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Background: Sinusoidal obstruction syndrome (SOS) remains a significant, potentially lethal complication after allogeneic hematopoietic cell transplantation (allo-HCT). Although a liver biopsy is required to diagnose SOS accurately, it is not considered a mandatory evaluation due to its invasiveness. Therefore, the Seattle and Baltimore criteria with minor revisions have been widely used. However, the diagnostic accuracy of those criteria is insufficient. A noninvasive and more accurate diagnostic strategy is necessary. A number of studies have reported several candidate blood biomarkers for the diagnosis and prediction of SOS. However, which biomarkers or combination thereof are most useful for the diagnosis and prediction of SOS is unclear. We explored the best diagnostic and predictive biomarkers/combination among previously reported biomarkers for SOS using a stringent definition based on a liver biopsy. Methods: We performed this single-center prospective observational study in patients who received allo-HCT from April 2014 to February 2019. Seven biomarkers (PAI-1, P3P, ferritin, total bilirubin [T-bil], direct bilirubin [D-bil], brain natriuretic peptide [BNP], and protein C activity) were examined at pre-conditioning, at days 5 and 30, and at the onset of CTCAE grade ≥2 liver disorder after allo-HCT. We described how to diagnose definitive SOS (Fig. 1). A logistic regression (LR) model and the area under the receiver operating characteristic curves (AUC) were used to compare the seven biomarkers in the diagnosis and prediction of definitive SOS. The sensitivity, specificity, positive predictive value, negative predictive value, positive likelihood ratio, and negative likelihood ratio for the SOS diagnosis and prediction were also calculated by the best cut-off values, using the Youden index. Results of statistical tests with a p < 0.05 were considered significant. Results: A total of 180 patients were included. The median age was 48 (range: 16-68) years old. Forty-eight patients developed CTCAE grade ≥2 liver disorders. Of these, 10 were diagnosed with definitive SOS. The results of LR and AUC analyses of the SOS diagnosis and prediction are shown in the Table. PAI-1, P3P, ferritin, T-bil, and D-bil were found to be significant diagnostic markers for SOS. Among these, PAI-1 showed the highest AUC (0.85; 95% confidence interval [CI], 0.67-1.00). Furthermore, PAI-1, P3P, ferritin, T-bil, D-bil, and BNP were significant predictors for SOS. Among these biomarkers, P3P showed the highest AUC (0.82; 95% CI, 0.67-0.97). To perform further comparisons using multivariable models in SOS prediction, we first constructed a base model including the times of allo-HCT, disease status, and conditioning intensity. The AUC of the base model was 0.66 (95% CI, 0.48-0.84). After adding P3P to the base model, the AUC significantly improved to 0.88 (95% CI, 0.76-1.00) (p = 0.049). In the kinetics analysis of biomarkers, notably, PAI-1 and P3P increased over the peri-transplant period only in patients with definitive SOS (Fig. 2). In contrast, those values in patients with liver disorders other than SOS or without liver disorders did not show significant kinetic characteristics in the allo-HCT period. Discussion: SOS is attributed to toxic injury of the sinusoidal endothelial cells. PAI-1 is a known endothelial factor, released when the endothelial cells are damaged. This could be why PAI-1 was considered useful for the SOS diagnosis. P3P has been shown to be a sensitive biomarker for liver fibrosis. Furthermore, fibrous alterations in the hepatic remodeling process are well-known significant features for patients with SOS. Thus, liver fibrosis may pathophysiologically be a risk factor for SOS, and P3P may allow clinicians to detect SOS-high-risk patients with high accuracy, even at the time of allo-HCT when preclinical liver fibrosis can exist. Conclusion: We demonstrated that PAI-1 and P3P were the most useful biomarkers for the diagnosis and prediction of SOS, respectively. Figure 1 Figure 1. Disclosures Okamura: NIPPON SHINYAKU CO.,LTD.: Honoraria. Koh: AstraZeneca: Research Funding; Sumitomo Dainippon Pharma Co., Ltd.: Honoraria; MSD: Honoraria; Takeda Pharmaceutical Company Limited.: Honoraria, Research Funding; Novartis: Honoraria; NIHON PHARMACEUTICAL CO., LTD: Honoraria; Asahi Kasei Corporation:: Research Funding; IQVIA Services Japan K.K.:: Research Funding. Takakuwa: Takeda Pharmaceutical Company Limited.: Honoraria; Bristol-Myers Squibb Comapany: Honoraria; Sanofi K.K.: Honoraria; Celgene Corporation: Honoraria; Janssen Pharmaceutical K.K.: Honoraria; Novartis: Honoraria; AbbVie GK: Research Funding; Celgene Corporation: Research Funding. Nakamae: Novartis: Honoraria. Nishimoto: Otsuka Pharmaceutical Co., Ltd.: Honoraria; CSL Behring: Honoraria; Kyowa Kirin Co., Ltd: Honoraria; "Bayer Yakuhin, Ltd ": Research Funding; Janssen Pharmaceutical K.K.: Research Funding. Nakashima: Amgen Astellas BioPharma K.K.: Honoraria; Amgen Inc: Honoraria; Novartis: Honoraria, Research Funding; JCR Pharmaceuticals Co., Ltd.: Honoraria; Pfizer Japan Inc.: Honoraria; Eisai Co., Ltd: Honoraria; Chugai Pharmaceutical Co., Ltd.: Honoraria; SymBio Pharmaceuticals Limited.: Honoraria, Research Funding; Astellas Pharma Inc.: Research Funding; Celgene Corporation: Research Funding; AbbVie GK: Research Funding. Nakamae: Astellas Pharma Inc.: Honoraria; Otsuka Pharmaceutical Co., Ltd: Honoraria; ONO PHARMACEUTICAL CO., LTD.: Honoraria; Simon-Kucher & Partners: Honoraria; Sumitomo Dainippon Pharma Co., Ltd.: Honoraria; Takeda Pharmaceutical Company Limited.: Honoraria; Novartis: Honoraria, Research Funding; Pfizer Japan Inc.: Honoraria; Bristol-Myers Squibb Company: Honoraria, Research Funding; Alexion: Research Funding; PPD-SNBL K.K: Research Funding; CMIC HOLDINGS Co., Ltd: Research Funding. Hino: Novartis: Honoraria, Research Funding; NIPPON SHINYAKU CO.,LTD.: Honoraria; Japan Blood Products Organization: Honoraria, Research Funding; Chugai Pharmaceutical Co., Ltd.: Honoraria; Takeda Pharmaceutical Company Limited.: Honoraria, Research Funding; Celgene Corporation: Honoraria, Research Funding; Sanofi: Honoraria; Otsuka Pharmaceutical Co., Ltd.: Honoraria, Research Funding; AstraZeneca: Honoraria; Astellas Pharma Inc.: Honoraria; MSD: Honoraria, Research Funding; CSL Behring: Honoraria; ONO PHARMACEUTICAL CO., LTD.: Honoraria, Research Funding; Meiji Seika Pharma Co., Ltd.: Honoraria; Eisai Co., Ltd: Honoraria, Research Funding; Kyowa Kirin Co., Ltd: Honoraria, Research Funding; Pfizer Japan Inc.: Honoraria, Research Funding; Bristol-Myers Squibb Comapany: Honoraria; Janssen Pharmaceutical: Honoraria; JCR Pharmaceuticals Co., Ltd.: Research Funding; ARKRAY: Research Funding; Asahi Kasei Corporation:: Research Funding; Abbott: Research Funding; TEIJIN PHARMA LIMITED.: Research Funding; SEKISUI MEDICAL CO., LTD.: Research Funding; Sumitomo Dainippon Pharma Co., Ltd.: Research Funding; TAIHO PHARMACEUTICAL CO., LTD.: Research Funding; DAIICHI SANKYO COMPANY, LIMITED.: Research Funding; TOSOH CORPORATION: Research Funding.

Background. Inflammatory tumor microenvironment leads to T cell exhaustion in multiple myeloma leading to treatment failure and relapse. Specifically, T cell based therapies including bispecific antibodies and chimeric antigen receptor (CAR) T cell are associated with the additional side effects of non-specific T cell activation and cytokine release syndrome. Adoptive therapy with allogeneic cord blood (CB) T regulatory (Treg) cell therapy has been shown to be safe with clinical efficacy in a wide range of diseases including graft vs. host disease (GvHD), inflammatory bone marrow failures and COVID-19 induced acute respiratory distress syndrome. Furthermore, combination of Tregs with donor lymphocyte infusion (DLI) has led to resolution of leukemia relapse without GvHD flare up. We hypothesize that co-administration of Tregs with adoptive T cell based therapy will improve myeloma outcomes. Methods. 3x106 GFP-labeled MM.1S cells were injected into NSG mice followed by 5x106 CD3+ T conventional (Tcon) cells on day 14. In a subset of the Tcon treated mice, 1x107 CB Treg cells were injected on day 47, 54 and 61. Mice were followed every other day for weight and GvHD score. Non-invasive bioluminescent imaging (BLI) was performed serially. Weekly blood draw was performed for cell analysis and cytokine assays. At the time of euthanasia, blood, spleen and bone marrow were harvested for histopathology and flow analysis. In a subsequent experiment, intra-peritoneal injection of the bi-specific antibody against CD3 and BCMA (BCMA-BiTE) was administered in the xenogenic myeloma model in the presence or absence of CB Treg cells. Pan T cells were injected into all mice to facilitate the anti-tumor action of BiTE. Results. Both Tcon and Tcon+Treg recipients maintained their body weight compared to myeloma alone or myeloma + Treg arm (Figure A). All mice showed evidence of tumor growth by day 20 (Figure A). Widespread MM.1S cell growth in the myeloma only mice at day 27 was demonstrated by BLI whereas no measurable tumor growth was evident in Tcon recipients or Tcon+Treg recipients. By day 69, Tcon only mice were significantly increased tumor growth compared to Tcon+Treg recipients (Figure B). While circulating multiple myeloma cells were detected in myeloma alone and myeloma+Treg arm, no such evidence was detectable in the Tcon or Tcon+Treg recipients. However, upon euthanasia, extramedullary relapse of myeloma as retroperitoneal mass was detected in Tcon recipient (Figure C). Addition of Treg + BiTE led to a similar degree of tumor control compared to BiTE alone treated mice, however, a significant weight loss was observed in this arm (Figure D) with a corresponding high GvHD score (Figure E). Furthermore, addition of CB Treg cells led to decrease of T cell exhaustion phenotypic markers (data not shown). Conclusion. We are the first to show that CB Treg cells can be administered in combination with the T-cell based immunotherapies directed against myeloma. Such a strategy should be examined in the clinical setting. Figure Disclosures Nishimoto: Bayer Yakuhin, Ltd:: Research Funding; Janssen Pharmaceutical K.K.:: Research Funding. Sadeghi:Cellenkos Inc.: Current Employment. Shah:GSK, Amgen, Indapta Therapeutics, Sanofi, BMS, CareDx, Kite, Karyopharm: Consultancy; BMS, Janssen, Bluebird Bio, Sutro Biopharma, Teneobio, Poseida, Nektar: Research Funding. Patel:Nektar: Consultancy, Research Funding; Celgene: Consultancy, Research Funding; Cellectis: Research Funding; Takeda: Consultancy, Research Funding; Janssen: Consultancy, Research Funding; Oncopeptides: Consultancy; Poseida: Research Funding; Precision Biosciences: Research Funding; Bristol Myers Squibb: Consultancy, Research Funding. Parmar:Cellenkos Inc.: Current equity holder in private company, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties, Research Funding.

Background.As a T cell driven process where release of inflammatory cytokines as a result of the proliferation and on target cell kill by chimeric antigen receptor (CAR)-T cells, cytokine release syndrome (CRS) can be potentially targeted by adoptive therapy with T regulatory (Treg) cells. Specifically, allogeneic cord blood (CB) derived Treg cells have now shown safety and efficacy in graft vs host disease (GVHD), we hypothesized that CB Treg cell therapy can be exploited for treatment of CRS. Method.Xenogenic lymphoma model was created using NSG mice where 0.3x106 GFP-labeled Raji cells were injected on day 0 in all mice followed by 0.3x106 cells of i) mock-CAR T, ii) no CART, ii) CD19-CAR T cells on day +5. Additional injections of 1x107 CB Treg cells on day +11, +18, +25 were added to the no CAR T arm and the CD19-CAR T arm such that there were 3 mice per arm. Mice were followed for weight, GVHD score and survival. Non-invasive bioluminescence was used to perform serial imaging to evaluate the tumor burden. Serial blood was drawn for cell analysis and cytokine assay. Result. As shown in figure A, in vivo proliferation of GFP-labeled Raji cells was evident in all mice day by day +4. CD19-CAR T but not the mock-CAR T cells decreased the tumor burden at day+11. However, at day +14 all mice including CD19-CAR T cell recipients showed progression whereas CD19-CAR T+CB Treg cell recipient showed no evidence of bioluminescence. A superior survival in the CD19-CAR T+CB Treg cells recipients was evident when compared to other treatment arms (Table A). At the time of euthanasia, different organs were evaluated for the detection of the CD19-CART cells and were recovered only in the CD19-CART+CB Treg cells recipients (Table B) . The CD19-CAR T recipients showed an increase in the inflammatory cytokines on day +16 PB samples including IFN-gamma (Figure B) and TNF-alpha (Figure C) which were decreased in the CD19-CAR T + CB Treg arm. Furthermore, a reciprocal increase of the anti-inflammatory cytokine IL-1RA was observed in the CD19-CAR T + CB Treg arm compared to the CD19-CAR T alone (Figure D). Conclusion. The addition of CB Treg cells to CD19-CAR T cells in a xenogenic lymphoma model led to dampening of the cytokine storm and improved on target efficacy of CAR T cells. This combination should be examined in clinical setting. Disclosures Sadeghi: Cellenkos Inc.:Current Employment.Nastoupil:Genentech, Inc.:Honoraria, Research Funding;Karus Therapeutics:Research Funding;Bayer:Honoraria;Gamida Cell:Honoraria;Gilead/KITE:Honoraria;Novartis:Honoraria, Research Funding;Merck:Research Funding;TG Therapeutics:Honoraria, Research Funding;LAM Therapeutics:Research Funding;Janssen:Honoraria, Research Funding;Pfizer:Honoraria, Research Funding;Celgene:Honoraria, Research Funding.Patel:Oncopeptides:Consultancy;Janssen:Consultancy, Research Funding;Precision Biosciences:Research Funding;Takeda:Consultancy, Research Funding;Nektar:Consultancy, Research Funding;Celgene:Consultancy, Research Funding;Bristol Myers Squibb:Consultancy, Research Funding;Poseida:Research Funding;Cellectis:Research Funding.Parmar:Cellenkos Inc.:Current equity holder in private company, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties, Research Funding.

Background: Recent approval of ruxolitinib (rux) for steroid refractory graft versus host disease (GvHD) has revolutionized the field and provided tremendous choice for the patients. However, the side effects including thrombocytopenia leads to dug discontinuation and intolerance. We have previously shown that adoptive therapy with cord blood (CB) derived T regulatory (Treg) cells can prevent and treat GvHD. We hypothesized that the addition of CB Treg therapy to rux based therapy can augment overall efficacy. Methods: CellTrace Violet suppression assay was performed to evaluate the suppressor function of CB Treg cells in the presence or absence of rux. Xenogenic GvHD mouse model was utilized where the NSG mice underwent sublethal irradiation on day -1 followed by injection of 1x107 donor peripheral blood (PB) mononuclear cells (MNCs) on day 0. Oral rux at 1 mg daily was fed continuously to the mice in the presence or absence of 1x107 CB Treg cells, tagged with CellTrace Violet dye, administered on days +4, +7, +11, +18. Mice were followed every other day for weight, GvHD score and survival. Serial blood draws were performed to analyze for cell compartment and cytokine assays. Results: We examine whether the addition of rux impacts the suppressor function of CB Treg cells. Varying concentration of rux including 0.01, 0.05, 0.1 and 0.5 µM were added at 24, 48 and 96 hours of the cell suppression assay. The addition of rux 0.05 µM at 48 hours of the cell suppression culture led to a restoration of poor cell function (Figure A). Lowest GVHD score was reported in the rux+CB Treg combination arms at day +14 when compared to rux alone or CB Treg alone arm which (Figure B) translated into a superior survival in the rux +CB Treg arm (Figure C). Furthermore, an increase in the hemoglobin level (Figure D) and the platelet count (Figure E) was demonstrated in the rux+CB Treg arm. Addition of rux led to longer persistence of the injected CB Treg cells on day 14 (data not shown) which correlated with the increase in the plasma level of the pro-Treg cell signaling markers including IL-7 (Figure F) and IL-15 (Figure G). A decrease in the IL-4 production supported the increased Treg cell function (Figure H). A synergistic suppression of inflammatory cytokines including IL-17 (Figure I) and IL1A (Figure J) was evident in the rux+CB Treg arm. Conclusion: The combination of CB Tregs with ruxolitinib leads to improved overall survival, decreased inflammatory cytokines and improved hematologic parameters. Such combination should be explored in a clinical setting Figure Disclosures Sadeghi: Cellenkos Inc.: Current Employment. Parmar:Cellenkos Inc.: Current equity holder in private company, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties, Research Funding.

Introduction: Regulatory T cells (Tregs) are potent immunosuppressors and are being developed as adoptive immunotherapy for inflammatory disorders and autoimmune diseases. Specifically, cord blood (CB) Tregs are emerging as a promising treatment for graft vs. host disease (GVHD) as well as immune mediated bone marrow failure disorders including aplastic anemia, hypoplastic myelodysplasia and primary myelofibrosis. We and others have shown that when compared to peripheral blood (PB), CB Tregs have a higher expression of Helios, a marker of thymic Tregs; exert superior suppression on proliferating conventional T cells and do not secrete inflammatory IL-17 or express RORүt under stressful conditions. Such a stable suppressor profile coupled with their ready availability as an off-the-shelf product positions CB Tregs to be a very attractive therapeutic agent. Since multiple myeloma, a plasma cell clonal malignancy, exists in an inflammatory microenvironment of hematopoietic and non-hematopoietic cells which is likely related to disease progression, we hypothesized that adoptive therapy with CB Tregs may block myeloma progression by exerting their anti-inflammatory function. Methods: We used the NOD-SCID IL2rγnull (NSG) mice to first establish the myeloma tumor model, where mice were injected intravenously via tail vein with 3 x 106 Firefly luciferase labeled MM1S cells. For generating CB Tregs for adoptive therapy, Treg cell enrichment was performed from the whole CB unit using CD25+ magnetic beads and LS column (MIltenyl) followed by continuous culture in the presence of CD3/28 T-cell activator beads, and human recombinant interleukin-2 for 14 days. Expanded CB Treg phenotype was confirmed using flow cytometry analysis and the in-vitro suppressive capacity was assessed by CellTrace Violet Cell Proliferation assay. The mice were injected intravenously via tail vein with Firefly luciferase labeled MM1S cells on day 0 with or without 10 x 106 ex-vivo expanded CB Treg cells on day -1. We monitored the progression of MM1S cells by in vivo bioluminescence imaging (BLI) using the IVIS imaging system (Xenogen) 10 minutes after intraperitoneal injection of D-luciferin. Imaging data were analyzed and quantified with Living Image Software (Xenogen). We also assessed the weight and survival as well as the plasma cytokines levels. At the time of euthanasia, organs were harvested and analyzed for myeloma burden by using immunohistochemistry as well as flow analysis. Results: The expanded CB Tregs showed a consistent phenotype of CD4+25+127-FoxP3high and more than 80% suppression of the proliferating conventional T cells (Tcons). The progression of MM1S cells in the mice injected with CB Treg (n=9) was significantly delayed as shown in figure 1A, where minimal evidence of myeloma cells is visualized on day 31 compared to widespread tumor in the control arm (n=9). CB Treg recipients preserved their weight for a longer time (Figure 1B) and had improved overall survival (p=0.039) (Figure 1C). The prevention of development of myeloma by CB Tregs correlated with the lower levels of the inflammatory cytokine, interleukin-6 (IL-6) (murine) especially on day 35 post myeloma inoculation (Figure 1D). The circulating myeloma cells in the CB Treg recipients were significantly lower as compared to control mice. Upon euthanasia on day 25 post inoculation, myeloma cells were barely detectable in bone marrow and spleen in the CB Treg recipients as compared to large tumor burden in the control arm (Figure 1E). Conclusions: Our results demonstrate that ex-vivo expanded CB Treg cells prevent the growth of myeloma cells in a xenogenic model via suppression of inflammatory cytokines such as IL-6. These data provide additional insight to the underpinnings of myeloma progression and may contribute to the development of the novel immunotherapies in the future. Figure 1 Disclosures Shah: University of California, San Francisco: Employment; Genentech, Seattle Genetics, Oncopeptides, Karoypharm, Surface Oncology, Precision biosciences GSK, Nektar, Amgen, Indapta Therapeutics, Sanofi: Membership on an entity's Board of Directors or advisory committees; Indapta Therapeutics: Equity Ownership; Celgene, Janssen, Bluebird Bio, Sutro Biopharma: Research Funding; Poseida: Research Funding; Bristol-Myers Squibb: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Amgen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Nkarta: Consultancy, Membership on an entity's Board of Directors or advisory committees; Kite: Consultancy, Membership on an entity's Board of Directors or advisory committees; Teneobio: Consultancy, Membership on an entity's Board of Directors or advisory committees. Orlowski:Poseida Therapeutics, Inc.: Research Funding. Parmar:Cellenkos Inc.: Equity Ownership, Membership on an entity's Board of Directors or advisory committees, Research Funding.

Background: Regulatory T cells (Treg), a well defined suppressor cell population with the phenotype of CD4+CD25+CD127- FoxP3+ are emerging as a promising adoptive therapy for a diverse subset of autoimmune diseases and inflammatory disorders. Specificlaly, cord blood (CB) Tregs have been shown to be superior to peripheral blood (PB) Tregs in their function and stability. Here, we define a novel subset of CB Tregs CD4+CD8+CD25+CD127- FoxP3+ that is not very well defined in the PB population and explore its' differentiation characteristics. Method: Tregs were isolated from CB or PB as described previously and cultured in the presence of CD3/28 beads and IL-2. On the day of harvest, cells were further sorted for CD8+ cell population and labelled as CD8+CD4+ (double positive CB Tregs: DP) and the leftover fraction as CD8-CD4+ (single positive CB Tregs: SP). Cells fractions were analyzed using flow cytometry and for cytokine assay, cells were activated (5 hours) with 1X Cell Stimulation Cocktail with Golgi inhibitors and stained for IFN-γ, IL-4, IL-17, IL-10 or TGFβ1 as per manufacturer's instructions. Additional cytokine assay was performed on the culture supernatants. DNA methylation assay was performed for the TSDR region as per manufacturer's instructions. Single cell RNAseq was performed at Albert Einstein Hospital and analyzed at Methodist Hospital. A threshold for original counts were applied to all four conditions, i.e. only transcripts with original counts>10 in all four. This step reduced the number of genes from 34626 to 16628; subsequently stringent cutoffs pairs showed two sets of genes- 1) Fold change>1.5, p-value Result: We cultured the Tregs isolated from CB or PB for 14 days and no evidence of a DP Tregs (0) was seen in PB as compared to a clearly defined DP Treg (8-26%) population in CB cultures. No differences were seen between the SP and DP CB Tregs in terms of the markers for mechanisms of suppression (FoxP3,Helios,CD39 ), homing (PSGL1, CLA, CD62L, CD49d), TGF-beta signaling (LAP, TGF-beta, GARP) and T cell signaling (LAG23, PD1, Icos, Tim3, CTLA-4, GITR). DP CBTregs consisted of a significantly higher expression of CCR4hiCXCR3hiCD95hipopulation. DP CB Tregs demonstrated a significantly higher IL-10 secretion compared to SP CB Tregs (Fig 1A) which correlated with the level of IL-10 secreted in the cell cuture supernatant (data not shown). While the degree of suppression of the proliferating conventional T cells was similar by the DP and SP CB Tregs (data not shown), a significantly higher demethylation of FoxP3 promoter and first intron region was observed in the DP vs SP CB Treg population (n=3) (Fig 1B). A total of 337 pathways were identified from Up-406 gene set, 80 of these pathways had enrichment p-value Conclusion: We have identified a novel double positive CD4+CD8+ CB Treg population. Additional experiments for evaluating suppressor mechanism in addition to IL-10 secretion are ongoing. Figure 1 Disclosures Verma: Stelexis: Equity Ownership, Honoraria; Acceleron: Honoraria; Celgene: Honoraria; BMS: Research Funding; Janssen: Research Funding. Iyer:Genentech/Roche: Research Funding; Incyte: Research Funding; Seattle Genetics, Inc.: Research Funding; Novartis: Research Funding; Arog: Research Funding; Bristol-Myers Squibb: Research Funding. Parmar:Cellenkos Inc.: Equity Ownership, Membership on an entity's Board of Directors or advisory committees, Research Funding.

Background: Aplastic anemia is an autoimmune disease of the bone marrow (BM) characterized by defective and decreased regulatory T cells (Tregs) which results in unchecked cytotoxic T cell mediated bone marrow suppression [1]. In a xenogeneic model of induce BM aplasia, adoptive therapy with cord blood (CB) Tregs reverses such a defect (Fig 1A). Furthermore, as compared to peripheral blood (PB), CB Tregs show a higher expression of Helios, a marker of thymic derived Tregs (Fig 1B) and CB Tregs exert a superior suppression of proliferating conventional T-cells in CFSE assay (Fig 1C). In a xenogeneic mouse model of GVHD, CB Tregs can exert suppression across HLA barrier resulting in survival benefit (Fig 1D); and in another xenogenic lupus model, a single dose of CB Tregs results in significant decrease in circulating effector T cells (Fig 1E) up to 8 weeks. Furthermore, under stressful conditions of continued culture in the presence of inflammatory cytokines including IL15 and IL23, CB Tregs do not secrete IL-17 or express RORγt, a concern of plasticity that plagues PB Tregs (Fig 1F). In fact, CB Tregs increase their secretion of the suppressor cytokine, IL-10 in response to inflammatory stress, which supports our hypothesis, that CB Tregs based adoptive therapy can have wide application and can be used to treat inflammatory disorders. Therefore, we hypothesized that adoptive therapy with CB Tregs can be utilized as treatment for the inflammatory bone marrow failure (BMF) disorders including aplastic anemia, hypoplastic myelodysplasia and primary myelofibrosis. Study Design and Methods: We have now launched a phase I clinical trial examining the role of single infusion of CK0801, an allogeneic, fresh CB Treg product, utilizing novel process development that consist of well-defined qualification criteria for the starting material (cord blood units), parameters for manufacturing and culture-expansion; and well-defined analytic testing and lot release criteria, for the treatment of BMF, where 3 doses are examined: i) dose level I: 1x106 cells/kg; ii) dose level II: 3x106 cells/kg and iii) dose level III: 10x106 cells/kg (NCT03773393). The study follows 3+3 phase I design where 3 patients will be treated at dose level I. If no DLT is observed, then the dose will be escalated to dose level II and if no DLT is observed, then the dose will be escalated to dose level III. If 1 DLT is observed at a dose level, then 3 additional patients will be treated at that level. If no additional DLTs, then that dose level will be defined as MTD. If ≥2DLTs are observed at dose level II or III, then prior dose level is defined as MTD. If ≥2DLTs at dose level I, then DSMB will review and evaluate for study continuation. MTD will be decided when 6 patients are treated at a dose level with < 2 DLTs. The eligibility criteria include: i) diagnosis of aplastic anemia, myelodysplastic syndrome or myelofibrosis, ii) Age > 18 years, iii) cord blood unit matched at HLA 3 out of 6 with the patient for generation of CK0801. The primary endpoint includes dose limiting toxicity (DLT) as defined by i) severe (grade 3 or 4) infusion toxicity within 24 hours; ii) regimen related death within 30 days or iii) severe (grade 3 or 4) cytokine release syndrome within 30 days. The secondary endpoints include i) disease-specific response including complete remission, transfusion independence and hematologic improvement and ii) duration of response. The exploratory endpoints include assessment of PB and BM immune reconstitution and inflammatory cytokines at baseline and scheduled follow ups of Days 0, +1, +3, +7, +14, +21, +30, +60, +90, +180 and +365 in the post-treatment setting. These studies will include T cell compartment analysis: Treg, Effector T cells, T-cell anti-viral activity. Serum will be analyzed for inflammatory cytokines: IL1, IL2, IL4, IL6, IL7, IL8, IL10, IL17, IFN-gamma, ST2, REG3a, OPN, Follistatin, Elafin, TGF-beta. Optional exploratory cytokines: SCF, G-CSF, GM-CSF, HGF, VEGF, SDF1a, MCP1, MCP2, TARC, MIP3a, TECK, CTACK, CCL28, FGF, PDGF, EGF, TGF-α, TLR. The first patient is already consented with a planned total of 9 patients. References: 1. Kordasti S, Costantini B, Seidl T, et al., Deep phenotyping of Tregs identifies an immune signature for idiopathic aplastic anemia and predicts response to treatment. 2016 Sep 1;128(9):1193-205 Figure 1 Disclosures Kadia: AbbVie: Consultancy, Research Funding; Amgen: Membership on an entity's Board of Directors or advisory committees, Research Funding; BMS: Research Funding; Bioline RX: Research Funding; Celgene: Research Funding; Jazz: Membership on an entity's Board of Directors or advisory committees, Research Funding; Genentech: Membership on an entity's Board of Directors or advisory committees; Pfizer: Membership on an entity's Board of Directors or advisory committees, Research Funding; Pharmacyclics: Membership on an entity's Board of Directors or advisory committees; Takeda: Membership on an entity's Board of Directors or advisory committees. DiNardo:abbvie: Consultancy, Honoraria; agios: Consultancy, Honoraria; celgene: Consultancy, Honoraria; daiichi sankyo: Honoraria; jazz: Honoraria; medimmune: Honoraria; syros: Honoraria; notable labs: Membership on an entity's Board of Directors or advisory committees. Parmar:Cellenkos Inc.: Equity Ownership, Membership on an entity's Board of Directors or advisory committees, Research Funding. Iyer:Rhizen: Research Funding; Seattle Genetics: Research Funding; Trillium Therapeutics: Research Funding; Merck: Research Funding; Spectrum: Research Funding. Hari:Celgene: Consultancy, Honoraria, Research Funding; Takeda: Consultancy, Honoraria, Research Funding; BMS: Consultancy, Research Funding; Janssen: Consultancy, Honoraria; Kite: Consultancy, Honoraria; Amgen: Research Funding; Spectrum: Consultancy, Research Funding; Sanofi: Honoraria, Research Funding; Cell Vault: Equity Ownership; AbbVie: Consultancy, Honoraria. Jabbour:BMS: Consultancy, Research Funding; Takeda: Consultancy, Research Funding; Amgen: Consultancy, Research Funding; AbbVie: Consultancy, Research Funding; Adaptive: Consultancy, Research Funding; Pfizer: Consultancy, Research Funding; Cyclacel LTD: Research Funding. Borthakur:Novartis: Research Funding; Xbiotech USA: Research Funding; Oncoceutics: Research Funding; Agensys: Research Funding; Janssen: Research Funding; Incyte: Research Funding; AbbVie: Research Funding; BMS: Research Funding; AstraZeneca: Research Funding; Bayer Healthcare AG: Research Funding; Eisai: Research Funding; Strategia Therapeutics: Research Funding; BioTheryX: Membership on an entity's Board of Directors or advisory committees; Argenx: Membership on an entity's Board of Directors or advisory committees; FTC Therapeutics: Membership on an entity's Board of Directors or advisory committees; Merck: Research Funding; Arvinas: Research Funding; Polaris: Research Funding; BioLine Rx: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Tetralogic Pharmaceuticals: Research Funding; PTC Therapeutics: Consultancy; Oncoceutics, Inc.: Research Funding; Eli Lilly and Co.: Research Funding; GSK: Research Funding; NKarta: Consultancy; Cantargia AB: Research Funding; Cyclacel: Research Funding. Verstovsek:Incyte: Research Funding; Roche: Research Funding; NS Pharma: Research Funding; Celgene: Consultancy, Research Funding; Gilead: Research Funding; Promedior: Research Funding; CTI BioPharma Corp: Research Funding; Genetech: Research Funding; Blueprint Medicines Corp: Research Funding; Novartis: Consultancy, Research Funding; Sierra Oncology: Research Funding; Pharma Essentia: Research Funding; Astrazeneca: Research Funding; Ital Pharma: Research Funding; Protaganist Therapeutics: Research Funding; Constellation: Consultancy; Pragmatist: Consultancy.

Background: Central nervous system (CNS) complications after allogeneic hematopoietic cell transplantation (allo-HCT) can be fatal. Although numerous studies have reported risk factors for CNS complications after allo-HCT, most defined CNS complication events as a composite endpoint, for example, composed of cerebrovascular disease, infection, posterior reversible encephalopathy syndrome (PRES), and metabolic encephalopathy. For a more precise and targeted approach, risk factor analyses for each individual CNS event are needed. Few studies have reported risk factor analyses for individual CNS complications. They have included analyses for cerebrovascular disease, viral encephalitis, HHV6 encephalitis, and noninfectious neurologic complications. To our knowledge, no pretransplant risk factor analysis for calcineurin inhibitor-induced encephalopathy (CNIE) and limbic encephalitis (LE) has yet been reported. Method: We retrospectively examined consecutive patients who underwent allo-HCT at our institute between January 2005 and November 2017. CNIE was defined as a patient who exhibited clinical symptoms of PRES or neurological manifestations of thrombotic microangiopathy during cyclosporin A (CSA) or tacrolimus (TAC) administration. LE was defined as a patient who displayed selective medial temporal lobe involvement in brain MRIs. As a rule, HHV-6 DNA polymerase chain reaction was performed on cerebrospinal fluid (CSF) for LE cases. Results: A total of 485 patients between 16- and 69-years-old (median, 46 years) were eligible for this study. They received myeloablative (n = 292) or reduced-intensity conditioning (n = 193) for allo-HCT. Diagnoses included AML/ALL (n = 292), MDS (n = 59), NHL (n = 93), and others (n = 41). HLA allele typing was performed at HLA-A, -B, -C, and -DRB1. Donor sources consisted of HLA-matched or -one allele mismatched sibling peripheral blood (PB) or bone marrow (BM) (n = 98)/HLA matched unrelated donors (n = 93) (hereafter referred to as HLA-matched donors), HLA-mismatched unrelated BM (uBM; n = 36), umbilical cord blood (uCB; n = 110), haploidentical PB (n = 118), and allele unknown uBM (n = 30). A total of 33 CNS events were identified: 11 CNIE (33 %), 14 LE (42 %), 3 transverse myelitis (9.0 %), 2 drug encephalopathy (6.0 %), 1 aseptic meningitis (3.0 %), 1 fungal brain abscess (3.0 %), and 1 acute epidural hematoma (3.0 %). The median follow-up time among the survivors was 1836 days (range, 45-4860 days) after allo-HCT. By landmark time analysis, the prognosis of those with any CNS complications within 30 days was significantly worse than those who did not (1-year OS, 37.5 % vs. 55.4 %, Log-rank p = 0.011). A multivariable time-dependent Cox model revealed that CNS complications were an independent prognostic factor for overall survival (Hazard ratio (HR) 4.49, 95 % CI, 2.30-8.76, p < 0.001), adjusted for age and disease risk index. CNIE cases included 6 CSA-induced and 3 TAC-induced cases, of which 4 patients (44 %) were alive. In the multivariable Cox models, MDS (HR 9.4 (vs. AML/ALL), 95 % CI, 2.2-40, p = 0.002) and HLA-mismatched uBM (HR 16 (vs. HLA-matched donors), 95 % CI, 3.0-81, p = 0.001) were significantly associated with CNIE development. LE included 7 HHV6-negative (2 alive), 5 HHV6-positve (1 alive), and 2 unknown cases (1 alive). Eleven of these patients were treated by methylprednisolone pulse therapy; all patients responded partially or effectively and four patients (36 %) achieved complete remission. In the multivariable Cox models, HLA-mismatched uBM (HR 7.5 (vs. HLA-matched donors), 95 % CI, 1.2-45, p = 0.028) was significantly associated with LE development. Conclusion: CNS complications were found to be an independent risk factor for OS after allo-HCT, as reported previously. MDS and HLA-mismatched uBM were risk factors for CNIE; the former may be partly explained by the fact that a subset of MDS may be predisposed to vascular endothelial damage (e.g. vasculitis), since CNIE may be triggered by endothelial dysfunction caused by CNI. Moreover, HLA-mismatched uBM was a risk factor for LE. Experimental data revealed that major histocompatibility complex class 1 protein was expressed in hippocampal neurons; thus, the limbic system may be targeted by alloimmune reactions more frequently in HLA-mismatched uBM settings, regardless of whether HHV-6 reactivation occurs. Disclosures Koh: Alexion: Honoraria; DAIICHI SANKYO COMPANY: Honoraria; MSD K.K: Honoraria; Takeda Pharmaceutical: Honoraria, Research Funding; NIHON PHARMACEUTICAL: Honoraria; Takeda Science Foundation: Research Funding; Chugai Pharmaceutical: Research Funding; Amgen Astellas BioPharma: Research Funding; Asahi Kasei Corporation: Research Funding; IQVIA Services Japan: Research Funding. Okamura:Eisai Co., Ltd: Honoraria; MSD K.K: Honoraria. Shiro:Bristol-Myers Squibb: Honoraria. Nanno:Eisai Co., Ltd.: Honoraria; MSD K.K: Honoraria; Chugai Pharmaceutical Co., Ltd.: Honoraria. Nakamae:Chugai Pharmaceutical Co., Ltd.: Honoraria, Membership on an entity's Board of Directors or advisory committees; Pfizer Japan Inc.: Honoraria, Membership on an entity's Board of Directors or advisory committees; Astellas Pharma Inc.: Research Funding; Alexion: Honoraria; Bristol-Myers Squibb: Honoraria; Celgene: Honoraria; Janssen: Honoraria; Japan Blood Products Organization: Honoraria; Kyowa-Hakko Kirin Co.,Ltd: Honoraria; Nippon Shinyaku: Honoraria; Novartis: Honoraria, Research Funding; Otsuka Pharmaceutical: Honoraria, Membership on an entity's Board of Directors or advisory committees; Shire Japan KK.: Honoraria; Takeda Pharmaceutical Co., Ltd.: Honoraria. Nakashima:Novartis: Honoraria; Kyowa-Hakko Kirin Co.,Ltd: Honoraria; Eisai Co.,Ltd: Honoraria, Research Funding; Celgene Corporation: Research Funding; Amgen Astellas BioPharma K.K.: Honoraria, Research Funding; AbbVie Inc.: Research Funding; Astellas Pharma Inc.: Research Funding; Bristol-Myers Squibb: Honoraria. Nakane:Kyowa-Hakko Kirin Co.,Ltd: Honoraria; Chugai Pharmaceutical Co., Ltd.: Honoraria; DAIICHI SANKYO COMPANY, LIMITED.,: Honoraria; Mundipharma K.K.: Honoraria; Novartis: Honoraria; Janssen Pharmaceutical K.K.: Research Funding; MSD K. K,: Research Funding; Pfizer Japan Inc.: Research Funding; Bayer Yakuhin, Ltd: Research Funding. Hino:MSD: Honoraria, Research Funding; Mundipharma: Honoraria; Nihon Pharmaceutical Co., Ltd: Research Funding; Sumitomo Dainippon Parma: Honoraria, Research Funding; Nippon Shinyaku: Honoraria; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees; Ono Pharmaceutical: Honoraria, Other: Consulting fee, Research Funding; Otsuka Pharmaceutical: Honoraria, Research Funding; Pfizer Japan Inc: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Sanofi: Honoraria; Shire Japan KK: Honoraria; Kyowa-Hakko Kirin Co.,Ltd: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Consulting fee, Research Funding; Mochica Pharmaceutical Co., Ltd: Honoraria; Eisai: Research Funding; Janssen: Honoraria; Japan Blood Products Organization: Honoraria, Research Funding; Celgene: Honoraria; Chugai Pharmaceutical Co., Ltd: Honoraria, Research Funding; Daichi-Sankyo: Honoraria, Research Funding; Astellas Pharma Inc: Honoraria, Research Funding; Astellas Amgen BioPharma: Honoraria; Bristol-Myers Squibb: Honoraria; Taiho Pharama: Research Funding; Takeda Pharmaceutical Co., Ltd: Honoraria, Research Funding; Teijin: Research Funding; Alexion: Honoraria; Abbott: Research Funding. Nakamae:Takeda Pharmaceutical Co., Ltd.: Honoraria; Skire Japan KK.: Honoraria; Pfizer Japan Inc.: Honoraria, Membership on an entity's Board of Directors or advisory committees; Otsuka Pharmaceutical: Honoraria, Speakers Bureau; Novartis: Honoraria, Research Funding; Nippon Shinyaku: Honoraria; Kwowa-Hakko kirin Co., Ltd.: Honoraria; Japan blood Products Organization: Honoraria; Janssen: Honoraria; Chugai Pharmaceutical Co., Ltd.: Honoraria, Membership on an entity's Board of Directors or advisory committees; Celgene: Honoraria; Bristol-Myers Squibb: Honoraria; Astellas Pharma Inc.: Research Funding; Alexion: Honoraria.

Previously, we presented the results of a phase I trial of using cord blood (CB) derived regulatory T cells (Tregs) at a dose of 1x106 cells/kg in the prevention of graft vs. host disease (GVHD) in five patients undergoing allogeneic stem cell transplant (SCT). We now present an update of those patients and also the outcome of a single patient treated with CB Tregs at higher dose of 1x107 cells/kg. At the last follow up of 3.5 years, 5 of 6 patients are alive, in complete remission, without GVHD and off immune-suppression (table 1). One patient died of head injury at day 45 post-transplant without GVHD. None of the patients relapsed in spite of having high risk disease including Flt3+ acute myeloid leukemia (AML) (pt#1); refractory mycosis fungoides/ sezary syndrome (pt#2); relapsed refractory multiple myeloma including two autologous SCT (pt#3); myeloid sarcoma (pt#4); AML with complex cytogenetics (pt#5). Specifically, the sixth patient (treated at CB Tregs cell dose of 1x107 cells/kg) had a diagnosis of lymphoid blast crisis of chronic myelogenous leukemia (CML) and underwent allogeneic peripheral blood (PB) matched unrelated donor (MUD) SCT in second chronic phase with the conditioning regimen of fludarabine (40 mg/m2/d on day -5 to -2) and melphalan (140mg/m2 on day -2) and received CB Tregs at a dose of 1x107 cells/kg on day -1. The CB Tregs were manufactured at the MD Anderson GMP facility. Tregs were isolated from 4 out of 6 HLA matched CB unit with a post-thaw total nucleated cell (TNC) count of 1295 x 106 cells with 90% recovery. Enrichment of CD25+ Treg cells was accomplished with directly conjugated anti-CD25 magnetic microbeads and the LS column (Miltenyl) based selection. After selection, the total no. of isolated CB Tregs was 17.6 x 106 cells. These cells were ex-vivo expanded in culture for a total of 14 days in the continued presence of CD3/28 microbeads and interleukin-2. On the day of harvest, a total of 1359 x 106 Treg cells were generated with 96% viability. Based on patient's weight of 67 kg, a total of 67x107 CB Treg cells were infused. The expanded CB Tregs were also evaluated for functionality by using an in vitro suppression assay, where the stimulated CD4+ Tcon cells stained with CellTrace Violet and Tregs were added into a 96-well plate at a 1:1 and 1:2 ratio and incubated for three days at 37oC. As shown in figure 1A, the clinically manufactured CB Tregs were functional and exerted 98% suppression of the proliferating Tcon cells. Subsequently, the patient received PB MUD graft on day 0. The graft had a TNC count of 1900 x106 cells where the CD3+ T cells were at a dose of 400 x106 cells/kg resulting in a Treg: Tcon ratio of 1:40, a significantly lower number of Tregs compared to other published clinical trials using Treg prophylaxis for GVHD. There was no infusion reaction related to the CB Treg infusion, the patient engrafted on day+12 with 100% donor chimerism on day +30. The patient did not develop any grade II-IV GVHD and was off immune suppression by +6 months. At the time of last follow up of 2 years and 4 months, the patient remains alive, in complete remission and without GVHD. We compared the inflammatory cytokine profile as well as GVHD biomarkers for pt #6 to the rest of the five patients who received the lower dose of CB Tregs at 1x106 cells/kg (with up to 400 times Tcon cells in the graft), where 4 patients had developed acute GVHD. The inflammatory biomarkers of IL-6 (fig 1B) and IL-8 (fig 1C) for pt#6 were low to undetectable compared to the other patients. Similarly, the GVHD biomarkers of ST2 (fig 1D); MIG/ CXCL9 (fig 1E) and follistatin (fig 1F) were also low to undetectable in pt#6 compared to the rest. At the time of last follow up, all patients had resolved acute GVHD and were off-immune suppression and in complete remission. Based on these data, we conclude that CB Treg dose of 1x107 cells/kg may be able to prevent GVHD without alleviating the graft vs leukemia effect. Disclosures Popat: Jazz: Consultancy; Incyte: Research Funding; Bayer: Research Funding. Nieto:Affimed: Consultancy; Astra-Zeneca: Research Funding; Novartis: Research Funding; Affimed: Research Funding. Ciurea:Kiadis Pharma: Membership on an entity's Board of Directors or advisory committees, Other: stock holder; MolMed: Membership on an entity's Board of Directors or advisory committees; Spectrum: Membership on an entity's Board of Directors or advisory committees; Miltenyi: Research Funding. Qazilbash:Amgen: Consultancy, Other: Advisory Board; Genzyme: Other: Speaker; Bioclinical: Consultancy; Autolus: Consultancy. Champlin:Actinium: Consultancy; Johnson and Johnson: Consultancy; Sanofi-Genzyme: Research Funding. Parmar:Cellenkos Inc.: Equity Ownership, Membership on an entity's Board of Directors or advisory committees, Research Funding.

INTRODUCTION HLA-haploidentical allogeneic hematopoietic cell transplantation (allo-HCT) using post-transplantation cyclophosphamide (PT/Cy-haplo) can be a standard of care in patients suffering from poor prognostic hematological malignancies without conventional donors. Regarding killer cell immunoglobulin-like receptor (KIR) and HLA information on optimal donor selection in PT/Cy-haplo settings, the following factors associated with improved survival have been reported: HLA-DR/HLA-DP mismatch, KIR receptor-ligand mismatch, KIR B/x haplotype with KIR2DS2, and inhibitory KIR gene mismatch (Willem 2019, Solomon 2018, Symons 2010). However, the results were still inconclusive. In addition, it remains unknown whether the graft-versus-leukemia/tumor (GVL) effect of donor KIRs or HLAs is modified by residual tumor burden at PT/Cy-haplo. METHODS We retrospectively examined consecutive patients who received PT/Cy-haplo at our institution between June 2009 and December 2018. In both patients and donors, 16 KIR genes were genotyped using KIR SSO Genotyping Test (One Lambda, Inc.) and HLA allele typing was performed at HLA-A, -B, -C, and -DRB1. Cumulative incidence of relapse (CIR) was estimated using a cumulative incidence curve with nonrelapse mortality as a competing risk and compared using the Gray's test. RESULTS A total of 91 patients with available KIR typing data were eligible. Of these, HLA typing data were unavailable for 5 patients (5.5%). In this cohort, 76 HLA-C mismatched transplants (88%) were included, and the frequencies of donor KIR ligand were 78 (90.7%) in C1/C1, 8 (9.3%) in C1/C2, and 0 in C2/C2. The median age was 48 years (range, 17 - 68 years). Median follow-up time among survivors was 1,271 days (range, 242 - 3,135 days) after PT/Cy-haplo. This study included 54 AML, 6 MDS, 2 CML, 13 ALL, and 16 NHL patients. Thirty-four patients (37%) showed complete remission (CR) at PT/Cy-haplo, and 37 on the secondor third transplant (40.7%). In CR population at PT/Cy-haplo, the patients who underwent PT/Cy-haplo from a KIR2DS1-positive donor had significantly lower rates of CIR than those from a KIR2DS1-negative donor (2-year CIR, 9.2% vs 42%; P = 0.037; Figure 1A). Due to unavailability of cases, we were unable to perform the subgroup analysis based on donor C1 or C2 status. In PT/Cy-haplo from a KIR3DS1- or KIR2DL5-positive donor, similar results were obtained, most likely due to genetic linkage disequilibrium among these genes. No other donor KIR genes were associated with CIR. Furthermore, PT/Cy-haplo from a KIR2DS1-positive donor was significantly associated with improved OS (2-year OS, 83% vs 34%; P = 0.01; Figure 1C). Also, PT/Cy-haplo from a B/x donor significantly increased OS (2-year OS, 77% vs 35%; P = 0.019), but did not decrease CIR (2-year CIR, 16% vs 40%; P = 0.122). These results suggested that donor KIR2DS1 could have a more crucial role in prevention of leukemia relapse than donor B/x haplotype. In non-complete remission (NCR) population at PT/Cy-haplo, however, PT/Cy-haplo from a KIR2DS1-positive donor and a B/x donor did not significantly improve CIR (Figure 1B) or OS (Figure 1D). Although we investigated the following previously reported models: KIR mismatch with ligand incompatibility model, receptor-ligand model, missing ligand model, inhibitory KIR gene model, and HLA-DRB1 disparity of graft-versus-host direction, none was found to be associated with significantly improved CIR or OS. CONCLUSION We found that in PT/Cy-haplo settings, with donor-recipient HLA-C mismatch in almost all cases, a KIR2DS1-positive donor significantly contributed to decreased CIR and increased OS in CR population at PT/Cy-haplo, but not in NCR population. These results were consistent with the 2012 NEJM data by Venstrom et al in patients undergoing allo-HCT from HLA-matched or one-allele mismatched unrelated donors. Although the exact mechanism remains unclear, activating KIR2DS1, known as a player in the activation and tolerance of NK cells, could mediate NK-cell function and enhance GVL effect through NK alloreactivity in low tumor burden status at PT/Cy-haplo also in the PT/Cy-haplo setting. Our results may contribute to the establishment of an optimal donor selection algorithm. In future, elucidating the detailed mechanism of our findings could lead to the development of a novel preventive or therapeutic strategy for leukemia relapse. Disclosures Ido: MSD K.K.: Honoraria. Koh:Alexion: Honoraria; DAIICHI SANKYO COMPANY: Honoraria; MSD K.K: Honoraria; Takeda Pharmaceutical: Honoraria, Research Funding; NIHON PHARMACEUTICAL: Honoraria; Takeda Science Foundation: Research Funding; Chugai Pharmaceutical: Research Funding; Amgen Astellas BioPharma: Research Funding; Asahi Kasei Corporation: Research Funding; IQVIA Services Japan: Research Funding. Okamura:MSD K.K: Honoraria; Eisai Co., Ltd: Honoraria. Koh:Bristol-Myers Squibb: Honoraria. Nanno:Eisai Co., Ltd.: Honoraria; MSD K.K: Honoraria; Chugai Pharmaceutical Co., Ltd.: Honoraria. Nakamae:Novartis: Honoraria, Research Funding; Takeda Pharmaceutical Co., Ltd.: Honoraria; Japan Blood Products Organization: Honoraria; Kyowa-Hakko Kirin Co.,Ltd: Honoraria; Astellas Pharma Inc.: Research Funding; Bristol-Myers Squibb: Honoraria; Pfizer Japan Inc.: Honoraria, Membership on an entity's Board of Directors or advisory committees; Chugai Pharmaceutical Co., Ltd.: Honoraria, Membership on an entity's Board of Directors or advisory committees; Alexion: Honoraria; Celgene: Honoraria; Janssen: Honoraria; Nippon Shinyaku: Honoraria; Otsuka Pharmaceutical: Honoraria, Membership on an entity's Board of Directors or advisory committees; Shire Japan KK.: Honoraria. Nakashima:Novartis: Honoraria; Kyowa-Hakko Kirin Co.,Ltd: Honoraria; Eisai Co.,Ltd: Honoraria, Research Funding; Celgene Corporation: Research Funding; Bristol-Myers Squibb: Honoraria; Astellas Pharma Inc.: Research Funding; Amgen Astellas BioPharma K.K.: Honoraria, Research Funding; AbbVie Inc.: Research Funding. Nakane:Kyowa-Hakko Kirin Co.,Ltd: Honoraria; Chugai Pharmaceutical Co., Ltd.: Honoraria; DAIICHI SANKYO COMPANY, LIMITED.,: Honoraria; Mundipharma K.K.: Honoraria; Novartis: Honoraria; Janssen Pharmaceutical K.K.: Research Funding; MSD K. K,: Research Funding; Pfizer Japan Inc.: Research Funding; Bayer Yakuhin, Ltd: Research Funding. Hino:Taiho Pharama: Research Funding; Takeda Pharmaceutical Co., Ltd: Honoraria, Research Funding; Astellas Amgen BioPharma: Honoraria; Bristol-Myers Squibb: Honoraria; Celgene: Honoraria; Chugai Pharmaceutical Co., Ltd: Honoraria, Research Funding; Daichi-Sankyo: Honoraria, Research Funding; Eisai: Research Funding; Janssen: Honoraria; Japan Blood Products Organization: Honoraria, Research Funding; Kyowa-Hakko Kirin Co.,Ltd: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Consulting fee, Research Funding; Mochica Pharmaceutical Co., Ltd: Honoraria; Pfizer Japan Inc: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Sanofi: Honoraria; Shire Japan KK: Honoraria; Sumitomo Dainippon Parma: Honoraria, Research Funding; Ono Pharmaceutical: Honoraria, Other: Consulting fee, Research Funding; Otsuka Pharmaceutical: Honoraria, Research Funding; Nippon Shinyaku: Honoraria; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees; Teijin: Research Funding; Nihon Pharmaceutical Co., Ltd: Research Funding; Astellas Pharma Inc: Honoraria, Research Funding; MSD: Honoraria, Research Funding; Mundipharma: Honoraria; Abbott: Research Funding; Alexion: Honoraria. Nakamae:Pfizer Japan Inc.: Honoraria, Membership on an entity's Board of Directors or advisory committees; Otsuka Pharmaceutical: Honoraria, Speakers Bureau; Novartis: Honoraria, Research Funding; Nippon Shinyaku: Honoraria; Kwowa-Hakko kirin Co., Ltd.: Honoraria; Japan blood Products Organization: Honoraria; Janssen: Honoraria; Chugai Pharmaceutical Co., Ltd.: Honoraria, Membership on an entity's Board of Directors or advisory committees; Celgene: Honoraria; Bristol-Myers Squibb: Honoraria; Astellas Pharma Inc.: Research Funding; Alexion: Honoraria; Takeda Pharmaceutical Co., Ltd.: Honoraria; Skire Japan KK.: Honoraria.

Background Adoptive therapy with regulatory T cells (Tregs) has already been established as a promising strategy for prevention of graft vs. host disease (GVHD) in clinical trials. Our group at MD Anderson Cancer Center has previously shown that a significantly lower dose of cord blood (CB) Tregs as compared to conventional T cells (Tcon) in the donor graft is able to prevent GVHD while preserving the graft vs. leukemia (GVL) effect. Therefore, we now examined the efficacy of using CB Tregs in the treatment of GVHD. Method: Xenogenic GVHD mouse model was established using NOD/SCID/IL2Rgnull (NSG) mice were sublethally irradiated at 300 cGy followed by injection of 1x107 peripheral blood (PB) mononuclear cells on day 0, as previously described. Ex vivo expanded CB Tregs were injected on day -1 (for prophylaxis) or at different days post PBMC injection for treatment. Mice were serially examined for appearance, weight, posture, GVHD score and survival. Serial peripheral blood sampling for flow cytometry and serum cytokine analysis. CB Tregs were also analyzed by flow cytometry. In order to understand the impact of the routine immunosuppressive agents on the function of CB Tregs, we incubated the CB Tregs in culture with cyclosporine (200ng/ml) or sirolimus (20 ng/ml) from day 8 to day 14. Cells were harvested on day 14 and analyzed by flow cytometry and CellTrace Violet suppression assay. Result: A single dose of 1x107 CB Tregs injected at day +7 did not result in a survival difference compared to the control arm (data not shown). Therefore, we froze multiple aliquots of expanded CB Tregs to be injected at different intervals post-transplant. Thawed CB Tregs showed stable phenotype of CD4+25+127lo: 94.7%; intracellular Helios+: 98.5% and intracellular FOXP3+: 99.4% and were able to suppress 87% of the proliferating conventional T-cells (Tcons). In order to compare the efficacy of the CB Tregs for GVHD treatment, we set up 3 arms: i) Control: PBMC alone; ii) Prophylaxis: 1x107 CB Tregs injected on day -1 and iii) Treatment: 1x107 CB Tregs injected on day +4, +7, +18 and +25. The mice in the prophylaxis and treatment arm retained their weight as compared to the control arm (p Conclusions: Multiple injections with CB Tregs can effectively treat GVHD. Combination therapy of CB Tregs with the commonly used GVHD treatments can be explored. Figure 1 Disclosures Iyer: Genentech/Roche: Research Funding; Incyte: Research Funding; Seattle Genetics, Inc.: Research Funding; Novartis: Research Funding; Bristol-Myers Squibb: Research Funding; Arog: Research Funding. Parmar:Cellenkos Inc.: Equity Ownership, Membership on an entity's Board of Directors or advisory committees, Research Funding.

Background: Systemic Lupus Erythematosus (SLE) is a chronic inflammatory autoimmune disorder with multi-organ involvement, including skin rash, joint pain, neurological dysfunction, pulmonary fibrosis, vasculitis, and renal failure. Previously it has been reported that SLE patients have a lower percentage of regulatory T cells (Tregs) and when compared to healthy population, Tregs derived from SLE patients show defect in their suppressor function. Our group at MD Anderson Cancer Center has already shown that a significantly lower dose of cord blood (CB) Tregs as compared to conventional T cells (Tcon) in the donor graft is able to prevent graft vs host disease (GVHD). Furthermore, adoptive therapy with CB Tregs is being explored as a therapy for bone marrow failure including aplastic anemia as a single agent in the non-transplant setting. Therefore, we hypothesized that adoptive therapy with CB Tregs may be utilized for the treatment of SLE. Method: For examining the efficacy of CB Tregs in vivo, we developed a humanized SLE model, where female Rag2-/-γc-/- mice were transplanted with 3 ~ 4 x 106 human SLE-PBMCs by intravenous injection on day 0. The mice were allowed to develop disease (control) and at 1 weeks post-transplant a single dose of 1x107 CB Tregs was injected through the tail vein (treatment). Mice peripheral blood (PB) was assessed weekly for their cell compartment composition by using flow cytometry; double stranded DNA (dsDNA IgG) and plasma cytokines. Mice were monitored twice per week for weight loss, GVHD score and survival. Weekly urine collection was performed to analyze for albumin and creatinine. At the time of euthanasia, harvested organs were analyzed by flow cytometry, and immunohistochemistry. Result: Single injection of CB Tregs was sufficient to slow down the phenotype of SLE as shown in figure 1A, where the physical appearance of CB Treg treated mice was significantly better than the control and it correlated with a significantly lesser CD3+ infiltrates in the spleen of the treatment vs. control mice (Figure 1B) and a similar finding was observed in the CD20 infiltrate in the renal tissue (data not shown). While a widespread parakeratosis in the skin of the control mice, almost complete resolution was observed in the treatment arm (figure 1C). In addition, a lack of lymphoid infiltrate in the kidney and resolution of splenic lymphoid hyperplasia was observed in the CB Treg recipients (data not shown). In another experiment, we studied the role of weekly injection of 1x107 CB Tregs with the first injection administered at week 4 after the lupus inoculation. Significant improvement was observed in the urine albumin (p Conclusion: We conclude that adoptive therapy with CB Tregs is a viable option for SLE and additional studies are planned to optimize the dose and schedule details. Figure 1 Disclosures Khoury: Angle: Research Funding; Stemline Therapeutics: Research Funding; Kiromic: Research Funding. Iyer:Seattle Genetics, Inc.: Research Funding; Novartis: Research Funding; Bristol-Myers Squibb: Research Funding; Genentech/Roche: Research Funding; Incyte: Research Funding; Arog: Research Funding. Parmar:Cellenkos Inc.: Equity Ownership, Membership on an entity's Board of Directors or advisory committees, Research Funding.

Background: Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is a curative treatment for hematologic malignancies. In addition to hematopoietic cell transplantation-comorbidity index (HCT-CI) and disease risk index (DRI), age, performance status (PS), conditioning regimen intensity, and donor source are used to assess the transplant outcome in patients. Recently, several serum markers, such as ferritin and albumin, have also been reported as additional useful prognostic markers. Beta-2 microglobulin (BMG) is a component of major histocompatibility complex class 1 molecules in all nucleated cells, and serum BMG levels reflect renal function, tumor burden, and inflammatory conditions. Although elevated serum BMG levels are reportedly markers for poor prognosis of several hematological malignancies, no study has assessed the prognostic significance of pre-transplant serum BMG levels for allo-HSCT. Methods: We retrospectively registered consecutive patients who underwent allo-HSCT from April 2010 to September 2017 with available pre-transplant serum BMG levels at our institute. Cox regression models were used to estimate hazard ratios (HRs) with 95% confidence intervals in the univariate and multivariate analyses. In this study, the variables analyzed were age, sex, disease, HCT-CI, PS, DRI, number of times HSCT was performed, conditioning regimen intensity, donor source, cytomegalovirus (CMV) serostatus, and pre-transplant serum BMG level in each patient. Predictors with borderline significance (p Result: A total of 288 patients were identified during the study period. The median age was 47 (range: 17-48) years. The clinical characteristics are shown in Table 1. The median follow-up period of survivors (192 patients) was 674.5 (range: 15-2642) days. The median pre-transplant BMG level was 2.1 (range: 0.9-11.6) mg/mL. When stratified into quartiles of pre-transplant BMG levels, the 2-year OS rates were 89.2%, 62.8%, 64.3%, and 33.7% in quartiles 1 (0.9-1.6), 2 (1.7-2.0), 3 (2.1-2.9), and 4 (3.0-11.6), respectively. Because quartiles 2 and 3 showed almost the same OS rates, we combined these two groups and assessed the association between major transplant outcomes (OS, Rel/Prog, NRM, acute GVHD, and chronic GVHD) and the following three groups of BMG levels: 0.9-1.6 mg/mL (lower BMG group), 1.7-3.0 mg/mL (intermediate BMG group as the reference), and >3.0 mg/mL (higher BMG group). In the univariate analysis, the lower BMG group was significantly associated with an increased probability of OS (HR: 0.29, p=0.002) and decreased probability of Rel/Prog and NRM (HR: 0.58, p=0.048 and HR: 0.19, p=0.02, respectively) compared with those of the intermediate BMG group. The higher BMG group was significantly associated with a decreased probability of OS (HR: 2.4, p Conclusions: The study results suggest that pre-transplant serum BMG level is a potential prognostic marker for survival after allo-HSCT, which is independent of other prognostic factors, including well-known prognostic systems, such as HCT-CI and DRI. Disclosures Nakamae: Otsuka Pharmaceutical Co., Ltd.: Consultancy, Honoraria, Research Funding. Hino:Otsuka Pharmaceutical Co., Ltd.: Research Funding; Novartis: Research Funding. Nakamae:Otsuka Pharmaceutical Co., Ltd.: Consultancy, Honoraria, Research Funding.

INTRODUCTION The prognosis for allogeneic hematopoietic cell transplantation (allo-HCT) is relatively poor in patients with acute myeloid leukemia (AML) who are not in remission (non-CR). Wilms' tumor-1 gene messenger ribonucleic acid (WT1 mRNA), which is overexpressed in almost all AML, has been used as an indicator of monitoring minimal residual disease (MRD) and has been regarded as one of the prognostic factors in AML patients with complete remission (CR). However, the association between the expression levels of WT1 mRNA in peripheral blood (WT1) before allo-HCT and risk of mortality in AML patients in non-CR remains quite elusive. We therefore assessed the effect of the pre-transplant WT1 level on survival after allo-HCT in AML patients in non-CR. METHODS We retrospectively analyzed data from consecutive patients undergoing allo-HCT at our institution between November 2007 and January 2017. We excluded patients who did not have an available WT1 value within 28 days before the start of conditioning. RESULTS A total of 125 AML patients, including 46 non-CR patients (36.8 %), were eligible for this study. The median age was 48 years (range: 17-68 years) and the number of males was 69 (55.2%). Forty-two patients (33.6%) had AML with myelodysplasia-related changes. This study included 34 patients (27.2%) who had undergone multiple transplantation. Myeloablative and reduced-intensity conditioning were used in 73 (58.4%) and 52 (41.6%) patients, respectively. In 63 patients who received transplants from either a related peripheral blood stem cell or bone marrow (BM) donor, four pairs (6.3%) were serologically mismatched for one antigen of HLA and 45 pairs (71.4%) received transplants from HLA haploidentical donors. In 32 patients who received transplants from an unrelated BM donor, seven pairs (21.9%) were serologically mismatched for one HLA antigen. Twenty-nine patients (23.2%) received unrelated cord blood transplantation. Among 46 non-CR patients, the median follow-up period among survivors was 1,092 days (range: 688-2,607 days) following allo-HCT. Receiver operating characteristic analysis for prediction of composite events including any cause of death or subsequent transplantation indicated that the best cutoff value for WT1 was 5,000 copies/ μg RNA in non-CR AML patients. Estimated two-year, event-free survival of non-CR patients with WT1 levels of less than 5,000 copies/ μg RNA was significantly higher than that of those with WT1 levels of 5,000 copies/ μg RNA or more (41.2% [95% confidence interval (CI), 18.6-62.6] vs 10.3% [95% CI, 2.6-24.3]; P=0.006). On multivariate analysis of the non-CR patients, WT1 5,000 copies/ μg RNA or more was significantly associated with increased risk of mortality (hazard ratio (HR), 2.7; 95% CI, 1.3-5.5; P=0.008). Log10-transformed WT1 (continuous scale) was also significantly related to increased risk of mortality (HR, 1.5; 95% CI, 1.0-2.1; P=0.037). In the entire cohort, log10-transformed WT1 (divided into four categories) before allo-HCT was found to be the most powerful prognostic factor of survival among remission status, cytogenetic risk group, and revised disease risk index, applying Akaike's information criterion. Moreover, under the assumption of a non-linear model, as the log10-transformed WT1 level rose, the HR of mortality increased monotonically; a non-linear fit was obtained using a restricted cubic spline function (three knots; Figure 1). CONCLUSION Our data showed that WT1 levels obtained before allo-HCT monotonically increased HR of mortality in a non-linear manner regardless of CR status. Of importance is the finding that WT1 levels before allo-HCT were proportionally correlated with probability of survival after allo-HCT in non-CR AML patients. This suggests that the level of expression of WT1 mRNA in peripheral blood might reflect tumor burden and that there may be a WT1 threshold in non-CR patients for benefiting from allo-HCT. Further prospective studies of WT1 are necessary to determine acceptable or feasible levels of disease activity for receiving allo-HCT in relapsed or refractory AML patients. Disclosures Nakamae: Otsuka Pharmaceutical Co., Ltd.: Consultancy, Honoraria, Research Funding. Hino:Otsuka Pharmaceutical Co., Ltd.: Research Funding; Novartis: Research Funding. Nakamae:Otsuka Pharmaceutical Co., Ltd.: Consultancy, Honoraria, Research Funding.

Introduction Cord blood derived ex vivo expanded regulatory T cells(CB-Tregs) have been verified that they can effectively prevent xenogenic graft-versus-host disease(GVHD) in NSG mice, which provide evidence to further investigate the effect of CB-Tregs in clinical setting. However, due to the potent suppression function of CB-Tregs, it needs to elucidate the concerning about whether CB-Tregs worsen leukemia or dampen anti-leukemia activity of donor cells. Beatrice et al. report donor derived in vitro expanded Treg can also prevent GVHD successfully while allowing a powerful graft-versus-leukemia(GVL) in murine models. We hypothesize cord blood derived ex vivo Treg are effective in preventing GVHD without compromising GVL. Methods Tregs are isolated from cord blood and expanded with CD3CD28 beads and IL-2 in SCGM medium. Then the cells are harvested on day14 after culturing. We use CD4+CD25+CD127low or - Foxp3+ to confirm Tregs, viabilty and purification on flow cytometry. The suppresive assay of CB-Tregs are based on CFSE. 3 or 10 million HL-60 cells are used to build AML model in NSG mouse. AML VS AML+Tregs or AML+PBMC/Tcons VS AML+PBMC/Tcons+Tregs are set up in each experiments. The primary end point is survival, secondary point is AML percentage and weight loss as well as the cytokines in the serum and tissue pathology. Results 62-135 folds of CB-Tregs compared original number are harvested on day14, >90% cells are CD4+CD25+CD127low or - Foxp3+, There is no any difference in weight loss, AML percentage of peripheral blood and survival between AML+PBMC and AML+PBMC+Treg (Figure1 a, b,c and d,e,f). There is no significant difference in AML percentage between AML+PBMC/Tcons +Treg and AML+PBMC/Tcons, but mice in AML+Tcons+Treg survived longer than mice in AML+Tcons (Figure 2a,b,c,d). Conclusion CB-Tregs do not deteriorate the development of AML, they also do not impair anti-leukemia activity of PBMC or Tcons while they provide protection from GVHD. Our findings lay down the basis for testing impact CB-Tregs on CAR T cell activity in Vivo. Disclosures No relevant conflicts of interest to declare.

Mast cells are the major effector-cell type for immediate hypersensitivity and other forms of allergic reactions. Expression of 4-1BB, a member of the tumor necrosis factor receptor superfamily, is induced at mRNA and protein levels on stimulation through the high-affinity receptor for immunoglobulin E (IgE; FcepsilonRI). In this study, we present evidence that agonistic anti-4-1BB antibodies can enhance FcepsilonRI-induced cytokine production and secretion. Consistent with this, 4-1BB-deficient mast cells exhibit reduced degranulation and cytokine production on FcepsilonRI stimulation. Analysis of 4-1BB ligand (4-1BBL)-deficient cells supported this notion. As a potential mechanism for these defects, we identified a defect in Ca2+ flux induced by FcepsilonRI stimulation. The defective Ca2+ flux could be accounted for by the reduced activity of Lyn/Btk/phospholipase C-gamma2 pathway and constitutive interactions between 4-1BB and Lyn. Therefore, FcepsilonRI-inducible 4-1BB plays a costimulatory function together with FcepsilonRI stimulation.

Introduction: Sinusoidal obstruction syndrome (SOS) is one of the potentially fatal complications of hematopoietic stem cell transplantation (HSCT). In particular, severe SOS frequently leads to multiple organ failure, and a worse prognosis. Thus, prophylaxis against development of SOS could contribute improved survival after HSCT. Previous reports demonstrated the effectiveness of the prophylactic use of ursodeoxycholic acid (UDCA) or certain anticoagulants, including unfractionated and low-molecular-weight heparin, for SOS. In two randomized controlled trials and two meta-analyses it was reported that UDCA, a hydrophilic bile acid, was an effective and safe drug for prophylaxis against SOS. The usefulness and feasibility of prophylactic use of anticoagulants after allogeneic HSCT are however still controversial. In addition, to our knowledge no study has evaluated the feasibility of usage of UDCA combined with an anticoagulant for SOS prevention after allogeneic HSCT in adult patients. To assess the efficacy and safety of use of UDCA combined with an anticoagulant as SOS prophylaxis, we performed a retrospective cohort study to examine the occurrences of SOS and hemorrhagic events in patients who underwent myeloablative allogeneic HSCT at our institution. We examined use of any anticoagulant together with simultaneous administration of UDCA, in comparison with UDCA alone for the prevention of SOS. Patients and methods: We reviewed the charts of consecutive adult patients in whom myeloablative allogeneic HSCT was performed at our hospital from November 1994 to May 2014, and who received either unfractionated heparin or dalteparin (low-molecular-weight heparin) with UDCA (group 1), danaparoid with UDCA (group 2), or UDCA only (group 3), used for prophylaxis against SOS. Results: A total of 280 patients (group 1: n=52; group 2: n=33; and group 3: n=195) were investigated. The proportions of patients with risk factors for SOS-including non-remission at the time of HSCT, a second or subsequent HSCT, high aspartate aminotransferase (AST) levels before HSCT, high ferritin levels before HSCT, a history of receiving gemtuzumab ozogamicin, and HLA disparity-were similar across the three groups. In group 1, a conditioning regimen containing busulfan was used less frequently (P = 0.002). SOS occurred in seven patients (13.7%) in group 1, five patients (15.2%) in group 2, and 28 patients (14.4%) in group 3, all meeting the Seattle criteria. None of the patients in group 1, two (6.1%) in group 2, and nine (4.6%) in group 3 had SOS diagnosed according to the Baltimore criteria. There was no significant difference in the incidence of SOS among the three groups. In addition, with regard to the cumulative incidence of severe SOS, no statistically significant difference was present among the three groups. The incidence of hemorrhagic events within 30 and 100 days following allogeneic HSCT was not significantly different across the three groups (30 days; 5.8%, 3.0%, 5.1%, P = 0.843, 100 days; 17.6%, 15.2%, 14.4%, P=0.843, respectively). Furthermore, the probabilities of OS and NRM until day 100 after allogeneic HSCT were similar among the three groups (P = 0.733 and P = 0.637, respectively). In a univariate model, a history of gemtuzumab ozogamicin treatment, high serum ferritin levels before HSCT, an HLA mismatched donor, and non-complete remission of disease at the time of allogeneic HSCT were found to be significant risk factors for SOS. Multivariate analysis revealed that a history of gemtuzumab ozogamicin therapy, a mismatched HLA donor, and non-complete remission of disease at the time of allogeneic HSCT were significant and independent risk factors for SOS. In the multivariate as well as univariate analyses, combined administration of UDCA and any anticoagulant for SOS prophylaxis did not have a significant effect on the incidence SOS, when compared to prophylaxis with UDCA alone. Conclusion: Our study results suggest that the combined use of UDCA and an anticoagulant for SOS prophylaxis after myeloablative allogeneic HSCT in adult patients was not beneficial. Establishment of an optimal strategy for prophylaxis against SOS after HSCT is still needed. Disclosures Nakane: Mundipharma KK: Research Funding. Koh:Pfizer: Consultancy, Honoraria. Hino:Pfizer: Honoraria, Research Funding; Nippon Shinyaku: Honoraria, Speakers Bureau; Alexion: Honoraria, Research Funding. Nakamae:Mochida Pharmaceutical Co., Ltd.: Honoraria, Research Funding; Pfizer: Consultancy, Honoraria; Novartis Pharma KK: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: travel/accommodation/meeting expenses, Research Funding.

Castleman's disease, an atypical lymphoproliferative disorder, can be classified into 2 types: hyaline-vascular and plasma cell types according to the histologic features of the affected lymph nodes. The plasma cell type is frequently associated with systemic manifestations and is often refractory to systemic therapy including corticosteroids and chemotherapy, particularly in multicentric form. Dysregulated overproduction of interleukin-6 (IL-6) from affected lymph nodes is thought to be responsible for the systemic manifestations of this disease. Therefore, interference with IL-6 signal transduction may constitute a new therapeutic strategy for this disease. We used humanized anti-IL-6 receptor antibody (rhPM-1) to treat 7 patients with multicentric plasma cell or mixed type Castleman's disease. All patients had systemic manifestations including secondary amyloidosis in 3. With the approval of our institution's ethics committee and the consent of the patients, they were treated with 50 to 100 mg rhPM-1 either once or twice weekly. Immediately after administration of rhPM-1, fever and fatigue disappeared, and anemia as well as serum levels of C-reactive protein (CRP), fibrinogen, and albumin started to improve. After 3 months of treatment, hypergammaglobulinemia and lymphadenopathy were remarkably alleviated, as were renal function abnormalities in patients with amyloidosis. Treatment was well tolerated with only transient leukopenia. Histopathologic examination revealed reduced follicular hyperplasia and vascularity after rhPM-1 treatment. The pathophysiologic significance of IL-6 in Castleman's disease was thus confirmed, and blockade of the IL-6 signal by rhPM-1 is thought to have potential as a new therapy based on the pathophysiologic mechanism of multicentric Castleman's disease. (Blood. 2000;95:56-61)

To the editor: Several studies have indicated that platelet recovery occurs in a subgroup of immune thrombocytopenia (ITP) patients after successful Helicobacter pylori ( H pylori) eradication.[1][1],[2][2] Interestingly, a higher response rate to H pylori eradication therapy has been reported in

We showed the dose-dependent growth inhibition by alltrans retinoic acid (ATRA) of myeloma cells freshly isolated from patients. ATRA downregulated the cell surface expression of interleukin-6 receptor (IL- 6R) and/or glycoprotein (gp) 130. The growth-inhibitory activity of ATRA was well correlated with that of anti-gp 130 antibody in every sample. Furthermore, ATRA inhibited the production of IL-6 from both myeloma cells and marrow stromal cells, and recombinant IL-6 (rIL-6) could partially recover the myeloma cell growth that had been inhibited by ATRA. These data suggest that ATRA may inhibit the proliferation of myeloma cells both by the downregulation of IL-6R and gp130 expression on myeloma cells and by the inhibition of IL-6 production from myeloma and stromal cells. Prednisolone (PSL) and interferon-gamma (IFN-gamma) also inhibited the myeloma growth, while their effects were different from those of ATRA on IL-6 R and gp130 expression, IL-6 production, and morphological change. The inhibitory effect of ATRA on myeloma cell proliferation was observed in 10 of 14 samples obtained from eight patients, which suggests that ATRA may be a potent new therapeutic agent for some myeloma patients.

Background: Autonomic nerve function can be affected by various factors such as patient activity of daily living, disease status, treatment history and/or comorbidity. Indeed, autonomic nervous system dysfunction, as indexed by heart rate variability (HRV), has shown prognostic value for various disease outcomes, but its influence on outcomes following allogeneic hematopoietic cell transplantation (allo-HCT) is unclear. We therefore conducted a prospective observational study to determine the impact of autonomic nervous system dysfunction on outcomes following allo-HCT. Methods: From July 2011 to July 2013, we prospectively registered patients who had received allo-HCT in our institute. We also applied well-established examination of HRV as a surrogate maker of the autonomic nervous system. HRV data were collected from 24-hour ambulatory ECG recordings within 28 days of the starting day of the conditioning regimen for allo-HCT. Obtained data were analyzed with RR data analysis software (MemCalc/CHIRAM version 3, GMS Co., LTD., Tokyo, Japan). The following parameters were employed as markers of HRV: standard deviation of NN interval (SDNN) and the squares of the differences between adjacent normal-to-normal RR intervals (r-MSSD) in time domain analysis, and low-frequency (LF) and high-frequency (HF) power in frequency domain analysis. Δ Akaike's information criterion (Δ AIC) was used to compare the HRV components-added model to the basic model by the Pre-transplantation Assessment of Mortality (PAM) score, HCT-specific comorbidity index (HCT-CI), or disease risk index (DRI) in a Cox proportional hazards model. Results: We registered 112 consecutive allo-HCTs (103 patients) who agreed to participate in this study. The median age of the patients was 45.5 years (range: 18-66) and the median follow-up period for survivors (76 patients) was 961 days (range: 159-1654). Diagnoses included acute myeloid leukemia (n=55, 49%), acute lymphoid leukemia/lymphoblastic lymphoma (n=13, 12%), mixed phenotype acute leukemia (n=3, 3%), myelodysplastic syndrome (n=15, 13%), adult T cell leukemia/lymphoma (n=7, 6%), aggressive lymphomas (n=6, 5%), indolent lymphoma/chronic lymphoid leukemia (n=3, 3%), chronic myeloid leukemia/other myeloproliferative neoplasms (n=5, 4%), aplastic anemia (n=2, 2%), and others (n=3, 3%). Stem cell sources consisted of HLA-matched related donors for 18 transplants (16%), mismatched related donors for 24 transplants (22%), matched unrelated donors for 32 transplants (29%), mismatched unrelated donors for 8 transplants (7%), and cord blood for 30 transplants (27%). Myeloablative conditioning was employed for 84 transplants (75%). Median value of LF, HF, SDNN, and r-MSSD was 409 msec2 (range: 27-1279), 103 msec2 (range: 5-1309), 122 msec (range: 48-231), and 20 msec (range: 4-95), respectively.From univariate analysis, the reduction of LF, HF, SDNN, or r-MSSD was significantly associated with decreased probability of OS (hazard ratio (HR): 0.7 for LF per 100 msec2 (p Conclusions: Pre-transplant autonomic nervous system dysfunction is a powerful predictor of survival likely because it reflects the comprehensive physiological or pathological status of the patient. Of note, LF was a powerful predictor for survival and statistically independent from well-known prognostic indexes or scoring systems such as PAM, HCT-CI, and DRI. Disclosures Nakane: Otsuka: Honoraria. Nakamae:Otsuka: Other: My spouse receives research funding from Otsuka; Kyowa Kirin: Other: My spouse receives research funding from Kyowa Kirin. Nishimoto:Otsuka: Honoraria. Hino:Celgene: Honoraria. Nakamae:Otsuka: Honoraria, Research Funding; Kyowa Kirin: Honoraria, Research Funding.

Functional deregulation of transcription factors has been found in many types of tumors. Transcription factor AML1/RUNX1 is one of the most frequent targets of chromosomal abnormalities in human leukemia and altered function of AML1 is closely associated with malignant transformation of hematopoietic cells. However, the molecular basis and therapeutic targets of AML1-related leukemia are still elusive. Here, we explored immediate target pathways of AML1 by in vitro synchronous inactivation in hematopoietic cells. We found that AML1 inhibits NF-κB signaling through interaction with IκB kinase complex in the cytoplasm. Remarkably, AML1 mutants found in myeloid tumors lack the ability to inhibit NF-κB signaling, and human cases with AML1-related leukemia exhibits distinctly activated NF-κB signaling. Furthermore, inhibition of NF-κB signaling in leukemic cells with mutated AML1 efficiently blocks their growth and development of leukemia. These findings reveal a novel role for AML1 as a cytoplasmic attenuator of NF-κB signaling and indicate that NF-κB signaling is one of the promising therapeutic targets of hematologic malignancies with AML1 abnormality.