MLN9708 Elicits Pharmacodynamic Response in the Bone Marrow Compartment and Has Strong Antitumor Activity in a Preclinical Intraosseous Model of Plasma Cell Malignancy.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 1834-1834 ◽  
Author(s):  
Edmund Lee ◽  
Bret Bannerman ◽  
Michael Fitzgerald ◽  
Jennifer Terkelsen ◽  
Daniel Bradley ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Antitumor Activity ◽  
Plasma Cell ◽  
Research Funding ◽  
Ex Vivo ◽  
Xenograft Model ◽  
Tumor Burden ◽  
Human Multiple Myeloma ◽  
Cell Malignancy

Abstract Abstract 1834 Poster Board I-860 Introduction The clinical success of VELCADE® (bortezomib) for Injection has validated the proteasome as a therapeutic target for the treatment of human cancer. The novel proteasome inhibitor MLN9708 is a potent, reversible, and specific inhibitor of the b5 site of the 20S proteasome identified in preclinical studies. MLN9708 is currently in human clinical development for both hematological and non-hematological malignancies. Here we describe the pharmacodynamic (PD) response of MLN9708 in the murine bone marrow compartment and its strong antitumor activity in an intraosseous xenograft model of plasma cell malignancy. Materials MLN9708 immediately hydrolyzes to MLN2238, the biologically active form, upon exposure to aqueous solutions or plasma. MLN2238 was used for all preclinical studies described below. Methods It has been previously shown that double transgenic iMycCa/Bcl-XL mice develop de novo plasma cell malignancies (J. Clin. Invest. 113:1763-1773, 2004) in which neoplastic plasma cell development is driven by the targeted expression of the transgene Myc (c-myc; myelocytomatosis oncogene) and Bcl-x (Bcl2l1; encodes the oncoprotein Bcl-XL). DP54 is a plasma cell tumor cell line derived from the bone marrow of a syngeneic mouse previously inoculated with an iMycCa/Bcl-XL tumor (Cancer Res. 67:4069-4078, 2007). In vitro, DP54 cells express both the Myc and Bcl-XL transgenes, various plasma cell and B-cell markers including CD38, CD138 and B220, and has gene expression profile very similar to human multiple myeloma. To establish a preclinical intraosseous model of plasma cell malignancy for efficacy studies, freshly dissociated DP54-Luc cells (constitutively expressing firefly luciferase under a mouse Ig-k promoter) were aseptically injected into the bone marrow space of the upper shaft of the right tibia of NOD-SCID mice. Once tumor growth has been established, mice were randomized into treatment groups and then treated intravenously (IV) with vehicle, bortezomib (at 0.8 mg/kg twice weekly [BIW]) or MLN2238 (at 11 mg/kg BIW) for 3 consecutive weeks. Tumor burden was measured by bioluminescent imaging. Results MLN2238 strongly inhibited proteasome activity in the blood and bone marrow compartments of mice (maximum b5 inhibition of 84% and 83%, respectively). In vivo, when DP54 cells were aseptically injected into the bone marrow space of the mouse tibia, signs of bone erosion in the tibia, femur and cranial sagittal sultures (as determined by ex-vivo mCT imaging) were observed which resembled osteolytic lesions frequently seen in human multiple myeloma. Dissemination of DP54-Luc cells after intratibia inoculations were detected by in vivo bioluminescent and confirmed by ex vivo imaging where luminescent tumor nodules were detected in the spleen, kidneys, intestine, lymph nodes and bones including right tibia, spine and cranium. To assess the antitumor activity of MLN2238 in the bone marrow compartment, an efficacy study was performed using the DP54-Luc intraosseous xenograft model of plasma cell malignancy. Tumor burden (bioluminescence), osteolytic lesions (mCT) and overall survival after treatment with bortezomib and MLN2238 will be presented. Conclusion The novel proteasome inhibitor MLN9708 demonstrates strong activity in the bone marrow compartment in vivo. MLN9708 is currently in human clinical development for both hematological and solid tumor indications. Disclosures Lee: Milllennium: Employment, Equity Ownership. Bannerman:Milllennium: Employment. Terkelsen:Milllennium: Employment. Bradley:Milllennium: Employment, Equity Ownership, Research Funding. Li:Milllennium: Employment. Li:Milllennium: Employment. Janz:Milllennium: Research Funding. Van Ness:Milllennium: Research Funding. Manfredi:Milllennium: Employment. Kupperman:Milllennium: Employment.

Evaluating the Antitumor Activity of MLN9708 in a Disseminated Mouse Model of Double Transgenic iMyc Ca/Bcl-XL Plasma Cell Malignancy.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 3835-3835 ◽  
Author(s):  
Michael Fitzgerald ◽  
Yueying Cao ◽  
Bret Bannerman ◽  
Zhi Li ◽  
Olga Tayber ◽  
...  
Keyword(s):  
Antitumor Activity ◽  
Mouse Model ◽  
Lymph Nodes ◽  
Plasma Cell ◽  
Research Funding ◽  
Ex Vivo ◽  
Employment Equity ◽  
Equity Ownership

Abstract Abstract 3835 Poster Board III-771 Introduction The first generation proteasome inhibitor VELCADE® (bortezomib) is indicated for the treatment of patients with multiple myeloma (MM), a form of plasma cell malignancy (PCM). MLN9708 is our novel proteasome inhibitor that selectively and reversibly binds to, and potently inhibits the b5 site of the 20s proteasome in preclinical studies. We have recently demonstrated that MLN9708 significantly prolongs tumor-free survival of double transgenic iMycCa/Bcl-XL mice, a genetically-engineered mouse model of de novo PCM. Here we describe the in vivo evaluation of cell lines derived from double transgenic iMycCa/Bcl-XL mice and the antitumor activity of MLN9708 in a disseminated mouse model of iMycCa/Bcl-XL PCM. Materials MLN9708 immediately hydrolyzes to MLN2238, the biologically active form, upon exposure to aqueous solutions or plasma. MLN2238 was used for all preclinical studies described below. Double transgenic iMycCa/Bcl-XL mice develop de novo PCM, in which neoplastic plasma cell development is driven by the targeted expression of the oncoprotein Myc and anti-apoptotic Bcl-XL (J. Clin. Invest. 113:1763-1773, 2004). DP54 and DP42 are plasma cell tumor cell lines isolated from the bone marrow and lymph nodes, respectively, of syngeneic mice previously inoculated with iMycCa/Bcl-XL tumors (Cancer Res. 67:4069-4078, 2007). In vitro, DP54 and DP42 cells express both the Myc and Bcl-XL transgenes, various plasma cell and B-cell markers including CD38, CD138 and B220, and have gene expression profiles very similar to human MM. Methods Cell viability studies were performed to determine the antiproliferative effects of MLN2238 in DP54 and DP42 cells in vitro. To evaluate DP54 and DP42 cells in vivo, these cells were aseptically inoculated into the tail vein of NOD-SCID mice. Progressions of the resultant PCM were monitored and tumor burdens were evaluated by magnetic resonance imaging (MRI), ex vivo mCT imaging, and histopathology. Mouse plasma samples were collected at the end of the studies and levels of immunoglobulin were assessed. To establish a preclinical disseminated mouse model of iMycCa/Bcl-XL PCM, freshly dissociated DP54-Luc cells (constitutively expressing firefly luciferase under a mouse Ig-k promoter) were aseptically inoculated into the tail vein of NOD-SCID mice. Once tumor growth has been established, mice were randomized into treatment groups and then treated with vehicle, bortezomib (at 0.7mg/kg intravenously [IV] twice weekly [BIW]) or MLN2238 (at 11 mg/kg IV BIW) for 3 consecutive weeks. Tumor burden was measured by bioluminescent imaging. Results In vitro, both DP54 and DP42 cells were sensitive to MLN2238 treatment (LD50 values of 14 and 25 nM, respectively). In vivo, NOD-SCID mice rapidly succumbed to PCM after being inoculated with DP54 and DP42 cells (25 and 14 days post-inoculation, respectively), where the disease was accompanied by marked elevation of plasma immunoglobulins. MRI scans revealed the presence of multiple lesions and several abnormalities were found including: cranial deformation, bowel distortion, splenomegaly and renal edema. Tumor infiltrates, ranging from minor to extensive, were identified in multiple organ compartments (brain<kidney<liver<lymph nodes<spleen<bone marrow) by histopathological analysis. Ex vivo mCT imaging has also revealed signs of bone erosion in the cranial sagittal sutures. Dissemination of DP54-Luc cells after tail vein inoculations was detected by in vivo bioluminescent and confirmed by ex vivo imaging where luminescent tumor nodules were identified in the spleen, kidneys, liver, intestine, lymph nodes, spinal bone and cranium. To assess the antitumor activity of MLN2238, an efficacy study was performed using the DP54-Luc disseminated model. Tumor burden (bioluminescence), skeletal malformation (mCT) and overall survival after treatment with bortezomib and MLN2238 will be presented. Conclusion The DP54-Luc disseminated mouse model of double transgenic iMycCa/Bcl-XL PCM recapitulated several key features of human MM and provided real-time assessment of novel MM therapy preclinically. MLN9708 is currently in human clinical development for both hematological and solid tumor indications. Disclosures: Cao: Milllennium: Employment, Equity Ownership. Bannerman:Milllennium: Employment. Li:Milllennium: Employment. Bradley:Milllennium: Employment, Equity Ownership, Research Funding. Silverman:Milllennium: Employment. Janz:Milllennium: Research Funding. Van Ness:Milllennium: Research Funding. Kupperman:Milllennium: Employment. Manfredi:Milllennium: Employment. Lee:Milllennium: Employment, Equity Ownership.

Effects of Oprozomib in Combination with Pomalidomide and/or Dexamethasone on Human Multiple Myeloma Tumors Growing in SCID Mice

Blood ◽  
2015 ◽  
Vol 126 (23) ◽  
pp. 5349-5349 ◽  
Author(s):  
Eric Sanchez ◽  
Mingjie Li ◽  
Abigail Gillespie ◽  
Puja Mehta ◽  
Suzie Vardanyan ◽  
...  
Keyword(s):  
Multiple Myeloma ◽  
Tumor Size ◽  
Research Funding ◽  
Single Agent ◽  
Xenograft Model ◽  
Tumor Burden ◽  
Scid Mice ◽  
Human Multiple Myeloma ◽  
Minimal Reduction

Abstract Introduction: Oprozomib (OPZ) is an irreversible, orally administered proteasome inhibitor (PI).It decreases tumor burden and prevents tumor-related bone loss in preclinical multiple myeloma (MM) studies. In recently published clinical trials, the combination of the PI carfilzomib with the immunomodulatory agent (IMiD) lenalidomide and dexamethasone (Dex) has shown high response rates with durable responses for previously treated and untreated MM patients. Carfilzomib with the IMiD pomalidomide (Pom) and Dex for the treatment of RRMM patients shows promising results (Shah et al, 2013). We evaluated OPZ in combination with Pom and Dex using two of our human MM xenograft models in severe combined immunodeficient (SCID) mice. Methods: Each SCID mouse (n=10/group) was surgically implanted with a 20 - 40 mm3 MM tumor piece into the hind limb. Seven days post-implantation mice were randomized into treatment groups based on human immunoglobulin (Ig) G levels. OPZ stock solution (4 mg/ml) was diluted to 40 mg/kg using 1% carboxymethylcellulose (CMC) and administered twice weekly on two consecutive days via oral gavage.Dex stock solution (10 mg/ml) was diluted to 1 mg/kg using NaCl and administered daily via intraperitoneal injection.Pom stock solution (1 mg/ml) was diluted to 10 mg/kg using 1% CMC and administered daily via oral gavage. Tumor size was measured using calipers and IgG levels by ELISA. Results: Using our human MM model LAGk-1A, treatment with single agent OPZ or Pom produced a minimal reduction in tumor volume when compared with vehicle-treated mice, whereas Dex alone or OPZ + Pom produced more anti-MM effects, and no differences were observed between these two groups. Mice treated with OPZ + Dex or Pom + Dex also showed greater anti-MM activity than OPZ + Pom or Dex alone but the differences were not significant. All three agents together resulted in much smaller tumors when compared to OPZ + Pom on days 35, 42, 49 and 56 (P = 0.0006, P = 0.0001, P = 0.0002 and P < 0.0001, respectively). The same triplicate resulted in a smaller tumors when compared to OPZ + Dex on days 35, 42, 49, 56, and 63 (P = 0.0112, P = 0.0030, P = 0.0060, P = 0.0035 and P = 0.0021, respectively). Although Pom + Dex had some anti-MM effects when compared to the three single agents and one of the doublets (OPZ + Pom), mice receiving the triplicate demonstrated markedly smaller tumors when compared with Pom + Dex on days 35, 42, 49, 56, 63, 70, and 77 (P = 0.0250, P = 0.0018, P < 0.0001, P = 0.0014, P = 0.0018, P = 0.0017 and P = 0.0014, respectively). Mice receiving Pom + Dex had to be euthanized on day 77, whereas mice receiving all three drugs had very small tumors at study termination. We obtained similar results in a second MM xenograft model that produces IgG (LAGλ-1). Although day 21 post-tumor implantation mice receiving Pom alone had lower IgG levels compared with vehicle-treated mice (P = 0.0053), mice receiving OPZ + Pom had smaller tumors when compared to Pom alone (P = 0.0387), OPZ alone (P = 0.0004), or vehicle-treated mice (P = 0.0001). Although mice receiving Pom alone had a reduction in tumor size when compared with vehicle-treated mice (P = 0.0021), mice receiving OPZ + Pom had smaller tumors when compared with Pom alone (P = 0.0081), OPZ alone (P = 0.0007), or vehicle-treated mice (P < 0.0001). Mice receiving the triplicate showed smaller tumors on day 28 compared with mice treated with either the doublets of Pom + Dex (P = 0.0120) or OPZ + Pom (P = 0.0043). Conclusions: These in vivo human MM xenograft studies show that the combination of OPZ + Pom + Dex shows greater anti-MM activity than doublets (Pom + Dex, OPZ + Dex or OPZ + Pom) or single agents, and provides further support for this three drug combination to treat MM. Disclosures Tang: Onyx: Research Funding. [email protected]:Onyx: Consultancy, Honoraria, Research Funding, Speakers Bureau.

scholarly journals A novel BCMA/CD3 bispecific T-cell engager for the treatment of multiple myeloma induces selective lysis in vitro and in vivo

Leukemia ◽  
2016 ◽  
Vol 31 (8) ◽  
pp. 1743-1751 ◽  
Author(s):  
S Hipp ◽  
Y-T Tai ◽  
D Blanset ◽  
P Deegen ◽  
J Wahl ◽  
...  
Keyword(s):  
Multiple Myeloma ◽  
Bone Marrow ◽  
T Cell ◽  
Plasma Cells ◽  
Ex Vivo ◽  
Xenograft Model ◽  
Selective Lysis ◽  
Bispecific T Cell Engager

Abstract B-cell maturation antigen (BCMA) is a highly plasma cell-selective protein that is expressed on malignant plasma cells of multiple myeloma (MM) patients and therefore is an ideal target for T-cell redirecting therapies. We developed a bispecific T-cell engager (BiTE) targeting BCMA and CD3ɛ (BI 836909) and studied its therapeutic impacts on MM. BI 836909 induced selective lysis of BCMA-positive MM cells, activation of T cells, release of cytokines and T-cell proliferation; whereas BCMA-negative cells were not affected. Activity of BI 836909 was not influenced by the presence of bone marrow stromal cells, soluble BCMA or a proliferation-inducing ligand (APRIL). In ex vivo assays, BI 836909 induced potent autologous MM cell lysis in both, newly diagnosed and relapsed/refractory patient samples. In mouse xenograft studies, BI 836909 induced tumor cell depletion in a subcutaneous NCI-H929 xenograft model and prolonged survival in an orthotopic L-363 xenograft model. In a cynomolgus monkey study, administration of BI 836909 led to depletion of BCMA-positive plasma cells in the bone marrow. Taken together, these results show that BI 836909 is a highly potent and efficacious approach to selectively deplete BCMA-positive MM cells and represents a novel immunotherapeutic for the treatment of MM.

Preliminary Results of a Phase I Study of the Pan-PI3 Kinase Inhibitor SF1126 in Patients with Relapsed and Refractory Myeloma.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 3879-3879
Author(s):  
Sagar Lonial ◽  
R. Donald Harvey ◽  
Dixil Francis ◽  
Engin Gul ◽  
Sundar Jagannath ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Cell Lines ◽  
Plasma Cell ◽  
Solid Tumor ◽  
Stable Disease ◽  
Research Funding ◽  
Median Number ◽  
Pi3k Inhibitor ◽  
Post Infusion

Abstract Abstract 3879 Poster Board III-815 Introduction Preclinical and clinical studies have demonstrated the central importance of the PI3K/AKT axis in malignant cell survival and proliferation, yet few therapeutic options have been available. SF1126 is a conjugate comprised of the well-characterized PI3K inhibitor SF1101 (LY294002) attached to a vascular-targeting tetra-peptide (SF1174) designed to bind to RGD-recognizing integrin receptors expressed on endothelial and tumor cells resulting in angiogenesis inhibition and direct antitumor effect. SF1126 has recently demonstrated reversal of resistance mediated through the PI3K/PTEN pathway in trastuzumab-resistant HER2-over-expressing breast cancer cell lines. From the parallel solid tumor study (ASCO 2009), SF1126 was well tolerated, inhibited the PI3K pathway selectively in tumor tissue, and resulted in stable disease in a heavily pretreated population. The rationale for using SF1126 in myeloma is based upon a body of work from Durden et al. (ASH 2007) and David et al. (ASH 2008) demonstrating in vivo and in vitro activity in human myeloma cell lines and xenograft models. These studies demonstrated SF1126 has activity at 5-10uM and combines safely and with enhanced efficacy with dexamethasone, melphalan, and bortezomib. Methods Patients were eligible if they had relapsed or refractory myeloma with at least 2 prior lines of therapy. Dose escalation using Bayesian methodology [Escalation With Overdose Control (EWOC)] incorporated information from the solid tumor trial along with information from this trial. In addition to standard measures of efficacy, a novel assay assessing in vivo PI3K inhibition was evaluated. Briefly, we have developed a protocol for multiparameter flow cytometry analysis of intracellular phosphoepitopes for monitoring pharmacodynamic (PD) molecular targets of SF1126 in study subject's myeloma cells. The aims are to determine: 1) constitutive activation of AKT (by comparing to ex vivo LY294002 treatment) 2) AKT activation in response to IGF-1 (a microenvironment stimulus) 3) inhibition of basal activation and/or inhibition of IGF-1 potentiated response following SF1126 treatment and 4) correlation of this analysis to SF1126 dose and patient response. Subjects undergo serial bone marrow (BM) sampling on day 0 and day 1 (4 hrs after dosing) of cycles 1 and 2. Results To date, a total of 7 patients have been treated with escalating doses ranging from 90 to 1110 mg/m2. Most patients were male (6), median age was 63 (50-69) and median number of prior treatments was 8 (3-10). All had documented refractory disease with bone marrow aspirates showing plasma cell percentages of 30-90%. No grade 4 drug-related toxicities have been noted to date. Approximately one-third of patients experienced grade 2 nausea/vomiting. Constitutional symptoms included fatigue and loss of appetite. Although preclinical studies demonstrated a rise in blood glucose one hour post infusion, this was not seen in any patients receiving drug. The dose limiting toxicity is still undefined. Median number of cycles is 1 (0.4-2.5), with one patient achieving stable disease (urinary protein stabilized following rapid rise prior to study initiation). All patients were taken off study due to progression. In vivo inhibitory effects of SF1126 on the pathway were demonstrated in bone marrow samples. PK data demonstrates similar PK to what has been seen in the solid tumor trial: a) SF1126 is rapidly cleared post-infusion; b) PK of active hydrolysis product (LY294002/SF1101) shows t1/2 ∼1.1-1.5 hrs; c) dose proportional Cmax and AUC(0-t); d) AUC values at doses ≥ 140 mg/m2 exceed those found effective in mouse xenograft studies. Conclusion The PI3K inhibitor SF1126 resulted in similar PK to that seen in solid tumor patients and in vivo studies demonstrated that PI3K activity in the plasma cell compartment of the bone marrow had suppression of this key pathway following SF1126. Completion of the study at the current dose (1110mg/m2) and planning for a future trial combining SF1126 with other active agents in myeloma is currently ongoing. Additional PK/PD and clinical data from this trial will be available. Disclosures: Lonial: Millennium: Consultancy, Research Funding; Celgene: Consultancy; BMS: Consultancy; Novartis: Consultancy; Gloucester: Research Funding. Jagannath:Millennium: Honoraria, Membership on an entity's Board of Directors or advisory committees; Celgene: Honoraria; Merck: Honoraria. Garlich:Semafore Pharmaceuticals: Employment, Equity Ownership, Research Funding. Trudel:Celgene: Honoraria, Speakers Bureau; Ortho Biotech: Honoraria.

In Vivo Bioluminescence Imaging to Study the Contribution of TNF-TNFR Interactions on Immune and Parenchymal Cells to Tumor Cell Progression in a Syngenic Mouse Model

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 1110-1110
Author(s):  
Martin Chopra ◽  
Simone S Riedel ◽  
Viktoria von Krosigk ◽  
Carina A Bäuerlein ◽  
Christian Brede ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Mouse Model ◽  
Tumor Cell ◽  
Knockout Mice ◽  
Bioluminescence Imaging ◽  
Ex Vivo ◽  
Tumor Burden ◽  
Cell Progression ◽  
In Vivo Bioluminescence Imaging

Abstract Abstract 1110 The cytokine tumor necrosis factor-α (TNF) has pleiotropic functions both in normal physiology and disease. TNF and its relative lymphotoxin-α (LT) signal by activating two cell surface receptors TNFR1 and TNFR2. TNFR1 is expressed on most cells whereas TNFR2 is mainly expressed in cells of the hematopoietic system. TNF-TNFR interactions were shown to play a major role in graft-versus-leukemia effect and in the immunosurveillance of solid tumors. To study the contribution of TNF-TNFR interactions on tumor cell progression we employed a syngenic B16 melanoma mouse model combined with in vivo bioluminescence imaging. Firefly luciferase-transgenic B16 melanoma cells were injected intravenously into syngenic albino C57BL/6 hosts. The host mice were either of wildtype, TNF, LT, TNFR1, TNFR2 knockout or TNFR1R2 double knockout genotype. The localization and expansion of the B16 cells was monitored by in vivo bioluminescence imaging for up to 14 days. On days 15, mice were sacrificed and internal organs were imaged ex vivo to further elucidate the organ-specific tumor burden. B16 tumors were primarily found in the lungs of all genotypes. All female knockout genotypes displayed a higher lung tumor burden than wildtype mice. In male mice, only TNF knockout presented enhanced tumor cell signals. Following ex vivo imaging we evaluated the pulmonary infiltration of NK1.1 or NKp46, CD8, CD4 and CD4/CD25/Foxp3 regulatory T cells by flow cytometry and immunofluorescence microscopy. Compared to wildtype mice, more regulatory T cells infiltrated the lungs of female TNFR1 knockout mice (200%). In LT knockout mice, very few NK cells (<20%) but more CD4+ cells (160%) infiltrated the lungs. Only subtle changes occurred in the other deficient mouse strains. However, these changes were independent of the presence of tumor cells and could also be found in normal knockout mice without B16 tumors. Within sections of tumor-bearing lungs, we found that TNF and all three TNFR knockouts exhibited less CD8+ cells within tumors than did wildtype or LT knockout mice. The number of CD8+ cells in normal lung tissue was not altered across the different genotypes. The deficit in NK cells of LT knockout mice was confirmed by histology. The enhanced tumor progression in all knockout mice could be a secondary effect due to their altered immune phenotype rather than to the loss of TNF-TNFR interactions. To circumvent this potential experimental bias and to further assess the influence of the loss of expression of parts of the TNF/TNFR-system in immune cells only, we generated bone marrow chimeras by reconstituting lethally irradiated female wildtype mice with bone marrow derived from TNF, LT, TNFR1 or TNFR2 knockout mice. Tumor cell signals in these chimeric mice progressed more than in normal wildtype mice. In contrast to the first set of experiments with knockout mice, we found that mice reconstituted with either TNF or TNFR2 knockout bone marrow presented less tumor cell signal than did mice reconstituted with wildtype bone marrow. TNF-TNFR interactions between immune cells appear to exhibit pro-tumorigenic functions in our mouse model. These results show that TNF-TNFR interactions are an important step in tumor cell progression and that the outcome of these interactions differs, depending on whether immune or parenchymal cells are deficient in TNF-TNFR signalling components. Disclosures: No relevant conflicts of interest to declare.

L-Stereoisomer RNA Oligonucleotide Anti-SDF-1 (Nox-A12) Disrupts the Interaction of Multiple Myeloma Cells with the Bone Marrow Milieu In Vivo, Leading to Enhanced Sensitivity to Bortezomib

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 887-887
Author(s):  
Aldo M Roccaro ◽  
Antonio Sacco ◽  
Phong Quang ◽  
AbdelKareem Azab ◽  
Patricia Maiso ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Confocal Microscopy ◽  
Board Of Directors ◽  
Tumor Cells ◽  
Research Funding ◽  
Ex Vivo ◽  
In Vivo Confocal Microscopy ◽  
Advisory Committees

Abstract Abstract 887 Background. Stomal-cell-derived factor 1 (SDF-1) is known to be involved in bone marrow (BM) engrafment for malignant tumor cells, including CXCR4 expressing multiple myeloma (MM) cells. We hypothesized that de-adhesion of MM cells from the surrounding BM milieu through SDF-1 inhibition will enhance MM sensitivity to therapeutic agents. We therefore tested NOX-A12, a high affinity l-oligonucleotide (Spiegelmer) binder to SDF-1in MM, looking at its ability to modulate MM cell tumor growth and MM cell homing to the BM in vivo and in vitro. Methods. Bone marrow (BM) co-localization of MM tumor cells with SDF-1 expressing BM niches has been tested in vivo by using immunoimaging and in vivo confocal microscopy. MM.1S/GFP+ cells and AlexaFluor633-conjugated anti-SDF-1 monoclonal antibody were used. Detection of mobilized MM-GFP+ cells ex vivo has been performed by flow cytometry. In vivo homing and in vivo tumor growth of MM cells (MM.1S-GFP+/luc+) were assessed by using in vivo confocal microscopy and in vivo bioluminescence detection, in SCID mice treated with 1) vehicle; 2) NOX-A12; 3) bortezomib; 4) NOX-A12 followed by bortezomib. DNA synthesis and adhesion of MM cells in the context of NOX-A12 (50–200nM) treated primary MM BM stromal cells (BMSCs), in presence or absence of bortezomib (2.5–5nM), were tested by thymidine uptake and adhesion in vitro assay, respectively. Synergism was calculated by using CalcuSyn software (combination index: C.I. according to Chou-Talalay method). Results. We first showed that SDF-1 co-localizes in the same bone marrow niches of growth of MM tumor cells in vivo. NOX-A12 induced a dose-dependent de-adhesion of MM cells from the BM stromal cells in vitro. These findings were corroborated and validated in vivo: NOX-A12 induced MM cell mobilization from the BM to the peripheral blood (PB) as shown ex vivo, by reduced percentage of MM cells in the BM and increased number of MM cells within the PB of mice treated with NOX-A12 vs. control (BM: 57% vs. 45%; PB: 2.7% vs. 15%). We next showed that NOX-A12-dependent de-adhesion of MM cells from BMSCs lead to enhanced MM cell sensitivity to bortezomib, as shown in vitro, where a synergistic effect between NOX-A12 (50–100 nM) and bortezomib (2.5–5 nM) was observed (C.I.: all between 0.57 and 0.76). These findings were validated in vivo: tumor burden detected by BLI was similar between NOX-A12- and control mice whereas bortezomib-treated mice showed significant reduction in tumor progression compared to the control (P<.05); importantly significant reduction of tumor burden in those mice treated with sequential administration of NOX-A12 followed by bortezomib was observed as compared to bortezomib alone treated mice (P <.05). Similarly, NOX-A12 + bortezomib combination induced significant inhibition of MM cell homing in vivo, as shown by in vivo confocal microscopy, as compared to bortezomib used as single agent. Conclusion. Our data demonstrate that the SDF-1 inhibiting Spiegelmer NOX-A12 disrupts the interaction of MM cells with the BM milieu both in vitro and in vivo, thus resulting in enhanced sensitivity to bortezomib. Disclosures: Roccaro: Roche:. Kruschinski:Noxxon Pharma AG: Employment. Ghobrial:Novartis: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees; Millennium: Consultancy, Membership on an entity's Board of Directors or advisory committees; Millennium: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Bristol-Myers Squibb: Research Funding; Noxxon: Advisory Board, Research Funding.

scholarly journals Vecabrutinib Is Efficacious In Vivo in a Preclinical CLL Adoptive Transfer Model

Blood ◽  
2018 ◽  
Vol 132 (Supplement 1) ◽  
pp. 1868-1868 ◽  
Author(s):  
Billy Michael Chelliah Jebaraj ◽  
Annika Scheffold ◽  
Eugen Tausch ◽  
Judith A. Fox ◽  
Pietro Taverna ◽  
...  
Keyword(s):  
Bone Marrow ◽  
T Cells ◽  
T Cell ◽  
Board Of Directors ◽  
Cd8 T Cells ◽  
Research Funding ◽  
Tumor Burden ◽  
Transfer Model ◽  
Advisory Committees

Abstract B cell receptor signaling (BCR) in chronic lymphocytic leukemia (CLL) drives tumor cell proliferation and survival. Inhibition of Bruton's tyrosine kinase (BTK), a key enzyme in the BCR pathway, has proved to be efficacious even in poor-risk and chemo-refractory patients. However resistance to the BTK inhibitor ibrutinib has been shown to emerge in a subset of CLL patients. Of importance, the C481S BTK mutation conferred resistance by preventing the covalent binding of ibrutinib to its target cysteine 481 in BTK. Vecabrutinib (formerly known as SNS-062, a succinate salt) is a novel, highly potent, next generation noncovalent BTK inhibitor which demonstrated biochemical and cellular activity against C481S BTK mutant in vitro. However, the efficacy of vecabrutinib and its impact on the T-cell microenvironment has not been studied in in vivo preclinical CLL models. In the present study, the efficacy of vecabrutinib was investigated using the Eµ-TCL1 adoptive transfer model. Mice were randomized to treatment with either 40mg/kg vecabrutinib succinate, twice daily by oral gavage (n=6) or vehicle control (n=6). The mice were sacrificed after 2 weeks of treatment and changes in tumor burden as well as alterations in T-cell microenvironment were analysed in detail. Treatment with vecabrutinib decreased tumor burden as observed by a significant decrease in WBC count (36.5 vs. 17.1 giga/L; P=0.002), spleen weight (median 0.56g vs. 0.31g; P=0.005) and liver weight (median 1.5g vs. 1.2g; P=0.005) compared to vehicle treatment. Correspondingly, the CD5+ CD19+ tumor cells were significantly decreased in blood (P=0.002) and spleen (P=0.002) while no significant difference was observed in bone marrow (P=0.818) upon treatment with vecabrutinib. Since BTK inhibition is known to reshape the tumor microenvironment, we studied the impact of vecabrutinib specifically on T-cell subsets. Firstly, no difference in the proportions of CD4 or CD8 expressing T-cells was observed in mice treated with vehicle or vecabrutinib. However, of interest, the percentage of CD4+ CD25+ FoxP3+ regulatory T cells (Tregs) were significantly decreased upon treatment with vecabrutinib in peripheral blood (P=0.026) and spleen (P=0.009). The decrease in Tregs was due to reduced proliferation of these cells upon exposure to the drug as measured by Ki-67 staining. Also, the Tregs expressing the maturation and activation markers such as CD103 and GITR were significantly decreased in blood and spleen upon drug treatment. Further, we analysed the changes in CD8 T-cell subsets following treatment with vecabrutinib. Treatment with the drug resulted in expansion of the CD127+ CD44- naïve CD8 T-cells in blood, bone marrow and spleen (all P values 0.002) while the CD127+ CD44+ memory CD8 T-cells were significantly decreased in bone marrow and spleen (all P values 0.009). Also, the CD127low CD44int-hi effector CD8 T-cells were decreased in blood (P=0.004), bone marrow (P=0.004) and spleen (P=0.002) upon vecabrutinib treatment. Therefore, vecabrutinib treatment did not alter the percentage of CD4+ and CD8+ T cells in mice however, significant changes in the subset composition of the CD4 and CD8 T cells were observed. Lastly, to analyse the impact of vecabrutinib on survival, a cohort of mice (n=12) were transplanted with 5 million splenic tumor cells isolated from Eµ-TCL1 transgenic mice. After allowing for engraftment, the mice were randomized to treatment with the drug (n=6) or vehicle (n=6). Of note, the mice treated with the drug showed a significant increase in survival (median 35 days from transplant; P<0.001) compared to treatment with vehicle (median 28 days). In summary, vecabrutinib was efficacious in vivo in a preclinical CLL adoptive transfer model, decreasing tumor burden in different organs and significantly improving survival. Treatment with the drug altered the T-cell architecture in vivo. Of interest, the immunosuppressive Tregs, which protect the tumor from immune surveillance were decreased in various tissue compartments; however, a decrease in the effector CD8 T cells might impact anti-tumor immunity if there is a consistent effect upon drug treatment. Vecabrutinib antitumor activity and effects on T-cell populations in vivo in this preclinical CLL model are intriguing, merits further investigation and supports the ongoing phase 1b/2 study in patients with previously treated B-lymphoid malignancies (NCT03037645). Disclosures Tausch: AbbVie: Consultancy, Other: Travel grants; Celgene: Consultancy, Other: Travel grants; Gilead: Consultancy, Other: Travel grants. Fox:Sunesis Pharmaceuticals: Employment; Amphivena Therapeutics: Employment. Taverna:Sunesis Pharmaceuticals: Employment. Stilgenbauer:Sanofi: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Genentech: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Boehringer-Ingelheim: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Hoffmann La-Roche: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Amgen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; GSK: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Gilead: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Genzyme: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; AbbVie: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Pharmcyclics: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Mundipharma: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding.

Evaluation Of Acadesine, a Drug Stimulating Cell Autophagy, In Azacitidine(AZA)-Resistant Myelodysplastic Syndromes (MDS)

Blood ◽  
2013 ◽  
Vol 122 (21) ◽  
pp. 1568-1568
Author(s):  
Thomas Cluzeau ◽  
Guillaume Robert ◽  
Jean Michel Karsenti ◽  
Frederic Luciano ◽  
Nicolas Mounier ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Cell Death ◽  
Myelodysplastic Syndromes ◽  
Research Funding ◽  
Bone Marrow Cells ◽  
Ex Vivo ◽  
Cell Metabolism ◽  
Vitro Effect

Abstract Background AZA is currently the first line treatment for intermediate-2 and high-risk IPSS myelodysplastic syndromes (MDS) and acute myeloid leukemia (AML) with 20 to 30% of marrow blasts. We have previously reported that cells from AZA-resistant patients exhibit impaired mitochondrial apoptosis but maintain functional autophagy (Cluzeau et al. Cell Cycle 2011, Oncotarget 2012). Acadesine (ACA), also known as AICAR or Aica-Riboside is a nucleoside analogue that has been shown to trigger autophagy in AZA resistant cells. Methods In vitro effect: We used an AZA-resistant MDS/AML cell line (SKM1-R) as a tool to decipher AZA resistance. Cells were treated with increasing doses of ACA (0.5-2mM) or with a maximally efficient dose of AZA (1µM) and induction of cell death was assessed by cell metabolism and Propidium Iodide (PI) assays. In vivo effect: The effect of ACA was also assessed in a mouse xenograft model of SKM1-R cells. When tumors reached 100 mm3, mice were treated daily with an intra-peritoneal injection of the vehicle alone, 5 mg/kg AZA, or 200 or 400 mg/kg ACA. Ex vivo effect: We finally used primary bone marrow cells from AZA-resistant MDS or AML-resistant patients (n=12) (clinicalTrials.gov identifier: NCT01210274) to perform cell metabolism assays. Results In vitro effect: Only a slight decrease of cell metabolism and a moderate increase of PI staining were detected following stimulation with 1µM AZA confirming the resistance of SKM1-R cells to AZA. In identical conditions, ACA induced a robust increase of cell death in AZA-resistant cells with a maximal effect at 2mM. Induction of cell death by ACA was independent of apoptosis but relied on autophagy induction, as shown by the conversion of LC3-I to LC3-II and an increase of cathepsin B activity, that are respectively early and late markers of autophagy. In vivo effect: As expected, AZA failed to trigger tumor regression of AZA-resistant SKM1-R cells in vivo compared to vehicle alone, whereas ACA was found to induce a statistically significant inhibition of tumor growth at both tested concentrations. Ex vivo effect:Bonferroni’s Multiple Comparison Test performed in 6 AZA-resistant MDS patients showed significant reduction of cell metabolism between ACA and untreated cells (66% and 78% at 1 and 2 mM of ACA) and between ACA and AZA-treated cells (60% and 72% at 1 and 2mM of ACA,). Identical results were found in 6 AML AZA-resistant AML patients with a significant reduction of cell metabolism between ACA and untreated cells (63% and 81% at 1 and 2mM of ACA) and ACA and AZA-treated cells (56% and 75% at 1 and 2 mM of ACA). Conclusion Our results show the high efficacy of Acadesine in vitro, in vivo and ex vivo in AZA-resistant MDS and AML cell lines and patient’s bone marrow cells. Induction of cell death by autophagy seems to be the main mechanism by which ACA circumvents AZA resistance in MDS and AML cells. These encouraging results prompted us to initiate a multicenter phase I/II clinical trial with the French MDS Group (GFM) to assess the safety and efficacy of ACA in MDS and AML patients with 20 to 30% of marrow blasts not responding or relapsing after AZA treatment (clinicalTrials.gov identifier: NCT01813838). Disclosures: Cluzeau: Advancell: Research Funding. Robert:Advancell: Research Funding. Auberger:Advancell: Research Funding.

A Novel Activating Mutation Of CXCR4 Plays a Crucial Role In Waldenstrom Macroglobulinemia Biology

Blood ◽  
2013 ◽  
Vol 122 (21) ◽  
pp. 272-272 ◽  
Author(s):  
Aldo M Roccaro ◽  
Antonio Sacco ◽  
Cristina Jimenez ◽  
Patricia Maiso ◽  
Michele Moschetta ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Cell Proliferation ◽  
Tumor Cells ◽  
Research Funding ◽  
Ex Vivo ◽  
Advisory Board ◽  
Beta Catenin ◽  
Activating Mutation

Abstract Background The C-X-C chemokine receptor type 4 (CXCR4) plays a crucial role in modulating the biology of B-cell lymphoproliferative disorders. Recent whole genome sequencing studies have identified unique CXCR4 mutations in 29% of the 55 evaluated patients with Waldenstrom Macroglobulinemia (WM). In this study, we sought to better define the mutation status of CXCR4 in B-cell malignancies and define the functional role of this mutation in the progression of WM in vivo. Methods Allele-specific(AS) PCR has been performed on bone marrow (BM)-derived tumor cells of patients with WM (n: 131); IgM monoclonal gammopathy of undetermined significance (MGUS; n: 40); as well as in patients with diffuse large cell lymphomas (DLBCL; n: 75), splenic marginal zone lymphoma (SMZL; n: 14), B-chronic lymphocytic leukemia (B-CLL; n: 37), hairy cell leukemia (HCL; n: 35), multiple myeloma (MM; n: 36), IgA/IgG MGUS (n: 22), lymphoplasmacytic lymphoma without WM criteria (n: 13), and amyloidosis (n: 6). CXCR4-loss and -gain of function studies have been performed on WM cells stably expressing either shRNA-CXCR4, CXCR4-ORF-GFP-tagged or scramble-RFP-tagged (generated via lentivirus-based infection). A mutagenesis kit has been used to generate the C1013GCXCR4 mutant protein (C1013GCXCR4) in WM cells, via lentivirus-based infection. CXCR4-knock-in or C1013GCXCR4-mutated cells and the corresponding controls have been injected i.v. into SCID/Bg mice and tumor dissemination has been evaluated ex vivo by immunohistochemistry IHC (human-CD20; -CXCR4). C1013GCXCR4-mutated cells have been characterized at mRNA levels (U133 plus2) using GSEA. A novel human anti-CXCR4 mAb (BMS-936564/MDX-1338; Bristol Myers Squibb, NY) has been tested in vitro (cell proliferation, MTT, adhesion and migration to primary WM BM mesenchymal stromal cells) and in vivo (10mg/kg i.p. x3-4/week). Tumor growth has been evaluated by IHC ex vivo (hCD20; hCXCR4) and by immunofluorescence. Results We examined the mutational status of C1013GCXCR4 and confirmed the presence of this specific mutation in 28% of the 131 cases evaluated. The mutation was also detected at the stage of IgM-MGUS (20%); while it was present in a minority of patients with DLBCL (1%) and SMZL (7%). Remarkably, it was absent in all MM (n=36) and IgA/IgG MGUS patients (n=22), and it was not detected in healthy subjects (n=32). The functional relevance of the C1013G-CXCR4 variant was next examined in vivo. Mice injected with C1013GCXCR4-cells presented with a significant dissemination of tumor cells, demonstrating involvement of liver, bone marrow, lymph nodes, kidney and lung. IHC showed the presence of CXCR4+ and CD20+ cells in all the tissues examined; and quantification of CXCR4 and CD20 positivity was higher in C1013GCXCR4-cells-, compared to parental(p)-WM cell-injected mice (NIS Elements software, Nikon, Melville, NY; P<0.05). In addition, C1013GCXCR4-cells were further characterized in vitro, showing increased adhesion and cell proliferation in the presence of primary WM BM-MSCs. These findings were also confirmed using CXCR4-overexpressing cells. In contrast CXCR4-knock-down cells presented the opposite behavior, where reduced adhesion and proliferation in presence of primary WM BM-MSCs were observed. By performing GSEA we demonstrated that genes related to invasiveness, cell proliferation, anti-apoptosis, and oncogenesis were all enriched in C1013GCXCR4-cells compared to the parental-WM cells. These findings let us hypothesize that C1013GCXCR4 may act as an activating mutation in WM cells. Indeed, in a different mouse model, CXCR4 over-expressing cells and scramble infected cells were injected into mice, showing similar phenotype to the one observed upon C1013GCXCR4-WM cell-injected-mice. Finally, the novel antibody BMS-936564/MDX-1338 exerted anti-WM activity both in vitro and in vivo, with anti-tumor effects observed also against the mutated variant. This was supported by inhibition of pro-survival pathways (p-ERK; pAKT); induction of pro-apototic proteins (cleaved-PARP and -caspase-9); up-regulation of p-GSK3beta, p-beta catenin and relative beta catenin degradation. Conclusion These findings demonstrate that C1013GCXCR4 acts as an activating mutation in WM; and it is targetable by using MDX936564/1338 thus providing the basis for translating these observations into clinical trials for WM patients. Disclosures: Kuhne: BMS: Employment. Cardarelli:BMS: Employment. Ghobrial:BMS: Advisory board, Advisory board Other, Research Funding; Onyx: Advisoryboard Other; Noxxon: Research Funding; Sanofi: Research Funding.

scholarly journals Dissecting the Mechanisms of Activity of SLAMF7 and the Targeting Antibody Elotuzumab in Multiple Myeloma

Blood ◽  
2014 ◽  
Vol 124 (21) ◽  
pp. 3431-3431 ◽  
Author(s):  
Siobhan Glavey ◽  
Michaela Reagan ◽  
Salomon Manier ◽  
Michele Moschetta ◽  
Yawara Kawano ◽  
...  
Keyword(s):  
Research Funding ◽  
Xenograft Model ◽  
Myeloma Cell ◽  
Tumor Burden ◽  
Advisory Board ◽  
Xenograft Models ◽  
Human Igg1

Abstract Background Signaling lymphocytic activation molecule family 7 (SLAMF7) is a cell surface receptor which is expressed at high levels in multiple myeloma (MM) cells and serves as a therapeutic target in this disease. Elotuzumab, a humanized monoclonal antibody targeting SLAMF7, has shown promising activity, particularly in combination with lenalidomide, in MM patients in the clinical trial setting. While the primary mechanism of action of elotuzumab in pre-clinical in vitro studies has been shown to be antibody-dependent cellular cytotoxicity (ADCC) mediated via NK-cell CD16, other possible mechanisms of activity of elotuzumab in MM are not well defined. Specifically, the downstream signaling effects of SLAMF7 have not been delineated in myeloma cells. We set out to examine the effect of stable SLAMF7 knockdown (KD) on MM tumor development in vivo and evaluated the ability of elotuzumab to exert an anti-myeloma effect within the bone marrow niche in MM mouse models. Methods: In-vitro: KD of SLAMF7 was performed in myeloma cell line MM1s using lentiviral shRNAs targeting different regions in the SLAMF7 mRNA. Specific SLAMF7 knockdown was confirmed by reduced SLAMF7 mRNA and protein expression in comparison to cells receiving scrambled control shRNA lentivirus. Survival of SLAMF7 KD cells in comparison to scrambled control cells was assessed by MTT assay. The effect of elotuzumab treatment on the survival of MM1s cells was also assessed. In vivo: Tumor Xenograft models SLAMF7 KD; MM1S-GFP-Luc+ cells (5X106) were injected intravenously (IV) into SCID-Bg mice (n=7/group) and animals underwent bioluminescent imaging (BLI) weekly following injection. Xenograft models elotuzumab; Forty eight hours after IV injection of MM1S-GFP-Luc+ cells (5X106) elotuzumab or human IgG control antibody (both 10mg/kg) was administered via intraperitoneal (IP) injection twice weekly and mice (n=7/group) were followed for tumor burden and survival outcomes. A follow up study was performed (n=5/group) using a modified form of elotuzumab (IgG1.1mAb 10mg/kg IP) harboring mutations in the IgG1 CH2 domain which decreases ADCC via decreased Fc-γ receptor binding allowing evaluation of the CD16 mediated effect in this model. Results SLAMF7 KD resulted in a significant reduction in the survival of MM1s cells at 24 hours as assessed by MTT assay (P = 0.001). No significant reduction in survival was noted for the MM1s myeloma cell line following elotuzumab treatment at 24 hours in the absence of effector cells. Interestingly, knockdown of SLAMF7 resulted in a reduction in tumor burden in the SCID-Bg xenograft model as assessed by weekly BLI signal (P = 0.005 at week 6) with a consequent increase in survival for mice receiving SLAMF7 KD cells. (average 49 vs. 110 days Log Rank P<0.0001). Treatment of mice that had been administered MM1s cells and subsequently treated with elotuzumab resulted in a significant reduction in tumor burden (P = 0.001 at 5 weeks) and prolonged survival (Log Rank P = 0.0001) compared to human IgG1 control antibody treated mice (n=7/group). A follow up 3 arm study comparing IgG1.1f mAb to elotuzumab or human IgG1 control antibody (n=5/group) demonstrated no significant difference in tumor burden between the group receiving IgG1.1 mAb (no CD16 binding) and human IgG1 control antibody (P =0.8 at week 3). The difference in tumor burden between IgG1.1 mAb and elotuzumab was significant (P = 0.019 at 3 weeks) indicating that the effect on tumor burden seen in these mice was indeed CD16 dependent. Conclusions Knockdown of SLAMF7 in MM cells results in reduced tumor burden and survival in xenograft mice, indicating that SLAMF7 potentially plays a role in tumor biology in this disease. In addition elotuzumab treatment reduces tumor burden in a xenograft model of MM with defective NK cells in a CD16 dependent manner indicating that additional mechanisms beyond ADCC may be important in mediating the anti-myeloma effect of elotuzumab. Disclosures Glavey: BMS: Consultancy, Research Funding. Robbins:Bristol-Myers Squibb: Employment; Bristol-Myers Squibb: Equity Ownership. Ghobrial:Onyx: Advisory board Other; BMS: Advisory board, Advisory board Other, Research Funding; Noxxon: Research Funding; Sanofi: Research Funding.

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