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.

The safety of JAK kinase inhibitors for the treatment of myelofibrosis.

INTRODUCTION: During the last decade, the development of small molecule inhibitors of Janus kinases (JAKi) contributed to revolutionize the therapeutic landscape of myelofibrosis (MF). JAKi proved to be effective in controlling disease-related symptoms and splenomegaly with remarkable inter-drug variability. However, in some cases the border between clinical efficacy of JAKi and dose-dependent toxicities is narrow leading to sub-optimal dose modifications and/or treatment discontinuation. AREAS COVERED: In the current review, the authors aimed at providing a comprehensive review of the safety profile of JAKi that are currently approved or in advanced clinical development. Also, a short discussion of promising JAKi in early clinical evaluation and molecules 'lost' early in clinical development is provided. Finally, we discuss the possible strategies aimed at strengthening the safety of JAKi while improving the therapeutic efficacy. EXPERT OPINION: Overall, JAKi display a satisfactory risk-benefit ratio, with main toxicities being gastrointestinal or related to the myelo/immunosuppressive effects, generally mild and easily manageable. However, JAKi may be associated with potentially life-threatening toxicities, such as neurological and infectious events. Thus, many efforts are needed in order to optimize JAKi-based therapeutic strategies without burdening patient safety. This could be attempted through drug combinations or the development of more selective molecules.

Transforming growth factor ß-mediated micromechanics modulates disease progression in primary myelofibrosis.

Primary myelofibrosis (PMF) is a Ph-negative myeloproliferative neoplasm (MPN), characterized by advanced bone marrow fibrosis and extramedullary haematopoiesis. The bone marrow fibrosis results from excessive proliferation of fibroblasts that are influenced by several cytokines in the microenvironment, of which transforming growth factor-ß (TGF-ß) is the most important. Micromechanics related to the niche has not yet been elucidated. In this study, we hypothesized that mechanical stress modulates TGF-ß signalling leading to further activation and subsequent proliferation and invasion of bone marrow fibroblasts, thus showing the important role of micromechanics in the development and progression of PMF, both in the bone marrow and in extramedullary sites. Using three PMF-derived fibroblast cell lines and transforming growth factor-ß receptor (TGFBR) 1 and 2 knock-down PMF-derived fibroblasts, we showed that mechanical stress does stimulate the collagen synthesis by the fibroblasts in patients with myelofibrosis, through the TGFBR1, which however seems to be activated through alternative pathways, other than TGFBR2.

Reduced renal function strongly affects survival and thrombosis in patients with myelofibrosis.

We retrospectively investigated a cohort of 176 myelofibrosis patients (128 primary-PMF; 48 secondary-SMF) from five hematology centers. The presence of chronic kidney disease (CKD) was determined in addition to other clinical characteristics. CKD was present in 26.1% of MF patients and was significantly associated with older age (P < 0.001), higher WBC (P = 0.015), and its subsets (neutrophil, monocyte, and basophil counts), higher platelets (P = 0.001), lower albumin (P = 0.018), higher serum uric acid (P = 0.001), higher LDH (P = 0.022), and the presence of CV risk factors (P = 0.011). There was no significant association with driver mutations, degree of bone marrow fibrosis, PMF/SMF, or DIPSS risk categories (P > 0.05 for all analyses). The presence of CKD was significantly associated with shorter time to arterial (HR = 3.49; P = 0.041) and venous thrombosis (HR = 7.08; P = 0.030) as well as with shorter overall survival (HR 2.08; P = 0.009). In multivariate analyses, CKD (HR = 1.8; P = 0.014) was associated with shorter survival independently of the DIPSS (HR = 2.7; P < 0.001); its effect being more pronounced in lower (HR = 3.56; P = 0.036) than higher DIPSS categories (HR = 2.07; P = 0.023). MF patients with CKD should be candidates for active management aimed at the improvement of renal function. Prospective studies defining the optimal therapeutic approach are highly needed.

Acquired Gray Platelet Syndrome Associated with Primary Myelofibrosis.

A 53-year-old man presented with uncontrolled bleeding caused by acquired platelet dysfunction accompanied by calreticulin-mutated primary myelofibrosis. Based on the detection of abnormal platelets, including large gray platelets, under light microscopy and the loss of the second wave of aggregation observed by light transmission aggregometry, the patient was diagnosed with platelet dysfunction accompanied by myeloproliferative neoplasms (MPNs). In addition, the absence of platelet α-granules was confirmed by electron microscopy. Therefore, this condition may be termed "acquired gray platelet syndrome." Acquired platelet dysfunction must be ruled out when abnormal platelets are observed in patients with MPNs.

Extramedullary haematopoiesis presenting as a periportal mass.

Extramedullary haematopoiesis (EMH) is defined as haematopoiesis occurring in organs outside the bone marrow. The liver is one of the rare sites of EMH, and to the best of our knowledge, a few cases of adult EMH of the liver have been reported in the last 20 years. Here, we reported the case of a 68-year-old man with a known history of myelofibrosis presented with vague abdominal pain. An abdominal CT scan showed a hypoattenuating periportal mass encasing the portal vein. The final diagnosis of EMH was made through the histopathological examination. This is a rare presentation of EMH, which may be easily mistaken for other pathologies such as metastases. Familiarity with this type of presentation aids in correctly diagnosing it in an appropriate clinical setting.

Investigational non-JAK inhibitors for chronic phase myelofibrosis.

INTRODUCTION: Patients with myelofibrosis (MF) have no effective treatment option after the failure of approved JAK inhibitor (JAKi) therapy. Non-JAK inhibitors (non-JAKi) that target non-canonical molecular pathways are undergoing clinical evaluations to optimize efficacy and/or to reduce hematological toxicity of JAKi. AREA COVERED: This article reviews the efficacy data from completed and ongoing early phase clinical trials of non-JAKi agents for chronic phase MF. The article also illuminates some of the challenges of myelofibrosis drug development. EXPERT OPINION: Most non-JAKi agents tested so far have shown modest benefit in improving the efficacy of ruxolitinib. Several novel agents such as BET inhibitor- CPI-0610, activin receptor ligand trap- luspatercept, recombinant pentraxin-PRM-151, telomerase inhibitor- imetelstat and bcl-2 inhibitor- navitoclax, have shown promising activity; however, they require vigorous evaluation in randomized controlled trials to understand the clinical benefit. Drugs that target new molecular pathways (MDM2, p-selectin, TIM-3, TGF-ß, aurora kinase) and immune-based strategies (CALR vaccine, anti-PD-1, allogeneic cord blood regulatory T cells) are in early phase trials. Further translational studies to target leukemic stem cells, improvement in trial designs by incorporating control arm and survival endpoints, and patient-focused collaborations among all stakeholders could pave a way for future success in MF drug development.

Patient characteristics and outcomes after ruxolitinib discontinuation in patients with myelofibrosis.

Background: This retrospective analysis evaluates morbidities, outcomes and associated risk factors in patients with myelofibrosis (MF) after ruxolitinib discontinuation, using Truven Health Analytics MarketScan (TR), Optum integrated virtual electronic health records and claims databases (OP), and Surveillance, Epidemiology, and End Results (SEER)-Medicare linked database (SM).Methods: A total of 290 patients with MF between 2006 and 2015 (using ICD-9 and ICD-O-3 codes), who were treated with and discontinued ruxolitinib were identified. Only patients with ≥90 days of medical history prior to index diagnosis (TR + OP) and Part A, B, and D enrollment at the time of index diagnosis (SM) were included. Morbidities were assessed during the 30-day period each following ruxolitinib initiation, prior to and post ruxolitinib discontinuation. Cumulative incidence of cytopenias and efficacy outcomes were evaluated from baseline.Results: Median age of patients was 68 years, with equal proportion of either gender. Median time to ruxolitinib discontinuation was 284 days and median follow-up after discontinuation was 70.9 days. The majority of patients were diagnosed with anemia and >30% of the patients received RBC transfusions during 30-day period prior to and the 30-day period post ruxolitinib discontinuation. After ruxolitinib discontinuation, half of the patients developed cytopenias. The median treatment progression-free survival, and overall survival after ruxolitinib discontinuation were 6.0 (4.4, 8.3) months and 11.1 (8.4, 14.5) months, respectively. Age at ruxolitinib discontinuation (HR [95% CI] = 2.071 [1.320, 3.248]), Charlson Comorbidity Index score (HR [95% CI] = 1.172 [1.093, 1.257]) and gender (HR [95% CI] = 1.620 [1.108, 2.369]) increased the risk of treatment progression (start of the subsequent treatment regimen) or death.Conclusion: Results from this large, retrospective, US population-based outcome analysis of MF patients show an increase in morbidity burden and identifies the risk factors of survival outcomes among real-world patients who have discontinued ruxolitinib.

Ruxolitinib therapy is associated with improved renal function in patients with primary myelofibrosis.

Recent evidence suggests that renal dysfunction may be a direct consequence of primary myelofibrosis (PMF). We performed a retrospective analysis of 100 patients with previously untreated PMF, receiving frontline treatment with single agent ruxolitinib, and compared them to 105 patients, receiving frontline treatment with a non-ruxolitinib-based therapy, matched by age, sex, DIPSS plus, and estimated glomerular filtration rate (eGFR). Use of ruxolitinib associated with a significantly higher rate of renal improvement (RI) > 10% (73% vs 50%, p = 0.01) confirmed on multivariate analysis (MVA) [odds ratio 3, 95% confidence interval (CI) 1.6-5.5, p < 0.001]. After a median follow-up of 41 months (range, 1-159 months), median failure-free survival (FFS) was 14 months (range, 1-117 months). Achievement of a RI > 10% maintained its independent association with prolonged FFS on MVA (hazard ratio 1.4, 95% CI 1.1-2, p = 0.02). Ruxolitinib can significantly improve renal function in patients with PMF, significantly impacting failure-free survival.

Development of a symptom assessment in patients with myelofibrosis: qualitative study findings.

BACKGROUND: The goal of the research reported here was to understand the patient experience of living with myelofibrosis (MF) and establish content validity of the Modified Myeloproliferative Neoplasm Symptom Assessment Diary (MPN-SD). METHODS: Qualitative interviews were performed in patients with MF, including both concept elicitation and cognitive debriefing. Patients with MF were asked to spontaneously report on their signs, symptoms, and impacts of MF, as well as their understanding of the MPN-SD content, and use of the tool on an electronic platform. A supplementary literature review and meetings with MF experts were also performed. RESULTS: Twenty-three patients with MF participated in qualitative interviews. Signs and symptoms most commonly reported by ruxolitinib-experienced patients (n = 16) were: fatigue and/or tiredness (n = 16, 100%), shortness of breath (n = 11, 69%), pain below the ribs on the left side and/or stomach pain and/or abdominal pain (n = 9, 56%), and enlarged spleen (n = 9, 56%) and for ruxolitinib-naïve patients (n = 7) were: fatigue and/or tiredness (n = 6, 86%), pain below the ribs on the left side (n = 6, 86%), enlarged spleen (n = 4, 57%), full quickly/filling up quickly (n = 4, 57%), night sweats and/or general sweats (n = 4, 57%), and itching (n = 4, 57%). Patients demonstrated that they were able to read, understand, and provide meaningful responses to the MPN-SD. The final version of the MPN-SD includes the 10 most commonly reported concepts from the MF patient interviews. CONCLUSIONS: The findings demonstrate the comprehensiveness of the MPN-SD in assessing MF symptoms in both ruxolitinib-experienced and ruxolitinib-naïve patients, while remaining easy for patients to understand and complete.

SOHO State of the Art Updates and Next Questions: Myelofibrosis.

The discovery of a mutation in the Janus Kinase 2 gene in 2005 spurred significant progress in the field of myeloproliferative neoplasms. A comprehensive description of genomic factors at play in the malignant clone in myeloproliferative neoplasms, particularly myelofibrosis (MF), have recently led to more precise, personalized prognostic tools. Despite this, understanding of the disease pathogenesis remains relatively limited. We continue to lack a detailed description of the interaction between the hematopoietic stem cell clone, abnormal bone marrow niche cells, and circulating signaling molecules and an understanding of how they cooperate to promote cell proliferation, fibrogenesis, and extramedullary hematopoiesis. Despite our knowledge gaps, recent research in MF has led to promising clinical translation. In this article, we summarize recent insights into MF pathophysiology, progress in the development of novel therapeutics, and opportunities for further advancement of the field.

EVALUATION OF BURDENSOME SYMPTOMS IN PATIENTS WITH RADIATION6ASSOCIATED AND SPONTANEOUS MYELOPROILIFERATIVE NEOPLASMS WITH THE USE OF OPTIMIZED SELF-ASSESSMENT MPN-SAF TSS. / OTsINKA OBTIaZhLYVYKh SYMPTOMIV U KhVORYKh NA RADIATsIINO-ASOTsIIOVANI TA SPONTANNI MIIeLOPROLIFERATYVNI NEOPLAZIÏ Z VYKORYSTANNIaM ADAPTOVANOÏ ShKALY SAMOOTsINKY MPN-SAF TSS.

OBJECTIVE: To investigate the intensity of burdensome symptoms using self-assessment MPN-SAF TSS in patientswith radiation-associated and spontaneous myeloproiliferative neoplasms (MPNs). MATERIALS AND METHODS: The study included 89 patients with radiation-associated and spontaneous MPNs, the bur-densome symptoms of MPN were determined using MPN-SAF TSS. RESULTS: The average score for complaints in patients with radiation-associated MPNs was significantly higher thanin patients with spontaneous MPNs - 43.46 and 25.04 points, respectively (p = 0.003). MPN patients classified bysubtypes also showed differences regarding intensity of burdensome MPN symptoms, demonstrating significantlyhigher average score of complaints among primary myelofibrosis patients (35.60), compared to polycythemia vera(29.60) and essential thrombocythemia (18.05) patients, (p = 0.005). Our study did not reveal any influence of theJAK2 V617F mutation on MPN burdensome symptoms intensity in MPN patients. CONCLUSIONS: We demonstrated a higher intensity of the MPN burdensome symptoms determined by the optimizedself-assessment MPN-SAF TSS in patients with radiation-associated, and in primary myelofibrosis patients, indicat-ing increased severity of patient's general conditions at the stage of diagnosis verification. It is advisable to usethe optimized MPN-SAF TSS at the moment of molecular genetic testing during the diagnosis of MPN for selectionor modifying treatment strategies in order to achieve better quality of life for patients.

99mTc-Sulfur Colloid Bone Marrow Scintigraphy in Diagnosis of Diffuse Pulmonary Extramedullary Hematopoiesis Secondary to Myelofibrosis.

Our objective was to define the role of combined 99mTc-sulfur colloid bone marrow (SC BM) scintigraphy, SPECT or SPECT/CT, and chest CT in diagnosing diffuse pulmonary extramedullary hematopoiesis (PEMH) in patients with myelofibrosis. Methods: We retrospectively reviewed 99mTc-SC BM scintigraphy scans performed at our institution for the diagnosis of diffuse PEMH, as well as accompanying chest CT and SPECT/CT imaging findings. Relevant clinical information, including respiratory manifestations, pulmonary hypertension, and subjective response to whole-lung radiation therapy, was also summarized. Results: Twenty-two myelofibrosis patients with 27 99mTc-SC BM scintigraphy scans were diagnosed with diffuse PEMH. In 21 patients (95%) with accompanying chest CT and SPECT/CT scans, the most common CT findings were ground-glass opacity, interstitial infiltration, and pleural effusion. Of 20 patients (91%) who underwent 2-dimensional echocardiography studies, 12 (55%) were diagnosed with pulmonary hypertension. All 12 patients exhibited the aforementioned nonspecific CT imaging findings, with 8 (66%) of them presenting with respiratory symptoms, including dyspnea, shortness of breath, and cough. In the remaining 8 patients, without pulmonary hypertension, half had similar respiratory symptoms. Fourteen patients (64%) of this cohort received whole-lung radiation therapy, of whom 7 (50%) experienced symptom relief after therapy. Conclusion: Nonspecific respiratory symptoms should raise concern about pulmonary hypertension and diffuse PEMH in patients with advanced-stage myelofibrosis. Combined 99mTc-SC BM scintigraphy and SPECT/CT is a promising noninvasive imaging tool to diagnose this rare clinical entity.Key Words: hematology; respiratory; SPECT/CT; pulmonary hematopoiesis; Tc-99m sulfur colloid scintigraphy; myelofibrosis.

Understanding Splenomegaly in Myelofibrosis: Association with Molecular Pathogenesis.

Myelofibrosis (MF) is a clinical manifestation of chronic BCR-ABL1-negative chronic myeloproliferative neoplasms. Splenomegaly is one of the major clinical manifestations of MF and is directly linked to splenic extramedullary hematopoiesis (EMH). EMH is associated with abnormal trafficking patterns of clonal hematopoietic cells due to the dysregulated bone marrow (BM) microenvironment leading to progressive splenomegaly. Several recent data have emphasized the role of several cytokines for splenic EMH. Alteration of CXCL12/CXCR4 pathway could also lead to splenic EMH by migrated clonal hematopoietic cells from BM to the spleen. Moreover, low Gata1 expression was found to be significantly associated with the EMH. Several gene mutations were found to be associated with significant splenomegaly in MF. In recent data, JAK2V617F homozygous mutation was associated with a larger spleen size. In other data, CALR mutations in MF were signigicantly associated with longer larger splenomegaly-free survivals than others. In addition, MF patients with ≥1 mutations in AZXL1, EZH1 or IDH1/2 had significantly low spleen reduction response in ruxolitinib treatment. Developments of JAK inhibitors, such as ruxolitinib, pacritinib, momelotinib, and febratinib enabled the effective management in MF patients. Especially, significant spleen reduction responses of the drugs were demonstrated in several randomized clinical studies, although those could not eradicate allele burdens of MF.

Emerging drugs for the treatment of Myelofibrosis.

INTRODUCTION: Myelofibrosis (MF) is a Philadelphia chromosome-negative myeloproliferative neoplasm (MPN). It can be sub-categorized into primary myelofibrosis, post polycythemia vera myelofibrosis and post essential thrombocythemia myelofibrosis. MF is a life-threatening hematologic malignancy characterized by dysregulation of the Janus associated kinase (JAK)/signal transducer and activator of transcription (STAT) signaling network and a heightened inflammatory state. Areas covered: We cover the pathogenesis, clinical features, new prognostic models, current treatment of MF and discuss agents in development. We also cover market review and health care costs associated with some of these therapies. Expert opinion: There are many ongoing clinical trials evaluating novel therapeutic approaches, including selective JAK inhibitors, histone deacetylase/DNA methyltransferase inhibitors, PI3K-inhibitors, Hedgehog/mammalian target of rapamycin (MTOR) inhibitors, anti-fibrotic agents, immunomodulators, monoclonal antibodies and immune checkpoint inhibitors. Ruxolitinib, a potent oral JAK1/JAK2 inhibitor remains the only Food and Drug Administration (FDA)-approved medicinal therapy for the treatment of MF. Unmet needs include alleviation of limiting thrombocytopenia and anemia, halting disease progression to acute leukemia, and extending survival. The development of biomarker driven clinical trials of mechanism based novel therapeutics will usher in a new era of advances in the treatment of this chronic and progressive myeloid malignancy.

Progression of primary myelofibrosis to polycythemia vera: A case report.

RATIONALE: This case report describes the progression of primary myelofibrosis (PMF) to polycythemia vera (PV), and discuss its potential mechanisms. PATIENT CONCERNS: The patient was admitted because of abdominal discomfort and enlarged spleen for 19 months. DIAGNOSIS: A case of PMF progressed to PV was retrospectively analyzed. There were 19 months between the diagnosis of PMF and PV. The JAK2 V617F mutation was positive before and after the diagnosis of PV; however, new chromosomal abnormalities were detected during the progression. INTERVENTIONS: For treatment of PMF, the danazol, calcitriol, and thalidomide were given. Then, the use of thalidomide and calcitriol was stopped, and hydroxyurea was started. For treatment of PV, interferon treatment was given, whereas hydroxyurea was continued. OUTCOMES: After 30 months of the progression (at the recent follow-up), this patient had no obvious symptoms or thrombosis. LESSONS: PMF rarely progresses to PV, however, the progression will significantly improve the quality of life and prognosis.

The Amelioration of Myelofibrosis with Thrombocytopenia by a JAK1/2 Inhibitor, Ruxolitinib, in a Post-polycythemia Vera Myelofibrosis Patient with a JAK2 Exon 12 Mutation.

Less than 5% of patients with polycythemia vera (PV) show JAK2 exon 12 mutations. Although PV patients with JAK2 exon 12 mutations are known to develop post-PV myelofibrosis (MF) as well as PV with JAK2V617F, the role of JAK inhibitors in post-PV MF patients with JAK2 exon 12 mutations remains unknown. We describe how treatment with a JAK1/2 inhibitor, ruxolitinib, led to the rapid amelioration of marrow fibrosis, erythrocytosis and thrombocytopenia in a 77-year-old man with post-PV MF who carried a JAK2 exon 12 mutation (JAK2H538QK539L). This case suggests that ruxolitinib is a treatment option for post-PV MF in patients with thrombocytopenia or JAK2 exon 12 mutations.

A case-based discussion of clinical problems in the management of patients treated with ruxolitinib for myelofibrosis.

Ruxolitinib is a dual janus kinase 1 (JAK1)/JAK2 inhibitor used to treat splenomegaly and symptoms associated with myelofibrosis (MF). Current therapeutic options for symptomatic MF include supportive care, myelosuppressive therapy (such as hydroxycarbamide) and janus kinase (JAK) inhibitors (in particular ruxolitinib). Allogeneic stem cell transplantation remains the only potentially curative treatment for MF, and younger transplant-eligible patients should still be considered for allogeneic stem cell transplantation; however, this is applicable only to a small proportion of patients. There is now increasing and extensive experience of the efficacy and safety of ruxolitinib in MF, both in clinical trials and in 'real-world' practice. The drug has been shown to be of benefit in intermediate-1 risk patients with symptomatic splenomegaly or other MF-related symptoms, and higher risk disease. Optimal use of the drug is required to maximise clinical benefit, requiring an understanding of the balance between dose-dependent responses and dose-limiting toxicities. There is also increasing experience in the use of ruxolitinib in the pre-transplantation setting. This paper aims to utilise several 'real-life' cases to illustrate several strategies that may help to optimise clinical practice.