Momelotinib inhibits ACVR1/ALK2, decreases hepcidin production, and ameliorates anemia of chronic disease in rodents

Pharmacotherapeutic advances for splenomegaly in myelofibrosis

INTRODUCTION

Myelofibrosis is a hematologic malignancy with a variety of clinical manifestations including splenomegaly, which is present in approximately 80% of newly diagnosed patients. JAK inhibitors are the mainstay of pharmacologic treatment for splenomegaly in myelofibrosis, although spleen size reduction is not universal, and the duration of benefit is only moderately durable.

AREAS COVERED

We first discuss the pathobiology of splenomegaly in myelofibrosis before detailing approved and novel pharmacotherapies that can reduce spleen size while also highlighting non-pharmacologic approaches. In this review, efficacy of these treatments is measured solely by spleen volume reduction, acknowledging that other outcome measures such as symptom improvement and survival are also critical.

EXPERT OPINION

Currently, ruxolitinib can be administered to the majority of frontline patients although those with severe thrombocytopenia should receive pacritinib to address spleen burden. Momelotinib may be particularly well suited for patients with significant anemia and novel combination treatments in clinical development may improve the depth and duration of spleen responses. After frontline treatment failure, fedratinib, or pacritinib are commercial options for patients with persistent symptomatic splenomegaly. Novel agents given alone or in combination with a JAK inhibitor are being explored in trials, which may ameliorate splenomegaly and ultimately improve disease progression.

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.

Predictors of anemia response to momelotinib therapy in myelofibrosis and impact on survival

We retrospectively reviewed 72 anemic patients with myelofibrosis (MF; median age 68 years), who were JAK2 inhibitor-naïve at the time of study entry to a phase-1/2 momelotinib clinical trial. Driver mutation profile included JAK2 69%, CALR 17%, MPL 8%, and triple-negative 6%; other mutations included ASXL1 39% and SRSF2 17%. Momelotinib was administered at a median dose of 300 mg daily. Anemia response was assessed by formal criteria and documented in 44% of all patients with hemoglobin levels below the sex-adjusted reference range (n = 72), 48% of those with hemoglobin <10 g/dl (n = 54), and 46% of those who were transfusion-dependent at the time of study entry (n = 28). Anemia response was more likely with post-essential thrombocythemia MF (83% vs 37%; p = .001), lower serum ferritin (p = .003), and shorter time from diagnosis to momelotinib therapy (p = .001); the first two variables were also predictive in transfusion-dependent patients. Post-momelotinib median survival was 3.2 years; in univariate analysis, survival was superior in anemia responders (median 3.8 vs. 2.8 years; p = .14) and in the presence of type 1/like CALR mutation and inferior in the presence of age > 65 years, ASXL1/SRSF2 mutation, unfavorable karyotype, DIPSS-plus high risk, red cell transfusion need and higher serum ferritin. Multivariable analysis confirmed the favorable impact of anemia response on survival (p = .02; HR 0.5, 3/5/10-year survival; 69%/38%/25%). This survival advantage was also noted in transfusion-dependent patients (3.7 vs. 1.9 years; p = .01; HR 0.3) and appeared to be restricted to patients with an unfavorable genetic profile. The current study suggests a short-term survival benefit associated with anemia response in momelotinib-treated patients with MF.

New Treatments for Myelofibrosis

OPINION STATEMENT

Currently approved therapies for myelofibrosis (MF) consist of JAK inhibitors, which produce meaningful improvements in spleen size and symptom burden but do not significantly impact leukemic progression. In addition, many patients develop resistance or intolerance to existing therapies and are left without meaningful therapeutic options. There has been recent rapid development of agents in MF that may be able to fill these unmet needs. Importantly, most treatments currently in clinical development have targets outside the JAK-STAT pathway, including BET, BCL-2/BCL-xL, PI3k, HDM2, PIM-1, SINE, telomerase, LSD1, and CD123. These therapies are being tested in combination with JAK inhibitors in the front-line setting and in patients with a suboptimal response, as well as a single agent after JAK inhibitor failure. This next generation of agents is likely to produce a paradigm shift in MF treatment with a focus on combination treatment targeting multiple areas of MF pathophysiology.

Momelotinib versus danazol in symptomatic patients with anaemia and myelofibrosis (MOMENTUM): results from an international, double-blind, randomised, controlled, phase 3 study

BACKGROUND

Janus kinase (JAK) inhibitors approved for myelofibrosis provide spleen and symptom improvements but do not meaningfully improve anaemia. Momelotinib, a first-in-class inhibitor of activin A receptor type 1 as well as JAK1 and JAK2, has shown symptom, spleen, and anaemia benefits in myelofibrosis. We aimed to confirm the differentiated clinical benefits of momelotinib versus the active comparator danazol in JAK-inhibitor-exposed, symptomatic patients with anaemia and intermediate-risk or high-risk myelofibrosis.

METHODS

MOMENTUM is an international, double-blind, randomised, controlled, phase 3 study that enrolled patients at 107 sites across 21 countries worldwide. Eligible patients were 18 years or older with a confirmed diagnosis of primary myelofibrosis or post-polycythaemia vera or post-essential thrombocythaemia myelofibrosis. Patients were randomly assigned (2:1) to receive momelotinib (200 mg orally once per day) plus danazol placebo (ie, the momelotinib group) or danazol (300 mg orally twice per day) plus momelotinib placebo (ie, the danazol group), stratified by total symptom score (TSS; <22 vs ≥22), spleen size (<12 cm vs ≥12 cm), red blood cell or whole blood units transfused in the 8 weeks before randomisation (0 units vs 1-4 units vs ≥5 units), and study site. The primary endpoint was the Myelofibrosis Symptom Assessment Form (MFSAF) TSS response rate at week 24 (defined as ≥50% reduction in mean MFSAF TSS over the 28 days immediately before the end of week 24 compared with baseline). MOMENTUM is registered with ClinicalTrials.gov, number NCT04173494, and is active but not recruiting.

FINDINGS

195 patients were randomly assigned to either the momelotinib group (130 [67%]) or danazol group (65 [33%]) and received study treatment in the 24-week randomised treatment period between April 24, 2020, and Dec 3, 2021. A significantly greater proportion of patients in the momelotinib group reported a 50% or more reduction in TSS than in the danazol group (32 [25%] of 130 vs six [9%] of 65; proportion difference 16% [95% CI 6-26], p=0·0095). The most frequent grade 3 or higher treatment-emergent adverse events with momelotinib and danazol were haematological abnormalities by laboratory values: anaemia (79 [61%] of 130 vs 49 [75%] of 65) and thrombocytopenia (36 [28%] vs 17 [26%]). The most frequent non-haematological grade 3 or higher treatment-emergent adverse events with momelotinib and danazol were acute kidney injury (four [3%] of 130 vs six [9%] of 65) and pneumonia (three [2%] vs six [9%]).

INTERPRETATION

Treatment with momelotinib, compared with danazol, resulted in clinically significant improvements in myelofibrosis-associated symptoms, anaemia measures, and spleen response, with favourable safety. These findings support the future use of momelotinib as an effective treatment in patients with myelofibrosis, especially in those with anaemia.

FUNDING

Sierra Oncology.

New approaches to tackle cytopenic myelofibrosis

Myelofibrosis (MF) is a clonal hematopoietic stem cell neoplasm characterized by constitutional symptoms, splenomegaly, and risks of marrow failure or leukemic transformation and is universally driven by Jak/STAT pathway activation. Despite sharing this pathogenic feature, MF disease behavior can vary widely. MF can generally be categorized into 2 distinct subgroups based on clinical phenotype: proliferative MF and cytopenic (myelodepletive) MF. Compared to proliferative phenotypes, cytopenic MF is characterized by lower blood counts (specifically anemia and thrombocytopenia), more frequent additional somatic mutations outside the Jak/STAT pathway, and a worse prognosis. Cytopenic MF presents unique therapeutic challenges. The first approved Jak inhibitors, ruxolitinib and fedratinib, can both improve constitutional symptoms and splenomegaly but carry on-target risks of worsening anemia and thrombocytopenia, limiting their use in patients with cytopenic MF. Supportive care measures that aim to improve anemia or thrombocytopenia are often ineffective. Fortunately, new treatment strategies for cytopenic MF are on the horizon. Pacritinib, selective Jak2 inhibitor, was approved in 2022 to treat patients with symptomatic MF and a platelet count lower than 50 × 109/L. Several other Jak inhibitors are in development to extend therapeutic benefits to those with either anemia or thrombocytopenia. While many other novel non-Jak inhibitor therapies are in development for MF, most carry a risk of hematologic toxicities and often exclude patients with baseline thrombocytopenia. As a result, significant unmet needs remain for cytopenic MF. Here, we discuss clinical implications of the cytopenic MF phenotype and present existing and future strategies to tackle this challenging disease.

Long-Term Efficacy and Safety of Luspatercept for Anemia Treatment in Patients With Lower-Risk Myelodysplastic Syndromes: The Phase II PACE-MDS Study

Clinical trials frequently include multiple end points that mature at different times. The initial report, typically based on the primary end point, may be published when key planned co-primary or secondary analyses are not yet available. Clinical Trial Updates provide an opportunity to disseminate additional results from studies, published in JCO or elsewhere, for which the primary end point has already been reported.Luspatercept has high clinical activity in patients with transfusion-dependent lower-risk myelodysplastic syndromes (LR-MDS) and ring sideroblasts (RS) relapsed or refractory to erythropoietin. We report long-term luspatercept safety and efficacy in 108 patients with LR-MDS in the PACE-MDS study, including 44 non-RS and 34 non-transfusion-dependent or previously untreated patients. The primary end point was safety. Secondary end points included rates of hematologic improvement (HI) erythroid (HI-E), HI neutrophil, and HI platelet. Exploratory end points included erythropoiesis biomarker quantitation and mutation data. Median duration of luspatercept exposure was 315 days (range, 21-1,934 days). No new safety signals emerged. HI-E was observed in 53.7% of patients, including 36.4% of non-RS and 70.6% of non-transfusion-dependent patients. HI neutrophil and HI platelet were observed in 33.3% and 9.5% of patients, respectively. An almost three-fold increase in bone marrow late to early progenitor cell ratio accompanied HI-E response, irrespective of RS status. Lower baseline erythropoietin levels in non-RS patients (69.6 v 623.3 IU/L; P = .0077) and higher late to early erythroid progenitor cell ratio (10.44 v 4.48; P = .0106) in RS patients were associated with HI-E. This study highlights luspatercept's effects across LR-MDS subtypes, including untreated MDS-RS, serving as a platform for future trials.

Novel Therapies in Myelofibrosis: Beyond JAK Inhibitors

PURPOSE OF REVIEW

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

RECENT FINDINGS

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

Pacritinib for the treatment of patients with myelofibrosis and thrombocytopenia

INTRODUCTION

: Myelofibrosis (MF) is a rare myeloproliferative neoplasm characterized by a complex symptom profile, cytopenias, splenomegaly, and potential for leukemic progression. Severe thrombocytopenia is common in patients with MF and correlates with poor prognosis; however, until recently, treatment options for these patients were limited. Pacritinib, a potent Janus kinase (JAK) 2/interleukin-1 receptor-associated kinase 1 (IRAK1) inhibitor, has demonstrated significant reduction in splenomegaly, improved symptom control, and a manageable safety profile in patients with MF regardless of the severity of thrombocytopenia.

AREAS COVERED

: This review will outline the pacritinib drug profile and summarize key efficacy and safety data, focusing on the 200 mg twice daily dose from phase 2 and 3 studies that formed the basis for the recent US Food and Drug Administration approval of pacritinib in patients with MF and severe thrombocytopenia (platelet counts <50 x 10⁹/L).

EXPERT OPINION

Pacritinib, with its unique mechanism of action targeting both JAK2 and IRAK1, offers patients with MF and severe thrombocytopenia a new treatment option, providing consistent disease and symptom control. Adverse events are easily manageable. Further analyses to identify ideal patient characteristics for pacritinib and other JAK inhibitors along with studies of pacritinib combinations are warranted, including in related myeloid malignancies.

Overall survival in the SIMPLIFY-1 and SIMPLIFY-2 phase 3 trials of momelotinib in patients with myelofibrosis

Janus kinase inhibitors (JAKi) approved for myelofibrosis provide spleen and symptom improvements but do not address anemia, a negative prognostic factor. Momelotinib, an inhibitor of ACVR1/ALK2, JAK1 and JAK2, demonstrated activity against anemia, symptoms, and splenomegaly in the phase 3 SIMPLIFY trials. Here, we report mature overall survival (OS) and leukemia-free survival (LFS) from both studies, and retrospective analyses of baseline characteristics and efficacy endpoints for OS associations. Survival distributions were similar between JAKi-naïve patients randomized to momelotinib, or ruxolitinib then momelotinib, in SIMPLIFY-1 (OS HR = 1.02 [0.73, 1.43]; LFS HR = 1.08 [0.78, 1.50]). Two-year OS and LFS were 81.6% and 80.7% with momelotinib and 80.6% and 79.3% with ruxolitinib then momelotinib. In ruxolitinib-exposed patients in SIMPLIFY-2, two-year OS and LFS were 65.8% and 64.2% with momelotinib and 61.2% and 59.7% with best available therapy then momelotinib (OS HR = 0.98 [0.59, 1.62]; LFS HR = 0.97 [0.59, 1.60]). Baseline transfusion independence (TI) was associated with improved survival in both studies (SIMPLIFY-1 HR = 0.474, p = 0.0001; SIMPLIFY-2 HR = 0.226, p = 0.0005). Week 24 TI response in JAKi-naïve, momelotinib-randomized patients was associated with improved OS in univariate (HR = 0.323; p < 0.0001) and multivariate (HR = 0.311; p < 0.0001) analyses. These findings underscore the importance of achieving or maintaining TI in myelofibrosis, supporting the clinical relevance of momelotinib’s pro-erythropoietic mechanism of action, and potentially informing treatment decision-making.

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.

Thrombocytopenia in Patients With Myelofibrosis: Pathogenesis, Prevalence, Prognostic Impact, and Treatment

Myelofibrosis (MF) is a clonal hematopoietic stem cell neoplasm, characterized by pathologic myeloproliferation associated with inflammatory and pro-angiogenic cytokine release, that results in functional compromise of the bone marrow. Thrombocytopenia is a disease-related feature of MF, which portends a poor prognosis impacting overall survival (OS) and leukemia free survival. Thrombocytopenia in MF has multiple causes including ineffective hematopoiesis, splenic sequestration, and treatment-related effects. Presently, allogeneic hematopoietic stem cell transplantation (HSCT) remains the only curable treatment for MF, which, unfortunately, is only a viable option for a minority of patients. All other currently available therapies are either focused on improving cytopenias or the alleviating systemic symptoms and burdensome splenomegaly. While JAK2 inhibitors have moved to the forefront of MF therapy, available JAK inhibitors are advised against in patients with severe thrombocytopenia (platelets < 50 × 10⁹/L). In this review, we describe the pathogenesis, prevalence, and prognostic significance of thrombocytopenia in MF. We also explore the value and limitations of treatments directed at addressing cytopenias, splenomegaly and symptom burden, and those with potential disease modification. We conclude by proposing a treatment algorithm for patients with MF and severe thrombocytopenia.

Management of Myeloproliferative Neoplasms in the Molecular Era: From Research to Practice

The 1960 discovery of the Philadelphia chromosome in chronic myeloid leukemia (CML) marked the beginning of the modern genomic era of oncology. In the following years, the molecular underpinnings of CML were unraveled, culminating in the development of the first molecularly targeted therapy: imatinib. Imatinib revolutionized CML management, inducing deep molecular responses for most patients and aligning survival curves with those of age-matched control participants. Five additional tyrosine kinase inhibitors are now approved for CML: dasatinib, nilotinib, bosutinib, ponatinib, and asciminib (approved October 2021). The 2005 discovery of JAK2 mutations in myelofibrosis (MF) sparked enthusiasm that molecularly targeted therapies could have a similar impact in that disease. Three JAK inhibitors are now available for MF: ruxolitinib, fedratinib, and pacritinib (approved February 2022). JAK inhibitors are helpful for improving symptoms and splenomegaly but still only scratch the surface of MF pathophysiology. Clinical research testing novel agents, next-generation JAK inhibitors, and combinations of JAK inhibitors plus novel agents is moving at a tremendous pace in the hope that outcomes for patients with MF may mirror those with CML one day. This review provides an update on the status of clinical care and research for MF and addresses ongoing issues related to CML management.

Momelotinib for the treatment of myelofibrosis with anemia

Myelofibrosis is a myeloproliferative neoplasm characterized by splenomegaly, debilitating constitutional symptoms and bone marrow failure. Disease-related anemia is common and associated with an inferior quality of life and survival. Unfortunately, few therapies exist to improve hemoglobin in myelofibrosis patients. Momelotinib is a JAK1/JAK2 inhibitor that also antagonizes ACVR1, leading to downregulation of hepcidin expression and increased availability of iron for erythropoiesis. In clinical testing, momelotinib has demonstrated a unique ability to improve hemoglobin and reduce transfusion burden in myelofibrosis patients with baseline anemia, while producing reductions in spleen size and symptom burden. This review explores the preclinical rationale, clinical trial data and future role of momelotinib in the evolving therapeutic landscape of myelofibrosis.

The role of TBK1 in cancer pathogenesis and anticancer immunity

The TANK-binding kinase 1 (TBK1) is a serine/threonine kinase belonging to the non-canonical inhibitor of nuclear factor-κB (IκB) kinase (IKK) family. TBK1 can be activated by pathogen-associated molecular patterns (PAMPs), inflammatory cytokines, and oncogenic kinases, including activated K-RAS/N-RAS mutants. TBK1 primarily mediates IRF3/7 activation and NF-κB signaling to regulate inflammatory cytokine production and the activation of innate immunity. TBK1 is also involved in the regulation of several other cellular activities, including autophagy, mitochondrial metabolism, and cellular proliferation. Although TBK1 mutations have not been reported in human cancers, aberrant TBK1 activation has been implicated in the oncogenesis of several types of cancer, including leukemia and solid tumors with KRAS-activating mutations. As such, TBK1 has been proposed to be a feasible target for pharmacological treatment of these types of cancer. Studies suggest that TBK1 inhibition suppresses cancer development not only by directly suppressing the proliferation and survival of cancer cells but also by activating antitumor T-cell immunity. Several small molecule inhibitors of TBK1 have been identified and interrogated. However, to this point, only momelotinib (MMB)/CYT387 has been evaluated as a cancer therapy in clinical trials, while amlexanox (AMX) has been evaluated clinically for treatment of type II diabetes, nonalcoholic fatty liver disease, and obesity. In this review, we summarize advances in research into TBK1 signaling pathways and regulation, as well as recent studies on TBK1 in cancer pathogenesis. We also discuss the potential molecular mechanisms of targeting TBK1 for cancer treatment. We hope that our effort can help to stimulate the development of novel strategies for targeting TBK1 signaling in future approaches to cancer therapy.

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.

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

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

Managing patients with myelofibrosis and thrombocytopenia

INTRODUCTION

: Given the progressive nature of myelofibrosis, the incidence of thrombocytopenia increases over time. Furthermore, approved drugs ruxolitinib and fedratinib, induce thrombocytopenia. Hence, treatment of myelofibrosis patients with low platelet counts is an unmet need.

AREAS COVERED

: This review summarizes the current and emerging treatment options available for patients with myelofibrosis and thrombocytopenia. In the first section of this review, we summarized the use of JAK inhibitors in patients with thrombocytopenia, and in the second part, we focused on use of therapies other than JAK Inhibitors such as steroids, immunomodulatory agents, androgens and other novel agents.

EXPERT OPINION

: Up to 25% of patients with myelofibrosis have platelet counts below 100,000 at presentation. Patients with thrombocytopenia are more likely to be anemic and PRBC transfusion-dependent, as well as have high-risk disease characteristics and a poor overall survival rate.. Among all JAK inhibitors studied in phase 3 clinical trials, pacritinib seems not to induce significant thrombocytopenia while maintaining a good spleen response. Severe thrombocytopenia is a major impediment to myelofibrosis therapy, and more research, particularly on novel therapeutic agents aimed at cytopenic patient populations, is needed.

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.

Emerging drugs for the treatment of myelofibrosis: phase II & III clinical trials

INTRODUCTION

Myelofibrosis is a clonal hematologic malignancy with clinical manifestations that include cytopenias, debilitating constitutional symptoms, splenomegaly, bone marrow fibrosis and a propensity toward leukemic progression. While allogeneic hematopoietic stem cell transplantation can be curative, this therapy is not available for the majority of patients. Ruxolitinib and fedratinib are approved JAK2 inhibitors that have produced meaningful benefits in terms of spleen reduction and symptom improvement, but there remain several unmet needs.

AREAS COVERED

We discuss novel therapies based upon published data from phase II or III clinical trials. Specifically, we cover novel JAK inhibitors (momelotinib and pacritinib), and agents that target bromodomain and extra-terminal domain (pelabresib), the antiapoptotic proteins BCL-2/BCL-xL (navitoclax), MDM2 (navtemadlin), phosphatidylinositol 3-kinase (parsaclisib), or telomerase (imetelstat).

EXPERT OPINION

Patients with disease related cytopenias are ineligible for currently approved JAK2 inhibitors. However, momelotinib and pacritinib may be able to fill this void. Novel therapies are being evaluated in the upfront setting to improve the depth and duration of responses with ruxolitinib. Future evaluation of agents must be judged on their potential to modify disease progression, which current JAK2 inhibitors lack. Combination therapy, possibly with an immunotherapeutic agent might serve as key components of future myelofibrosis treatment options.

Novel therapeutics and targets in myelofibrosis

Myelofibrosis is a myeloproliferative neoplasm characterized by clonal proliferation of myeloid cells, bone marrow fibrosis and cytopenias, extramedullary hematopoiesis and hepatosplenomegaly, increased pro-inflammatory cytokine production, and systemic symptoms. Patients with MF also have a propensity toward leukemic transformation. Allogeneic hematopoietic stem cell transplantation (aHCT) is the only curative therapy for patients with MF; however, transplant-related morbidity and mortality precludes this option for the majority of patients. In the last decade, two targeted therapies have been approved for the treatment of MF, both JAK2 inhibitors, ruxolitinib and fedratinib. Despite the clinical efficacy of these two compounds in terms of splenomegaly and symptom burden reduction, there remain many areas of unmet need in the treatment of myelofibrosis. In this review, we discuss the limitations of currently approved treatment options and novel therapeutic targets with drug candidates in late-stage (phase II or III) clinical development for the treatment of MF. We delve into the mechanism of action and scientific rational of each candidate agent as well as the available clinical data, and ongoing trials that could lead to the approval of some of these novel therapies.

Novel strategies for challenging scenarios encountered in managing myelofibrosis

Given its rarity, multi-faceted clinical presentation and the relative paucity of approved therapies, the management of myeloproliferative neoplasm (MPN)-associated myelofibrosis (MF) can be challenging. Janus kinase (JAK) inhibitors, the only approved agents at present, have brought many clinical benefits to patients, with prolongation of survival also demonstrated for ruxolitinib. However, these agents have clear limitations. Optimal management of anemia in MF remains a major unmet need. Neither ruxolitinib nor fedratinib is recommended for use in patients with severe thrombocytopenia, i.e. platelets <50 × 10⁹/L, who have a particularly poor prognosis. The search for the optimal partner for JAK inhibitors to address some of the shortcomings of these agents (e.g. limited ability to improve bone marrow fibrosis, cytopenias and induce molecular responses) and achieve meaningful 'disease modification' continues. This has led to the development of a number of rational, preclinically synergistic combinations for use either upfront or in the setting of sub-optimal response to JAK inhibition. Finally, the outlook for patients whose disease progresses on JAK inhibitor therapy continues to be grim, and agents with alternative mechanisms of action may be needed in this setting. In this article, we use a case-based approach to illustrate challenges commonly encountered in clinical practice and our management of the same. Fortunately, there has been enormous growth in drug development efforts in the MF space in the last few years, some of which appear poised to bear fruit in the very near future.

TP0463518 (TS-143) Ameliorates Peptidoglycan-Polysaccharide Induced Anemia of Inflammation in Rats

TP0463518 (TS-143) is a competitive prolyl hydroxylase 1/2/3 pan-inhibitor, and has been shown to specifically stabilize hypoxia-inducible factor-2 alpha in the liver to increase erythropoietin production. While TP0463518 has been shown to improve renal anemia, its effect on anemia of inflammation is still unknown. In this study, we created a rat model of anemia of inflammation by administering peptidoglycan-polysaccharide (PG-PS) to Lewis rats; the PG-PS-treated rats developed anemia within 2 weeks after the PG-PS challenge. The hematopoietic effects of oral TP0463518 administration at 10 mg/kg once daily for 6 weeks were examined in this rat model. The hematocrit values in the TP0463518-treated group increased significantly from 32.8 ± 0.8 to 44.5 ± 2.1% after the treatment, which was comparable to that in the healthy control group. The change of the mean corpuscular volume following TP0463518 treatment was similar to that in the healthy control group up to week 4, and significantly higher than that in the vehicle-treated group. TP0463518 increased divalent metal transporter 1 and duodenal cytochrome b expressions in the intestine. Conversely, TP0465318 did not exert any effects on the expressions of genes involved in iron metabolism in the liver, even though TP0463518 dramatically increased erythropoietin expression. Furthermore, TP0463518 had no effect on the expressions of inflammation markers in the liver. These results suggest that TP0463518 increased iron absorption and improved anemia of inflammation without exacerbating liver inflammation. TP0463518 appears to have an acceptable safety profile and could become a useful new therapeutic option for anemia of inflammation.

New Horizons in Myeloproliferative Neoplasms Treatment: A Review of Current and Future Therapeutic Options

Philadelphia-negative myeloproliferative neoplasms (MPN) are aggressive diseases characterized by clonal proliferation of myeloid stem cells. The clonal process leads to excessive red cells production, platelets production, and bone marrow fibrosis. According to the phenotype, MPN can be classified as polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF). MPN patients have shortened survival due to the increased risk of thrombosis, hemorrhages, and transformation to acute myeloid leukemia (AML). Prognosis is variable, with a shorter life expectancy in myelofibrosis. Currently, drug therapy can reduce symptoms, splenomegaly, and risk of thrombosis. Still, some patients can be resistant or intolerant to the treatment. At the same time, allogeneic stem cell transplant (ASCT) is the only treatment modality with the potential to cure the disease. Nevertheless, the ASCT is reserved for high-risk leukemic progression patients due to the risk of treatment-related death and comorbidity. Therefore, there is a need for new drugs that can eradicate clonal hematopoiesis and prevent progression to more aggressive myeloid neoplasms. Thanks to the better understanding of the disease’s molecular pathogenesis, many new potentially disease-modifying drugs have been developed and are currently in clinical trials. This review explores the most promising new drugs currently in clinical trials.

Physiology and Inflammation Driven Pathophysiology of Iron Homeostasis-Mechanistic Insights into Anemia of Inflammation and Its Treatment

Anemia is very common in patients with inflammatory disorders. Its prevalence is associated with severity of the underlying disease, and it negatively affects quality of life and cardio-vascular performance of patients. Anemia of inflammation (AI) is caused by disturbances of iron metabolism resulting in iron retention within macrophages, a reduced erythrocyte half-life, and cytokine mediated inhibition of erythropoietin function and erythroid progenitor cell differentiation. AI is mostly mild to moderate, normochromic and normocytic, and characterized by low circulating iron, but normal and increased levels of the storage protein ferritin and the iron hormone hepcidin. The primary therapeutic approach for AI is treatment of the underlying inflammatory disease which mostly results in normalization of hemoglobin levels over time unless other pathologies such as vitamin deficiencies, true iron deficiency on the basis of bleeding episodes, or renal insufficiency are present. If the underlying disease and/or anemia are not resolved, iron supplementation therapy and/or treatment with erythropoietin stimulating agents may be considered whereas blood transfusions are an emergency treatment for life-threatening anemia. New treatments with hepcidin-modifying strategies and stabilizers of hypoxia inducible factors emerge but their therapeutic efficacy for treatment of AI in ill patients needs to be evaluated in clinical trials.

SOHO State of the Art Updates and Next Questions: Identifying and Treating "Progression" in Myelofibrosis

Over the last decade, the Janus kinase (JAK) 1/2 inhibitor ruxolitinib has become widely established as the cornerstone of pharmacologic therapy for most patients with myelofibrosis (MF), providing dramatic and durable benefits in terms of splenomegaly and symptoms, and prolonging survival. Ruxolitinib does not address all aspects of the disease, however; notably cytopenias, and its ability to modify the underlying biology of the disease remains in question. Furthermore, patients eventually lose response to ruxolitinib. Multiple groups have reported the median overall survival of MF patients after ruxolitinib discontinuation to be 13 to 14 months. While consensus criteria only recognize splenic and blast progression as "progressive disease" in patients with MF, disease progression can occur in a variety of ways. Besides increasing splenomegaly and progression to accelerated phase/leukemic transformation, patients may develop worsening disease-related symptoms, cytopenias, progressive leukocytosis, extramedullary hematopoiesis, etc. As in the frontline setting, treatment needs to be tailored to the clinical needs of the patient. Current treatment options for patients with MF who fail ruxolitinib remain unsatisfactory, and this continues to represent an area of major unmet medical need. The regulatory approval of fedratinib has introduced an important option in the postruxolitinib setting. Fortunately, a plethora of novel agents, both new JAK inhibitors and drugs from other classes, eg, bromodomain and extraterminal (BET), murine double minute 2 (MDM2) and telomerase inhibitors, activin receptor ligand traps, BH3-mimetics and more, are poised to greatly expand the therapeutic armamentarium for patients with MF if successful in pivotal trials.

Classical Philadelphia-negative myeloproliferative neoplasms (MPNs): A continuum of different disease entities

Classical Philadelphia-negative myeloproliferative neoplasms (MPNs) are clonal hematopoietic stem cell-derived disorders characterized by uncontrolled proliferation of differentiated myeloid cells and close pathobiologic and clinical features. According to the 2016 World Health Organization (WHO) classification, MPNs include polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF). The 2016 revision aimed in particular at strengthening the distinction between masked PV and JAK2-mutated ET, and between prefibrotic/early (pre-PMF) and overt PMF. Clinical manifestations in MPNs include constitutional symptoms, microvascular disorders, thrombosis and bleeding, splenomegaly secondary to extramedullary hematopoiesis, cytopenia-related symptoms, and progression to overt MF and acute leukemia. A dysregulation of the JAK/STAT pathway is the unifying mechanistic hallmark of MPNs, and is guided by somatic mutations in driver genes including JAK2, CALR and MPL. Additional mutations in myeloid neoplasm-associated genes have been also identified, with established prognostic relevance, particularly in PMF. Prognostication of MPN patients relies on disease-specific clinical models. The increasing knowledge of MPN biology led to the development of integrated clinical and molecular prognostic scores that allow a more refined stratification. Recently, the therapeutic landscape of MPNs has been revolutionized by the introduction of potent, selective JAK inhibitors (ruxolitinib, fedratinib), that proved effective in controlling disease-related symptoms and splenomegaly, yet leaving unmet critical needs, owing the lack of disease-modifying activity. In this review, we will deal with molecular, clinical, and therapeutic aspects of the three classical MPNs aiming at highlighting either shared characteristics, that overall define a continuum within a single disease family, and uniqueness, at the same time.

Management of Myelofibrosis-Associated Anemia: Focus on Standard Agents and Novel Therapeutics in Phase 3 Clinical Trials

PURPOSE OF REVIEW

The management of myelofibrosis is risk-adapted when considering transplant eligibility and symptom-directed, prioritizing the most burdensome symptoms for the patient. Unfortunately, myelofibrosis-anemia is common, multifactorial in its origin, and impactful regarding prognosis. While clinical trials are advised, not all patients have convenient access, and therefore, hematologists should be aware of the data supporting the use of conventional agents such as erythropoietin-stimulating agents, steroid treatments (danazol and prednisone), and immunomodulatory drugs (thalidomide and lenalidomide). This review summarizes the conventional approach to treating myelofibrosis-anemia and highlights recent data from 3 novel agents that are under phase 3 evaluation.

RECENT FINDINGS

Momelotonib is a JAK1/2 and ACVR1 inhibitor that has demonstrated not only improvements in splenomegaly and symptoms, but also amelioration of anemia on the SIMPLIFY 1 and 2 clinical trial program. This may occur through suppression of hepcidin production. Luspatercept promotes late-stage hematopoiesis, and the phase 2 study has shown promise in ameliorating anemia as a monotherapy, and especially in combination with ruxolitinib. Finally, CP-0160, a BET inhibitor, has shown efficacy as an anemia-directed agent, when used as monotherapy and in combination. This agent reduces cytokine production and promotes erythroid differentiation. Results have been presented for patients previously treated with JAK inhibitors, as well as those who were naïve to JAK inhibitor therapy. Safety and effectiveness are reviewed for both conventional and selected novel agents used in the treatment of MF-anemia. A practical approach to treatment is presented, and data from ASH 2020 are presented.

The Role of Iron in Benign and Malignant Hematopoiesis

Significance: Iron is an essential element required for sustaining a normal healthy life. However, an excess amount of iron in the bloodstream and tissue generates toxic hydroxyl radicals through Fenton reactions. Henceforth, a balance in iron concentration is extremely important to maintain cellular homeostasis in both normal hematopoiesis and erythropoiesis. Iron deficiency or iron overload can impact hematopoiesis and is associated with many hematological diseases. Recent Advances: The mechanisms of action of key iron regulators such as erythroferrone and the discovery of new drugs, such as ACE-536/luspatercept, are of potential interest to treat hematological disorders, such as β-thalassemia. New therapies targeting inflammation-induced ineffective erythropoiesis are also in progress. Furthermore, emerging evidences support differential interactions between iron and its cellular antioxidant responses of hematopoietic and neighboring stromal cells. Both iron and its systemic regulator, such as hepcidin, play a significant role in regulating erythropoiesis. Critical Issues: Significant pre-clinical studies are on the way and new drugs targeting iron metabolism have been recently approved or are undergoing clinical trials to treat pathological conditions with impaired erythropoiesis such as myelodysplastic syndromes or β-thalassemia. Future Directions: Future studies should explore how iron regulates hematopoiesis in both benign and malignant conditions. Antioxid. Redox Signal. 35, 415-432.

Recent Advances in ALK2 Inhibitors

Activin receptor-like kinase-2 (ALK2) is a type I bone morphogenetic protein (BMP) receptor which has a role in biological processes that control the development of bone, heart, brain, and other tissue. Gain of function mutations in ALK2 have been identified in fibrodysplasia ossificans progressiva (FOP) and the childhood brain tumor, diffuse intrinsic pontine glioma (DIPG), which has given focus to the development of ALK2 inhibitors as targeted treatments. This review covers the structural features of ALK2 inhibitors which contribute to their ALK2 potency and selectivity, and the pharmacokinetic or in vivo efficacy data available to demonstrate their suitability for treating a peripheral or CNS disease.

A case of a primary myelofibrosis with progression and related literature review of progression phase genetics

Philadelphia (BCR-ABL)-negative myeloproliferative neoplasms (MPNs) include polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF). MPN can transform into an accelerated or a blast phase, which is associated with poor response to standard therapy and low overall median survival. We present an interesting case of a patient with a history of PMF and progression and summarize the current studies on genetic features of myeloproliferative neoplasms in blast phase (MPN-BP) with an emphasis on PMF. Although MPN-BP show ≥20% blasts in peripheral blood or bone marrow, it is not considered as acute myeloid leukemia (AML) according to the WHO classification. While MPNs-BP typically lack genetic mutations seen in de novo AML, they commonly harbor IDH1/2, SRSF2, ASXL1, and TP53 mutations, similar to the genetic profiles of acute myeloid leukemia with myelodysplasia-related changes (AML-MRC).

Inflammation in Myeloid Malignancies: From Bench to Bedside

Myeloid malignancies, stemming from a somatically mutated hematopoietic clone, can cause a wide variety of clinical consequences, including pancytopenia in myelodysplastic syndrome, overproduction of three myeloid lineages in myeloproliferative neoplasm, and the rapid growth of immature hematopoietic cells in acute myeloid leukemia (AML). It is becoming clear that inflammation is a hallmark feature of clonal myeloid conditions, ranging from clonal hematopoiesis of indeterminate potential to AML. Fundamental findings from laboratory research on inflammation in myeloid malignancies has potential implications for diagnosis, prognostication, and treatment in these diseases. In this review, we highlighted some pertinent basic science findings regarding the role of inflammation in myeloid malignancies and speculated how these findings could impact the clinical care of patients.

Efficacy and tolerability of Janus kinase inhibitors in myelofibrosis: a systematic review and network meta-analysis

Myelofibrosis is a myeloproliferative neoplasm associated with constitutional symptoms, increasing splenomegaly, and worsening cytopenias. Janus kinase (JAK) inhibitors have been used for the treatment of myelofibrosis for several years, but there is a lack of comparative information between those treatments. A systematic review and network meta-analysis was performed on randomized controlled trials in patients with myelofibrosis receiving JAK inhibitor or placebo or control. Primary outcomes were efficacy on spleen volume reduction and total symptom score reduction. Additional analyses were conducted on anemia and thrombopenia events. Seven studies were included in the network meta-analysis including 1953 patients randomly assigned to four JAK inhibitors—ruxolitinib, fedratinib, pacritinib, momelotinib—or control. In first-line therapy, momelotinib and fedratinib were associated with comparable efficacy to ruxolitinib, and with less toxicity on erythrocytes and platelets, respectively. Pacritinib was less effective on splenomegaly than ruxolitinib as a first-line treatment but seemed effective in second line, after ruxolitinib exposure. Fedratinib and ruxolitinib that are FDA approved in myelofibrosis have both confirmed being valuable option to treat splenomegaly and constitutional symptoms, and their slightly different tolerance-profiles can guide therapeutic choice for first-line treatment, according to patient profile. Momelotinib could be another option especially due to its positive effect on anemia.

Pharmacological Targeting of BMP6-SMAD Mediated Hepcidin Expression Does Not Improve the Outcome of Systemic Infections With Intra-Or Extracellular Gram-Negative Bacteria in Mice

Introduction

Hepcidin is the systemic master regulator of iron metabolism as it degrades the cellular iron exporter ferroportin. In bacterial infections, hepcidin is upregulated to limit circulating iron for pathogens, thereby increasing iron retention in macrophages. This mechanism withholds iron from extracellular bacteria but could be of disadvantage in infections with intracellular bacteria. We aimed to understand the role of hepcidin in infections with intra- or extracellular bacteria using different hepcidin inhibitors.

Methods

For the experiments LDN-193189 and oversulfated heparins were used, which interact with the BMP6-SMAD pathway thereby inhibiting hepcidin expression. We infected male C57BL/6N mice with either the intracellular bacterium Salmonella Typhimurium or the extracellular bacterium Escherichia coli and treated these mice with the different hepcidin inhibitors.

Results

Both inhibitors effectively reduced hepcidin levels in vitro under steady state conditions and upon stimulation with the inflammatory signals interleukin-6 or lipopolysaccharide. The inhibitors also reduced hepcidin levels and increased circulating iron concentration in uninfected mice. However, both compounds failed to decrease liver- and circulating hepcidin levels in infected mice and did not affect ferroportin expression in the spleen or impact on serum iron levels. Accordingly, both BMP-SMAD signaling inhibitors did not influence bacterial numbers in different organs in the course of E.coli or S.Tm sepsis.

Conclusion

These data indicate that targeting the BMP receptor or the BMP-SMAD pathway is not sufficient to suppress hepcidin expression in the course of infection with both intra- or extracellular bacteria. This suggests that upon pharmacological inhibition of the central SMAD-BMP pathways during infection, other signaling cascades are compensatorily induced to ensure sufficient hepcidin formation and iron restriction to circulating microbes.

20 years of Hepcidin: How far we have come

Twenty years ago the discovery of hepcidin deeply changed our understanding of the regulation of systemic iron homeostasis. It is now clear that hepcidin orchestrates systemic iron levels by controlling the amount of iron exported into the bloodstream through ferroportin. Hepcidin expression is increased in situations where systemic iron levels should be reduced, such as in iron overload and infection. Conversely, hepcidin is repressed during iron deficiency, hypoxia or expanded erythropoiesis, to increase systemic iron availability and sustain erythropoiesis. In this review, we will focus on molecular mechanisms of hepcidin regulation and on the pathological consequences of their disruption.

Physiological and pathophysiological mechanisms of hepcidin regulation: clinical implications for iron disorders

The discovery of hepcidin has provided a solid foundation for understanding the mechanisms of systemic iron homeostasis and the aetiologies of iron disorders. Hepcidin assures the balance of circulating and stored iron levels for multiple physiological processes including oxygen transport and erythropoiesis, while limiting the toxicity of excess iron. The liver is the major site where regulatory signals from iron, erythropoietic drive and inflammation are integrated to control hepcidin production. Pathologically, hepcidin dysregulation by genetic inactivation, ineffective erythropoiesis, or inflammation leads to diseases of iron deficiency or overload such as iron-refractory iron-deficiency anaemia, anaemia of inflammation, iron-loading anaemias and hereditary haemochromatosis. In the present review, we discuss recent insights into the molecular mechanisms governing hepcidin regulation, how these pathways are disrupted in iron disorders, and how this knowledge is being used to develop novel diagnostic and therapeutic strategies.

ACVR1/JAK1/JAK2 inhibitor momelotinib reverses transfusion dependency and suppresses hepcidin in myelofibrosis phase 2 trial

Momelotinib (MMB) is a JAK1/2 and ACVR1 inhibitor with demonstrated clinical activity in all 3 hallmarks of myelofibrosis (MF): anemia, constitutional symptoms, and splenomegaly. In this phase 2 open-label translational biology study (NCT02515630) of 41 transfusion-dependent patients with MF, we explored mechanisms underlying the favorable activity of MMB on MF-associated iron-restricted anemia, including its impact on serum hepcidin levels, and markers of iron storage and availability, erythropoiesis, and inflammation. A transfusion-independent response (TI-R), defined as red blood cell transfusion independence (TI) ≥12 weeks at any time on study, occurred in 17 patients (41%; 95% confidence interval [CI], 26%-58%), including 14 patients (34%; 95% CI, 20%-51%) who achieved TI-R by week 24. In addition, 78% of TI nonresponse (TI-NR) patients achieved a ≥50% decrease in transfusion requirement for ≥8 weeks. Adverse events (AEs) were consistent with previous studies of MMB in MF, with cough, diarrhea, and nausea as the most common. Twenty-one patients experienced grade ≥3 AEs, most commonly anemia and neutropenia. Consistent with preclinical data, daily MMB treatment led to an acute and persistent decrease in blood hepcidin associated with increased iron availability and markers of erythropoiesis. Baseline characteristics associated with TI-R were lower inflammation and hepcidin as well as increased markers of erythropoiesis and bone marrow function. Overall, the study demonstrates that MMB treatment decreases hepcidin in conjunction with improving iron metabolism and erythropoiesis, suggesting a mechanistic explanation for the reduced transfusion dependency observed in transfusion-dependent MF patients treated with MMB, thereby addressing the key unmet medical need in the MF population.

Next Generation Therapeutics for the Treatment of Myelofibrosis

Myelofibrosis is a myeloproliferative neoplasm characterized by splenomegaly, constitutional symptoms, bone marrow fibrosis, and a propensity towards transformation to acute leukemia. JAK inhibitors are the only approved therapy for myelofibrosis and have been successful in reducing spleen and symptom burden. However, they do not significantly impact disease progression and many patients are ineligible due to coexisting cytopenias. Patients who are refractory to JAK inhibition also have a dismal survival. Therefore, non-JAK inhibitor-based therapies are being explored in pre-clinical and clinical settings. In this review, we discuss novel treatments in development for myelofibrosis with targets outside of the JAK-STAT pathway. We focus on the mechanism, preclinical rationale, and available clinical efficacy and safety information of relevant agents including those that target apoptosis (navitoclax, KRT-232, LCL-161, imetelstat), epigenetic modulation (CPI-0610, bomedemstat), the bone marrow microenvironment (PRM-151, AVID-200, alisertib), signal transduction pathways (parsaclisib), and miscellaneous agents (tagraxofusp. luspatercept). We also provide commentary on the future of therapeutic development in myelofibrosis.

Effect of hepcidin antagonists on anemia during inflammatory disorders

Iron is an essential element for the mammalian body however, its homeostasis must be regulated accurately for appropriate physiological functioning. Alterations in physiological iron levels can lead to moderate to severe iron disorders like chronic and acute iron deficiency (anemia) or iron overload. Hepcidin plays an important role in regulating homeostasis between circulating iron and stored iron in the cells as well as the absorption of dietary iron in the intestine. Inflammatory disorders restrict iron absorption from food due to increased circulating levels of hepcidin. Increased production of hepcidin causes ubiquitination of ferroportin (FPN) leading to its degradation, thereby retaining iron in the spleen, duodenal enterocytes, macrophages, and hepatocytes. Hepcidin inhibitors and antagonists play a consequential role to ameliorate inflammation-associated anemia. Many natural and synthesized compounds, able to reduce hepcidin expression during inflammation have been identified in recent years. Few of which are currently at various phases of clinical trial. This article comprises a comprehensive review of therapeutic approaches for the efficient treatment of anemia associated with inflammation. Many strategies have been developed targeting the hepcidin-FPN axis to rectify iron disorders. Hepcidin modulation with siRNAs, antibodies, chemical compounds, and plant extracts provides new insights for developing advanced therapeutics for iron-related disorders. Hepcidin antagonist's treatment has a high potential to improve iron status in patients with iron disorders, but their clinical success needs further recognition along with the identification and application of new therapeutic approaches.

Myelofibrosis: challenges for preclinical models and emerging therapeutic targets

Introduction: Myelofibrosis (MF) is characterized by anemia, splenomegaly, constitutional symptoms and bone marrow fibrosis. MF has no curative treatment to date, except for a small subset of patients that are eligible for allogeneic hematopoietic stem cell transplant. The discovery in recent years of the MF mutational landscape and the role of bone marrow microenvironment in disease pathogenesis has led to further insights into disease biology and consequentially rationally derived therapies.Areas covered: We searched PubMed/Medline/American Society of Hematology (ASH) abstracts until November 2020 using the following terms: myelofibrosis, mouse models, pre-clinical studies and clinical trials. The development of targeted therapies is aimed to modify the history of the disease. Although JAK inhibitors showed encouraging results in terms of spleen and symptoms response, long term remissions and disease modifying ability is lacking. Beyond JAK inhibitors, a range of agents targeting proliferative, metabolic, apoptotic pathways, the microenvironment, epigenetic modification and immunomodulation are in various stages of investigations. We review pre-clinical data, preliminary clinical results of these agents, and finally offer insights on the management of MF patients.Expert opinion: MF patients refractory or with suboptimal response to JAK inhibitors, may be managed by addition of agents with differing mechanisms, such as bromodomain (BET), lysine demethylase 1 (LSD1), MDM2, or Bcl-Xl inhibitors which could prevent emergence of resistance. Immunotherapies as long-acting interferons, and calreticulin directed antibodies or peptide vaccination are eagerly awaited. Historically, therapeutic challenges in MF have arisen due to the fact that rationally derived therapies that are based on murine models have limited impact on fibrosis and underlying disease biology in human studies, the latter illustrates the complex multi-faceted disease pathogenesis of MF. Together, we not only suggest individualized therapy in MF that is guided by genomic signature but also its early implementation potentially in prefibrotic MF.

MOMENTUM: momelotinib vs danazol in patients with myelofibrosis previously treated with JAKi who are symptomatic and anemic

Hallmark features of myelofibrosis (MF) are cytopenias, constitutional symptoms and splenomegaly. Anemia and transfusion dependency are among the most important negative prognostic factors and are exacerbated by many JAK inhibitors (JAKi). Momelotinib (MMB) has been investigated in over 820 patients with MF and possesses a pharmacological and clinical profile differentiated from other JAKi by inhibition of JAK1, JAK2 and ACVR1. MMB is designed to address the complex drivers of iron-restricted anemia and chronic inflammation in MF and should improve constitutional symptoms and splenomegaly while maintaining or improving hemoglobin in JAKi-naive and previously JAKi-treated patients. The MOMENTUM Phase III study is designed to confirm and extend observations of safety and clinical activity of MMB.

TAM-ing the CIA-Tumor-Associated Macrophages and Their Potential Role in Unintended Side Effects of Therapeutics for Cancer-Induced Anemia

Cancer-induced anemia (CIA) is a common consequence of neoplasia and has a multifactorial pathophysiology. The immune response and tumor treatment, both intended to primarily target malignant cells, also affect erythropoiesis in the bone marrow. In parallel, immune activation inevitably induces the iron-regulatory hormone hepcidin to direct iron fluxes away from erythroid progenitors and into compartments of the mononuclear phagocyte system. Moreover, many inflammatory mediators inhibit the synthesis of erythropoietin, which is essential for stimulation and differentiation of erythroid progenitor cells to mature cells ready for release into the blood stream. These pathophysiological hallmarks of CIA imply that the bone marrow is not only deprived of iron as nutrient but also of erythropoietin as central growth factor for erythropoiesis. Tumor-associated macrophages (TAM) are present in the tumor microenvironment and display altered immune and iron phenotypes. On the one hand, their functions are altered by adjacent tumor cells so that they promote rather than inhibit the growth of malignant cells. As consequences, TAM may deliver iron to tumor cells and produce reduced amounts of cytotoxic mediators. Furthermore, their ability to stimulate adaptive anti-tumor immune responses is severely compromised. On the other hand, TAM are potential off-targets of therapeutic interventions against CIA. Red blood cell transfusions, intravenous iron preparations, erythropoiesis-stimulating agents and novel treatment options for CIA may interfere with TAM function and thus exhibit secondary effects on the underlying malignancy. In this Hypothesis and Theory, we summarize the pathophysiological hallmarks, clinical implications and treatment strategies for CIA. Focusing on TAM, we speculate on the potential intended and unintended effects that therapeutic options for CIA may have on the innate immune response and, consequently, on the course of the underlying malignancy.

A fully human anti-BMP6 antibody reduces the need for erythropoietin in rodent models of the anemia of chronic disease

Recombinant erythropoietin (EPO) and iron substitution are a standard of care for treatment of anemias associated with chronic inflammation, including anemia of chronic kidney disease. A black box warning for EPO therapy and concerns about negative side effects related to high-dose iron supplementation as well as the significant proportion of patients becoming EPO resistant over time explains the medical need to define novel strategies to ameliorate anemia of chronic disease (ACD). As hepcidin is central to the iron-restrictive phenotype in ACD, therapeutic approaches targeting hepcidin were recently developed. We herein report the therapeutic effects of a fully human anti-BMP6 antibody (KY1070) either as monotherapy or in combination with Darbepoetin alfa on iron metabolism and anemia resolution in 2 different, well-established, and clinically relevant rodent models of ACD. In addition to counteracting hepcidin-driven iron limitation for erythropoiesis, we found that the combination of KY1070 and recombinant human EPO improved the erythroid response compared with either monotherapy in a qualitative and quantitative manner. Consequently, the combination of KY1070 and Darbepoetin alfa resulted in an EPO-sparing effect. Moreover, we found that suppression of hepcidin via KY1070 modulates ferroportin expression on erythroid precursor cells, thereby lowering potentially toxic-free intracellular iron levels and by accelerating erythroid output as reflected by increased maturation of erythrocyte progenitors. In summary, we conclude that treatment of ACD, as a highly complex disease, becomes more effective by a multifactorial therapeutic approach upon mobilization of endogenous iron deposits and stimulation of erythropoiesis.