High Molecular Risk Mutations Research Articles

Predictors of clinical outcome in myeloproliferative neoplasm, unclassifiable: A Bone Marrow Pathology Group study.

Myeloproliferative neoplasm, unclassifiable (MPN-U, revised to MPN, not otherwise specified in the fifth edition of the World Health Organization classification) is a heterogeneous category of primary marrow disorders with clinical, morphologic, and/or molecular features that preclude classification as a more specific MPN subtype due to stage at diagnosis, overlapping features between MPN subtypes, or the presence of coexisting disorders. Compared with other MPN subtypes, the contribution of the mutational landscape in MPN-U in conjunction with other clinical and morphologic biomarkers to prognosis has been less well investigated. We performed a multicenter, retrospective study of MPN-U (94 cases) to better define the clinicopathologic features, genetic landscape, and clinical outcomes, including subgroups of early-stage, advanced-stage, and coexisting disorders. The Dynamic International Prognostic Scoring System (DIPSS) plus scoring system was applied to assess its relevance to MPN-U prognosis. Multivariate analysis demonstrated bone marrow blast count and DIPSS plus score as statistically significant in predicting overall survival. Univariate analysis identified additional potential poor prognostic markers, including abnormal karyotype and absence of JAK2 mutation. Secondary mutations were frequent in the subset analyzed by next-generation sequencing (26/37 cases, 70.3%) with a borderline association between high molecular risk mutations and overall survival. This study, as one of the largest of MPN-U studies incorporating both clinicopathologic and molecular data, moves toward identification of biomarkers that better predict prognosis in this heterogeneous category.

HMR Mutations Drive Poor Prognosis in Myelofibrosis Patients with Lower JAK2V617F Allele Burden but Not in Those with Higher Allele Burden: Results of a Multicenter Study

JAK2V617F is the most common driver mutation in myelofibrosis (MF), followed by CALR and MPL alterations. Clinical variables included in the International Prognostic Scoring System (IPSS), Dynamic IPSS (DIPSS), and DIPSS plus, as well as JAK2V617F allele burden are all well-established prognostic factors influencing the survival of MF patients. In addition, ASXL1, EZH2, SRSF2, IDH and U2AF1 mutations are classified as high-molecular risk (HMR) mutations in this context because of their close association with disease progression and leukemic transformation. However, the relationship between JAK2V617F allele burden and HMR mutations remains unclear. To address this, we recruited 122 MF patients (discovery cohort) diagnosed at the National Taiwan University Hospital (Taipei, Taiwan) who had available mutation profile determined by next-generation sequencing. For external validation, 82 MF patients from the Christie Hospital (Manchester, U.K.) and 51 MF patients from the Cleveland Clinic (Ohio, U.S.A.) and Vilnius University Hospital Santaros Klinikos (Vilnius, Lithuania) were enrolled. The median age of the discovery cohort was 61 years. JAK2V617F was the most common driver mutation (64.8%), followed by CALR (18%) and MPL mutations (9%). ASXL1 mutation was the most common (37%) genetic alteration other than driver mutations, followed by TET2 (16%) and EZH2 mutations (12%). Overall, 55 patients (45%) had at least one HMR mutation ( ASXL1, EZH2, SRSF2, IDH and U2AF1). With a median follow-up of 28.2 months, the median overall survival (OS) of the discovery cohort was not reached (NR) and was well risk-stratified by current prognostication systems, including IPSS, DIPSS plus, MIPSS70, and GIPSS. Notably, patients with at least one HMR mutation had significantly shorter leukemia-free survival (LFS) and OS than those without (both p<0.001). Next, we divided the 79 JAK2-mutated patients into lower- and higher-allele burden groups ( JAK2low and JAK2high) using the median (75%), as the cutoff. Concurring with previous reports ( Tefferi et al, Leukemia 2008; and Guglielmelli et al, Blood 2009), JAK2low patients had significantly inferior OS than JAK2high patients (median, 53 months vs NR, p=0.037). Among all JAK2-mutated patients, those with HMR mutations had a significantly shorter OS than those without (50 months vs NR, p<0.001). When considering HMR mutations and JAK2V617F allele burden together, the presence of HMR alterations conferred worse LFS and OS in JAK2low but not in JAK2high patients (HMR vs without HMR among JAK2low patients, p<0.001 and p<0.001; and JAK2high, p=0.822 and p=0.699, respectively). By and large, patients with concurrent HMR mutations and lower JAK2V617F allele burden had a distinctively inferior OS than those with other constellations of genomic lesions ( p<0.001, Figure 1A). This group of patients also had the shortest survival among the total cohort including both JAK2-mutated and wild patients ( p<0.001). The discriminating power of integrating HMR/ JAK2 allele burden for LFS and OS remained valid in the UK cohort (HMR vs without HMR: JAK2low, p=0.013 and p=0.012; and JAK2high, p=0.337 and p=0.600, respectively) and the US/Lithuania cohort (HMR vs without HMR: JAK2low, p=0.016 and p=0.013; and JAK2high, p=0.643 and p=0.446, respectively). Co-occurrence tests in the discovery and validation cohorts revealed that there was no shared mutational co-occurrence pattern among the 3 cohorts, excluding the potential confounding influence of specific concurrent mutations. More strikingly, time-dependent ROC curve analyses suggested that integrating JAK2 allele burden with HMR mutations could be complementary to current risk stratification systems in predicting LFS and OS of MF patients (Figure 1B) across 3 cohorts. Finally, HMR/ JAK2low was identified as an independent adverse prognostic factor by multivariable analysis, irrespective of age, risk stratification systems, and other mutations. In summary, we observe that HMR mutations accompanied by a lower mutant JAK2V617F allele burden identified a distinct MF population with significantly reduced survival and high risk of leukemic transformation, with independent prognostic relevance extrapolated to and validated in two independent cohorts. Experimental studies are ongoing to ascertain the underlying mechanistic basis and resolve the clonal architecture of this distinct MF genomic grouping.

Ras Activity Is Significantly Elevated in Patients with Primary Myelofibrosis and Is Agnostic to the Presence of RAS and JAK pathwaymutations

Myelofibrosis (MF) is a myeloproliferative stem cell disorder arising from various clonal mutations in early myeloid-committed hematopoietic progenitor cells. The subsequent acquisition of additional mutations and cytokine signaling then heralds the recruitment of fibroblasts to the marrow space, leading to collagen deposition. MF disease behavior varies widely and hematopoietic stem cell transplantation remains the only curative therapeutic option. In non-transplant candidates, managing cytopenic disease is uniquely challenging as patients develop resistance to commonly-utilized Jak-inhibitors. Expanding the molecular landscape of the disease beyond Jak/Stat signaling with the goal of identifying new therapeutic targets has, accordingly, been an area of growing interest in MF research. Recently-published studies, including results from our own institution, have identified mutations that potentially activate Ras signaling as being associated with features of advanced MF (higher somatic mutation burden) as well as with shorter overall survival and progression to AML. The goals of our study is to expand on this prior data, characterize the activity of Ras signaling and determine its role in patients with MF. Peripheral blood mononuclear cells (PBMCs) from 27 patients with myelofibrosis (MF) at a single institution underwent integrated genomic-transcriptomic sequencing analyses using the University of Michigan MiOncoSeq platform. PBMCs were separated by Ficoll® followed by cell lysis and protein quantification. Ras activity was measured by the binding of effector Ras binding domain (RBD) via ELISA. Patients with MF were compared to healthy donors and to patients with either polycythemia vera (PV) or essential thrombocythemia (ET). Ras activity in MF was examined across different mutations and with respect to various clinical parameters. Multivariate analyses were performed to assess the impact of each individual mutation on Ras activity. Accompanying statistical analyses for all assessments were conducted using two-way unpaired t-tests. Overall, Ras activity in 21 assessable patients with MF was 1.64 fold higher than in PV/ET (12 patients, p=0.0462) and 1.74 fold higher than healthy donors (13 volunteers, p=0.0304). While the majority of patients in the MF cohort had driver mutations, including in JAK2 (73%) and CALR (15.4%), the individual types of driver mutations did not impact Ras activity. Within the Ras/MAP Kinase signaling pathway, mutations were present at a range of variant allele frequencies (VAF), including 2 patients with NRAS (one with VAF 42%, one <5%), 2 KRAS (both <5%), 2 NF1, 1 CBL and 1 RAF1 (VAFs not assessed). The individual impact of various driver mutations, epigenetic regulators and splicing factors as assessed by multivariate analysis identified a trend toward enhanced Ras activity with mutations in RAS, CALR, ASXL1, TET2 and TP53, suggesting that in addition to RAS, other mutations also activate Ras signaling in MF. With regards to clinical parameters, Ras activity was weakly correlated with spleen size and high molecular risk mutation (HMR) presence, although this did not reach statistical significance in this cohort due to a relatively small sample size. Next, we performed a differential enrichment of myeloid and lymphoid cells from PBMCs using EasySep™ and measured Ras activity in lymphoid and myeloid enriched cells. We observed that the ratio of myeloid:lymphoid activity in patients with MF with RAS/MAP Kinase pathway mutations is 3.8 times higher than in patients without such mutations (p=0.0012), suggesting that RAS pathway mutations have a predominant role in myeloid cells. Our results show that the majority of patients with MF have hyperactive Ras signaling compared to PV/ET or healthy donors, regardless of the presence of alterations in the Ras signaling pathway. This underscores the importance of functional assessment of Ras activity in patients with MF and provides evidence that targeting Ras signaling in MF may lead to therapeutic benefit. We are currently expanding our analysis to a larger cohort of MF patients and performing preclinical testing of Ras/MAP Kinase pathway inhibitors as a means of overcoming Jak-inhibitor resistance.

Oral Decitabine/Cedazuridine Is a Tolerable and Effective Ambulatory Regimen for Patients with Advanced Myeloproliferative Neoplasms

Background: Treatment options are limited for patients (pts) with advanced myeloproliferative neoplasms (MPNs). Most pts become refractory to JAK2 inhibitor (JAKi) therapy by 3 years with subsequent survival of only 11-16 months. Sequential treatment with chromatin-modifying agents including decitabine (D) can upregulate CXCR4 expression, correct abnormal trafficking of myelofibrosis (MF) stem cells, and eliminate JAK2V617F+ MF stem and progenitor cells in preclinical models ( Wang et al, Cancer Res 2019, Blood 2010). Combination therapy with intravenous D and ruxolitinib (Rux) had a favorable effect on overall survival (OS) in a phase 2 study of MPN-accelerated/blast phase pts ( Mascarenhas et al, Blood Adv 2020) and prolonged survival in a cohort of DIPSS-plus high-risk MF pts ( Bader et al, Leuk Res 2015). Oral decitabine/cedazuridine (DC), therefore, represents an attractive ambulatory treatment option for pts with advanced MPNs. Methods: We retrospectively reviewed the electronic health records of pts with advanced high-risk MF (AHR-MF) or MPN- accelerated phase (MPN-AP) seen at our institution that were treated with DC with or without a JAKi from 1/2021-7/2023. MPN-AP was defined by the presence of 10-19% blasts in peripheral blood/ bone marrow. AHR-MF was defined by the presence of 4-9% circulating blasts or 5-9% blasts in the bone marrow, and/or refractoriness to a JAKi. Results: A total of 14 pts, 7 each with MPN-AP and AHR-MF, respectively received DC therapy (Table 1). Most pts (8/14 or 57%) were older than 75 years. All pts were classified as high risk/very high-risk (MIPPS70 plus v.2). Ten (71%) pts had one or more high molecular risk mutations ( ASXL1, EZH2, SRSF2, IDH1/2, U2AF1), with the most prevalent being ASXL1 mutations in 8/14 (57%) pts. Other somatic mutations included NF1, KRAS, NRAS, BRAF, GATA2, STAG2, DNMT3A and TET2 genes. Eight of the 14 pts (57%) had either an unfavorable or very high-risk karyotype (MIPSS70 plus v.2). Thirteen pts had previously failed JAKi therapy. The median number of cycles of DC therapy was 2 (range,1-6) and 4 (range,1-26) for MPN-AP and AHR-MF pts, respectively and 4/7 pts received a concurrent JAKi in each group. Two pts in AHR-MF cohort were successfully bridged to transplant. Two pts in the MPN-AP group discontinued treatment after cycle 1 due to neutropenic sepsis and progression to blast phase, respectively. Among MPN-AP pts who received ≥ 2 cycles of DC, circulating blasts were reduced to ≤ 5% in 4/5 pts, normalization of thrombocytopenia and improvement in hemoglobin by ≥ 1.5 g/dl each occurred in 3/5 pts (Fig.1). In the AHR-MF cohort, 6/7 pts received ≥ 2 cycles of DC with elimination of circulating blasts in one pt. WBC and platelet count were effectively reduced in 4/4 and 2/2 pts with baseline WBC of >50x 10 3/uL and platelet count >1000 x 10 3/uL, respectively. Spleen size reduction was achieved in two pts with combination of DC + Rux who were previously refractory to a JAKi. One pt achieved complete resolution of palpable splenomegaly after 2 cycles of combination therapy. The predominant treatment-related adverse event was neutropenic fever in three pts requiring hospitalization. DC cycle length was reduced from 5 to 3/28 days in 7/14 pts, which reduced the degree of therapy related neutropenia and anemia. Pts remained ambulatory during treatment except for hospitalizations related to neutropenic fever. With a median follow-up of 109 days (range, 28 days - 29 months), median OS has not been reached. Three pts in the MPN-AP cohort progressed to MPN-blast phase (BP), including two pts who only received one cycle of DC. Two pts with MPN-BP died after 28 and 68 days of DC therapy, respectively. None of the AHR-MF pts progressed to MPN-AP/BP. The most durable response was observed in a pt who has received a total of 26 cycles of DC + Rux with stable disease for >2 years and loss of BRAF and KRAS mutations after 9 months of treatment. Conclusions: DC therapy appears to be a well-tolerated and effective oral ambulatory regimen with clinically meaningful responses in elderly, transplant ineligible pts as well as a bridge to transplant in high-risk pts with advanced MPNs. The ease of outpatient administration significantly reduces pt treatment burdens and positively impacts their quality of life. These data provide a rationale for studying oral decitabine/cedazuridine +/- JAKi in a prospective manner, especially in pts with AHR-MF refractory to JAKi prior to evolution MPN-AP/BP.

Type 1/like Calr Mutation in Momelotinib-Treated Patients with Myelofibrosis Is the Most Prominent Predictor of Drug Survival and Longevity without Transplant

Background: Non-transplant treatment options in myelofibrosis MF are palliative in scope and include Janus kinase 2 (JAK2) inhibitors (JAKi). FDA-approved JAKi for the treatment of MF include ruxolitinib, fedratinib, and pacritinib. A fourth JAKi, momelotinib, is currently under review. We have previously reported long-term survival data on momelotinib and drug survival that was significantly longer, retrospectively compared to ruxolitinib ( AJH. 2022;97:E433). In the current study, we focused on molecular predictors of drug survival (i.e., drug retention) and longevity without allogeneic hematopoietic stem cell transplant AHSCT (transplant-censored survival). Methods : The current study included data from Mayo Clinic patients who participated in a phase-1/2 core study of momelotinib (NCT00935987). Study design, drug doses and schedule, and additional details on treatment effect and side effects have previously been published. Drug survival was calculated from time of initiation of momelotinib to time of treatment discontinuation. Survival analysis required censoring of patients at time of AHSCT. Conventional statistical methods were applied using JMP Pro 16.0.0 software (SAS Institute, Cary, NC, USA). Results : 79 JAKi-naïve patients with MF were considered: median age 67 years; males 54%; PMF 65%, post-PV MF 20%, post-ET MF 15%; JAK2 71%, type 1/like CALR ( CALR-1) 14%, CALR-2 3%, MPL 8%, triple-negative 5%. Risk category according to DIPSS was high/intermediate in 80% of the patients and unfavorable karyotype in 29%. Non-driver mutation information was available in a subset of patients and included ASXL1 22% and SRSF2 18%. Median time from diagnosis to study entry was 25.2 months; patients were enrolled between November 2009 and March 2011 with follow-up information updated through July 2023; during this period, 68 (86%) deaths, 13 (16%) leukemic transformations, and 7 (9%) AHSCTs were recorded. Median follow-up for alive patients was 12.5 years (range 11.3-13.1). Anemia response rate was 48% and spleen 47%. Median treatment duration was 25 months (range 0.1-157); the proportion of patients remaining on active therapy was 68% at 1 year, 30% at 3 years, 16% at 5 years, and 7% at 10 years (Figure 1a). At the time of this writing, 5 (6.3%) patients were still receiving momelotinib therapy with treatment durations of 152 to 157 months. In univariate analysis, molecular predictors of drug survival included CALR-1 (p=0.006) but not ASXL1 (p=0.6) or SRSF2 (p=0.3) mutation, or unfavorable karyotype (p=0.08). The 3-, 5-, and 10-year drug survival rates for CALR-1-mutated patients were 64%, 40%, and 18%, respectively, and for CALR-1 wild-type 25%, 11%, and 4% (p=0.01, Figure 1b). CALR-1 independent association with longer drug survival was also appreciated for younger age (p<0.01) and absence of baseline transfusion dependency at time of study entry (p=0.02); all three risk factors remained significant during multivariable analysis with HR (95% CI) rates of 0.4 (0.2-0.87) for CALR-1, 0.5 (0.3-0.89) for age <63 years, and 0.6 (0.3-0.9) for absence of transfusion-dependency. Spleen response (p<0.01) but not anemia response (p=0.23) was also associated with longer drug survival; in multivariable analysis all 4 risk factors retained significance. Multivariable analysis of genetic variables for transplant-censored survival identified absence of CALR-1 (HR 3.5, 95% CI 1.2-10.5; p=0.03) and presence of high molecular risk (HMR; ASXL1/ SRSF2) mutations (HR 2.3, 95% CI 1.1-4.6; p=02) to independently predict inferior survival. Among 11 patients with CALR-1 mutation, median transplant-censored survival was 125 months with 10-year survival rate of 60% (Figure 1c); by contrast, the corresponding figures were 37 months and 12%, in the 68 patients not harboring CALR-1 mutation (Figure 1c). In multivariable analysis, absence of CALR-1 (HR 2.9, 95% CI 1.02-8.1), age ≥63 years (HR 3.0, 95% CI 1.5-6.0), and absence of spleen response (HR 2.6, 95% CI 1.5-4.5) were identified as being most significant in predicting inferior transplant-censored survival. Conclusions : CALR-1 mutation is the most important risk factor for both drug survival and longevity without AHSCT, in momelotinib-treated patients with MF. Such information might help identify MF patients who might benefit from treatment with momelotinib and in whom AHSCT might be deferred or not.

Phase 2 Study to Assess the Safety and Efficacy of Bomedemstat (MK3543) in Combination with Ruxolitinib in Patients with Myelofibrosis

Background Approximately 50% of patients with myelofibrosis (MF) discontinue ruxolitinib after 3 years, mostly due to disease progression, suboptimal response or cytopenia. Outcome after ruxolitinib discontinuation is poor with a median overall survival (OS) of approximately 14 months. Lysine-specific demethylase-1 (LSD1) is a histone demethylase critical for self-renewal of malignant hematopoietic stem cells and for maturation of progenitor cells. Bomedemstat is an oral LSD1 inhibitor clinically active in patients with myeloproliferative neoplasms (MPN) and has shown clinical activity as a single-agent in patients with MF. Aims This is an ongoing, open-label, Phase 2 study of the combination of bomedemstat and ruxolitinib in treatment-naïve patients with MF or those with a sub-optimal response to ruxolitinib. The objectives of this are to evaluate the safety and tolerability of the combination, the optimal dosing of bomedemstat in this regimen, and to assess the efficacy of the combination as assessed by spleen size reduction and symptom reduction using the Myelofibrosis Symptom Assessment Form (MFSAF). Methods Cohort A is comprised of patients with a sub-optimal response to an adequate trial of ruxolitinib defined as splenomegaly not reduced by >35% from baseline or symptoms scores that have not improved by >50%. Cohort A patients must have been on a stable dose of ruxolitinib for ≥8wks. Cohort B is comprised of treatment-naïve patients with MF who require treatment per guidelines. Patients in Cohort A remain on the entry dose of ruxolitinib while Cohort B patients received a starting ruxolitinib dose of 10 mg BID throughout the study. All patients received concomitantly, a starting dose of bomedemstat of 0.4mg/kg/d. Dose adjustments up were allowed every 4 weeks to achieve a target platelet count of 50 x 10 9/L (40-90 x 10 9/L range) Down titrations could be made at any time in the interest of patient safety. Results At the data cut-off of 30 June 2023, 16 men and 16 women with a median age of 64 (range: 47-81) years were enrolled. Case distribution was PMF, N=19 (59.4%); PPV-MF, N=7 (21.9%); and PET-MF, N=6 (18.8%). Mutational profile of driver genes was JAK2 V617F, N=24 (75%); JAK2 exon 12, N=1 (3.1%); and CALR mutations, N=7 (21.9%). Six patient (18.8%) harbored high-molecular risk (HMR) mutations ( ASXL N =4; EZH2, N=2). At enrollment, the median white blood cell count (WBC), hemoglobin (Hb), platelet count, and lactate dehydrogenase (LDH) were 10.21 x 10 9/L (2.4-50.8 x 10 9/L), 9.4 g/dL (6.7-12.1g/dL), 215 x 10 9/L (100-906 x 10 9/L) and 504 IU/L (107-2174 UL), respectively. Ten patients (31.2%), 19 patients (59.4%) and 3 patients (9.4%) belonged to the Dynamic International Prognostic Scoring System (DIPSS) high, intermediate-2 and intermediate-1 risk categories, respectively. The median spleen size was 5cm (5-16cm) below left costal margin (BLCM). Twenty-four patients were enrolled in Cohort A with a median treatment duration of ruxolitinib of 128 (13-668) weeks. Cohort B has enrolled 8 patients. The median duration of ruxolitinib + bomedemstat was 12 (1-26) weeks. In 20 evaluable patients at Week 12 (Cohort A, N=17; Cohort B, N=3), 12 patients (60%) had stable ( ∆<± 1.0 g/dL) or improved Hb (>1.0 g/dL) (Cohort A: 11/17, 64.7%; Cohort B: 1/3, 33.3%), 5 patients (25%) had ≥50% reduction in MF-SAF Total Symptom Score (TSS) (Cohort A: 4/17, 23.5%; Cohort B: 1/3, 33.3%) and 18 patients (65%) had ≥ 30% spleen length reduction (Cohort A: 15/17, 88.2%; Cohort: 3/3, 100%) (Figure 1A-C). In six patients evaluable for molecular responses by droplet-digital polymerase chain reaction at Week 12, 4 patients (67%) had reductions in JAK2 V617F allele frequencies with 1 patient (17%) having ≥50% reduction. The most common non-hematologic adverse events (AEs) were diarrhea (Grade 1-2, N=16; Grade 3-4, N=0); malaise (Grade 1-2, N= 6; Grade 3-4, N=0); oedema (Grade 1-2, N=7; Grade 3-4, N=0) and dysgeusia (Grade 1-2, N=5; Grade 3-4, N=0). There were no safety signals, dose-limiting toxicities, or deaths related to drug. Conclusions These early results suggest that the addition of bomedemstat to a ruxolitinib regimen is well tolerated, improves splenomegaly and symptom scores, and stabilizes hemoglobin both in the frontline and second-line setting. Enrollment in ongoing.

Impact of Clinical and Genetic Factors on Myelofibrosis Outcomes after Allogeneic Transplantation

Introduction: The reported impact of gene mutations, including JAK2-V617F, other MPN phenotypic drivers and additional cooccurring mutations on outcomes after allogeneic transplantation (HCT) in myelofibrosis (MF) has been inconsistent. While the MTSS score incorporated ASXL1 and JAK2 (non MPL/CALR mutations) as unfavorable predictors after HCT, other studies reported JAK2 mutations to be favorable (Blood 2010). Further, in some studies, mutations known to affect disease progression in MF pre-HCT (high-molecular risk or HMR mutations) have not been predictors of post-HCT outcomes. Here we present outcomes in all MF patients undergoing HCT at Dana-Farber Cancer Institute (DFCI) from 2000-2020 and examine clinical and genetic predictors of outcomes, stratified by year of HCT (<2011 or pre-2011 and >2011 or post-2011). Of note, ruxolitinib was available for use post-2011 only, following its FDA approval that year. Methods: Patients with MF who underwent HCT from 2000-2020 at DFCI (n=166) were included in this retrospective cohort analysis. Outcomes were analyzed for the whole cohort as well as sub-group analyses in the pre-2011 (n=39) and post-2011 era (n=127). Mutational analysis was performed by targeted next-generation sequencing of available pre-HCT samples in 115/127 patients in the post-2011 era. Results: Median age was 61 years and follow up 56.2 months. 25% had massive splenomegaly. DIPSS-plus scores were high in 45.2% and 45.1% received rux. HCT and patient characteristics (including KPS and median time from diagnosis to HCT) were similar pre and post 2011, with differences in conditioning regimens. Majority (77.1%) had HLA-matched donors, underwent reduced intensity (69.3%) HCT with peripheral blood stem-cells (92.2%) and received tacrolimus/methotrexate based GVHD prophylaxis (90.1%). FluMel100/140 (n=65), FluBu4 (n=34) and FluBu2 (n=11) were commonly used in the post-2011 era, while Flu/Bu1 (n= 34), ablative Bu/Cy (n=5) and Cy/TBI (n=12) were predominant pre-2011. Few patients underwent pre-HCT splenectomy (10.2%) or splenic irradiation (9%). Median D100 donor chimerism was 68% for Flu/Bu1, 86% for Flu/Bu2, 98% for Flu/Bu4, and 100% for Flu/Mel100-140. At 4 years, overall survival (OS) for the whole cohort was 58% (50,66), progression-free survival (PFS) 55% (47,63), non-relapse mortality (NRM) 23% (17,30) and relapse rate 21%. 4 year OS was significantly better in the post-2011 era compared to pre-2011 (69% vs 26%, p<0.0001), as was PFS, driven by lower relapse rates in the post-2011 era (15% vs 41%, p<0.0001). 4-yr NRM was also marginally better (20% vs 33%, p= 0.17). In the post-2011 era, 115/127 patients had NGS panel-based genetic analysis prior to HCT (Fig 1), demonstrating 91.3% of patients had at least one driver mutation (JAK2 62.6%, CAL-R 13.9%, MPL 14.8%) while 8.7% patients were triple negative. The most frequent cooccurring mutations were ASXL1 (40%), TET2 (28.7%) and U2AF1 (17.4%).In univariable analysis (UVA), the presence of JAK2 mutations (JAK2+) was associated with superior PFS (HR 0.5, 95% CI 0.27,0.94, p= 0.03) while CALR (HR 1.86, p=0.12) and MPL (HR:1.21, p=0.65) mutations were not significant for PFS. Triple negative patients showed a trend towards poorer PFS (HR 2.27, p=0.05). OS results mirrored those of PFS. No cooccurring myeloid gene mutations were associated with PFS or OS. Superior 4-year OS for JAK2+ versus JAK2- recipients (80% versus 58%, p=0.01) is shown in Figure 2. TP53 (p=0.03), TET2 (p=0.015) and EZH2 (p=0.002) mutations were associated with higher relapse rates in UVA. Patients with JAK2+ and cooccurring ASXL1 mutations had poorer OS compared to those with JAK2+/no cooccurring ASXL1 mutations (HR=2.69, p=0.031). Combining clinical and molecular features in the post-2011 era, in MVA, only DIPSS high (HR=4.76, p=0.03) and KPS < 90% (HR=2.66, p=0.024) were significantly associated with poorer OS/PFS while JAK2+ (HR=0.32, 95% CI 0.14,0.75,p=0.009) was significantly associated with better OS/PFS; JAK inhibitor use spleen size/management, conditioning regimen or other mutations including HMR mutations and TP53 were not significantly associated with OS/PFS. Conclusions: In this single-institution retrospective analysis, the presence of a JAK2-V617F mutation was associated with better OS and PFS following HCT in MF in the post-2011 era. Survival outcomes are significantly better in the post-2011 era compared to pre-2011, in our cohort.

Meter: A Multi-Country, Real-World Chart Review Study to Explore Treatment Patterns, Effectiveness and Healthcare Resource Utilization for Patients with Myelofibrosis

Background : Myelofibrosis (MF) is a rare myeloproliferative disorder associated with significant morbidity and mortality. The hallmarks of MF pathobiology include aberrant myeloproliferation, cytokine-induced inflammation, bone marrow reticulin fibrosis, extramedullary hematopoiesis, cytopenias, and constitutional symptoms. Hydroxyurea was the most commonly used drug in patients with MF prior to the approval of ruxolitinib (RUX), a first-in-class Janus kinase 1/2 inhibitor (JAKi) that is widely approved for symptomatic patients with MF. In addition to RUX, the JAKis fedratinib and, more recently, pacritinib have also been approved by the US Food and Drug Administration. Real-world treatment patterns and impact of currently available JAKis on patients with MF are not well understood. Several novel agents are in advanced development and will further reshape the treatment landscape of MF. A better understanding of current treatment patterns will assist in positioning novel treatments within the MF therapeutic landscape. Methods : The METER study (NCT05444972) is an ongoing multicountry noninterventional retrospective chart review assessing treatment patterns, effectiveness, and healthcare resource utilization (HCRU) in patients diagnosed with MF. Data from patients aged ≥18 years with primary or secondary MF treated on or after the local first date of RUX approval until December 31 , 2021 were assessed. Patients who received treatment for MF in a clinical trial were excluded. The primary objective is to describe real-world MF treatment patterns, including patient characteristics, time from MF diagnosis to first-line (1L) therapy, choice, duration and reason for change/discontinuation of initial and subsequent treatments for MF, and treatment procedures. Secondary objectives include assessments of days hospitalized as part of HCRU. Results : As of June 1, 2023, 928 patient charts were included, met eligibility criteria, and had initial treatment information available. Most patients were male (54%) and White (65%), and the median (range) age for patients ≤89 years of age was 66 (58-73) years; the most common geographic locations were Europe (53%), Latin America (23%), and North America (13%). Of patients, 66% (614/928) had primary MF, and 10% (97/928) were transfusion-dependent. Of patients tested for high molecular risk mutations, 50% (81/162) were positive. Of patients with available bone marrow fibrosis data, 82% (554/680) had grade ≥2 bone marrow fibrosis at diagnosis. The average interval from MF diagnosis to start of initial treatment (index date) was approximately 8.5 months. RUX was the most commonly used 1L therapy (47%; 437/928) followed by hydroxyurea (41%; 380/928). RUX was also the most common therapy used in second-line (2L), third-line, fourth-line, and fifth-line treatment for 62% (217/353), 63% (107/171), 66% (56/85), and 59% (24/41) of patients, respectively. Mean (SD) time from index date to procedural intervention was 556 (519) days; the most common procedure was stem cell transplant (n = 71) followed by splenectomy (n = 20). Of the 927 patients who received 1L therapy, 98% remained on 1L therapy through Week 24, and 66% did not initiate 2L therapy until Week 156. Median (95% CI) duration of 1L therapy was 48 (45-52) months (Figure). Median (95% CI) survival from the start of 1L therapy was 79 (71-NR) months. The estimated survival rate (95% CI) was 76% (73-79) at Week 156. Median (95% CI) overall survival was 120 (93-147) months. Median (Q1-Q3) total number of days hospitalized after the index date was 2 (0-19), and median (Q1, Q3) total number of days in the intensive care unit after the index date was 0 (0, 0). Analyses will be updated for presentation. Conclusions : In patients with MF, RUX was the most commonly used agent in all lines of therapy. The greatest reduction in duration of MF treatment occurred from 1L to 2L. Most patients remained on 1L therapy through Week 24 and did not initiate 2L therapy until Week 156. Median survival time from start of 1L therapy to death was 79 months (approximately 6 years). There was a high degree of advanced bone marrow fibrosis as well as transfusion dependence among this real-world patient population. Together, these results highlight the importance of optimizing 1L therapy.

High cell-free DNA is associated with disease progression, inflammasome activation and elevated levels of inflammasome-related cytokine IL-18 in patients with myelofibrosis.

Myelofibrosis (MF) is a clonal hematopoietic stem cell disorder classified among chronic myeloproliferative neoplasms, characterized by exacerbated myeloid and megakaryocytic proliferation and bone marrow fibrosis. It is induced by driver (JAK2/CALR/MPL) and high molecular risk mutations coupled to a sustained inflammatory state that contributes to disease pathogenesis. Patient outcome is determined by stratification into risk groups and refinement of current prognostic systems may help individualize treatment decisions. Circulating cell-free (cf)DNA comprises short fragments of double-stranded DNA, which promotes inflammation by stimulating several pathways, including inflammasome activation, which is responsible for IL-1β and IL-18 maturation and release. In this work, we assessed the contribution of cfDNA as a marker of disease progression and mediator of inflammation in MF. cfDNA was increased in MF patients and higher levels were associated with adverse clinical outcome, a high-risk molecular profile, advanced disease stages and inferior overall survival, indicating its potential value as a prognostic marker. Cell-free DNA levels correlated with tumor burden parameters and markers of systemic inflammation. To mimic the effects of cfDNA, monocytes were stimulated with poly(dA:dT), a synthetic double-stranded DNA. Following stimulation, patient monocytes released higher amounts of inflammasome-processed cytokine, IL-18 to the culture supernatant, reflecting enhanced inflammasome function. Despite overexpression of cytosolic DNA inflammasome sensor AIM2, IL-18 release from MF monocytes was shown to rely mainly on the NLRP3 inflammasome, as it was prevented by NLRP3-specific inhibitor MCC950. Circulating IL-18 levels were increased in MF plasma, reflecting in vivo inflammasome activation, and highlighting the previously unrecognized involvement of this cytokine in MF cytokine network. Monocyte counts were higher in patients and showed a trend towards correlation with IL-18 levels, suggesting monocytes represent a source of circulating IL-18. The close correlation shown between IL-18 and cfDNA levels, together with the finding of enhanced DNA-triggered IL-18 release from monocytes, suggest that cfDNA promotes inflammation, at least in part, through inflammasome activation. This work highlights cfDNA, the inflammasome and IL-18 as additional players in the complex inflammatory circuit that fosters MF progression, potentially providing new therapeutic targets.

The prognostic contribution of CBL, NRAS, KRAS, RUNX1, and TP53 mutations to mutation-enhanced international prognostic score systems (MIPSS70/plus/plus v2.0) for primary myelofibrosis.

Contemporary risk models in primary myelofibrosis (PMF) include the mutation (MIPSS70) and mutation/karyotype enhanced (MIPSS70 plus/v2.0) international prognostic scoring systems. High molecular risk (HMR) mutations incorporated in one or both of these models include ASXL1, SRSF2, EZH2, IDH1/2, and U2AF1Q157; the current study examines additional prognostic contribution from more recently described HMR mutations, including CBL, NRAS, KRAS, RUNX1, and TP53. In a cohort of 363 informative cases (median age 58 years; 60% males), mutations included JAK2 61%, CALR 24%, MPL 6%, ASXL1 29%, SRSF2 10%, U2AF1Q157 5%, EZH2 10%, IDH1/2 4%, TP53 5%, CBL 5%, NRAS 7%, KRAS 4%, and RUNX1 4%. At a median follow-up of 4.6 years, 135 (37%) deaths and 42 (11.6%) leukemic transformations were recorded. Univariate analysis confirmed significant survival impact from the original MIPSS70/plus/v2.0 HMR mutations as well as CBL (HR 2.8; p < .001), NRAS (HR 2.4; p < .001), KRAS (HR 2.1; p = .01), and TP53 (HR 2.4; p = .004), but not RUNX1 mutations (HR 1.8; p = .08). Multivariate analysis (MVA) that included both the original and more recently described HMR mutations confirmed independent prognostic contribution from ASXL1 (HR 1.8; p = .007), SRSF2 (HR 4.3; p < .001), U2AF1Q157 (HR 2.9, p = .004), and EZH2 (HR 2.4; p < .001), but not from IDH1/2 (p = .3), TP53 (p = .2), CBL (p = .3), NRAS (p = .8) or KRAS (p = .2) mutations. The lack of additional prognostic value from CBL, NRAS, KRAS, RUNX1, and TP53 was further demonstrated in the setting of (i) MVA of mutations and karyotype, (ii) MVA of MIPSS70/plus/v2.0 composite scores and each one of the recently described HMR mutations, except TP53, and iii) modified MIPSS70/plus/plus v2.0 that included CBL, NRAS, KRAS, and TP53 as part of the HMR constituency, operationally referred to as "HMR+" category. Furthermore, "HMR+" enhancement of MIPSS70/plus/plus v2.0 did not result in improved model performance, as measured by C-statistics. We conclude that prognostic integrity of MIPSS70/plus/plus v2.0, as well as their genetic components, was sustained and their value not significantly upgraded by the inclusion of more recently described HMR mutations, including CBL, NRAS, KRAS, and RUNX1. Additional studies are needed to clarify the apparent additional prognostic value of TP53 mutation and its allelic state.

Drivers and high-molecular-risk mutations in Argentine patients with primary myelofibrosis

Primary myelofibrosis (PMF), a BCR-ABL negative myeloproliferative neoplasm, is a heterogeneous clinical and genetic disorder with a poor prognosis. We aimed to study the mutational profile of driver genes (JAK2, CALR, and MPL) and high-molecular-risk (HMR) genes (ASXL1, EZH2, IDH1/2, and SRSF2) and their prognostic impact in 65 Argentine patients with PMF. Mutually exclusive driver mutations were identified in 88% of the cases and HMR mutations were detected in 37% of patients, including 37.5% of triple negative cases. ASXL1 and SRSF2 were the most frequently mutated HMR genes, and a significant association between these mutations was observed (P = 0.04). Additionally, age &gt;65 years, lower hemoglobin level, constitutional symptoms, male sex, and bone marrow (BM) fibrosis grade ≥ 2 were correlated with ASXL1 mutations, and circulating blasts with SRSF2 mutations. HMR mutations were significantly associated with inferior overall survival (P &lt; 0.001). These mutations were more frequent with increasing risk of DIPSS score and allowed us to identify patients with poor survival in intermediate DIPSS groups. The application of the MIPSS70 score stratified our patients into three risk groups, with significant differences in overall survival (P &lt; 0.001). Interestingly, 85% of the patients who were upgraded to a higher risk category compared to the DIPSS score showed a HMR profile. In conclusion, our study contributes to the understanding of the mutational landscape in MFP, supports the integration of molecular data to improve prognostic models and reinforces the adverse prognostic impact of HMR mutations, particularly in ASXL1 and SRSF2 genes.

Impact of Clonal Architecture on Clinical Course and Prognosis in Patients With Myeloproliferative Neoplasms.

Myeloproliferative neoplasms (MPNs) are caused by a somatic gain-of-function mutation in 1 of the 3 disease driver genes JAK2, MPL, or CALR. About half of the MPNs patients also carry additional somatic mutations that modify the clinical course. The order of acquisition of these gene mutations has been proposed to influence the phenotype and evolution of the disease. We studied 50 JAK2-V617F-positive MPN patients who carried at least 1 additional somatic mutation and determined the clonal architecture of their hematopoiesis by sequencing DNA from single-cell-derived colonies. In 22 of these patients, the same blood samples were also studied for comparison by Tapestri single-cell DNA sequencing (scDNAseq). The clonal architectures derived by the 2 methods showed good overall concordance. scDNAseq showed higher sensitivity for mutations with low variant allele fraction, but had more difficulties distinguishing between heterozygous and homozygous mutations. By unsupervised analysis of clonal architecture data from all 50 MPN patients, we defined 4 distinct clusters. Cluster 4, characterized by more complex subclonal structure correlated with reduced overall survival, independent of the MPN subtype, presence of high molecular risk mutations, or the age at diagnosis. Cluster 1 was characterized by additional mutations residing in clones separated from the JAK2-V617F clone. The correlation with overall survival improved when mutation in such separated clones were not counted. Our results show that scDNAseq can reliably decipher the clonal architecture and can be used to refine the molecular prognostic stratification that until now was primarily based on the clinical and laboratory parameters.

Ruxolitinib in cytopenic myelofibrosis: Response, toxicity, drug discontinuation, and outcome.

Patients with cytopenic myelofibrosis (MF) have more limited therapeutic options and poorer prognoses compared with patients with the myeloproliferative phenotype. Prognostic correlates of cytopenic phenotype were explored in 886 ruxolitinib-treated patients with primary/secondary MF (PMF/SMF) included in the RUX-MF retrospective study. Cytopenia was defined as: leukocyte count <4×109 /L and/or hemoglobin <11/<10g/dL (males/females) and/or platelets <100×109 /L. Overall, 407 (45.9%) patients had a cytopenic MF, including 249 (52.4%) with PMF. In multivariable analysis, high molecular risk mutations (p=.04), intermediate 2/high Dynamic International Prognostic Score System (p<.001) and intermediate 2/high Myelofibrosis Secondary to Polycythemia Vera and Essential Thrombocythemia Prognostic Model (p<.001) remained associated with cytopenic MF in the overall cohort, PMF, and SMF, respectively. Patients with cytopenia received lower average ruxolitinib at the starting (25.2mg/day vs. 30.2mg/day, p<.001) and overall doses (23.6mg/day vs. 26.8mg/day, p<.001) and achieved lower rates of spleen (26.5% vs. 34.1%, p=.04) and symptom (59.8% vs. 68.8%, p=.008) responses at 6months compared with patients with the proliferative phenotype. Patients with cytopenia also had higher rates of thrombocytopenia at 3months (31.1% vs. 18.8%, p<.001) but lower rates of anemia (65.6% vs. 57.7%, p=.02 at 3months and 56.6% vs. 23.9% at 6months, p<.001). After competing risk analysis, the cumulative incidence of ruxolitinib discontinuation at 5years was 57% and 38% in patients with cytopenia and the proliferative phenotype (p<.001), whereas cumulative incidence of leukemic transformation was similar (p=.06). In Cox regression analysis adjusted for Dynamic International Prognostic Score System score, survival was significantly shorter in patients with cytopenia (p<.001). Cytopenic MF has a lower probability of therapeutic success with ruxolitinib as monotherapy and worse outcome. These patients should be considered for alternative therapeutic strategies.

Clinical and genetic characteristics of young patients with myeloproliferative neoplasms

Objectives: To investigate the clinical and genetic features of young Chinese patients with myeloproliferative neoplasms (MPN). Methods: In this cross-sectional study, anonymous questionnaires were distributed to patients with MPN patients nationwide. The respondents were divided into 3 groups based on their age at diagnosis: young (≤40 years) , middle-aged (41-60 years) , and elderly (>60 years) . We compared the clinical and genetic characteristics of three groups of MPN patients. Results: 1727 assessable questionnaires were collected. There were 453 (26.2%) young respondents with MPNs, including 274 with essential thrombocythemia (ET) , 80 with polycythemia vera (PV) , and 99 with myelofibrosis. Among the young group, 178 (39.3%) were male, and the median age was 31 (18-40) years. In comparison to middle-aged and elderly respondents, young respondents with MPN were more likely to present with a higher proportion of unmarried status (all P<0.001) , a higher education level (all P<0.001) , less comorbidity (ies) , fewer medications (all P<0.001) , and low-risk stratification (all P<0.001) . Younger respondents experienced headache (ET, P<0.001; PV, P=0.007; MF, P=0.001) at diagnosis, had splenomegaly at diagnosis (PV, P<0.001) , and survey (ET, P=0.052; PV, P=0.063) . Younger respondents had fewer thrombotic events at diagnosis (ET, P<0.001; PV, P=0.011) and during the survey (ET, P<0.001; PV, P=0.003) . JAK2 mutations were found in fewer young people (ET, P<0.001; PV, P<0.001; MF, P=0.013) ; however, CALR mutations were found in more young people (ET, P<0.001; MF, P=0.015) . Furthermore, mutations in non-driver genes (ET, P=0.042; PV, P=0.043; MF, P=0.004) and high-molecular risk mutations (ET, P=0.024; PV, P=0.023; MF, P=0.001) were found in fewer young respondents. Conclusion: Compared with middle-aged and elderly patients, young patients with MPN had unique clinical and genetic characteristics.

The Combination of Navitoclax and Ruxolitinib in JAK Inhibitor-Naïve Patients with Myelofibrosis Mediates Responses Suggestive of Disease Modification

Background: Myelofibrosis (MF) is a myeloproliferative neoplasm associated with splenomegaly, high symptom burden, bone marrow fibrosis (BMF), and poor prognosis. The Janus kinase inhibitor (JAKi) ruxolitinib is the current standard of care for patients with MF. It improves splenomegaly and disease symptoms with limited impact on disease biology, highlighting an unmet medical need in MF. Driver mutations of JAK2, CALR, and MPL are key to the pathogenesis of MF. Reduction in variant allele frequency (VAF) of driver mutations and reversal of BMF are suggestive of disease modification (Pemmaraju, Cancer, 2022). Additionally, mutations in ASXL1, EZH2, SRSF2, IDH1/2, and U2AF1 p.Q157 are classified as high molecular risk (HMR) mutations associated with a worse prognosis (Arber et al., Blood, 2016). We previously demonstrated evidence of disease modification independent of HMR mutations by adding navitoclax to ruxolitinib in patients with suboptimal responses to ruxolitinib monotherapy (Pemmaraju, Lancet Oncology, 2022). Herein, we investigated whether the type of MF and risk (e.g., age, Dynamic International Prognostic Scoring System [DIPSS], and HMR) correlated with clinical outcomes and responses suggestive of disease modification (e.g., VAF reduction and improvement in BMF) among JAKi treatment-naïve patients with MF treated with the combination of navitoclax and ruxolitinib. Methods: Cohort-3 of the phase-2 multicenter REFINE study (NCT03222609) enrolled JAKi treatment-naïve patients with MF. Enrolled patients had primary or secondary MF with splenomegaly (DIPSS ≥ Intermediate-1) and did not receive prior JAK-2 therapy or bromodomain and extra terminal motif (BET) inhibitors. Patients initiated navitoclax at 100 mg QD or 200 mg QD if baseline platelet count was ≤ 150 × 109/L or > 150 × 109/L, respectively. Ruxolitinib was given BID with starting dose based on baseline platelet count per local label. The primary endpoint was spleen volume reduction of ≥ 35% (SVR35) from baseline at week 24, assessed by MRI conducted by central review. Key secondary and exploratory endpoints evaluated in this analysis were a reduction in BMF obtained from BM biopsies by local evaluation and a reduction in VAF for the driver gene mutations (JAK2V617, CALR, or MPL), respectively. Driver gene VAF and HMR mutations were determined in whole blood with the 50-gene Focus Myeloid next-generation sequencing panel (Interspace Pharma Solutions, Morrisville, NC, USA). Results: As of Feb 07, 2022, all enrolled patients (N = 32) treated with navitoclax and ruxolitinib were evaluable for biomarker analysis. The median duration of follow-up was 6.1 months (range, 1.9 – 18.6); median age was 69 years (range, 44 – 83), and median spleen volume was 1889.08 cm3 (range, 645.6 – 7339.6). At baseline, 22 (69%) patients had JAK2, 6 (19%) had CALR, and 3 (9%) had MPL mutations. One (3%) patient was triple negative. Nineteen (59%) patients had HMR mutations. SVR35 at week 24 was observed in all subgroups known to confer poor prognosis, including age (≥75 years, 50% [n = 4/8]), high DIPSS score (Intermediate-2, 63% [n = 12/19]; high, 33% [n = 1/3]), and HMR mutations (47% [n = 9/19]; Figure). BMF grade improvement was evaluable in 26/32 (81%) patients, of which 9/26 (35%) achieved ≥ 1-grade improvement at any time during treatment with a median time-to-improvement of 12.3 weeks (range, 12.1 – 24.1). Complete resolution of BMF was observed in 2/9 (22%) patients. The baseline BMF grades of these patients were 2 and 3. BMF ≥ 1-grade improvement was achieved by 7/13 (54%) patients with HMR mutations and 2/13 (15%) without HMR mutations. Reduction in driver gene JAK2V617 mutation VAF > 20% from baseline at week 12 or 24 was observed in 14/28 (50%) patients, and 5/14 (36%) patients achieved > 50% VAF reduction from baseline. There were no differences in > 20% VAF reductions from baseline to week 12 or 24 between those with or without HMR mutations (7/15 [47%] versus 7/13 [54%], respectively). Conclusions: Among JAKi treatment-naïve patients with MF, the combination of navitoclax and ruxolitinib reduced splenomegaly in several high-risk groups known to confer poor prognosis. Reductions in BMF and VAF were independent of HMR mutations. The reduction in BMF and VAF for the driver mutation JAK2V617 is encouraging and suggestive of evidence of disease modification with the combination of navitoclax and ruxolitinib. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Training and Validation Cohorts for Predicting the Impact of High Molecular Risk Mutations after Allogeneic Stem Cell Transplantation in Myelofibrosis

Introduction Myelofibrosis (MF) is the most aggressive form of Philadelphia negative myeloproliferative neoplasm and allogeneic hematopoietic stem cell transplantation (HSTC) is the only curative approach, but non relapse mortality limits the indication for HSTC to high-risk patients. The prognostic evaluation of MF patients is evolving during time together with a better understanding of the mutational landscape of this disease. The presence of high molecular risk (HMR) mutations, specifically ASXL1, SRSF2, EZH2, IDH1, IDH2 and U2AF1Q157, harbors a detrimental effect on survival and leukemic transformation and has been incorporated in different prognostic scoring systems. In this multicenter study we aimed to determine the impact of HMR mutations on transplant outcome. Methods We studied two independent cohorts of patients: 44 patients (training, retrospective cohort) were part of a multicenter, randomized GITMO (Gruppo Italiano Trapianti di Midollo Osseo) clinical trial (Patriarca F, BBMT 2019) and 29 patients (validation, prospective cohort) were subsequently recruited at the Bergamo Bone Marrow Transplant Unit. Patients from the training cohort (median age 56, range 36-66) were conditioned with busulfan-fludarabine or thiotepa-fludarabin while patients in the validation cohort (median age 61, range 36-67) were conditioned with a reduced intensity thiotepa-busulfan-fludarabin regimen. The mutational profile obtained on the pre-transplant DNA was performed by sequencing 30 myeloid related genes by applying SOPHia GENETICS Myeloid Solution on Illumina MiniSeq platform. Results In the training retrospective cohort, driver mutations were detected in 40 (29 JAK2/8 CALR/3 MPL) patients, with 4 patients having a triple negative MF. At least one HMR mutation was detected in 43% of patients and an unfavorable karyotype was present in 18% of patients. According to the Mutation-Enhanced International Prognostic Scoring System 70 plus (MIPPS70+) scoring system, 77% of patients were allocated in the high/very high groups. With a median follow up of 4.2 years (range 0.02-9), the 5-years Overall Survival (OS) and Progression Free Survival (PFS) were 61% and 45% respectively. The 5-years Non-Relapse Mortality (NRM) and Cumulative Incidence of Relapse (CIR) were 25% and 30%. In the prospective validation cohort, a driver mutation was detected in all patients (15 JAK2/7 CALR/7MPL). At least one HMR mutation was detected in 48% of patients and an unfavorable karyotype was present in 24% of patients. Patients allocated to the MIPPS70+ high/very group were 52%. After a median follow up of 10.7 months (range 0-44), the 2-years OS and PFS were 61% and 49% respectively. The 2-years NRM and CIR were 33% and 18%. In the training cohort, a higher risk of death and progression was observed in patients with high/very high risk MIPPS70+ prognostic index [HR for OS 4.3 (95% CI 0.6-33.1), HR for PFS 4.1 (95% CI 0.9-16.9)]. Conversely, the presence of HMR mutations did not significantly affect OS, PFS (Figure 1), NRM or CIR. The prognostic significance of MIPSS70+ risk classification was confirmed in the validation cohort, with a higher risk of death and progression for high/very high MIPSS70+ group [OS HR 3.2 (95% CI 0.4-27.1), PFS HR 3.8 (95% CI 0.5-31.4)]. Similarly, in the validation cohort the presence of HMR mutations did not affect transplant outcome, with no impact on OS, PFS (Figure 2), NRM or CIR. In the whole group of 73 patients, the presence of JAK2V617F mutation showed an adverse prognostic impact on CIR [HR 3.4 (95% CI 1-11.8)], while MIPPS70+ confirmed its role on PFS. Conclusions In this study we prospectively confirmed that the presence of HMR mutations did not impact on transplant outcome. Allogeneic stem cell transplantation can lead to a significant cure rate of MF patients, regardless the presence of HMR mutations. Patients in the high/very high MIPSS70+ risk group had a higher risk of death and progression after transplant. Appropriate timing and selection of patients is crucial for transplant outcome in MF. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

A Phase 2 Study of the LSD1 Inhibitor Bomedemstat (IMG-7289) for the Treatment of Essential Thrombocythemia (ET)

Many patients with ET are intolerant of or have an inadequate response to current standards of care (SOC) - hydroxyurea (HU), interferon, or anagrelide. Lysine-specific demethylase-1 (LSD1) is an enzyme critical for the self-renewal potential of malignant cells and hematopoietic differentiation, e.g., LSD1 licenses progenitors to mature into megakaryocytes, a cell central to ET pathogenesis. Bomedemstat is an orally active LSD1 inhibitor that reduced peripheral cell counts, splenomegaly, inflammatory cytokines, mutant cell burdens and improved survival in mouse models of MPNs (Kleppe et al. 2015; Jutzi et al. 2018). IMG-7289-CTP-201 is a global, open-label, Phase 2b study of bomedemstat taken once daily for 24+ weeks in patients with ET who are resistant to or intolerant of at least one SOC treatment (NCT04254978). Key eligibility criteria include the need for cytoreduction (age >60 or history of thrombosis), platelet count >450 x 109/L and hemoglobin ≥10 g/dL. Key objectives are safety and response, defined as platelets (plt) ≤400 x 109/L without new thromboembolic events. Exploratory endpoints include durability of response, reduction in WBCs, changes in mutant allele frequencies (MAF), and symptom improvement. Patients receive a starting dose of 0.6 mg/kg/d followed by dose titrations if necessary to a target platelet count of 200-400 x 109/L. At data cut-off (20Jun2022), 73 patients had enrolled. Median age was 66 (42-92) yrs; median time since diagnosis was 81 months (N=71), and 60 patients had previously been treated with HU. Of the patients most recently treated with HU (N=51), 90% met ELN criteria for resistance/intolerance. 64% (47/73) received 1 prior cytoreductive therapy with 36% (26/73) receiving between 2 and 4. The Day 1 mean (range) platelet, WBC and Hb values were 809 x 109/L (457-2220), 8.8 x 109/L (3.7-43.1), and 13.0 g/dL (9.4-16.5), respectively. Median (range) MPN-SAF TSS at baseline was 16 (0-74). 32% (23/73) and 11% (8/73) of patients had a history of bleeding or thromboembolic events respectively. Extended sequencing of 261 genes in 53 patients identified mutations in JAK2 (51%), CALR (36%), and MPL (4%). 32% had more than one mutation of which 41% were high molecular risk mutations (U2AF1, IDH1/2, NPM1, RUNX1, EZH2, ASXL1, TP53). Median time on treatment was 23 weeks (0.1-84). For patients treated ≥24 weeks, 94% (34/36) achieved a platelet count response ≤400x109/L, without new thromboembolic events, in a median time of 8 weeks (Figure). One patient was diagnosed with a pulmonary embolism. 83% of patients (30/36) treated for ≥24 weeks maintained their platelet count response for ≥12 weeks. Of the 7/36 (19%) patients with Day 1 WBC count >10x109/L, 100% of those treated for ≥24 weeks had a reduction in WBC count to ≤10x109/L (Figure); mean hemoglobin remained stable at ≥10 g/dL. In patients with baseline MPN-SAF TSS >20 (28/73), at Week 24, 79% (11/14) experienced an improvement with 64% (9/14) improving ≥10-points. The median baseline score for worst fatigue was 4.0 (N=73). By Week 24, the median fatigue score had improved to 3.0 (N=35). At Week 24, 67% (N=24) had a decrease in allele frequencies. No new mutations were found. In the safety population (N=73) the most common AEs (% patients, % patients with grade 3/4) regardless of causality were dysgeusia (43%, N/A), constipation (27%, 1%), fatigue (23%, 0%), thrombocytopenia (23%, 6%), arthralgia (21%, 3%), contusion (16%, 0%), and diarrhea (15%, 1%). Seventeen patients reported serious AEs (SAE), with related events (per the PI) in 2 patients. Fifteen patients discontinued treatment, 9 due to AEs (3 for dysgeusia), 3 subject decision, 1 investigator decision, 1 disease progression to MF, and 1 unrelated death due to aspiration pneumonia. There have been no safety signals or deaths related to drug. At the data cut-off date, 80% (58/73) of patients remain on study. With this additional follow-up data, bomedemstat, in this ET patient population, continues to be generally well-tolerated, improves symptoms, reduces the mutation burden and, importantly durably reduces platelets and WBCs without adversely affecting hemoglobin. Based on these data, a Phase 3 study of bomedemstat for the treatment of ET is being planned. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Peripheral Blood Cytotoxic T Cells from Myelofibrosis Patients Show Early Exhausted Features Targetable By CTLA-4 Inhibition

Introduction: Myelofibrosis (MF), either primary or secondary, belongs to Philadelphia-negative myeloproliferative neoplasms (MPN) and is characterized by bone marrow fibrosis, hematopoietic stem cell mobilization and extramedullary hematopoiesis. Compelling evidence are suggesting that persistent antigen stimulation in the tumor microenvironment can differentiate T effector cells into terminally exhausted T cells, a functional state characterized by decrease in proliferation, cytotoxicity, and cytokine production. Innovative therapies aim at reversing the exhausted state through immune checkpoint inhibition to recover the immune response against the tumor. Even in myeloid neoplasms such as MPNs, T cells are showing dysfunctional features; thus we investigated T cell exhaustion in MF to assess the possibility of immune checkpoint inhibition as a new effective therapy. Methods: Peripheral blood mononuclear cells (PBMCs) were isolated from 44 MF patients and 22 healthy donors (HD). CD3+CD8+ T cells were characterized by multicolor flowcytometry to assess surface expression of the following inhibitory receptors (IRs): PD-1, CD244, CD160, TIM-3, LAG-3, CTLA-4. Results were correlated with clinical features such as Dynamic International Prognostic Scoring System (DIPSS) classification, splenomegaly, high-molecular risk (HMR) mutation number and other negative prognostic factors. We performed intracellular flowcytometry staining to assess residual cytokine production in PBMCs stimulated overnight with anti-CD3, anti-CD28 and Brefeldin A. Total cellular RNA was isolated from granulocytes of 141 primary and secondary MF patients and 28 HDs, and we performed Gene expression profiling (GEPs) by microarray platform to evaluate IRs-ligands expression. To test the possible inhibitory effect of the neoplastic clone we cultured T cells either alone or in co-culture with the myeloid cells for 4 days in the presence of anti-CD3/CD28 stimulatory beads, SCF, TPO, FLT3l, IL6, IL7 and IL15 and then we tested the activation marker OX40 expression level. The co-culture system was also used to test the effect of CTLA-4 inhibition. Results: We observed increased expressions of PD-1, CD244, CTLA-4 and CD160 on cytotoxic T cells from MF patients together with the expansion of PD-1+CD57- cytotoxic T cell populations (Panel A), which also showed increased expression of all the IRs assessed, with CD160 and CTLA-4 being the more significantly upregulated. Higher levels of PD-1, CD244, CD160, CTLA-4, LAG-3 or TIM-3 on cytotoxic T cells correlate with detrimental features like splenomegaly, low hemoglobin levels, HMR mutation number and more severe DIPSS classification. Moreover, we observed decreased secretion of IFNɣ and TNFɑ by total CD3+CD8+ T cells and PD1+ subpopulation from MF patients (Panel B). A significant reduction of Granzyme B production was observed mainly in patients with expansion of PD1+CD57- exhausted T cells. GEPs analysis highlighted increased expression of IR-ligands like CD274, CEACAM1, CD48, CD80 on granulocytes from MF patients compared to HDs. While cytotoxic T cells from HDs were effectively activated either alone or in co-culture with myeloid cells, the activation of cytotoxic T cells from MF patients was damped in presence of myeloid cells and restored when T cells were cultured alone. Treatment with anti-CTLA-4 was able to partially restore the MF T cells activation potential in the presence of myeloid cells. Conclusions: Our data evidenced in MF patients the presence of an impaired population of peripheral blood cytotoxic T cells expressing multiple IRs and with reduced cytokine production after in vitro activation. Clinical correlations suggest a more severe disease in patients with higher IRs expression on cytotoxic T cells. Moreover, granulocytes from MF patients display higher level of IR-ligands transcripts suggesting an immunosuppressive interplay between the myeloid neoplastic clone and T cells. This was also suggested by reduced activation level of T cells in co-culture with myeloid cells that was restored by removing of myeloid cells or with anti-CTLA-4 treatment. Taken together this data highlights an exhausted state likely implicated in immune escape that could be targeted and potentially reverted by immune checkpoint inhibitions. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Splenic Irradiation Prior to Allogeneic Hematopoietic Cell Transplantation for Patients with Myelofibrosis

Background: Myelofibrosis (MF) is a clonal stem cell neoplasm characterized by excess fibrous tissue formation in the bone marrow. Allogeneic hematopoietic cell transplantation (HCT) is the only curative treatment for MF. Patients with MF often have compensatory splenic extramedullary hematopoiesis leading to splenomegaly, which is associated with delayed engraftment and decreased survival post-HCT. Several Janus kinase (JAK) inhibitors are approved to treat splenomegaly and systemic symptoms in MF patients. However, JAK inhibitor therapy does not always lead to complete resolution of splenomegaly. Therefore, splenic irradiation (RT) prior to HCT may benefit patients with persistent splenomegaly, yet research investigating outcomes of this therapeutic approach is limited. Methods: We conducted a single-center, retrospective cohort study of MF patients to characterize the feasibility of splenic RT and assess engraftment rates and post-transplant outcomes with this approach. Forty-eight MF patients who underwent HCT at Massachusetts General Hospital between 2011 to 2021 were identified using an institutional transplant database. Patient disease- and transplant-related characteristics were summarized according to splenic RT within 3 months prior to transplant. Results: Baseline disease- and transplant-related characteristics are displayed in Table 1. Among all patients, twenty-nine (60%) were male, and the median age was 67 years (range, 53-77). All patients received reduced intensity conditioning, with a majority (81%) receiving fludarabine with melphalan. Seventy-three percent of patients had a JAK2 mutation and 46% received ruxolitinib (RUX) prior to HCT. A total of 17 (35%) patients received splenic RT prior to transplant. Splenic RT ranged from 2 daily doses of 1 Gy to 5 daily doses of 1.5 Gy, with total radiation ranging from 2 Gy to 7.5 Gy. Splenic RT was administered at a median of 13 days prior to transplant (range, 7-69 days). All splenic RT patients had splenomegaly prior to transplant, and 11 (65%) were treated with RUX prior to HCT. Patients receiving splenic RT had significantly larger spleen sizes prior to transplant (23.1 v. 17.3 cm, p<0.01), and were more likely to have at least one high molecular risk (HMR) mutation than patients in the no RT group (83% v. 33%, p=0.01). For the entire cohort, the median days to neutrophil engraftment and platelet engraftment was 14 and 23, respectively. Among splenic RT patients, there was one case of primary graft failure and one case of secondary graft failure. The median days to neutrophil engraftment was 15 (IQR, 13-19) for the RT group and 13 (IQR, 12-14) for the no RT group (p=0.07). The median days to platelet engraftment was 32 (IQR, 25-108) for the RT group and 22 (IQR, 18-25) for the no RT group (p<0.01). Three splenic RT patients (18%) died early without platelet engraftment. When RUX was accounted, patients with RT and RUX had a substantially delayed platelet engraftment compared to no RT and/or no RUX (69.5 days vs 19.5-22.5 days, p=0.03) [Figure 1]. For the entire cohort, the 3-year overall survival (OS) and progression-free survival (PFS) was 67% (95%CI: 50%-79%) and 61% (95%CI: 45%-74%), respectively. The cumulative incidence of non-relapse mortality (NRM) and relapse was 26% (95%CI: 13%-40%) and 13% (95%CI: 5%-24%), respectively. Despite delayed platelet engraftment, survival outcomes were not different between RT and no RT, regardless of pre-HCT RUX exposure. Conclusion: Splenic RT administration prior to HCT appears feasible and associated with acceptable engraftment and clinical outcomes for MF patients with splenomegaly at the time of transplant. The persistence of massive splenomegaly at transplant following pre-transplant RUX is likely indicative of higher risk disease and remains associated with longer time to platelet engraftment, despite the addition of splenic RT. Larger prospective studies are required to fully assess the clinical impact of splenic RT in the transplant setting, especially in combination with other therapeutic strategies. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

A Phase Ib Dose-finding Study of Panobinostat and Ruxolitinib in Myelofibrosis.

A Phase Ib Dose-finding Study of Panobinostat and Ruxolitinib in Myelofibrosis.