Abstract: Background Hospitalised patients with severe COVID-19 (requiring critical care level support) appear to be at increased risk of thrombosis despite standard pharmacological thromboprophylaxis. The magnitude of thrombotic risk in patients with COVID-19 of moderate severity (not requiring critical care) is less clear. The optimal approach to thromboprophylaxis (and the role of intensified thromboprophylaxis) remains to be determined. Evidence of endothelial dysfunction has been widely reported in COVID-19 (particularly in severe COVID) and this may contribute to hypercoagulability. Aim To assess differences in patterns of hypercoagulability and endothelial dysfunction between a group of patients with moderate COVID-19 and a group of age-matched hospitalized patients (SARS-CoV-2 PCR negative) receiving low molecular weight heparin (LMWH) thromboprophylaxis. Methods Blood was collected from individuals admitted to hospital with COVID-19 of moderate severity (not requiring critical care level support) and a group of age-matched patients admitted with infective/inflammatory illness (SARS-CoV-2 PCR negative). All subjects received standard-dose LMWH thromboprophylaxis, with blood drawn at 12 hours post-dose (and with measurement of anti-FXa activity levels). Circulating levels of endothelial & fibrinolytic markers including ICAM, PAI-1, VCAM, soluble thrombomodulin (sTM), and tissue plasminogen activator (tPA) were determined by ELISA. Thrombin generation (TG) in platelet-poor plasma was assessed by calibrated automated thrombography in the presence of tissue factor (Final concentration, 1pM & 5pM), thrombomodulin (TM) (Final concentration, 6.25nM), and an inhibitory anti-tissue factor pathway inhibitor antibody (anti-TFPI; Final concentration 100μg/mL). Results 14 COVID-19 positive subjects and 11 hospitalized controls were recruited. There were no differences in mean age (69.7±4.5 vs 61.6±4.7 years; p= 0.2) or mean Body mass index (25.7±1.1 vs 22.7±1.2 Kg/m2; p=0.1) between groups. No COVID-19 patient or control required critical care support. In the COVID group, radiological evidence of pneumonitis [diffuse (n=3) or peripheral infiltrates (n=7)] was present in the majority of cases. None of the COVID-19 cases were requiring supplemental oxygen at the time of recruitment. All controls were admitted with either respiratory or urinary infection [radiological evidence of pneumonia in 4/11; supplemental oxygen requirement in 2/11, (28-36% FiO2 via nasal cannula)]. Plasma levels of sTM, ICAM, PAI-1 & VCAM were similar in both groups. Levels of t-PA were significantly higher in the COVID group (8.31±4.35 vs 4.91±2.37 ng/mL; p= 0.005). Despite similar plasma anti-Xa activity in both groups (0.06 vs 0.04 IU/mL; p=0.2), mean endogenous thrombin potential (ETP) was significantly higher in the COVID group (1929±119.7 vs 1528±138.9 nM*min; p=0.02), although peak thrombin was similar (173.6±26 vs 161.5±31nM). ETP-TM ratio was similar between groups (0.3±0.1 vs 0.2±0.1; p=0.3). Despite increased ETP, the lag time to thrombin generation was significantly prolonged in the COVID group (8.3±0.6 vs 5.8±0.5 mins, p= 0.006). This pattern has previously been observed in vascular diseases associated with altered plasma tissue factor pathway inhibitor (TFPI) activity. In the presence of an anti-TFPI antibody, the difference in lagtime between groups was attenuated (4.7±0.2 vs 3.5±0.1 mins; p= 0.002) and the difference in overall thrombin generation (delta TG) between both groups became significantly increased (Fig.1). Conclusion Plasma thrombin generation is enhanced in patients with non-severe COVID-19 despite pharmacological thromboprophylaxis. Endothelial dysfunction is also observed in this group and appears to modulate parameters of plasma thrombin generation. The clinical implications of these observations are not known although clinical studies of intensified thromboprophylaxis in attenuating thrombotic risk and other complications are ongoing. Fig 1. Inhibition of TFPI activity enhances thrombin generation in COVID-19. In the presence of an inhibitory anti-TFPI antibody, peak plasma thrombin generation was enhanced in COVID-19 in contrast to that observed among SARS-CoV-2 PCR negative hospitalised patients (339.6+25.2 vs 247.4+10.1, p=0.01). Figure 1 Figure 1. Disclosures Maguire: Actelion: Research Funding; Bayer Pharma: Research Funding. Ni Ainle: Daiichi-Sankyo: Research Funding; Actelion: Research Funding; Leo Pharma: Research Funding; Bayer Pharma: Research Funding. Kevane: Leo Pharma: Research Funding.

Abstract: The risk of thrombosis differs between men and women; however, the mechanisms underlying this sex difference are unknown. We recently reported differences in thrombosis that are dependent on sexually-dimorphic patterns of growth hormone (GH) secretion and its subsequent effects on the expression of coagulation-related genes in the liver. Mice that are deficient in STAT5A and STAT5B are largely insensitive to growth hormone and demonstrate loss or reversal of sex-specific patterns of liver gene expression. Thus, genetic manipulation of STAT5 factors provides a means of probing the mechanism of GH-dependent sex differences in thrombosis. We analyzed mice with global (STAT5g) and liver-specific (STAT5c) disruptions of the Stat5a and Stat5b genes, and determined their susceptibility to thrombosis in vivo and coagulation in vitro. In an in vivo model of pulmonary embolism, control female mice were relatively protected from thrombosis compared to control males, demonstrating percent survival of 61.3% and 50.0% and median survival times of 1200 and 972 seconds, respectively. In contrast, STAT5g males and females showed similar susceptibility to pulmonary embolism and had significantly reduced survival compared to matched controls, with percentages of 12.5% and 11.1% and median survival times of 468 and 275 seconds, respectively. As with the global loss of STAT5AB, liver-specific disruption of STAT5AB resulted in reduced survival compared to control mice. In vitro coagulation studies of whole blood triggered with dilute tissue factor (TF 1:1000) revealed significantly longer clot times in control females compared to control males. In contrast, mice with either global or liver-specific disruption of STAT5AB showed similar whole blood clot times between males and females, but had significantly shorter clot times as compared to controls. Similar results were obtained from coagulation studies in platelet poor plasma, indicating that platelets or white blood cells do not play a major role in this phenotype. No significant differences were found between control and STAT5AB-deficient mice in the expression or activity of a panel of pro- or anti-coagulant factors. APC sensitivity ratios were also similar between control and STAT5g males and females. An in vitro clotting model was employed to measure thrombin-antithrombin (TAT) complexes, fibrinogen, and D-dimer levels over time. Clotting was triggered with a 1:10,000 dilution of TF and analyzed at two minute intervals for ten minutes. Levels of TAT and fibrinogen did not differ between genotypes throughout the time course. In contrast, D-dimer was decreased in STAT5AB-deficient mice at each interval with a 52% reduction present at four minutes and a 46% reduction remaining at ten minutes. These studies have shown that global and liver-specific loss of STAT5AB results in reduced survival in a pulmonary embolism model, in vivo and shorter clotting times, in vitro. Furthermore, STAT5AB -deficiency eliminated the relative protection from thrombosis afforded to control female mice. This observed increase in thrombosis was not due to significant changes in coagulation factor activity, APC resistance, fibrinogen levels, or thrombin generation. However, a major decrease in D-dimer levels suggests a defect in the fibrinolytic system. While future studies are aimed at further defining the mechanistic regulation of the fibrinolytic system by growth hormone and downstream mediators, the current findings demonstrate a novel role for STAT5AB as a significant regulator of sexdependent thrombosis.

Abstract: Thromboembolic events are frequent and life-threating complications of COVID-19 but are also observed in patients with sepsis. Disseminated thrombosis can occur despite anticoagulation, suggesting that platelets play a direct but incompletely understood role. Several studies demonstrated altered platelet function in COVID-19 with some controversial findings, while underlying disease-specific mechanisms remain ill defined. We performed a comprehensive cohort study with 111 patients, comprising 37 with COVID-19, 46 with sepsis, and 28 with infection, compared with control participants. Platelet phenotype and function were assessed under static and flow conditions, revealing unexpected disease-specific differences. From hospital admission onward, platelets in COVID-19 failed to activate the integrin glycoprotein IIb/IIa (GPIIb/IIIa) in response to multiple agonists. Dense granule release was markedly impaired due to virtually missing granules, also demonstrated by whole-mount electron microscopy. By contrast, α-granule marker CD62P exposure was only mildly affected, revealing a subpopulation of PAC-1−/CD62P+ platelets, independently confirmed by automated clustering. This uncoupling of α-granule release was not observed in patients with sepsis, despite a similar disease severity. We found overall unaltered thrombus formation in COVID-19 and sepsis samples under venous shear rates, which was dependent on the presence of tissue factor. Unexpectedly, under arterial shear rates, thrombus formation was virtually abrogated in sepsis, whereas we detected overall normal-sized and stable thrombi in blood from patients with COVID-19. These thrombi were susceptible to subthreshold levels of GPIIb/IIIa blockers, eptifibatide, or tirofiban that had only a minor effect in control participants’ blood. We provide evidence that low-dose GPIIb/IIIa blockade could be a therapeutic approach in COVID-19.

Abstract: While acute myeloid leukemia (AML) is still associated with a low cure rate, recent advances in understanding its molecular complexity have significantly improved therapy for subgroups of patients, including those harboring FLT3, IDH1 or IDH2 mutations1. However, more than half of AML cases still lack a druggable oncogenic target. Human cancers frequently harbor mutations in RAS oncogene family members, including NRAS, KRAS and HRAS, which drive oncogenesis by augmenting cellular proliferation and survival. These are small protein GTPases, regulated by a switch between active GTP-linked and inactive GDP-bound states governed by a complex network of guanine exchange factors (GEFs, favoring RAS-GTP) and GTPase activating factors (GAPs, favoring RAS-GDP). RAS activation - due to either extrinsic recruitment by transmembrane tyrosine kinase receptors or intrinsic mutations - propagates through the downstream RAF/MEK/ERK and PI3K/AKT signaling pathways. Besides RAS-activating mutations conferring independence from physiological regulators, human cancers harbor mutations in other RAS network genes such as NF1 (encoding neurofibromin, a RAS GAP), BRAF or PTPN11 (encoding the SHP2 tyrosine phosphatase involved in RAS activation). Somatic alterations of RAS pathway genes, notably NRAS, KRAS, PTPN11 (missense mutations) and NF1 (mutations and deletions), are reported in up to 20% of AML cases2. Generally arising as late driver events, RAS pathway mutations participate in leukemogenesis through mitogen activated protein kinase (MAPK) activation. The anti-tumor activity of MEK inhibitors in Nras-mutated AML in mice and in some NRAS or KRAS-mutated AML patients suggests that deregulated RAS pathway signaling may represent a bona fide therapeutic target. However, strategies to inhibit RAS - indirectly in most cases - have been hampered by signaling feedback, redundancy and tumor heterogeneity 3. We identified 127 cases of AML with unmet therapeutic need within a cohort from which we excluded those with European leukemia network (ELN) favorable prognosis or FLT3-ITD mutations. Targeted next-generation sequencing revealed RAS pathway alterations in 50 patients (39.3%) and NF1 mutations and deletions, mostly large cytogenetically detected deletions, in 17 (14.8%). NRAS, KRAS, PTPN11, CBL and BRAF variants were detected in 13 (10.4%), 10 (7.9%), 9 (7.2%), 5 (3.9%) and 2 (1.6%) cases, respectively. Mutations in RAF1, RASA1, SOS1 and MAP2K2 were observed in a single case each. RAS pathway alterations appeared in the putative main leukemic clone as well as in subclones inferred from variant allele frequencies. Concurrent RAS pathway mutations were observed in nine cases. Among 79 patients homogeneously treated with intensive induction chemotherapy, RAS pathway alterations correlated with higher clinical proliferation markers (elevated white blood cell count, blast cell percentage and LDH levels) and reduced survival probability, particularly within the ELN intermediate-risk subgroup. We established robust models of RAS/MAPK activation through genetic NF1 disruption or expression of NRASG12D or PTPN11D61Y in growth factor (GF)-dependent cell lines. We assessed oncogenic addiction to the RAS pathway in these cells through GF-independence, increased RAS activity, faster propagation in immunocompromised mice and an exquisite sensitivity to pharmacological MEK inhibition in vitro and in vivo. High-content pharmacological screens with FDA-approved molecules identified pyrvinium pamoate, an anti-helminthic agent, as preferentially active in RAS-activated cells. This compound significantly impaired cell viability and colony formation in primary AML samples with RAS pathway alterations. Moreover, the combination of trametinib and pyrvinium pamoate demonstrated synergy in cell line models and even primary samples. While pyrvinium pamoate strongly inhibited mitochondrial respiration and induced metabolic reprograming towards increased glycolysis, trametinib impaired glycolysis and mitochondrial respiratory capacity, suggesting a mechanistic basis for the synergy observed. These data highlight the translational opportunity in developing pyrvinium pamoate for RAS pathway mutated AML. References 1. Raj RV et al. Leuk. Res. 2018;74:113-120. 2. Simanshu DK et al. Cell. 2017;170(1):17-33. 3.Ryan MB et al. Nat Rev Clin Oncol. 2018;15(11):709-720. Figure Disclosures Hermine: AB Science: Membership on an entity's Board of Directors or advisory committees. Tamburini:Novartis pharmaceutical: Research Funding; Incyte: Research Funding.

Abstract: Background: Rivaroxaban is a direct oral anticoagulant (DOAC) with similar efficacy to vitamin K antagonists in the management of non-valvular atrial fibrillation (NVAF) and venous thromboembolism (VTE) but with a more favourable bleeding profile. Recent studies including the landmark COMPASS trial have demonstrated that rivaroxaban possesses cardioprotective and anti-inflammatory properties beyond its well-established anticoagulant effects however, these remain poorly characterized. The effects of FXa inhibition on the generation of circulating extracellular vesicles (EV) are currently unknown. We hypothesize that circulating proinflammatory EV profiles differ in patients treated with rivaroxaban compared to those treated with warfarin and that these changes may represent a novel biomarker for cardioprotective effects mediated by FXa inhibition. Methods: Patients stably anticoagulated with 20 mg Rivaroxaban (n=15) once daily or warfarin (n=15) (at a target INR of 2.0 - 3.0) who had commenced therapy no sooner than 3 months previously for VTE treatment or NVAF were recruited following informed consent at the Mater Misericordiae University Hospital, Dublin. Demographic and clinical data were collected including patient age, body mass index, smoking and alcohol history, medical comorbidities, white cell and platelet count, creatinine clearance, liver profile, medications, detailed indication for anticoagulation and time since last dose of medication. Patients receiving warfarin had a time in therapeutic range of 〉 55% and had an INR within target range at the time of sampling. Exclusion criteria included severe renal impairment (creatinine clearance 〈 30 ml/min), significant liver impairment, known proinflammatory conditions (including systemic lupus erythematosus, inflammatory bowel disease, rheumatoid arthritis), recurrent VTE, active malignancy, previous stroke or systemic inflammation, antiphospholipid syndrome, strong thrombophilia (eg antithrombin deficiency), individuals aged 〈 18, patients receiving inhibitory CYP3A4 and P-glycoprotein medications or platelet inhibitors, bleeding or platelet function disorders, and thrombocytopenia (platelet count 〈 150 x 109/ml) Total particle counts in platelet poor plasma were measured by Nanoparticle Tracking Analysis (NTA) and flow cytometry. NTA was carried out using a NanoSight NS300 (Malvern) with a camera level of 13 and a detection threshold of 10. 15 x 60 second videos were captured per sample. Flow Cytometry analysis was performed using a CytoFlex LX (Beckman Coulter). Gigamix beads (Biocytex) were used to establish size gates for 100, 300, 500 and 900 nm particles. Samples were analysed in triplicate. Statistical analysis was performed in RStudio (version 1.2.1335) using a two-tailed t-test with a significance level of 5%. Results and Conclusion: Overall, we observed lower circulating EV levels in patients anticoagulated with FXa inhibitors versus vitamin K antagonists (Figure 1). Within our groups, patients with NVAF exhibited overall lower EV particle counts than VTE patients. Interestingly, EV levels were observed to be further diminished in patients treated with rivaroxaban versus warfarin. In this group, we detected a 2.5-fold decrease in the level of circulating EVs in patients with NVAF (1.18x1011±5.03x1010 particles/mL vs 2.92x1011±2.08x1011 particles/mL, p=0.039) and a 1.7-fold decrease in patients with VTE (3.37x1011±2.46x1011 particles/mL vs 5.71x1011±1.471011 particles/mL, p=0.164), in contrast to warfarin treatment. Collectively, these data suggest that FXa inhibition reduces the generation of circulating EVs, independent of the disease. These findings are of translational relevance towards characterizing cardioprotective mechanisms associated with rivaroxaban therapy. Disclosures Ni Ainle: Leo Pharma: Research Funding; BMS: Membership on an entity's Board of Directors or advisory committees; Actelion: Research Funding; Bayer: Membership on an entity's Board of Directors or advisory committees, Research Funding; Boehringer: Membership on an entity's Board of Directors or advisory committees; Daiichi Sankyo: Membership on an entity's Board of Directors or advisory committees. Maguire:Bayer: Research Funding; Leo Pharma: Research Funding; Actelion: Research Funding.

Abstract: CCAAT enhancer-binding protein (CEBP) transcription factors play pivotal roles in proliferation and differentiation, including suppression of myeloid leukemogenesis. Mutations of CEBPA are found in a subset of acute myeloid leukemia (AML) and in some cases of familial AML. Here, using cytogenetics, fluorescence in situ hybridization (FISH), and molecular cloning, we show that 5 CEBP gene family members are targeted by recurrent IGH chromosomal translocations in BCP-ALL. Ten patients with t(8;14)(q11;q32) involved CEBPD on chromosome 8, and 9 patients with t(14;19)(q32;q13) involved CEBPA, while a further patient involved CEBPG, located 71 kb telomeric of CEBPA in chromosome band 19q13; 4 patients with inv(14)(q11q32)/t(14;14)(q11;q32) involved CEBPE and 3 patients with t(14;20)(q32;q13) involved CEBPB. In 16 patients the translocation breakpoints were cloned using long-distance inverse–polymerase chain reaction (LDI-PCR). With the exception of CEBPD breakpoints, which were scattered within a 43-kb region centromeric of CEBPD, translocation breakpoints were clustered immediately 5′ or 3′ of the involved CEBP gene. Except in 1 patient with t(14;14)(q11;q32), the involved CEBP genes retained germ-line sequences. Quantitative reverse transcription (RT)–PCR showed overexpression of the translocated CEBP gene. Our findings implicate the CEBP gene family as novel oncogenes in BCP-ALL, and suggest opposing functions of CEBP dysregulation in myeloid and lymphoid leukemogenesis.

Abstract: Patient-derived iPSCs recapitulate juvenile myelomonocytic leukemia. MEK inhibition normalizes GM-CSF independence and hypersensitivity in myeloid precursors from JMML iPSCs.

Abstract: Introduction: Acalabrutinib (acala) is an irreversible, second generation Bruton tyrosine kinase inhibitor (BTKi) approved by the FDA for the treatment of relapsed/refractory (R/R) mantle cell lymphoma, and is in advanced stages of clinical testing for front line (FL) and R/R CLL (Byrd NEJM, Wang NEJM). Ibrutinib (ibr) is a well-established and potent treatment for CLL; however, discontinuation due to intolerance precludes a significant number of patients (pts) in clinical practice from long-term benefit of this targeted therapy (Mato et al Blood 2016, Follows BJH 2017). Acala inhibits BTK more selectively than ibr, and while demonstrating impressive activity, may result in significantly less off-target adverse events (AEs). Although not yet FDA approved, it is being increasingly used in CLL pts with ibr-intolerance or cardiovascular or hematologic comorbidities (atrial fibrillation (AF), hypercoagulable state on long-term anticoagulation, etc.) to potentially avoid ibr-related toxicities. The increasing use of acala in clinical practice provides an opportunity to address various knowledge gaps. Therefore, we conducted a multi-institutional, retrospective analysis in CLL pts treated with acala in the real-world setting. We aimed to report and analyze the main reasons for starting acala, its safety, efficacy, outcome and sequencing. Patients and Methods: This multi-institutional, retrospective analysis included acala-treated CLL pts at 9 US cancer centers. We analyzed and described prior treatments, dosing of acala, discontinuations, toxicities and outcomes. The primary endpoint was progression-free survival (PFS) as predicted by the Kaplan Meier method. Results: 69 CLL pts treated with acala (off clinical trials) were identified. Baseline characteristics are described in Table 1. Median age was 70 years (range 51-89) and 6 (9%) and 63 (91%) pts received acala in the FL and R/R settings, respectively. Of the R/R pts, 49 (78%) had received a prior BTKi, 11 (17%) a phosphoinositide 3-kinase inhibitor (PI3Ki), 14 (22%) venetoclax, 18 (29%) bendamustine, and 17 (27%) fludarabine. Median time from diagnosis of CLL to starting acala was 79.5 months. Most common reasons for choosing acala were prior intolerance to other agents in 47 (68%), disease progression on the prior line of therapy in 19 (28%) and concern for intolerance to other therapies due to age/comorbidities in 9 (13%). Prior intolerance to ibr was the reason for starting acala in 46 (98%) of the intolerant pts; the most common AEs leading to discontinuation of ibr were rash in 10 (22%), AF/flutter in 8 (17%), arthralgia in 8 (17%), bleeding in 6 (13%), infection in 6 (13%) and fatigue in 6 (13%). Almost all pts (99%) started on acala 100 mg orally twice daily, with dose reductions required in 5 (7%). The most common toxicities on acala were fatigue in 9 (13%), infection in 9 (13%), diarrhea/colitis in 7 (10%), nausea/vomiting in 6 (9%), headache in 5 (7%), rash in 5 (7%), bleeding in 2 (3%) and AF/flutter in 1 (1%). The median time from the start of acala to an infection was 3 months. With a median follow-up of 5 months, the acala discontinuation rate was estimated to be 19% (13 pts) with median time to discontinuation of 1 month. The main reason for discontinuation was AEs in 8 pts (12%) (no consistent pattern of AEs), all in R/R pts with median time to discontinuation of 3.5 months; 2 others proceeded to CAR T-cell therapy or allogeneic transplant; 2 died of unrelated causes, 1 from progressive disease off acala. Overall response rate (ORR) was 62% (9% CR, 53% PR, number reported = 66), 50% PR in FL (3/6) and 63% (CR 5%, PR 58%, number reported = 60) in R/R pts. The differences likely reflected small numbers and short follow-up. Median PFS and overall survival were not reached (Figs 1a,b). Conclusion: In this group of largely ibr-intolerant pts, the overall acala discontinuation rate was lower than prior reports from clinical trials, although with relatively short follow up. However, discontinuation rate due to AEs appears to be similar to clinical trial data in an ibr-intolerant pt population (Awan Blood Adv, Rogers ICML 2019). These data demonstrate the need for the results of randomized studies, in order to compare the efficacy and AE profile of acala relative to ibr and other novel agents and Disclosures Yazdy: Genentech: Research Funding; Bayer: Honoraria, Speakers Bureau; Octapharma: Consultancy; Abbvie: Consultancy. Mato:Genentech: Consultancy, Research Funding; Pharmacyclics: Consultancy, Research Funding; Sunesis: Consultancy, Research Funding; Celgene: Consultancy; Johnson & Johnson: Consultancy, Research Funding; TG Therapeutics: Consultancy, Other: DSMB member , Research Funding; Acerta: Consultancy; Janssen: Consultancy; Gilead: Research Funding; DTRM Biopharma: Research Funding; AstraZeneca: Consultancy, Research Funding; AbbVie: Consultancy, Research Funding; LOXO: Consultancy, Research Funding. Roeker:AbbVie: Equity Ownership; Abbott Laboratories: Equity Ownership. Ujjani:Gilead: Consultancy; Atara: Consultancy; Genentech: Honoraria; AbbVie: Honoraria, Research Funding; PCYC: Research Funding; Pharmacyclics: Honoraria; PCYC: Research Funding; Pharmacyclics: Honoraria; Astrazeneca: Consultancy. Shadman:TG Therapeutics: Research Funding; Gilead: Research Funding; Merck: Research Funding; Bigene: Research Funding; Celgene: Research Funding; Acerta: Research Funding; Emergent: Research Funding; Sunesis: Research Funding; Mustang Biopharma: Research Funding; Atara: Consultancy; Pharmacyclics: Consultancy, Research Funding; Verastem: Consultancy; AbbVIe: Consultancy, Research Funding; Genentech, Inc.: Consultancy, Research Funding; AstraZeneca: Consultancy; Sound Biologics: Consultancy; ADC Therapeutics: Consultancy. Skarbnik:Genentech: Honoraria, Speakers Bureau; Seattle Genetics: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Acerta: Research Funding; Novartis: Speakers Bureau; Jazz Pharmaceuticals: Speakers Bureau; Abbvie: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Pharmacyclics: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Janssen: Consultancy, Honoraria, Research Funding, Speakers Bureau; Verastem Oncology: Honoraria, Research Funding, Speakers Bureau; Kite Pharma: Honoraria, Speakers Bureau; Gilead Sciences: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Celgene: Consultancy, Honoraria, Speakers Bureau; CLL Society: Consultancy, Membership on an entity's Board of Directors or advisory committees. Pagel:AstraZeneca: Consultancy; Gilead Sciences: Consultancy; Pharmacyclics: Consultancy. Patel:Sunesis: Consultancy; Pharmacyclics/Janssen: Consultancy, Speakers Bureau; Celgene: Consultancy, Speakers Bureau; AstraZeneca: Consultancy, Research Funding, Speakers Bureau; Genentech: Consultancy, Speakers Bureau. Jacobs:AstraZeneca: Speakers Bureau; Gilead: Consultancy; Genentech: Speakers Bureau; JUNO: Consultancy; TG Therapeutics: Honoraria, Research Funding; AbbVie: Consultancy, Speakers Bureau; Pharmacyclics LLC, an AbbVie Company: Research Funding, Speakers Bureau. Feldman:Portola Pharma: Research Funding; Roche: Research Funding; Corvus: Research Funding; Eisai: Research Funding; Kyowa Hakko Kirin: Research Funding; Roche: Research Funding; Trillium: Research Funding; Viracta: Research Funding; Pfizer: Research Funding; Bayer: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Pharmacyclics: Honoraria, Other: Travel expenses, Speakers Bureau; Janssen: Honoraria, Speakers Bureau; Takeda: Honoraria, Speakers Bureau; Celgene: Honoraria, Research Funding, Speakers Bureau; Seattle Genetics: Consultancy, Honoraria, Other: Travel expenses, Speakers Bureau; AbbVie: Honoraria, Other: Travel expenses, Speakers Bureau; Amgen: Research Funding; Cell Medica: Research Funding; Kite Pharma: Honoraria, Other: Travel expenses, Speakers Bureau. Goy:University of Nebraska: Research Funding; Acerta: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Grants outside of the submitted work, Research Funding; Hakensackumc: Research Funding; Hackensack University Medical Center, RCCA: Employment; Genentech: Other: Grants outside of the submitted work, Research Funding; Pharmacyclics/Janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Grants outside of the submitted work, Research Funding; Takeda: Other: Grants outside of the submitted work; Astrazenca: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Kite, a Gilead Company: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Grants outside of the submitted work; COTA: Equity Ownership, Membership on an entity's Board of Directors or advisory committees, Other: leadership role for profit healthcare company; Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees. Coombs:Pharmacyclics: Honoraria; Loxo: Honoraria; H3 Biomedicine: Honoraria; Octopharma: Honoraria; Dedham Group: Consultancy; Cowen & Co.: Consultancy; Medscape: Honoraria; Abbvie: Consultancy; Covance: Consultancy. Lamanna:Celgene: Consultancy; Infinity/ Verastem: Research Funding; Ming: Research Funding; TG Therapeutics: Research Funding; Oncternal: Research Funding. Weiss:TG Therapeutics: Other: family member with employment and equity) . Cheson:AstraZeneca: Membership on an entity's Board of Directors or advisory committees; Acerta: Consultancy, Research Funding; Pharmacyclics: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Morphosys: Membership on an entity's Board of Directors or advisory committees; Bristol Myers Squibb: Research Funding; Portola: Research Funding; Kite: Research Funding; Gilead: Research Funding; Epizyme: Research Funding; Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Symbios: Equity Ownership, Membership on an entity's Board of Directors or advisory committees; Abbvie: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Trillium: Research Funding; TG Therapeutics: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Seattle Genetics: Research Funding; Genentech: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding. OffLabel Disclosure: Acalabrutinib is an irreversible, second generation Bruton tyrosine kinase inhibitor approved by the FDA for the treatment of relapsed/refractory (R/R) mantle cell lymphoma, and is in advanced stages of clinical development testing for front line (FL) and R/R CLL. Although not yet FDA approved, it is being increasingly used in CLL patients in clinical practice. This highlights the necessity to address various knowledge gaps.

Abstract: Erythrocytes undergo a well-defined switch from fetal to postnatal circulation, which is mainly reflected by the stage-specific expression of hemoglobin chains. Perinatal alterations in thrombopoiesis are poorly understood. We assessed the ontogenesis of platelet phenotype and function from early prematurity to adulthood. We recruited 64 subjects comprising 7 extremely preterm (27-31 weeks gestational age), 25 moderately preterm (32-36 weeks), 10 term neonates, 8 infants ( & lt;2 years), 5 children (2-13 years), and 9 adults ( & gt;13 years). Blood was withdrawn at up to 3 different time points in neonates (t1: 0-2, t2: 3-7, and t3: 8-14 days after birth). We found that the expression levels of the major surface receptors for fibrinogen, collagen, vWF, fibronectin, and laminin were reduced but correlated with decreased platelet size, indicating a normal surface density. Although CD62P and CD63 surface exposure upon stimulation with TRAP-6, ADP, or U46619 was unaltered or only slightly reduced in neonates, GPIIb/IIIa inside-out and outside-in activation was blunted but showed a continuous increase until adulthood, correlating with the expression of the GPIIb/IIIa regulating tetraspanin CD151. Platelet subpopulation analysis using automated clustering revealed that neonates presented with a CD63+/PAC-1– pattern, followed by a continuous increase in CD63+/PAC-1+ platelets until adulthood. Our findings revealed that the number of platelet-monocyte and platelet-neutrophil aggregates, but not platelet-lymphocyte aggregates, is increased in neonates and that neonatal aggregate formation depends in part on CD62P activation. Our PLatelets In Neonatal Infants Study (PLINIUS) provides several lines of evidence that the platelet phenotype and function evolve continuously from neonates to adulthood.

Abstract: Background: Patients with hematologic malignancy (HM) are hypothesized to be at high risk of poor outcomes with coronavirus disease 2019 (COVID-19), due to disease and therapy-related immunosuppression. Despite this, there are minimal reported data describing the outcomes of HM patients with COVID-19. Methods: The COVID-19 and Cancer Consortium (CCC19) (NCT04354701) is an international registry aimed at investigating the clinical course and complications of COVID-19 in patients with cancer. The CCC19 cohort includes patients with active cancer or a history of cancer with presumed or laboratory-confirmed COVID-19. The registry contains de-identified patient demographics, information regarding cancer diagnosis and treatment history, COVID-19 treatments, and clinical outcomes. Patients greater than 18 years of age with laboratory-confirmed, symptomatic COVID-19 and HM diagnoses were included in this study. The primary outcome is a composite of severe COVID-19 illness (composed of mechanical ventilation, severe illness requiring hospitalization, intensive care unit (ICU) requirement, or death); mechanical ventilation, ICU level of care, supplemental oxygen, and 30-day mortality are reported as secondary outcomes. Baseline characteristics are reported for the entire cohort. Reported clinical outcomes are stratified by cancer type, cancer status, line of therapy received (never treated, first, second or later), receipt of cellular therapy or transplant (none, within 12 months, & gt;12 months prior to COVID-19 diagnosis), last receipt of cytotoxic therapy (within 4 weeks, 1-3 months, 3-12 months prior to COVID-19 diagnosis), and receipt of HM therapies under investigation as repurposed treatments for COVID-19 (Bruton tyrosine kinase (BTK) inhibitors, Janus kinase (JAK) inhibitors, Bcr-Abl kinase inhibitors). Results: From March 17, 2020 to July 31, 2020, a total of 757 patients with HM and COVID-19 were enrolled and met inclusion criteria. Median follow-up was 30 days (IQR 17-70 days). Median age was 65 years (IQR 55-75), 62% (470) were over age 60, 57% were men, 45% were non-Hispanic white (22% Black, 18% Hispanic, 5% other), 39% were former or current smokers, 27% were obese, 18% had Eastern Cooperative Oncology Group (ECOG) performance status ≥2, and 51% were on active treatment within 3 months of COVID-19 diagnosis. Among patients with HM, 281 (37%) developed the primary endpoint. Five-hundred and eleven patients (67%) were hospitalized (some with non-severe disease), 188 (25%) required ICU level of care, 133 (18%) required mechanical ventilation, 409 (54%) required supplemental oxygen, and 143 (19%) died within 30 days of COVID-19 diagnosis. Stratified rates of severe outcomes are shown in the Table. The rate of severe COVID-19 was highest in patients with chronic lymphocytic leukemia (53%), and lowest in patients with Hodgkin lymphoma (23%). Patients receiving cytotoxic systemic therapy within 3 months of COVID-19 diagnosis had higher rates of severe COVID-19 (41%) and 30-day mortality (28%) than patients who completed treatment 3-12 months (26% severe COVID-19, 16% 30-day mortality) or more than 12 months (29% severe COVID-19, 13% 30-day mortality) prior to COVID-19 diagnosis. Patients receiving cellular therapy or transplant within a year prior to COVID-19 diagnosis had similar rates of severe COVID-19 (36% v. 38%) and 30-day mortality (23% v. 19%) to patients who had not received such therapies within a year prior to COVID-19 diagnosis. Patients on second-line or later therapy experienced similar rates of poor outcomes (42% severe COVID-19, 20% 30-day mortality) to patients on first-line therapy (39% severe COVID-19, 18% 30-day mortality) and untreated patients (42% severe COVID-19, 20% 30-day mortality). Outcomes for patients receiving therapies under investigation as repurposed COVID-19 treatments were similar to the cohort at large. Conclusions: This is the largest cohort study to date describing COVID-19 outcomes in patients with HM. Rates of severe COVID-19 outcomes including death were high. Unadjusted rates of severe COVID-19 outcomes were higher in patients with previously described risk factors such as advanced age, poor performance status, and progressive disease, as well as those receiving recent cytotoxic therapy. Outcomes varied widely by malignancy but were similar across treatment contexts. Additional data collection and analyses are ongoing. Disclosures Lynch: Bayer: Research Funding; Rhizen Pharmaceuticals: Research Funding; Incyte: Research Funding; TG Therapeutics: Research Funding; Takeda: Research Funding; Juno Therpeutics: Research Funding; Genentech: Research Funding; MorphoSys: Consultancy; Cyteir: Research Funding. Bakouny:BMS: Research Funding; Genentech: Research Funding. Bhutani:Sanofi: Consultancy, Research Funding. Shah:American Cancer Society and the Hope Foundation for Cancer Research: Research Funding; National Cancer Institute: Research Funding. Lyman:Mylan: Consultancy; Beyond Spring: Consultancy; Samsung: Consultancy; Sandoz: Consultancy; Invitae: Consultancy; Spectrum: Consultancy; G1 Therapeutics: Consultancy; Amgen: Research Funding. Kuderer:Janssen: Consultancy; G1 Therapeutics: Consultancy; Beyond Springs: Consultancy; Spectrum Pharmaceuticals: Consultancy; Bayer: Consultancy; Bristol-Myers Squibb: Consultancy; celldex: Consultancy; Total Health: Consultancy; Invitae: Consultancy. Warner:HemOnc.orgLLC: Other: Shareholder/Stockholder/Stock options; National Cancer Institute: Research Funding; IBM Watson Health: Consultancy; Westat: Consultancy. Mesa:Bristol Myers Squibb: Research Funding; Incyte: Research Funding; AbbVie: Research Funding; Samus Therapeutics: Research Funding; Genentech: Research Funding; Promedior: Research Funding; CTI BioPharma: Research Funding; Novartis: Consultancy; Sierra Oncology: Consultancy; LaJolla Pharmaceutical Company: Consultancy. Thompson:AIM Specialty Health, BMS, GlaxoSmithKline, Takeda, Via Oncology: Membership on an entity's Board of Directors or advisory committees; Doximity: Current equity holder in publicly-traded company, Membership on an entity's Board of Directors or advisory committees; Synapse Precision Medical Council: Other: Travel expenses.