Current therapeutic interventions are only partially effective with only allogeneic stem cell transplant potentially curative. Ruxolitinib is the only approved therapy for MF by the US Food and Drug Administration. However, despite efficacy in reducing splenomegaly and controlling symptomatology, it is not associated with consistent molecular or pathologic responses. Drug discontinuation is associated with a dismal outcome. The therapeutic landscape in MF has significantly improved, and emerging drugs with different target pathways, alone or in combination with ruxolitinib, seem promising.

Survival outcomes in myelofibrosis patients treated with ruxolitinib: A population-based cohort study in Sweden and Norway

Objective

To estimate survival in Swedish and Norwegian myelofibrosis (MF) patients who received ruxolitinib.

Methods

Swedish and Norwegian patients with MF diagnosis in the National Cancer Registries (Sweden: 2001‐2015; Norway: 2002‐2016) and ≥1 record of ruxolitinib in the Prescribed Drug Registries (2013‐2017) were included. Patients were followed from ruxolitinib initiation until death or end of follow‐up; those who discontinued ruxolitinib were followed from ruxolitinib discontinuation. Relative survival (RS) and excess mortality rate ratios (EMRRs) were calculated vs a matched general population. Average loss in life expectancy (LEL) was predicted using flexible parametric models.

Results

Among patients who initiated ruxolitinib (n = 190), 1‐ and 4‐year RS were 0.80 (95% confidence interval [CI]: 0.74, 0.86) and 0.52 (95% CI: 0.42, 0.64), respectively, and LEL was 11 years. EMRR was greater in patients aged >70 vs <60 years (3.16; 95% CI: 1.34‐7.40). Among patients who discontinued ruxolitinib (n = 71), median RS was 16.0 months (95% CI: 6.3, NE), and LEL was 12 years. After ruxolitinib treatment discontinuation, Swedish patients (n = 37) received glucocorticoids, hydroxyurea, busulfan, danazol and lenalidomide.

Conclusion

Swedish and Norwegian MF patients who discontinued ruxolitinib had dismal survival outcomes and limited subsequent treatment options, highlighting the need for improved therapies.

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.

Reduced intensity allogeneic stem cell transplantation for younger patients with myelofibrosis

Allogeneic stem cell transplantation (alloSCT) is a curative procedure for myelofibrosis. Elderly people are mainly affected, limiting the feasibility of myeloablative regimens. The introduction of reduced-intensity conditioning (RIC) made alloSCT feasible for older patients. Nevertheless, the incidence of myelofibrosis is not negligible in young patients, who are theoretically able to tolerate high-intensity therapy. Very few data are available about the efficacy of RIC-alloSCT in younger myelofibrosis patients. This study included 56 transplanted patients aged <55 years. Only 30% had a human leucocyte antigen (HLA)-matched sibling donor, the others were transplanted from a fully-matched (36%) or partially-matched (34%) unrelated donor. All transplants were conditioned according the European Society for Blood and Marrow Transplantation protocol: busulfan-fludarabine + anti-thymocyte globulin, followed by ciclosporin and mycophenolate. One patient experienced primary graft failure. Incidence of graft-versus-host disease grade II-IV was 44% (grade III/IV 23%). One-year non-relapse mortality was 7% and the 5-year cumulative incidence of relapse was 19%. After a median follow-up of 8·6 years, the estimated 5-year progression-free survival and overall survival (OS) was 68% and 82%, respectively. Patients with fully-matched donor had a 5-year OS of 92%, in contrast to 68% for those with a mismatched donor (P = 0·03). The most important outcome-determining factor is donor HLA-matching. In conclusion, RIC-alloSCT ensures optimal engraftment and low relapse rate in younger myelofibrosis patients, enabling the possibility of cure in this group.

The ruxolitinib effect: understanding how molecular pathogenesis and epigenetic dysregulation impact therapeutic efficacy in myeloproliferative neoplasms

The myeloproliferative neoplasms (MPN), polycythaemia vera (PV), essential thrombocythemia (ET) and primary myelofibrosis (PMF) are linked by a propensity to thrombosis formation and a risk of leukaemic transformation. Activation of cytokine independent signalling through the JAK/STAT cascade is a feature of these disorders. A point mutation in exon 14 of the JAK2 gene resulting in the formation of the JAK2 V617F transcript occurs in 95% of PV patients and around 50% of ET and PMF patients driving constitutive activation of the JAK/STAT pathway. Mutations in CALR or MPL are present as driving mutations in the majority of remaining ET and PMF patients. Ruxolitinib is a tyrosine kinase inhibitor which inhibits JAK1 and JAK2. It is approved for use in intermediate and high risk PMF, and in PV patients who are resistant or intolerant to hydroxycarbamide. In randomised controlled trials it has demonstrated efficacy in spleen volume reduction and symptom burden reduction with a moderate improvement in overall survival in PMF. In PV, there is demonstrated benefit in haematocrit control and spleen volume. Despite these benefits, there is limited impact to induce complete haematological remission with normalisation of blood counts, reduce the mutant allele burden or reverse bone marrow fibrosis. Clonal evolution has been observed on ruxolitinib therapy and transformation to acute leukaemia can still occur. This review will concentrate on understanding the clinical and molecular effects of ruxolitinib in MPN. We will focus on understanding the limitations of JAK inhibition and the challenges to improving therapeutic efficacy in these disorders. We will explore the demonstrated benefits and disadvantages of ruxolitinib in the clinic, the role of genomic and clonal variability in pathogenesis and response to JAK inhibition, epigenetic changes which impact on response to therapy, the role of DNA damage and the role of inflammation in these disorders. Finally, we will summarise the future prospects for improving therapy in MPN in the JAK inhibition era.

Classical Philadelphia-negative myeloproliferative neoplasms: focus on mutations and JAK2 inhibitors

Classical Philadelphia- negative myeloproliferative neoplasms (MPNs) encompass three main myeloid malignancies: polycythemia vera (PV), essential thrombocythemia (ET), and myelofibrosis (MF). Phenotype-driver mutations in Janus kinase 2 (JAK2), calreticulin (CALR), and myeloproliferative leukemia virus oncogene (MPL) genes are mutually exclusive and occur with a variable frequency. Driver mutations influence disease phenotype and prognosis. PV patients with JAK2 exon 14 mutation do not differ in number of thrombotic events, risk of leukemic and fibrotic transformation, and overall survival to those with JAK2 exon 12 mutation. Type 2-like CALR-mutated ET patients have lower risk of thrombosis if compared with those carrying JAK2 or type 1-like CALR mutation. For ET, overall survival is comparable between patients with JAK2 and either type 1-like and type 2-like CALR mutations. For MF, better OS is demonstrated for patients harboring a type 1-like CALR mutation than those with type 2-like CALR or JAK2. The discovery of driver mutations in MPNs has prompted the development of molecularly targeted therapy. Among JAK2 inhibitors, ruxolitinib (RUX) has been approved for (1) treatment of intermediate-2 and high-risk MF and (2) PV patients who are resistant to or intolerant to hydroxyurea. RUX reduces spleen size and alleviates disease symptoms in a proportion of MF patients. RUX in MF leads to prolonged survival and reduces risk of death. RUX controls hematocrit, reduces spleen size and alleviates symptoms in PV. Adverse events of RUX are moderate, however, its long-term use may be associated with opportunistic infections. Trials with other JAK2 inhibitors are ongoing.

Cancer immune therapy for myeloid malignancies: present and future

The myelodysplastic syndromes, the chronic myeloproliferative neoplasms, and the acute myeloid leukemia are malignancies of the myeloid hematopoietic stem cells of the bone marrow. The diseases are characterized by a dysregulation of the immune system as both the cytokine milieu, immune phenotype, immune regulation, and expression of genes related to immune cell functions are deregulated. Several treatment strategies try to circumvent this deregulation, and several clinical and preclinical trials have shown promising results, albeit not in the same scale as chimeric antigen receptor T cells have had in the treatment of refractory lymphoid malignancies. The use of immune checkpoint blocking antibodies especially in combination with hypomethylating agents has had some success-a success that will likely be enhanced by therapeutic cancer vaccination with tumor-specific antigens. In the chronic myeloproliferative neoplasms, the recent identification of immune responses against the Januskinase-2 and calreticulin exon 9 driver mutations could also be used in the vaccination setting to enhance the anti-tumor immune response. This immune response could probably be enhanced by the concurrent use of immune checkpoint inhibitors or by vaccination with epitopes from immune regulatory proteins such as arginase-1 and programmed death ligand-1. Herein, we provide an overview of current cancer immune therapeutic treatment strategies as well as potential future cancer immune therapeutic treatment options for the myeloid malignancies.

Philadelphia chromosome-negative classical myeloproliferative neoplasms: revised management recommendations from European LeukemiaNet

This document updates the recommendations on the management of Philadelphia chromosome-negative myeloproliferative neoplasms (Ph-neg MPNs) published in 2011 by the European LeukemiaNet (ELN) consortium. Recommendations were produced by multiple-step formalized procedures of group discussion. A critical appraisal of evidence by using Grades of Recommendation, Assessment, Development and Evaluation (GRADE) methodology was performed in the areas where at least one randomized clinical trial was published. Seven randomized controlled trials provided the evidence base; earlier phase trials also informed recommendation development. Key differences from the 2011 diagnostic recommendations included: lower threshold values for hemoglobin and hematocrit and bone marrow examination for diagnosis of polycythemia vera (PV), according to the revised WHO criteria; the search for complementary clonal markers, such as ASXL1, EZH2, IDH1/IDH2, and SRSF2 for the diagnosis of myelofibrosis (MF) in patients who test negative for JAK2V617, CALR or MPL driver mutations. Regarding key differences of therapy recommendations, both recombinant interferon alpha and the JAK1/JAK2 inhibitor ruxolitinib are recommended as second-line therapies for PV patients who are intolerant or have inadequate response to hydroxyurea. Ruxolitinib is recommended as first-line approach for MF-associated splenomegaly in patients with intermediate-2 or high-risk disease; in case of intermediate-1 disease, ruxolitinib is recommended in highly symptomatic splenomegaly. Allogeneic stem cell transplantation is recommended for transplant-eligible MF patients with high or intermediate-2 risk score. Allogeneic stem cell transplantation is also recommended for transplant-eligible MF patients with intermediate-1 risk score who present with either refractory, transfusion-dependent anemia, blasts in peripheral blood > 2%, adverse cytogenetics, or high-risk mutations. In these situations, the transplant procedure should be performed in a controlled setting.

Benefits and pitfalls of pegylated interferon-α2a therapy in patients with myeloproliferative neoplasm-associated myelofibrosis: a French Intergroup of Myeloproliferative neoplasms (FIM) study

We have previously described the safety and efficacy of pegylated interferon-α2a therapy in a cohort of 62 patients with myeloproliferative neoplasm-associated myelofibrosis followed in centers affiliated to the French Intergroup of Myeloproliferative neoplasms. In this study, we report their long-term outcomes and correlations with mutational patterns of driver and non-driver mutations analyzed by targeted next generation sequencing. The median age at diagnosis was 66 years old, the median follow-up since starting pegylated interferon was 58 months. At the time of analysis, 30 (48.4%) patients were alive including 16 still being treated with pegylated interferon. The median survival of patients with intermediate and high-risk prognostic Lille and dynamic International Prognostic Scoring System scores treated with pegylated interferon was increased in comparison to that of historical cohorts. In addition, overall survival was significantly correlated with the duration of pegylated interferon therapy (70 versus 30 months after 2 years of treatment, P<10⁻¹²). JAK2^V617F allele burden was decreased by more than 50% in 58.8% of patients and two patients even achieved complete molecular response. Next-generation sequencing analyses performed in 49 patients showed that 28 (57.1%) of them carried non-driver mutations. The presence of at least one additional mutation was associated with a reduction of both overall and leukemia-free survival. These findings in a large series of patients with myelofibrosis suggest that pegylated interferon therapy may provide a survival benefit for patients with intermediate- or high-risk Lille and dynamic International Prognostic Scoring System scores. It also reduced the JAK2^V617F allele burden in most patients. These results further support the use of pegylated interferon in selected patients with myelofibrosis.

The BCR-ABL1-negative myeloproliferative neoplasms: a review of JAK inhibitors in the therapeutic armamentarium

INTRODUCTION

The classical BCR-ABL1-negative myeloproliferative neoplasms (MPN) include primary myelofibrosis (PMF), polycythemia vera (PV) and essential thrombocythemia (ET). They are characterized by stem cell-derived clonal proliferation, harbor Janus kinase 2 (JAK2), or calreticulin (CALR), or myeloproliferative leukemia virus oncogene (MPL) driver mutations and exert an over activated JAK-signal transducer and activator of transcription (STAT) pathway. Therefore JAK inhibiting strategies have been successfully investigated in MPN clinical trials. Areas covered: The present review aims to provide a concise overview of the current and future role of JAK inhibitors in the therapeutic armamentarium of MPN. Expert opinion: The JAK1/JAK2 inhibitor ruxolitinib has clearly enriched the therapeutic armamentarium of MPN and is now licenced for more than five years in MF and over three years as second line in PV. Momelotinib, although of limited activity in MPN trials, demonstrated unique property of improving MF associated anemia. Less myelosuppressive or more selective JAK inhibitors like pacritinib, NS-01872 or Itacitinib are new promising agents tested in MF. JAK inhibition has become a cornerstone of MPN therapy and future efforts focus on ruxolitinib-based combinations and new JAK inhibitors.

Ruxolitinib for the management of myelofibrosis: Results of an international physician survey

BACKGROUND

Ruxolitinib is established as treatment for symptomatic myeloproliferative neoplasm (MPN)-associated myelofibrosis. The strict inclusion and exclusion criteria and dose modification rules that applied to the COMFORTI and II studies that led to the licensing of ruxolitinib are not always applicable to routine clinical practice. Thus physicians now face decisions regarding ruxolitinib use that were not addressed in these pivotal trials.

METHODS

We performed an online survey of hematologists practicing in Europe, Israel, the United Kingdom and the United States. Demographic details regarding the physicians and their practice as relates to MPNs were collected. Management decisions pertaining to the use of ruxolitinib were obtained regarding 10 clinical scenarios relating to anemia, thrombocytopenia, frailty, infection and lack or loss of response to ruxolitnib in MF patients.

RESULTS

140 physicians responded to the survey. There were marked differences regarding their decisions for ruxolitinib administration in MF patients with or developing anemia or thrombocytopenia. Similarly there was little consensus regarding management of patients refractory or losing a response to ruxolitinib. There were differences between "MPN-focused" and "non-MPN-focused" physicians in certain areas.

CONCLUSION

Physician practices regarding management of MF patients experiencing ruxolitinib-related toxicities or in whom response to the drug is lost was variable. This was true of "MPN-focused" and "non-MPN-focused" physicians in certain cases. Physician education and experience in using ruxolitinib may improve patient management.

Fatal ruxolitinib-related JC virus meningitis

We report a possible association between ruxolitinib and JC virus meningitis. A 72-year-old man with myelofibrosis started treatment with ruxolitinib. Fourteen days later, the patient presented to the emergency department with fever and nausea. HIV test was negative. Ruxolitinib was suspended. Symptoms progressed with neck stiffness, cognitive impairment, and motor aphasia. CSF was positive for JC virus. MRI showed nonspecific abnormal findings. Five days after the clinical debut, the patient died. The clinical picture, MRI imaging, and positive JC virus PCR in CSF strongly suggest ruxolitinib-related JC virus meningitis.

Fatal ruxolitinib-related JC virus meningitis

We report a possible association between ruxolitinib and JC virus meningitis. A 72-year-old man with myelofibrosis started treatment with ruxolitinib. Fourteen days later, the patient presented to the emergency department with fever and nausea. HIV test was negative. Ruxolitinib was suspended. Symptoms progressed with neck stiffness, cognitive impairment, and motor aphasia. CSF was positive for JC virus. MRI showed nonspecific abnormal findings. Five days after the clinical debut, the patient died. The clinical picture, MRI imaging, and positive JC virus PCR in CSF strongly suggest ruxolitinib-related JC virus meningitis.

Ruxolitinib in myelofibrosis: to be or not to be an immune disruptor

Primary myelofibrosis (PMF) is a myeloproliferative neoplasm classified according to the 2016 revision of World Health Organization Classification of Tumors and Haematopoietic and Lymphoid Tissue. Ruxolitinib is an oral inhibitor of Janus kinase approved in the USA for the treatment of intermediate or high-risk PMF and approved in Europe for the treatment of splenomegaly and constitutional symptoms of the disease. More recently, case reports described serious opportunistic infections in this neoplasm treated with ruxolitinib. Research studies demonstrated the immunological derangement of this compound mainly based on T, dendritic, and natural killer cell defects. The purpose of this review of the literature was to analyze the relationship among ruxolitinib, immune system and bacterial, viral, fungal, and protozoan infections. A literature search was conducted using PubMed articles published between January 2010 and November 2016. The efficacy of drug in patients with PMF was demonstrated in two phase III studies, Controlled MyeloFibrosis Study with ORal Jak inhibitor Treatment (COMFORT-I and COMFORT-II). Grade 3 and 4 neutropenia were recognized in 7.1% and 2% of patients in the ruxolitinib and placebo arm of COMFORT-I. Grade 3 or 4 neutropenia or leukopenia were observed in 8.9% and 6.3% of ruxolitinib treated patients of 5-year follow-up of COMFORT-II. In addition, leukocyte subpopulations, lymphocyte functions, or antibody deficiency were not documented in either of the studies. The complex interactions between ruxolitinib, bone marrow, immune system, and infections in PMF need further investigation, robust data from a randomized clinical trial, registry, or large case-series.

Oral ruxolitinib induces hair regrowth in patients with moderate-to-severe alopecia areata

BACKGROUND. Alopecia areata (AA) is a common autoimmune disease with a lifetime risk of 1.7%; there are no FDA-approved treatments for AA. We previously identified a dominant IFN-γ transcriptional signature in cytotoxic T lymphocytes (CTLs) in human and mouse AA skin and showed that treatment with JAK inhibitors induced durable hair regrowth in mice by targeting this pathway. Here, we investigated the use of the oral JAK1/2 inhibitor ruxolitinib in the treatment of patients with moderate-to-severe AA. METHODS. We initiated an open-label clinical trial of 12 patients with moderate-to-severe AA, using oral ruxolitinib, 20 mg twice per day, for 3-6 months of treatment followed by 3 months follow-up off drug. The primary endpoint was the proportion of subjects with 50% or greater hair regrowth from baseline to end of treatment. RESULTS. Nine of twelve patients (75%) demonstrated a remarkable response to treatment, with average hair regrowth of 92% at the end of treatment. Safety parameters remained largely within normal limits, and no serious adverse effects were reported. Gene expression profiling revealed treatment-related downregulation of inflammatory markers, including signatures for CTLs and IFN response genes and upregulation of hair-specific markers. CONCLUSION. In this pilot study, 9 of 12 patients (75%) treated with ruxolitinib showed significant scalp hair regrowth and improvement of AA. Larger randomized controlled trials are needed to further assess the safety and efficacy of ruxolitinib in the treatment of AA. TRIAL REGISTRATION. Clinicaltrials.gov NCT01950780. FUNDING. Locks of Love Foundation, the Alopecia Areata Initiative, NIH/National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS), and the Irving Institute for Clinical and Translational Research/Columbia University Medical Center Clinical and Translational Science Award (CUMC CTSA).

Primary myelofibrosis: current therapeutic options

Primary myelofibrosis is a Philadelphia-negative myeloproliferative neoplasm characterized by clonal myeloid expansion, followed by progressive fibrous connective tissue deposition in the bone marrow, resulting in bone marrow failure. Clonal evolution can also occur, with an increased risk of transformation to acute myeloid leukemia. In addition, disabling constitutional symptoms secondary to the high circulating levels of proinflammatory cytokines and hepatosplenomegaly frequently impair quality of life. Herein the main current treatment options for primary myelofibrosis patients are discussed, contemplating disease-modifying therapeutics in addition to palliative measures, in an individualized patient-based approach.

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.

Setting Appropriate Goals for the Next Generation of Clinical Trials in Myelofibrosis

New targeted therapies administered in phase II and phase III studies have produced substantial improvements in outcomes of myelofibrosis (MF). However, strong documentation that the new agents modify the natural history of the disease is lacking, and a number of therapeutic indications of new drugs remain unaddressed. Overall survival (OS) improvement is the major goal of next-generation clinical trials in MF. This may be attained if an adequate population of patients and an unambiguous design of the trial will be selected. Another goal is preventing disease progression in early MF: this requires a controlled clinical trial with an accessible endpoint and a clinically relevant definition of disease progression. Improvement in the documentation of responsiveness of patient-reported outcomes (PROs) will allow to use them as a critical endpoint of new trials. Finally, exploiting the clinical utility of biomarkers should become a major goal of future clinical experimentation in MF.