The Next Generation of JAK Inhibitors: an Update on Fedratinib, Momelotonib, and Pacritinib

The Role of the JAK-STAT Pathway in Childhood B-Cell Acute Lymphoblastic Leukemia

B-cell lymphoblastic leukemia is a hematologic neoplasm that poses a serious health concern in childhood. Genetic aberrations, such as mutations in the genes IL-7, IL7R, JAK1, JAK2, TLSP, CRLF2, and KTM2A or gene fusions involving BCR::ABL1, ETV6::RUNX1, and PAX5::JAK2, often correlate with the onset of this disease. These aberrations can lead to malfunction of the JAK-STAT signaling pathway, which is implicated in various important biological processes, including those related to immunology. Understanding the mechanisms underlying the malfunction of the JAK-STAT pathway holds potential for research on drugs targeting its components. Available drugs that interfere with the JAK-STAT pathway include fludarabine, ruxolitinib, and fedratinib.

Design, Synthesis, and Antitumor Efficacy of Substituted 2-Amino[1,2,4]triazolopyrimidines and Related Heterocycles as Dual Inhibitors for Microtubule Polymerization and Janus Kinase 2

Preclinical and clinical studies have demonstrated the synergistic effect of microtubule-targeting agents in combination with Janus kinase 2 (JAK2) inhibitors, prompting the development of single agents with enhanced therapeutic efficacy by dually inhibiting tubulin polymerization and JAK2. Herein, we designed and synthesized a series of substituted 2-amino[1,2,4]triazolopyrimidines and related heterocycles as dual inhibitors for tubulin polymerization and JAK2. Most of these compounds exhibited potent antiproliferative activity against the selected cancer cells, with compound 7g being the most active. This compound effectively inhibits both tubulin assembly and JAK2 activity. Furthermore, phosphorylated compound 7g (i.e., compound 7g-P) could efficiently convert to compound 7g in vivo. Compound 7g, whether it was administered directly or in the form of a phosphorylated prodrug (i.e., compound 7g-P), significantly inhibited the growth of A549 xenografts in nude mice. The present findings strongly suggest that compound 7g represents a promising chemotherapeutic agent with high antitumor efficacy.

Profiling of mouse and human liver diseases identifies targets for therapeutic treatment of autoimmune hepatitis

Autoimmune hepatitis (AIH), primary sclerosing cholangitis (PSC), and non-alcoholic steatohepatitis (NASH) are chronic liver diseases (CLDs) of distinct etiologies that represent a public health risk with limited therapeutic options. A common feature among CLDs is an aggressive T cell response resulting in destruction of liver tissue and fibrosis. Here, we assessed the presence and nature of T cell inflammation in late-stage human AIH, PSC and NASH and examined whether targeting the T cell response can improve disease pathology in a mouse model (Traf6ΔTEC) of spontaneous AIH. T cell infiltration and ensuing inflammatory pathways were present in human AIH and PSC and to a lesser extent in NASH. However, we observed qualitative differences in infiltrating T cell subsets and upregulation of inflammatory pathways among these diseases, while mouse and human AIH exhibited similar immunogenic signatures. While gene expression profiles differed among diseases, we identified 52 genes commonly upregulated across all diseases that included the JAK3 tyrosine kinase. Therapeutic targeting of chronic AIH with the JAK inhibitor tofacitinib reduced hepatic T cell infiltration, AIH histopathology and associated immune parameters in treated Traf6ΔTEC mice. Our results indicate that targeting T cell responses in established hepatic autoimmune inflammation is a feasible strategy for developing novel therapeutic approaches to treat AIH and possibly other CLDs irrespective of etiology.

New drug approvals for 2022: Synthesis and clinical applications

The U.S. Food and Drug Administration has approved a total of 37 new drugs in 2022, which are composed of 20 chemical entities and 17 biologics. In particular, 20 chemical entities, including 17 small molecule drugs, 1 radiotherapy, and 2 diagnostic agents, provide privileged scaffolds, breakthrough clinical benefits, and a new mechanism of action for the discovery of more potent clinical candidates. The structure-based drug development with clear targets and fragment-based drug development with privileged scaffolds have always been the important modules in the field of drug discovery, which could easily bypass the patent protection and bring about improved biological activity. Therefore, we summarized the relevant valuable information about clinical application, mechanism of action, and chemical synthesis of 17 newly approved small molecule drugs in 2022. We hope this timely and comprehensive review could bring about creative and elegant inspiration on the synthetic methodologies and mechanism of action for the discovery of new drugs with novel chemical scaffolds and extended clinical indications.

Safety and efficacy of jaktinib (a novel JAK inhibitor) in patients with myelofibrosis who are intolerant to ruxolitinib: A single-arm, open-label, phase 2, multicenter study

Although ruxolitinib improves splenomegaly and constitutional symptoms in patients with myelofibrosis (MF), a substantial proportion of patients discontinue ruxolitinib because of intolerance. This phase 2 trial investigated the safety and efficacy of jaktinib, a novel JAK inhibitor in patients with ruxolitinib-intolerant MF. The primary endpoint was the proportion of patients with ≥35% reduction in spleen volume (SVR35) at week 24. The secondary endpoints included change of MF-related symptoms, anemic response, and safety profiles. Between December 18, 2019, and November 24, 2021, 51 patients were enrolled, 45 treated with jaktinib 100 mg bid (100 mg bid group) and six received non-100 mg bid doses (non-100 mg bid group). The SVR35 at week 24 in the 100 mg bid group was 43.2% (19/44, 95% CI 29.7%-57.8%). There were 41.9% (13/31) of transfusion-independent patients with hemoglobin (HGB) ≤100 g/L who had HGB elevation ≥20 g/L within 24 weeks. The proportion of patients with a ≥50% decrease in the total symptom score (TSS 50) at week 24 was 61.8% (21/34). The most commonly reported grade ≥3 treatment-emergent adverse events (TEAEs) in the 100 mg bid group were anemia 31.1%, thrombocytopenia 22.2%, and infectious pneumonia 17.8%. A total of 16 (35.6%) in the 100 mg bid group had serious adverse events, and 4 (8.9%) were considered possibly drug related. These results indicate jaktinib can provide a treatment option for patients with MF who are intolerant to ruxolitinib.

A year in pharmacology: new drugs approved by the US Food and Drug Administration in 2022

While new drug approvals by the U.S. Food and Drug Administration (FDA) had remained stable or even increased in the first 2 years of the COVID-19 pandemic, the 37 newly approved drugs in 2022 are considerably less than the 53 and 50 new drugs approved in 2020 and 2021, respectively, and less than the rolling 10-year average of 43. As in previous years of this annual review, we assign these new drugs to one of three levels of innovation: first drug against a condition ("first-in-indication"), first drug using a novel molecular mechanism ("first-in-class"), and "next-in-class," i.e., a drug using an already exploited molecular mechanism. We identify two "first-in-indication" (ganaxolon and teplizumab), 20 (54%) "first-in-class," and 17 (46%) "next-in-class" drugs. By treatment area, rare diseases and cancer drugs were once again the most prevalent (partly overlapping) therapeutic areas. Other continuing trends were the use of accelerated regulatory approval pathways and the reliance on biopharmaceuticals (biologics).

Targeted Therapy for MPNs: Going Beyond JAK Inhibitors

PURPOSE OF REVIEW

JAK inhibition is an effective means of controlling symptom burden and improving splenomegaly in patients with myeloproliferative neoplasms (MPNs). However, a majority of patients treated with JAK inhibition will have disease progression with long-term use. In In this review, we focus on the investigation of novel targeted agents beyond JAK inhibitors both in the chronic phase of disease and in the accelerated/blast phase of disease.

RECENT FINDINGS

Relevant targeted therapies in MPNs include BET inhibitors, BCL inhibitors, LSD1 inhibitors, PI3K inhibitors, IDH inhibitors, telomerase inhibitors, and MDM2 inhibitor. Agents within these classes have been investigated either as monotherapy or in combination with a JAK inhibitor. We summarize the prospective data for these agents along with detailing the ongoing phase III trials incorporating these agents. While JAK inhibition has been a mainstay of therapy in MPNs, a majority of patients will have disease of progression. JAK inhibitors also have limited anti-clonal effect and do not impact the rate of progression to the blast phase of disease. The novel therapies detailed in this review not only show promise in ameliorating the symptom burden of MPNs but may be able to alter the natural history of disease.

Roles of STAT3 in the pathogenesis and treatment of glioblastoma

Glioblastoma (GBM) is the most malignant of astrocytomas mainly involving the cerebral hemispheres and the cerebral cortex. It is one of the fatal and refractory solid tumors, with a 5-year survival rate of merely 5% among the adults. IL6/JAK/STAT3 is an important signaling pathway involved in the pathogenesis and progression of GBM. The expression of STAT3 in GBM tissues is substantially higher than that of normal brain cells. The abnormal activation of STAT3 renders the tumor microenvironment of GBM immunosuppression. Besides, blocking the STAT3 pathway can effectively inhibit the growth and metastasis of GBM. On this basis, inhibition of STAT3 may be a new therapeutic approach for GBM, and the combination of STAT3 targeted therapy and conventional therapies may improve the current status of GBM treatment. This review summarized the roles of STAT3 in the pathogenesis of GBM and the feasibility of STAT3 for GBM target therapy.

Modulation of type I interferon signaling by natural products in the treatment of immune-related diseases

Type I interferon (IFN) is considered as a bridge between innate and adaptive immunity. Proper activation or inhibition of type I IFN signaling is essential for host defense against pathogen invasion, tumor cell proliferation, and overactive immune responses. Due to intricate and diverse chemical structures, natural products and their derivatives have become an invaluable source inspiring innovative drug discovery. In addition, some natural products have been applied in clinical practice for infection, cancer, and autoimmunity over thousands of years and their promising curative effects and safety have been well-accepted. However, whether these natural products are primarily targeting type I IFN signaling and specific molecular targets involved are not fully elucidated. In the current review, we thoroughly summarize recent advances in the pharmacology researches of natural products for their type I IFN activity, including both agonism/activation and antagonism/inhibition, and their potential application as therapies. Furthermore, the source and chemical nature of natural products with type I IFN activity are highlighted and their specific molecular targets in the type I IFN pathway and mode of action are classified. In conclusion, natural products possessing type I IFN activity represent promising therapeutic strategies and have a bright prospect in the treatment of infection, cancer, and autoimmune diseases.

Safety and efficacy of jaktinib in the treatment of Janus kinase inhibitor-naïve patients with myelofibrosis: Results of a phase II trial

Myelofibrosis (MF) is associated with several constitutional symptoms. Currently, there are few therapeutic options for MF. Jaktinib, a novel, small-molecule inhibitor of JAK, is currently being studied for its potential to treat MF. This phase 2 trial investigated efficacy and safety of jaktinib in the treatment of MF patients. The primary end point was the proportion of patients with ≥35% reduction in spleen volume (SVR35, proportion of patients with ≥35% reduction in spleen volume) at week 24. The secondary end points included improvement of anemia, rates of symptom response, and safety profile. Between January 8, 2019 and August 29, 2020, 118 patients were recruited and treated with either jaktinib 100 mg BID or 200 mg QD. At week 24, 54.8% (34/62) of patients in the 100 mg BID group and 31.3% (15/48) in the 200 mg QD group achieved SVR35 (p = .0199). Jaktinib treatment increased hemoglobin level to ≥20 g/L in 35.6% (21/59) of patients with hemoglobin ≤100 g/L at baseline. The proportion of patients who achieved a ≥50% improvement in total symptom score at week 24 was 69.6% (39/56) in the BID group and 57.5% (23/40) in the QD group. The most common ≥ grade 3 hematological treatment-emergent adverse events (TEAEs; ≥ 10%) were anemia (100 mg BID: 24.2%, 200 mg QD: 28.8%), thrombocytopenia (16.7%, 11.5%), and neutropenia (3.0%, 11.5%). All non-hematological TEAEs were mild. These results indicate that jaktinib can shrink the spleen, improve anemia, and other clinical symptoms with good tolerability.

Cutting the umbilical cord: Cancer stem cell-targeted therapeutics

Cancer Stem Cells (CSCs) are a notoriously quiescent subpopulation of cells within heterogeneous tumors exhibiting self-renewal, differentiation and drug-resistant capabilities leading to tumor relapse. Heterogeneous cell populations in tumor microenvironment develop an elaborate network of signalling and factors supporting the CSC population within a niche. Identification of specific biomarkers for CSCs facilitates their isolation. CSCs demonstrate abilities that bypass immune surveillance, exhibit resistance to therapy, and induce cancer recurrence while promoting altered metabolism of the bulk tumor, thereby encouraging metastasis. The fight against cancer is prone to relapse without discussing the issue of CSCs, making it imperative for encapsulation of current studies. In this review, we provide extensive knowledge of recent therapeutics developed that target CSCs via multiple signalling cascades, altered metabolism and the tumor microenvironment. Thorough understanding of the functioning of CSCs, their interaction with different cells in the tumor microenvironment as well as current gaps in knowledge are addressed. We present possible strategies to disrupt the cellular and molecular interplay within the tumor microenvironment and make it less conducive for CSCs, which may aid in their eradication with subsequently better treatment outcomes. In conclusion, we discuss a brief yet functional idea of emerging concepts in CSC biology to develop efficient therapeutics acting on cancer recurrence and metastasis.

Pacritinib: First Approval

Pacritinib (VONJO™) is an orally administered, small molecule kinase inhibitor being developed by CTI BioPharma for the treatment of myelofibrosis and graft-versus-host disease. Pacritinib received its first approval in February 2022 in the USA for the treatment of adults with intermediate- or high-risk primary or secondary (post-polycythemia vera or post-essential thrombocythemia) myelofibrosis with a platelet count below 50 × 10⁹/L. The accelerated approval was based on results from the randomized, active-controlled, phase III PERSIST-2 trial, in which spleen volume reduction was demonstrated in pacritinib recipients. This article summarizes the milestones in the development of pacritinib leading to this first approval for myelofibrosis.

The progress of small-molecules and degraders against BCR-ABL for the treatment of CML

Chronic myeloid leukemia (CML) is a malignant disease of the hematopoietic system with crucial pathogenic protein named BCR-ABL, which endangers the life of patients severely. As a milestone of targeted drug, Imatinib has achieved great success in the treatment of CML. Nevertheless, inevitable drug resistance of Imatinib has occurred frequently in clinical due to the several mutations in the BCR-ABL kinase. Subsequently, the second-generation of tyrosine kinase inhibitors (TKIs) against BCR-ABL was developed to address the mutants of Imatinib resistance, except T315I. To date, the third-generation of TKIs targeting T315I has been developed for improving the selectivity and safety. Notably, the first allosteric inhibitor has been in market which could overcome the mutations in ATP binding site effectively. Meanwhile, some advanced technology, such as proteolysis-targeting chimeras (PROTAC) based on different E3 ligand, are highly expected to overcome the drug resistance by selectively degrading the targeted proteins. In this review, we summarized the current research progress of inhibitors and degraders targeting BCR-ABL for the treatment of CML.

JAK2 Inhibitor, Fedratinib, Inhibits P-gp Activity and Co-Treatment Induces Cytotoxicity in Antimitotic Drug-Treated P-gp Overexpressing Resistant KBV20C Cancer Cells

P-glycoprotein (P-gp) overexpression is one of the major mechanisms of multidrug resistance (MDR). Previously, co-treatment with Janus kinase 2 (JAK2) inhibitors sensitized P-gp-overexpressing drug-resistant cancer cells. In this study, we assessed the cytotoxic effects of JAK2 inhibitor, fedratinib, on drug-resistant KBV20C cancer cells. We found that co-treatment with fedratinib at low doses induced cytotoxicity in KBV20C cells treated with vincristine (VIC). However, fedratinib-induced cytotoxicity was little effect on VIC-treated sensitive KB parent cells, suggesting that these effects are specific to resistant cancer cells. Fluorescence-activated cell sorting (FACS), Western blotting, and annexin V analyses were used to further investigate fedratinib’s mechanism of action in VIC-treated KBV20C cells. We found that fedratinib reduced cell viability, increased G2 arrest, and upregulated apoptosis when used as a co-treatment with VIC. G2 phase arrest and apoptosis in VIC–fedratinib-co-treated cells resulted from the upregulation of p21 and the DNA damaging marker pH2AX. Compared with dimethyl sulfoxide (DMSO)-treated cells, fedratinib-treated KBV20C cells showed two-fold higher P-gp-inhibitory activity, indicating that VIC–fedratinib sensitization is dependent on the activity of fedratinib. Similar to VIC, fedratinib co-treatment with other antimitotic drugs (i.e., eribulin, vinorelbine, and vinblastine) showed increased cytotoxicity in KBV20C cells. Furthermore, VIC–fedratinib had similar cytotoxic effects to co-treatment with other JAK2 inhibitors (i.e., VIC–CEP-33779 or VIC–NVP-BSK805) at the same dose; similar cytotoxic mechanisms (i.e., early apoptosis) were observed between treatments, suggesting that co-treatment with JAK2 inhibitors is generally cytotoxic to P-gp-overexpressing resistant cancer cells. Given that fedratinib is FDA-approved, our findings support its application in the co-treatment of P-gp-overexpressing cancer patients showing MDR.

New Markers of Disease Progression in Myelofibrosis

Primary myelofibrosis (PMF) is a myeloproliferative neoplasm due to the clonal proliferation of a hematopoietic stem cell. The vast majority of patients harbor a somatic gain of function mutation either of JAK2 or MPL or CALR genes in their hematopoietic cells, resulting in the activation of the JAK/STAT pathway. Patients display variable clinical and laboratoristic features, including anemia, thrombocytopenia, splenomegaly, thrombotic complications, systemic symptoms, and curtailed survival due to infections, thrombo-hemorrhagic events, or progression to leukemic transformation. New drugs have been developed in the last decade for the treatment of PMF-associated symptoms; however, the only curative option is currently represented by allogeneic hematopoietic cell transplantation, which can only be offered to a small percentage of patients. Disease prognosis is based at diagnosis on the classical International Prognostic Scoring System (IPSS) and Dynamic-IPSS (during disease course), which comprehend clinical parameters; recently, new prognostic scoring systems, including genetic and molecular parameters, have been proposed as meaningful tools for a better patient stratification. Moreover, new biological markers predicting clinical evolution and patient survival have been associated with the disease. This review summarizes basic concepts of PMF pathogenesis, clinics, and therapy, focusing on classical prognostic scoring systems and new biological markers of the disease.

JAK inhibitors: a potential treatment for JDM in the context of the role of interferon-driven pathology

Juvenile Idiopathic Inflammatory Myopathies (IIM) are a group of rare diseases that are heterogeneous in terms of pathology that can include proximal muscle weakness, associated skin changes and systemic involvement. Despite options for treatment, many patients continue to suffer resistant disease and lasting side-effects. Advances in the understanding of the immunopathology and genetics underlying IIM may specify new therapeutic targets, particularly where conventional treatment has not achieved a clinical response. An upregulated type I interferon signature is strongly associated with disease and could be a prime target for developing more specific therapeutics. There are multiple components of the IFN pathway that could be targeted for blockade therapy.Downstream of the cytokine receptor complexes are the Janus kinase-signal transducers and activators of transcription (JAK-STAT) pathway, which consists of JAK1-3, TYK2, and STAT1-6. Therapeutic inhibitors have been developed to target components of this pathway. Promising results have been observed in case studies reporting the use of the JAK inhibitors, Baricitinib, Tofacitinib and Ruxolitinib in the treatment of refractory Juvenile Dermatomyositis (JDM). There is still the question of safety and efficacy for the use of JAK inhibitors in JDM that need to be addressed by clinical trials. Here we review the future for the use of JAK inhibitors as a treatment for JDM.

The Ups and Downs of STAT Inhibition in Acute Myeloid Leukemia

Aberrant Janus kinase-signal transducer and activator of transcription (JAK-STAT) signaling is implicated in the pathogenesis of acute myeloid leukemia (AML), a highly heterogeneous hematopoietic malignancy. The management of AML is complex and despite impressive efforts into better understanding its underlying molecular mechanisms, survival rates in the elderly have not shown a substantial improvement over the past decades. This is particularly due to the heterogeneity of AML and the need for personalized approaches. Due to the crucial role of the deregulated JAK-STAT signaling in AML, selective targeting of the JAK-STAT pathway, particularly constitutively activated STAT3 and STAT5 and their associated upstream JAKs, is of great interest. This strategy has shown promising results in vitro and in vivo with several compounds having reached clinical trials. Here, we summarize recent FDA approvals and current potential clinically relevant inhibitors for AML patients targeting JAK and STAT proteins. This review underlines the need for detailed cytogenetic analysis and additional assessment of JAK-STAT pathway activation. It highlights the ongoing development of new JAK-STAT inhibitors with better disease specificity, which opens up new avenues for improved disease management.

Untwining Anti-Tumor and Immunosuppressive Effects of JAK Inhibitors-A Strategy for Hematological Malignancies?

Simple Summary

The Janus kinase-signal transducer and activator of transcription (JAK-STAT) pathway is aberrantly activated in many malignancies. Inhibition of this pathway via JAK inhibitors (JAKinibs) is therefore an attractive therapeutic strategy underlined by Ruxolitinib (JAK1/2 inhibitor) being approved for the treatment of myeloproliferative neoplasms. As a consequence of the crucial role of the JAK-STAT pathway in the regulation of immune responses, inhibition of JAKs suppresses the immune system. This review article provides a thorough overview of the current knowledge on JAKinibs’ effects on immune cells in the context of hematological malignancies. We also discuss the potential use of JAKinibs for the treatment of diseases in which lymphocytes are the source of the malignancy.

Abstract

The Janus kinase-signal transducer and activator of transcription (JAK-STAT) pathway propagates signals from a variety of cytokines, contributing to cellular responses in health and disease. Gain of function mutations in JAKs or STATs are associated with malignancies, with JAK2^V617F being the main driver mutation in myeloproliferative neoplasms (MPN). Therefore, inhibition of this pathway is an attractive therapeutic strategy for different types of cancer. Numerous JAK inhibitors (JAKinibs) have entered clinical trials, including the JAK1/2 inhibitor Ruxolitinib approved for the treatment of MPN. Importantly, loss of function mutations in JAK-STAT members are a cause of immune suppression or deficiencies. MPN patients undergoing Ruxolitinib treatment are more susceptible to infections and secondary malignancies. This highlights the suppressive effects of JAKinibs on immune responses, which renders them successful in the treatment of autoimmune diseases but potentially detrimental for cancer patients. Here, we review the current knowledge on the effects of JAKinibs on immune cells in the context of hematological malignancies. Furthermore, we discuss the potential use of JAKinibs for the treatment of diseases in which lymphocytes are the source of malignancies. In summary, this review underlines the necessity of a robust immune profiling to provide the best benefit for JAKinib-treated patients.

Radiotherapy for symptom palliation of splenomegaly in patients with haematological malignancies

Splenomegaly severely compromises the quality of life of those affected. The aim of the present study was to describe the clinical characteristics of patients with haematological disorders who receive radiotherapy for splenomegaly, particularly focusing on the changes in spleen volume. The present study conducted a retrospective analysis of consecutive patients with haematological disorders who underwent splenic radiotherapy with palliative intent at the Department of Radiology of the University of Tokyo Hospital between June 2008 and June 2019. Pre- and post-radiotherapy spleen volumes were measured from computed tomography images. A total of 8 patients (5 men and 3 women) with a median age of 59 years (range, 46-76 years) were included. The median total prescription and fractional doses were 4.5 Gy (range, 1.5-10 Gy) and 0.78 Gy (range, 0.5-2.0 Gy), respectively. A total of 5 patients (62.5%) experienced a reduction in spleen volume. The mean ± SD spleen sizes pre- and post-radiotherapy were 1,887±1,011 and 1,368±577 ml, respectively. The mean variation rate in spleen volume was -19.1±24.7%, and the case with the most notable improvement in the present study exhibited a -52.4% change. Of the 5 patients who experienced pain prior to radiotherapy, 3 achieved pain relief, 1 did not experience any change and 1 patient was not assessed post-radiotherapy. Therefore, the findings of the present study revealed that palliative radiotherapy for splenomegaly may achieve symptom palliation and radiological volumetric effects in patients with haematological disorders.

Inflammatory Microenvironment and Specific T Cells in Myeloproliferative Neoplasms: Immunopathogenesis and Novel Immunotherapies

The Philadelphia-negative myeloproliferative neoplasms (MPNs) are malignancies of the hematopoietic stem cell (HSC) arising as a consequence of clonal proliferation driven by somatically acquired driver mutations in discrete genes (JAK2, CALR, MPL). In recent years, along with the advances in molecular characterization, the role of immune dysregulation has been achieving increasing relevance in the pathogenesis and evolution of MPNs. In particular, a growing number of studies have shown that MPNs are often associated with detrimental cytokine milieu, expansion of the monocyte/macrophage compartment and myeloid-derived suppressor cells, as well as altered functions of T cells, dendritic cells and NK cells. Moreover, akin to solid tumors and other hematological malignancies, MPNs are able to evade T cell immune surveillance by engaging the PD-1/PD-L1 axis, whose pharmacological blockade with checkpoint inhibitors can successfully restore effective antitumor responses. A further interesting cue is provided by the recent discovery of the high immunogenic potential of JAK2V617F and CALR exon 9 mutations, that could be harnessed as intriguing targets for innovative adoptive immunotherapies. This review focuses on the recent insights in the immunological dysfunctions contributing to the pathogenesis of MPNs and outlines the potential impact of related immunotherapeutic approaches.

Inflammatory Microenvironment and Specific T Cells in Myeloproliferative Neoplasms: Immunopathogenesis and Novel Immunotherapies

The Philadelphia-negative myeloproliferative neoplasms (MPNs) are malignancies of the hematopoietic stem cell (HSC) arising as a consequence of clonal proliferation driven by somatically acquired driver mutations in discrete genes (JAK2, CALR, MPL). In recent years, along with the advances in molecular characterization, the role of immune dysregulation has been achieving increasing relevance in the pathogenesis and evolution of MPNs. In particular, a growing number of studies have shown that MPNs are often associated with detrimental cytokine milieu, expansion of the monocyte/macrophage compartment and myeloid-derived suppressor cells, as well as altered functions of T cells, dendritic cells and NK cells. Moreover, akin to solid tumors and other hematological malignancies, MPNs are able to evade T cell immune surveillance by engaging the PD-1/PD-L1 axis, whose pharmacological blockade with checkpoint inhibitors can successfully restore effective antitumor responses. A further interesting cue is provided by the recent discovery of the high immunogenic potential of JAK2V617F and CALR exon 9 mutations, that could be harnessed as intriguing targets for innovative adoptive immunotherapies. This review focuses on the recent insights in the immunological dysfunctions contributing to the pathogenesis of MPNs and outlines the potential impact of related immunotherapeutic approaches.