The Development and Use of Janus Kinase 2 Inhibitors for the Treatment of Myeloproliferative Neoplasms

Macrocyclization strategy for improving candidate profiles in medicinal chemistry

Macrocycles are defined as cyclic compounds with 12 or more members. In medicinal chemistry, they are categorized based on their core chemistry into cyclic peptides and macrocycles. Macrocycles are advantageous because of their structural diversity and ability to achieve high affinity and selectivity towards challenging targets that are often not addressable by conventional small molecules. The potential of macrocyclization to optimize drug-like properties while maintaining adequate bioavailability and permeability has been emphasized as a key innovation in medicinal chemistry. This review provides a detailed case study of the application of macrocyclization over the past 5 years, starting from the initial analysis of acyclic active compounds to optimization of the resulting macrocycles for improved efficacy and drug-like properties. Additionally, it illustrates the strategic value of macrocyclization in contemporary drug discovery efforts.

Macrocyclization of linear molecules by deep learning to facilitate macrocyclic drug candidates discovery

Interest in macrocycles as potential therapeutic agents has increased rapidly. Macrocyclization of bioactive acyclic molecules provides a potential avenue to yield novel chemical scaffolds, which can contribute to the improvement of the biological activity and physicochemical properties of these molecules. In this study, we propose a computational macrocyclization method based on Transformer architecture (which we name Macformer). Leveraging deep learning, Macformer explores the vast chemical space of macrocyclic analogues of a given acyclic molecule by adding diverse linkers compatible with the acyclic molecule. Macformer can efficiently learn the implicit relationships between acyclic and macrocyclic structures represented as SMILES strings and generate plenty of macrocycles with chemical diversity and structural novelty. In data augmentation scenarios using both internal ChEMBL and external ZINC test datasets, Macformer display excellent performance and generalisability. We showcase the utility of Macformer when combined with molecular docking simulations and wet lab based experimental validation, by applying it to the prospective design of macrocyclic JAK2 inhibitors.

Mutations, inflammation and phenotype of myeloproliferative neoplasms

Knowledge on the myeloproliferative neoplasms (MPNs) - polycythemia vera (PV), essential thrombocythemia (ET), primary myelofibrosis (PMF) - has accumulated since the discovery of the JAK/STAT-activating mutations associated with MPNs: JAK2V617F, observed in PV, ET and PMF; and the MPL and CALR mutations, found in ET and PMF. The intriguing lack of disease specificity of these mutations, and of the chronic inflammation associated with MPNs, triggered a quest for finding what precisely determines that MPN patients develop a PV, ET or PMF phenoptype. The mechanisms of action of MPN-driving mutations, and concomitant mutations (ASXL1, DNMT3A, TET2, others), have been extensively studied, as well as the role played by these mutations in inflammation, and several pathogenic models have been proposed. In parallel, different types of drugs have been tested in MPNs (JAK inhibitors, interferons, hydroxyurea, anagrelide, azacytidine, combinations of those), some acting on both JAK2 and inflammation. Yet MPNs remain incurable diseases. This review aims to present current, detailed knowledge on the pathogenic mechanisms specifically associated with PV, ET or PMF that may pave the way for the development of novel, curative therapies.

Anti-neoplastic pharmacophore benzophenone-1 coumarin (BP-1C) targets JAK2 to induce apoptosis in lung cancer

Reigning of the abnormal gene activation associated with survival signalling in lung cancer leads to the anomalous growth and therapeutic failure. Targeting specific cell survival signalling like JAK2/STAT3 nexus has become a major focus of investigation to establish a target specific treatment. The 2-bromobenzoyl-4-methylphenoxy-acetyl hydra acetyl Coumarin (BP-1C), is new anti-neoplastic agent with apoptosis inducing capacity. The current study was aimed to develop antitumor phramacophore, BP-1C as JAK2 specific inhibitor against lung neoplastic progression. The study validates and identifies the molecular targets of BP-1C induced cell death. Cell based screening against multiple cancer cell lines identified, lung adenocarcinoma as its specific target through promotion of apoptosis. The BP-1C is able to induce, specific hall marks of apoptosis and there by conferring anti-neoplastic activity. Validation of its molecular mechanism, identified, BP-1C specifically targets JAK2^Tyr1007/1008 phosphorylation, and inhibits its downstream STAT3^Tyr705 signalling pathway to induce cell death. As a consequence, modulation in Akt/Src survival signal and altered expression of interwoven apoptotic genes were evident. The results were reproducible in an in-vivo LLC tumor model and in-ovo xenograft studies. The computational approaches viz, drug finger printing confers, BP-1C as novel class JAK2 inhibitor and molecular simulations studies assures its efficiency in binding with JAK2. Overall, BP-1C is a novel JAK2 inhibitor with experimental evidence and could be effectively developed into a promising drug for lung cancer treatment.

Dual targeting of JAK2 and ERK interferes with the myeloproliferative neoplasm clone and enhances therapeutic efficacy

Myeloproliferative neoplasms (MPN) show dysregulated JAK2 signaling. JAK2 inhibitors provide clinical benefits, but compensatory activation of MAPK pathway signaling impedes efficacy. We hypothesized that dual targeting of JAK2 and ERK1/2 could enhance clone control and therapeutic efficacy. We employed genetic and pharmacologic targeting of ERK1/2 in Jak2V617F MPN mice, cells and patient clinical isolates. Competitive transplantations of Jak2V617F vs. wild-type bone marrow (BM) showed that ERK1/2 deficiency in hematopoiesis mitigated MPN features and reduced the Jak2V617F clone in blood and hematopoietic progenitor compartments. ERK1/2 ablation combined with JAK2 inhibition suppressed MAPK transcriptional programs, normalized cytoses and promoted clone control suggesting dual JAK2/ERK1/2 targeting as enhanced corrective approach. Combined pharmacologic JAK2/ERK1/2 inhibition with ruxolitinib and ERK inhibitors reduced proliferation of Jak2V617F cells and corrected erythrocytosis and splenomegaly of Jak2V617F MPN mice. Longer-term treatment was able to induce clone reductions. BM fibrosis was significantly decreased in MPLW515L-driven MPN to an extent not seen with JAK2 inhibitor monotherapy. Colony formation from JAK2V617F patients' CD34⁺ blood and BM was dose-dependently inhibited by combined JAK2/ERK1/2 inhibition in PV, ET, and MF subsets. Overall, we observed that dual targeting of JAK2 and ERK1/2 was able to enhance therapeutic efficacy suggesting a novel treatment approach for MPN.

[The prognostic value of ASXL1 mutation in primary myelofibrosis. Literature review and clinical case description]

Primary myelofibrosis is a myeloproliferative neoplasm that occurs de novo, characterized by clonal proliferation of stem cells, abnormal expression of cytokines, bone marrow fibrosis, hepatosplenomegaly as a result of extramedullary hematopoiesis, symptoms of tumor intoxication, cachexemia, peripheral blood leukoerythroblastosis, leukemic progression and low survival. Primary myelofibrosis is a chronic incurable disease. The aims of therapy: preventing progression, increasing overall survival, improving quality of life. The choice of therapeutic tactics is limited. Allogenic hematopoietic stem cell transplantation is the only method that gives a chance for a cure. The role of mutations in a number of genes in the early identification of candidates for allogeneic hematopoietic stem cell transplantation is being actively studied. The article describes the clinical case of the detection ofASXL1gene mutations in a patient with prefibrous primary myelofibrosis. The diagnosis was established on the basis of WHO criteria 2016. The examination revealed a mutation ofASXL1. Interferon alfa therapy is carried out, against the background of which clinico-hematological remission has been achieved. Despite the identified mutation, the patient is not a candidate for allogeneic hematopoietic stem cell transplantation. Given the unfavorable prognostic value of theASXL1mutation, the patient is subject to active dynamic observation and aggressive therapeutic tactics when signs of disease progression appear.

Anti-Glucosylsphingosine Autoimmunity, JAK2V617F-Dependent Interleukin-1β and JAK2V617F-Independent Cytokines in Myeloproliferative Neoplasms

Simple Summary

Inflammation plays a major role in myeloproliferative neoplasms (MPNs) as regulator of malignant cell growth and mediator of clinical symptoms. Yet chronic inflammation may also be an early event that facilitates the development of MPNs. Here we analysed 42 inflammatory cytokines and report that in patients as well as in UT-7 cell lines, interleukin-1β and interferon-induced protein 10 (IP-10) were the main inflammatory molecules found to be induced by JAK2V617F, the most frequent driving mutation in MPNs. All other inflammatory cytokines were not linked to JAK2V617F, which implies that inflammation likely precedes MPN development at least in subsets of MPN patients. Consistently, a possible cause of early, chronic inflammation may be auto-immunity against glucolipids: we report that 20% of MPN patients presented with anti-glucosylsphingoside auto-antibodies. Since existing treatments can reduce glucosylsphingoside, this lysosphingolipid could become a new therapeutic target for subsets of MPN patients, in addition to JAK2V617F and inflammation.

Abstract

Inflammatory cytokines play a major role in myeloproliferative neoplasms (MPNs) as regulators of the MPN clone and as mediators of clinical symptoms and complications. Firstly, we investigated the effect of JAK2V617F on 42 molecules linked to inflammation. For JAK2V617F-mutated patients, the JAK2V617F allele burden (%JAK2V617F) correlated with the levels of IL-1β, IL-1Rα, IP-10 and leptin in polycythemia vera (PV), and with IL-33 in ET; for all other molecules, no correlation was found. Cytokine production was also studied in the human megakaryocytic cell line UT-7. Wild-type UT-7 cells secreted 27/42 cytokines measured. UT-7 clones expressing 50% or 75% JAK2V617F were generated, in which the production of IL-1β, IP-10 and RANTES was increased; other cytokines were not affected. Secondly, we searched for causes of chronic inflammation in MPNs other than driver mutations. Since antigen-driven selection is increasingly implicated in the pathogenesis of blood malignancies, we investigated whether proinflammatory glucosylsphingosine (GlcSph) may play a role in MPNs. We report that 20% (15/75) of MPN patients presented with anti-GlcSph IgGs, distinguished by elevated levels of 11 cytokines. In summary, only IL-1β and IP-10 were linked to JAK2V617F both in patients and in UT-7 cells; other inflammation-linked cytokines in excess in MPNs were not. For subsets of MPN patients, a possible cause of inflammation may be auto-immunity against glucolipids.

A journey through infectious risk associated with ruxolitinib

Ruxolitinib has proved to be effective for the treatment of patients with myelofibrosis (either primary or secondary) and polycythaemia vera, and its approval led to a significant change in the current treatment algorithm. Despite its efficacy and beyond its well described haematological toxicity, a peculiar immunosuppressive effect emerged as our clinical experience grew, both within and outside of a clinical trial setting. Definite and negative interactions with multiple pathways of the immune system of patients have been reported so far, involving both adaptive and innate immune responses. These pathophysiological mechanisms may contribute to the increased risk of reactivation of silent infections (e.g., tuberculosis, hepatitis B virus and varicella zoster virus) that have been associated with the drug. Even though such infectious events may be fatal or may lead to significant impairment of organ function, compromising the eligibility of patients for an allotransplant procedure, there are no dedicated guidelines that may help us in assessing and managing the risk of developing serious infections. On this basis, our aim for the present work was to review the current knowledge on the pathophysiological mechanisms through which ruxolitinib may exert its immunosuppressive effect, and to illustrate our personal approach to the management of three peculiar clinical scenarios, for which a risk-based algorithm is suggested.

Emerging translational science discoveries, clonal approaches, and treatment trends in chronic myeloproliferative neoplasms

The 60th American Society of Hematology (ASH) held in San Diego in December 2018 was followed by the 13th Post-ASH chronic myeloproliferative neoplasms (MPNs) workshop on December 4 and 5, 2018. This closed annual workshop, first introduced in 2006 by Goldman and Mughal, was organized in collaboration with Alpine Oncology Foundation and allowed experts in preclinical and clinical research in the chronic MPNs to discuss the current scenario, including relevant presentations at ASH, and address pivotal open questions that impact translational research and clinical management. This review is based on the presentations and deliberations at this workshop, and rather than provide a resume of the proceedings, we have selected some of the important translational science and treatment issues that require clarity. We discuss the experimental and observational evidence to support the intimate interaction between aging, inflammation, and clonal evolution of MPNs, the clinical impact of the unfolding mutational landscape on the emerging targets and treatment of MPNs, new methods to detect clonal heterogeneity, the challenges in managing childhood and adolescent MPN, and reflect on the treatment of systemic mastocytosis (SM) following the licensing of midostaurin.

Targeting compensatory MEK/ERK activation increases JAK inhibitor efficacy in myeloproliferative neoplasms

Constitutive JAK2 signaling is central to myeloproliferative neoplasm (MPN) pathogenesis and results in activation of STAT, PI3K/AKT, and MEK/ERK signaling. However, the therapeutic efficacy of current JAK2 inhibitors is limited. We investigated the role of MEK/ERK signaling in MPN cell survival in the setting of JAK inhibition. Type I and II JAK2 inhibition suppressed MEK/ERK activation in MPN cell lines in vitro, but not in Jak2V617F and MPLW515L mouse models in vivo. JAK2 inhibition ex vivo inhibited MEK/ERK signaling, suggesting that cell-extrinsic factors maintain ERK activation in vivo. We identified PDGFRα as an activated kinase that remains activated upon JAK2 inhibition in vivo, and PDGF-AA/PDGF-BB production persisted in the setting of JAK inhibition. PDGF-BB maintained ERK activation in the presence of ruxolitinib, consistent with its function as a ligand-induced bypass for ERK activation. Combined JAK/MEK inhibition suppressed MEK/ERK activation in Jak2V617F and MPLW515L mice with increased efficacy and reversal of fibrosis to an extent not seen with JAK inhibitors. This demonstrates that compensatory ERK activation limits the efficacy of JAK2 inhibition and dual JAK/MEK inhibition provides an opportunity for improved therapeutic efficacy in MPNs and in other malignancies driven by aberrant JAK-STAT signaling.

JAK2 (and other genes) be nimble with MPN diagnosis, prognosis, and therapy

Now that the spectrum of somatic mutations that initiate, propagate, and drive the progression of myeloproliferative neoplasms (MPNs) has largely been defined, recent efforts have focused on integrating this information into clinical decision making. In this regard, the greatest progress has been made in myelofibrosis, in which high-molecular-risk mutations have been identified and incorporated into prognostic models to help guide treatment decisions. In this chapter, we focus on advances in 4 main areas: (1) What are the MPN phenotypic driver mutations? (2) What constitutes high molecular risk in MPN (focusing on ASXL1)? (3) How do we risk-stratify patients with MPN? And (4) What is the significance of molecular genetics for MPN treatment? Although substantial progress has been made, we still have an incomplete understanding of the molecular basis for phenotypic diversity in MPN, and few rationally designed therapeutic approaches to target high-risk mutations are available. Ongoing research efforts in these areas are critical to understanding the biological consequences of genetic heterogeneity in MPN and to improving outcomes for patients.

Predictive models for splenic response to JAK-inhibitor therapy in patients with myelofibrosis

JAK inhibitors for myelofibrosis (MF) reduce spleen size, control constitutional symptoms, and may improve survival. We studied the clinical characteristics of 548 MF patients treated with JAK inhibitors from 2008 to 2016 to better understand predictors of splenic response. Response was defined as a 50% decrease in spleen size at early (3-4 months on therapy) and late (5-12 months) timepoints after therapy initiation. Early response positively correlated with higher doses of JAK inhibitor, baseline spleen size 5-10 cm, and hemoglobin. Early response negatively correlated with baseline spleen size >20 cm and high WBC. The strongest predictor of late response was whether a patient had a response at the earlier timepoint (OR 8.88). Our response models suggest that clinical factors can be used to predict which patients are more likely to respond to JAK inhibitors, and those who do not achieve an early response, i.e. within 3-4 months, should consider alternative treatments.

Translational and clinical advances in JAK-STAT biology: The present and future of jakinibs

In this era, it is axiomatic that cytokines have critical roles in cellular development and differentiation, immune homeostasis, and host defense. Equally, dysregulation of cytokines is known to contribute to diverse inflammatory and immune-mediated disorders. In fact, the past 20 years have witnessed the rapid translation of basic discoveries in cytokine biology to multiple successful biological agents (mAbs and recombinant fusion proteins) that target cytokines. These targeted therapies have not only fundamentally changed the face of multiple immune-mediated diseases but have also unequivocally established the role of specific cytokines in human disease; cytokine biologists have many times over provided remarkable basic advances with direct clinical benefit. Numerous cytokines rely on the JAK-STAT pathway for signaling, and new, safe, and effective small molecule inhibitors have been developed for a range of disorders. In this review, we will briefly summarize basic discoveries in cytokine signaling and briefly comment on some major unresolved issues. We will review clinical data pertaining to the first generation of JAK inhibitors and their clinical indications, discuss additional opportunities for targeting this pathway, and lay out some of the challenges that lie ahead.

NPV-BSK805, an Antineoplastic Jak2 Inhibitor Effective in Myeloproliferative Disorders, Causes Adiposity in Mice by Interfering With the Action of Leptin

The pathophysiology of body weight gain that is observed in patients suffering from myeloproliferative neoplasms treated with inhibitors of the janus kinase (Jak) 1 and 2 pathway remains unknown. Here we hypothesized that this class of drugs interferes with the metabolic actions of leptin, as this hormone requires functional Jak2 signaling. To test this, C57BL/6J chow-fed mice received either chronic intraperitoneal (ip) or repeated intracerebroventricular (icv) administration of the selective Jak2 inhibitor NVP-BSK805, which was proven efficacious in treating polycythemia in rodents. Changes in food intake, body weight and body composition were recorded. Icv NVP-BSK805 was combined with ip leptin to evaluate ability to interfere with the action of this hormone on food intake and on induction of hypothalamic phosphorylation of signal transducer and activator of transcription 3 (STAT3). We found that chronic peripheral administration of NVP-BSK805 did not alter food intake, but increased fat mass and feed efficiency. The increase in fat mass was more pronounced during repeated icv administration of the compound, suggesting that metabolic effects were related to molecular interference in brain structures regulating energy balance. Accordingly, acute icv administration of NVP-BSK805 prevented the ability of leptin to decrease food intake and body weight by impeding STAT3 phosphorylation within the hypothalamus. Consequently, acute icv administration of NVP-BSK805 at higher dose induced hyperphagia and body weight gain. Our results provide evidence for a specific anabolic effect exerted by antineoplastic drugs targeting the Jak2 pathway, which is due to interference with the actions of leptin. Consequently, assessment of metabolic variables related to increased fat mass gain should be performed in patients treated with Jak2 inhibitors.

Prevalence of the Janus kinase 2 V617F mutation in Philadelphia-negative myeloproliferative neoplasms in a Portuguese population

Myeloproliferative neoplasms (MPNs) result from the malignant transformation of a hematopoietic stem-cell (HSC), leading to abnormal amplification and proliferation of myeloid lineages. Identification of the Janus kinase 2 (JAK2) V617F mutation developed the knowledge of Philadelphia-negative (PN)-MPNs, contributing to and influencing the definition of the phenotype and prognostic impact. Considering the lack of Portuguese epidemiological data, the present study intends to characterize the prevalence of the JAK2 mutation in a PN-MPN versus a control Portuguese population. Caucasian Portuguese PN-MPN patients (n=133) and 281 matched control subjects were investigated. No significant differences were identified between the case and control groups concerning age distribution or smoking habits. Pathology distribution was as follows: 60.2% with essential thrombocythemia (ET), 29.3% with polycythemia vera (PV) and 10.5% with primary myelofibrosis (PMF). A total of 75.0% of patients were positive for the presence of the JAK2 V617F mutation. In addition, the prevalence of PV was 87.2%, ET was 73.4% and PMF was 50.0%. The JAK2 V617F mutation is observed in various MPN phenotypes, and has an increased incidence in ET patients and a decreased incidence in PV patients. These data may contribute to improving the knowledge of the pathophysiology of these disorders, and to a more rational and efficient selection of therapeutic strategies to be adopted, notably because most of the patients are JAK2 V617F negative.