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

Molecular biomarkers of leukemia: convergence-based drug resistance mechanisms in chronic myeloid leukemia and myeloproliferative neoplasms

Leukemia represents a diverse group of hematopoietic neoplasms that can be classified into different subtypes based on the molecular aberration in the affected cell population. Identification of these molecular classification is required to identify specific targeted therapeutic approaches for each leukemic subtype. In general, targeted therapy approaches achieve good responses in some leukemia subgroups, however, resistance against these targeted therapies is common. In this review, we summarize molecular drug resistance biomarkers in targeted therapies in BCR::ABL1-driven chronic myeloid leukemia (CML) and JAK2-driven myeloproliferative neoplasms (MPNs). While acquisition of secondary mutations in the BCR::ABL1 kinase domain is the a common mechanism associated with TKI resistance in CML, in JAK2-driven MPNs secondary mutations in JAK2 are rare. Due to high prevalence and lack of specific therapy approaches in MPNs compared to CML, identification of crucial pathways leading to inhibitor persistence in MPN model is utterly important. In this review, we focus on different alternative signaling pathways activated in both, BCR::ABL1-mediated CML and JAK2-mediated MPNs, by combining data from in vitro and in vivo-studies that could be used as potential biomarkers of drug resistance. In a nutshell, some common similarities, especially activation of PDGFR, Ras, PI3K/Akt signaling pathways, have been demonstrated in both leukemias. In addition, induction of the nucleoprotein YBX1 was shown to be involved in TKI-resistant JAK2-mediated MPN, as well as TKI-resistant CML highlighting deubiquitinating enzymes as potential biomarkers of TKI resistance. Taken together, whole exome sequencing of cell-based or patients-derived samples are highly beneficial to define specific resistance markers. Additionally, this might be helpful for the development of novel diagnostic tools, e.g., liquid biopsy, and novel therapeutic agents, which could be used to overcome TKI resistance in molecularly distinct leukemia subtypes.

Type II mode of JAK2 inhibition and destabilization are potential therapeutic approaches against the ruxolitinib resistance driven myeloproliferative neoplasms

Background

Ruxolitinib has been approved by the US FDA for the treatment of myeloproliferative neoplasms such as polycythemia vera and primary myelofibrosis. Ruxolitinib will remain a main stay in the treatment of MPN patients due to its effective therapeutic benefits. However, there have been instances of ruxolitinib resistance in MPN patients. As JAK2 is a direct target of ruxolitinib, we generated ruxolitinib-resistant clones to find out the mechanism of resistance.

Methods

Cell-based screening strategy was used to detect the ruxolitinib-resistant mutations in JAK2. The Sanger sequencing method was used to detect the point mutations in JAK2. Mutations were re-introduced using the site-directed mutagenesis method and stably expressed in Ba/F3 cells. Drug sensitivities against the JAK2 inhibitors were measured using an MTS-based assay. JAK2 and STAT5 activation levels and total proteins were measured using immunoblotting. Computational docking studies were performed using the Glide module of Schrodinger Maestro software.

Results

In this study, we have recovered seven residues in the kinase domain of JAK2 that affect ruxolitinib sensitivity. All these mutations confer cross-resistance across the panel of JAK2 kinase inhibitors except JAK2-L983F. JAK2-L983F reduces the sensitivity towards ruxolitinib. However, it is sensitive towards fedratinib indicating that our screen identifies the drug-specific resistance profiles. All the ruxolitinib-resistant JAK2 variants displayed sensitivity towards type II JAK2 inhibitor CHZ-868. In this study, we also found that JAK1-L1010F (homologous JAK2-L983F) is highly resistant towards ruxolitinib suggesting the possibility of JAK1 escape mutations in JAK2-driven MPNs and JAK1 mutated ALL. Finally, our study also shows that HSP90 inhibitors are potent against ruxolitinib-resistant variants through the JAK2 degradation and provides the rationale for clinical evaluation of potent HSP90 inhibitors in genetic resistance driven by JAK2 inhibitors.

Conclusion

Our study identifies JAK1 and JAK2 resistance variants against the type I JAK2 inhibitors ruxolitinib, fedratinib, and lestaurtinib. The sensitivity of these resistant variants towards the type II JAK2 inhibitor CHZ-868 indicates that this mode of type II JAK2 inhibition is a potential therapeutic approach against ruxolitinib refractory leukemia. This also proposes the development of potent and specific type II JAK2 inhibitors using ruxolitinib-resistance variants as a prototype.

Patchouli Alcohol Protects the Heart against Diabetes-Related Cardiomyopathy through the JAK2/STAT3 Signaling Pathway

Diabetic cardiomyopathy (DCM) represents a common pathological state brought about by diabetes mellitus (DM). Patchouli alcohol (PatA) is known for its diverse advantageous effects, notably its anti-inflammatory properties and protective role against metabolic disorders. Despite this, the influence of PatA on DCM remains relatively unexplored. To explore the effect of PatA on diabetes-induced cardiac injury and dysfunction in mice, streptozotocin (STZ) was used to mimic type 1 diabetes in mice. Serological markers and echocardiography show that PatA treatment protects the heart against cardiomyopathy by controlling myocardial fibrosis but not by reducing hyperglycemia in diabetic mice. Discovery Studio 2017 software was used to perform reverse target screening of PatA, and we found that JAK2 may be a potential target of PatA. RNA-seq analysis of heart tissues revealed that PatA activity in the myocardium was primarily associated with the inflammatory fibrosis through the Janus tyrosine kinase 2 (JAK2)/signal transducer and activator of the transcription 3 (STAT3) pathway. In vitro, we also found that PatA alleviates high glucose (HG) + palmitic acid (PA)-induced fibrotic and inflammatory responses via inhibiting the JAK2/STAT3 signaling pathway in H9C2 cells. Our findings illustrate that PatA mitigates the effects of HG + PA- or STZ-induced cardiomyopathy by acting on the JAK2/STAT3 signaling pathway. These insights indicate that PatA could potentially serve as a therapeutic agent for DCM treatment.

Advances in pharmacotherapy for myelofibrosis: what is the current state of play?

INTRODUCTION

The introduction of the first JAK inhibitor (JAKi) ruxolitinib 10 years ago represented a pivotal advancement in myelofibrosis (MF) treatment, mostly in terms of spleen and symptoms response. Nowadays three more JAKi, fedratinib, pacritinib, and momelotinib, are available for both ruxolitinib-resistant and naïve patients. Moreover, many drugs are currently being investigated, both alone and in combination with JAKi.

AREAS COVERED

In this review we discuss the long-term data of ruxolitinib and more recent evidence coming from clinical trials of fedratinib, pacritinib, and momelotinib, used as first- or second-line MF therapy. More, focus is set on data from non-JAKi drugs, such as the quite extensively studied BET-inhibitors (pelabresib) and BCL-inhibitors (navitoclax), novel target therapies, and drugs aimed to improve anemia, still representing a major determinant of reduced survival in MF.

EXPERT OPINION

It's now evident that JAKi monotherapy, though clinically effective, is rarely able to change MF natural history; novel drugs are promising but long-term data are inevitably lacking. We feel that soon MF treatment will require clinicians to select the most appropriate JAKi inhibitor, based on patient characteristics, associating either front-line or in case of early suboptimal response, non-JAKi drugs with the aim to pursue disease modification.

A phase I trial of pevonedistat in combination with ruxolitinib for the treatment of myelofibrosis

Janus kinase 2 (JAK2) inhibitors such as ruxolitinib have become standard-of-care therapy for patients with myeloproliferative neoplasms (MPNs); however, activation of alternate oncogenic pathways including nuclear factor kappa-light-chain-enhancer of activated B cells (NFκB) has limited durable response as single-agent therapy. With the rationale of targeting both pathways, we conducted a phase I dose escalation trial of pevonedistat in combination with ruxolitinib for the treatment of patients with myelofibrosis (NCT03386214). The primary objective was to assess the safety and tolerability of combination therapy with additional objectives of treatment efficacy and alterations of biomarkers. There were no dose-limiting toxicities observed with most adverse events being limited to grades 1/2. In secondary measures, anemia response was observed in two patients. Pro-inflammatory cytokines and iron parameters were longitudinally assessed, which revealed suppression of interleukin-6 and interferon-gamma in a dose-dependent manner across a subset of patients. These results suggest that combination therapy targeting both JAK2 and NFκB may hold clinical merit for MPN patients.

Changes in bone marrow fibrosis during momelotinib or ruxolitinib therapy do not correlate with efficacy outcomes in patients with myelofibrosis

Bone marrow fibrosis (BMF) is a pathological feature of myelofibrosis, with higher grades associated with poor prognosis. Limited data exist on the association between outcomes and BMF changes. We present BMF data from Janus kinase (JAK) inhibitor-naive patients from SIMPLIFY-1 (NCT01969838), a double-blind, randomized, phase 3 study of momelotinib vs ruxolitinib. Baseline and week 24 bone marrow biopsies were graded from 0 to 3 as per World Health Organization criteria. Other assessments included Total Symptom Score, spleen volume, transfusion independence status, and hemoglobin levels. Paired samples were available from 144 and 160 patients randomized to momelotinib and ruxolitinib. With momelotinib and ruxolitinib, transfusion independence was achieved by 87% and 44% of patients with BMF improvement of ≥1 grade and 76% and 56% of those with stable/worsening BMF; there was no association between BMF changes and transfusion independence for either arm (momelotinib, p = .350; ruxolitinib, p = .096). Regardless of BMF changes, hemoglobin levels also generally increased on momelotinib but decreased on ruxolitinib. In addition, no associations between BMF changes and spleen (momelotinib, p = .126; ruxolitinib, p = .407)/symptom (momelotinib, p = .617; ruxolitinib, p = .833) outcomes were noted, and no improvement in overall survival was observed with ≥1-grade BMF improvement (momelotinib, p = .395; ruxolitinib, p = .407). These data suggest that the anemia benefit of momelotinib is not linked to BMF changes, and question the use of BMF assessment as a surrogate marker for clinical benefit with JAK inhibitors.

Golidocitinib, a selective JAK1 tyrosine-kinase inhibitor, in patients with refractory or relapsed peripheral T-cell lymphoma (JACKPOT8 Part B): a single-arm, multinational, phase 2 study

BACKGROUND

Golidocitinib, a selective JAK1 tyrosine-kinase inhibitor, has shown encouraging anti-tumour activity in heavily pre-treated patients with relapsed or refractory peripheral T-cell lymphoma in a phase 1 study (JACKPOT8 Part A). Here, we report the full analysis of a phase 2 study, in which we assessed the anti-tumour activity of golidocitinib in a large multinational cohort of patients.

METHODS

We did a single-arm, multinational, phase 2 trial (JACKPOT8 Part B) in 49 centres in Australia, China, South Korea, and the USA. Eligible patients were adults (aged ≥18 years) with relapsed or refractory peripheral T-cell lymphoma who had received at least one previous line of systemic therapy and an Eastern Cooperative Oncology Group performance status of 0-2. Patients were given oral golidocitinib 150 mg once daily until disease progression or other discontinuation criteria were met. The primary endpoint was the CT-based objective response rate, assessed by an independent review committee (IRC) per Lugano 2014 classification. The activity analysis set included all patients who received at least one dose and whose pathological diagnosis of peripheral T-cell lymphoma had been retrospectively confirmed by a central laboratory and who had at least one measurable lesion at baseline assessed by IRC. The safety analysis set included all patients who received at least one dose of study drug. This study is registered with ClinicalTrials.gov, NCT04105010, and is closed to accrual and follow-up is ongoing.

FINDINGS

Between Feb 26, 2021, and Oct 12, 2022, we assessed 161 patients for eligibility, of whom 104 (65%) were enrolled and received at least one dose of study drug; the activity analysis set included 88 (85%) patients (median age 58 years [IQR 51-67], 57 [65%] of 88 were male, 31 [35%] were female, and 83 [94%] were Asian). As of data cutoff (Aug 31, 2023; median follow-up was 13·3 months [IQR 4·9-18·4]), per IRC assessment, the objective response rate was 44·3% (95% CI 33·7-55·3; 39 of 88 patients, p<0·0001), with 21 (24%) patients having a complete response and 18 (20%) having a partial response. In the safety analysis set, 61 (59%) of 104 patients had grade 3-4 drug-related treatment-emergent adverse events. The most common grade 3-4 drug-related treatment-emergent adverse events were neutrophil count decreased (30 [29%]), white blood cell count decreased (27 [26%]), lymphocyte count decreased (22 [21%]), and platelet count decreased (21 [20%]), which were clinically manageable and reversible. 25 (24%) patients had treatment-related serious adverse events. Deaths due to treatment-emergent adverse events occurred in three (3%) patients: two (2%) due to pneumonia (one case with fungal infection [related to golidocitinib] and another one with COVID-19 infection) and one (1%) due to confusional state.

INTERPRETATION

In this phase 2 study, golidocitinib showed a favourable benefit-risk profile in treating relapsed or refractory peripheral T-cell lymphoma. The results of this study warrant further randomised clinical studies to confirm activity and assess efficacy in this population.

FUNDING

Dizal Pharmaceutical.

ACVR1: A Novel Therapeutic Target to Treat Anemia in Myelofibrosis

Activin receptor type I (ACVR1) is a transmembrane kinase receptor belonging to bone morphogenic protein receptors (BMPs). ACVR1 plays an important role in hematopoiesis and anemia via the BMP6/ACVR1/SMAD pathway, which regulates expression of hepcidin, the master regulator of iron homeostasis. Elevated hepcidin levels are inversely associated with plasma iron levels, and chronic hepcidin expression leads to iron-restricted anemia. Anemia is one of the hallmarks of myelofibrosis (MF), a bone marrow (BM) malignancy characterized by BM scarring resulting in impaired hematopoiesis, splenomegaly, and systemic symptoms. Anemia and red blood cell transfusions negatively impact MF prognosis. Among the approved JAK inhibitors (ruxolitinib, fedratinib, momelotinib, and pacritinib) for MF, momelotinib and pacritinib are preferably used in cytopenic patients; both agents are potent ACVR1 inhibitors that suppress hepcidin expression via the BMP6/ACVR1/SMAD pathway and restore iron homeostasis/erythropoiesis. In September 2023, momelotinib was approved as a treatment for patients with MF and anemia. Zilurgisertib (ACVR1 inhibitor) and DISC-0974 (anti-hemojuvelin monoclonal antibody) are evaluated in early phase clinical trials in patients with MF and anemia. Luspatercept (ACVR2B ligand trap) is assessed in transfusion-dependent MF patients in a registrational phase 3 trial. Approved ACVR1 inhibitors and novel agents in development are poised to improve the outcomes of anemic MF patients.

Synthesis and clinical application of small-molecule inhibitors of Janus kinase

Janus kinase (JAK) plays a crucial role in intracellular signaling pathways, particularly in cytokine-mediated signal transduction, making them attractive therapeutic targets for a wide range of diseases, including autoimmune disorders, myeloproliferative neoplasms, and inflammatory conditions. The review provides a comprehensive overview of the development and therapeutic potential of small-molecule inhibitors targeting JAK family of proteins in various clinical trials. It also discusses the mechanisms of action, specificity, and selectivity of these inhibitors, shedding light on the challenges associated with achieving target selectivity while minimizing off-target effects. Moreover, the review offers insights into the clinical applications of JAK inhibitors, summarizing the ongoing clinical trials and the Food and Drug Administration (FDA)-approved JAK inhibitors currently available for various diseases. Overall, this review provides a thorough examination of the synthesis and clinical use of typical small-molecule JAK inhibitors in different clinical stages and offers a bright future for the development of novel small-molecule JAK inhibitors.

Precision medicine in nasopharyngeal carcinoma: comprehensive review of past, present, and future prospect

Nasopharyngeal carcinoma (NPC) is an aggressive malignancy with high propensity for lymphatic spread and distant metastasis. It is prominent as an endemic malignancy in Southern China and Southeast Asia regions. Studies on NPC pathogenesis mechanism in the past decades such as through Epstein Barr Virus (EBV) infection and oncogenic molecular aberrations have explored several potential targets for therapy and diagnosis. The EBV infection introduces oncoviral proteins that consequently hyperactivate many promitotic pathways and block cell-death inducers. EBV infection is so prevalent in NPC patients such that EBV serological tests were used to diagnose and screen NPC patients. On the other hand, as the downstream effectors of oncogenic mechanisms, the promitotic pathways can potentially be exploited therapeutically. With the apparent heterogeneity and distinct molecular aberrations of NPC tumor, the focus has turned into a more personalized treatment in NPC. Herein in this comprehensive review, we depict the current status of screening, diagnosis, treatment, and prevention in NPC. Subsequently, based on the limitations on those aspects, we look at their potential improvements in moving towards the path of precision medicine. The importance of recent advances on the key molecular aberration involved in pathogenesis of NPC for precision medicine progression has also been reported in the present review. Besides, the challenge and future outlook of NPC management will also be highlighted.

Androgen use in bone marrow failures and myeloid neoplasms: Mechanisms of action and a systematic review of clinical data

Despite recent advancements, treatment of cytopenia due to bone marrow failures (BMF) and myeloid neoplasms remains challenging. Androgens promote renewal and maturation of blood cells and may be beneficial in these forms. Here we report a systematic review of androgens use as single agent in hematologic conditions. Forty-six studies, mainly retrospective with various androgen types and doses, were included: 12 on acquired aplastic anemia (AA), 11 on inherited BMF, 17 on myelodysplastic syndromes (MDS), and 7 on myelofibrosis. Responses ranged from 50 to 70% in inherited BMF, 40-50% in acquired AA and MDS, while very limited evidence emerged for myelofibrosis. In acquired AA, response was associated with presence of non-severe disease; in MDS androgens were more effective on thrombocytopenia or mild to moderate anemia, whilst limited benefit was observed for transfusion dependent anemia. Toxicity profile mainly consisted of virilization and liver enzyme elevation, whilst the risk of leukemic evolution remains controversial.

Proteogenetic drug response profiling elucidates targetable vulnerabilities of myelofibrosis

Myelofibrosis is a hematopoietic stem cell disorder belonging to the myeloproliferative neoplasms. Myelofibrosis patients frequently carry driver mutations in either JAK2 or Calreticulin (CALR) and have limited therapeutic options. Here, we integrate ex vivo drug response and proteotype analyses across myelofibrosis patient cohorts to discover targetable vulnerabilities and associated therapeutic strategies. Drug sensitivities of mutated and progenitor cells were measured in patient blood using high-content imaging and single-cell deep learning-based analyses. Integration with matched molecular profiling revealed three targetable vulnerabilities. First, CALR mutations drive BET and HDAC inhibitor sensitivity, particularly in the absence of high Ras pathway protein levels. Second, an MCM complex-high proliferative signature corresponds to advanced disease and sensitivity to drugs targeting pro-survival signaling and DNA replication. Third, homozygous CALR mutations result in high endoplasmic reticulum (ER) stress, responding to ER stressors and unfolded protein response inhibition. Overall, our integrated analyses provide a molecularly motivated roadmap for individualized myelofibrosis patient treatment.

A Journey Through JAK Inhibitors for the Treatment of Myeloproliferative Diseases

PURPOSE OF REVIEW

Chronic myeloproliferative neoplasms (MPN) represent a group of diseases characterised by constitutive activation of the JAK/STAT pathway in a clonal myeloid precursor. The therapeutic approach aims to treat the symptom burden (headache, itching, debilitation), splenomegaly, slow down the fibrotic proliferation in the bone marrow and reduce the risk of thrombosis/bleeding whilst avoiding leukaemic transformation.

RECENT FINDINGS

In recent years, the advent of JAK inhibitors (JAKi) has significantly broadened treatment options for these patients. In myelofibrosis, symptom control and splenomegaly reduction can improve quality of life with improved overall survival, not impacting progression into acute leukaemia. Several JAKi are available and used worldwide, and combination approaches are now being explored. In this chapter, we review the approved JAKi, highlighting its strengths, exploring potential guidelines in choosing which one to use and reasoning towards future perspectives, where the combinations of therapies seem to promise the best results.

The pharmacotherapeutic management of patients with myelofibrosis: looking beyond JAK inhibitors

INTRODUCTION

The approach to myelofibrosis (MF) has been revolutionized in recent years, overcoming the traditional therapies, often not very effective. Janus kinase inhibitors (JAKi - from ruxolitinib up to momelotinib) were the first class of drugs with considerable results.

AREAS COVERED

Ongoing, new molecules are being tested that promise to give hope even to those patients not eligible for bone marrow transplants who become intolerant or are refractory to JAKi, for which therapeutic hopes are currently limited. Telomerase, murine double minute 2 (MDM2), phosphatidylinositol 3-kinase δ (PI3Kδ), BCL-2/xL, and bromodomain and extra-terminal motif (BET) inhibitors are the drugs with promising results in clinical trials and close to closure with consequent placing on the market, finally allowing JAK to look beyond. The novelty of the MF field was searched in the PubMed database, and the recently completed/ongoing trials are extrapolated from the ClinicalTrial website.

EXPERT OPINION

From this point of view, the use of new molecules widely described in this review, probably in association with JAKi, will represent the future treatment of choice in MF, leaving, in any case, the potential new approaches actually in an early stage of development, such as the use of immunotherapy in targeting CALR, which is coming soon.

Advances in management of primary myelofibrosis and polycythaemia vera: Implications in clinical practice

Primary myelofibrosis (PMF) and polycythaemia vera (PV) are rare BCR-ABL1-negative myeloproliferative neoplasms, associated with an increased risk of thrombosis, haemorrhagic complications and progression to fibrosis or leukaemia or fibrosis for PV. Both diseases are characterised by biological and clinical heterogeneity, leading to great variability in their management in routine clinical practice. In this review, we present an updated overview of the diagnosis, prognosis and treatment of PMF and PV, and we discuss how our multidisciplinary expert group based across France translates this evidence-based knowledge into routine clinical practice.

Novel Janus-kinase (JAK) Inhibitors in Myelofibrosis

INTRODUCTION

JAK inhibitors (JAKis), used in the treatment of myelofibrosis, have entered standard treatment, providing significant improvements in spleen size and symptom burden. Although splenomegaly provides a reduction and some improvement in cytopenia, there is still a way to go. Novel JAKis are being investigated to overcome barriers to treatment access, such as therapeutic challenges, intolerance, and unresponsiveness.

AREAS COVERED

This review includes the current status of JAKi treatment for myelofibrosis, mainly focusing on investigational JAKis; jaktinib, lestaurtinib, itacitinib, gandotinib, BMS-911543, ilginatinib, TQ05105, and flonoltinib maleate. MEDLINE and clinicaltrials.gov were screened to identify all completed or active studies on this topic. The outcomes of the preclinical studies and clinical trials are presented and discussed for each drug.

EXPERT OPINION

In patients with myelofibrosis, momelotinib was effective in treating anemia, whereas jaktinib was effective in both anemia and Total Symptom Score (TSS). More phase 3 studies are needed to provide more precise evidence. The increasing variety of JAKis will allow for more personalized treatment options for myelofibrosis in the future. The potential impact on disease progression, molecular responses, and the duration of this response will become important parameters for future evaluations of these drugs.

Association of Myelofibrosis Phenotypes with Clinical Manifestations, Molecular Profiles, and Treatments

Myelofibrosis (MF) presents an array of clinical manifestations and molecular profiles. The two distinct phenotypes- myeloproliferative and myelodepletive or cytopenic- are situated at the two poles of the disease spectrum and are largely defined by different degrees of cytopenias, splenomegaly, and distinct molecular profiles. The myeloproliferative phenotype is characterized by normal/higher peripheral blood counts or mildly decreased hemoglobin, progressive splenomegaly, and constitutional symptoms. The myeloproliferative phenotype is typically associated with secondary MF, higher JAK2 V617F burden, fewer mutations, and superior overall survival (OS). The myelodepletive phenotype is usually associated with primary MF, ≥2 cytopenias, modest splenomegaly, lower JAK2 V617F burden, higher fibrosis, greater genomic complexity, and inferior OS. Cytopenias are associated with mutations in epigenetic regulators/splicing factors, clonal evolution, disease progression, and shorter OS. Clinical variables, in conjunction with the molecular profiles, inform integrated prognostication and disease management. Ruxolitinib/fedratinib and pacritinib/momelotinib may be more suitable to treat patients with the myeloproliferative and myelodepletive phenotypes, respectively. Appreciation of MF heterogeneity and two distinct phenotypes, the different clinical manifestations and molecular profiles associated with each phenotype alongside the growing treatment expertise, the development of non-myelosuppressive JAK inhibitors, and integrated prognostication are leading to a new era in patient management. Physicians can increasingly tailor personalized treatments that will address the unique unmet needs of MF patients, including those presenting with the myelodepletive phenotype, to elicit optimal outcomes and extended OS across the disease spectrum.

Benefit of Early Ruxolitinib Initiation Regardless of Fibrosis Grade in Patients with Primary Myelofibrosis: A Post Hoc Analysis of the Single-Arm Phase 3b JUMP Study

Bone marrow fibrosis (BMF) is an adverse prognostic factor for myelofibrosis (MF). The single-arm, open-label, phase 3b JUMP trial (NCT01493414) assessed the safety and efficacy of the JAK1/JAK2 inhibitor ruxolitinib in patients with symptomatic MF. This post hoc analysis investigated the impact of BMF grade on response and outcomes in patients with primary MF (PMF) from the JUMP study. BMF was assessed by biopsy and graded from 0 to 3; grades 0-1 were considered low-grade fibrosis (LGF) and grades 2-3 were considered high-grade fibrosis (HGF). Patients with LGF (n = 268) had lower rates of cytopenias at baseline but showed comparable disease burden vs. patients with HGF (n = 852). The proportion of patients achieving a spleen response was greater in the LGF group vs. the HGF group at Week 24 and at any time during the study, while overall survival estimates were improved in patients with LGF vs. patients with HGF. Early initiation of ruxolitinib therapy (within 2 years of diagnosis) was associated with increased response rates in all patients. These results highlight the efficacy of ruxolitinib in symptomatic patients with PMF, with the greatest clinical improvements observed in patients with LGF and in patients who received early treatment.

Ten years after ruxolitinib approval for myelofibrosis: a review of clinical efficacy

Myelofibrosis (MF) is a chronic myeloproliferative neoplasm characterized by splenomegaly, abnormal cytokine expression, cytopenias, and progressive bone marrow fibrosis. The disease often manifests with burdensome symptoms and is associated with reduced survival. Ruxolitinib, an oral Janus kinase (JAK) 1 and JAK2 inhibitor, was the first agent approved for MF. As a first-in-class targeted treatment, ruxolitinib approval transformed the MF treatment approach and remains standard of care. In addition, targeted inhibition of JAK1/JAK2 signaling, a key molecular pathway underlying MF pathogenesis, and the large volume of literature evaluating ruxolitinib, have led to a better understanding of the disease and improved management in general. Here we review ruxolitinib efficacy in patients with MF in the 10 years following approval, including demonstration of clinical benefit in the phase 3 COMFORT-I/II trials, real-world evidence, translational studies, and expanded access data. Lastly, future directions for MF treatment are discussed, including ruxolitinib-based combination therapies.

SOHO State of the Art Updates and Next Questions: Novel Therapeutic Strategies in Development for Myelofibrosis

Development of myelofibrosis (MF) therapeutics has reached fruition as the transformative impact of JAK2 inhibitors in the MPN landscape is complemented/expanded by a profusion of novel monotherapies and rational combinations in the frontline and second line settings. Agents in advanced clinical development span various mechanisms of action (eg, epigenetic or apoptotic regulation), may address urgent unmet clinical needs (cytopenias), increase the depth/duration of spleen and symptom responses elicited by ruxolitinib, improve other aspects of the disease besides splenomegaly/constitutional symptoms (eg, resistance to ruxolitinib, bone marrow fibrosis or disease course), provide personalized strategies, and extend overall survival (OS). Ruxolitinib had a dramatic impact on the quality of life and OS of MF patients. Recently, pacritinib received regulatory approval for severely thrombocytopenic MF patients. Momelotinib is advantageously poised among JAK inhibitors given its differentiated mode of action (suppression of hepcidin expression). Momelotinib demonstrated significant improvements in anemia measures, spleen responses, and MF-associated symptoms in MF patients with anemia; and will likely receive regulatory approval in 2023. An array of other novel agents combined with ruxolitinib, such as pelabresib, navitoclax, parsaclisib, or as monotherapies (navtemadlin) are evaluated in pivotal phase 3 trials. Imetelstat (telomerase inhibitor) is currently evaluated in the second line setting; OS was set as the primary endpoint, marking an unprecedented goal in MF trials, wherein SVR35 and TSS50 at 24 weeks have been typical endpoints heretofore. Transfusion independence may be considered another clinically meaningful endpoint in MF trials given its correlation with OS. Overall, therapeutics are at the cusp of an exponential expansion and advancements that will likely lead to the golden era in treatment of MF.

Myelofibrosis and Survival Prognostic Models: A Journey between Past and Future

Among the myeloproliferative diseases, myelofibrosis is a widely heterogeneous entity characterized by a highly variable prognosis. In this context, several prognostic models have been proposed to categorize these patients appropriately. Identifying who deserves more invasive treatments, such as bone marrow transplantation, is a critical clinical need. Age, complete blood count (above all, hemoglobin value), constitutional symptoms, driver mutations, and blast cells have always represented the milestones of the leading models still used worldwide (IPSS, DIPSS, MYSEC-PM). Recently, the advent of new diagnostic techniques (among all, next-generation sequencing) and the extensive use of JAK inhibitor drugs have allowed the development and validation of new models (MIPSS-70 and version 2.0, GIPSS, RR6), which are continuously updated. Finally, the new frontier of artificial intelligence promises to build models capable of drawing an overall survival perspective for each patient. This review aims to collect and summarize the existing standard prognostic models in myelofibrosis and examine the setting where each of these finds its best application.

Early intervention in myelofibrosis and impact on outcomes: A pooled analysis of the COMFORT-I and COMFORT-II studies

BACKGROUND

In a pooled analysis of the phase 3 Controlled Myelofibrosis Study With Oral JAK Inhibitor Treatment I (COMFORT-I) and COMFORT-II clinical trials, adult patients with intermediate-2 or high-risk myelofibrosis who received oral ruxolitinib at randomization or after crossover from placebo or best available therapy (BAT) had improved overall survival (OS).

METHODS

This post hoc analysis of pooled COMFORT data examined relevant disease outcomes based on the disease duration (≤12 or >12 months from diagnosis) before ruxolitinib initiation.

RESULTS

The analysis included 525 patients (ruxolitinib: ≤12 months, n = 84; >12 months, n = 216; placebo/BAT: ≤12 months, n = 66; >12 months, n = 159); the median age was 65.0-70.0 years. Fewer thrombocytopenia and anemia events were observed among patients who initiated ruxolitinib treatment earlier. At Weeks 24 and 48, the spleen volume response (SVR) was higher for patients who initiated ruxolitinib earlier (47.6% vs. 32.9% at Week 24, p = .0610; 44.0% vs. 26.9% at Week 48, p = .0149). In a multivariable analysis of factors associated with spleen volume reduction, a logistic regression model that controlled for confounding factors found that a significantly greater binary reduction was observed among patients with shorter versus longer disease duration (p = .022). At Week 240, OS was significantly improved among patients who initiated ruxolitinib earlier (63% [95% CI, 51%-73%] vs. 57% [95% CI, 49%-64%]; hazard ratio, 1.53; 95% CI, 1.01-2.31; p = .0430). Regardless of disease duration, a longer OS was observed for patients who received ruxolitinib versus those who received placebo/BAT.

CONCLUSIONS

These findings suggest that earlier ruxolitinib initiation for adult patients with intermediate-2 and high-risk myelofibrosis may improve clinical outcomes, including fewer cytopenia events, durable SVR, and prolonged OS.

PLAIN LANGUAGE SUMMARY

Patients with myelofibrosis, a bone marrow cancer, often do not live as long as the general population. These patients may also have an enlarged spleen and difficult symptoms such as fatigue. Two large clinical trials showed that patients treated with the drug ruxolitinib lived longer and had improved symptoms compared to those treated with placebo or other standard treatments. Here it was examined whether starting treatment with ruxolitinib earlier (i.e., within a year of diagnosis) provided benefits versus delaying treatment. Patients who received ruxolitinib within a year of diagnosis lived longer and experienced fewer disease symptoms than those whose treatment was delayed.

Treatment-resistant idiopathic multicentric Castleman disease with thrombocytopenia, anasarca, fever, reticulin fibrosis, renal dysfunction, and organomegaly managed with Janus kinase inhibitors: A case report

RATIONALE

Thrombocytopenia, anasarca, fever, reticulin fibrosis, renal dysfunction, and organomegaly (TAFRO) syndrome are nonmalignant but life-threatening systemic inflammatory disorders. However, many patients are refractory to treatment, resulting in significant morbidity and mortality. Additionally, established treatment options are unavailable. Therefore, we present 2 cases of adults with the iMCD-TAFRO syndrome refractory to initial treatment but responded to Janus kinase (JAK) inhibitors with ruxolitinib. The report reveals that these rare adult cases of the refractory and treatment-resistant iMCD-TAFRO syndrome can be treated using JAK inhibitors.

PATIENT CONCERNS

Case 1 is a 36-year-old previously healthy male patient who presented with fever and general fatigue for 2 weeks. Case 2 is a 42-year-old previously healthy female patient who presented with fever and general fatigue.

DIAGNOSIS

The diagnosis met the 2015 criteria for TAFRO syndrome, as determined by All Japan TAFRO Syndrome Research Group in the Research Program for Intractable Disease by the Ministry of Health, Labor and Welfare (MHLW) Japan.

INTERVENTIONS

Treatment with tocilizumab and several immunosuppressants were ineffective. So, we performed ruxolitinib.

OUTCOMES

Each patient received ruxolitinib, the general condition improved, and CRP levels decreased.

LESSONS

These cases showed that ruxolitinib was effective for treatment-resistant/ refractory TAFRO syndrome. Further prospective studies are needed on using ruxolitinib with a small number of cases.

Myelofibrosis treatment history and future prospects

Myelofibrosis (MF) is a haematopoietic stem cell tumour caused by the lack of BCR-ABL translocation due to point mutations in Janus kinases (JAKs). In previous years, dealing with MF included several protocols such as traditional drugs that control general symptoms, splenectomy, blood transfusion, and allogeneic haematopoietic stem-cell transplantation (HSCT). Allogeneic HSCT is remaining the only treatment that has the potential to alter MF’s progression. However, clinical trials of JAK inhibitors and non-JAK targeted therapies have been increasingly carried out in earlier years. The most prominent JAK inhibitors for the treatment of MF are ruxolitinib, fedratinib, momelotinib, pacritinib, gandotinib, ilginatinib, itacitinib, and lestaurtinib. On the other hand, the non-JAK targeted therapies that showed strong efficacy and safety are alisertib, imetelstat, pembrolizumab, nivolumab, and sotatercept. In this review, we summarized the recent clinical trials carried out on these drugs to understand their efficacy and safety. Also, we talked briefly about allogeneic HSCT as powerful therapy until the present for patients suffering from MF.

BOREAS: a global, phase III study of the MDM2 inhibitor navtemadlin (KRT-232) in relapsed/refractory myelofibrosis

Patients with myelofibrosis (MF) who discontinue ruxolitinib due to progression/resistance have poor prognoses. JAK inhibitors control symptoms and reduce spleen volumes with limited impact on underlying disease pathophysiology. Murine double minute 2 (MDM2), a negative regulator of p53, is overexpressed in circulating malignant CD34+ MF cells. The oral MDM2 inhibitor navtemadlin (KRT-232) restores p53 activity to drive apoptosis of wild-type TP53 tumor cells by inducing expression of pro-apoptotic Bcl-2 family proteins. Navtemadlin demonstrated promising clinical and disease-modifying activity and acceptable safety in a phase II study in patients with relapsed/refractory MF. The randomized phase III BOREAS study compares the efficacy and safety of navtemadlin to best available therapy in patients with MF that is relapsed/refractory to JAK inhibitor treatment.

Dual therapy with an angiotensin receptor blocker and a JAK1/2 inhibitor attenuates dialysate-induced angiogenesis and preserves peritoneal membrane structure and function in an experimental CKD rat model

BACKGROUND

Peritoneal dialysis (PD) is limited by reduced efficacy over time. We previously showed that a Janus kinase 1/2 inhibitor (JAK1/2i) reduced inflammation, hypervascularity and fibrosis induced by 4.25% dextrose dialysate (4.25%D) intraperitoneally (IP) infused for 10 days in rats with normal kidney function. JAK/STAT signalling mediates inflammatory pathways, including angiotensin signalling. We now tested the effect of long-term JAK1/2i and/or an angiotensin receptor blocker (ARB) on peritoneal membrane (PM) in polycystic kidneys (PCK) rats infused with 4.25%D.

METHODS

Except for controls, all PCK rats had a tunnelled PD catheter: (1) no infusions; (2) 4.25%D; (3) 4.25%D + JAK1/2i (5 mg/kg); (4) 4.25%D +losartan (5 mg/kg); and (5) 4.25%D + losartan +JAK1/2i (5 mg/kg each) IP BID × 16 weeks (N = 5/group). PM VEGFR2 staining areas and submesothelial compact zone (SMCZ) width were morphometrically measured. Peritoneal equilibration testing measured peritoneal ultrafiltration (UF) by calculating dialysate glucose at time 0 and 90 min (D/D₀ glucose).

RESULTS

4.25%D caused hypervascularity, SMCZ widening, fibrosis and UF functional decline in PCK rats. Angiogenesis was significantly attenuated by JAK1/2i ± ARB but not by ARB monotherapy. Both treatments reduced SMCZ area. UF was preserved consistently by dual therapy (p < 0.05) but with inconsistent responses by monotherapies.

CONCLUSION

Long-term JAK1/2i ± ARB reduced angiogenesis and fibrosis, and the combination consistently maintained UF. In clinical practice, angiotensin inhibition has been advocated to maintain residual kidney function. Our study suggests that adding JAK1/2i to angiotensin inhibition may preserve PM structure and UF.

JAK2 Alterations in Acute Lymphoblastic Leukemia: Molecular Insights for Superior Precision Medicine Strategies

Acute lymphoblastic leukemia (ALL) is the most common pediatric cancer, arising from immature lymphocytes that show uncontrolled proliferation and arrested differentiation. Genomic alterations affecting Janus kinase 2 (JAK2) correlate with some of the poorest outcomes within the Philadelphia-like subtype of ALL. Given the success of kinase inhibitors in the treatment of chronic myeloid leukemia, the discovery of activating JAK2 point mutations and JAK2 fusion genes in ALL, was a breakthrough for potential targeted therapies. However, the molecular mechanisms by which these alterations activate JAK2 and promote downstream signaling is poorly understood. Furthermore, as clinical data regarding the limitations of approved JAK inhibitors in myeloproliferative disorders matures, there is a growing awareness of the need for alternative precision medicine approaches for specific JAK2 lesions. This review focuses on the molecular mechanisms behind ALL-associated JAK2 mutations and JAK2 fusion genes, known and potential causes of JAK-inhibitor resistance, and how JAK2 alterations could be targeted using alternative and novel rationally designed therapies to guide precision medicine approaches for these high-risk subtypes of ALL.

Dual-target Janus kinase (JAK) inhibitors: Comprehensive review on the JAK-based strategies for treating solid or hematological malignancies and immune-related diseases

Janus kinases (JAKs) are the non-receptor tyrosine kinases covering JAK1, JAK2, JAK3, and TYK2 which regulate signal transductions of hematopoietic cytokines and growth factors to play essential roles in cell growth, survival, and development. Dysregulated JAK activity leading to a constitutively activated signal transducers and activators of transcription (STAT) is strongly associated with immune-related diseases and cancers. Targeting JAK to interfere the signaling of JAK/STAT pathway has achieved quite success in the treatment of these diseases. However, inadequate clinical response and serious adverse events come along by the treatment of monotherapy of JAK inhibitors. With better and deeper understanding of JAK/STAT pathway in the pathogenesis of diseases, researchers start to show huge interest in combining inhibition of JAK and other oncogenic targets to realize a broader regulation on pathological processes to block disease development and progression, which has hastened extensive research of dual JAK inhibitors over the past decades. Until now, studies of dual JAK inhibitors have added BTK, SYK, FLT3, HDAC, Src, and Aurora kinases to the overall inhibitory profile and demonstrated significant advantage and superiority over single-target inhibitors. In this review, we elucidated the possible mechanism of synergic effects caused by dual JAK inhibitors and briefly describe the development of these agents.

Addition of Navitoclax to Ongoing Ruxolitinib Therapy for Patients With Myelofibrosis With Progression or Suboptimal Response: Phase II Safety and Efficacy

PURPOSE

Targeting the BCL-XL pathway has demonstrated the ability to overcome Janus kinase inhibitor resistance in preclinical models. This phase II trial investigated the efficacy and safety of adding BCL-XL/BCL-2 inhibitor navitoclax to ruxolitinib therapy in patients with myelofibrosis with progression or suboptimal response to ruxolitinib monotherapy (ClinicalTrials.gov identifier: NCT03222609).

METHODS

Thirty-four adult patients with intermediate-/high-risk myelofibrosis who had progression or suboptimal response on stable ruxolitinib dose (≥ 10 mg twice daily) were administered navitoclax at 50 mg once daily starting dose, followed by escalation to a maximum of 300 mg once daily in once in weekly increments (if platelets were ≥ 75 × 109/L). The primary end point was ≥ 35% spleen volume reduction (SVR35) from baseline at week 24. Secondary end points included ≥ 50% reduction in total symptom score (TSS50) from baseline at week 24, hemoglobin improvement, change in bone marrow fibrosis (BMF) grade, and safety.

RESULTS

High molecular risk mutations were identified in 58% of patients, and 52% harbored ≥ 3 mutations. SVR35 was achieved by 26.5% of patients at week 24, and by 41%, at any time on study, with an estimated median duration of SVR35 of 13.8 months. TSS50 was achieved by 30% (6 of 20) of patients at week 24, and BMF improved by 1-2 grades in 33% (11 of 33) of evaluable patients. Anemia response was achieved by 64% (7 of 11), including one patient with baseline transfusion dependence. Median overall survival was not reached with a median follow-up of 21.6 months. The most common adverse event was reversible thrombocytopenia without clinically significant bleeding (88%).

CONCLUSION

The addition of navitoclax to ruxolitinib in patients with persistent or progressive myelofibrosis resulted in durable SVR35, improved TSS, hemoglobin response, and BMF. Further investigation is underway to qualify the potential for disease modification.

State-of-the-Art Review on Myelofibrosis Therapies

Myelofibrosis (MF) is a BCR-ABL1-negative myeloproliferative neoplasm characterized by anemia, extramedullary hematopoiesis, bone marrow fibrosis, splenomegaly, constitutional symptoms and acute myeloid leukemia progression. Currently, allogeneic haematopoietic stem cell transplantation (AHSCT) therapy is the only curative option for MF patients. However, AHSCT is strictly limited due to the high rates of morbidity and mortality. Janus kinase 2 (JAK2) inhibitor Ruxolitinib is the first-line treatment for intermediate-II or high-risk MF patients with splenomegaly and constitutional symptoms, but most MF patients develop resistance or intolerance to Ruxolitinib. Therefore, MF treatment is a challenge for the medical community. This review summarizes 3 investigated directions for MF therapy: monotherapies of JAK inhibitors, monotherapies of non-JAK targeted agents, combination therapies of Ruxolitinib and other agents. We emphasize combination of Ruxolitinib and other agents is a promising strategy.

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.

SOHO State of the Art Updates and Next Questions: Novel Therapies in Development for Myelofibrosis

Myeloproliferative neoplasms research has entered a dynamic and exciting era as we witness exponential growth of novel agents in advanced/early phase clinical trials for myelofibrosis (MF). Building on the success and pivotal role of ruxolitinib, many novel agents, spanning a wide range of mechanisms/targets (epigenetic regulation, apoptotic/intracellular signaling pathways, telomerase, bone marrow fibrosis) are in clinical development; several are studied in registrational trials and hold great potential to expand the therapeutic arsenal/shift the treatment paradigm if regulatory approval is granted. Insight into MF pathogenesis and its molecular underpinnings, preclinical studies demonstrating synergism of ruxolitinib with investigational agents, urgent unmet clinical needs (cytopenias, loss of response to JAK inhibitors); and progressive disease fueled the rapid rise of innovative therapeutics. New strategies include pairing ruxolitinib with erythroid maturation agents to manage anemia (luspatercept), designing rational combinations with ruxolitinib to boost responses in both the frontline and suboptimal response settings (pelabresib, navitoclax, parsaclisib), treatment with non-JAK inhibitor monotherapy in the second-line setting (navtemadlin, imetelstat), novel JAK inhibitors tailored to subgroups with challenging unmet needs (momelotinib and pacritinib for anemia and thrombocytopenia, respectively); and agents potentially enhancing longevity (imetelstat). Beyond typical endpoints evaluated in MF clinical trials (spleen volume reduction ≥ 35%, total symptom score reduction ≥ 50%) thus far, emerging endpoints include overall survival, progression-free survival, transfusion independence, anemia benefits, bone marrow fibrosis and driver mutation allele burden reduction. Novel biomarkers and additional clinical features are being sought to assess new agents and tailor emerging therapies to appropriate patients. New strategies are needed to optimize the design of clinical trials comparing novel combinations to standard agent monotherapy.

Type-I Interferon Signaling in Fanconi Anemia

Fanconi Anemia (FA) is a genome instability syndrome caused by mutations in one of the 23 repair genes of the Fanconi pathway. This heterogenous disease is usually characterized by congenital abnormalities, premature ageing and bone marrow failure. FA patients also show a high predisposition to hematological and solid cancers. The Fanconi pathway ensures the repair of interstrand crosslinks (ICLs) DNA damage. Defect in one of its proteins prevents functional DNA repair, leading to the accumulation of DNA breaks and genome instability. Accumulating evidence has documented a close relationship between genome instability and inflammation, including the production of type-I Interferon. In this context, type-I Interferon is produced upon activation of pattern recognition receptors by nucleic acids including by the cyclic GMP-AMP synthase (cGAS) that detects DNA. In mouse models of diseases displaying genome instability, type-I Interferon response is responsible for an important part of the pathological symptoms, including premature aging, short stature, and neurodegeneration. This is illustrated in mouse models of Ataxia-telangiectasia and Aicardi-Goutières Syndrome in which genetic depletion of either Interferon Receptor IFNAR, cGAS or STING relieves pathological symptoms. FA is also a genetic instability syndrome with symptoms such as premature aging and predisposition to cancer. In this review we will focus on the different molecular mechanisms potentially leading to type-I Interferon activation. A better understanding of the molecular mechanisms engaging type-I Interferon signaling in FA may ultimately lead to the discovery of new therapeutic targets to rescue the pathological inflammation and premature aging associated with Fanconi Anemia.

JAK2 inhibitor persistence in MPN: uncovering a central role of ERK activation

The Philadelphia chromosome negative myeloproliferative neoplasms, including polycythemia vera, essential thrombocytosis, and myelofibrosis, are driven by hyper activation of the JAK2 tyrosine kinase, the result of mutations in three MPN driving genes: JAK2, MPL, and CALR. While the anti-inflammatory effects of JAK2 inhibitors can provide improved quality of life for many MPN patients, the upfront and persistent survival of disease-driving cells in MPN patients undergoing JAK2 inhibitor therapy thwarts potential for remission. Early studies indicated JAK2 inhibitor therapy induces heterodimeric complex formation of JAK2 with other JAK family members leading to sustained JAK2-dependent signaling. Recent work has described novel cell intrinsic details as well as cell extrinsic mechanisms that may contribute to why JAK2 inhibition may be ineffective at targeting MPN driving cells. Diverse experimental strategies aimed at uncovering mechanistic details that contribute to JAK2 inhibitor persistence have each highlighted the role of MEK/ERK activation. These approaches include, among others, phosphoproteomic analyses of JAK2 signaling as well as detailed assessment of JAK2 inhibition in mouse models of MPN. In this focused review, we highlight these and other studies that collectively suggest targeting MEK/ERK in combination with JAK2 inhibition has the potential to improve the efficacy of JAK2 inhibitors in MPN patients. As MPN patients patiently wait for improved therapies, such studies should further strengthen optimism that pre-clinical research is continuing to uncover mechanistic insights regarding the ineffectiveness of JAK2 inhibitors, which may lead to development of improved therapeutic strategies.

Momelotinib: an emerging treatment for myelofibrosis patients with anemia

The suite of marked anemia benefits that momelotinib has consistently conferred on myelofibrosis (MF) patients stem from its unique inhibitory activity on the BMP6/ACVR1/SMAD and IL-6/JAK/STAT3 pathways, resulting in decreased hepcidin (master iron regulator) expression, higher serum iron and hemoglobin levels, and restored erythropoiesis. Clinical data on momelotinib from the phase 2 and the two phase 3 SIMPLIFY trials consistently demonstrated high rates of sustained transfusion-independence. In a recent phase 2 translational study, 41% of the patients achieved transfusion independence for ≥ 12 weeks. In the phase 3 trials SIMPLIFY-1 and SIMPLIFY-2, 17% more JAK inhibitor-naïve patients and two-fold more JAK inhibitor-treated patients achieved or maintained transfusion independence with momelotinib versus ruxolitinib and best available therapy (89% ruxolitinib), respectively. Anemia is present in approximately a third of MF patients at diagnosis, eventually developing in nearly all patients. The need for red blood cell transfusions is an independent adverse risk factor for both overall survival and leukemic transformation. Presently, FDA-approved medications to address anemia are lacking. Momelotinib is one of the prime candidates to durably address the critical unmet needs of MF patients with moderate/severe anemia. Importantly, momelotinib may have overall survival benefits in frontline and second-line MF patients. MOMENTUM is an international registration-track phase 3 trial further assessing momelotinib’s unique constellation of anemia and other benefits in second-line MF patients; the results of the MOMENTUM trial are keenly awaited and may lead to regulatory approval of momelotinib.

OUP accepted manuscript

Background

This study analyses treatment patterns, health care resource utilization (HCRU), and costs in patients with myelofibrosis (MF) and a subgroup treated with ruxolitinib (RUX).

Materials and Methods

Treatment patterns, all-cause and MF-related HCRU, and costs were analyzed in adults with MF with continuous enrollment in a commercial or the Medicare Advantage health plan in the pre-index period, defined as the 12 months immediately prior to the index date (date of primary or secondary MF diagnosis), and the post-index period, defined as ≥6 months following the index date. In a subgroup analysis, outcomes were analyzed in patients treated with optimal RUX (OPT RUX, ≥30 mg) and suboptimal RUX (SUB RUX, <30 mg) in the pre-index RUX period, defined as the 3 months immediately prior to the index RUX date (first date for an RUX claim), and the post-index RUX period, defined as ≥6 months following the index RUX date.

Results

Of 2830 patients with an MF diagnosis, 1191 met eligibility requirements. The median age of patients was 72 years, 54% were male, and comorbidities were frequent. Sixty percent of patients received ≥1 line of therapy (LOT), of which 46% (n = 331) had ≥2 LOTs during the post-index MF period. Costs increased considerably 6-month pre-index to 6-month post-index (all-cause: cause ($24,216 to $48,966) and MF-related ($16,502 to $39,383), driven by inpatient stays and pharmacy costs. In the subgroup analysis, patients treated with RUX (n = 495) experienced significant disease burden and high costs, regardless of dose. A shorter duration of therapy and a higher rate of discontinuation were observed in patients treated with SUB RUX (n = 191) versus OPT RUX (n = 304).

Conclusion

These findings suggest a significant disease and economic impacts associated with MF patients that persists with RUX therapy, highlighting the need for additional therapeutic options for MF.

From cell to cell: Identification of actionable targets in bone marrow fibrosis using single-cell technologies

Single-cell technologies have rapidly developed in recent years and have already had a significant impact on the research of myeloproliferative neoplasms. The increasing number of publicly available data sets allows characterization of the bone marrow niche in patients and mouse models at unprecedented resolution. Single-cell RNA sequencing has successfully been used to identify and characterize disease-driving cell populations and to identify the alarmin S100A8/A9 as an important mediator of myelofibrosis and potent therapeutic target. It is now possible to execute a streamlined set of experiments to specifically identify and validate actionable target genes functionally with the advance of reliable in vivo models and the possibility of conducting single-cell analyses with a minimal amount of patient material. The advent of large-scale analyses of both hematopoietic and non-hematopoietic bone marrow cells will allow comprehensive network analyses guiding an increasingly detailed mapping of the MPN interactome.

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.

Ruxolitinib Inhibits IFNγ Licensing of Human Bone Marrow Derived Mesenchymal Stromal Cells

Ruxolitinib is a JAK2/JAK1 inhibitor that blocks the inflammatory JAK-STAT signaling pathway. Ruxolitinib has been demonstrated to be effective in the treatment of steroid-resistant acute graft-versus-host disease (GVHD). Ruxolitinib's effect on inflammatory cells of hematopoietic origin is known. However, its effect on nonhematopoietic cell types with immune-modulating and antigen-presenting cell competency plausibly involved in pathogenesis of GVHD has not been explored. Mesenchymal stromal cells (MSCs) are CD45^- nonhematopoietic cells of the bone marrow with immune modulatory functions in vivo. MSCs' immunobiology largely depends on their responsiveness to IFNγ. We aimed to define the effect of ruxolitinib on the immunobiology of MSCs that are modulated by IFNγ. Human bone marrow derived MSCs, peripheral blood mononuclear cells (PBMCs), and primary bone marrow aspirates were analyzed for their sensitivity to ruxolitinib-mediated blocking of IFNγ-induced STAT-1 phosphorylation and downstream effector molecules, utilizing Western blot, flow cytometry, secretome analysis, and phosflow techniques. IFNγ-induced cytostatic effects on MSCs are reversed by ruxolitinib. Ruxolitinib inhibits IFNγ and secretome of activated peripheral PBMC-induced STAT-1 phosphorylation on human bone marrow derived MSCs. In addition, ruxolitinib inhibits IFNγ-induced pro-GVHD pathways on MSCs, which includes HLAABC(MHCI), HLADR(MHCII), CX3CL1, and CCL2. IFNγ-induced immunosuppressive molecules IDO and PDL-1 were also inhibited by ruxolitinib on MSCs. Comparative analysis with PBMCs has demonstrated that MSCs are as equal as to HLADR⁺ PBMC populations in responding to ruxolitinib-mediated inhibition of IFNγ-induced STAT-1 phosphorylation. Ex vivo analysis of human marrow aspirates has demonstrated that ruxolitinib blocks IFNγ-induced STAT-1 phosphorylation in CD45^+/-HLADR^+/- populations at different levels, which is depending on their sensitivity to IFNγ responsiveness. These results inform the hypothesis that ruxolitinib's immune-modulatory effects in vivo may pharmacologically involve marrow and tissue-resident MSCs. Ruxolitinib affects the immunobiology of MSCs equivalent to professional HLADR⁺ antigen presenting cells, which collectively mitigate GVHD.

Targeting Abnormal Hematopoietic Stem Cells in Chronic Myeloid Leukemia and Philadelphia Chromosome-Negative Classical Myeloproliferative Neoplasms

Myeloproliferative neoplasms (MPNs) are unique hematopoietic stem cell disorders sharing mutations that constitutively activate the signal-transduction pathways involved in haematopoiesis. They are characterized by stem cell-derived clonal myeloproliferation. The key MPNs comprise chronic myeloid leukemia (CML), polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF). CML is defined by the presence of the Philadelphia (Ph) chromosome and BCR-ABL1 fusion gene. Despite effective cytoreductive agents and targeted therapy, complete CML/MPN stem cell eradication is rarely achieved. In this review article, we discuss the novel agents and combination therapy that can potentially abnormal hematopoietic stem cells in CML and MPNs and the CML/MPN stem cell-sustaining bone marrow microenvironment.

JAK-Inhibitoren für die Behandlung hämatoonkologischer Erkrankungen

Die konstitutive Aktivierung des JAK-STAT-Signalwegs ist charakteristisch für die Pathogenese der myeloproliferativen Neoplasien, speziell der primären Myelofibrose, der Polycythaemia vera und der essentiellen Thrombozythämie. Die Einführung von oral verfügbaren JAK-Inhibitoren in die Klinik brachte einen entscheidenden Fortschritt für die pharmakologische Behandlung der Myelofibrose und der Polycythaemia vera, wenngleich damit noch keine Heilung verbunden ist. Im Vordergrund steht die Verbesserung der Lebensqualität der meist älteren Patienten durch Kontrolle krankheitsbedingter konstitutioneller Symptome, Reduktion einer bestehenden Splenomegalie und Vermeidung insbesondere von thromboembolischen Folgekomplikationen. Darüber hinaus kann die Therapie von Myelofibrose-Patienten mit JAK-Inhibitoren jedoch auch deren Krankheitsverlauf verlangsamen und ihr Gesamtüberleben verlängern. Der bislang einzige in Europa zugelassene JAK-Inhibitor Ruxolitinib hemmt die Isoformen JAK1 und JAK2 und besitzt sowohl antiinflammatorisches als auch antiproliferatives Potenzial. Damit zeigt dieser Inhibitor überdies eine gute Wirkung in der Therapie der Graft-versus-Host-Erkrankung nach allogener hämatopoetischer Stammzelltransplantation. Mit Fedratinib, Pacritinib und Momelatinib befinden sich derzeit 3 weitere vielversprechende JAK-Inhibitoren mit etwas unterschiedlichen Wirkprofilen in der klinischen Phase III-Testung. Diese zeigen auch bei Patienten mit unwirksamer oder unverträglicher Vorbehandlung mit Ruxolitinib Wirksamkeit, sodass eine kontinuierliche Weiterentwicklung der entsprechenden Therapiestrategien abzusehen ist.