ALBERT

Description: Abstract 3615 Introduction: Preferentially expressed antigen of melanoma (PRAME) was first isolated as a human melanoma antigen by cDNA expression cloning using melanoma-reactive cytotoxic Tcells (CTL). PRAME is a tumor associated antigen (TAA) of particular interest since it is widely expressed by lymphoid and myeloid malignancies and solid tumors. Several studies have associated high PRAME RNA levels with good prognosis in acute myeloid leukemia (AML). In addition, several authors have suggested that PRAME could be used as a target for anticancer T-cell therapy. PRAME expression is regulated at the epigenetic level. For this reason inhibitors of DNA methylation, such as 5-azacytidine, can modulate the expression of this TAAs. In the current study we analyzed the effect of 5-azaC on the expression of PRAME in blasts versus CD34+ cells from healthy donors in an attempt to increase its expression, thus inducing a potential target for therapeutic strategies. Methods: We analyzed PRAME mRNA expression of blast cells from AML patients at diagnosis versus CD34+ stem cells from healthy donors by RT-PCR without treatment or after exposure to 1mM 5-azaC during the four days of culture and correlated the expression of PRAME with the methylation status of the promoter. Results: PRAME is significantly over-expressed in blasts from AML patients (n=11) compared with normal CD34+ cells (n=8) ((700±1102 vs. 1.8±2.5 p=0.002). Interestingly, we found an inverse correlation between PRAME expression and the degree of methylation in the promoter among both AML samples and healthy donors (r=-0.77 p=0.010). In order to evaluate the effect of 5-azaC on PRAME gene expression, we treated blast cells and CD34+ cells from healthy donors with the drug and we observed that the exposure to the drug induced a decrease in the percentage of methylation in the promoter and subsequently increased the expression of PRAME but, interestingly, the higher the basal methylation of the promoter the more intense the effect of the drug among AML cells. By contrast, CD34+ cells from healthy donors were resistant to the effect of the drug so that no significant changes were observed neither in terms of methylation status of the promoter nor in the expression of PRAME prior to or after exposure to the drug among healthy donors. Conclusions: The promoter region is highly methylated in normal CD34+ cells compared to AML cells and this pattern correlates with a higher expression of PRAME in blasts. Furthermore, the level of PRAME methylation was reduced in AML patients after exposure to 5-azaC which correlated with an increase in the expression of PRAME. By contrast, the effect of 5-azaC on the methylation pattern of the promoter was significantly lower in CD34+ cells from healthy donors. Disclosures: Cañizo: Celgene: Membership on an entity's Board of Directors or advisory committees. San Miguel:Celgene: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees; Jangssen-cilag: Membership on an entity's Board of Directors or advisory committees; millennium: Membership on an entity's Board of Directors or advisory committees. Off Label Use: The drug used in this study is the demethylating agent 5-azacytidine (5-azaC) and the purpose is to increase PRAME expression in blasts from AML patients and generate CTL CD8+ specific response against tumor cells.

Description: Background: CC-122, a first in class PPM™ pleiotropic pathway modifier, has anti-tumor activity against B cell lymphomas. The molecular target of CC-122 is cereblon (CRBN) and CC-122 promotes ubiquitination of lymphoid transcription factor Aiolos in a CRBN-dependent manner, leading to its degradation in Diffuse Large B Cell Lymphoma (DLBCL) tumor tissue and immune cells. CC-122 also depletes Ikaros, which is expressed in immature stages of myeloid differentiation and regulates early neutrophil differentiation (Blood 101:2219 2003). Following establishment of CC-122 3mg daily (QD) as the maximum tolerated dose (MTD) on a continuous schedule (Blood 122:2905 2013), subjects with advanced lymphoma, myeloma, and select solid tumors were enrolled in parallel expansion. In DLBCL subjects, CC-122 treatment demonstrated promising clinical efficacy, however, dose reductions due to neutropenia were frequent with the QD schedule (Blood 124:3500 2014). Therefore, a second cohort of DLBCL subjects was enrolled to evaluate the tolerability and clinical activity of intermittent schedules. Methods: Subjects with relapsed/refractory DLBCL were enrolled in parallel dose escalation of CC-122 given orally at 4mg or 5mg on two intermittent schedules. CC-122 given 21/28 days was tested based on lenalidomide experience. In order to model a second schedule, human bone marrow CD34+ cells were cultured for two weeks in SCF, Flt3L and G-CSF for expansion towards granulocytic lineage followed by 6 days with media plus G-CSF for neutrophil maturation.CC-122 0.5 uM was added continuously or on a 5 out of 7 day (5/7d) schedule. Myeloid maturation stages were measured 14 days later by CD34, CD33 and CD11b flow cytometry. Continuous exposure to CC-122 led to reversible myeloid maturation arrest and 90% decreased mature neutrophils compared to vehicle, whereas, CC-122 exposure for 5/7d resulted in only 50% decreased mature neutrophils. Based on this rationale, CC-122 given 5/7d was selected as the second intermittent schedule tested in DLBCL. Results: As of June 25, 2015, 22 subjects with relapsed/refractory DLBCL were enrolled in the 2nd cohort; all were evaluable for safety, 16 were efficacy evaluable (EE) as of the cutoff date. The median age was 60 years and 54% were male. The median time since diagnosis was 14 months and all subjects were ECOG 0-1. For subjects treated with CC-122 4mg 21/28 days (N=3), there were no dose limiting toxicities (DLTs) in cycle 1, however, all subjects required dose reduction due to neutropenia and therefore this dose level was considered a non-tolerated dose (NTD). For subjects treated with CC-122 on a 5/7 days schedule, the NTD was at 5mg due to 2 DLTs in 2 of 5 subjects (grade 3 febrile neutropenia and grade 3 pneumonitis). CC-122 4mg was the MTD on 5/7d and was selected for ongoing expansion in up to 50 subjects (N=14 as of cutoff date). There were no DLTs in 12 DLT-evaluable subjects. Median relative dose intensity achieved for 4mg 5/7d vs 3mg QD was 99% vs 79%. The most common (≥ 10%) related adverse events (AEs) were neutropenia (36%), constipation (29%), asthenia (21%) and grade 3/4 related AEs were neutropenia (36%) and lipase elevation (14%). In addition, drug-related serious AEs included pneumonia, neck pain, and respiratory failure. AEs were an uncommon cause of discontinuation (7%, n=14). Response rates for the EE DLBCL subjects treated at 5mg 5/7d (N=3), 4mg 5/7d (N=10), and 3mg QD (N=22) was 67% (2 PR), 30% (1CR, 2 PR) and 23% (1CR, 4PR), respectively. Aiolos protein levels in peripheral T cells was measured by flow cytometry pre (baseline) and 5 hours post dosing on C1D1, C1D10 and C1D22. The median % change Aiolos levels at each of these visits were -47, -28 and -52%, respectively, indicating that Aiolos degradation occurs throughout the cycle. In addition, the median increase from baseline in cytotoxic memory T cells and helper memory T cells at cycle 1 day 22 in peripheral blood samples was 580% and 76%, respectively. Conclusion: In an in vitro myeloid differentiation assay, myeloid maturation arrest by CC-122, possibly due to Ikaros degradation, can be partially bypassed with a 2 day drug holiday. From a clinical standpoint, exploration of intermittent dosing confirmed that 5/7d schedule mitigates neutropenia-related dose reductions and improves CC-122 clinical activity in relapse/refractory DLBCL patients. Of note, the immunomodulatory effects of CC-122 are maintained on the 5/7d schedule. Disclosures Carpio: Celgene: Research Funding. Off Label Use: CC-122 is a first in class PPM(TM) pleiotropic pathway modifier with anti-tumor activity against B cell lymphomas.. Ysebaert:Celgene: Research Funding. Cordoba:Celgene: Research Funding. Santoro:Celgene: Research Funding. López-Martín:Celgene: Research Funding. Sancho:Celgene: Research Funding. Panizo:Celgene: Research Funding; Roche: Speakers Bureau; Janssen: Speakers Bureau; Takeda: Speakers Bureau. Gharibo:Celgene: Research Funding. Rasco:Asana BioSciences, LLC: Research Funding; Celgene: Research Funding. Stoppa:Amgen: Consultancy, Honoraria; Janssen: Consultancy, Honoraria; Novartis: Consultancy, Honoraria; Celgene: Consultancy, Honoraria, Research Funding. Damian:Celgene: Research Funding. Wei:Celgene: Employment, Equity Ownership. Hagner:Celgene: Employment, Equity Ownership. Hege:Celgene Corporation: Employment, Equity Ownership. Carrancio:Celgene: Research Funding. Gandhi:Celgene: Employment, Equity Ownership. Pourdehnad:Celgene: Employment, Equity Ownership. Ribrag:Esai: Membership on an entity's Board of Directors or advisory committees, Research Funding; Pharmamar: Honoraria, Membership on an entity's Board of Directors or advisory committees; Gilead: Membership on an entity's Board of Directors or advisory committees; Celgene: Research Funding; Servier: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding.

Description: Abstract 2771 Introduction: We have previously shown that 5-azaC inhibits T-cells proliferation and favours the development of Tregs which decreases the risk of GVHD after allogeneic transplantation. This is at least in part due to the effect of the drug on the expression of genes such as FOXP3. Nevertheless, considering the unspecific effect of 5-azaC, it could also favour the overexpression of other genes related to the regulation of the immune response such as TBET, GATA3, IFNg or IL-2, which in turn would favour the development of a Th1, Th2 or Th17 polarization instead of a Treg expansion. In the current study we have evaluated the effect of 5-azaC on these genes in order to know the mechanisms involved in the effect of the drug on the immune response. Methods: We analyzed TBET, GATA3, FOXP3, IFNg and IL-2 mRNA expression of T lymphocytes by RT-PCR after exposure to 1mM 5-azaC during eleven days of culture. These T cells were cultured in medium alone or stimulated with plate-bound anti-CD3 (5 mg/ml) plus soluble anti-CD28 (2.5 mg/ml). Furthermore, we analyzed the methylation status of the promoters of these genes before and after 5-azaC treatment. Results: The expression of TBET, GATA3 and RORγ is not significantly affected by the exposure to the drug whereas the expression of FOXP3 significantly increases along the culture. Regarding IFNg and IL-2 expression no increased expression was observed after exposure to the drug at different time-points along the 11 days of culture. Upon analyzing the mathylation status of the promoter of these genes, we observed that in steady state the promoter of TBET and GATA is demethylated, which is in contrast to FOXP3 promoter. For this reason, the exposure to the drug decreases the methylation status of the promoter of FOXP3 while there is no effect on the promoters of TBET or RORg, thus justifying the absence of effect on the expression of these genes. By contrat, the promoter of both IFNg and IL-2 is methylated prior to the exposure to 5-azaC and it is demethylated after exposure to the drug, which is in contrast to the absence of increased expression of these genes. Accordingly, other mechanisms in addition to the epigenetic regulation of the promoter of IFNg and IL-2 are responsible for their expression in this model. Conclusions: In the current study we show by the first time the effect of 5-azaC on the promoters of genes which regulate the immune response. While no effect was observed for TBET, and GATA3 5-azaC induces a strong demethylation in the promoter of IFN or IL-2. In spite of this effect there is no increase in their expression which could be due to the overexpression of FOXP3 or to additional mechanisms involved in their regulation which are currently being evaluated. Disclosures: Cañizo: Celgene: Membership on an entity's Board of Directors or advisory committees. San Miguel:Celgene: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees; Jangssen-cilag: Membership on an entity's Board of Directors or advisory committees; millennium: Membership on an entity's Board of Directors or advisory committees. Off Label Use: The drug used in this study is the demethylating agent 5-azacytidine (5-azaC) and the purpose is the inhibition of graft versus host disease.

Description: Abstract 397 Mesenchymal stromal cells (MSC) are closely related to the regulation of hematopoietic stem cell niche. Recently, Raaijmakers et al (Nature, 2010), published that deletion of Dicer1, a RNase III enzyme involved in microRNA biogenesis, in murine MSC-derived osteoprogenitors triggered peripherical blood cytopenias, myelodysplasia and subsequent AML, showing that molecular alterations in bone marrow microenvironment could result in clonal impaired haematopoiesis. Here, we have investigated whether MSC from myelodysplastic syndrome (MDS) patients show differences in DICER1 and DROSHA, another RNA III endonuclease, in comparison to healthy MSC. In addition, we have analyzed several hematopoietic-related microRNAs in these same samples. Bone marrow MSC from MDS patients (n=35; 10 5q- syndrome, 4 RA, 5 RARS, 10 RCMD, 3 RAEB, 2 MDS-U and 1 hypocellular MDS) and healthy donors (HD, n=20) were isolated and in vitro expanded following standard procedures until the third passage. Additionally, paired mononuclear cells (MNC) from 13 MDS and 8 HD were obtained. Total RNA was isolated using TRIzol reagent (Invitrogen). DICER1 and DROSHA relative gene expressions were assessed by quantitative PCR (Q-PCR) using commercial TaqMan® assay (Applied Biosystems®) with GAPDH as control gene. DICER1 and DROSHA (Abcam) protein expression were evaluated in whole cell lysates by western blot, using calnexin (Stressgen) as control. Several microRNAs with known role in hematopoiesis and immune system regulation were analyzed in 25 MDS and 12 HD by Q-PCR using commercial TaqMan® MicroRNA assay (Applied Biosystems®) with RNU43 as control microRNA. MSC from MDS showed significant lower DICER1 (0.0035±0.0020 vs. 0.0076±0.0092; p=0.044) and DROSHA (0.0070±0.0028 vs. 0.0135±0.0176; p=0.019) gene expression levels than healthy controls. Moreover, MSC from MDS showed lower protein expression of both DICER1 and DROSHA by western blot analysis, confirming Q-PCR findings. By contrast, no difference in either DICER1 (0.0197±0.0151 vs. 0.0173±0.0112; p=0.9) or DROSHA (0.0089±0.0023 vs. 0.0067±0.0037; p=0.09) gene expression were observed between MNC from MDS and HD. As far as microRNA expression, we observed a lower expression of mir-155 (0.63±0.92 vs. 0.94±0.49; p=0.007) and mir-181a (1.30±0.95 vs. 2.02±1.05; p=0.041) in MSC from MDS in comparison to healthy controls. Mir-155 and mir-181a are involved in T-cell and B-cell differentiation, while mir-155 are also related to erythroid and megakarycytic differentiation. We conclude that MSC from MDS patients show lower expression of DICER and DROSHA, two relevant RNA-III endonucleases involved in the microRNA biogenesis, confirming recent findings in murine models. Moreover, the expression of some microRNA is impaired in these cells, raising the possibility that these microenvironmental alterations could be involved in the MDS pathophysiology. Disclosures: No relevant conflicts of interest to declare.

Description: Abstract 3738 Graft-versus-host disease (GVHD) represents a major challenge and the main cause of morbidity and mortality after allogeneic transplantation. Using the standard GVHD prophylaxis based on a calcineurin inhibitor plus methotrexate (MTX). The incidence of acute GVHD is in the range of 30–60%, so that new strategies are required in order to decrease GVHD without hampering GVL. Sirolimus, an mTOR inhibitor, allows to decrease the risk of GVHD and increases the number of Treg after transplantation. Unfortunately, its use may increase the risk of microangiopathy and, moreover, its combination with calcineurin inhibitors blocks the development of Treg. Bortezomib is a proteosome inhibitor and blocks the nuclear translocation and activation of NF-kB. It induces depletion of alloreactive T and allows the expansion of T-cells with suppressive properties. Accordingly, both drugs could favour the development of a tolerogeneic immune response after transplantation. In the current study we have analyzed the synergistic effect of sirolimus together with bortezomib. Bortezomib 100 nM plus sirolimus 5nM synergistically inhibited T-cell activation as assessed by the expression of CD25, production of IFNg and expression of CD40L as well as proliferation assessed as expression of PKH. Remain vibility, these effects could not be attributed to a decreased viability of T-cells, as assessed by 7-AAD, at the concentrations evaluated. As compared to each drug alone, the combination significantly decreased the production of Th1 cytokines (IFNg, IL-2 and TNF) while regarding TH2 cytokines, only IL-6 significantly decreased upon combining both drugs. Concerning the mechanisms involved in this synergistic effect, the combination of both drugs resulted in an inhibition of the Akt and Erk ½ phophorylation, thus indicating that sirolimus inhibit pathways which could allow T-cells to escape from the effect of bortezomib at the doses used in the current experiment. In order to confirm in vivo the synergistic effect of sirolimus and bortezomib, a GVHD mouse model (C57/BL6-Balb/c) was carried out. Mice receiving both drugs (Bortezomib 1μg/day intravenous on days 0, +1, +2 postransplantat and sirolimus 0.25mg/Kg intra-peritoneal on days 0 to 12) has a significantly lower incidence of GVHD and longer survival as compared to each drug alone. We also wanted to evaluate whether the immunosuppressive effect of the combination was unspecific or, by contrast, it allowed induce specific immune tolerance against host but maintaining the immune response against other antigens. For this purpose a haematopoietic cells of Balb/c mice which were C57/BL6 complete chimeras were infused to NOD-SCID mice. While none of the donors had developed GVHD after transplantation plus sirolimus and bortezomib postransplant, the NOD-SCID mice succumbed due to GVHD. Furthermore, we infused WEHI cells to BALB/c after total body irradiation and we observed that, while all BALB/c mice receiving WEHI plus C57BL/6 donor BM cells died due to leukemic infiltration, none of those receiving WEHI cells plus C57BL/6 donor BM cells plus splenocytes (and GVHD prophylaxis with sirolimus and bortezomib) did develop leukemic infiltration, thus confirming that, using this approach, we were able to separate GVHD and GVL effect. In conclusion, the current study shows a potent synergistic effect between sirolimus and bortezomib in vitro and in vivo which prevent GVHD while maintaining GVL. Disclosures: Cañizo: CELGENE: Membership on an entity's Board of Directors or advisory committees. San Miguel:JANSSEN-CILAG: Membership on an entity's Board of Directors or advisory committees; CELGENE: Membership on an entity's Board of Directors or advisory committees; NOVARTIS: Membership on an entity's Board of Directors or advisory committees; MILLENNIUM: Membership on an entity's Board of Directors or advisory committees. Off Label Use: sirolimus and bortezomib are not approved for use in prophylaxis of graft versus host disease.

Description: Treatment options for relapsed/refractory diffuse large B-cell lymphoma (R/R DLBCL) are limited with no standard of care; prognosis is poor, with 4- to 6-month median survival. Avadomide (CC-122) is a cereblon-modulating agent with immunomodulatory and direct antitumor activities. This phase 1 dose expansion study assessed safety and clinical activity of avadomide monotherapy in patients with R/R de novo DLBCL and transformed lymphoma. Additionally, a novel gene expression classifier, which identifies tumors with a high immune cell infiltration, was shown to enrich for response to avadomide in R/R DLBCL. Ninety-seven patients with R/R DLBCL, including 12 transformed lymphoma, received 3 to 5 mg of avadomide administered on continuous or intermittent schedules until unacceptable toxicity, disease progression, or withdrawal. Eighty-two patients (85%) experienced ≥1 grade 3/4 treatment-emergent adverse events (AEs), most commonly neutropenia (51%), infections (24%), anemia (12%), and febrile neutropenia (10%). Discontinuations because of AEs occurred in 10% of patients. Introduction of an intermittent 5/7‑day schedule improved tolerability and reduced frequency and severity of neutropenia, febrile neutropenia, and infections. Among 84 patients with de novo R/R DLBCL, overall response rate (ORR) was 29%, including 11% complete response (CR). Responses were cell-of-origin-independent. Classifier-positive DLBCL patients (de novo) had an ORR of 44%, median progression-free survival (mPFS) of 6 months, and 16% CR versus an ORR of 19%, mPFS of 1.5 months, and 5% CR in classifier-negative patients (P = .0096). Avadomide is being evaluated in combination with other antilymphoma agents. This trial was registered at www.clinicaltrials.gov as #NCT01421524.

Description: Cytokine genes are targets of multiple epigenetic mechanisms in T lymphocytes. 5-azacytidine (5-azaC) is a nucleoside-based DNA methyltransferase inhibitor that induces demethylation and gene reactivation. In the current study, we analyzed the effect of 5-azaC in T-cell function and observed that 5-azaC inhibits T-cell proliferation and activation, blocking cell cycle in the G0 to G1 phase and decreasing the production of proinflammatory cytokines such as tumor necrosis factor-α and interferon-γ. This effect was not attributable to a proapoptotic effect of the drug but to the down-regulation of genes involved in T-cell cycle progression and activation such as CCNG2, MTCP1, CD58, and ADK and up-regulation of genes that induce cell-growth arrest, such as DCUN1D2, U2AF2, GADD45B, or p53. A longer exposure to the drug leads to demethylation of FOXP3 promoter, overexpression of FOXP3, and expansion of regulatory T cells. Finally, the administration of 5-azaC after transplantation prevented the development of graft-versus-host disease, leading to a significant increase in survival in a fully mismatched bone marrow transplantation mouse model. In conclusion, the current study shows the effect of 5-azaC in T lymphocytes and illustrates its role in the allogeneic transplantation setting as an immunomodulatory drug, describing new pathways that must be explored to prevent graft-versus-host disease.

Description: Erythropoiesis, the process of cell proliferation and differentiation that produces erythrocytes, is a tightly regulated process, but apart from early progenitor development and the EPO-dependent response, very little is known about other molecular signals which control cellular fate during RBC production. Members of the transforming growth factor beta (TGFβ) superfamily have been studied as potential regulators of erythropoiesis, iron regulation and globin expression. Sotatercept, an ActRIIA ligand trap, binds to and inhibits activin and other members of the TGFβ superfamily to induce a rapid increase in red cell number and hemoglobin in healthy volunteers. Pharmacological findings demonstrate that RAP-011, a murine ortholog of sotatercept, stimulates RBC parameters in mice through a mechanism distinct from EPO. We conducted the current study to evaluate if RAP-011 may stimulate expansion of a late-stage erythroblast population that is not normally expanded and/or may induce faster differentiation of erythroid precursors. In order to determine if RAP-011 promotes proliferation or differentiation during erythropoiesis, the number of cell divisions was quantified by CFSE staining. During in vitro erythroid differentiation, RAP-011 did not appear to alter the number of cell divisions; however, the percentage of cells that underwent the last division was higher in cultures treated with RAP-011, suggesting that the drug induced faster cellular maturation/differentiation. We also analyzed cell viability of GPA+ cells at the end of the differentiation process and observed that the percentage of apoptotic death was higher in control vs. RAP-011-treated cells. This suggests that RAP-011 may promote survival of late-stage precursors. To assess potential candidates which may mediate the erythropoietic effects of RAP-011, we selected three high affinity RAP-011 ligands, Activin A, Activin B and GDF-11, and proceeded to evaluate their effects on Smad signaling and on erythroid differentiation of human bone marrow progenitors. First, we observed that RAP-011 blocked ligand-induced Smad2/3 phosphorylation in the bone marrow-derived cells. Secondly, RAP-011 rescued activin A-induced inhibition of BFU-E colony formation. Finally, when mature CD36+ cells were differentiated in liquid media containing each of the three ligands, RAP-011 was able to reverse GDF-11- and Activin A-induced inhibition of of erythroid cell proliferation. GDF-11 and Activin A also significantly decreased the percentage of GPA-positive cells in culture, while significantly increasing the percentage of CD45-positive cells. Consistent with proliferation results, RAP-011 blocked these ligand effects. Treatment of CD36+ cells with Activin B did not alter growth or differentiation. These data suggest that GDF-11 and Activin A may contribute, in part, to the erythropoietic stimulatory effects of RAP-011. Several members of the TGFβ superfamily of ligands have been implicated as negative growth regulators, or “chalones”, functioning in homeostasis to maintain specific, mature tissue size. The results from our studies using the ActRIIA-Fc ligand trap, RAP-011, suggest that GDF-11 and Activin A, as well as other sotatercept ligands, may also be “chalones” for the blood, specifically regulating homeostasis of mature RBCs. We suggest that sotatercept increases red blood cell maturation and survival by blocking the negative growth regulation by TGFβ members. In pathologic states such as ineffective erythropoiesis, sotatercept may have an even greater impact than in the healthy, homeostatically-balanced environment. Disclosures: Carrancio: Celgene Corp.: Employment. Markovics:Celgene Corp.: Employment. Wong:Celgene Corp.: Employment. Heise:Celgene: Employment, Equity Ownership. Daniel:Celgene Corp.: Employment, Equity Ownership. Chopra:Celgene: Employment, Equity Ownership. Sung:Celgene Corp.: Employment.