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Essential thrombocythemia (ET) is characterized by abnormal megakaryopoiesis and enhanced thrombotic risk. Once-daily low-dose aspirin is the recommended antithrombotic regimen, but accelerated platelet generation may reduce the duration of platelet cyclooxygenase-1 (COX-1) inhibition. We performed a multicenter double-blind trial to investigate the efficacy of 3 aspirin regimens in optimizing platelet COX-1 inhibition while preserving COX-2–dependent vascular thromboresistance. Patients on chronic once-daily low-dose aspirin (n = 245) were randomized (1:1:1) to receive 100 mg of aspirin 1, 2, or 3 times daily for 2 weeks. Serum thromboxane B2 (sTXB2), a validated biomarker of platelet COX-1 activity, and urinary prostacyclin metabolite (PGIM) excretion were measured at randomization and after 2 weeks, as primary surrogate end points of efficacy and safety, respectively. Urinary TX metabolite (TXM) excretion, gastrointestinal tolerance, and ET-related symptoms were also investigated. Evaluable patients assigned to the twice-daily and thrice-daily regimens showed substantially reduced interindividual variability and lower median (interquartile range) values for sTXB2 (ng/mL) compared with the once-daily arm: 4 (2.1-6.7; n = 79), 2.5 (1.4-5.65, n = 79), and 19.3 (9.7-40; n = 85), respectively. Urinary PGIM was comparable in the 3 arms. Urinary TXM was reduced by 35% in both experimental arms. Patients in the thrice-daily arm reported a higher abdominal discomfort score. In conclusion, the currently recommended aspirin regimen of 75 to 100 once daily for cardiovascular prophylaxis appears to be largely inadequate in reducing platelet activation in the vast majority of patients with ET. The antiplatelet response to low-dose aspirin can be markedly improved by shortening the dosing interval to 12 hours, with no improvement with further reductions (EudraCT 2016-002885-30).

The goal of therapy for essential thrombocythemia (ET) and polycythemia vera (PV) patients is to reduce thrombotic events by normalizing blood counts. Hydroxyurea (HU) and interferon-α (IFN-α) are the most frequently used cytoreductive options for ET and PV patients at high-risk for vascular complications. Myeloproliferative Disorders Research Consortium 112 was an investigator-initiated, phase 3 trial comparing HU to pegylated IFN-α (PEG) in treatment naïve, high-risk ET/PV patients. The primary endpoint was complete response (CR) rate at 12 months. A total of 168 patients were treated for a median of 81.0 weeks. CR for HU was 37% and 35% for PEG (p=0.80) at 12 months. At 24/36 months, CR was 20%/17% for HU and 29%/33% for PEG. PEG led to a greater reduction in JAK2V617F at 24 months, but histopathologic responses were more frequent with HU. Thrombotic events and disease progression were infrequent in both arms, while grade 3/4 adverse events were more frequent with PEG (46% vs. 28%). At 12 months of treatment there was no significant difference in CR rates between HU and PEG. This study indicates that PEG and HU are both effective treatments for PV and ET. With longer treatment PEG was more effective in normalizing blood counts and reducing driver mutation burden, while HU produced more histopathologic responses. Despite these differences, both agents did not differ in limiting thrombotic events and disease progression in high-risk ET/PV patients. (Funded by the National Cancer Institute, 5P01CA108671-09; clinicaltrials.gov number (NCT01259856). [Abstract copyright: Copyright © 2022 American Society of Hematology.]

Introduction. MPN-COVID is a European LeukemiaNet cohort study, launched in March 2020 in patients with myeloproliferative neoplasms (MPN) with COVID-19. The first cohort of 175 cases was analyzed at the end of first wave (July 2020) and results provided estimates and risk factors of overall mortality (Barbui T. Leukemia, 2021), thrombosis incidence (Barbui T. Blood Cancer J, 2021), and post-COVID outcomes (Barbui T. Blood Cancer J, 2021). In the second wave of pandemic (June 2020 to June 2021), case-fatality risk in the general population has been found variable across different countries, and no information is available in MPN patients with COVID-19 diagnosed during the second wave in comparison with those of the first wave. Methods. In an electronic case report form, we registered a total of 479 cases of ET (n=161, 34%), PV (n=135, 28%), pre-PMF (n=49, 10%) and overt MF (n=134, 28%), from 39 European hematology units (Italy, Spain, Germany, France, UK, Poland, Croatia). Of these, 304 were diagnosed COVID-19 during the second wave. Results. Patients in the second wave were significantly different from those in the first wave, including parameters such as age (median: 63 vs. 71 years, p Conclusions. This is the largest series of MPN patients who incurred COVID-19 from June 2020 onward, namely during the "second COVID-19 wave". Compared to the first wave, the second one recorded a lower overall COVID-19 severity, but Ruxolitinib discontinuation still remained a risk factor for a dismal outcome. Greater vulnerability of ET than PV in developing venous thrombosis was confirmed also during the second wave. This finding suggests that ET warrants a specific antithrombotic prophylaxis in addition to heparin. Figure 1 Figure 1. Disclosures 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. Iurlo: Novartis: Speakers Bureau; Incyte: Speakers Bureau; Pfizer: Speakers Bureau; Bristol Myers Squibb: Speakers Bureau. Sobas: Celgene: Consultancy, Honoraria; Novartis: Consultancy, Honoraria. Fox: Novartis: Honoraria; Sierra: Honoraria. Palandri: AOP: Membership on an entity's Board of Directors or advisory committees; CTI: Consultancy; Sierra Oncology: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees. Benevolo: Novartis: 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; Takeda: Membership on an entity's Board of Directors or advisory committees; BMS: Membership on an entity's Board of Directors or advisory committees; Amgen: Speakers Bureau. Harrison: Gilead Sciences: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Roche: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Sierra Oncology: Honoraria; 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; 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; Shire: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Incyte Corporation: 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; Janssen: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Novartis: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Geron: 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; Constellation Pharmaceuticals: Research Funding; Abbvie: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Bonifacio: Pfizer: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees; Bristol Myers Squibb: Membership on an entity's Board of Directors or advisory committees; Amgen: Membership on an entity's Board of Directors or advisory committees. Kiladjian: Taiho Oncology, Inc.: Research Funding; Bristol Myers Squibb: Membership on an entity's Board of Directors or advisory committees; Incyte Corporation: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees; PharmaEssentia: Other: Personal fees; AOP Orphan: Membership on an entity's Board of Directors or advisory committees; AbbVie: Membership on an entity's Board of Directors or advisory committees. Patriarca: Incyte: Honoraria; Takeda: Honoraria; Argenix: Honoraria; Novartis: Honoraria; Amgen: Honoraria; Pfizer: Honoraria. Griesshammer: Janssen: Consultancy, Honoraria; Roche: Consultancy, Honoraria; Shire: Consultancy, Honoraria; Pfizer: Consultancy, Honoraria; Celgene: Consultancy, Honoraria; Novartis: Consultancy, Honoraria; Amgen: Consultancy, Honoraria; AOP Orphan: Consultancy, Honoraria; CTI: Consultancy, Honoraria; Gilead: Consultancy, Honoraria; Astra Zeneca: Consultancy, Honoraria. Garcia Gutierrez: Pfizer: Consultancy, Honoraria, Research Funding; Incyte: Consultancy, Honoraria, Research Funding; BMS: Consultancy, Honoraria, Research Funding; Novartis: Consultancy, Honoraria, Research Funding. Osorio: Janssen, Abbvie, Roche: Consultancy. Koschmieder: CTI: Membership on an entity's Board of Directors or advisory committees, Other; BMS: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: (e.g. travel support); Bristol-Myers Squibb: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel support, Research Funding; Baxalta: Membership on an entity's Board of Directors or advisory committees, Other; Abbvie: Other: Travel support; Alexion: Other: Travel support; Karthos: Other: Travel support; Sanofi: Membership on an entity's Board of Directors or advisory committees, Other: Travel support; Image Biosciences: Other: Travel support; AOP Pharma: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: (e.g. travel support), Research Funding; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: (e.g. travel support); Incyte: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: (e.g. travel support); Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: (e.g. travel support), Research Funding; Geron: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: (e.g. travel support), Research Funding; Roche: 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, Other: Travel support, Research Funding; Ariad: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: (e.g. travel support); Pfizer: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: (e.g. travel support); Shire: Honoraria, Other. 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.

Introduction: Anticoagulation plays a crucial role in the treatment of splanchnic vein thrombosis (SVT), including thrombosis of the portal (PVT), mesenteric (MVT) and splenic (SpVT) veins. Rivaroxaban is a potential alternative to heparins and vitamin K antagonists (VKA) in these patients, but data to support its use are scant. Several recent guidelines highlighted the limited evidence available for the use of the direct oral anticoagulants in these patients. In addition, despite anticoagulation, SVT patients carry high risk of recurrent venous thromboembolic events. The aim of this study was to evaluate the safety and efficacy of rivaroxaban for the acute-phase treatment of SVT (first 3 months of treatment). Methods: RIVASVT-100 (NCT02627053) was a prospective cohort study of adult patients with a first episode of symptomatic, objectively diagnosed PVT, MVT or SpVT. Exclusion criteria were known liver cirrhosis, Budd-Chiari syndrome, previous or ongoing variceal bleeding, portal cavernoma, thrombocytopenia, severe renal failure, life expectancy 7 days, ongoing VKA treatment. Patients received rivaroxaban 15 mg twice daily for 3 weeks, followed by 20 mg once daily for a total of 3 months. Afterwards, the decision to continue any available anticoagulant drug was left to the discretion of the attending physicians. Follow-up was performed at 3 weeks, 2 months, 3 months and 6 months. Primary outcome was the occurrence of ISTH-defined major bleeding events during the 3 months of active treatment and up to 2 days after the end of study treatment. Secondary outcomes included death, clinically relevant non-major bleeding (CRNMB), recurrent SVT or symptomatic venous thromboembolism in other sites. We here report the results of the 3-month follow-up. Results: Between June 2015 and March 2021, 103 patients were enrolled from 18 participating centres. After excluding 3 patients who did not meet the criteria for eligibility, 100 patients were included in the analysis. Mean (SD) age was 54.4 (± 15.5) years; 64% were males. Overall, 74% of patients had PVT, 61% MVT and 48% SpVT; 53% of SVT occurred in multiple sites. The most common risk factors were abdominal inflammation/infection (26%), followed by solid cancer (9%), overt myeloproliferative neoplasms (9%) and oestrogen hormonal therapy (9%), while 43% of cases were unprovoked. The JAK2 V617F mutation was detected in 13 out of 50 tested patients (26%). Rivaroxaban was the sole anticoagulant agent used in 21% of patients, whereas the remaining received a combination of anticoagulants, which included low molecular weight heparin, unfractionated heparin or fondaparinux for a median of 5.0 days before transitioning to rivaroxaban. Three patients were lost to follow-up but known to be alive at the end of the study. At 3-month follow-up, 1 (1.0%) patient died due to a non-SVT related cause. Two patients (2.06%; 95% CI, 0.57-7.21) had major bleeding events (both gastrointestinal), while 3 patients (3.09%) had CRNMB. There were 2 recurrent SVT (2.06%) during rivaroxaban treatment, one of these occurred in a patient with metastatic solid cancer. The 6-month follow-up for the last enrolled patient is ongoing. Conclusions: Rivaroxaban appears to be safe and effective for the acute-phase treatment of SVT in non-cirrhotic patients. Disclosures Beyer-Westendorf: Bayer: Other: Personal fees; Daiichi Sankyo: Other: Personal fees; Pfizer: Other: Personal fees; Portola-Alexion: Other: Personal fees. Carrier: BMS: Honoraria, Research Funding; Leo Pharma: Honoraria, Research Funding; Bayer: Honoraria; Pfizer: Honoraria, Research Funding; Servier: Honoraria; Sanofi: Honoraria. Bertoletti: BMS: Honoraria, Other: Personal Fees; Pfizer: Honoraria, Other: Personal fees; Aspen: Other: Personal Fees; Bayer: Other: Personal Fees; Leo Pharma: Other: Personal Fee. Di Nisio: Bayer, Daiichi Sankyo, BMS-Pfizer, Leo Pharma, and Sanofi: Other: Personal fees. Ageno: Bayer: Research Funding; Bayer, Portola, Janssen, Aspen, Norgine, Sanofi.: Other: Advisory Board. OffLabel Disclosure: The use of rivaroxaban in splanchnic vein thrombosis is off label in most countries.

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 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.

Background The detrimental effect of leukocytosis on survival in myeloproliferative neoplasms (MPN) has been well established for primary myelofibrosis (PMF), polycythemia vera (PV) and essential thrombocythemia (ET ) (JCO. 2018;36:310; BJH. 2020;189:291) Previous studies have also implicated leukocytosis as a risk factor for leukemic transformation (Mayo Clin Proc. 2017;92:1118) and thrombosis in MPN (Blood Adv. 2019;3:1729). However, it is currently not clear as to which component(s) of white blood cells is responsible for these observations. In the current study, we sought to examine the individual prognostic contribution of absolute neutrophil (ANC), lymphocyte (ALC) and monocyte (AMC) counts, on overall (OS), leukemia-free (LFS), and myelofibrosis-free (MFFS) survival and in ET. Methods Study patients (n=349) were retrospectively recruited from the Mayo Clinic MPN database of 1,249 WHO-defined ET patients, evaluated over five decades (1967-2021), based on availability of information on ANC, ALC and AMC. Conventional criteria were used for diagnosis and definitions of major complications, including leukemic or fibrotic transformation (Blood 2016;127:2391). Conventional statistical methods were applied using JMP Pro 14.0.0 software package, SAS Institute, Cary, NC. Multivariable analyses included previously established risk factors for survival. Results 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%); median followup was 10 years (range 0-47), during which time 118 deaths, 52 fibrotic progressions, and 14 leukemic transformations were documented. Multivariable analysis identified older age (p60 years, 3.1 (2.1-4.6; p60 years), 2 for increased ANC (≥8 x 10(9)/L) and 1 for ALC ( An external validation cohort from the University of Florence (n=485) confirmed the independent survival risk contribution from age >60 years (p Conclusions: The current study identifies increased ANC and decreased ALC as age-independent risk factors for survival in ET, thus allowing the development of a globally applicable simple to use "Triple A" risk model that is based on Age, ANC and ALC. Decreased ALC also predicted fibrotic and leukemic progression. Our observations suggest potential value for immune profiling as an additional prognostic tool in MPN. Figure 1 Figure 1. Disclosures Szuber: Novartis: Honoraria. Vannucchi: BMS: 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: Honoraria, Membership on an entity's Board of Directors or advisory committees; AbbVie: Membership on an entity's Board of Directors or advisory committees.

Background and Rationale. miRNAs are small non-coding RNAs that regulate gene expression by acting on the epigenetic machinery and are themselves controlled by epigenetic mechanisms. The expression of miRNAs is linked to cancer development and miRNA profiles are studied as new prognostic factors or therapeutic new perspectives (Jiang X et al. Nat Commun 2016). High-risk MDS are now treated with hypomethylating agents, like Azacitidine (AZA), alone or in combination with other drugs, such as Lenalidomide (LEN). Recent data showed that the concurrent acquisition of specific point mutations on PI3KCD, PLCG2 and AKT3 genes is associated with loss of response to AZA+LEN therapy (Follo MY et al. Leukemia 2019). Inositide signalling regulated by Phospholipase C (PLC) and PI3K/AKT is indeed involved in epigenetic processes and in MDS progression to AML, through the regulation of proliferation, differentiation and apoptosis. Patients and Methods. This study included 26 high-risk MDS patients treated with AZA (75 mg/m2/day, days 1-5, sc) and LEN (10 mg/day, days 1-21 or 8-21, orally) every 4 weeks. Patients showing complete remission (CR), partial remission (PR), any hematologic improvement (HI) or marrow CR+HI following IWG response criteria were considered as responders, while patients showing stable disease or disease progression were considered as non-responders. miRNAs expression was assessed using an Affymetrix miRNA 4.0 array on patients' cells extracted at baseline and during the therapy, at the 4th (T4) and 8th (T8) cycle of therapy. Results were then validated by Real-Time PCR and miRNA targets were studied by dual Luciferase assay. Real-Time PCR was also used to examine the expression of PLC genes. Results. All patients included in this study were considered evaluable for response. According to the revised IWG criteria (14), the overall response rate (ORR) was 76.9% (20/26 cases): CR (5/26, 19.2%), PR (1/26, 3.8%), marrow CR (mCR, 2/26, 7.7%), HI (6/26, 23.1%), mCR+HI (6/26, 23.1%), whereas 6/26 patients (23.1%) had a stable disease. For our analyses, we considered 10 patients as responders (R, showing response within T4 and maintaining it at T8), 10 losing response (LR, showing response within T4 and losing it at T8) and 6 non-responders (NR, never showing a response). Paired analysis between R and NR patients showed a statistically significant up-regulation of miR-192-5p and miR-21-5p between T0 and T4, as well as a down-regulation of miR-224-5p between T4 and T8, hinting at a relevant role for these miRNAs during AZA+LEN response. Real-Time PCR analyses confirmed the modulation of miR-192-5p and an altered expression of PLC genes during AZA+LEN therapy in all patients' subgroups, as well as an involvement of BCL-2 (possible target of miR-192-5p) that was also proven in vitro by dual Luciferase assays. Furthermore, as miR-192-5p expression seemed to be correlated with response, we performed Kaplan-Meier analyses and found out an association between high levels of miR-192-5p at T4 and OS (p=0.08) or LFS (p=0.04) in our MDS cases. More interestingly, this correlation was stronger (p=0.03) in R, as compared with LR and NR. Conclusions. This study shows that AZA+LEN therapy in MDS affects the expression of miR-192-5p, whose high level at T4 is associated with higher OS and LFS in responder patients. Moreover, we showed that miR-192-5p specifically targets and inhibits BCL-2, hinting at a regulation of MDS proliferation and apoptosis. Additional studies, to be performed in a larger cohort of MDS patients, are needed to confirm these data, as well as better understand the molecular mechanisms and the prognostic relevance of miR-192-5p in AZA+LEN therapy. Disclosures Cavo: AbbVie: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Adaptive Biotechnologies: Consultancy, Honoraria; Novartis: Honoraria; GlaxoSmithKline: Consultancy, Honoraria; Takeda: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Amgen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: TRAVEL, ACCOMMODATIONS, EXPENSES, Speakers Bureau; Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel Accommodations, Speakers Bureau; Sanofi: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Bristol-Myers Squib: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Finelli: Celgene BMS: Consultancy, Research Funding, Speakers Bureau; Takeda: Consultancy; Novartis: Consultancy, Speakers Bureau.

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 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.

Background: Ciltacabtagene autoleucel (cilta-cel) is a novel chimeric antigen receptor T-cell therapy that is being evaluated in the CARTITUDE-1 trial (NCT03548207) in patients with relapsed or refractory multiple myeloma (RRMM) who are triple-class exposed (to immunomodulatory drugs, proteasome inhibitors, and an anti-CD38 monoclonal antibody). As there is no clear standard of care for this patient population, and due to an absence of direct head-to-head trials evaluating cilta-cel and other relevant treatments, indirect treatment comparisons (ITCs) between cilta-cel and treatments used in current clinical practice, ie, physician's choice of treatment (PCT), have been previously conducted. Meta-analyses were performed to derive single summary effect estimates for overall survival (OS) and progression-free survival (PFS) by pooling ITCs evaluating cilta-cel versus PCT in patients with triple-class exposed RRMM. Methods: ITCs examining the comparative effectiveness of cilta-cel versus PCT on OS and PFS were included. Data on cilta-cel corresponded to the February 2021 data-cut for CARTITUDE-1. Data on PCT was leveraged from the following sources: (i) the Flatiron database, a primarily US community-based multiple myeloma registry, (ii) the long-term follow-up results of three global RRMM daratumumab randomized clinical trials (POLLUX [NCT02076009], CASTOR [NCT02136134], and EQUULEUS [NCT01998971]), (iii) the US-based retrospective MAMMOTH study, and (iv) a representative German patient registry maintained by OncologyInformationService (OIs). In each ITC, the PCT group was comprised of patients who satisfied key eligibility criteria for CARTITUDE-1 and was made comparable to CARTITUDE-1 using inverse probability of treatment weighting. Hence, the ITCs were deemed appropriate to meta-analyze. The meta-analyses used a robust variance estimator to account for the use of CARTITUDE-1 in each pairwise ITC. The main meta-analyses considered all participants treated with cilta-cel in CARTITUDE-1 compared with PCT. Sensitivity analyses considered ITC effect estimates based on all enrolled participants in CARTITUDE-1. Pooled summary effect estimates were presented as hazard ratios (HRs) with the corresponding 95% confidence intervals (CIs). Results: Based on availability of data, the main meta-analyses included four ITCs for OS and three ITCs for PFS. Cilta-cel was associated with a statistically significant improvement in OS (HR: 0.21, 95% CI: 0.13 to 0.34; Figure 1) and PFS (HR: 0.20, 95% CI: 0.07 to 0.63; Figure 2) compared to PCT. Sensitivity analyses including all enrolled participants confirmed the results of the main meta-analyses. Conclusions: In the meta-analyses, cilta-cel demonstrated a significant advantage over PCT in terms of OS and PFS, highlighting its potential as an effective therapy in patients with triple-class exposed RRMM. Figure 1 Figure 1. Disclosures Hari: GSK: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other, Research Funding, Speakers Bureau; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other, Research Funding, Speakers Bureau; Celgene-BMS: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other, Research Funding, Speakers Bureau; Amgen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other, Research Funding, Speakers Bureau; Karyopharm: Consultancy; Sanofi: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Oncopeptides: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Takeda: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other, Research Funding, Speakers Bureau; Adaptive Biotech: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Millenium: Membership on an entity's Board of Directors or advisory committees, Research Funding. Berdeja: EMD Sorono, Genentech: Research Funding; Celularity, CRISPR Therapeutics: Research Funding; Bluebird bio, BMS, Celgene, CRISPR Therapeutics, Janssen, Kite Pharma, Legend Biotech, SecuraBio, Takeda: Consultancy; Abbvie, Acetylon, Amgen: Research Funding; GSK, Ichnos Sciences, Incyte: Research Funding; Lilly, Novartis: Research Funding; Poseida, Sanofi, Teva: Research Funding. Gay: Bluebird Bio: Membership on an entity's Board of Directors or advisory committees; Oncopeptides: Membership on an entity's Board of Directors or advisory committees; Adaptive Biotechnologies: Membership on an entity's Board of Directors or advisory committees; Roche: Membership on an entity's Board of Directors or advisory committees; GlaxoSmithKline: Honoraria, Membership on an entity's Board of Directors or advisory committees; AbbVie: Honoraria, Membership on an entity's Board of Directors or advisory committees; Bristol-Myers Squibb: Honoraria; Takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees; Amgen: Honoraria, Membership on an entity's Board of Directors or advisory committees; Sanofi: Consultancy, Honoraria. Hooper: Eversana: Current Employment; Janssen: Consultancy. Haltner: Eversana: Current Employment; Janssen: Consultancy. Kumar: Carsgen: Research Funding; Novartis: Research Funding; Merck: Research Funding; Bluebird Bio: Consultancy; Roche-Genentech: Consultancy, Research Funding; Oncopeptides: Consultancy; Astra-Zeneca: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Antengene: Consultancy, Honoraria; Janssen: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Beigene: Consultancy; KITE: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Takeda: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Tenebio: Research Funding; Celgene: Membership on an entity's Board of Directors or advisory committees, Research Funding; Adaptive: Membership on an entity's Board of Directors or advisory committees, Research Funding; Amgen: Consultancy, Research Funding; Abbvie: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; BMS: Consultancy, Research Funding; Sanofi: Research Funding. Martin: Sanofi: Research Funding; Janssen: Research Funding; GlaxoSmithKline: Consultancy; Amgen: Research Funding; Oncopeptides: Consultancy. Mateos: AbbVie: Honoraria; Oncopeptides: Honoraria, Membership on an entity's Board of Directors or advisory committees; Regeneron: Honoraria, Membership on an entity's Board of Directors or advisory committees; Amgen: Honoraria, Membership on an entity's Board of Directors or advisory committees; Takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees; Celgene - Bristol Myers Squibb: Honoraria, Membership on an entity's Board of Directors or advisory committees; Roche: Honoraria, Membership on an entity's Board of Directors or advisory committees; Bluebird bio: Honoraria; Pfizer: Honoraria, Membership on an entity's Board of Directors or advisory committees; Oncopeptides: Honoraria; Adaptive Biotechnologies: Honoraria, Membership on an entity's Board of Directors or advisory committees; Sea-Gen: Honoraria, Membership on an entity's Board of Directors or advisory committees; GSK: Honoraria; Sanofi: Honoraria, Membership on an entity's Board of Directors or advisory committees; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees. Moreau: Sanofi: Honoraria; Janssen: Honoraria; Celgene BMS: Honoraria; Oncopeptides: Honoraria; Amgen: Honoraria; Abbvie: Honoraria. Rosta: EVERSANA: Current Employment; Janssen Inc.: Consultancy. Samjoo: EVERSANA: Current Employment; Janssen Inc.: Consultancy. Usmani: GSK: Consultancy, Research Funding; Abbvie: Consultancy; Array BioPharma: Consultancy, Research Funding; Celgene/BMS: Consultancy, Research Funding, Speakers Bureau; EdoPharma: Consultancy; Seattle Genetics: Consultancy, Research Funding; Janssen Oncology: Consultancy, Research Funding; SkylineDX: Consultancy, Research Funding; Takeda: Consultancy, Research Funding, Speakers Bureau; Janssen: Consultancy, Research Funding, Speakers Bureau; Merck: Consultancy, Research Funding; Sanofi: Consultancy, Research Funding, Speakers Bureau; Pharmacyclics: Consultancy, Research Funding; Bristol-Myers Squibb: Research Funding; Amgen: Consultancy, Research Funding, Speakers Bureau. Weisel: Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Amgen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; GSK: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Karyopharm: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Bristol Myers Squibb: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Takeda: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Roche: Honoraria; Oncopeptides: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Adaptive Biotechnologies: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Sanofi: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Abbvie: Consultancy; Novartis: Honoraria; Pfizer: Honoraria. Jackson: Janssen: Current Employment; Memorial Sloan Kettering Cancer Center: Consultancy. Olyslager: Janssen: Current Employment. Schecter: Janssen: Current Employment, Current holder of stock options in a privately-held company. Vogel: Janssen Global Services, LLC: Current Employment, Current holder of individual stocks in a privately-held company, Current holder of stock options in a privately-held company, Divested equity in a private or publicly-traded company in the past 24 months. Garrett: Legend Biotech USA: Current Employment. Lee: Legend Biotech: Current Employment, Current equity holder in publicly-traded company. Nesheiwat: Legend Biotech USA: Current Employment. Pacaud: Legend Biotech: Current Employment. Valluri: Janssen: Current Employment, Current equity holder in publicly-traded company. Costa: Amgen: Consultancy, Honoraria, Research Funding, Speakers Bureau; Sanofi: Consultancy, Honoraria, Speakers Bureau; BMS: Consultancy, Honoraria, Research Funding; Karyopharm: Consultancy, Honoraria; Janssen: Consultancy, Honoraria, Research Funding; Pfizer: Consultancy, Honoraria. Lin: Merck: Research Funding; Bluebird Bio: Consultancy, Research Funding; Juno: Consultancy; Takeda: Research Funding; Legend: Consultancy; Sorrento: Consultancy; Gamida Cell: Consultancy; Vineti: Consultancy; Novartis: Consultancy; Celgene: Consultancy, Research Funding; Janssen: Consultancy, Research Funding; Kite, a Gilead Company: Consultancy, Research Funding.