Defining disease modification in myelofibrosis in the era of targeted therapy

Pathogenesis and management of high molecular risk myeloproliferative neoplasms

Classical myeloproliferative neoplasms (MPN) are clonal stem cell disorders characterized by driver mutations that affect the constitutive activation of JAK-signaling. Mutations additional to an MPN-driver occur in a large number of patients and have been shown be associated with disease presentation and progression. In this review, we outline the current hypotheses regarding how clonal evolution in MPN is thought to occur and the functional mechanisms as to how concomitant somatic mutations (i.e., mutations in genes other than the 'driver' genes) contribute to disease progression. We discuss the definitions of high molecular risk MPN, provide an overview of how concomitant mutations influence the clinical management of MPN and suggest how the rapidly developing genetic risk stratification can be utilized to improve clinical outcomes.

Prevention and treatment of transformation of myeloproliferative neoplasms to acute myeloid leukemia

Philadelphia-chromosome negative myeloproliferative neoplasms (MPN) are hematopoietic stem disorders with a risk of progression to an accelerated phase (AP) or blast phase (BP) that is influenced by clinical, pathological, cytogenetic, and molecular variables. Overall survival of patients with MPN-AP/BP is limited with current treatment approaches, particularly in those patients who cannot receive an allogeneic hematopoietic stem cell transplant (allo-HCT). In addition, long-term survival with allo-HCT is predominantly seen in chronic-phase MPN, which suggests that the ideal time for intervention may be before the MPN evolves to AP/BP. In this review we focus on the risk factors for progression to MPN-AP/BP, identification of high-risk chronic-phase MPN, potential early-intervention strategies, and considerations around the timing of allo-HCT. We also summarize current survival outcomes of patients with MPN-AP/BP, discuss the uncertainty around how to best gauge response to therapy, and outline clinical trial considerations for this population of patients. Lastly, we highlight future directions in the management of high-risk MPN.

Optimization of allogeneic hematopoietic cell transplantation for patients with myelofibrosis treated with ruxolitinib: eligibility, best practices, and improving transplant outcomes

Allogeneic hematopoietic cell transplantation (HCT) is the only curative treatment for myelofibrosis (MF), and current guidelines recommend assessing all patients with MF for eligibility. Several patient- and disease-specific factors impact transplantation outcomes, and timely assessment of potential transplant candidates is key to optimizing post-HCT outcomes. The role of HCT in the treatment of MF continues to evolve, with the adoption of newer and safer approaches, enhanced donor availability, use of reduced-intensity conditioning, improvements in graft-versus-host disease (GVHD) prophylaxis and treatment, and greater understanding of high-risk clinical and molecular features of the disease. These developments highlight the importance of early and ongoing assessment throughout the MF disease course to optimize eligibility and consideration for HCT. Ruxolitinib is approved for first-line treatment of intermediate- or high-risk MF, and emerging data have clarified the important role of ruxolitinib in not only optimizing clinical status before HCT but also mitigating and treating post-HCT complications in patients with MF, notably acute and chronic GVHD and relapse. Here we review strategies for optimizing clinical outcomes in patients considered for and undergoing HCT for MF treated with ruxolitinib. We discuss strategies for appropriate patient and donor selection, optimization of ruxolitinib therapy in the pre- and peri-HCT periods, choice of conditioning regimen, GVHD prophylaxis, post-HCT management of GVHD, continued monitoring for MF relapse, and the role of post-HCT ruxolitinib maintenance to reduce risks of GVHD and disease relapse.

Managing Myelofibrosis: Matching Advances in Treatments With Clinical Unmet Needs

Myelofibrosis (MF) is characterized by anemia, constitutional symptoms, hepatosplenomegaly and bone marrow fibrosis, and is associated with poor survival. The janus kinase inhibitor (JAKi) ruxolitinib has been the mainstay of treatment for over a decade. Despite demonstrated symptomatic and quality of life improvement, unmet clinical needs persist. A literature review identified promising novel targeted treatment options in MF using pre-set selection criteria (available Phase 2 or 3 data, minimum enrollment of 50 patients, trial end date within the last 5 years). Available data for novel and approved therapies were extracted, tabulated, and analyzed for clinical relevancy. From an initial shortlist of 48, 16 retained molecules were selected for inclusion. Other JAKi (pacritinib, momelotinib, jaktinib) address treatment-related cytopenia, expanding the therapeutic utility of this class of agents to patients with baseline anemia or thrombocytopenia. Novel candidates exploit multiple molecular pathways, and offer the potential to improve the management of MF-associated cytopenia (imetelstat, pelabresib, navitoclax, selinexor, luspatercept, sotatercept, elritercept, LCL161, bomedemstat) and recover bone marrow fibrosis (imetelstat, pelabresib, navitoclax and bomedemstat). It remains to be seen if these newer agents can induce any remission in MF and enable patients to come off therapy, but the future is beginning to look much brighter.

Clinical and Immune Effects of Peri-Transplantation JAK Inhibition for Myelofibrosis

Despite the introduction of JAK inhibitors, allogeneic hematopoietic cell transplant remains the only potentially curative treatment for patients with myelofibrosis but has considerable treatment-related complications. Whether the incorporation of JAK inhibition into the transplant algorithm leads to improved outcomes is still unclear. Here, we analyzed different transplant platforms in myelofibrosis patients undergoing a first transplant, comparing immune profiles and outcomes of (1) 33 patients continuing JAK inhibition at start of conditioning until stable engraftment (PERI-group), (2) 38 patients receiving JAK inhibition prior to transplant until start of conditioning (PRE-group), and (3) 38 patients that had never received JAK inhibition (NON-group). Patients in the PERI-group showed significantly higher early B-cell recovery as well as significantly increased late recovery of gamma-delta T cells and NK cells. We observed excellent neutrophil and platelet engraftment (100% for both) in the PERI-group and no hematotoxic effects or increased rates of infections following peri-transplant JAK inhibition. Cumulative incidence of acute graft-versus-host disease (GvHD) grade II-IV at day 100 after transplant was 15% in the PERI-group versus 29% in the PRE-group versus 34% in the NON-group. Cumulative incidence of relapse at 1 year after transplant was 9% in the PERI-group compared with 16% in the PRE-group and 18% in the NON-group. In conclusion, peri-transplant JAK inhibition was feasible with promising engraftment and acute GvHD rates, though deserves further investigation.

Molecular profiling in MPN: who should have it and why?

Philadelphia chromosome-negative myeloproliferative neoplasms (MPNs) are a group of blood cancers that result from somatic mutations in hematopoietic stem cells, causing constitutive activation of JAK-STAT signaling pathways with consequent overproduction of 1 or more myeloid lineages. The initiating event in MPN pathogenesis is a genetic mutation, and consequently molecular profiling is central to the diagnosis, risk stratification, and, increasingly, monitoring of therapy response in persons with MPN. In this review we summarize current approaches to molecular profiling of classical MPNs (essential thrombocythemia, polycythemia vera, and myelofibrosis), using illustrative clinical case histories to demonstrate how genetic analysis is already fully integrated into MPN diagnostic classification and prognostic risk stratification. Molecular profiling can also be used in MPN to measure response to therapy both in clinical trials and increasingly in routine clinical practice. Taking a forward look, we discuss how molecular profiling in MPN might be used in the future to select specific molecularly targeted therapies and the role of additional genetic methodologies beyond mutation analysis.

Investigational drugs in early phase trials for myelofibrosis

INTRODUCTION

Myelofibrosis (MF) is a chronic myeloproliferative neoplasm characterized by bone marrow fibrosis, cytopenias, and organomegaly. Four JAK inhibitors are US-FDA approved for treatment of MF. While these drugs reduce symptom burden and spleen size to varying degrees, they do not affect the natural disease course or decrease the risk of leukemic transformation. Therefore, there is a strong need for newer therapies to further advance the field and improve the outcomes of MF. In this review, we cover novel therapies for MF currently in early stages of development.

AREAS COVERED

We present the latest data from early phase clinical trials in MF using drugs with diverse therapeutic mechanisms, including novel JAK-STAT pathway inhibitors, epigenetic therapies, antifibrotic agents, and immunotherapeutic strategies. Additionally, we cover drugs targeted toward anemia improvement in MF.

EXPERT OPINION

Numerous agents representing diverse drug classes are in clinical development for MF. While deeper and durable improvements in splenomegaly, symptoms, and anemia are the main clinical objectives, a number of putative biomarkers are being assessed as measures of potential 'disease modification.' Although JAK inhibitor monotherapy represents the current standard, it is hoped that JAK inhibitor-based rational combinations and driver mutation-specific therapies will soon usher in a new era.

A multicenter phase 2 clinical trial of low-dose subcutaneous decitabine in myelofibrosis

ABSTRACT

Myelofibrosis (MF) in the chronic phase is a challenging disease to treat, and conventional treatment options are geared toward symptom palliation. In this prospective, multicenter, phase 2 trial, 21 patients with MF (18 chronic phase, 2 accelerated phase, and 1 blast phase) were treated with a 10-day schedule of subcutaneous decitabine at 0.3 mg/kg per day. The overall response rate was 33% (95% confidence interval, 15-57), primarily manifested as an improvement in cytopenias. The median duration of response was 7 months (range, 3-44). A high International Prognostic Scoring System risk score, high baseline fetal hemoglobin level, and sustained decrease in circulating CD34+ cell counts were associated with response to decitabine. All patients experienced at least 1 grade 3/4 cytopenia. Nonhematologic toxicities were less frequent, with fatigue, anorexia, and hypocalcemia being the most common. Given the lack of effective therapies in MF with severe cytopenias, this study supports further investigation into the use of hypomethylating agents as single agents or in combination therapies. This trial was registered at www.ClinicalTrials.gov as #NCT00095784.

Polycythemia vera: past, present and future

There has been remarkable progress in the development of novel therapeutic approaches for patients with polycythemia vera (PV). Historically, therapy goals in PV were to mitigate thrombotic risks and control blood counts and symptoms. There is now increased focus on disease modification through progressive attrition of JAK2-mutant stem/progenitor cells. The approval of ropeginterferon, a novel monoPEGylated interferon, coupled with findings from LOW-PV and longer-term data from CONTINUATION-PV that strongly support a disease-modifying effect for interferon therapy, have transformed the treatment paradigm for this disorder. Results from MAJIC-PV demonstrate that disease modification can also be induced with JAK inhibitors, suggesting an urgent need to incorporate prospective molecular monitoring into PV trials. Novel agents, such as hepcidin mimetics, aim to help patients with PV restore normal hematocrit levels and become phlebotomy-free. In this review, we will summarize past, current and future approaches to PV management and highlight findings from key clinical studies.

Consistency of Spleen and Symptom Reduction Regardless of Cytopenia in Patients With Myelofibrosis Treated With Pacritinib

BACKGROUND

Pacritinib is a JAK2/IRAK1/ACVR1 inhibitor that is approved in the United States for the treatment of patients with myelofibrosis who have a platelet count < 50 × 109/L. Phase 3 clinical studies of pacritinib included patients across a wide range of baseline platelet and hemoglobin levels.

PATIENTS AND METHODS

In order to assess the impact of baseline blood counts on pacritinib efficacy, an analysis of efficacy outcomes by baseline platelet and hemoglobin levels was performed using data pooled from 2 Phase 3 studies of pacritinib in patients with MF (PERSIST-1 and PERSIST-2).

RESULTS

Of 276 patients evaluable for spleen response, spleen volume reduction occurred consistently across platelet subgroups (< 100 × 109/L or ≥ 100 × 109/L) and hemoglobin subgroups (< 8 g/dL, ≥ 8 to < 10 g/dL, or > 10 g/dL), with no diminution in treatment effect in patients with severe thrombocytopenia or anemia. Among 159 patients evaluable for symptoms response, improvement in total symptom score (TTS) was similar across platelet subgroups. A ≥ 50% improvement of TSS occurred more frequently in patients with baseline hemoglobin < 8 g/dL compared with those with baseline hemoglobin ≥ 8 to < 10 g/dL or > 10 g/dL. Patients with baseline hemoglobin < 8 g/dL also experienced improved hemoglobin sustained over 24 weeks, whereas subgroups with less severe anemia had stable hemoglobin levels over time. Symptom improvement as assessed using the Patient Global Impression of Change instrument was generally consistent across platelet and hemoglobin subgroups.

CONCLUSION

Pacritinib demonstrates consistent efficacy in patients with MF regardless of baseline platelet and hemoglobin counts.

Prognostic and Predictive Models in Myelofibrosis

PURPOSE OF REVIEW

Myelofibrosis (MF) includes prefibrotic primary MF (pre-PMF), overt-PMF and secondary MF (SMF). Median overall survival (OS) of pre-PMF, overt-PMF and SMF patients is around 14 years, seven and nine years, respectively. Main causes of mortality are non-clonal progression and transformation into blast phase.

RECENT FINDINGS

Discoveries on the impact of the biological architecture on OS have led to the design of integrated scores to predict survival in PMF. For SMF, OS estimates should be calculated by the specific MYSEC-PM (MYelofibrosis SECondary-prognostic model). Information on the prognostic role of the molecular landscape in SMF is accumulating. Crucial treatment decisions for MF patients could be now supported by multivariable predictive algorithms. OS should become a relevant endpoint of clinical trials. Prognostic models guide prediction of OS and treatment planning in MF, therefore, their timely application is critical in the personalized approach of MF patients.

SOHO State of the Art Updates and Next Questions | Early Intervention in Myelofibrosis: Where Are We and Does It Matter?

Historically, therapeutic clinical trials in myelofibrosis have predominantly focused on targeting patients with higher-risk disease who are at risk of increased morbidity and mortality. The endpoints have been designed to target regularly measured disease parameters that are of immediate pertinence to patient's welfare including splenic volume reduction and symptom reduction. These efforts have resulted in meaningful and measurable improvements in disease parameters in these high-risk study populations and multiple FDA approved agents. However, they have not tackled specific interventions that may be applied to patients with earlier or less advanced disease state. In this review, we summarize evidence from completed and ongoing clinical trials investigating different aspects of intervention targeted at less advanced disease and advocate for the merit of this approach.

Myeloproliferative neoplasms in the adolescent and young adult population: A comprehensive review of the literature

Myeloproliferative neoplasms (MPN) are characterized by a clonal proliferation of myeloid lineage cells within the bone marrow. The classical BCR-ABL negative MPNs are comprised of polycythaemia vera, essential thrombocythaemia and primary myelofibrosis. Historically, the majority of MPNs are diagnosed in adults older than 60 years of age; however, in recent years, there has been recognition of MPNs in the adolescent and young adult (AYA) population. AYAs with MPN, typically defined as between the ages of 15 and 39 years old, may comprise up to 20% of patients diagnosed with MPN. They demonstrate unique patterns of driver mutations and thrombotic events and remain at risk for progression to more aggressive disease states. Given the likely long length of time they will live with their disease, there is a significant unmet need in identifying well-tolerated and effective treatment options for these patients, particularly with the advent of disease modification. In this review, we provide a comprehensive overview of the clinical features, disease course and management of AYA patients with MPN and, in doing so, highlight key characteristics that distinguish them from their older counterparts.

Myelofibrosis: Current unmet needs, emerging treatments, and future perspectives

The current standard-of-care for treatment of myelofibrosis (MF) comprises inhibitors of the Janus kinase (JAK)/signal transducers and activators (STAT) pathway; however, despite their ability to alleviate symptoms, they do not appear to modify underlying disease and have not demonstrated substantial survival benefit. Allogeneic-hematopoietic stem cell transplantation remains the only curative option for patients with MF but is limited to a subset of high-risk and fit patients. Early disease modification could positively affect disease trajectory for lower risk patients with MF as well as those with conditions that can precede MF, such as polycythemia vera and essential thrombocythemia. Here, the authors discuss critical unmet needs in the MF treatment paradigm, including: the need for safe, impactful therapies for lower risk patients, thus allowing intervention when success is most likely; better development of first-line therapies (likely highly novel or combination strategies) for intermediate-risk/higher risk patients; and approved drugs to manage cytopenia. Finally, a consensus definition of disease modification is needed that informs trial design, allowing the development of clinical end points that enable understanding of therapies and responses and that facilitate the development of therapies that work according to this definition. Through close collaboration between clinicians, patients, and the pharmaceutical industry, better efforts to define benefit and identify patients most likely to benefit from a particular combination or treatment strategy should enable the development of more effective and safe treatments to extend and improve quality of life for patients with MF.

Quantitative MRI reveals heterogeneous impacts of treatment on diseased bone marrow in a mouse model of myelofibrosis

PURPOSE

Analyzing bone marrow in the hematologic cancer myelofibrosis requires endpoint histology in mouse models and bone marrow biopsies in patients. These methods hinder the ability to monitor therapy over time. Preclinical studies typically begin treatment before mice develop myelofibrosis, unlike patients who begin therapy only after onset of disease. Using clinically relevant, quantitative MRI metrics allowed us to evaluate treatment in mice with established myelofibrosis.

METHODS

We used chemical shift-encoded fat imaging, DWI, and magnetization transfer sequences to quantify bone marrow fat, cellularity, and macromolecular components in a mouse model of myelofibrosis. We monitored spleen volume, the established imaging marker for treatment, with anatomic MRI. After confirming bone marrow disease by MRI, we randomized mice to treatment with an approved drug (ruxolitinib or fedratinib) or an investigational agent, navitoclax, for 33 days. We measured the effects of therapy over time with bone marrow and spleen MRI.

RESULTS

All treatments produced heterogeneous responses with improvements in bone marrow evident in subsets of individual mice in all treatment groups. Reductions in spleen volume commonly occurred without corresponding improvement in bone marrow. MRI revealed patterns associated with effective and ineffective responses to treatment in bone marrow and identified regional variations in efficacy within a bone.

CONCLUSIONS

Quantitative MRI revealed modest, heterogeneous improvements in bone marrow disease when treating mice with established myelofibrosis. These results emphasize the value of bone marrow MRI to assess treatment in preclinical models and the potential to advance clinical trials for patients.

Results from phase 1 of the MANIFEST clinical trial to evaluate the safety and tolerability of pelabresib in patients with myeloid malignancies

Pelabresib (CPI-0610), a BET protein inhibitor, is in clinical development for hematologic malignancies, given its ability to target NF-κB gene expression. The MANIFEST phase 1 study assessed pelabresib in patients with acute leukemia, high-risk myelodysplastic (MDS) syndrome, or MDS/myeloproliferative neoplasms (MDS/MPNs) (NCT02158858). Forty-four patients received pelabresib orally once daily (QD) at various doses (24-400 mg capsule or 225-275 mg tablet) on cycles of 14 d on and 7 d off. The most frequent drug-related adverse events were nausea, decreased appetite, and fatigue. The maximum tolerated dose (MTD) was 225 mg tablet QD. One patient with chronic myelomonocytic leukemia (CMML) showed partial remission. In total, 25.8% of acute myeloid leukemia (AML) patients and 38.5% of high-risk MDS patients had stable disease. One AML patient and one CMML patient showed peripheral hematologic response. The favorable safety profile supports the ongoing pivotal study of pelabresib in patients with myelofibrosis using the recommended phase 2 dose of 125 mg tablet QD.CLINICAL TRIAL REGISTRATION: NCT02158858.

Exploring the molecular mechanisms between lymphoma and myelofibrosis

Lymphoma is a heterogeneous malignant tumor with an increasing annual incidence. As the lymphoma progresses, bone marrow (BM) invasion gradually appears. Myelofibrosis (MF) can accompany a variety of hematological malignancies, including lymphoma, and multiple myeloma. The prognosis of lymphoma patients with myelofibrosis is poor, and a fundamental reason is that there are few studies on the correlation and pathogenesis of the two diseases. In this review, we examine the potential pathogenesis and the correlation of the two diseases.

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.

Evolving landscape of JAK inhibition in myelofibrosis: monotherapy and combinations

Myeloproliferative neoplasms (MPNs) are characterized by clonal myeloproliferation in 1 or more of the hematopoietic stem cell lineages. Primary myelofibrosis (MF), post-polycythemia vera MF, and post-essential thrombocythemia MF have the worst prognosis and are characterized by the presence of cytokine-mediated symptom complex, splenomegaly, progressive marrow failure, and clonal instability, leading to leukemic transformation. The key therapeutic aims encompass the management of symptoms, splenomegaly, and anemia and the improvement of survivals. These therapeutic aims have evolved with the availability of Jak inhibitors and novel agents, making disease modification potentially achievable. Novel agents may potentially target MPN stem cells, epigenetic alterations, signaling pathways, and apoptotic pathways. In this case-based review, we outline our approach to the management of MF and discuss the therapeutic landscape of MF, highlighting the utility of Jak inhibitors and novel Jak inhibitor-based combinations.

Moving toward disease modification in polycythemia vera

Polycythemia vera (PV) belongs to the BCR-ABL1-negative myeloproliferative neoplasms and is characterized by activating mutations in JAK2 and clinically presents with erythrocytosis, variable degrees of systemic and vasomotor symptoms, and an increased risk of both thromboembolic events and progression to myelofibrosis and acute myeloid leukemia (AML). Treatment selection is based on a patient's age and a history of thrombosis in patients with low-risk PV treated with therapeutic phlebotomy and aspirin alone, whereas cytoreductive therapy with either hydroxyurea or interferon alfa (IFN-α) is added for high-risk disease. However, other disease features such as significant disease-related symptoms and splenomegaly, concurrent thrombocytosis and leukocytosis, or intolerance of phlebotomy can constitute an indication for cytoreductive therapy in patients with otherwise low-risk disease. Additionally, recent studies demonstrating the safety and efficacy (ie, reduction in phlebotomy requirements and molecular responses) of ropegylated IFN-α2b support its use for patients with low-risk PV. Additionally, emerging data suggest that early treatment is associated with higher rates of molecular responses, which might eventually enable time-limited therapy. Nonetheless, longer follow-up is needed to assess whether molecular responses associate with clinically meaningful outcome measures such as thrombosis and progression to myelofibrosis or AML. In this article, we provide an overview of the current and evolving treatment landscape of PV and outline our vision for a patient-centered, phlebotomy-free, treatment approach using time-limited, disease-modifying treatment modalities early in the disease course, which could ultimately affect the natural history of the disease.

New era for myelofibrosis treatment with novel agents beyond Janus kinase-inhibitor monotherapy: Focus on clinical development of BCL-XL /BCL-2 inhibition with navitoclax

Myelofibrosis is a heterogeneous myeloproliferative neoplasm characterized by chronic inflammation, progressive bone marrow failure, and hepatosplenic extramedullary hematopoiesis. Treatments like Janus kinase inhibitor monotherapy (e.g., ruxolitinib) provide significant spleen and symptom relief but demonstrate limited ability to lead to a durable disease modification. There is an urgent unmet medical need for treatments with a novel mechanism of action that can modify the underlying pathophysiology and affect the disease course of myelofibrosis. This review highlights the role of B-cell lymphoma (BCL) protein BCL-extra large (BCL-XL ) in disease pathogenesis and the potential role that navitoclax, a BCL-extra large/BCL-2 inhibitor, may have in myelofibrosis treatment.

Quantitative interpretation of bone marrow biopsies in MPN-What's the point in a molecular age?

The diagnosis of myeloproliferative neoplasms (MPN) requires the integration of clinical, morphological, genetic and immunophenotypic findings. Recently, there has been a transformation in our understanding of the cellular and molecular mechanisms underlying disease initiation and progression in MPN. This has been accompanied by the widespread application of high-resolution quantitative molecular techniques. By contrast, microscopic interpretation of bone marrow biopsies by haematologists/haematopathologists remains subjective and qualitative. However, advances in tissue image analysis and artificial intelligence (AI) promise to transform haematopathology. Pioneering studies in bone marrow image analysis offer to refine our understanding of the boundaries between reactive samples and MPN subtypes and better capture the morphological correlates of high-risk disease. They also demonstrate potential to improve the evaluation of current and novel therapeutics for MPN and other blood cancers. With increased therapeutic targeting of diverse molecular, cellular and extra-cellular components of the marrow, these approaches can address the unmet need for improved objective and quantitative measures of disease modification in the context of clinical trials. This review focuses on the state-of-the-art in image analysis/AI of bone marrow tissue, with an emphasis on its potential to complement and inform future clinical studies and research in MPN.

A Prognostic Model to Predict Ruxolitinib Discontinuation and Death in Patients with Myelofibrosis

Most patients with myelofibrosis (MF) discontinue ruxolitinib (JAK1/JAK2 inhibitor) in the first 5 years of therapy due to therapy failure. As the therapeutic possibilities of MF are expanding, it is critical to identify patients predisposed to early ruxolitinib monotherapy failure and worse outcomes. We investigated predictors of early ruxolitinib discontinuation and death on therapy in 889 patients included in the "RUX-MF" retrospective study. Overall, 172 patients were alive on ruxolitinib after ≥5 years (long-term ruxolitinib, LTR), 115 patients were alive but off ruxolitinib after ≥5 yrs (short-term RUX, STR), and 123 patients died while on ruxolitinib after <5 yrs (early death on ruxolitinib, EDR). The cumulative incidence of the blast phase was similar in LTR and STR patients (p = 0.08). Overall survival (OS) was significantly longer in LTR pts (p = 0.002). In multivariate analysis, PLT < 100 × 109/L, Hb < 10 g/dL, primary MF, absence of spleen response at 3 months and ruxolitinib starting dose <10 mg BID were associated with higher probability of STR. Assigning one point to each significant variable, a prognostic model for STR (STR-PM) was built, and three groups were identified: low (score 0-1), intermediate (score 2), and high risk (score ≥ 3). The STR-PM may identify patients at higher risk of failure with ruxolitinib monotherapy who should be considered for alternative frontline strategies.

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.

Recent advances in therapies for primary myelofibrosis

Primary myelofibrosis (PMF), polycythemia vera (PV) and essential thrombocythemia (ET) form the classical BCR-ABL1-negative myeloproliferative neoplasms (MPNs) that are driven by a constitutive activation of JAK2 signaling. PMF as well as secondary MF (post-ET and post-PV MF) are the most aggressive MPNs. Presently, there is no curative treatment, except allogenic hematopoietic stem cell transplantation. JAK inhibitors, essentially ruxolitinib, are the therapy of reference for intermediate and high-risk MF. However, presently the current JAK inhibitors behave mainly as anti-inflammatory drugs, improving general symptoms and spleen size without major impact on disease progression. A better understanding of the genetics of MF, the biology of its leukemic stem cells (LSCs), the mechanisms of fibrosis and of cytopenia and the role of inflammatory cytokines has led to new approaches with the development of numerous therapeutic agents that target epigenetic regulation, telomerase, apoptosis, cell cycle, cytokines and signaling. Furthermore, the use of a new less toxic form of interferon-α has been revived, as it is presently one of the only molecules that targets the mutated clone. These new approaches have different aims: (a) to provide alternative therapy to JAK inhibition; (b) to correct cytopenia; and (c) to inhibit fibrosis development. However, the main important goal is to find new disease modifier treatments, which will profoundly modify the progression of the disease without major toxicity. Presently the most promising approaches consist of the inhibition of telomerase and the combination of JAK2 inhibitors (ruxolitinib) with either a BCL2/BCL-xL or BET inhibitor. Yet, the most straightforward future approaches can be considered to be the development of and/or selective inhibition of JAK2V617F and the targeting MPL and calreticulin mutants by immunotherapy. It can be expected that the therapy of MF will be significantly improved in the coming years.

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.

Emerging Treatment Options for Myelofibrosis: Focus on Anemia

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

Morphology of myeloproliferative neoplasms

Myeloproliferative neoplasms (MPN) are a group of clonal haematological malignancies first described by Dameshek in 1957. The Philadelphia-negative MPN that will be described are polycythaemia vera (PV), essential thrombocythaemia (ET), pre-fibrotic myelofibrosis and primary myelofibrosis (PMF). The blood and bone marrow morphology are essential in diagnosis, for WHO classification, establishing a baseline, monitoring response to treatment and identifying changes that may indicate disease progression. The blood film changes may be in any of the cellular elements. The key bone marrow features are architecture and cellularity, relative complement of individual cell types, reticulin content and bony structure. Megakaryocytes are the most abnormal cell and key to classification, as their number, location, size and cytology are all disease-defining. Reticulin content and grade are integral to assignment of the diagnosis of myelofibrosis. Even with careful assessment of all these features, not all cases fit neatly into the diagnostic entities; there is frequent overlap reflecting the biological disease continuum rather than distinct entities. Notwithstanding this, an accurate morphologic diagnosis in MPN is crucial due to the significant differences in prognosis between different subtypes and the availability of different therapies in the era of novel agents. The distinction between "reactive" and MPN is also not always straightforward and caution needs to be exercised given the prevalence of "triple negative" MPN. Here we describe the morphology of MPN including comments on changes with disease evolution and with treatment.

Moving Beyond Ruxolitinib Failure in Myelofibrosis: Evolving Strategies for Second Line Therapy

Ruxolitinib has been the cornerstone of pharmacologic therapy for myelofibrosis for over a decade. However, the last several years have witnessed the regulatory approval of other Janus kinase (JAK) inhibitors for myelofibrosis, i.e. fedratinib, pacritinib, and US approval of momelotinib is widely anticipated in 2023. Due to the multifaceted clinical presentation of myelofibrosis, a watertight definition of ruxolitinib failure has remained elusive, as "progression" on ruxolitinib can take many forms and management is highly nuanced. Yet, the availability of other JAK inhibitors and potential future availability of non-JAK inhibitor agents for myelofibrosis make a consensus on management of ruxolitinib failure critically important. This consensus paper summarizes a discussion between multiple academic and community physician experts, a pharmacist and an advanced practice provider around the issues to be considered for the optimal care of patients with myelofibrosis whose disease is refractory to or does not respond adequately to ruxolitinib, or who exhibit intolerance to ruxolitinib. The panel identified several areas of consensus, as well as some areas where more data to inform evidence-based practice are needed. In some situations, maintaining ruxolitinib while adding another agent, e.g. to address anemia, is appropriate, whereas in others, switching to a different drug has merit.

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.

Biology and therapeutic targeting of molecular mechanisms in MPNs

Myeloproliferative neoplasms (MPNs) are clonal hematopoietic stem cell disorders characterized by activated Janus kinase (JAK)-signal transducer and activator of transcription signaling. As a result, JAK inhibitors have been the standard therapy for treatment of patients with myelofibrosis (MF). Although currently approved JAK inhibitors successfully ameliorate MPN-related symptoms, they are not known to substantially alter the MF disease course. Similarly, in essential thrombocythemia and polycythemia vera, treatments are primarily aimed at reducing the risk of cardiovascular and thromboembolic complications, with a watchful waiting approach often used in patients who are considered to be at a lower risk for thrombosis. However, better understanding of MPN biology has led to the development of rationally designed therapies, with the goal of not only addressing disease complications but also potentially modifying disease course. We review the most recent data elucidating mechanisms of disease pathogenesis and highlight emerging therapies that target MPN on several biologic levels, including JAK2-mutant MPN stem cells, JAK and non-JAK signaling pathways, mutant calreticulin, and the inflammatory bone marrow microenvironment.

Myelofibrosis

The clinical phenotype of primary and post-polycythemia vera and postessential thrombocythemia myelofibrosis (MF) is dominated by splenomegaly, symptomatology, a variety of blood cell alterations, and a tendency to develop vascular complications and blast phase. Diagnosis requires assessing complete cell blood counts, bone marrow morphology, deep genetic evaluations, and disease history. Driver molecular events consist of JAK2V617F, CALR, and MPL mutations, whereas about 8% to 10% of MF are "triple-negative." Additional myeloid-gene variants are described in roughly 80% of patients. Currently available clinical-based and integrated clinical/molecular-based scoring systems predict the survival of patients with MF and are applied for conventional treatment decision-making, indication to stem cell transplant (SCT) and allocation in clinical trials. Standard treatment consists of anemia-oriented therapies, hydroxyurea, and JAK inhibitors such as ruxolitinib, fedratinib, and pacritinib. Overall, spleen volume reduction of 35% or greater at week 24 can be achieved by 42% of ruxolitinib-, 47% of fedratinib-, 19% of pacritinib-, and 27% of momelotinib-treated patients. Now, it is time to move towards new paradigms for evaluating efficacy like disease modification, that we intend as a robust and unequivocal effect on disease biology and/or on patient survival. The growing number of clinical trials potentially pave the way for new strategies in patients with MF. Translational studies of some molecules showed an early effect on bone marrow fibrosis and on variant allele frequencies of myeloid genes. SCT is still the only curative option, however, it is associated with relevant challenges. This review focuses on the diagnosis, prognostication, and treatment of MF.

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.

JAK inhibition in myelofibrosis: how to sequence treatment in this new era of multiple options

The management of myelofibrosis has improved following approval of the JAK1/JAK2 inhibitor, ruxolitinib. This agent laid the foundation for JAK inhibitor therapy, yet limitations have included myelosuppression and other adverse events (skin cancer, weight gain, and infection), as well as loss of response. Recently, two additional JAK inhibitors were approved for use in myelofibrosis. Fedratinib can be used front-line and has demonstrated impressive responses as a salvage option after ruxolitinib loss of response. Previously, patients with severe thrombocytopenia had limited treatment options; approval of pacritinib offers an option to address splenomegaly and/or symptoms in these patients. A significant unmet need has been the treatment of anemia; momelotinib (not approved at the time of writing) has demonstrated spleen, symptom, and anemia responses. The possibility of having four approved options for myelofibrosis may be soon realized. This speaks to progress in the past decade, though achieving clinical and molecular remissions remain paramount.

Targeted Therapy for MPNs: Going Beyond JAK Inhibitors

PURPOSE OF REVIEW

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

RECENT FINDINGS

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

Towards a Personalized Definition of Prognosis in Philadelphia-Negative Myeloproliferative Neoplasms

Purpose of Review

Philadelphia-negative myeloproliferative neoplasms (MPNs) include polycythemia vera (PV), essential thrombocythemia (ET), prefibrotic (pre-), and overt-primary myelofibrosis (primary MF, PMF). PV and ET could evolve into secondary MF (SMF), whose early diagnosis relies on monitoring signs of possible progression. All MPNs have a risk of blast phase (BP), that is associated with a very dismal outcome. Overall survival (OS) is different among MPNs, and disease-specific prognostic scores should be applied for a correct clinical management. In this review, an overview of current prognostic scores in MPNs will be provided.

Recent Findings

The biological complexity of MPNs and its role on the trajectory of disease outcome have led to the design of integrated prognostic models that are nowadays of common use in PMF patients. As for PV and ET, splicing gene mutations could have a detrimental role, but with the limit of the not routinary recommended application of extensive molecular analysis in these diseases. SMF is recognized as a distinct entity compared to PMF, and OS estimates should be calculated by the MYSEC-PM (Myelofibrosis SECondary-prognostic model). Both in PMF and SMF, decisions as selection of patients potentially candidates to allogenic stem cell transplant or that could benefit from an early shift from standard treatment are based not only on conventional prognostic scores, but also on multivariable algorithms.

Summary

The expanding landscape of risk prediction for OS, evolution to BP, and SMF progression from PV/ET informs personalized approach to the management of patients affected by MPNs.