AL amyloidosis clonal plasma cells are regulated by microRNAs and dependent on anti-apoptotic BCL2 family members.

BACKGROUND: Noncoding RNAs such as microRNAs (miRNAs) have attracted attention as biological pathway regulators, which differ from chromosomal translocations and gene point mutations. Their involvement in the molecular mechanisms underlying light chain (AL) amyloidosis pathogenesis is yet to be elucidated. AIMS: To decipher specific miRNA expression profile in AL-amyloidosis and to examine how miRNAs are involved in AL pathogenesis. METHODS: The expression profile of miRNAs and mRNA from bone marrow (BM)-derived CD138+ cells were determined using the NanoString nCounter assay and RNA-Seq, respectively. The effect of aberrantly expressed miRNAs on potential molecular targets was analyzed by qRT-PCR, Western blot, Mito-potential assay, and Annexin-PI staining. RESULTS: Genes which were significantly differentially expressed between AL-amyloidosis and MM, were found to be involved in cell growth and apoptotic mechanisms. Specifically, BCL2L1, MCL1, and BCL2 were upregulated in AL-amyloidosis compared with MM and controls. The levels of miR-181a-5p and miR-9-5p, which regulate the above-mentioned genes, were lower in BM samples from AL-amyloidosis compared with controls, providing a mechanism for BCL2 family gene upregulation. When miR-9-5p and miR-181a-5p were overexpressed in ALMC1 cells, BCL2L1, MCL1, and BCL2 were downregulated and induced apoptosis. Treatment of ALMC-1 cells with venetoclax, (BCL-2 inhibitor), resulted in the upregulation of those miRNAs, the downregulation of BCL2, MCL1, and BCL2L1 mRNA and protein levels, and subsequent apoptosis. CONCLUSION: Our findings suggest that miR-9-5p and miR-181a-5p act as tumor-suppressors whose downregulation induces anti-apoptotic mechanisms underlying the pathogenesis of AL-amyloidosis. The study highlights the post-transcriptional regulation in AL-amyloidosis and provides pathogenetic evidence for the potential use of BCL-2 inhibitors in this disease.

Mitigating the interference of Daratumumab with immunofixation electrophoresis. A single-center experience using Hydrashift 2/4 kit.

BACKGROUND: Multiple myeloma (MM) accounts for approximately 10% of hematological malignancies. The monoclonal immunoglobulin G kappa (IgG-κ) daratumumab can bind to CD38 on MM cells and be detected in serum immunofixation (IF), causing pitfalls in M-protein quantification. OBJECTIVES: To determine the efficacy of mitigating the interference of IgG MM treated with daratumumab. METHODS: Levels of Ig, free light chains (FLC) kappa (κ) and lambda (λ), serum protein electrophoresis (SPE)/IF, and Hydrashift 2/4 assays were assessed following manufacturer's instructions in three patients. RESULTS: Patient 1 was a 70-year-old male diagnosed with IgG-λ MM. The IF distinguished two monoclonal bands (IgG-κ and IgG-λ). With the Hydrashift assay, the daratumumab-anti-daratumumab immune complex shifted the IgG-κ to the α zone, suggesting that the monoclonal IgG-κ band corresponded to daratumumab. Patient 2 was a 63-year-old male with IgG-κ MM who was receiving daratumumab once every other week. SPE/IF assay revealed a faint monoclonal IgG-κ band in the  zone. A stronger monoclonal band was observed after administration. The IgG-κ band disappeared on the Hydrashift assay, while the daratumumab-anti-daratumumab complex appeared as a broad smear in the α-region. Patient 3, a 63-year-old male diagnosed with IgG-λMM, was receiving daratumumab once every other month. The IF assay showed two distinct bands (IgG-κ and IgG-λ) post-daratumumab administration. The shift to the α zone of the IgG-κ bands on the Hydrashift assay confirmed that the additional band observed post-infusion was due to the daratumumab. CONCLUSIONS: The Hydrashift assay can help distinguish daratumumab from endogenous M-spike.

Effective Neutralization of Daratumumab Effects on Pre-Transfusion Testing: a Method Modification.

BACKGROUND: The anti-CD38 antibody daratumumab is a common multiple myeloma treatment. As the erythrocyte's membrane expresses CD38, Daratumumab-treated samples show agglutination in serological pre-transfusion tests, hindering detection of erythrocyte alloantibodies. Dithiothreitol interferes with erythrocyte antigens, affecting investigation of unexpected antibodies. DARAEx®, an anti-CD38 neutralizing agent, overcomes daratumumab-induced effects, without dithiothreitol's interferences. DARAEx® is applied only in Biorad columns. This study aimed to provide a DARAEx® protocol for application with the Grifols platform. METHODS: We introduced a modified DARAEx® protocol (AssutaBB protocol) and performed antibody screenings on samples from nineteen daratumumab-treated patients. RESULTS: The AssutaBB protocol provided antibody screen results for all patients, exactly as established in the default manufacturing protocol. Eleven patients presented natural negative antibody screens; eight presented positive K/E antibodies. CONCLUSIONS: AssutaBB allows the use of the more widespread Grifols platform in daratumumab-treated patients.

Recent advances in the treatment of polycythemia vera.

Polycythemia vera (PV) has long been recognized as a disease characterized by excess blood cell production leading to thromboembolic phenomena. While the focus of treatment is on prevention of thromboembolic complications, achieved by hematocrit control and administration of low dose aspirin, attention has begun to shift to other elements of this chronic neoplasm, namely symptom control and arrest of disease progression. Clearly, phlebotomy is not able to accomplish these goals, and the ability of cytoreductive agents such as hydroxyurea (HU), to influence these elements of the disease is limited. Novel and repurposed drugs have recently entered this space, based on promising initial studies demonstrating their effects on biologic outcomes such as JAK2 V617F variant allele frequency (VAF). In this review, we present updated results of randomized clinical trials of pegylated interferon (IFN) and ruxolitinib and summarize emerging data from early phase trials of novel agents in PV.

Characteristics and recognition of early infections in patients treated with commercial anti-CD19 CAR-T cells.

The characteristics of infections following chimeric antigen receptor T (CAR-T) cells targeting CD19 in real-word population are obscure. We analyzed infections' characteristics in the first month among consecutive patients with diffuse large B-cell lymphoma (DLBCL) (n = 60, median age, 69.3 years), treated with commercial CAR-T cells. ECOG performance status (PS) was 2-3 in most patients (58%). Infections were observed in 45% of patients (16, 27%, bacterial infections, and 14, 23%, viral infections). Bacterial infection included clinically documented infection in 7 (Pneumonia, n = 5; periodontal infection, n = 1; and cellulitis, n = 1) and microbiology documented infection (MDI) in 9 patients (Gram-negative rod, n = 5; Gram-positive cocci, n = 3, bacteremia; polymicrobial, n = 1). The most common viral infection was cytomegalovirus (CMV) reactivation (n = 10, 17%) leading to initiation of anti-CMV treatment in 6 (60%) among these patients. None had CMV disease. In univariate analysis, immune effector cell-associated neurotoxicity syndrome (ICANS) was associated with higher incidence of bacterial infection (OR=4.5, P = .018), while there was a trend for lower incidence of bacterial infections in patients with chemosensitive disease to bridging therapy (OR=0.375, P = .074). Age or PS was not associated with increased risk of bacterial infection. Increase in C-reactive protein (CRP) prior to fever onset was associated with microbiologically documented infections. We conclude that infections are common in the first month following CAR-T-cell administration, however, were not increased in elderly patients or those presenting with poorer PS. Increase in CRP prior to fever onset could support infection over cytokine release syndrome.

[PROLONGED POST-COVID-19 ANEMIA].

INTRODUCTION: In February 2020, the World Health Organization (WHO) designated Covid-19 as a global pandemic, resulting in a growing population of individuals with a wide range of persistent symptoms after acute SARS-CoV-2 infection. According to the categories proposed by the WHO, the symptoms can be regarded as post-Covid if they developed during or after the Covid-19, continue >2 months and are not explained by an alternative diagnosis. Common persistent symptoms include fatigue, dyspnea, and decreased exercise capacity. Even though at diagnosis Covid- 19 has prominent hematologic manifestations, they mostly resolve after recovery from acute illness. We present a case of a 58-year-old male, without prior medical conditions, who developed a profound and prolonged anemia following mild Covid-19.

Venetoclax combinations induce high response rates in newly diagnosed acute myeloid leukemia patients ineligible for intensive chemotherapy in routine practice.

Combinations of the BCL-2 inhibitor, venetoclax, with either hypomethylating agents (HMA) or low dose cytarabine (LDAC), have shown promising results in clinical trials of AML patients unfit for intensive therapy. We report on the efficacy and safety of venetoclax combinations in AML patients treated outside of clinical trials. Complete remission (CR) + CR with incomplete count recovery (CRi) were achieved in 61% of patients, with similar CR+CRi rates in with secondary AML, and in patients who were previously treated with HMA (61% and 43%, respectively). Relapse occurred in 25% of patients, with a median event-free survival (EFS) of 11.7 months (95% CI, 10.09-13.35) in responding patients. At a median follow up of 8.7 months, the median overall survival (OS) was 9.8 months (95% CI 6.42-13.3) in the entire cohort. In multivariate analysis adverse karyotype was the only negative predictor of CR/CRi (p = .03), while both ECOG performance status (PS) and adverse karyotype were significantly associated with shorter OS (p = .023 and .038, respectively). Median OS was higher in patients achieving CR/CRi and in patients proceeding to allogeneic stem cell transplantation (allo-SCT). Treatment was well tolerated, with side effects similar to those described in the randomized clinical trials. Tumor lysis syndrome (TLS) occurred in 12% of patients. Our data support the efficacy and safety of venetoclax combinations in newly diagnosed AML patients not eligible for intensive therapy. According to our data, secondary AML patients could benefit from venetoclax combinations similarly to de-novo AML patients, and allo-SCT could be offered to selected patients achieving CR/CRi.

Multiple Myeloma Presenting in Patients Younger than 50 Years of Age: A Single Institution Experience.

INTRODUCTION: Multiple myeloma (MM) is uncommon in persons younger than 50 years of age. The presenting features in this age group are unclear. METHODS: We analyzed a cohort of patients <50 years of age with MM treated in our center. RESULTS: Twenty-three patients at a median age of 41.5 years (range 27-49) were analyzed. Patients presented at International Staging System (ISS) I-II (79%), had high frequency of bone lytic lesions (89%), extramedullary disease (26%), light-chain myeloma (45%), and translocation t(11;14) (68%). The subpopulation of patients carrying t(11;14) were younger (p = 0.025). This subgroup had higher bone marrow infiltration of plasma cells (75 vs. 47.5%), higher incidence of proteinuria (2.9 vs. 0.19 g/day), and poorer response to therapy: 85.7% of patients achieving complete/very good partial remission after induction therapy did not have t(11;14). A trend toward inferior progression-free survival (PFS) was observed in patients with t(11; 14) compared to patients without this translocation (median PFS 18 and 36 months, respectively). DISCUSSION/CONCLUSION: Translocation t(11; 14) seems to be more prevalent in young myeloma patients. Young myeloma patients and especially those who harbor translocation t(11; 14) may represent a distinct clinical entity that confers a poor outcome.

Kidney disease and plasma cell dyscrasias: ambiguous cases solved by serum free light chain dimerization analysis.

BACKGROUND: Plasma cell dyscrasias (PCD) comprise a wide spectrum of disorders, which may adversely affect the kidney. However, in some PCD cases associated with kidney disease, the routine laboratory tests may be incapable to determine precisely the form of PCD, i.e., benign or malignant. Moreover, the kidney biopsy needed for precise diagnosis may be risky or declined. To overcome these limitations, we have developed and reported a new non-invasive technique based on serum free light chains (FLC) monomer (M) and dimer (D) pattern analysis (FLC MDPA), which allowed differentiation between malignant and benign PCD forms. The objective of our retrospective study was to demonstrate the utility of FLC MDPA in solving ten puzzling PCD cases complicated with kidney disease (patients 1-10). METHODS: Ten patients with uncertain form of PCD or with a questionable response to treatment were studied. In addition to routine laboratory tests and clinical evaluation of the PCD patients, our previously developed FLC MDPA in sera and biochemical amyloid typing in biopsy tissues were applied. RESULTS: The FLC MDPA aided the diagnosis of the PCD underlying or accompanying the kidney disease in patients 1-5, and helped to interpret properly the response to treatment in patients 1, 6-10. The FLC MDPA findings were confirmed by a biochemical analysis of tissue amyloid deposits and subsequently by the outcome of these patients. CONCLUSIONS: FLC MDPA is a non-invasive diagnostic test useful in the management of ambiguous cases of PCD associated with kidney disease.

Newly diagnosed multiple myeloma patients carrying monoallelic deletion of the whole locus of immunoglobulin heavy chain gene have a better prognosis compared to those with t(4;14) and t(14;16).

The current study evaluated the prognostic significance of the monoallelic deletion of the whole locus of the immunoglobulin heavy-chain (w_del(IGH)) gene compared to translocations t(4;14) and t(14;16) among newly diagnosed multiple myeloma (MM) patients. We retrospectively analyzed clinical (age, gender, and staging) and laboratory data at diagnosis and the overall survival (OS) of 255 newly diagnosed MM patients carrying w_del(IGH) or translocations t(4;14) or t(14;16). Bone marrow samples were examined by morphological and sequential interphase fluorescense in situ hybridization analyses. Among 255 patients, 117 (45.8%) had w_del(IGH), 99 (38.8%) had t(4;14), and 39 (15.3%) had t(14;16). Mean age was 61.6 ± 11.6 years. Groups did not differ significantly in age, gender, or lactate dehydrogenase levels. Patients in the w_del(IGH) group presented more frequently at International Staging System stage I than at stage II/III. Patients in the w_del(IGH) group had significantly fewer additional chromosomal aberrations (1.58) than the other two groups (2.3 and 2.13 in the del(IGH), t(14;16) and t(4;14) groups, respectively, P < 0.0001). Furthermore, the w_del(IGH) group had significantly longer estimated median OS (9.47 years) compared to those with translocations t(14;16) (3.02 years, P = 0.002) or t(4;14) (4.18 years, P = 0.001), respectively. These findings suggest a potential prognostic significance of monoallelic deletion of IGH among these patients. Additional studies are needed to better understand the nature and mechanism of this prognostic factor.

STK405759 as a combination therapy with bortezomib or dexamethasone, in in vitro and in vivo multiple myeloma models.

Multiple myeloma (MM) remains an incurable hematological malignancy. Combination regimens of conventional and novel drugs have improved patient's survival. However, most patients inevitably relapse and become refractory to the current therapeutic armamentarium. We investigated the efficacy of combining the microtubule-targeting agent STK405759 with dexamethasone or bortezomib in vitro and in vivo. STK405759 combined with dexamethasone or bortezomib had synergistic cytotoxic activity in RPMIS, CAG and MM1.S human MM cell lines through activation of caspase 2, 3, 8, 9 and PARP. These treatments remained cytotoxic in the presence of bone marrow stroma cells. In other MM cells, including cells resistant to vincristine, melphalan, mitoxantrone or dexamethasone, these combinations decreased significantly survival as compared to single agents. In in vivo studies, STK405759 disrupted existing blood vessels in xenograft tumors, acting not only as a cytotoxic agent but also as an anti-angiogenic drug. Mice treated with STK405759 in combination with dexamethasone or bortezomib resulted in greater tumor growth inhibition, increased overall response and prolonged survival as compared to as compared to BTZ or DEXA alone. Their anticancer activity was mediated by activation of apoptosis and reduction of tumor microvessel density. These preclinical studies provide the rationale for future clinical trials of STK405759, dexamethasone and bortezomib combinations to improve the outcome of multiple myeloma patients.

Role of oral examination in newly diagnosed multiple myeloma patients: A safe and simple way to detect light chain amyloidosis.

OBJECTIVE: Up to 30% of multiple myeloma (MM) patients have subclinical amyloid deposits. These patients are under-recognized and are more susceptible to drug toxicity, bleeding and death. Early diagnosis and adjustment of treatment are crucial. Biopsies of oral mucosa might be a potentially useful diagnostic tool. The objective of this study was to assess the prevalence and characteristics at presentation of oral amyloidosis in a large cohort of MM patients. METHODS: The prevalence and characteristics of oral amyloidosis in a large cohort of MM patients who were referred for oral evaluation before and during bisphosphonate therapy were assessed, retrospectively. RESULTS: Among 212 patients analysed, 13 (6%) were diagnosed with concomitant light chain (AL) amyloidosis. In 54% (n = 7), lesions in the oral cavity compatible with amyloid deposition were detected by examination. CONCLUSIONS: The salient feature of this study is the high prevalence of oral manifestations among MM patients with amyloidosis. These results highlight the value of routine oral cavity examination and biopsy as a safe and simple method for detecting light chain amyloidosis.

Gastrointestinal perforation in light chain amyloidosis in the era of novel agent therapy - a case series and review of the literature.

Gastrointestinal (GI) perforation is remarkably rare in patients with light chain (AL) amyloidosis and has not yet been reported in patients with AL amyloidosis treated with novel agents. Only 24 cases of GI perforation have previously been reported in the setting of AL amyloidosis of which 15 had available information in English. All 15 did not receive novel agent therapy and six died early after experiencing GI perforation. This study reports the characteristics and outcome of AL patients that developed GI perforation in the era of novel agent treatment. Seven patients were reviewed. In two patients, GI perforation was the presenting symptom of AL amyloidosis, whereas five patients developed GI perforations following initiation of an anti-AL therapy (three after bortezomib-based, 1 after lenalidomide-based and 1 after thalidomide-based therapy). All patients underwent surgery and survived the perforation. Treatment was renewed following surgery in six of seven patients, with no further GI complications. In conclusion, GI perforation in AL amyloidosis is rare and mostly reported after treatment initiation. Urgent surgery appears to be lifesaving and renewal of the anti-AL novel therapy appears to be safe, with no significant risk for re-perforation or GI toxicity. Prognosis in these patients is related to severity of the disease and response to therapy rather than the development of GI perforation.

Obesity and related risk of myeloproliferative neoplasms among israeli adolescents.

OBJECTIVE: Obesity has been associated with various malignancies, but a clear association between overweight and myeloproliferative neoplasms (MPN) has not been established. METHODS: This study assessed the association between adolescent obesity and future risk for MPN. Data on 2,516,256 Israeli adolescents, who underwent a compulsory general health examination at ages 16 to 19, between 1967 and 2011, were linked to the National Cancer Registry in this nationwide, population-based cohort study. Cox proportional hazards models were used to estimate the hazard ratio (HR) for MPN associated with BMI measured at adolescence. RESULTS: The mean follow-up of 19.86 ± 12.15 years reflected 49,977,521 person years, during which 433 examinees developed MPN, primarily chronic myelogenous leukemia, polycythemia vera, and essential thrombocythemia. Obesity (BMI ≥ 95th percentile) in adolescence significantly predicted increased risk of MPN with HR (adjusted for sex) of 1.81 (95% confidence interval 1.13-2.92, P = 0.014). CONCLUSIONS: Adolescent obesity might be related to an increased incidence of myeloproliferative neoplasms.

Thrombin generation as a predictor of thromboembolic events in multiple myeloma patients.

BACKGROUND: Multiple myeloma (MM) is characterized by an increased incidence of thromboembolic events, especially when immunomodulatory drugs are used. Currently, our ability to predict these thrombotic events is limited. We hypothesized that global coagulation tests may be predictive of thrombotic events in MM patients. METHODS: Blood samples were taken from 36 MM patients before and during routine treatment. Thrombin generation (TG) tests including endogenous thrombin potential (ETP) and peak height were analyzed. RESULTS: Patients were followed for a median of 2.5years. Those who developed thrombotic events were characterized by significantly higher ETP and peak height values compared to those who did not (P=0.001). In these patients, we identified a gradual increase in TG parameters that preceded the thrombotic event. Anticoagulation therapy was associated with a significant decrease in ETP and peak height values (P<0.001). There was no statistically significant difference in TG parameters between newly diagnosed MM patients and healthy subjects, as well as between MM patients prior to and during chemotherapy. CONCLUSIONS: TG tests might predict thrombotic events in MM patients. Thus, TG tests may be incorporated into decision-making protocols of prophylactic anticoagulant therapy in MM patients.

The novel compound STK405759 is a microtubule-targeting agent with potent and selective cytotoxicity against multiple myeloma in vitro and in vivo.

Despite advances in treatment, multiple myeloma (MM) remains incurable. Here we propose the use of STK405759, a novel microtubule targeting agent (MTA) and member of the furan metotica family for MM therapy.STK405759 inhibited tubulin polymerization in a cell-free system and in myeloma cells. This molecule had potent cytotoxic activity against several MM cell lines and patient-derived MM cells. Moreover, STK405759 demonstrated cytotoxicity against drug-resistant myeloma cells that overexpressed the P-glycoprotein drug-efflux pump. STK405759 was not cytotoxic to peripheral blood mononuclear cells, including activated B and T lymphocytes. This compound caused mitotic arrest and apoptosis of myeloma cells characterized by cleavage of poly (ADP-ribose) polymerase-1 and caspase-8, as well as decreased protein expression of mcl-1. The combination of STK405759 with bortezomib, lenalidomide or dexamethasone had synergistic cytotoxic activity. In in vivo studies, STK405759-treated mice had significantly decreased MM tumor burden and prolonged survival compared to vehicle treated- mice.These results provide a rationale for further evaluation of STK405759 as monotherapy or part of combination therapy for treating patients with MM.

Translocation t(11;14) in newly diagnosed patients with multiple myeloma: Is it always favorable?

The most common translocation in multiple myeloma (MM) is t(11;14)(q13;q32). According to several studies, this translocation represents a unique subset of patients with relatively favorable outcomes. Using combined analyses of morphology and fluorescence in situ hybridization (I-FISH), we examined the co-occurrence rates of t(11;14) with seven chromosomal aberrations (CAs), del(13q), del(17p), del(1p), gain(1q), multiple gains(1q), del(16q), and del(IGH), and assessed the effect of the different combinations on patient outcomes, with overall survival (OS) as the main outcome measure. Bone marrow samples and clinical data from 212 patients with MM with t(11;14) were analyzed. At least two additional CAs were found in 35% (75/205) of patients and a strong correlation between specific CAs. The occurrence of three CAs [multiple gains of (1q) (HR = 6.94, P = 0.001), del(1p) (HR = 4.47, P = 0.008), and del(IGH) (HR = 2.38, P = 0.002)] exerted a profoundly deleterious effect on median OS when compared with patients with t(11;14) only. Del(17p) and del(13q) have also exerted a deleterious effect albeit to a lesser extent (HR = 2.05, P = 0.07 and HR = 1.81, P = 0.03, respectively). When compared with t(11;14) alone, the addition of certain CAs lead to worse outcomes. These findings may have important clinical and biological implications. Patients with coexisting adverse lesions and t(11;14) may be considered at high risk and managed accordingly. © 2016 Wiley Periodicals, Inc.

Ruxolitinib treatment for myelofibrosis: Efficacy and tolerability in routine practice.

Ruxolitinib has been shown in two randomized clinical trials to be effective in alleviating systemic symptoms and reducing spleen size in patients with myelofibrosis (MF). We retrospectively evaluated efficacy and tolerability of ruxolitinib in a cohort of unselected MF patients treated in routine clinical practice. One hundred and two patients who began ruxolitinib therapy were identified in 13 participating centers. Ninety three of the patients receiving ruxolitinib for at least 3 months were evaluated for treatment efficacy and toxicity. Median age at ruxolitinib initiation was 67 years. Indications for treatment were constitutional symptoms (15%), symptomatic splenomegaly (6%) or both (76%). Two patients received ruxolitinib for other indications. The median initial ruxolitinib dose was 30mg/day. Median duration of therapy was 11 months. Eighty two patients (88.2%) responded to therapy, 76 (84.4%) patients had improvement in constitutional symptoms and 60 patients (70.6%) had reduction in spleen length. While on ruxolitinib, 30% of patients had grade 3-4 anemia and 12.9% of patients had grade 3-4 thrombocytopenia. Thirteen patients (14%) discontinued therapy. This analysis of a cohort of MF patients treated with ruxolitinib in routine clinical practice demonstrates the efficacy and tolerability of this drug outside of a highly monitored clinical trial setting.

Pathogenesis of myeloproliferative neoplasms.

Major progress has been recently made in understanding the molecular pathogenesis of myeloproliferative neoplasms (MPN). Mutations in one of four genes-JAK2, MPL, CALR, and CSF3R-can be found in the vast majority of patients with MPN and represent driver mutations that can induce the MPN phenotype. Hyperactive JAK/STAT signaling appears to be the common denominator of MPN, even in patients with CALR mutations and the so-called "triple-negative" MPN, where the driver gene mutation is still unknown. Mutations in epigenetic regulators, transcription factors, and signaling components modify the course of the disease and can contribute to disease initiation and/or progression. The central role of JAK2 in MPN allowed development of small molecular inhibitors that are in clinical use and are active in almost all patients with MPN. Advances in understanding the mechanism of JAK2 activation open new perspectives of developing the next generation of inhibitors that will be selective for the mutated forms of JAK2.