Blast-phase Myeloproliferative Neoplasms Research Articles

CD123 As a Therapeutic Target in Accelerated and Blast Phase Myeloproliferative Neoplasms (MPNs)

CD123 As a Therapeutic Target in Accelerated and Blast Phase Myeloproliferative Neoplasms (MPNs)

Outcomes of intensive and nonintensive blast-reduction strategies in accelerated and blast-phase MPN

AbstractTransformation of BCR::ABL1-negative myeloproliferative neoplasms (MPN) to an accelerated or blast phase is associated with poor outcomes. The efficacy of acute myeloid leukemia (AML)–type intensive and nonintensive hypomethylating agent–based regimens is not well studied. We therefore performed a retrospective analysis of patients with MPN-AP/BP (N = 138) treated with intensive (N = 81) and nonintensive (N = 57) blast-reduction strategies. We used clinically relatable response criteria developed at the Princess Margaret Cancer Centre. The overall best response, comprising complete remission (CR), complete remission with incomplete hematologic recovery (CRi), and reversion to chronic phase MPN (cMPN), in the intensive and nonintensive groups was 77% (62 of 81) and 39% (21 of 54), respectively. Similar overall best response rates were observed in patients receiving induction with daunorubicin combined with cytarabine arabinoside (daunorubicin + ara-C) (74% [23 of 31]) or FLAG-IDA/NOVE-HiDAC (78% [39 of 50], P = .78). However, patients receiving daunorubicin + ara-C more often required second inductions (29% [9 of 31] vs 4% [2 of 50], P = .002). Most responses in the entire cohort were reversions to cMPN (55 of 83 [66%]). CR and CRi comprised 30% (25 of 83) and 4% (3 of 83) of responses, respectively. Mutations in TP53 (overall response [OR] 8.2 [95% confidence interval [CI] 2.01, 37.1], P = .004) and RAS pathway (OR 5.1 [95%CI 1.2, 23.7], P = .03) were associated with inferior treatment response for intensively treated patients, and poorer performance status (Eastern Cooperative Oncology Group) was associated with inferior treatment response in both intensively (OR 10.4 [95% CI 2.0, 78.5], P = .009) and nonintensively treated groups (OR 12 [95% CI 2.04, 230.3], P = .02). In patients with paired samples before and after therapy (N = 26), there was a significant residual mutation burden remaining irrespective of response to blast-reduction therapy.

CD123 As a Therapeutic Target in Accelerated and Blast Phase Myeloproliferative Neoplasms (MPNs)

Background: CD123 expression in MPNs has been reported in case series and CD123 has been a therapeutic target in one phase I study of patients with chronic myelomonocytic leukemia or myelofibrosis in chronic phase. CD123 has also been described as a marker of leukemic stem cells and incorporated in chimeric antigen receptor T-cell products for treatment of acute myeloid leukemia in clinical trials. Herein, we describe the clinical phenotype of patients with accelerated (AP) or blast phase (BP) MPNs paired with CD123 co-expression on CD45(dim) myeloid blasts. Methods: This is a retrospective, single-institution study of patients with AP and BP MPNs. Subjects were identified by search for MPN diagnoses in the Ohio State University Comprehensive Cancer Center Leukemia Tissue Bank (OSUCCC-LTB). Relevant clinical data was collected by retrospective chart review with approval of Institutional Review Board. CD123 expression was measured by immunophenotyping of cryopreserved peripheral blood (PB) or marrow (BM) samples. Blasts were identified by CD45(dim) gating of lymphocytes. Lymphocytes were also gated on CD7, CD13, CD33, CD34, and CD117. CD123 expression was stratified by quartile and correlation with disease phase, symptoms, splenomegaly, transfusion-dependence, and molecular mutations measured by Chi-square test. Results: Forty-one PB or BM samples from 24 subjects were identified from the OSUCCC-LTB. Nine subjects had paired PB and BM specimens and 6 subjects had samples obtained at multiple timepoints in the course of their disease. Median age at time of sample collection was 65.8 years (range 35.2-79.7) and median time from initial diagnosis to sampling was 13.1 months (range 0-96.5). Constitutional symptoms were present at the time of collection in 24 specimens (58.5%) and splenomegaly present in 20 specimens (51.3%). At sample collection, 19.5% had never received treatment, 19.5% had been previously treated, and 61% were currently on treatment. Most patients on treatment (n=16, 64%) were receiving JAK inhibitor at sample collection. Nineteen samples were obtained in chronic phase (46.3%), nine in AP (22.0%), and thirteen in BP (31.7%). Median WBC count was 4.37K/uL (range 0.3-174.6), median peripheral blasts were 3.2% (range 0-76%), median hemoglobin was 8.8 g/dL (range 5.6-13.2), and median platelets were 42K/uL (range 5-564). Sixteen samples (39.0%) were from transfusion-dependent patients, of which, 68.8% were both red blood cell (RBC) and platelet transfusion-dependent, 25.0% were RBC transfusion-dependent only, and 6.2% were platelet transfusion-dependent only. Median lactate dehydrogenase at time of sampling was 300 U/L (range 116-2,142). Median bone marrow blasts at time of sampling were 3% (range 0-82%). Molecular sequencing and karyotype +/- 30 days of sample collection were available for 18 (43.9%) and 27 (65.9%) of specimens, respectively. The most common mutations identified were JAK2 (50%), ASXL1 (27.8%), SRSF2 (22.2%), CALR (16.7%), and TP53 (16.7%). Normal karyotype was reported in 37% of the samples (one was consistent with donor chimerism post-allogeneic SCT), 33.3% had complex karyotype, 11.1% had del 5q or 7q/-7, and 18.5% had del 13q or 20q. CD123 expression on the CD45(dim) gated blasts ranged from 0.3-95.6% with a median value of 11.02%. CD123 expression is presented in figure 1 box plot. Figure 2a shows correlation between CD123 expression and AP/BP compared to chronic phase disease (p < 0.01). Figure 2b shows CD123 expression correlation with ASXL1 compared to unmutated ASXL1 (p =0.023). There were no statistically significant associations between CD123 expression and any other tested variables. Conclusions: These single-institution data suggest that high CD123 expression on blasts is associated with leukemic transformation and high-risk disease. This is demonstrated by correlation of higher expression in AP and BP MPN as well as correlation with ASXL1 mutation. CD123 expression in MPNs has been previously reported and explored as a therapeutic target in a single phase I trial, though these data suggest that specifically targeting high risk disease, defined by blasts >10% or the presence of ASXL1 mutation, may be more effective with greater target availability. This is an especially important subpopulation of patients with MPNs in need of more effective and less toxic therapy than current standards of care that typically include cytotoxic chemotherapy.

Loss of Heterozygosity of Chromosome 9p and Progression in MPNs

Introduction Copy-neutral loss of heterozygosity (LOH) of chromosome 9p, concomitant with mutated JAK2, can occur in myeloproliferative neoplasms (MPNs), and may be the most common chromosomal aberration in patients with polycythemia vera (PV). The prevalence of LOH of 9p varies amongst the different MPNs and is highest in PV where it has been reported to be between 30-70%. The reported prevalence of LOH of 9p is 20-50% and 10-20% in patients with myelofibrosis (MF) and essential thrombocythemia (ET), respectively. A hallmark feature of MPNs is the tendency to progress to more aggressive disease phenotypes (i.e., PV/ET to MF to accelerated- or blast-phase MPN) through the acquisition or loss of cytogenetic and molecular clonal markers. Although loss of LOH of 9p likely contributes to progression in MPNs, its pathologic role is still incompletely defined. Methods We conducted a retrospective review of patients at a single-center, tertiary-care institution who were diagnosed with an MPN, either chronic, accelerated or blast-phase (MPN-AP/BP), from January 1 st, 2017 until July 1 st, 2023. All patients underwent a microarray-based chromosome analysis using the I Scan System with the Global Diversity Array-8 (GDA) v1.0 Array BeadChip. Mutational profiling was done using the NextGENe software (SoftGenetics LLC) and MiSeq Reporter, and variant annotation and filtration was performed using VarSeq (Golden Helix). Results Fifty-two patients with MF were identified. Twenty-eight patients (53.8%) were found to have LOH of 9p, 15 of whom had secondary MF (7 with preceding ET and 8 with preceding PV). Eight of 9 patients (88.9%) with PV-MF harbored LOH of 9p, vs. 6 of 13 (46.2%) with ET-MF. The median cell fraction affected was 70% (range, 5-95%) and the median JAK2 variant allele frequency (VAF) was 75% (range, 16-97%). Eleven of the 24 patients without LOH of 9p harbored JAK2 mutations, at a median VAF of 40%. Nine patients (32.2%) with LOH of 9p had abnormal cytogenetics by conventional karyotyping, compared to 8 (33.3%) without LOH of 9p. Eleven patients (39.3%) with LOH of 9p were MIPSS-70 v2 high or very high risk, compared to 10 (41.7%) patients without LOH of 9p. Nine patients (32.1%) with LOH of 9p were DIPSS-plus intermediate-2 or high-risk, compared with 9 (37.5%) patients without LOH of 9p. Twenty patients with MPN-AP/BP were identified, of whom 11 had MPN-AP and 9 had MPN-BP. Four patients (20%), all with MPN-BP, had LOH of 9p. Median JAK2 VAF in these patients was 50% (range, 38-80%), vs. 4% (range, 3-48%) in the 6 patients with JAK2 without LOH of 9p. Two of 19 patients (10.5%) with ET were found to have LOH of 9p, with a corresponding JAK2 VAF of 70% and 20%. Twelve of the 17 patients (70.6%) who did not have LOH of 9p had a JAK2 mutation, at a median VAF of 27% (range, 4-44%). One patient with LOH of 9p had a thrombotic event, vs. 4 of 17 patients (23.5%) without LOH of 9p. Three of 9 patients (33%) with PV were found to have a LOH of 9p, with a median corresponding JAK2 VAF of 61% (range, 55-81%). Median JAK2 VAF for the other 6 patients (all with a JAK2 mutation) was 34% (range, 26-46%). One patient with LOH of 9p had a thrombotic event vs. 3 of 6 patients (50%) without LOH of 9p. Discussion The highest prevalence of LOH of 9p in patients with an MPN was seen in those with MF (>50%), followed by PV, MPN-AP/BP and ET. These results are generally in line with those previously reported, though the prevalence in PV was lower than other studies (likely due to small sample size). The prevalence of LOH of 9p in ET-MF was more than four times higher than in ET, suggesting that LOH of 9p may be an acquired cytogenetic aberration involved in ET progression. LOH of 9p was seen in almost 90% of PV-MF vs. 33% of PV patients, further supporting that LOH of 9p may be implicated in MPN progression. Notably, LOH-9p was seen in far fewer patients with accelerated- or blast-phase disease. It is likely that clonal evolution of MPNs to MPN-AP/BP is driven more so by the acquisition of high-risk mutations (e.g., TP53, ASXL1, U2AF1) and less by changes such as LOH of 9p and increased JAK2 VAF. In summary, our data largely confirms previous reports regarding the prevalence of LOH of 9p in MPNs while suggesting a role for the gain or loss of LOH of 9p in the progression of these hematologic cancers.

Proof of concept of triple COMBI therapy to prohibit MPN progression to AML.

Patients with accelerated or blast phase myeloproliferative neoplasms have a dismal prognosis. The report by de Castro etal. provides important information on the rationale and prospect for a novel therapeutic approach combining interferon-alpha2 with 5-azacytidine and a JAK1-2 inhibitor (ruxolitinib) to be explored in well-designed clinical trials. Commentary on: Castro etal. Ratio of stemness to interferon signalling as a biomarker and therapeutic target of myeloproliferative neoplasm progression to acute myeloid leukaemia. Br J Haematol 2024;204:206-220.

Updates on accelerated and blast phase myeloproliferative neoplasms: Are we making progress?

Management approaches for accelerated and blast phase myeloproliferative neoplasms remain challenging for clinicians and patients alike. Despite many therapeutic advances, outcomes for those patients who are not allogeneic haematopoietic cell transplant eligible remain, in general, very poor. Estimated survival rates for such blast phase patients is frequently reported as less than 6 months. No specific immunological, genomic or clinicopathological signature currently exists that accurately predicts the risk and timing of transformation, which frequently induces a high degree of anxiety among patients and clinicians alike. Within this review article, we provide an up-to-date summary of current understanding of the underlying pathogenesis of accelerated and blast phase disease and discuss current therapeutic approaches and realistic outcomes. Finally, we discuss how the horizon may look with the introduction of more novel agents into the clinical arena.

Combination of azacitidine, venetoclax and ruxolitinib in blast phase myeloproliferative neoplasms.

Myeloproliferative neoplasms in blastic phase (MPN-BP) have a dreadful prognosis. We report the characteristics and outcomes of five MPN-BP patients treated with a never-before-described combination of azacytidine and venetoclax (to control BP transformation), added to ruxolitinib (needed to control constitutional symptoms). Median age was 76 years (range 72-84), and worst performance status was 2. The overall response rate was 80%, and the complete remission rate was 40%. With median follow-up of 10.0 months (range 4.2-13.4), median overall survival was 13.4 months (95% CI 4.2-13.4). We did not detect any unexpected treatment-related toxicity, and quality of life was improved.

Outcomes after allogeneic hematopoietic cell transplant in patients diagnosed with blast phase of myeloproliferative neoplasms: A retrospective study from the Chronic Malignancies Working Party of the European Society for Blood and Marrow Transplantation.

Allogeneic hematopoietic cell transplant (allo-HCT) provides the only potential route to long-term remission in patients diagnosed with blast phase transformation of myeloproliferative neoplasm (BP-MPN). We report on a large, retrospective European Society for Blood and Marrow Transplantation registry-based study of BP-MPN patients undergoing allo-HCT. BP-MPN patients undergoing first allo-HCT between 2005 and 2019 were included. A total of 663 patients were included. With a median follow-up of 62 months, the estimated 3-year overall survival (OS) was 36% (95% confidence interval [CI], 32-36). Factors associated with lower OS were Karnofsky Performance Score (KPS) <90 (hazard ratio [HR] 1.65, p < .001) and active disease at allo-HCT (HR 1.45, p < .001), whereas patients undergoing allo-HCT more recently associated with a higher OS (HR 0.96, p=.008). In a selected patient's population, the 3-year OS of patients undergoing allo-HCT in complete response (CR) and with a KPS ≥90 was 60%. KPS < 90 (HR 1.4, p=.001) and active disease (HR 1.44, p=.0004) were associated with a lower progression-free survival (PFS). Conversely, most recent allo-HCT associated with a higher PFS (HR 0.96, p=.008). Active disease at allo-HCT (HR 1.34, p=.03) was associated with a higher cumulative incidence of relapse (RI) and allo-HCT in earlier calendar years (HR 0.96, p=.02) associated with a lower RI. Last, KPS < 90 (HR 1.91, p < .001), active disease (HR 1.74, p=.003) and allo-HCT from mismatched related donors were associated with a higher non-relapse mortality (HR 2.66, p=.003). In this large series of BP-MPN patients, about one third were alive at 3 years after transplantation. Patients undergoing allo-HCT in the more recent era, with a KPS ≥90 and in CR at transplant had a better prognosis.

Treating accelerated and blast phase myeloproliferative neoplasms: progress and challenges.

Myeloproliferative neoplasms (MPNs) are a group of clonal hematologic malignancies that include polycythemia vera (PV), essential thrombocythemia (ET), and myelofibrosis (MF). MPNs are characterized by activating mutations in the JAK/STAT pathway and an increased risk of transformation to an aggressive form of acute leukemia, termed MPN-blast phase (MPN-BP). MPN-BP is characterized by the presence of ⩾20% blasts in the blood or bone marrow and is almost always preceded by an accelerated phase (MPN-AP) defined as ⩾10-19% blasts in the blood or bone marrow. These advanced forms of disease are associated with poor prognosis with a median overall survival (mOS) of 3-5 months in MPN-BP and 13 months in MPN-AP. MPN-AP/BP has a unique molecular landscape characterized by increased intratumoral complexity. Standard therapies used in de novo acute myeloid leukemia (AML) have not demonstrated improvement in OS. Allogeneic hematopoietic stem cell transplant (HSCT) remains the only curative therapy but is associated with significant morbidity and mortality and infrequently utilized in clinical practice. Therefore, an urgent unmet need persists for effective therapies in this advanced phase patient population. Here, we review the current management and future directions of therapy in MPN-AP/BP.

ENABLE: treatment combination including decitabine and venetoclax in acute myeloid leukemia secondary to myeloproliferative neoplasms.

The management of patients with acute myeloid leukemia (blast phase) secondary to myeloproliferative neoplasms (MPNs) is extremely challenging and the outcome dismal, with a median overall survival of about 3-6months. Effective therapeutic approaches are lacking, especially when intensive strategies followed by allogeneic transplantation are not feasible. The combination of venetoclax and hypomethylating agents has recently been established as standard for newly diagnosed, unfit patients with de novo acute myeloid leukemia, but the application of this therapeutic modality has not been tested prospectively in the specific context of blast-phase MPNs. ENABLE is an open, phase II clinical trial aimed at verifying the efficacy and safety of the combination of venetoclax and decitabine in patients with post-MPN blast phase.

Hitting the brakes on accelerated and blast-phase myeloproliferative neoplasms: current and emerging concepts

The BCR-ABL-negative myeloproliferative neoplasms (MPNs) have a variable risk of progressing to accelerated- or blast-phase MPN (MPN-AP/MPN-BP), defined by the presence of 10% to 19% and more than or equal to 20% myeloid blasts in the peripheral blood or bone marrow, respectively. The molecular processes underlying the progression to MPN-AP/MPN-BP are becoming increasingly understood with the acquisition of additional mutations in epigenetic modifiers (eg, ASXL1, EZH2, TET2), TP53, the Ras pathway, or splicing factors (eg, SRSF2, U2AF1), having been described as important steps in this evolutionary process. At least partially driven by the enrichment of these high-risk molecular features, the prognosis of patients with MPN-BP remains inferior to other patients with acute myeloid leukemia, with a median overall survival of 3 to 6 months. Allogeneic hematopoietic cell transplantation remains the only potentially curative therapeutic modality, but only a minority of patients are eligible. In the absence of curative intent, therapeutic strategies or palliative treatment with hypomethylating agents as monotherapy or in combination with ruxolitinib or venetoclax can be considered. Several novel agents are in various stages of clinical development but are not available for routine use at this point, highlighting the need for ongoing research and the prioritization of clinical trial enrollment when feasible.

Predictors of Response to Venetoclax Plus Hypomethylating Agent Therapy and Survival in Blast-Phase Myeloproliferative Neoplasm

Introduction Myeloproliferative neoplasms (MPN) with blast phase (BP) transformation (MPN-BP) are associated with shortened survival since most patients are elderly and unfit for intensive chemotherapy. Venetoclax (Ven) plus hypomethylating agent (HMA) is FDA approved for elderly/unfit acute myeloid leukemia, however MPN-BP patients were excluded from Ven+HMA clinical trials. Accordingly, in the current study, our main objective was to examine Ven+HMA treatment outcomes including the impact of karyotype and mutations on response and survival in MPN-BP. Methods Patients with MPN-BP that received Ven+HMA outside clinical trials at the Mayo Clinic between July 2018 and May 2022 were retrospectively recruited after institutional review board approval. Diagnosis of MPN-BP required the presence of ≥20% blasts in either the peripheral blood or bone marrow. Cytogenetic and molecular studies were performed by conventional karyotype, and next-generation sequencing, respectively. All patients received at least one cycle of Ven+HMA which included either azacitidine 75 mg/m2 days 1-7 or decitabine 20 mg/m2 days 1-5. Response was assessed according to the 2017 European Leukemia Net (ELN) criteria. ResultsPatient characteristics 47 patients with MPN-BP (median age 71 years, range 46-84; 60% males) received Ven+HMA either upfront (n=32) or following relapse (n=15). Antecedent MPN included ET/post-ET MF in 18 (38%), PV/post-PV MF in 16 (34%), and PMF in 13 (28%) patients. Driver mutation profile included JAK2 in 76% of the patients and CALR in 18%; other mutations included TP53 in 17 patients (39%), TET2 in 10 (23%), ASXL1 in 15 (34%), IDH1/2 in 12 (27%), EZH2 in 6 (14%), RUNX1 in 6 (14%), N/KRAS,SRSF2 and U2AF1 in 5 (11%) each. ELN cytogenetic risk was favorable (2%), intermediate (34%) or adverse (64%); among the latter, 55% were classified as complex. Response Thirty-one (66%) patients received decitabine and the remainder azacitidine with median Ven dose of 200 mg for a median of 3 cycles (range, 1-9 cycles). 21 (45%) patients experienced cycle delays/interruptions and treatment was complicated by neutropenic fever in 22 (47%) cases. CR or CRi was documented in 20 (43%) patients; 12 (26%) patients with CR and 8 (17%) with CRi, and residual morphological features of MPN were present in 10 patients. Among complete responders, median time to response was 1.7 months (range; 1-7 months), with median response duration of 5 months (range, 0.4-35 months). Relapse was documented in 9 (45%) of responding patients. Importantly, 7 of 13 (54%) transplant-eligible patients in CR/CRi, were bridged to transplant. CR/CRi rates were similar with upfront therapy or in the relapsed setting (47% vs 33%; p=0.38), azacitidine or decitabine (50% vs 39%; p=0.46), presence or absence of TP53 (41% vs 44%; p=0.83), ASXL1 (47% vs 41%, p=0.74), IDH1/2 (50% vs 41%; p=0.58), and K/NRAS mutations (20% vs 46%; p=0.25). CR/CRi was superior without vs with antecedent PV (55% vs 19%, p=0.01), presence vs absence of TET2 mutation (70% vs 35%, p=0.05), and absence of complex karyotype (60%, vs 29%, p=0.04). Multivariable analysis confirmed the favorable impact of TET2 mutation (p=0.02), and absence of antecedent PV (p=0.009) on CR/CRi. Moreover, CR/CRi was significantly higher in TET2 mutated vs unmutated patients without antecedent PV (83% vs 48%) and with antecedent PV (50% vs 9%) (p=0.01). Survival After a median follow up of 6 months (range, 1-37 months) from initiation of Ven+HMA, 31 (66%) patients have died. Median overall survival was 7 months (range; 1-37 months) and longer in transplanted patients (11 vs 6 months; p=0.04) (Figure). On univariate analysis, survival was superior in the absence of complex karyotype (10 vs 5 months, p=0.003), N/KRAS mutations (8 vs 4 months; p=0.02), with achievement of CR/CRi (10 vs 6 months; p=0.02), and transplant (11 vs 6 months, p=0.04). Multivariable analysis confirmed the favorable prognostic impact of absence of complex karyotype and N/KRAS mutations (p=0.003 and 0.03) (Figure). Conclusions The current study identifies MPN-BP patients with a higher likelihood of response (TET2 mutated without antecedent PV) and prolonged survival (absence of complex karyotype and N/RAS mutations) following treatment with Ven+HMA. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

CPX-351 for Blast-Phase Myeloproliferative Neoplasm (MPN-BP): Mayo Clinic Experience in 10 Consecutive Patients

CPX-351 for Blast-Phase Myeloproliferative Neoplasm (MPN-BP): Mayo Clinic Experience in 10 Consecutive Patients

Characterization of disease-propagating stem cells responsible for myeloproliferative neoplasm-blast phase.

Chronic myeloproliferative neoplasms (MPN) frequently evolve to a blast phase (BP) that is almost uniformly resistant to induction chemotherapy or hypomethylating agents. We explored the functional properties, genomic architecture, and cell of origin of MPN-BP initiating cells (IC) using a serial NSG mouse xenograft transplantation model. Transplantation of peripheral blood mononuclear cells (MNC) from 7 of 18 patients resulted in a high degree of leukemic cell chimerism and recreated clinical characteristics of human MPN-BP. The function of MPN-BP ICs was not dependent on the presence of JAK2V617F, a driver mutation associated with the initial underlying MPN. By contrast, multiple MPN-BP IC subclones coexisted within MPN-BP MNCs characterized by different myeloid malignancy gene mutations and cytogenetic abnormalities. MPN-BP ICs in 4 patients exhibited extensive proliferative and self-renewal capacity, as demonstrated by their ability to recapitulate human MPN-BP in serial recipients. These MPN-BP IC subclones underwent extensive continuous clonal competition within individual xenografts and across multiple generations, and their subclonal dynamics were consistent with functional evolution of MPN-BP IC. Finally, we show that MPN-BP ICs originate from not only phenotypically identified hematopoietic stem cells, but also lymphoid-myeloid progenitor cells, which were each characterized by differences in MPN-BP initiating activity and self-renewal capacity.

Comparison of Different Treatment Strategies for Blast-Phase Myeloproliferative Neoplasms

IntroductionUp to 20% of patients with myeloproliferative neoplasms (MPN) will progress to blast phase (MPN-BP). Outcomes are dismal, with intensive chemotherapy providing little benefit. Low-intensity therapy is preferred due to better tolerability, but the prognosis remains poor. Allogeneic stem cell transplant (AHSCT) is still the only potential for long term survival. Patients and MethodsTo better evaluate the initial treatment approach in MPN-BP, we performed a single-institution retrospective analysis of 75 patients with MPN-BP treated at Moffitt Cancer Center between 2001 and 2021. Patients were stratified by initial treatment: best supportive care (BSC), hypomethylating agent (HMA)-based therapy or intensive chemotherapy (IC). ResultsMedian overall survival (mOS) for the entire cohort was 4.8 months (BSC 0.8 months, HMA 4.7 months, and IC 11.4 months). Among IC patients, improved survival was evident in those that received AHSCT (mOS 40.8 months vs. 4.9 months, p < .01). Most patients that underwent AHSCT were initially treated with IC (p < .01). All patients that underwent AHSCT had achieved complete response (CR) or CR with incomplete hematological recovery (CRi). On multivariate analysis, factors associated with improved survival were receipt of therapy (HMA or IC) (P = .017), CR/CRi (P = .037) and receipt of AHSCT (p < .001). ConclusionWe show that active treatment with IC improves survival, but it is mostly tied to receipt of AHSCT. IC is a reasonable approach in appropriate patients as it can provide an effective bridge to AHSCT. Other treatment strategies such as molecularly targeted therapy and novel agents are desperately needed.

Mutational landscape of blast phase myeloproliferative neoplasms (MPN-BP) and antecedent MPN.

Myeloproliferative neoplasms (MPN) have an inherent tendency to evolve to the blast phase (BP), characterized by ≥20% myeloblasts in the blood or bone marrow. MPN-BP portends a dismal prognosis and currently, effective treatment modalities are scarce, except for allogeneic hematopoietic stem cell transplantation (allo-HSCT) in selected patients, particularly those who achieve complete/partial remission. The mutational landscape of MPN-BP differs from de novo acute myeloid leukemia (AML) in several key aspects, such as significantly lower frequencies of FLT3 and DNMT3A mutations, and higher incidence of IDH1/2 and TP53 in MPN-BP. Herein, we comprehensively review the impact of the three signaling driver mutations (JAK2 V617F, CALR exon 9 indels, MPL W515K/L) that constitutively activate the JAK/STAT pathway, and of the other somatic non-driver mutations (epigenetic, mRNA splicing, transcriptional regulators, and mutations in signal transduction genes) that cooperatively or independently promote MPN progression and leukemic transformation. The MPN subtype, harboring two or more high-molecular risk (HMR) mutations (epigenetic regulators and mRNA splicing factors) and "triple-negative" PMF are among the critical factors that increase risk of leukemic transformation and shorten survival. Primary myelofibrosis (PMF) is the most aggressive MPN; and polycythemia vera (PV) and essential thrombocythemia (ET) are relatively indolent subtypes. In PV and ET, mutations in splicing factor genes are associated with progression to myelofibrosis (MF), and in ET, TP53 mutations predict risk for leukemic transformation. The advent of targeted next-generation sequencing and improved prognostic scoring systems for PMF inform decisions regarding allo-HSCT. The emergence of treatments targeting mutant enzymes (e.g., IDH1/2 inhibitors) or epigenetic pathways (BET and LSD1 inhibitors) along with new insights into the mechanisms of leukemogenesis will hopefully lead the way to superior management strategies and outcomes of MPN-BP patients.

Venetoclax and hypomethylating agents in older/unfit patients with blastic plasmacytoid dendritic cell neoplasm

Venetoclax and hypomethylating agents in older/unfit patients with blastic plasmacytoid dendritic cell neoplasm

Molecular Progression of Myeloproliferative and Myelodysplastic/Myeloproliferative Neoplasms: A Study on Sequential Bone Marrow Biopsies.

Simple SummaryMyeloid neoplasms (MN) are malignant hematopoietic stem cell disorders, which can progress into aggressive forms of blood cancer, likely due to the acquisition of additional genetic alterations. We investigated bone marrow biopsies of MN patients who underwent progression and compared them to a cohort with stable disease course. We identified certain mutations that promote an unfavorable outcome and found that patients with a known progress harbor more genetic alterations in their MN than those who do not deteriorate. Furthermore, we underpinned the hypothesis that not only the sum of genetic alterations but also the order in which they appear matters in disease evolution. Our findings emphasize the importance of genetic testing in MN patients in order to assess their risk of progression into aggressive blood cancer.Myeloproliferative neoplasms (MPN) and myelodysplastic/myeloproliferative neoplasms (MDS/MPN) both harbor the potential to undergo myelodysplastic progression or acceleration and can transform into blast-phase MPN or MDS/MPN, a form of secondary acute myeloid leukemia (AML). Although the initiating transforming events are yet to be determined, current concepts suggest a stepwise acquisition of (additional) somatic mutations—apart from the initial driver mutations—that trigger disease evolution. In this study we molecularly analyzed paired bone marrow samples of MPN and MDS/MPN patients with known progression and compared them to a control cohort of patients with stable disease course. Cases with progression displayed from the very beginning a higher number of mutations compared to stable ones, of which mutations in five (ASXL1, DNMT3A, NRAS, SRSF2 and TP53) strongly correlated with progression and/or transformation, even if only one of these genes was mutated, and this particularly applied to MPN. TET2 mutations were found to have a higher allelic frequency than the putative driver mutation in three progressing cases (“TET2-first”), whereas two stable cases displayed a TET2-positive subclone (“TET2-second”), supporting the hypothesis that not only the sum of mutations but also their order of appearance matters in the course of disease. Our data emphasize the importance of genetic testing in MPN and MDS/MPN patients in terms of risk stratification and identification of imminent disease progression.

Navtemadlin (KRT-232), a Small Molecule MDM2 Inhibitor, Is More Effective Than Decitabine Against Myeloproliferative Neoplasm-Blast Phase in a Patient-Derived Xenograft Model

Patients with myeloproliferative neoplasm-blast phase (MPN-BP) have a particularly dismal prognosis with a median survival of less than 6 months with currently available therapies (Mesa Blood 2015). Decitabine is the standard of care for MPN-BP. Recently, using xenotransplantation assays, we have shown that MPN-BP originates at the hematopoietic stem cell (SC) level (Wang Blood 2018) and that MPN-BP CD34 + cells contain higher levels of MDM2 protein compared with their normal counterparts (% of MDM2 + CD34 + cells: MPN-BP: 76.4±3.3; Normal: 17.5±6.4. P <0.05). MDM2 negatively regulates p53 activity and MDM2 inhibitors can activate p53 and induce apoptosis of TP53 WT cancer cells. As mutations or deletions of TP53 occur infrequently in MPN-BP, we examined the effects of a potent MDM2 inhibitor, navtemadlin (KRT-232; Canon Mol. Cancer Ther. 2015) and decitabine as monotherapy or in combination on the depletion or elimination of MPN-BP cells in a patient derived xenograft (PDX) model.We firstestablished the dynamics of leukemia cell recovery following a single cycle of navtemadlin treatment. Spleen cells with wild type (WT) TP53 and mutations in KRAS, RAD21, KMT2A and ASXL1 were collected from the 4 th generation of MPN-BP PDX mice. Forty days after injection of these spleen cells (4×10 5/mouse) into sublethally irradiated NSG mice, peripheral blood (PB) leukemic burden (hCD34 + cells: 0.39±0.09%) was demonstrated by flow cytometric analysis. Mice were treated with vehicle alone (n=3) or high doses of navtemadlin (100 mg/kg, n=4) by daily oral gavage on day (D) 1-7. Without navtemadlin treatment, leukemia engraftment and leukemic burden continued to increase until the mice died on D15-D23. By contrast, hCD34 + leukemic blasts were almost undetectable on D8 and remained at significantly lower levels in PB of mice treated with navtemadlin on D15, than were detected in mice receiving vehicle alone (D8: Vehicle: 1.8±1.3%; Navtemadlin: 0.1±0.1%. D15: Vehicle: 19.9±6.0%; Navtemadlin: 0.5±0.1%). These findings suggest that navtemadlin monotherapy has the potential to deplete MPN-BP blast cells and prolong survival in MPN-BP PDX mice. To achieve long-term remission and to prevent relapse, we treated MPN-BP PDX mice with multiple cycles of low (50 mg/kg, n=4) and high dose navtemadlin (100 mg/kg, n=5) at three-week intervals based on the dynamics of leukemia cell recovery following a single cycle of navtemadlin treatment. hCD34 + cells, which contain MPN-BP SCs, and hCD45 dimCD33 + leukemic blasts were reduced in the spleen, but not in the marrows of mice during 3 cycles of 100 mg/kg navtemadlin treatment. However, reduced leukemia cell burden in PB persisted during 3 cycles of navtemadlin treatment and was associated with a prolongation in survival, which was dose-dependent (Mean survival after transplantation: Vehicle: 64.0 days; 50mg/kg navtemadlin: 86.0 days; 100mg/kg navtemadlin: 98.3 days). We then examined if a combination of navtemadlin and decitabine is more effective than single agent therapy in depleting MPN-BP SCs. Again, navtemadlin at 100 mg/kg significantly reduced the leukemia cell burden in mouse PB on C1D8 (hCD34 + cells: Vehicle: 4.1±0.8%; Navtemadlin: 0.6±0.2%, an 85% decrease. hCD45 dimCD33 + cells: Vehicle: 1.4±0.3%; Navtemadlin: 0.04±0.03%, a 97% decrease. P <0.001 for both), which persisted during 2 cycles of treatment. By contrast, multiple cycles of decitabine monotherapy (2.5mg/kg, IP, 3 times/week in 21-day cycles) resulted in a modest reduction in hCD34 + cells and hCD45 dimCD33 + cells (11.4% and 30.1% decrease, respectively) in PB of MPN-BP PDX mice, and did not reduce these cells in either the spleen or bone marrow on C1D8. Finally, addition of decitabine to navtemadlin did not further deplete either MPN-BP SCs or leukemia cells and did not improve survival of MPN-BP PDX mice, as compared to treatment with navtemadlin alone. Mean survival after transplantation in the combination study was: Vehicle: 55.5 days; navtemadlin: 70.3 days; Decitabine: 56.3 days; Combination: 64.0 days. Furthermore, toxicity (body weight loss, intestinal pathology) was observed in mice receiving high dose of navtemadlin and decitabine simultaneously, but not when either drug was administered alone. In conclusion, navtemadlin monotherapy, which activates p53, depletes leukemia cell counts and prolongs survival of MPN-BP PDX mice and is a promising agent for patients with WT TP53 MPN-BP. DisclosuresKrejsa: Kartos Therapeutics, Inc.: Current Employment. Hoffman: AbbVie Inc.: Other: Data Safety Monitoring Board, Research Funding; Kartos Therapeutics, Inc.: Research Funding; Protagonist Therapeutics, Inc.: Consultancy; Novartis: Other: Data Safety Monitoring Board, Research Funding.

Clinical and Genomic Characterization of Secondary Acute Myeloid Leukemia with Mixed Phenotype

Clinical and Genomic Characterization of Secondary Acute Myeloid Leukemia with Mixed Phenotype