ALBERT

Description: Key Points Pathogen-inactivated platelets were noninferior in preventing bleeding only in intention-to-treat analysis. In contrast to animal models, alloimmunization could not be prevented when using pathogen-inactivated platelets.

Description: Abstract 1179 Background Previous studies by our laboratory have demonstrated changes in apheresis collected, PLT concentrates during storage that are enhanced by Mirasol®PRT treatment. These include increased expression of P-selectin on PLTs and increased formation of neutrophil (PMN)/PLT aggregates. To explore the effect of these changes in a microvascular environment, we measured PLT adherence in a microfluidic chamber coated with collagen. Methods Three, double apheresis platelet products were collected from healthy volunteers with TRIMA system under an IRB approved protocol. One product of each pair was treated with Mirasol PRT and both were stored under standard conditions. Aliquots were sterilely removed from products during storage. To 1000 μl of fresh, ABO type specific, citrate anticoagulated whole blood was added 60 μl of apheresis platelet concentrate with or without PRT treatment on day 1 or 7 of storage and incubated for 5 min at 37C. The sample was recalcified with 20 mM CaCl2 and then pulled through the inlet of a microfluidic chamber at a flow sheer rate of 100 s−1. The flow chamber was composed of two parts, a glass slide patterned with collagen and a series of four polydimethylsiloxane microfluidic chambers per inlet. Stored PLTs were labeled with fluorescently labeled anti-CD41 to distinguish from PLTs of the whole blood. The chamber was mounted on an inverted fluorescence microscope, and video microscopic images sampled on observation field every 7 sec over 7 min. The number of fluorescent cells (stored PLTs) per field and the total area covered by all PLTs were determined at 7 min. Results The area, expressed as % of total field, covered by all of the PLTs in the sample was not different for whole blood alone (29 ± 3); Day 1 untreated (23 ± 9); Day 1 PRT treated (26 ± 8); Day 7 untreated (21 ± 5); and Day 7 treated (25 ± 9) PLTs. In contrast, there was an increase in the number of treated apheresis PLTs at Day 1 compared to untreated apheresis platelets binding to the chamber (2.26 ± 0.61 untreated, vs. 5.45 ± 1.45 treated, numbers are mean ± SEM for numbers of cells adhered normalized to the PLT count in the product, significant, p=0.0229). There was also an increase in binding of treated compared to untreated PLTs at Day 7 (2.43 ± 0.47 untreated, vs. 4.42 ± 1.35 treated). However, the results for untreated PLTs on Day 1 and 7 and treated PLTs on study days were not different. The increased binding of Mirasol PRT treated PLTs parallels the small decrease in recovery seen in clinical studies of patients receiving treated PLT concentrates compared to untreated products. Conclusion PRT treatment increases adherence of PLTs early in storage but does not appear to progress further. The changes may have implications for clinical responses to platelet transfusions. Evaluation of adherence in the microfluidic chamber provide a model which simulate the microvascular environment. Disclosures: Ambruso: Terumo BCT: Research Funding. Seewald:Terumo BCT: Research Funding. Marschner:Terumo BCT: Employment. Goodrich:Terumo BCT: Employment.

Description: Abstract 718 Introduction: The presence of donor white blood cells (WBC) in transfused blood products can induce alloimmunization, and reducing or eliminating this response may prove to be of clinical benefit. The use of a pathogen reduction method based on UV light illumination in the presence of riboflavin has been shown to induce changes in WBCs that result in a failure to bind to, or induce proliferation of allogeneic PBMCs in vitro. In addition, a study in rats has shown a reduction in alloimmunization in vivo using this treatment. Transfusion of cells illuminated with UV light at other doses without riboflavin has been shown to induce some degree of tolerance with a reduced antibody response to subsequent allogeneic transfusions. We sought to assess both the degree of alloimmunization in mice given pathogen reduced versus untreated allogeneic platelets, as well as determine if cells from mice given pathogen reduced platelets exhibited signs of tolerance ex vivo. Methods: Peripheral blood was collected from C57Bl/6 and Balb/cJ mice into CPDA-1, and platelet rich plasma (PRP) was prepared by gentle centrifugation. WBCs were isolated from the remainder of the blood and were added back to a portion of the PRP to generate either WBC-enriched or WBC-poor PRP. These products were either left untreated or pathogen reduced using the Mirasol pathogen reduction technology system, which uses a combination of riboflavin and UV illumination. These products were transfused via tail vein injection into Balb/cJ mice. Two weeks after transfusion the treated mice were sacrificed, and peripheral blood and spleens were collected. Serum levels of circulating alloantibodies were measured by flow cytometry. Splenocytes were cultured for 48 hours in the presence or absence of C57Bl/6 splenocytes, and levels of secreted cytokines were measured in culture supernatants using multiplexing techniques. Groups were compared using one-way ANOVA with Tukey's multiple comparison post-test, α=0.05. Results: Mice given allogeneic PRP transfusions had significantly elevated levels of alloantibodies compared with non-transfused control mice, whereas mice given syngeneic PRP or pathogen reduced PRP did not. Mice given either the WBC-enriched PRP or WBC-poor PRP generated alloantibodies, though higher levels of antibodies were observed with WBC-enriched PRP. Levels of IFN-γ, TNF-α, IL-10 and GM-CSF were significantly higher following secondary allogeneic challenge of cells from mice given untreated allogeneic PRP compared with those given no transfusion or syngeneic PRP, but not with those given pathogen reduced PRP. Levels of IL-1β, IL-4, IL-5, IL-6, IL-12(p70), and IL-13 were significantly reduced following secondary allogeneic challenge of cells from mice given pathogen reduced allogeneic PRP compared with those given no transfusion or syngeneic PRP. Conclusions: Treatment of allogeneic PRP with riboflavin and UV light prior to transfusion blocks alloimmunization in mice. Furthermore, secondary cytokine responses to allogeneic cells ex vivo are reduced, in some cases bellow the levels observed in cells from mice without prior exposure, suggesting induction of tolerance. Disclosures: Marschner: CaridianBCT Biotechnologies: Employment. Goodrich:CaridianBCT Biotechnologies: Employment. Norris:CaridianBCT Biotechnologies: Consultancy, Research Funding.

Description: Background: CXCR4 is a chemokine receptor overexpressed in more than 20 tumor types, including malignant plasma cells. The CXCR4/CXCL12 (SDF-1) axis has been known for many years as a critical regulator of tumor proliferation, cell, as well as migration into and out of the bone marrow. Ulocuplumab (BMS- 936564) is a first in class, fully human IgG4 monoclonal anti-CXCR4 antibody which inhibits the binding of CXCR4 to CXCL12. This study aimed to determine the safety, tolerability, pharmacokinetics, pharmacodynamics, and clinical activity of Ulocuplumab alone and in combination with lenalidomide plus dexamethasone (Len-Dex), or in combination with bortezomib plus dexamethasone (Bor-Dex) in subjects with relapsed/refractory multiple myeloma. Patients / Methods: Patients were eligible for this trial if they were 18 years of age or older with relapsed or relapsed/refractory multiple myeloma after having received at least 2 prior lines of treatment. Patients in whom who both lenalidomide and bortezomib had failed were not excluded from re-treatment with the same regimen. Patients were enrolled at four cancer centers in the U.S. from October 2011 to March 2014. Ulocuplumab (1, 3 and 10 mg/kg) was dose escalated with a 3-plus-3 design with doses of Len-Dex or Bor-Dex to identify maximum tolerated dose (MTD). Ulocuplumab was given weekly in combination with either 25mg lenalidomide on days 1-21 and 40mg oral dexamethasone on days 1, 8, 15, and 22 of the 28-day cycles on Arm A or 1.3 mg/m2 bortezomib on days 1, 4, 8, and 11 and 20mg oral dexamethasone on days 1, 2, 4, 5, 8, 9, 11, and 12 of the 21-day cycles on Arm B since cycle 2. The primary endpoints for this study were dose-limiting toxicities. Other key safety endpoints included incidence of adverse events (AE), AEs leading to discontinuation, SAEs, deaths, and laboratory abnormalities. The efficacy endpoints included overall responses, duration of response, and time to response. Responses were assessed using the IMWG criteria. Results: Forty-six patients were enrolled (median age, 60 years; range, 53-67). The median number of prior therapies was 3 (range, 1-11), with 70.0% of patients having received ≥ 3 lines of treatment. Ulocuplumab was escalated to a maximum of 10 mg/kg without reaching MTD. The most common treatment-related adverse events of any grade were neutropenia (13 patients, 43.3%), diarrhea (10 patients, 33.3%), thrombocytopenia (10 patients, 33.3%), and fatigue (7 patients, 23.3%) in Arm A; and thrombocytopenia (6 patients, 37.5%), fatigue (4 patients, 25.0%) and anemia (4 patients, 25.0%) in Arm B. The overall response rate (≥ partial response) for all subjects in escalation and expansion was 44.4% (20/45). The median time to response was 1.5 months (range 0.4-7.8 months) for Arm A and 1.0 month (range 0.5-3.7 months) for Arm B, respectively. Of note, the combination of Ulocuplumab with Len-Dex showed a high response rate of 55.2% and a clinical benefit rate ( ≥ minimal response) of 72.4%, including patients who have been previously treated with lenalidomide. Conclusion: This study shows that the blockade of the CXCR4-CXCL12 axis by Ulocuplumab is safe and has an encouraging response rate of over 50% in the Len-Dex arm of patients with relapsed/refractory myeloma. The distinct mechanisms of action of this antibody, as well as its non- cross resistance with currently approved approaches, make it a new class of anti-myeloma drug that warrants further exploration and evaluation in future clinical trials. Disclosures Ghobrial: Takeda: Consultancy; Celgene: Consultancy; BMS: Consultancy; Janssen: Consultancy. Richardson:Takeda: Membership on an entity's Board of Directors or advisory committees, Research Funding; Janssen: Membership on an entity's Board of Directors or advisory committees; BMS: Research Funding; Celgene: Membership on an entity's Board of Directors or advisory committees, Research Funding; Karyopharm: Membership on an entity's Board of Directors or advisory committees; Oncopeptides: Membership on an entity's Board of Directors or advisory committees; Jazz Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees, Research Funding; Amgen: Membership on an entity's Board of Directors or advisory committees. Anderson:Celgene: Consultancy; Takeda Millennium: Consultancy; Bristol Myers Squibb: Consultancy; Gilead: Membership on an entity's Board of Directors or advisory committees; Oncopep: Equity Ownership; C4 Therapeutics: Equity Ownership. Becker:GlycoMimetics: Research Funding.

Description: Abstract 1123 Introduction: Platelet concentrates develop biologically active compounds during storage which may play a role in adverse events of transfusion. Although many studies have focused on release of soluble pro-inflammatory compounds, changes in cells such as platelets may contribute to the pro-inflammatory effects of transfusion products. We evaluated untreated and Mirasol Pathogen Reduction Technology (PRT) treated platelet concentrates for expression of P-selectin and interactions between platelets and PMNs. Methods: Four, double apheresis platelet products were collected from healthy volunteers with TRIMA system under an IRB approved protocol. One product of each pair was PRT treated with Mirasol PRT and both were stored under standard conditions. At various times, aliquots were sterilely removed from products. Expression of P-selectin on platelets was defined with a specific antibody. Neutrophils, isolated from ABO type specific peripheral blood of volunteers, were incubated with platelet concentrates for 3 min at 37° C, and labeled CD41 was added. PMNs were identified with flow cytometry by forward/side scatter and platelets by fluorescence and the % of PMNs associated with platelets determined. Inhibition of platelet/neutrophil interaction with antibodies to adhesion molecules was also examined. In parallel experiments, activation of neutrophils after incubation with platelets was determined by oxidation of dihydrorhodamine (DHR). Results: During storage, platelet expression of P-selectin increased in both untreated and Mirasol treated platelet concentrates (p

Description: Abstract 2288 Introduction Platelet concentrates develop biologically active compounds during storage which may play a role in adverse events of transfusion. Although many studies have focused on release of soluble pro-inflammatory compounds, changes in cells such as platelets may contribute to the response or pro-inflammatory effects of transfusion products. In previous studies we have shown that pathogen reduction with Mirasol PRT of apheresis PLT concentrates induced changes in PLTs which increased during storage including expression of P-selectin and the capacity to form PLT-PMN aggregates. These changes were also associated with increased adherence of stored PLTs in a microfluidic chamber. In the current study we evaluated P-selectin and PLT-PMN aggregate formation in whole blood after treatment with Mirasol PRT. Methods Ten units of whole blood from healthy donors were drawn into CPD under an IRB approved protocol. Five units where treated with Mirasol PRT and five units remained untreated. Aliquots were taken before and after treatment (or at same times for untreated units) on Day 0 and 24–27 hours after draw on Day 1 after storage at 22–24°C. Platelet rich plasma (PRP) was produced by standard technique and PLTs isolated on a Sepharose 2B column. PLTs were incubated with APC-CD62P and FITC-CD41a for comparison with P-selectin expressed as percent positive increase over isotype control. PMNs were isolated from 50 ml of heparinized peripheral blood drawn from healthy, ABO-matched donors. After a 5 min pre-incubation at 37°C in a shaking water bath, untreated, treated PLTs, and PMNs were incubated separately or together for 3 min then quenched at 4°C. FITC-CD41a and FITC-IgG1 isotype for platelet-PMN aggregate quantitation or PE-CD11b for CD11b expression on neutrophils were added. Platelet-PMN aggregates was expressed as percent of all PMN events above CD41a isotype control. CD11b expression was determined for PMNs after exposure to PLTs by flow cytometry. Results P-selectin positive cells did not change significantly over time in samples from untreated products (Table 1). After Mirasol PRT treatment, cells positive for P-selectin increased on Day 0 and 1 (p

Description: Abstract 2498 Diffuse large B-cell lymphomas (DLBCL) account for approximately 40% of lymphomas in adults, with the activated B-cell lymphoma (ABC) subtype being the least curable. ABC lymphoma cells display the phenotype of activated B-cells, which is induced by constitutive activation of the transcription factor Nuclear Factor-kappa B (NF-κB). NF-κB activation in ABC lymphoma can result from several different mutations or abnormal expression of proteins upstream of NF-κB nuclear translocation. No matter the mechanism of NF-κB constitutive activation, the resulting gene expression pattern confers an anti-apoptotic and pro-survival advantage to B-cells, hence driving the oncogenesis and supporting the survival of ABC lymphomas. Therefore, inhibiting NF-κB activity is an attractive strategy for the treatment of ABC lymphomas. Using a cell line with a reporter for NF-κB transcriptional activity in a high throughput screen of 180,000 compounds we discovered 12 compounds that inhibited NF-κB activation, suggesting these compounds negatively regulate NF-κB. Since ABC lines are generally more dependent on NF-κB signalling for cell survival than are the other types of B-cell lymphoma, the hits from the primary screen were tested in a secondary screen for the ability to selectively inhibit the growth of ABC lymphoma cells. Of the 12 hits, two compounds belonging to the same quinolone chemotype were found to selectively inhibit the growth of an ABC line compared to a non-ABC line and normal human peripheral blood mononuclear cells (PBMCs). Three more structurally related quinolones were obtained to investigate a possible limited structure activity relationship for this class of molecules, designated here as Quinolone Inhibitors of NF-κB (QINs). QIN 1 was significantly more potent (Figure A and B) and selective (Figure B and C) relative to other QINs. The limited structure activity relationship suggests that two structural regions of the chemotype may be important for potency and for ABC selectivity, hence providing impetus to further investigate QINs as possible ABC lymphoma drugs. QIN1 is more potent in inhibiting the growth of ABC lines than a known inhibitor of NF-κB activity, a commercially available selective IKK inhibitor (CAS 507475-17-4). Active IKK causes degradation of IκBα, the natural inhibitor of NF-κB, hence IKK inhibitors prevent NF-κB activation by preventing degradation of IκBα. In addition to being more potent, QIN1 retains similar ABC selectivity as the IKK inhibitor (Figure C). QIN1 and the IKK inhibitor both cause apoptosis at a similar rate and both cause G1 arrest in ABC lines at equi-toxic concentrations, initially suggesting similar mechanisms of action. Subsequently, QIN1was found to inhibit NF-κB in several different assays using the IKK inhibitor as a positive control. First, QIN1 inhibited the activation of a transcription based NF-κB reporter cell line in response to LPS, an NF-κB activator. Supporting these results, QIN1 inhibited cytokine release from human PBMCs stimulated with LPS. In addition, QIN1 prevented degradation of IκBα in response to NF-κB activating stimuli, further demonstrating the ability of QIN1 to inhibit NF-κB activity. Finally, QIN1 inhibited nuclear translocation of active NF-κB, thus preventing pro-survival gene expression. The QINs studied here all contain an alpha-beta unsaturated ketone, an electrophilic chemical moiety known to interact with cysteine thiols. Compounds containing similar electrophilic groups are known to bind a cysteine thiol in IKK, preventing its activity and hence inhibiting NF-κB activation. This suggests that this electrophilic moiety in QINs maybe responsible for the NF-κB inhibition observed in these cell lines. The presence of this electrophilic group is not necessarily detrimental to normal cells as we have shown with QIN1 in vitro (Figure A-C) and in vivo (large daily doses of QIN1 cause no observable toxicities in mice). Overall, our data indicate QIN1 inhibits IKK, a kinase immediately upstream of NF-κB nuclear translocation, allowing the majority of ABC lymphomas to be treated irrespective of the upstream mechanism of pathway activation. The selectivity for inhibition of ABC lymphoma cells by QIN1 and our in vitro data showing synergy with an inhibitor of B-cell receptor signalling, which also promotes ABC survival, provides the impetus for further preclinical development of QINs. Disclosures: No relevant conflicts of interest to declare.

Description: Abstract 3867 Introduction: Despite their mature appearance, the B cells from chronic lymphocytic leukemia (CLL) possess immature characteristics both functionally and biochemically. CLL B cells display known biochemical markers characteristic of cells early in the blood lineage, including ROR1, Wnt16, and LEF1. In addition, CLL B cells have higher levels of Reactive Oxygen Species (ROS) and of the oxidant-induced transcription factor Nrf2 [NFE2L2], compared to normal peripheral blood mononuclear cells (PBMC). Intracellular ROS status has been suggested to be a marker of cancer stem/progenitor cells possibly due to their high expression of oncogenes. Downstream targets of Nrf2 include the Aldehyde dehydrogenase [ALDH] enzymes, which are believed to play a crucial role in stem cell biology because they protect the cells against oxidative stress caused by accumulation of aldehydes. Here, we use ALDH activity to visualize populations of CLL B cells that may have stem/progenitor properties. Materials and Methods: Isolated PBMC from normal donors and CLL patients with aggressive and indolent disease were stained for ALDH activity with an Aldefluor assay kit (StemCell Technologies). The ALDH inhibitor, diethylaminobenzaldehyde (DEAB), was used to confirm that the fluorescent activity was due to ALDH activity. At the end of the Aldefluor assay, the cells were stained for cell surface markers, CD19, CD5, CD38 and CD34. 50,000 total events were collected for FACS analysis. Normalized Mean Fluorescence Intensity (MFI) values were calculated by dividing each MFI value to average MFI value of normal CD19+ cells for each experiment. Data analyses were performed by FlowJo software and Prizm. P-values were calculated by One-Way ANOVA analysis with Post-Bonferroni's multiple comparison test. Results: We examine the level of ALDH expression and activity in CD19+ cells of healthy donors (n = 9), CLL samples that expressed unmutated IgVH and that were ZAP-70 positive (defined as “aggressive”, n = 14) or samples that expressed mutated IgVH and were ZAP-70 negative (defined as “indolent”, n=12). CLL B cells from patients with aggressive disease had significantly higher ALDH activities compared to normal B cells (p 〈 0.001) and indolent CLL B cells (p 〈 0.05) (Figure1). Indolent CLL B cells also have higher level of ALDH activities compared to normal B cells (p 〈 0.01) (Figure1). Treatment with the ALDH inhibitor, DEAB, suppressed the increased fluorescence observed in CLL B cells. In addition, ALDH high CLL B cells are CD34 negative. These data show that CLL B cells express a marker known to be associated with stem/progenitor cells, but these populations are different from CD34 positive hematopoietic stem cells. In addition, our data show that a stem/progenitor cell marker is associated with the pathogenesis of CLL. Disclosures: Kipps: Igenica: Equity Ownership, Membership on an entity's Board of Directors or advisory committees; Celgene: Consultancy, Research Funding; Abbot Industries: Research Funding; Pharmacyclics: Membership on an entity's Board of Directors or advisory committees; Genentech: Research Funding; GSK: Research Funding; Gilead Sciences: Consultancy, Research Funding; Amgen: Research Funding.

Description: Abstract 1786 The Wnt/beta-catenin pathway is highly active in chronic lymphocytic leukemia (CLL) and confers an anti-apoptotic effect in vitro and possibly also in vivo. As such, inhibition of this pathway represents a potential therapeutic target. Here we report preclinical studies using agelastatin A (AgA), a naturally occurring alkaloid extracted from the marine sponges Agelas dendromorpha and Cymbastella sp. We tested AgA using SW480 cells transfected with a beta-catenin dependent reporter gene expression system. Using this assay, we found that AgA is a potent Wnt signaling inhibitor with IC50 of 12nM. AgA also inhibits the expression of reporter genes in HEK293 cells cotransfected with either Wnt1 or mutated (dominant-active) beta-catenin, suggesting that its mechanism of action is independent of the beta-catenin degradation complex. Moreover, real time-PCR results show that Lef1, a classic Wnt/beta-catenin target gene highly expressed in CLL, is down-regulated in primary CLL cells incubated with AgA at nanomolar concentrations. AgA, but not structurally related compounds agelastatin C and agelastatin D, selectively induces apoptosis in CLL B-cells (mean IC50 = 56nM) compared with peripheral blood mononuclear cells from healthy volunteers (mean IC50 = 250nM). Interestingly, AgA induces apoptosis at nanomolar concentrations even in samples from CLL patients who had no clinical response to fludarabine, samples with 17p deletion or TP53 gene mutations, and samples in which p53 deficiency was determined by in vitro chemoresistance and absence of inducible p21, CD95, and DR5 after irradiation (Figure 1). In addition, AgA induces apoptosis on CLL cells that are maintained in co-culture conditions with stromal cells, which typically increases leukemia cell viability. This suggests that AgA is capable of disrupting pro-survival signals derived from the microenvironment, including Wnt mediated activation. In conclusion, AgA has potent activity against CLL cells in vitro. Our studies show that AgA inhibits Wnt/beta-catenin signaling at nanomolar concentrations, induces apoptosis in CLL cells independently of p53, and is able to disrupt pro-survival signaling derived from stromal cell support. AgA warrants further studies and clinical development for the treatment of CLL and potentially other malignancies associated with Wnt/beta-catenin signaling. Disclosures: No relevant conflicts of interest to declare.

Description: Background: Across sub-Saharan Africa, blood supplies are threatened by numerous pathogens. In some locations, Plasmodium parasitemia prevalence in donor blood is nearly 50%. Donor testing for malaria in these areas is not effective and the risk of transfusion-transmitted malaria (TTM) is high. The Mirasol® PRT System for Whole Blood (WB) is a medical device intended for extracorporeal pathogen reduction of WB. The current clinical study evaluated the ability of Mirasol-treated WB to reduce the incidence of TTM. Study Design/Methods: This was a prospective, randomized, double-blind, controlled, single-center study in Ghana, which is hyperendemic for malaria. The study had 90% power to demonstrate a 90% reduction in TTM. Hospitalized patients requiring WB transfusions were randomly allocated to receive ≤ 2 transfusions of standard (untreated) or Mirasol-treated WB. The primary endpoint was the incidence of TTM as measured by quantitative polymerase chain reaction and Plasmodium alleleic sequence homology between transfused and patient WB during 28 days of follow-up. Patient safety was assessed by monitoring treatment-emergent adverse events (TEAEs) and transfusion reactions.Clinical outcomes related to hemoglobin increments, hemostatic parameters, and clinical chemistries were monitored for 28 days post-transfusion. Results: Overall, 226 subjects (113 Mirasol, 113 Untreated) were enrolled; 223 subjects were included in the safety analysis. Sixty-five (65) subjects were non-parasitemic at pre-transfusion (28 Mirasol, 37 Untreated) and received at least 1 parasitemic WB transfusion. Of 16 cases of suspected TTM (3 Mirasol, 13 Untreated) with 2 consecutive days of parasitemia, 9 were confirmed by alleleic homology (1 Mirasol, 8 Untreated). Incidence of TTM was significantly reduced in patients receiving treated products. Hemoglobin (mean [standard deviation]) was similar between groups at baseline (6.71 g/dL; p = 1.0), and Day 1 following 1 transfusion (8.53 [2.0] vs 8.49 [1.5] g/dL; p = 0.93) or 2 transfusions (7.09 [1.5] vs 7.38 [1.6] g/dL; p = 0.33). Ninety-two subjects (48 Mirasol, 44 Untreated) reported 145 TEAEs (75 Mirasol, 70 Untreated). Transfusion reactions were observed in 8.1% and 13.4% of subjects receiving Mirasol-treated and untreated WB, respectively. Table. Incidence of TTM Mirasol n (%); 95% CI Untreated n (%); 95% CI P-Value 2 Consecutive days of ParasitemiaN = 65 3 (10.7); 2.3, 28.2 n = 28 13 (35.1); 20.2, 52.2n = 37 〈 0.05 2 Consecutive days of Parasitemia and 〉2 Allele match by PCRN = 65 1 (3.6); 0.1, 18.3n = 28 8 (21.6); 9.8, 38.2n = 37 〈 0.05 ITT PopulationN = 223 1 (0.9); 0.0, 4.9n = 111 8 (7.1); 3.1, 13.6n = 112 〈 0.05 Abbreviation: CI = confidence interval, ITT = intent-to-treat, PCR = polymerase chain reaction. Conclusions: The primary endpoint of the study was met. Mirasol treatment of WB clinically and statistically reduced TTM infections in the study population. This was the first human clinical study demonstrating that a PRT system can reduce transmission of a bloodborne pathogen. No safety issues were related to the device or device-treated WB. Transfusion reactions did not differ between patients receiving Mirasol-treated or untreated WB. Hemoglobin increments and transfusion outcome parameters in transfused patients did not differ between the treatment groups. Disclosures Allain: Terumo BCT: Consultancy. Owusu-Ofori:Terumo BCT: Other: Clinical Study Sub-Investigator. Marschner:Terumo BCT: Employment. Goodrich:Terumo BCT: Employment. Owusu-Ofori:Terumo BCT: Other: Clinical Study Investigator.