Vannucchi, Alessandro M.

Abstract Introduction: Thrombocytopenia, a hallmark of cytopenic myelofibrosis (MF), is associated with poor survival and quality of life impairment. Patients with MF and moderate or severe thrombocytopenia (platelet counts <100x10 9/L, <50x10 9/L) tend to have high symptom burden as measured by the Total Symptom Score (TSS), driven largely by physical functioning symptoms (Mesa R et al, ASH 2021 abstract in submission). Pacritinib, an investigational JAK2/IRAK1 inhibitor, was studied in patients with platelet counts ≤100x10 9/L in the PERSIST-2 trial. Unlike the pivotal studies upon which available JAK1/2 inhibitors were approved that relied on a modified TSS version that excluded 'tiredness' from the response analysis, PERSIST-2 included 'tiredness' as part of TSS and found response rates of 25% for pacritinib vs. 14% for best available therapy (BAT), P=0.08. Here, we retrospectively analyzed TSS on PERSIST-2 using the modified scoring system. In addition, we evaluated the impact of pacritinib and BAT, including ruxolitinib, on MF symptoms including 'tiredness' and 'inactivity'. Methods: All PERSIST-2 patients in the intention-to-treat population randomized at least 22 weeks prior to the end of the study were included. PERSIST-2 randomized patients 1:1:1 to pacritinib 200mg BID, pacritinib 400mg daily, or BAT (including ruxolitinib). The modified TSS score was calculated as the sum of individual symptom scores for early satiety, abdominal discomfort, rib pain, night sweats, itching, and bone pain ('tiredness' and 'inactivity' were not included), and response was defined as a ≥50% reduction in score from baseline to week 24. Symptoms were categorized as physical function-related (tiredness, inactivity), spleen-related (satiety, abdominal discomfort, rib pain), or cytokine-related (sweats, itching, bone pain). The Wilcoxon Rank Sum test was used to compare differences in scores. Results: The analysis included 74 patients randomized to pacritinib 200mg BID and 72 to BAT; an additional 75 were randomized to pacritinib 400mg QD (dose no longer in development). At baseline, 39% had moderate and 46% had severe thrombocytopenia. Ruxolitinib was selected as BAT in 45% of patients with moderate and 38% with severe thrombocytopenia. The co-primary endpoint for the study - TSS response rate in pooled pacritinib arms versus BAT - showed a significant difference using the modified TSS: 30% vs. 14%, P=0.008. Similarly, the modified TSS response rate was higher for patients treated with pacritinib 200mg BID compared to BAT (35% vs. 14%, P=0.004, Figure 1a). Among patients on the BAT arm, modified TSS response rates were modestly higher for patients who received ruxolitinib prior to week 24 (19% [n=6/32]) compared to those who did not (10% [n=4/40]), though both were lower than response rates with pacritinib. Patients on the pacritinib 200mg BID arm experienced greater percentage reductions in individual myelofibrosis symptoms between baseline and week 24 compared to BAT, both in patients with moderate and severe thrombocytopenia (Figure 1b, 1c). For physical function symptoms, severity was reduced more on pacritinib 200mg BID compared to BAT by week 24 (median reduction in tiredness: 30% vs. 13%, P=0.0261; inactivity: 22% vs. 7%, P=0.099). Among patients with severe thrombocytopenia, symptom improvement was minimal on BAT (Figure 1b). Conclusion: The symptom benefit of pacritinib in patients with moderate and severe thrombocytopenia is demonstrated in the PERSIST-2 study. A significant reduction in symptoms was observed in patients treated with pacritinib 200mg BID, the dose being studied in an ongoing Phase 3 trial (PACIFICA), compared to BAT. Furthermore, the modified TSS response rate of 35% in patients treated with pacritinib 200mg BID is comparable to that reported for approved JAK1/2 inhibitors in patients with higher platelet counts, suggesting the potential for pacritinib to address the unmet need of patients with cytopenic myelofibrosis. Figure 1 Figure 1. Disclosures Palmer: CTI BioPharma: Consultancy, Research Funding; Protagonist: Consultancy, Research Funding; Incyte: Research Funding; PharmaEssentia: Research Funding; Sierra Oncology: Consultancy, Research Funding. Mesa: Incyte Corporation: Consultancy, Research Funding; Samus: Research Funding; Sierra Oncology: Consultancy, Research Funding; CTI: Research Funding; Novartis: Consultancy; Celgene: Research Funding; Pharma: Consultancy; La Jolla Pharma: Consultancy; Constellation Pharmaceuticals: Consultancy, Research Funding; CTI: Research Funding; Abbvie: Research Funding; Gilead: Research Funding; Genentech: Research Funding; Promedior: Research Funding; AOP: Consultancy. Oh: Abbvie: Membership on an entity's Board of Directors or advisory committees; Blueprint Medicines: Membership on an entity's Board of Directors or advisory committees; Celgene Bristol Myers Squibb: Membership on an entity's Board of Directors or advisory committees; Constellation: Membership on an entity's Board of Directors or advisory committees; CTI Biopharma: Membership on an entity's Board of Directors or advisory committees; Disc Medicine: Membership on an entity's Board of Directors or advisory committees; Geron: Membership on an entity's Board of Directors or advisory committees; Incyte: Membership on an entity's Board of Directors or advisory committees; Kartos Therapeutics: Membership on an entity's Board of Directors or advisory committees; PharamaEssentia: Membership on an entity's Board of Directors or advisory committees; Sierra Oncology: Membership on an entity's Board of Directors or advisory committees. Rampal: Sierra Oncology: Consultancy; Novartis: Consultancy; BMS/Celgene: Consultancy; Stemline: Consultancy, Research Funding; Jazz Pharmaceuticals: Consultancy; Constellation: Research Funding; Kartos: Consultancy; Disc Medicine: Consultancy; Blueprint: Consultancy; Pharmaessentia: Consultancy; Incyte: Consultancy, Research Funding; Memorial Sloan Kettering: Current Employment; Abbvie: Consultancy; CTI: Consultancy. Buckley: CTI Biopharm: Current Employment. Roman-Torres: CTI Biopharm: Current Employment. Verstovsek: Protagonist Therapeutics: Research Funding; Genentech: Research Funding; Gilead: Research Funding; Incyte Corporation: Consultancy, Research Funding; Celgene: Consultancy, Research Funding; NS Pharma: Research Funding; AstraZeneca: Research Funding; Blueprint Medicines Corp: Research Funding; CTI BioPharma: Research Funding; Promedior: Research Funding; Ital Pharma: Research Funding; PharmaEssentia: Research Funding; Roche: Research Funding; Novartis: Consultancy, Research Funding; Sierra Oncology: Consultancy, Research Funding; Constellation: Consultancy; Pragmatist: Consultancy. Mascarenhas: Sierra Oncology: Consultancy, Membership on an entity's Board of Directors or advisory committees; Merck: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Merus: Research Funding; Geron: Consultancy; Gilead: Consultancy, Membership on an entity's Board of Directors or advisory committees; PharmaEssentia: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Roche: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Forbius: Research Funding; Genentech/Roche: Consultancy, Membership on an entity's Board of Directors or advisory committees; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Geron: Consultancy, Research Funding; Constellation: Consultancy, Membership on an entity's Board of Directors or advisory committees; Promedior: Consultancy, Membership on an entity's Board of Directors or advisory committees; Kartos: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; AbbVie: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene/BMS: Consultancy, Membership on an entity's Board of Directors or advisory committees; Incyte: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Prelude: Consultancy; Galecto: Consultancy; CTI Biopharm: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding. Vannucchi: AbbVie: Membership on an entity's Board of Directors or advisory committees; Bristol Myers Squibb: Honoraria, Membership on an entity's Board of Directors or advisory committees; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees; Incyte Corporation: Honoraria, Membership on an entity's Board of Directors or advisory committees. Kiladjian: CTI BioPharma: Membership on an entity's Board of Directors or advisory committees, Research Funding; AP Orphan: Membership on an entity's Board of Directors or advisory committees; Incyte: Membership on an entity's Board of Directors or advisory committees; AbbVie: Membership on an entity's Board of Directors or advisory committees; Celgene/BMS: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees; PharmaEssentia: Membership on an entity's Board of Directors or advisory committees. Harrison: Galacteo: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Promedior: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Constellation Pharmaceuticals: Research Funding; Incyte Corporation: Speakers Bureau; Roche: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Janssen: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; BMS: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Keros: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Shire: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Abbvie: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; AOP Orphan Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Sierra Oncology: Honoraria; Gilead Sciences: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Geron: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; CTI BioPharma: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Novartis: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau. Bose: Novartis: Honoraria; NS Pharma: Research Funding; Pfizer: Research Funding; Constellation Pharmaceuticals: Research Funding; Blueprint Medicines: Honoraria, Research Funding; Kartos Therapeutics: Honoraria, Research Funding; Incyte Corporation: Honoraria, Research Funding; Promedior: Research Funding; CTI BioPharma: Honoraria, Research Funding; Sierra Oncology: Honoraria; Astellas: Research Funding; BMS: Honoraria, Research Funding; Celgene Corporation: Honoraria, Research Funding. Craig: CTI BioPharma: Current Employment. Gerds: PharmaEssentia Corporation: Consultancy; CTI BioPharma: Research Funding; Sierra Oncology: Consultancy; AbbVie: Consultancy; Celgene/Bristol Myers Squibb: Consultancy; Constellation: Consultancy; Novartis: Consultancy.

Abstract Background In addition to its influence on survival, leukocytosis in myeloproliferative neoplasms (MPN) has also been implicated as a risk factor for thrombosis, including venous thrombosis in PV (Blood Cancer J, 2017;7:662) and arterial thrombosis in ET (Blood. 2011;117:5857). In the current study, we sought to clarify the individual prognostic contribution of absolute neutrophil (ANC), lymphocyte (ALC) and monocyte (AMC) counts, for arterial and venous thrombotic events in essential thrombocythemia (ET) and polycythemia vera (PV). Methods The current study included 487 patients with ET (n=349) or PV (n=138), recruited from the Mayo Clinic MPN database, based on availability of information on ANC, ALC and AMC. Conventional criteria were used for diagnosis (Blood 2016;127:2391) and definitions of major vascular events (Blood Cancer J. 2018;8:25). Conventional statistical models were applied using JMP Pro 14.0.0 software package, SAS Institute, Cary, NC. Multivariable analyses included previously established risk factors for arterial or venous thrombosis. Results Essential thrombocythemia patients: 349 patients (median age 57 years, range 18-89; females 61%) with ET were included in the study: 46% JAK2, 34% CALR, 16% triple-negative and 4% MPL mutated; IPSET risk category high 24%, intermediate 41%, and low 35%; presenting median (range) values were 13.8 g/dL (11.1-16.4) for hemoglobin, 8.2 x 10(9)/L (3.2-52) for leukocyte count, and 859 x 10(9)/L (451-3460) for platelet count; palpable splenomegaly was present in 48 (14%) patients and cardiovascular risk factors in 56%; median follow-up was 10 years (range 0-47). There were 38 (11%) documented venous events at diagnosis and 31 (9%) after diagnosis and 42 (12%) arterial events at diagnosis and 64 (18%) after diagnosis. Polycythemia vera patients: 138 patients (median age 62 years, range 20-94; females 50%) with PV were included in the study; presenting median (range) values were 17.9 g/dL (16.1-24) for hemoglobin, 11.8 x 10(9)/L (2.7-65.8) for leukocyte count, and 434 x 10(9)/L (44-1679) for platelet count; 57% of patients presented with leukocytosis >11 x 10(9)/L; palpable splenomegaly was present in 37 (27%) patients; abnormal karyotype was documented in 17% of patients. Median follow-up was 11 years (range 0.03-36.7). There were 22 (16%) documented venous events at diagnosis and 21 (16%) after diagnosis and 28 (20%) arterial events at diagnosis and 15 (11%) after diagnosis. ANC/ALC/AMC associations with thrombosis in ET and PV: In both ET and PV, ANC/ALC/AMC did not correlate with arterial thrombosis at/prior to diagnosis (p>0.1 in all instances). By contrast, in both ET and PV, higher ANC (p=0.05 and 0.04, respectively) and higher AMC (p=0.005 and 0.07), but not ALC (p=0.6 and 0.7), were correlated with venous thrombosis at/prior to diagnosis. Arterial thrombosis-free survival was not affected by ANC/ALC/AMC in either ET or PV (p>0.1 in all instances). By contrast, venous thrombosis-free survival in both ET and PV was compromised by higher ANC (p=0.05 and 0.003, respectively), but not ALC or AMC. The significant association between higher ANC and inferior venous thrombosis-free survival in both ET (p=0.01) and PV (p=0.007) was sustained during multivariable analysis that included history of venous thrombosis, age and sex; the only other variable of significance was older age in ET (p<0.001). The significant association between ANC and venous thrombosis-free survival was also noted in an external cohort of PV patients from the University of Florence (n=576). Conclusions: The current study identifies ANC as having a direct correlation with venous thrombosis in both ET and PV, independent of currently known risk factors. An additional risk contribution from AMC was apparent for events occuring at or prior to but not after diagnosis. Taken together, these observations flag both neutrophils and monocytes as potential contributors to venous but not arterial thrombosis in MPN, at least not by themselves. Additional collaborative studies are ongoing in order to integrate and reconcile our observations in the context of neutrophil/lymphocyte ratio (Carobbio et al) and JAK2V617F allele burden (Loscocco et al), on venous thrombosis-free survival in PV, reported in concomitantly submitted ASH 2021 abstracts, especially in light of the relatively small number of events in the current study. Disclosures Barbui: Novartis: Membership on an entity's Board of Directors or advisory committees, Research Funding; AOP Orphan: Membership on an entity's Board of Directors or advisory committees, Research Funding. Vannucchi: AbbVie: Membership on an entity's Board of Directors or advisory committees; Incyte Corporation: Honoraria, Membership on an entity's Board of Directors or advisory committees; Bristol Myers Squibb: Honoraria, Membership on an entity's Board of Directors or advisory committees; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees.

Abstract Background Current NCCN and ELN guidelines lack supporting evidence in regards to initiation of cytoreductive therapy in essential thrombocythemia (ET) with extreme thrombocytosis (ExT) ≥1500 x 10 9/L (NCCN guidelines: myeloproliferative neoplasms, version 2. 2019, Barbui, Leukemia, 2018).; we sought to determine prevalence and establish phenotype and genotype correlates for ET with ExT and assess its impact on thrombotic and bleeding events, in the context of aspirin therapy or cytoreduction. Methods 1,249 WHO-defined ET patients evaluated over five decades (1967-2021) were retrospectively recruited from the Mayo Clinic. Conventional criteria were used to define major arterial and venous thrombosis and major hemorrhage. Conventional statistical methods were applied using JMP Pro 14.0.0 software package, SAS Institute, Cary, NC. Results i) Phenotype and genotype correlates Among 1,249 consecutive patients with ET, 104 (8%) displayed Ext ≥1500 x 10 9/L, at time of initial diagnosis; these patients were characterized by younger age (median 47 vs 59 years; p<0.001) female gender (80% vs 62%; p<0.001), CALR mutation (39% vs 25%; p=0.004), lower hemoglobin (median 13.1 vs 13.7 g/dl; p<0.0001), leukocytosis ≥11 x 10 9/l (42% vs 23%; p<0.0001), and palpable splenomegaly (22% vs 14%; 0.03); multivariable analysis confirmed associations with age, anemia, leukocytosis, and CALR mutation. Acquired von Willebrand syndrome was reported in 4/9 (44%) vs 27/78 (35%) tested patients, with or without Ext ≥1500 x 10 9/L, respectively (p=0.57); however, comparison using platelet ≥1000 x 10 9/L resulted in near-signficant difference (46% vs 29%; p=0.11). NGS was performed in 297 patients and showed a non-sigificant association with U2AF1 mutations (5% vs 0.4%; p=0.11). ExT ≥1500 x 10 9/L was present in 25/986 (3%), 42/891 (5%), and 15/558 (3%) in the validation cohort; the limited number of cases precluded comparative analyses. ii )Correlation with vascular events at/prior to diagnosis Arterial or venous thrombosis at/prior to diagnosis occurred in 190 (15%) and 111 (9%) patients, respectively, and major hemorrage in 50 (4%). Ext ≥1500 x 10 9/L was associated with major hemorrhage (HR 2.9; 1.3-6.3), but not with arterial (p=0.15) or venous (p=0.41) thrombotic events, at/prior to diagnosis. Instead, multivariable analysis for events at/prior to diagnosis identified male gender (p=0.02), JAK2 mutation (p=0.01), and cardiovascular risk factors (p=0.001) as risk factors for arterial thrombosis and JAK2 mutation (HR 2.8; 1.4-5.7) as a risk factor for venous thrombosis. iii ) Correlation with vascular events after diagnosis At median follow-up of 10 years, arterial or venous thrombosis occurred in 222 (18%) and 97 (8%) patients, respectively, and major hemorrage in 128 (11%). Ext ≥1500 x 10 9/L at diagnosis was not associated with arterial (p=0.35) or venous (p=0.23) thrombosis-free survival or hemorrhage-free survival (p=0.24). Instead, multivariable analysis identified age >60 years, presence of cardiovascular risk factors, and history of arterial thrombosis, as risk factors for arterial thrombosis-free survival; and male gender and history of venous thrombosis as risk factors for venous thrombosis-free survival; and age >60 years and leukocytosis of ≥11 x 10 9/L as risk factors for hemorrhage-free survival. In addition, aspirin therapy was idependently protective of venous thrombosis (HR 0.5; 0.2-0.9), and also of arterial thrombosis, in univariate analysis (HR 0.6; 0.3-0.9), without being associated with an increased risk of major hemorrhage (p=0.64); by contrast, beneficial effect from cytoreductive therapy was not evident for either arterial (p=0.37) or venous (p=0.77) thrombosis. In low-risk patients with Ext ≥1500 x 10 9/L, both aspirin and cytoreductive therapy were protective of venous events (Figure 1), without affecting hemorrhage-free survival. Conclusion ExT ≥1500 x 10 9/L in ET was associated with major hemorrhage at diagnosis but did not affect thrombosis-free or hemorrhage-free survival. Initial therapy with aspirin and/or cytoreductive therapy was protective of venous events in ET patients with ExT ≥1500 x 10 9/L, including those with low-risk disease, without enhancing the risk of hemorrhage. The limited number of informative cases with ExT in the validation cohort, underscore the foreseeable challenges associated with controlled studies. Figure 1 Figure 1. Disclosures Szuber: Novartis: Honoraria. Vannucchi: AbbVie: Membership on an entity's Board of Directors or advisory committees; Bristol Myers Squibb: Honoraria, Membership on an entity's Board of Directors or advisory committees; Incyte Corporation: Honoraria, Membership on an entity's Board of Directors or advisory committees; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees. Barbui: AOP Orphan: Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Membership on an entity's Board of Directors or advisory committees, Research Funding.

Abstract Background. The tendency towards thrombosis in myeloproliferative neoplasms (MPNs) is linked to the JAK2-mutant clone which leads to hypercellularity and functional interplay between abnormal erythrocytes, platelets, leukocytes and dysfunctional endothelium. The resulting cell activation that also involves stromal cells in their microenvironment, has been shown associated with chronic, systemic, subclinical pro-inflammatory state, and has been implicated in the pathogenesis of thrombosis in MPN. Neutrophil to lymphocyte ratio (NLR) is a novel inflammatory marker found to be associated with the severity and prognosis of cardiovascular diseases but there is little evidence for its prognostic significance in MPN. We investigated whether NLR could predict the onset of arterial and venous thrombosis in polycythemia vera (PV). Methods. Subjects of this study were 1508 patients included in the ECLAP trail with NLR evaluation available. In addition to standard statistical methods, we used proportional hazards additive models (GAM) as they can provide an excellent fit in the presence of nonlinear relationships, for the prediction of total, arterial and venous thrombosis as smooth functions with cubic splines of different blood parameters. Results. After a median follow-up of 2.76 years, 169 thrombotic events (10.3%) were objectively diagnosed and analyzed: 87 arterial (MI, Stroke, TIA, PAT) and 88 venous thrombosis (DVT±PE, superficial thrombophlebitis). In univariate analysis, arterial thrombosis was associated with age (p=0.003) and previous thrombosis, especially if arterial (p<0.001), and with the presence of at least one cardiovascular risk factor (p=0.009). No association between baseline platelet and leukocyte counts and NLR with arterial events was found. Conversely, in venous thrombosis, beside age (p=0.039) and history of venous thrombosis (p<0.001), additional risk factors were low hemoglobin (p=0.039) and increasing values of NLR (p=0.002) resulting from a simultaneous increase of neutrophils (p=0.002) and to a decrease of absolute number lymphocytes (p=0.002).To predict outcomes, we tested total leukocytes, neutrophils, lymphocytes, platelets and NLR by GAM to evaluate their trend in continuous scale of thrombotic risk. A significant association between the risk of venous thrombosis and the progressive lower counts of lymphocytes (p=0.002) emerged, leading to increase the NLR values (p=0.005). However, given the greater precision of the NLR estimates and the markedly wide confidence interval of lymphocyte counts estimates, NLR was used in multivariate model. Conversely, neither absolute values of neutrophils and lymphocytes nor NLR were found associated with arterial events.In multivariate model, adjusted for age, gender and treatments at baseline, the risk of venous thrombosis was independently associated with previous venous events (HR=5.48, p ≤0.001) and NLR values ≥5 -the best cut-off resulted applying the Liu's method (HR=2.13, p=0.001). NLR effect for total venous thrombosis was not modified by excluding superficial venous thrombosis (HR=2.90, p=0.001) in a sensitivity analysis. Older age (i.e., ≥65 years, HR=1.88, p=0.005) and previous arterial thrombosis (HR=1.92, p=0.003) retained the prognostic statistical significance for arterial thrombosis.Our learning cohort findings, indicating a correlation between NLR values and venous thrombosis, have been validated in two Italian independent external cohorts (Florence, n=282 and Rome, n=173) of contemporary PV patients (Figure 1). Conclusions. The NLR is an inexpensive and easily accessible test compared to other inflammatory markers. We found that NLR-alone is an independent predictor of venous thrombosis and could be included in a new scoring system. In addition to guiding the stratification of thrombotic risk, these data confirm that inflammation is a relevant target of antithrombotic therapy in PV. Figure 1 Figure 1. Disclosures Vannucchi: Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees; BMS: Honoraria, Membership on an entity's Board of Directors or advisory committees; Incyte: Honoraria, Membership on an entity's Board of Directors or advisory committees; AbbVie: Membership on an entity's Board of Directors or advisory committees. Barbui: AOP Orphan: Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Membership on an entity's Board of Directors or advisory committees, Research Funding.

Abstract Introduction: Myelofibrosis -either primary (PMF) or post-polycythemia vera/essential thrombocythemia (collectively, secondary MF [SMF])- is characterized by biologic and clinical heterogeneity, with some patients (pts) presenting with features of myeloproliferation (MyP) and others exhibiting a myelodepletive (MyD) phenotype. Although not well defined, the latter is marked by cytopenias involving one or more hematopoietic lineages, in some respects mimicking a myelodysplastic or bone marrow (BM) failure syndrome. MyD features have been associated with poor prognosis in patients with MF, but cytopenias have been usually considered individually. In the current study, we aimed at investigating the phenotypic and prognostic correlates of a MyD phenotype in a large cohort of MF patients. Methods: After IRB approval, 704 consecutive patients with WHO-defined MF referring to CRIMM (Florence), were included in the study. There were 442 (63%) PMF and 262 (37%) SMF. Cytopenias at diagnosis were defined as follows: white blood cell (WBC) <4×10 9/L, hemoglobin (Hb) <11 g/dL for male and <10 g/dL for female, platelets (Plt) <100×10 9/L. A MyD phenotype was defined by the presence of at least one cytopenia in the absence of any increase of other blood cells (WBC >15×10 9/L, Hb >16.5 g/dL for male and >16 g/dL for female, Plt >450×10 9/L). Pts not included in the MyD group were considered as having a MyP phenotype. Mutational analysis by targeted NGS was available for 594/704 patients (PMF 368/442; SMF 226/262). Results: Overall, 166 pts were diagnosed as having a MyD MF, including 108 (24%) PMF and 58 (22%) SMF. Among PMF patients, leukopenia, sex-adjusted anemia and thrombocytopenia were present in 38%, 84% and 35%, respectively; in SMF, corresponding figures were 24%, 91% and 24%. Two or more cytopenias were found in 11% and 6% of PMF and SMF patients, respectively. In PMF, a MyD phenotype was associated with male gender (P=.0468), older age (P=.0002), lower peripheral blast count (P=.0006), higher prevalence of splenomegaly (P=0.0142), constitutional symptoms (P<.0001), and BM fibrosis grade ≥2 (P<.0001). The rates of thrombosis and bleeding were not different compared to MyP PMF. MyD pts were more likely to have very high risk (VHR) karyotype abnormalities (P=.0002) and to be triple negative (TN; P<.0001); there were no correlations with JAK2 mutation status and mutant burden, CALR and MPL mutations. Among non-driver mutations, a MyD phenotype was significantly enriched in ASXL1 (P=.0074), IDH1/2 (P=0.064), N/KRAS (P=.0014), U2AF1 (P<.0001), and CUX1 (P=.0002) mutations. Karyotype abnormalities (P=.0084), VHR cytogenetics (P=.0343), CBL (P=.0.171) and U2AF1 (P=.0148) mutations were significantly enriched in MyD pts with ≥2 cytopenias. On univariate analysis, OS was significantly shorter in pts with MyD vs MyP PMF (median, 55 vs 103 months, respectively; P<.0001), and not different between MyD pts with one (median, 65 months) and ≥2 (median, 44 months) cytopenias (Fig. 1A). After competing risk analysis, the cumulative incidence of leukemic transformation (LT) was not different between MyD and MyP phenotypes (16% vs 11% at 5 years, respectively). Phenotypic differences between MyD and MyP patients were less evident in SMF, a part for older age of the former (P=.0207). The molecular background was likewise different: a MyD feature was enriched in mutations in TP53 (P=.0024), U2AF1 (P<.0001), and SETBP1 (P=.0125). TP53 mutations were remarkably more frequent in MyD SMF pts with ≥2 cytopenias (19%). Pts with MyD SMF had a significantly shorter OS compared to the MyP counterpart (median, 44 vs 105 months; P<.0001). Median OS was significantly inferior in MyD patients with ≥2 cytopenias compared to one cytopenia (median, 27 vs 58 months, respectively; P<.0001) (Fig. 1B). The cumulative incidence of LT was not different: 16% vs 7% at 5 years, respectively, for SMF pts with MyD and MyP phenotype. Conclusion: The current study provides a comprehensive analysis of the MyD phenotype in pts with PMF and SMF, partly recapitulating findings of previous studies (Marcellino BK et al. Clin Lymphoma Myeloma Leuk 2020). We showed that the MyD phenotype is associated with high-risk clinical and molecular features, particularly in PMF, and correlates with inferior OS. Of interest, U2AF1 mutations emerged as a distinct molecular marker of MyD in both PMF and SMF, while mutations in TP53 appear prevalent in MyD SMF. Figure 1 Figure 1. Disclosures Vannucchi: Incyte: Honoraria, Membership on an entity's Board of Directors or advisory committees; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees; BMS: Honoraria, Membership on an entity's Board of Directors or advisory committees; AbbVie: Membership on an entity's Board of Directors or advisory committees.

Abstract Background The recent association of cerebral venous thrombosis (CVT) with COVID-19 vaccinations (JAMA; 2021; 325, N Engl J Med 2021; 384) motivated the current review of CVT and MPN. Our objectives were, i) provide an estimation of the incidence of CVT in the context of MPN, followed by a description of clinical phenotype and therapeutic strategies, ii) determine long term outlook in terms of recurrent thromboses, hemorrhage, and survival, iii) identify salient features which distinguish MPN associated from COVID vaccine- related CVT. Methods 74 consecutive MPN patients with CVT that underwent evaluation at the Mayo Clinic, Rochester MN, USA (n=36), Catholic University, Rome, Italy, (n=23), and University of Florence, Italy (n=15) between 1991 and 2021 were included. The cohort from a previously published multi-center study that included 42 MPN cases with CVT, which were not included in the current study, was used for comparison of observations. Diagnosis of CVT was established with computed tomography or magnetic resonance imaging with venography. Results Patient characteristics at time of CVT Among 74 patients with CVT and MPN (median age 44 years, range 15-85; 61% females); disease-specific frequencies were 1.3% (39/2,893), 1.2% (21/1,811) and 0.2% (3/1,888) for essential thrombocythemia (ET), polycythemia vera (PV) and primary myelofibrosis (PMF), respectively. CVT occurred prior to (n=20, 27%, median time to MPN diagnosis 16.5 months), at (n=32, 44%) or after (n=21, 29%, median time to CVT 26 months) MPN diagnosis. 72% of patients presented with headaches, 22% visual changes, 12% nausea/vomiting, 8% neurological deficits, and 6% seizures. Transverse (51%), sagittal (43%) and sigmoid (35%) sinuses were involved with central nervous system hemorrhage in 10 (14%) patients. MPN phenotype included ET (n=39, 53%), PV (n=21, 28%), pre-fibrotic MF (n=6, 8%), MPN-unclassified (n=4, 5%), PMF (n=3, 4%) and post-PV MF (n=1, 1%). Driver mutation testing was performed in 65 patients: 91% harbored JAK2V617F, 3% CALR type 1, 2% MPL, 5% triple negative; moreover, JAK2V617F was mutated in 27/33 (82%) ET patients. An underlying thrombophilia was identified in 19 (31%) cases. No patient had thrombocytopenia. (Table 1). Notably, one patient received the Ad26.COV2.S vaccine, five days prior to presenting with CVT, not associated with thrombosis in other sites, thrombocytopenia or platelet factor 4 antibodies. A history of thrombosis was documented in 10 (14%) patients with three splanchnic venous events. These observations were similar to those noted in our comparative group from a previously published report that included 42 cases; (ET (n=25, 60%), PV (n=11, 26%), PMF (n=5, 12%); median age 51 years, range 16-84; 55% females; 81% JAK2V617F mutated). Prior thrombosis occurred in 8(19%) patients with four splanchnic venous events. Treatment for CVT included systemic anticoagulation alone in 27 (36%) patients or in conjunction with aspirin (n=24, 32%), cytoreductive therapy (n=14, 19%), or both aspirin and cytoreduction (n=9, 12%). 5/21 (24%) patients with CVT post MPN diagnosis, were on anticoagulation at the time of CVT. Outcome following CVT At a median follow-up of 5.1 years (range; 0.1-28.6), recurrent CVT was documented in 3 (4%) patients; incidence rates for other arterial and venous thromboses and hemorrhage were 11% (2 per 100 patient-years), 9% (1.9 per 100 patient-years) and 14% (3 per 100 patient-years), respectively. 3 of 7 (43%) venous thromboses were splanchnic events. Antithrombotic therapy was ongoing in 53% and 80% of patients with thrombotic recurrences and hemorrhage, respectively. A higher incidence of venous thrombosis was noted in the aforementioned previously published cohort (12 (29%) vs 7 (9%), p=0.01); with 5/12 (42%) splanchnic events. Incidence rates for arterial thrombosis and major hemorrhage were similar. Fibrotic and leukemic transformation occurred in 5 (8%) and 1(1%) patient, respectively, with five (7%) deaths unrelated to CVT. Conclusions The current study highlights close association of CVT with JAK2V617F, younger age, and female gender. Clinical features distinguishing COVID vaccine-related from MPN-associated CVT include lower likelihood of concomitant non-CVT venous thromboses with the latter; moreover, the absence of thrombocytopenia resulted in a lower rate of intracerebral hemorrhage in MPN cases; as a result, MPN-CVT was not fatal. Figure 1 Figure 1. Disclosures Vannucchi: AbbVie: Membership on an entity's Board of Directors or advisory committees; Incyte Corporation: Honoraria, Membership on an entity's Board of Directors or advisory committees; Bristol Myers Squibb: Honoraria, Membership on an entity's Board of Directors or advisory committees; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees.

AbstractThe recent association of cerebral venous thrombosis (CVT) with COVID‐19 vaccinations prompted the current retrospective review of 74 cases of CVT (median age = 44 years, range 15–85; 61% females) associated with myeloproliferative neoplasms (MPNs), seen at the Mayo Clinic, Catholic University of Rome, and University of Florence, between 1991 and 2021. Disease‐specific frequencies were 1.3% (39/2893), 1.2% (21/1811) and 0.2% (3/1888) for essential thrombocythemia, polycythemia vera and primary myelofibrosis, respectively. Cerebral venous thrombosis occurred either prior to (n = 20, 27%), at (n = 32, 44%) or after (n = 22) MPN diagnosis. A total of 72% of patients presented with headaches. Transverse (51%), sagittal (43%) and sigmoid sinuses (35%) were involved with central nervous system hemorrhage noted in 10 (14%) patients. In all, 91% of tested patients harbored JAK2V617F. An underlying thrombophilic condition was identified in 19 (31%) cases and history of thrombosis in 10 (14%). Treatment for CVT included systemic anticoagulation alone (n = 27) or in conjunction with aspirin (n = 24), cytoreductive therapy (n = 14), or both (n = 9). At a median follow‐up of 5.1 years (range 0.1–28.6), recurrent CVT was documented in three (4%) patients while recurrent arterial and venous thromboses and major hemorrhage were recorded in 11%, 9% and 14%, respectively. Follow‐up neurological assessment revealed headaches (n = 9), vision loss (n = 1) and cognitive impairment (n = 1). The current study lends clarity to MPN‐associated CVT and highlights its close association with JAK2V617F, younger age and female gender. Clinical features that distinguish COVID vaccine‐related CVT from MPN‐associated CVT include, in the latter, lower likelihood of concurrent venous thromboses and intracerebral hemorrhage; as a result, MPN‐associated CVT was not fatal.

Abstract The current retrospective study involving a total of 1607 patients was designed to identify clinical and molecular variables that were predictive of inferior myelofibrosis‐free survival (MFS) in WHO‐defined essential thrombocythemia (ET), utilizing three independent patient cohorts: University of Florence, Italy ( n = 718); Mayo Clinic, USA ( n = 479) and Policlinico Gemelli, Catholic University, Rome, Italy ( n = 410). The Florence patient cohort was first examined to identify independent risk factors for MFS, which included age > 60 years (HR 2.5, 95% CI 1.3–4.9), male sex (2.1, 1.2–3.9), palpable splenomegaly (2.1, 1.2–3.9), CALR 1/1‐like or MPL mutation (3.4, 1.9–6.1) and JAK2 V617F variant allele frequency > 35% (4.2, 1.6–10.8). Subsequently, an operational molecular risk category was developed and validated in the other two cohorts from Mayo Clinic and Rome: “high molecular risk” category included patients with JAK2 V617F VAF >35%, CALR type 1/1‐like or MPL mutations; all other driver mutation profiles were assigned to “low molecular risk” category. The former, compared to the latter molecular risk category, displayed significantly higher risk of fibrotic transformation: Florence cohort with respective fibrotic transformation risk rates of 8% vs. 1.2% at 10 years and 33% vs. 8% at 20 years ( p < 0.001; HR 6.1; 95% CI 3.2–11.7); Mayo Cohort, 16% vs. 7% at 10 years and 44% vs. 25% at 20 years ( p < 0.001; HR 2.5; 95% CI 1.6–4.1); and Rome cohort 7.8% vs. 4.6% at 10 years and 31.2% vs. 7.1% at 20 years ( p = 0.007, HR 2.7; 95% CI 1.3–5.8). The present study provides practically useful risk signals for fibrotic transformation in ET and facilitates identification of patients who require close monitoring and appropriate counseling.

SummaryFedratinib, an oral Janus kinase‐2 (JAK2) inhibitor, reduces splenomegaly and improves symptom burden in patients with myelofibrosis. Regulatory approval of fedratinib 400‐mg daily was based on results of an updated analysis of the pivotal phase III, placebo‐controlled JAKARTA trial in patients with JAK‐inhibitor‐naïve myelofibrosis. At week 24, spleen volume response rate was 47% and symptom response rate was 40% with fedratinib 400 mg, versus 1% and 9% respectively, with placebo. Common adverse events were diarrhoea, nausea, anaemia, and vomiting. No Wernicke encephalopathy occurred in patients receiving fedratinib 400 mg/day. These updated data support use of first‐line fedratinib in patients with myelofibrosis.