ALBERT

Description: Ciraparantag, an anticoagulant reversal agent, is a small molecule specifically designed to bind non-covalently by charge-charge interaction to unfractionated heparin (UFH) and low molecular weight heparin (LMWH). It shows similar binding characteristics to the direct oral anticoagulants (DOAC). Dynamic light scattering methodology was used to demonstrate ciraparantag binding to the heparins and DOACs and its lack of binding to a variety of proteins including coagulation factors and to commonly used drugs. Ciraparantag reaches maximum concentration within minutes following intravenous (IV) administration with a half-life of 12 - 19 minutes. It is primarily hydrolyzed by serum peptidases into two metabolites, neither of which has substantial activity. Ciraparantag and its metabolites are recovered almost entirely in the urine. In animal models of bleeding (rat tail transection and liver laceration) a single IV dose of ciraparantag given at peak concentrations of the anticoagulant, but before the bleeding injury, significantly reduces the amount of blood loss. Ciraparantag given after the bleeding injury also significantly reduces blood loss. Ciraparantag appears to have substantial ability to reduce blood loss in animal models given a variety of anticoagulants and has potential as a useful DOAC reversal agent.

Description: Introduction A retrospective study (Russell JA et al. BBMT 2010) showed additional 400 cGy of total body irradiation (TBI) to Flu/Bu regimen improved both overall survival and disease-free survival. To investigate the role of additional TBI 400 cGy in Flu/Bu4 conditioning regimen, we conducted a prospective randomized comparative study of fludarabine/busulfan (Flu/Bu4) and fludarabine/busulfan/total body irradiation (Flu/Bu4/TBI) conditioning regimen in allogeneic hematopoietic stem cell transplantation for patients with myeloid diseases. Methods We prospectively enrolled patients with myeloid diseases and randomized to Flu/Bu4 or Flu/Bu4/TBI between July 2010 and August 2019. Patients were stratified by diagnosis and disease risk. Patients received fludarabine 40 mg/m2 on days -6 to -3 followed by IV busulfan 130 mg/m2 on days -6 to -3 (Flu/Bu4). Flu/Bu4/TBI group had additional 400 cGy TBI in two fractions on day -1. Recipients had rATG 4 mg total dose over 3 days on days -3 to -1. All patients received post-transplant immunosuppression with tacrolimus and methotrexate 5 mg/m2 on days +1, 3, 6, and 11. We analyzed overall survival (OS), leukemia free survival (LFS), non-relapse mortality (NRM), relapse, acute- and chronic graft versus-host disease (GvHD). Results Forty-six (27 male and 19 female) patients with myeloid diseases were randomized into Flu/Bu4 (24 patients) or Flu/Bu4/TBI (22 patients). Patients had AML (34 patients), CML (1 patient), MDS (5 patients), MF (3 patients), and CMML (3 patients) with mean age 49.2 (22-63 years) (Table 1). There were no graft failures. One patient died within 100 days of transplantation due to organ failure. Among 46 patients, eleven patients died within a year of transplantation (5 patients in Flu/Bu4, 6 patients in Flu/Bu4/TBI), 5 from disease progression, 3 from acute GVHD, 1 from infection, 1 from fall, and 1 from organ failure. Day 100 grade II-IV and III-IV acute GVHD rates were 45.7% (95% CI [31.3, 60.1]) and 10.9% (95% CI [1.9, 30.8]), respectively; 1-year chronic GVHD and extensive chronic GVHD rates were 39.1% (95% CI [25.0, 53.2]) and 13.0% (95% CI [3.3, 22.8]), respectively. With a median follow up of 22.6 months (range, 1.8-114.7), NRM at day 100 was 2.2% (n=1) and 10.9% at 1 year. Overall survival (OS), leukemia-free survival (LFS) and relapse at 1-year were 74.4%, 41.9%, and 30.2%, respectively. Among 34 AML patients, LFS for all AML patients was 52.9% at 1 years. LFS was higher in patients undergoing Flu/Bu4/TBI with 56.3% versus Flu/Bu4 with 50.0% at 1 year (p=0.4). AML relapse with Flu/Bu4 and Flu/Bu4/TBI regimen was 38.9% versus 18.8% in the first year, 44.4% versus 25.0% in three years (RR=0.61 95% CI [0.20, 1.91]) (Fig 1). However, Flu/Bu4/TBI regimen increased the risk of NRM in AML patients (60.0% versus 14.3%, p=0.22). Overall survival (OS) for all AML patients was 67.6% at 1 year. OS of AML patients was similar in patients undergoing Flu/Bu4 with 72.2% versus Flu/Bu4/TBI with 62.5% at 1 year (p=0.4). The median survival was 26.9 months and 21.4 months, respectively. Conclusions Addition of TBI 400 cGy to Flu/Bu4 conditioning regimen resulted in reduction of relapse, contributing to a better LFS. However, Flu/Bu4/TBI group did not have a better OS due to the regimen related mortality. These findings suggest the additional TBI 400 cGy to Flu/Bu4 should be cautiously selected for patients who is fit but has a high risk of relapsed disease. Disclosures Rowley: FATE Therapeutics: Consultancy; AbbVie: Current equity holder in publicly-traded company. Skarbnik:Jazz Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Kite Pharma: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees; Janssen: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; CLL Society: Membership on an entity's Board of Directors or advisory committees; AstraZeneca: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Gilead: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Seattle Genetics: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Novartis: Speakers Bureau; Verastem: Speakers Bureau; Beigene: Speakers Bureau; Alexion: Consultancy; Abbvie: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Genentech: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Pharmacyclics: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Vesole:Janssen: Speakers Bureau; Sanofi: Speakers Bureau; BMS: Speakers Bureau; Amgen: Speakers Bureau; Takeda: Speakers Bureau. Donato:Genomics Cooperative: Current equity holder in publicly-traded company.

Description: Introduction: Inborn errors of immunity such as hemophagocytic lymphohistiocytosis (HLH) and chronic granulomatous disease (CGD) are characterized by hyperinflammation. Hematopoietic cell transplantation (HCT) in the setting of hyperinflammation leads to high morbidity and mortality. Consequently, there is increasing use of less intense conditioning regimens, which can increase risk of mixed chimerism or graft failure. We sought to study the effect of common regimens on outcomes after HCT using data reported to the Center for International Blood and Marrow Transplant Research. Methods : 365 patients aged

Description: Introduction Regulatory T cell (Treg) based therapies are a promising approach for graft-versus-host disease (GvHD) prevention and treatment. However, mechanisms of Treg suppression of alloreactive conventional T cells (Tcon) in GvHD are incompletely understood. In this study, we performed paired RNA and T cell receptor (TCR) sequencing analysis on Tcon and Treg before and after transplantation to further elucidate Treg suppressive function during in vivo suppression of acute GvHD in an MHC major-mismatch mouse model. Methods CD45.2 Thy1.2 BALB/c mice were lethally irradiated (8.8 Gy) and transplanted with 5x106 T cell- depleted bone marrow cells (TCD-BM) from CD45.1 Thy1.2 C57Bl/6 mice alone or together with CD45.2 Thy1.2 C57Bl/6 FoxP3/GFP+ Treg (1x106) on day 0. On day 2, CD45.1 Thy1.1 C57Bl/6 Tcon (1x106; CD4:CD8 ratio = 2:1) were injected to induce GvHD. Irradiated (11 Gy) syngeneic C57Bl/6 recipients receiving C57Bl/6 TCD-BM and CD45.1 Thy1.1 Tcon alone were used as controls. On day 8, donor Thy1.1+ CD45.1+ CD4 and CD8 Tcon and Thy1.2+CD45.2+ FoxP3/GFP+ Treg were isolated by FACS from spleens and lymph nodes. T cell subsets before injection and recovered at day 8 were analyzed by paired RNA and TCR sequencing. Results The transcriptomic analysis revealed a dominant effect of the allogeneic transplant procedure on the clustering of the different T cell populations. Principal component analysis (PCA) of the top 1000 most differentially expressed genes revealed that 68% of the variance was explained by PC1, which clearly segregated CD4and CD8Tcon recovered at day 8 from allogeneic recipients from cells before injection or recovered from syngeneic recipients (Fig. 1). PC1 was mainly driven by naïve T cell genes (Ccr7, Sell, Il6ra, Il6st, Foxo1) that were progressively downregulated along PC1. Analysis of the TCR repertoire based on sequencing of the TCR alpha chain revealed a progressive clonal restriction along PC1 in CD4 and CD8 T cells (Fig. 1). Accordingly, clonal overlap between cells collected at day 8 and cells analyzed before injection were reduced in allogeneic recipients (Morisita Index [MI], CD4: 0.06±0.01; CD8: 0.02±0.01) compared to syngeneic controls (MI, CD4: 0.23±0.26; CD8: 0.57±0.05). Treg administration did not affect CD4 or CD8 T cell segregation along PC1, suggesting that they minimally interfered with cell activation and differentiation during GvHD. Accordingly, Treg did not inhibit clonal restriction (Fig.1) nor the reduction in clonal overlap (MI, CD4: 0.04±0.01; CD8: 0.01±0.01), indicating that Treg did not inhibit the initial activation of alloreactive T cells clones. Treg impact on CD4 but not CD8 Tcon transcriptome was revealed by PC2 (Fig.1). Treg induced the downregulation of TH1-signature genes (Tbx21, Il12rb1, Il12rb2, Stat4) and proinflammatory genes (Il18rap) while promoting up-regulation of anti-inflammatory genes (Il18bp), TH2 signature genes (Ccr4, Il4) and Il2 in CD4Tcon. Moreover, gene set enrichment analysis (GSEA) revealed that Treg treatment significantly impacted gene sets involved in metabolic processes in CD4and CD8Tcon, leading to a global up-regulation of genes encoding for enzymes involved in oxidative phosphorylation (OXPHOS) and downregulation of genes encoding for enzymes contributing to glycolysis (Slc2a1, Hk1, Pfkl, Pfkp, Pkm). Treg recovered at day 8 preserved a distinct transcriptomic signature observed before injection and further enhanced by the up-regulation of genes involved in Treg activation and suppressive function (Gata3, Tnfrsf18, Tnfrsf4, Icos, Ccr1, Ccr4, Il9r). GSEA in Treg revealed significant up-regulation of genes in the OXPHOS signature. TCR repertoire analysis showed clonal restriction of Treg during GvHD. Direct comparison of clone frequencies in Treg and CD4Tcon showed smaller clonal overlap on day 8 (MI=0.005±0.006) compared to day 0 (MI= 0.11±0.004) suggesting that Treg and CD4Tcon responses during GvHD are engaging different cell clonotypes triggered by different epitopes or antigens. Conclusion Our results indicate that Treg treatment did not interfere with Tcon activation and differentiation of alloreactive Tcon clones in a model of acute GvHD. Treg predominantly affected CD4Tcon and to a lesser extent CD8Tcon transcriptome, modulating the transcription of genes encoding pro- and anti-inflammatory molecules as well as enzymes involved in metabolic processes. Disclosures Turkoz: Adicet Bio: Current Employment, Current equity holder in private company. Negrin:Magenta Therapeutics: Consultancy, Current equity holder in publicly-traded company; BioEclipse Therapeutics: Current equity holder in private company; Amgen: Consultancy; KUUR Therapeutics: Consultancy; Biosource: Current equity holder in private company; UpToDate: Honoraria.

Description: Background: Idiopathic hypereosinophilia and hypereosinophilic syndrome (HES) comprise a rare, heterogeneous group of hematologic disorders characterized by the overproduction of eosinophils leading to tissue eosinophilic infiltration and damage. Hypereosinophilia can be primary - due to a clonal or malignant process - or secondary to a non-clonal process. Primary eosinophilia can be accompanied by clonal markers, such as in myeloid/lymphoid neoplasms with eosinophilia and rearrangement of PDGFRA/B, FGFR1 or PCM1-JAK2, genetic mutations or chromosomal abnormalities leading to a diagnosis of chronic eosinophilic leukemia. Without easily identifiable clonal markers, a diagnosis of idiopathic HES is made after secondary causes are excluded. Thrombotic complications in clonal eosinophilic disorders have been described in case reports but the prevalence of thrombosis has not been extensively studied. We hypothesized that HES is associated with an increased thrombotic risk compared to the general population. Additionally, given the known increased thrombotic risk in patients with clonal hematopoiesis of indeterminate potential, we also hypothesized that the risk of thrombosis is greatest in HES patients with evidence of an underlying clonal process. Methods: Using an institutional database, we retrospectively analyzed 44 patients with HES who had undergone molecular testing with a DNA based next generation sequencing (NGS) assay (Heme SnapShot) and an RNA based NGS assay (Heme fusion) as part of their work up for HES at Massachusetts General Hospital from 2016 to 2020. Patients with secondary eosinophilia were excluded. We used Fisher's exact test to compare rates of thrombotic events or death between patients with and without molecular aberration. Relative risk and corresponding 95% CI was estimated by fitting a log-binomial regression model. Results: Among the 44 patients analyzed, 16 (36.4%) had a molecular aberration detected on NGS. Of the patients with molecular aberrations detected, 4 (25%) had PGFRA, PGFRB, or FGFR1 fusions. Other pathogenic mutations were as follows - 1 (6.3%) JAK2 mutation, 3 (18.8%) TET2, 1 (6.3%) DNMT3A and 9 (56.4%) had mutations in other genes. White blood cell count, absolute eosinophil count, hematocrit, platelet count, tryptase and vitamin B12 levels at diagnosis of HES were similar between the two groups. After a median follow-up time of 29 months (IQR 19.3, 52), 9 (20.5%) of all HES patients had a thrombotic event after diagnosis of HES (4 venous and 5 arterial) with a median time to first thrombotic event of 14.0 months (IQR 3.5, 28.0). HES patients with a molecular aberration had increased number of thrombotic events compared to HES patients with no molecular aberrations, 37.5% versus 10.7% respectively (p = 0.053, risk ratio 3.5, 95% CI 1.01 - 12.12). Three patients with molecular aberrations died versus 1 patient with no molecular aberrations (p = 0.129, risk ratio 5.25, 95% CI 0.59 - 46.36). Among patients with at least 12 months of follow-up (n = 40, 14 with and 26 without molecular aberrations), the one-year cumulative incidence of thrombotic events was 42.9% in patients with molecular aberrations vs 11.5% without (p = 0.044, RR 3.7 95% CI 1.2-12.0). HES patients who had thrombotic events had an increased risk of death compared to those without thrombotic events (p = 0.0226, RR 11.7, 95% CI 1.8 - 75.2). Conclusions: Thrombotic complications are common in the current study of patients with HES and are associated with an increased risk of death. Although our patient cohort was small, presence of molecular aberrations had increased rates of thrombotic events and mortality, suggesting an area of further study including possible therapeutic trials. Figure 1 Disclosures Brunner: Takeda: Research Funding; Celgene: Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Research Funding; AstraZeneca: Research Funding; Forty-Seven Inc: Membership on an entity's Board of Directors or advisory committees; Jazz Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees. Al-Samkari:Argenx: Consultancy; Amgen: Research Funding; Dova: Consultancy, Research Funding; Agios: Consultancy, Research Funding; Rigel: Consultancy. Rosovsky:Bristol-Myers Squibb, Janssen: Research Funding; Bristol-Myers Squibb, Dova, Janssen, Portola: Consultancy. Fathi:PTC Therapeutics: Consultancy; Takeda: Consultancy; TrovaGene: Consultancy; Amgen: Consultancy; Bristol-Myers Squibb: Consultancy, Research Funding; Celgene: Consultancy, Research Funding; Astellas: Consultancy; Novartis: Consultancy; NewLink Genetics: Consultancy, Honoraria; Daiichi Sankyo: Consultancy; Forty Seven: Consultancy; Jazz: Consultancy, Honoraria; Kite: Consultancy, Honoraria; Trillium: Consultancy; Seattle Genetics: Consultancy, Research Funding; Pfizer: Consultancy; Kura: Consultancy; Boston Biomedical: Consultancy; Blue Print Oncology: Consultancy; AbbVie: Consultancy; Agios: Consultancy, Research Funding; Amphivena: Consultancy, Honoraria. Weitzman:Abbvie: Consultancy. Hobbs:Incyte: Research Funding; Bayer: Research Funding; Novartis: Honoraria; Celgene/BMS: Honoraria; Merck: Research Funding; Constellation: Honoraria, Research Funding; Jazz: Honoraria.

Description: Background: Post-partum hemorrhage (PPH) is a major cause of maternal mortality. The risk of death from PPH is approximately 1 in 1000 deliveries(Carroli et al., 2008). Tranexamic acid (TXA) is a recommended treatment for women with severe PPH as it significantly reduces blood loss, need for surgical intervention and maternal mortality from hemorrhage (Abdul-Kadir et al., 2014; Ducloy-Bouthors et al., 2011; Li et al., 2017). Despite evidence supporting the use of TXA in this setting, there remain concerns and reluctance with its use stemming from the known increased risk of venous thromboembolism (VTE) in women post-partum (Tepper et al., 2014; James, 2009). Much of the data on TXA use has come from studies conducted on women without a bleeding disorder. Women with inherited bleeding disorders are at a substantially greater risk of PPH with maternal mortality from PPH estimated to be 10 times higher than average(Abdul-Kadir et al., 2014; James & Jamison, 2007). The safety and efficacy of peri-partum use of TXA in this population warrants study given their increased baseline risk of PPH and lower risk of thromboembolism (James & Jamison, 2007; Martin & Key, 2016). Methods: A retrospective cohort study was conducted on all women with inherited bleeding disorders known to our Multidisciplinary Clinic for Women with Inherited Bleeding Disorders (MCWBD) who received TXA peri-partum between July 2014 and December 2019. The primary objective was to evaluate the frequency of VTE amongst patients with inherited bleeding disorders who received peri-partum TXA. The secondary objective was to evaluate the frequency of primary and secondary PPH among those who did and did not receive TXA. Research ethics board approval was obtained. Descriptive statistical analyses were used. Results: There were no VTE events in all MCWBD patients who received TXA peri-partum. A total of 40 patients with inherited bleeding disorders were managed from the beginning of pregnancy to labour and delivery under the care of the MCWBD between July 2014 and December 2019. The distribution of primary bleeding disorder diagnoses is 37.5% (15/40) for von Willebrand disease, 30% (12/40) had platelet function disorders, 22.5% (9/40) were symptomatic hemophilia carriers and 10% (4/40) had a rare factor deficiency (see Figure 1). Of these patients, 25% (10/40) had a personal previous history of PPH and 13% (5/40) had a family history of PPH. Among the 40 women, 75% (30/40) gave birth vaginally. TXA was provided to 95% (38/40) of patients at the onset of the second stage of labour, during the postpartum period (minimum of 10 days of oral TXA treatment), or both. Primary PPH occurred in 13% (5/38) of women who received prophylactic TXA and in 1 out 2 (50%) women without prophylactic TXA (see Table 1). There were no reports of secondary PPH. Conclusions: TXA appears to be a safe preventative treatment for PPH in patients with inherited bleeding disorders based on our retrospective study, with no additional risks of thromboembolism observed. Prospective evaluation of peripartum TXA use in this patient population is warranted to further assess its efficacy. Disclosures Martin: Borden Ladner Gervais LLP: Consultancy. Sholzberg:NovoNordisk: Honoraria, Other: Scientific Advisory Board; Novartis: Honoraria, Other: Scientific Advisory Board; Takeda: Honoraria, Other: Scientific Advisory Board, Research Funding; Amgen: Honoraria, Other: Scientific Advisory Board, Research Funding; Octapharma: Honoraria, Other: Scientific Advisory Board, Research Funding.

Description: BACKGROUD Improved care and prophylactic factor replacement therapy have lengthened life expectancy for persons with hemophilia (PWH). These advancements have created a new hemophilia cohort of senior persons not seen since the previous human immunodeficiency viruses (HIV) years, and little is known about their age-related health outcomes. OBJECTIVES We describe the impact of hemophilia on comorbidities, joint problems, healthcare utilization and health related quality of life (HRQoL) from the HUGS VII baseline data. METHODS HUGS VII prospectively examines the cost and burden of hemophilia, including HRQoL, arthropathy, and economic impact in persons with hemophilia A or B age ≥ 40 years who obtained care from three US Hemophilia Treatment Centers. Participants completed a standardized interview to collect clinical and sociodemographic characteristics, hemophilia treatment regimen, pain, joint problems, comorbidities, and HRQoL using EQ-5D-3L. Clinical chart reviews documented hemophilic severity and treatment. Participants' characteristics were compared between two age groups: 40-49 years and ≥ 50 years using Chi-square tests for categorical variables and T-tests for continuous variables. RESULTS This analysis includes a total of 70 male with hemophilia, 64.3% aged ≥50 years, 75.7% with hemophilia A. Individuals ≥ 50 years had higher rates of being married or with a partner (71.11% vs. 56.0%, P=0.20), retired/not employed (66.7% vs. 28.0%, P=0.002), and having mild or moderate hemophilia (68.9% vs. 40.0%, P=0.02) than those 40-49 years old. Use of prophylaxis was similar among age groups in severe hemophilia but lower for older mild/moderate PWH. Among persons with mild/moderate hemophilia, those ≥ 50 years old reported a higher rate of joint pain (83.8% vs 70.0%, P=0.37) or range of motion limitation (73.3% vs, 60.0%, p=0.45) than the younger group, although the differences were not statistically significant. Compared to those 40-49 years old, individuals ≥ 50 years old reported fewer emergency room visits (4.6% vs. 20.8%, P=0.03), and physical therapy visits (16.0% vs. 41.7%, P=0.06). The older age group had significantly higher rates of self-reported myocardial infarction (11.6% vs. 0%, P=0.08) and diabetes (24.4% vs. 4.0%, P=0.03) than those 40-49 years. Self-reported comorbidities were measured by asking "Has a doctor ever told you that you have certain conditions?" The most frequently reported comorbidities were hepatitis C infection (75.7%, 79.3% of persons with infected hepatitis C had been treated and, 82.7% cleared the hepatitis C virus), hypertension (47.1%), depression (23.2%) and anxiety (21.7%). Mean covariates adjusted EQ-5D index score was lower in older persons (0.79 vs. 0.87, P=0.09). CONCLUSIONS Older PWH are over-represented by individuals with mild/moderate disease, potentially due to premature death among those with severe disease. Although this group included a larger proportion of mild disease than younger PWH, it presented prevalent comorbidities both of aging and of hemophilic arthropathy, despite lower rates of healthcare utilization and use of preventive therapies. Disclosures Curtis: USC Hemophilia Utilization Group Study (HUGS): Consultancy; Patient Reported Outcomes, Burdens and Experiences: Consultancy; Bayer: Consultancy; Novo Nordisk: Consultancy. Konkle:Pfizer: Consultancy, Research Funding; Roche: Consultancy; BioMarin: Consultancy; Sigilon: Consultancy, Research Funding; Sanofi: Consultancy, Research Funding; Takeda: Research Funding; Uniquire: Research Funding; CSL Behring: Consultancy; Baxalta: Research Funding; Spark: Consultancy, Research Funding. Kulkarni:Sanofi/ Bioverativ, Bayer, Biomarin, Shire/Takeda, Novo Nordisk, Freeline: Other: clinical trial research grants ; Bioverativ/Sanofi, BPL, Genentech, Kedrion, Novo Nordisk, Octapharma, Pfizer, Takeda, Catalyst Bioscience Bayer: Membership on an entity's Board of Directors or advisory committees. Wu:Baxalta US Inc., Bannockburn, IL (a Takeda Company), CSL Behring L.L.C., and Octapharma USA, Inc.: Research Funding. Tran:Takeda: Consultancy; Novo Nordisk: Consultancy; Bayer: Consultancy; Bioverativ: Consultancy. Nichol:Global Blood Therapeutics: Research Funding; CSL Behring: Research Funding; Octapharma: Research Funding; Genentech Inc.: Research Funding; Baxalta US Inc., Bannockburn, IL (a Takeda Company): Research Funding; Pfizer: Research Funding.

Description: By presenting a patient's own tumor antigens to their immune system, autologous cancer cell vaccines can drive a robust polyclonal adaptive response. In this systematic review and meta-analysis, we investigated the safety and efficacy of these vaccines administered to patients with hematologic malignancies. Our primary outcomes of interest were safety and clinical response, with secondary outcomes including overall, disease-free and progression-free survival, relapse rate, correlative immune assays and health-quality related metrics. We identified 14 studies with 332 patients enrolled, of which 200 were ultimately treated with at least one dose of the vaccine. While we identified both patient-related and technical issues that might limit the feasibility of these trials, very few serious adverse events (AEs) were reported overall, with only 31.5% of patients suffering any AEs. Grade II or lower AE was observed in 10 (71.4%) of the 14 studies. Of the 3 (21.4%) reporting grade IV AEs, two observed the AE in one patient only, and one reported a 20% incidence of grade II-IV AEs. Of 58 evaluable patients, the complete response rate was 21% [95% CI, 10%-38%)] and overall response rate was 36% [95% CI, 24%-49%]. Analysis of individual patient level data (n=50) revealed a 5-year overall survival of 68.7% (SE 7.1%) and disease-free survival of 67.4% (SE 8.1%). Despite the clear safety and a signal towards efficacy, our review has identified several factors limiting administration of these vaccines, which should be considered when developing future clinical trials. PROSPERO registration number CRD42019140187 Disclosures Diallo: Virica Biotech: Other: Owner and Executive. Auer:Imugene: Other: Scientific Advisory Board. Kekre:Gilead: Consultancy, Honoraria; Novartis: Consultancy, Honoraria; Celgene: Consultancy, Honoraria.

Description: Hematopoiesis is extrinsically controlled by cells of the bone marrow microenvironment, including skeletal lineage cells. The identification and subsequent studies of distinct subpopulations of maturing skeletal cells is currently limited due to a lack of methods to isolate these cells. We found that murine Lineage-CD31-Sca-1-CD51+ cells can be divided into four subpopulations using flow cytometry, based on their expression of the platelet derived growth factor receptors ⍺ and β (PDGFR⍺ and PDGFRβ). The use of different skeletal lineage reporters confirmed the skeletal origin of the four populations. Multiplex immunohistochemistry studies revealed that all four populations were localized near the growth plate and trabecular bone and were rarely found near cortical bone regions or in central bone marrow. Functional studies revealed differences in their abundance, colony-forming unit-fibroblast capacity and potential to differentiate into mineralized osteoblasts or adipocytes in vitro. Furthermore, the four populations had distinct gene expression profiles and differential cell surface expression of leptin receptor (LEPR) and vascular cell adhesion molecule 1 (VCAM-1). Interestingly, we discovered that one of these four different skeletal populations showed the highest expression of genes involved in the extrinsic regulation of B lymphopoiesis. This cell population varied in abundance between distinct hematopoietically active skeletal sites, and significant differences in the proportions of B lymphocyte precursors were also observed in these distinct skeletal sites. It also supported pre-B lymphopoiesis in culture. Our method to isolate four distinct maturing skeletal populations will assist in elucidating the roles of distinct skeletal niche cells in regulating hematopoiesis and bone.

Description: Background Cytokine-release syndrome (CRS) is a life-threatening complication of haploidentical stem cell transplantation (haploSCT) occurring in the first few days after infusion of the stem cell graft prior to administration of post-transplant cyclophosphamide (PTCY). In the last few years, blockade of IL-6 receptor signaling with tocilizumab has emerged as an effective therapy for Grade 3-4 CRS. As IL-6 mediated signaling is a known regulator of the balance between regulatory T cells (Tregs) and other T cell subsets and has effects on NK cell function, questions remain regarding the effect of the blockade of IL-6 signaling on post-transplant immune cell recovery, engraftment, infection, acute graft-versus-host disease (aGVHD), and the graft-versus-tumor effect. We report on our experience with the use of tocilizumab to treat CRS, and we address the hypothesis that tocilizumab has no effect on the reconstitution of the post-haploSCT myeloid or lymphoid immune subsets. Methods A retrospective review of haploSCT patients with malignacies treated at the Dana-Farber Cancer Institute during the period of 2010-2019 was undertaken. Data included treatment with tocilizumab, cumulative incidence of NRM and relapse, day+30 and day+100 post-transplant chimerism, laboratory markers of viral and fungal infection, and immune reconstitution data at 1-month, 2-month, 3-month, and 6 months post-transplant. Kaplan-Meier analysis of overall survival (OS), including competing risk analysis of the cumulative incidence of relapse and non-relapse mortality (NRM) with the Fine-Gray model was preformed with EZR. Flow cytometry identification of relevant lymphoid populations was performed with a customized panel that included Treg (CD4+CD25+), Tcon (CD4+) and NK (CD3-CD56+) cells. Comparison of the lymphoid populations between the Tocilizumab-treated subgroup of haploSCT patients and the remaining patients was done with the Wilcoxon Mann-Whitney test. Results Out of 132 haploSCT patients, 19 received at least one dose of tocilizumab for the treatment of CRS out of whom one patient died from CRS. In tocilizumab-treated patients myeloid engraftment was 100% at day 30 post transplant. Tocilizumab use was not associated with any effect on lymphoid subset reconstitution at any time point post haploSCT (Figure 1A). Specifically, there was no difference in the reconstitution of NK cells (1-month NK: Mann-Whitney U = 120, p = 0.356; 3-month NK: Mann-Whitney U = 130, p = 0.528; 6-month NK: Mann-Whitney U = 110, p = 0.773), Treg (1-month Treg: Mann-Whitney U = 77, p = 0.412; 3-month Treg: Mann-Whitney U = 104, p = 0.203, 6-month Treg: Mann-Whitney U = 80, p = 0.186), or the Treg:Tcon ratio (1-month Treg:Tcon: Mann-Whitney U = 93, p = 0.835; 3-month Treg:Tcon: Mann-Whitney U = 97, p = 0.141; 6-month Treg:Tcon: Mann-Whitney U = 117, p = 0.959). The 1-year OS in the tocilizumab-treated patient subgroup was 62% (95% CI, 36%-80%) while in the rest it was 76% (95%CI, 67%-83%), with no significant difference between the two subgroups (p = 0.13). The 1-year cumulative incidence of relapse in the tocilizumab-treated subgroup was 19% (95% CI, 4%-42%) while in the rest it was 28% (95% CI, 20%-36%), with no difference between the subgroups (p=0.29). The 1-year NRM in the tocilizumab-treated subgroup was 33% (95% CI, 12%-55%) while in the rest it was 10% (95% CI, 5%-16%), and the difference between subgroups was statistically significant (p = 0.02). Fifty-five percent of patients treated with tocilizumab experienced reactivation of one or more of adenovirus, EBV, CMV or a fungal organism, with 50% of reactivations being CMV and 37% being fungal. Among the tocilizumab-treated patients, 42% experienced any aGVHD with only one patient experiencing Grade 3-4 aGVHD. Conclusions Tocilizumab use is not associated with any effect on post-transplant myeloid engraftment or reconstitution of the Treg, Tcon, and NK cell subsets. Although a significant proportion of tocilizumab-treated patients experienced reactivation of CMV or a fungal organism, the majority of these reactivations were not associated with any clinically significant symptoms. Treatment with tocilizumab was not associated with any significant effect on OS or disease relapse, but the tocilizumab-treated group had a higher NRM than the rest of the haploSCT patients. This association is consistent with prior studies correlating severe CRS with a high NRM, and merits further study. Disclosures Rambaldi: Equillium: Research Funding. Koreth:Amgen: Consultancy; Biolojic Design Inc: Consultancy; Regeneron: Other: Research Support; BMS: Other: Research Support; Cugene: Membership on an entity's Board of Directors or advisory committees; Miltenyi: Other: Research Support; Equillium: Consultancy; Moderna Therapeutics: Consultancy; Therakos: Membership on an entity's Board of Directors or advisory committees; EMD Serono: Consultancy; Clinigen: Other. Cutler:Medsenic: Consultancy, Membership on an entity's Board of Directors or advisory committees; Generon: Consultancy, Membership on an entity's Board of Directors or advisory committees; Mesoblast: 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; Kadmon: Consultancy, Membership on an entity's Board of Directors or advisory committees; Jazz: Consultancy, Membership on an entity's Board of Directors or advisory committees. Nikiforow:Kite: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees; Nkarta: Membership on an entity's Board of Directors or advisory committees. Wu:BionTech: Current equity holder in publicly-traded company; Pharmacyclics: Research Funding. Soiffer:Kiadis: Membership on an entity's Board of Directors or advisory committees; Be The Match/National Marrow Donor Program: Membership on an entity's Board of Directors or advisory committees; Celgene: Other; Juno: Other; Novartis: Consultancy; Alexion: Consultancy; VOR Biopharma: Consultancy; Mana Therapeutics: Consultancy; Precision Bioscience: Consultancy; Cugene: Consultancy; Rheos Therapeutics: Consultancy; Gilead: Consultancy. Ritz:TScan Therapeutics: Consultancy; Talaris Therapeutics: Consultancy; Rheos Medicines: Consultancy; Falcon Therapeutics: Consultancy; Avrobio: Consultancy; Kite Pharma: Research Funding; Equillium: Research Funding; Amgen: Research Funding; LifeVault Bio: Consultancy; Infinity Pharmaceuticals: Consultancy.