Anti-Myeloma Activity of a Novel Free Radical Inducer Rrx-001

Blood ◽  
2014 ◽  
Vol 124 (21) ◽  
pp. 4712-4712 ◽  
Author(s):  
Deepika Sharma Das ◽  
Ze Tian ◽  
Arghya Ray ◽  
Durgadevi Ravillah ◽  
Yan Song ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Clinical Trial ◽  
Drug Resistance ◽  
Board Of Directors ◽  
Tumor Cells ◽  
Cell Lines ◽  
Advisory Committees ◽  
Healthy Donors

Abstract Background and Rationale: Multiple Myeloma (MM) remains incurable despite the advent of novel drugs, highlighting the need for further identification of factors mediating disease progression and resistance. The bone marrow (BM) microenvironment confers growth, survival, and drug resistance in MM cells. Studies to date suggest an important role of BM hypoxia (low oxygenation) in MM cell survival, drug resistance, migration, and metastasis. Therapies targeting the MM cell in its BM milieu under hypoxic conditions may therefore achieve responses in patients resistant to various therapies. Recent studies led to the development of a novel aerospace-industry derived Phase 2 molecule RRx-001 with epigenetic and NO-donating properties. RRx-001 generates reactive oxygen and nitrogen species (RONS), which induces oxidative stress in tumor cells. Importantly, RRx-001 is also a potent vascular disrupting agent, which further provides rationale for utilizing RRx-001 as a therapeutic agent since tumor-associated angiogenesis is a characteristic of MM. A Phase I clinical trial has shown RRx-001 to have antitumor activity in heavily pretreated cancer patients and to be safe and well tolerated with no dose-limiting toxicities (Reid et al. J Clin Oncol 32:5s, 2014 suppl; abstr 2578). Here we examined the anti-MM activity of RRx-001 using in vitro and in vivo models of MM. Materials and methods: MM cell lines, patient MM cells, and peripheral blood mononuclear cells (PBMCs) from normal healthy donors were utilized to assess the anti-MM activity of RRx-001 alone or in combination with other agents. Drug sensitivity, cell viability, apoptosis, and migration assays were performed using WST, MTT, Annexin V staining, and transwell Inserts, respectively. Synergistic/additive anti-MM activity was assessed by isobologram analysisusing “CalcuSyn” software program. Signal transduction pathways were evaluated using immunoblotting. ROS release, nitric oxide generation, and mitochondrial membrane potential was measured as previously described (Chauhan et al., Blood, 2004, 104:2458). In vitro angiogenesis was assessed using matrigel capillary-like tube structure formation assays. DNMT1 activity was measured in protein lysates using EpiQuik DNMT1 assay kit. 5-methyl cytosine levels were analyzed in gDNA samples using methylflash methylated DNA quantification kit from Enzo life sciences; USA. For xenograft mouse model, CB-17 SCID-mice were subcutaneously inoculated with MM.1S cells as previously described (Chauhan et al., Blood, 2010, 115:834). Statistical significance of data was determined using a Student’st test. RRx-001 was obtained from RadioRx Inc., CA, USA; bortezomib, SAHA, and pomalidomide were purchased from Selleck chemicals, USA. Results: Treatment of MM cell lines (MM.1S, MM.1R, RPMI-8226, OPM2, H929, Dox-40 ARP-1, KMS-11, ANBL6.WT, ANBL6.BR, and LR5) and primary patient cells for 24h significantly decreased their viability (IC50 range 1.25nM to 2.5nM) (p < 0.001; n=3) without markedly affecting PBMCs from normal healthy donors, suggesting specific anti-MM activity and a favorable therapeutic index for RRx-001. Tumor cells from 3 of 5 patients were obtained from patients whose disease was progressing while on bortezomib, dexamethasone, and lenalidomide therapies. Moreover, RRx-001 inhibits proliferation of MM cells even in the presence of BM stromal cells. Mechanistic studies show that RRx-001-triggered apoptosis is associated with 1) induction of DNA damage response signaling via ATM/p53/gH2AX axis; 2) activation of caspases mediating both intrinsic and extrinsic apoptotic pathways; 3) increase in oxidative stress through release of ROS and generation of NO; and 4) decrease in DNA methyltransferase (DNMT1) enzymatic activity and global methylation levels. Furthermore, RRx-001 blocked migration of MM cells and angiogenesis. In vivo studies using subcutaneous human MM xenograft models show that RRx-001 is well tolerated and inhibits tumor growth. Finally, combining RRx-001 with bortezomib, SAHA, or pomalidomide induces synergistic anti-MM activity and overcomes drug resistance. Conclusion: Our preclinical studies showing efficacy of RRx-001 in MM disease models provide the framework for clinical trial of RRx-001, either alone or in combination, to improve outcome in relapsed and refractory MM patients. Disclosures Richardson: Oncopeptides AB: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees; Millennium: Membership on an entity's Board of Directors or advisory committees. Oronsky:RadioRx Inc, : Employment. Scicinski:RadioRx Inc,: Employment. Chauhan:Triphase Accelerator: Consultancy. Anderson:Celgene: Consultancy; Millenium: Consultancy; Onyx: Consultancy; Gilead: Consultancy; Sanofi Aventis: Consultancy; BMS: Consultancy; Oncopep/Acetylon: Equity Ownership.

Synergistic Anti-Myeloma Activity of a Proteasome Inhibitor Marizomib and IMiD® Immunomodulatory Drug Pomalidomide

Blood ◽  
2014 ◽  
Vol 124 (21) ◽  
pp. 2099-2099
Author(s):  
Deepika Sharma Das ◽  
Durgadevi Ravillah ◽  
Arghya Ray ◽  
Yan Song ◽  
Paul G. Richardson ◽  
...  
Keyword(s):  
Board Of Directors ◽  
Tumor Cells ◽  
Cell Lines ◽  
Proteasome Inhibitor ◽  
Response To Treatment ◽  
Low Doses ◽  
Advisory Committees ◽  
Healthy Donors

Abstract Background and Rationale: Proteasome inhibitor bortezomib is an effective therapy for the treatment of relapsed and refractory multiple myeloma (RRMM); however, prolonged treatment can be associated with toxicity, peripheral neuropathy and drug resistance. Our earlier studies showed that a novel proteasome inhibitor marizomib is distinct from bortezomib in its chemical structure, mechanisms of action, and effects on proteasomal activities (Chauhan et al., Cancer Cell 2005, 8:407-419). We also showed that marizomib triggers synergistic anti-MM activity in combination with lenalidomide (Chauhan et al., Blood 2010, 115:834-45). Pomalidomide, like lenalidomide, is an analogue of thalidomide with potent immunomodulatory activity, and has been approved by FDA for treatment of RRMM patients who have received at least two prior therapies including lenalidomide and bortezomib and showed disease progression on or within 60 days of completion of the last therapy. Approval of treatment is based on progression-free survival. Here we utilized in vitro and in vivo models of MM to examine the anti-MM activity of combined marizomib and pomalidomide. Materials and Methods:MM celllines, patient tumor cells, and peripheral blood mononuclear cells (PBMCs) from normal healthy donors were utilized to assess the anti-MM activity of marizomib and pomalidomide. Cell viability, apoptosis, and migration assays were performed using WST/MTT, Annexin V staining, and Transwell Inserts, respectively. Synergistic/additive anti-MM activity was analyzed by isobologram analysisusing “CalcuSyn” software program. Proteasome activity was measured, as previously described (Chauhan et al., Cancer Cell 2005, 8:407-419). In vitro angiogenesis was assessed using matrigel capillary-like tube structure formation assays. MM.1S-tumor-bearing mice were treated with vehicle control, marizomib, pomalidomide or marizomib plus pomalidomide at the indicated doses for 21 days on a twice-weekly schedule for marizomib and 4 consecutive days weekly for pomalidomide. Statistical significance was determined using a Student’s t test. Pomalidomide was purchased from Selleck chemicals, USA; and marizomib was obtained from Triphase Inc., USA. Results: MM cell lines (MM.1S, MM.1R, INA-6, RPMI-8226, Dox-40, U266, LR5, ANBL6.WT, and ANBL6.BR) and primary patient MM cells were pretreated with DMSO control or with pomalidomide for 24h; marizomib was then added for an additional 24h, followed by assessment of cell viability. A significant decrease in viability of all cell lines and patient cells was observed in response to treatment with combined low doses of marizomib and pomalidomide, compared with either agent alone. Isobologram analysis confirmed the synergistic anti-MM activity of these agents (CI < 1.0). Tumor cells from 5 of 7 patients were obtained from patients whose disease was progressing while on bortezomib, dexamethasone, and lenalidomide therapies. Moreover, the cytotoxicity of combination therapy was observed in MM cell lines sensitive and resistant to conventional (dex, doxorubicin, melphalan) and novel (bortezomib) therapies. No significant decrease in viability of PBMCs from normal healthy donors was observed in response to treatment with combined low doses of marizomib and pomalidomide, suggesting selective anti-MM activity and a favorable therapeutic index for this combination regimen. Furthermore, marizomib plus pomalidomide inhibits proliferation of MM cells even in the presence of BM stromal cells. Mechanistic studies showed that marizomib plus pomalidomide-induced apoptosis was associated with: 1) activation of caspase-8, caspase-9, caspase-3, and PARP; 2) downregulation of Cereblon, IRF4, c-Myc, and Mcl-1; and 3) enhanced inhibition of chymotrypsin-like, caspase-like and trypsin-like proteasome activities versus single agent alone. Furthermore, combined low doses of marizomib and pomalidomide blocked migration of MM cells and angiogenesis. In vivo studies using a subcutaneous human MM xenograft models show that combined low doses of marizomib and pomalidomide are well tolerated, inhibit tumor growth, and prolong survival. Conclusion: Our preclinical studies in MM disease models support a clinical trial of combined marizomib and pomalidomide to improve outcome in patients with relapsed and refractory MM. Disclosures Richardson: Oncopeptides AB: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees; Millennium: Membership on an entity's Board of Directors or advisory committees. Trikha:Triphase Accelerator: Employment. Chauhan:Triphase Accelerator: Consultancy. Anderson:Celgene: Consultancy; Millenium: Consultancy; Onyx: Consultancy; Gilead: Consultancy; Sanofi Aventis: Consultancy; BMS: Consultancy; Oncopep/Acetylon: Equity Ownership.

A Novel Acanthoic Acid Analog NPI-1342 Blocks IκB Kinase-α and Trigger In Vitro and In Vivo cytotoxicity in Multiple Myeloma Cells

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 1841-1841
Author(s):  
Dharminder Chauhan ◽  
Ajita V. Singh ◽  
Arghya Ray ◽  
Teru Hideshima ◽  
Paul G. Richardson ◽  
...  
Keyword(s):  
Multiple Myeloma ◽  
Cell Growth ◽  
Board Of Directors ◽  
Tumor Cells ◽  
Cell Lines ◽  
Inhibitory Effect ◽  
Advisory Committees ◽  
Acid Analog

Abstract Abstract 1841 Introduction: The dimeric Nuclear Factor-kappa B (NF-κB) transcription factor plays a key role during multiple myeloma (MM) cell adhesion-induced cytokine secretion in bone marrow stromal cells, which in turn triggers MM cell growth in a paracrine manner. NF-κB signaling pathway is mediated via canonical (IKK-α/IKK-β/NEMO-P50/65 or NF-κB1) and non-canonical (IKK-α/IKK-α/NIK-p52/RelB or NF-κB2) components. Prior studies have also linked constitutive activation of non-canonical NF-κB pathway to genetic abnormalities/mutation, allowing for an autocrine growth of MM cells. Other recent studies showed that constitutive NF-κB activity in tumor cells from MM patients renders these cells refractory to inhibition by bortezomib; and in fact, that bortezomib induces canonical NF-κB activity. These reports provided the impetus for the development of an agent with ability to modulate canonical and/or non-canonical NF-κB axis, allowing for a more robust and specific inhibition of NF-κB. Recent research and development efforts at Nereus Pharmaceuticals, Inc., have identified a novel small molecule acanthoic acid analog NPI-1342 as a potent NF-κB inhibitor. Here, we examined the effects of NPI-1342 on canonical versus non-canonical NF-κB signaling pathways, as well as its anti-tumor activity against MM cells using both in vitro and in vivo model systems. Methods: We utilized MM.1S, MM.1R, RPMI-8226, U266, KMS12PE, NCI-H929, OCI-MY5, LR5, Dox-40, OPM1, and OPM2 human MM cell lines, as well as purified tumor cells from patients with MM. Cell viability assays were performed using MTT and Trypan blue exclusion assays. Signal transduction pathways were evaluated using immunoblot analysis, ELISA, and enzymology assays. Animal model studies were performed using the SCID-hu model, which recapitulates the human BM milieu in vivo. Results: We first examined the effects of NPI-1342 on lipopolysaccharides (LPS)-induced NF-κB activity. Results showed that NPI-1342 inhibits LPS-stimulated NF-κB activity in vitro, as measured by phosphorylation of IkBa. To determine whether NPI-1342 triggers a differential inhibitory effect on IKKβ versus IKKα, MM.1S MM cells were treated with NPI-1342 for 48 hours, and protein lysates were subjected to kinase activity assays. NPI-1342 blocked IKKα, but not IKKβ or IKKγ phosphorylation. We next assessed whether the inhibitory effect of NPI-1342 on NF-κB activity is associated with cytotoxicity in MM cells. We utilized a panel of MM cell lines: at least five of these have mutations of TRAF3 (MM.1S, MM.1R, DOX40 and U266); one has no known NF-κB mutations (OPM2), and one has amplification of NF-κB1 (OCI-MY5). Treatment of MM cell lines and primary patient (CD138 positive) MM cells for 48 hours significantly decreased their viability (IC50 range 15–20 μM) (P < 0.001; n=3) without affecting the viability of normal peripheral blood mononuclear cells, suggesting selective anti-MM activity and a favorable therapeutic index for NPI-1342. NPI-1342-induced a marked increase in Annexin V+ and PI- apoptotic cell population (P < 0.001, n=3). Mechanistic studies showed that NPI-1342-triggered apoptosis in MM cells is associated with activation of caspase-8, caspase-9, caspase-3, and PARP cleavage. We next examined the in vivo effects of NPI-1342 in human MM xenograft models. For these studies, we utilized the SCID-hu MM model, which recapitulates the human BM milieu in vivo. In this model, MM cells are injected directly into human bone chips implanted subcutaneously in SCID mice, and MM cell growth is assessed by serial measurements of circulating levels of soluble human IL-6R in mouse serum. Treatment of tumor-bearing mice with NPI-1342 (20 mg/kg intraperitoneally, QD1-5 for 2 weeks), but not vehicle alone, significantly inhibits MM tumor growth in these mice (10 mice each group; P = 0.004). The doses of NPI-1342 were well tolerated by the mice, without significant weight loss. Finally, immunostaining of implanted human bone showed robust apoptosis and blockade of NF-κB in mice treated with NPI-1342 versus vehicle alone. Conclusions: We demonstrate the efficacy of a novel small molecule inhibitor of NF-κB NPI-1342 in MM using both in vitro and in vivo models. NPI-1342 blocks NF-κB activity with a preferential inhibitory activity against IKK-α component of NF-κB signaling. Our preclinical studies support evaluation of NPI-1342 as a potential MM therapy. Disclosures: Hideshima: Acetylon: Consultancy. Richardson:Millennium: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees; Johnson & Johnson: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees; Bristol Myers Squibb: Membership on an entity's Board of Directors or advisory committees. Palladino:Nereus Pharmaceuticals, Inc: Employment, Equity Ownership. Anderson:Celgene: Consultancy; Millennium: Consultancy; Onyx: Consultancy; Merck: Consultancy; Bristol Myers Squibb: Consultancy; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees; Acetylon:; Nereus Pharmaceuticals, Inc: Consultancy.

TAS-117, a Novel Selective Akt Inhibitor Demonstrates Significant Growth Inhibition in Multiple Myeloma Cells in Vitro and in Vivo

Blood ◽  
2012 ◽  
Vol 120 (21) ◽  
pp. 942-942 ◽  
Author(s):  
Naoya Mimura ◽  
Hiroto Ohguchi ◽  
Diana Cirstea ◽  
Francesca Cottini ◽  
Gullu Topal Gorgun ◽  
...  
Keyword(s):  
Multiple Myeloma ◽  
Drug Resistance ◽  
Cell Growth ◽  
Board Of Directors ◽  
Cell Lines ◽  
Akt Inhibitor ◽  
Advisory Committees ◽  
Significant Growth Inhibition

Abstract Abstract 942 The PI3K/Akt pathway mediates multiple myeloma (MM) cell growth and drug resistance, and targeting this molecule is a promising therapeutic option. In this study, we examined anti-MM activities of TAS-117 (TAIHO PHARMACEUTICAL CO., LTD., JAPAN), a selective potent Akt inhibitor in MM cell lines including MM.1S, MM.1R, OPM1 and H929 cells with high level of baseline Akt phosphorylation. TAS-117 induced significant growth inhibition in these cell lines, associated with downregulation of phosphorylation (Ser473 and Thr308) of Akt and downstream molecule FKHR/FKHRL1, without cytotoxicity in normal peripheral blood mononuclear cells. TAS-117 triggered G0/G1 arrest followed by apoptosis, evidenced by increased annexin V-positive cells, in both MM.1S and H929 cell lines. Apoptosis was further confirmed by cleavage of caspase-8, -3 and PARP. Interestingly, TAS-117 also induced: autophagy, evidenced by increased LC3-II; as well as endoplasmic reticulum (ER) stress, confirmed by induction of phospho-eIF2α, phospho-IRE1α and a molecular chaperone BiP/GRP78. Since the bone marrow (BM) microenvironment plays a crucial role in MM cell pathogenesis including drug resistance, we further examined the effect of TAS-117 in the presence of BM stromal cells (BMSCs). TAS-117 induced significant cytotoxicity in MM cells even in the presence of BMSCs, associated with downregulation of phospho-Akt. Importantly, TAS-117 inhibited secretion of IL-6 from BMSCs, and exogenous IL-6 and IGF-1 did not block cytotoxicity induced by this agent. We have previously shown the bortezomib activates Akt, and that Akt inhibition with bortezomib triggers synergistic MM cell cytotoxicity. TAS-117 enhanced bortezomib-induced cytotoxicity in MM.1S cells, associated with increased CHOP followed by PARP cleavage, suggesting that TAS-117 augments bortezomib-induced ER stress and apoptotic signaling. TAS-117 also enhanced cytotoxicity induced by other therapeutic agents (ie, rapamycin, dexamethasone, 17-AAG) in MM.1S cells. Finally, we examined anti-MM activities of TAS-117 in a xenograft murine model. Oral administration of TAS-117 for 14 days significantly inhibited growth of H929 plasmacytoma and was well tolerated. Taken together, the novel and selective Akt inhibitor TAS-117 blocks MM cell growth in vitro and in vivo, providing the preclinical framework for clinical evaluation of this agent to improve patient outcome in MM. Disclosures: Shimomura: TAIHO PHARMACEUTICAL CO., LTD.: Employment. Utsugi:TAIHO PHARMACEUTICAL CO., LTD.: Membership on an entity's Board of Directors or advisory committees. Anderson:Celgene, Millennium, BMS, Onyx: Membership on an entity's Board of Directors or advisory committees; Acetylon, Oncopep: Scientific Founder, Scientific Founder Other.

Preclinical Studies of Salinomycin In Multiple Myeloma (MM) Models: Targeting of Side Population (SP) Cells In the Context of Tumor – Microenvironment Interactions.

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 1574-1574
Author(s):  
Efstathios Kastritis ◽  
Jana Jakubikova ◽  
Jake Delmore ◽  
Steffen Klippel ◽  
Douglas W. McMillin ◽  
...  
Keyword(s):  
Breast Cancer ◽  
Stem Cell ◽  
Board Of Directors ◽  
Tumor Cells ◽  
Cell Lines ◽  
Research Funding ◽  
Advisory Committees ◽  
Ic50 Values

Abstract Abstract 1574 Cancer cells with stem cell-like features are a topic of intense research because their resistance to existing drugs is considered a culprit for relapses, even in patients with complete remission defined by clinical, biochemical and imaging parameters or by sensitive molecular techniques. Salinomycin, an antibacterial and coccidiodostatic ionophore, is reported (Cell 2009;138(4):645-59) to be >100-fold more potent against breast cancer cells with stem cell-like phenotype after mesenchymal transdifferentiation due to stable transfection with shRNA against CDH1 than against the parental cells. We evaluated whether salinomycin could also exhibit a similar activity against stem cell-like cells in multiple myeloma (MM). To establish a comparative reference for such potential activity, we first tested salinomycin (0-10 uM for up to 72hrs) against a panel of 15 MM cell lines and observed IC50 values <1 uM in 10/15 cell lines tested, including >80% reduction of tumor cell viability in 6/15 cell lines tested at 0.5 uM, i.e. levels lower than the IC50 values for in vitro activity of salinomycin against breast cancer cells with (HMLE-shCDH1, IC50 ∼1 uM) or without (HMLE-shControl, IC50 >>10 uM) stem cell-like features. CD138+ purified primary tumor cells from 3 MM patients responded to salinomycin with IC50 values (105, 332 and 750 nM, respectively) in the same range as MM cell lines. In vitro combinations with bortezomib, doxorubicin, melphalan, and dexamethasone showed overall no antagonism, while evidence of additive or even synergistic effect could be identified in certain dose ranges. Because MM cell lines and primary tumor cells responded concordantly to salinomycin and with higher sensitivity than breast cancer stem cell-like cells, we hypothesized that MM cells may in general be more responsive to salinomycin than other tumors. Since tumor-stromal interactions can increase the expression of transcriptional signatures of “stemness” in MM cells, we embarked on characterizing the anti-MM properties of salinomycin using compartment-specific bioluminescence imaging (CSBLI) assays. These showed that co-culture with stromal cells did not confer resistance to salinomycin in 5 MM cell lines (MM.1S, OCI-My5, KMS-11, KMS-18, NCI-H929) and in fact enhanced its activity against 4 of them. Side population (SP) cells, defined by their ability to efflux Hoechst stain, represent a stem cell-like population which was identified in MM cell lines and could represent the functional equivalent of the mesenchymally transdifferentiated breast cancer stem cell-like cells. We observed that salinomycin reduces the SP fraction of MM cell lines at doses >20 times lower than those required for in vitro effect against the bulk <<main population>> of the respective cell lines. Interestingly, the anti-SP effect of salinomycin was more pronounced in the presence of stroma, similarly to the CSBLI studies on the entire MM cell population and consistent with our prior observation that tumor-stroma interaction enhances transcriptional signatures of ≪stemness≫ in the tumor compartment. However, when we tested the in vivo anti-MM activity of salinomycin in an orthotopic model of i.v. injected Luc+ MM cells, no anti-MM activity (in terms of tumor burden decrease or overall survival prolongation) was observed at the maximum tolerated dose (1 mg/kg i.p. daily, which is consistent with most studies reported thus far in the literature). Ex vivo treatment of KMS-11 cells with salinomycin doses (100 nM for 72 hrs) selectively targeting SP cells was followed by s.c. injection of these cells or vehicle-treated controls in sublethallly irradiated SCID/NOD mice, but no statistically significant improvement in tumor burden or overall survival was observed. Our in vitro results indicate that salinomycin exhibits intriguing in vitro anti-MM activity, not only against SP cells but also against the bulk ≪main≫ MM cell population, even in the presence of stromal support. In contrast, the in vivo activity of salinomycin is compromised by side effects in the orthotopic model of MM lesions, while short term ex vivo exposure of tumor cells is conceivably insufficient to eradicate clonogenic cells and lead to appreciable delay in tumor growth in vivo. Our studies point to intriguing features as well as notable challenges that have to overcome before salinomycin or other more selective agents of this class can be safely tested in clinical trials in MM. Disclosures: McMillin: Axios Biosciences: Equity Ownership. Richardson:Celgene: Membership on an entity's Board of Directors or advisory committees; Millenium: Membership on an entity's Board of Directors or advisory committees. Anderson:Millennium Pharmaceuticals: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau. Mitsiades:Millennium: Consultancy, Honoraria; Novartis Pharmaceuticals: Consultancy, Honoraria; Bristol-Myers Squibb: Consultancy, Honoraria; Merck &Co.: Consultancy, Honoraria; Kosan Pharmaceuticals: Consultancy, Honoraria; Pharmion: Consultancy, Honoraria; Centrocor: Consultancy, Honoraria; PharmaMar: Patents & Royalties; OSI Pharmaceuticals: Research Funding; Amgen Pharmaceuticals: Research Funding; AVEO Pharma: Research Funding; EMD Serono: Research Funding; Sunesis: Research Funding; Gloucester Pharmaceuticals: Research Funding.

Effect of a novel agent, SL-401, targeting interleukin-3 (IL-3)-receptor on plasmacytoid dendritic cell (pDC)-induced myeloma cell growth and drug resistance.

2013 ◽  
Vol 31 (15_suppl) ◽  
pp. 8582-8582
Author(s):  
Dharminder Chauhan ◽  
Arghya Ray ◽  
Christopher Brooks ◽  
Eric K. Rowinsky ◽  
Kenneth Carl Anderson
Keyword(s):  
Drug Resistance ◽  
Cell Growth ◽  
Cell Lines ◽  
Plasmacytoid Dendritic Cell ◽  
Myeloma Cell ◽  
Healthy Donors ◽  
Signaling Axis ◽  
Novel Therapeutic Strategies

8582 Background: Multiple myeloma (MM) remains incurable despite novel therapies, highlighting the need for further identification of factors mediating disease progression and drug resistance. The bone marrow (BM) microenvironment confers growth, survival, and drug resistance in MM cells. Our recent study utilized in vitro and in vivo MM xenograft models to show that plasmacytoid dendritic cells (pDCs) were significantly increased in MM BM and promote MM growth (Chauhan et al., Cancer Cell 2009, 16:309). Importantly, we found increased IL-3 levels upon pDC-MM interaction, which in turn, trigger MM cell growth and pDCs survival. IL-3R is highly expressed on pDCs. We utilized SL-401, a novel biologic conjugate that targets IL-3R, to examine whether abrogation of IL-3–IL-3R signaling axis affects pDC-MM interaction and its tumor promoting sequelae. Methods: MM cell lines, patient MM cells, and pDCs from healthy donors or MM patients were utilized to study the anti-MM activity of SL-401. MM cells and pDCs were cultured alone or together in the presence or absence of SL-401, followed by analysis of cell growth or viability. Results: SL-401 significantly decreased the viability of pDCs at low concentrations (IC50: 0.83 ng/ml; P < 0.005, n = 3). SL-401 also decreased the viability of MM cells at clinically achievable doses. Co-culture of pDCs with MM cells induced growth of MM cell lines; and importantly, low doses (0.8 ng/ml) of SL-401 blocked MM cell growth-promoting activity of pDCs. MM patient-derived pDCs induced growth of MM cell lines and primary MM cells as well; conversely, SL-401 inhibited pDC-triggered MM cell growth (P < 0.005, n= 5). Tumor cells from 3 of the 5 patients were from patients whose disease was progressing while on bortezomib, dexamethasone, and lenalidomide therapies. In agreement with these results, SL-401 blocked pDC-induced growth of dexamethasone-resistant MM cell lines. Conclusions: Our study therefore provides the basis for directly targeting pDCs or blocking the pDC-MM interaction, as well as targeting MM, in novel therapeutic strategies with SL-401 to enhance MM cytotoxicity, overcome drug-resistance, and improve patient outcome.

scholarly journals Targeting Wnt/β-Catenin and BCL-2, Two Critical Survival Factors, Synergistically Induces Apoptosis in AML Via Rac1-Mediated MCL-1 Inhibition

Blood ◽  
2018 ◽  
Vol 132 (Supplement 1) ◽  
pp. 1442-1442
Author(s):  
Xiangmeng Wang ◽  
Po Yee Mak ◽  
Wencai Ma ◽  
Xiaoping Su ◽  
Hong Mu ◽  
...  
Keyword(s):  
Progenitor Cells ◽  
Board Of Directors ◽  
Cell Lines ◽  
Research Funding ◽  
Single Agent ◽  
Advisory Committees ◽  
Equity Ownership ◽  
Critical Survival

Abstract Wnt/β-catenin signaling regulates self-renewal and proliferation of AML cells and is critical in AML initiation and progression. Overexpression of β-catenin is associated with poor prognosis. We previously reported that inhibition of Wnt/β-catenin signaling by C-82, a selective inhibitor of β-catenin/CBP, exerts anti-leukemia activity and synergistically potentiates FLT3 inhibitors in FLT3-mutated AML cells and stem/progenitor cells in vitro and in vivo (Jiang X et al., Clin Cancer Res, 2018, 24:2417). BCL-2 is a critical survival factor for AML cells and stem/progenitor cells and ABT-199 (Venetoclax), a selective BCL-2 inhibitor, has shown clinical activity in various hematological malignancies. However, when used alone, its efficacy in AML is limited. We and others have reported that ABT-199 can induce drug resistance by upregulating MCL-1, another key survival protein for AML stem/progenitor cells (Pan R et al., Cancer Cell 2017, 32:748; Lin KH et al, Sci Rep. 2016, 6:27696). We performed RNA Microarrays in OCI-AML3 cells treated with C-82, ABT-199, or the combination and found that both C-82 and the combination downregulated multiple genes, including Rac1. It was recently reported that inhibition of Rac1 by the pharmacological Rac1 inhibitor ZINC69391 decreased MCL-1 expression in AML cell line HL-60 cells (Cabrera M et al, Oncotarget. 2017, 8:98509). We therefore hypothesized that inhibiting β-catenin by C-82 may potentiate BCL-2 inhibitor ABT-199 via downregulating Rac1/MCL-1. To investigate the effects of simultaneously targeting β-catenin and BCL-2, we treated AML cell lines and primary patient samples with C-82 and ABT-199 and found that inhibition of Wnt/β-catenin signaling significantly enhanced the potency of ABT-199 in AML cell lines, even when AML cells were co-cultured with mesenchymal stromal cells (MSCs). The combination of C-82 and ABT-199 also synergistically killed primary AML cells (P<0.001 vs control, C-82, and ABT-199) in 10 out of 11 samples (CI=0.394±0.063, n=10). This synergy was also shown when AML cells were co-cultured with MSCs (P<0.001 vs control, C-82, and ABT-199) in all 11 samples (CI=0.390±0.065, n=11). Importantly, the combination also synergistically killed CD34+ AML stem/progenitor cells cultured alone or co-cultured with MSCs. To examine the effect of C-82 and ABT-199 combination in vivo, we generated a patient-derived xenograft (PDX) model from an AML patient who had mutations in NPM1, FLT3 (FLT3-ITD), TET2, DNMT3A, and WT1 genes and a complex karyotype. The combination synergistically killed the PDX cells in vitro even under MSC co-culture conditions. After PDX cells had engrafted in NSG (NOD-SCID IL2Rgnull) mice, the mice were randomized into 4 groups (n=10/group) and treated with vehicle, C-82 (80 mg/kg, daily i.p injection), ABT-199 (100 mg/kg, daily oral gavage), or the combination for 30 days. Results showed that all treatments decreased circulating blasts (P=0.009 for C-82, P<0.0001 for ABT-199 and the combination) and that the combination was more effective than each single agent (P<0.001 vs C-82 or ABT-199) at 2 weeks of therapy. The combination also significantly decreased the leukemia burden in mouse spleens compared with controls (P=0.0046) and single agent treated groups (P=0.032 or P=0.020 vs C-82 or ABT-199, respectively) at the end of the treatment. However, the combination did not prolong survival time, likely in part due to toxicity. Dose modifications are ongoing. These results suggest that targeting Wnt/β-catenin and BCL-2, both essential for AML cell and stem cell survival, has synergistic activity via Rac1-mediated MCL-1 inhibition and could be developed into a novel combinatorial therapy for AML. Disclosures Andreeff: SentiBio: Equity Ownership; Oncolyze: Equity Ownership; Oncoceutics: Equity Ownership, Membership on an entity's Board of Directors or advisory committees; Jazz Pharma: Consultancy; Amgen: Consultancy, Research Funding; Eutropics: Equity Ownership, Membership on an entity's Board of Directors or advisory committees; Daiichi-Sankyo: Consultancy, Patents & Royalties: MDM2 inhibitor activity patent, Research Funding; Aptose: Equity Ownership, Membership on an entity's Board of Directors or advisory committees; Reata: Equity Ownership; Astra Zeneca: Research Funding; Celgene: Consultancy; United Therapeutics: Patents & Royalties: GD2 inhibition in breast cancer . Carter:novartis: Research Funding; AstraZeneca: Research Funding.

scholarly journals Activation of the Unfolded Protein Response with the First-in-Class P97 Inhibitor CB-5083 Induces Stable Disease Regression and Overcomes Ara-C Resistance in AML

Blood ◽  
2015 ◽  
Vol 126 (23) ◽  
pp. 1350-1350
Author(s):  
Steffan T. Nawrocki ◽  
Yingchun Han ◽  
Ronan LE Moigne ◽  
Valeria Visconte ◽  
Bartlomiej Przychodzen ◽  
...  
Keyword(s):  
Unfolded Protein Response ◽  
Board Of Directors ◽  
Cell Lines ◽  
Primary Cells ◽  
Advisory Committees ◽  
Unfolded Protein ◽  
The Unfolded Protein Response ◽  
Protein Response

Abstract Acute myeloid leukemia (AML) therapy has remained relatively unchanged for more than 40 years with the majority of patients not achieving long-term remission when treated with currently available agents. Novel strategies are urgently needed to improve outcomes. The constitutive dysregulation of protein synthesis/turnover contributes to disease progression and drug resistance in many forms of cancer including AML. p97 (VCP) is a master regulator of protein turnover that has been implicated in oncogenesis and malignant pathogenesis. CB-5083 is a first-in-class selective and potent orally available inhibitor of p97 that in currently being evaluated in phase I clinical trials in patients with multiple myeloma and advanced solid tumors. To assess the potential benefit of p97 inhibition as a novel approach for AML therapy, we investigated the efficacy, pharmacodynamics (PD), and pharmacokinetics (PK) of CB-5083 in a panel of human AML cell lines with diverse genetic backgrounds, primary AML specimens from both newly diagnosed and relapsed/refractory patients, and xenograft mouse models of AML. In vitro treatment with CB-5083 potently diminished the viability of AML cell lines (n = 7) and primary CD34+ blasts obtained from patients (n = 10) with IC50s significantly below 1 µM (range 200 - 700 nM) in all lines and specimens evaluated to date. Diminished viability was associated with reduced clonogenic survival and increased apoptosis in AML cell lines and primary blasts. In contrast to many conventional and experimental drugs that are less active against primary AML cells than established AML cell lines, primary cells exhibited sensitivity to CB-5083 that was similar to cell lines. Additionally, CB-5083 was highly active in 3 different cell line models of cytarabine resistance and primary cells from refractory AML patients. This suggests that CB-5083 may be effective for patients who are relapsed/refractory to conventional therapy. In vitro PD analyses demonstrated that CB-5083 rapidly triggered the accumulation of ubiquitin-conjugated proteins, activated the unfolded protein response (UPR), disrupted STAT5 signaling, reduced levels of key STAT5 targets including BCL-xL and PIM-2, and induced apoptosis. The pro-apoptotic effects of CB-5083 were associated with activation of the endoplasmic reticulum (ER) resident initiator caspase-4 and induction of the BH3-only protein NOXA, which has been previously demonstrated to be an important mediator of cell death induced by other agents that disrupt protein homeostasis. RNA sequencing (RNASeq) gene ontology (GO) analyses of MV4-11 and MOLM-13 AML cells following treatment with CB-5083 demonstrated that short-term treatment (6h) caused significant increases in multiple regulators of the unfolded protein response, protein biosynthesis, and other ubiquitin-related pathways (p<0.001). Results were confirmed by qRT-PCR. The in vivo anti-leukemic activity of CB-5083 was investigated in two different xenograft mouse models of AML: the FLT3-ITD+ MV4-11 cell line and APML HL-60 cells. Oral administration of CB-5083 (once daily, 4 days on, 3 days off) was well tolerated and induced disease regression in both xenograft models (p<0.01). In vivo PD studies demonstrated that administration of CB-5083 led to reduced AML cell proliferation (PCNA), to the induction of apoptosis (active caspase-3), and pathway inhibition as evidenced by poly-ubiquitin accumulation and elevated expression of CHOP, GRP78, and NOXA. PK-PD analyses demonstrated a correlation between the kinetics of the in vivo PD effects and drug exposure. Our collective preclinical data demonstrate that p97 inhibition is a very effective novel anti-leukemic strategy and support clinical investigation of CB-5083 in patients with relapsed/refractory AML. Disclosures LE Moigne: Cleave Biosciences: Employment. Rolfe:Cleave Biosciences: Employment. Djakovic:Cleave Biosciences: Employment. Anderson:Cleave Biosciences: Employment. Wustrow:Cleave Biosciences: Employment. Zhou:Cleave Biosciences: Employment. Wong:Cleave Biosciences: Employment. Sekeres:TetraLogic: Membership on an entity's Board of Directors or advisory committees; Celgene Corporation: Membership on an entity's Board of Directors or advisory committees; Amgen: Membership on an entity's Board of Directors or advisory committees. Carew:Boehringer Ingelheim: Research Funding.

scholarly journals In Vitro and inVivo Activity of Melflufen in Amyloidosis

Blood ◽  
2019 ◽  
Vol 134 (Supplement_1) ◽  
pp. 3100-3100 ◽  
Author(s):  
Ken Flanagan ◽  
Muntasir M Majumder ◽  
Romika Kumari ◽  
Juho Miettinen ◽  
Ana Slipicevic ◽  
...  
Keyword(s):  
Board Of Directors ◽  
Cell Lines ◽  
Plasma Cell ◽  
Light Chain ◽  
Research Funding ◽  
Plasma Cells ◽  
Al Amyloidosis ◽  
Advisory Committees

Background: Immunoglobulin light-chain (AL) amyloidosis is a rare disease caused by plasma cell secretion of misfolded light chains that assemble as amyloid fibrils and deposit on vital organs including the heart and kidneys, causing organ dysfunction. Plasma cell directed therapeutics, aimed at preferentially eliminating the clonal population of amyloidogenic cells in bone marrow are expected to reduce production of toxic light chain and alleviate deposition of amyloid thereby restoring healthy organ function. Melphalan flufenamide ethyl ester, melflufen, is a peptidase potentiated alkylating agent with potent toxicity in myeloma cells. Melflufen is highly lipophilic, permitting rapid cellular uptake, and is subsequently enzymatically cleaved by aminopeptidases within cells resulting in augmented intracellular concentrations of toxic molecules, providing a more targeted and localized treatment. Previous data demonstrating multiple myeloma plasma cell sensitivity for melflufen suggests that the drug might be useful to directly eliminate amyloidogenic plasma cells, thereby reducing the amyloid load in patients. Furthermore, the increased intracellular concentrations of melflufen in myeloma cells indicates a potential reduction in systemic toxicity in patients, an important factor in the fragile amyloidosis patient population. To assess potential efficacy in amyloidosis patients and to explore the mechanism of action, we examined effects of melflufen on amyloidogenic plasma cells invitro and invivo. Methods: Cellular toxicity and apoptosis were measured in response to either melflufen or melphalan in multiple malignant human plasma cell lines, including the amyloidosis patient derived light chain secreting ALMC-1 and ALMC-2 cells, as well as primary bone marrow cells from AL amyloidosis patients, using annexin V and live/dead cell staining by multicolor flow cytometry, and measurement of cleaved caspases. Lambda light chain was measured in supernatant by ELISA, and intracellular levels were detected by flow cytometry. To assess efficacy of melflufen in vivo, the light chain secreting human myeloma cell line, JJN3, was transduced with luciferase and adoptively transferred into NSG mice. Cell death in response to melflufen or melphalan was measured by in vivo bioluminescence, and serum light chain was monitored. Results: Melflufen demonstrated increased potency against multiple myeloma cell lines compared to melphalan, inducing malignant plasma cell death at lower doses on established light chain secreting plasma cell lines. While ALMC-1 cells were sensitive to both melphalan and melflufen, the IC50 for melphalan at 960 nM was approximately 3-fold higher than melflufen (334 nM). However, ALMC-2 cells were relatively insensitive to melphalan (12600 nM), but maintained a 100-fold increase in sensitivity to melflufen (121 nM). Furthermore, while 40% of primary CD138+ plasma cells from patients with diagnosed AL amyloidosis responded to melflufen treatment in vitro, only 20% responded to melphalan with consistently superior IC50 values for melflufen (Figure 1). Light chain secreting cell lines and AL amyloidosis patient samples were further analyzed by single cell sequencing. We further examined differential effects on apoptosis and the unfolded protein response in vitro in response to either melflufen or melphalan. This is of particular interest in amyloidosis, where malignant antibody producing plasma cells possess an increased requirement for mechanisms to cope with the amplified load of unfolded protein and associated ER stress. As AL amyloidosis is ultimately a disease mediated by secretion of toxic immunoglobulin, we assessed the effects of melflufen on the production of light chain invitro, measuring a decrease in production of light chain in response to melflufen treatment. Finally, we took advantage of a recently described adoptive transfer mouse model of amyloidosis to assess the efficacy of melflufen and melphalan in eliminating amyloidogenic clones and reducing the levels of toxic serum light chain in vivo. Conclusions: These findings provide evidence that melflufen mediated toxicity, previously described in myeloma cells, extends to amyloidogenic plasma cells and further affects the ability of these cells to produce and secrete toxic light chain. This data supports the rationale for the evaluation of melflufen in patients with AL amyloidosis. Figure 1 Disclosures Flanagan: Oncopeptides AB: Employment. Slipicevic:Oncopeptides AB: Employment. Holstein:Celgene: Consultancy; Takeda: Membership on an entity's Board of Directors or advisory committees; Adaptive Biotechnologies: Membership on an entity's Board of Directors or advisory committees; GSK: Consultancy; Genentech: Membership on an entity's Board of Directors or advisory committees; Sorrento: Consultancy. Lehmann:Oncopeptides AB: Employment. Nupponen:Oncopeptides AB: Employment. Heckman:Celgene: Research Funding; Novartis: Research Funding; Oncopeptides: Research Funding; Orion Pharma: Research Funding.

A NOVEL Aurora A Kinase INHIBITOR MLN8237 Induces Cytotoxicity and CELL Cycle Arrest IN MULTIPLE MYELOMA.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 3830-3830
Author(s):  
Gullu Gorgun ◽  
Elisabetta Calabrese ◽  
Teru Hideshima ◽  
Jeffrey Ecsedy ◽  
Giada Bianchi ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Board Of Directors ◽  
Cell Lines ◽  
Mitotic Spindle ◽  
Research Funding ◽  
Thymidine Incorporation ◽  
Aurora A Kinase ◽  
Advisory Committees

Abstract Abstract 3830 Poster Board III-766 Multiple myeloma (MM) is an incurable bone marrow derived plasma cell malignancy. Despite significant improvements in treating patients suffering from this disease, MM remains uniformly fatal due to intrinsic or acquired drug resistance. Thus, additional modalities for treating MM are required. Targeting cell cycle progression proteins provides such a novel treatment strategy. Here we assess the in vivo and in vitro anti-MM activity of MLN8237, a small molecule Aurora A kinase (AURKA) inhibitor. AURKA is a mitotic kinase that localizes to centrosomes and the proximal mitotic spindle, where it functions in mitotic spindle formation and in regulating chromatid congression and segregation. In MM, increased AURKA gene expression has been correlated with centrosome amplification and a worse prognosis; thus, inhibition of AURKA in MM may prove to be therapeutically beneficial. Here we show that AURKA protein is highly expressed in eight MM cell lines and primary patient MM cells. The affect of AURKA inhibition was examined using cytotoxicity (MTT viability) and proliferation (3[H]thymidine incorporation) assays after treatment of these cell lines and primary cells with MLN8237 (0.0001 μM – 4 μM) for 24, 48 and 72h Although there was no significant inhibition of cell viability and proliferation at 24h, a marked effect on both viability and proliferation occurred after 48 and 72h treatment at concentrations as low as 0.01 μM. Moreover, MLN8237 inhibits cell growth and proliferation of primary MM cells and cell lines even in the presence of bone marrow stromal cells (BMSCs) or cytokines IL-6 and IGF1. Similar experiments revealed that MLN8237 did not induce cytotoxicity in normal peripheral blood mononuclear cells (PBMCs) as measured by MTT assay, but did inhibit proliferation at 48 and 72h, as measured by the 3[H]thymidine incorporation assay. To delineate the mechanisms of cytotoxicity and growth inhibitory activity of MLN8237, apoptotic markers and cell cycle profiles were examined in both MM cell lines and primary MM cells. Annexin V and propidium iodide staining of MM cell lines cultured in the presence or absence of MLN8237 (1 μM) for 24, 48 and 72h demonstrated apoptosis, which was further confirmed by increased cleavage of PARP, capase-9, and caspase-3 by immunoblotting. In addition, MLN8237 upregulated p53-phospho (Ser 15) and tumor suppressor genes p21 and p27. Cell cycle analysis demonstrated that MLN8237 treatment induces an accumulation of tetraploid cells by abrogating G2/M progression. We next determined whether combining MLN8237 with conventional (melphalan, doxorubucin, dexamethasone) and other novel (VELCADE®) therapeutic agents elicited synergistic/additive anti-MM activity by isobologram analysis using CalcuSyn software. Combining MLN8237 with melphalan, dexamethasone, or VELCADE® induces synergistic/additive anti-MM activity against MM cell lines in vitro (p≤0.05, CI<1). To confirm in vivo anti-MM effects of MLN8237, MM.1S cells were injected s.c. into g-irradiated CB-17 SCID mice (n=40, 10 mice EA group). When tumors were measurable (>100 mm3), mice were treated with daily oral doses of vehicle alone or 7.5mg/kg, 15mg/kg, 30mg/kg MLN8237 for 21 days. Overall survival (defined as time between initiation of treatment and sacrifice or death) was compared in vehicle versus- MLN8237- treated mice by Kaplan-Meier method. Tumor burden was significantly reduced (p=0.02) and overall survival was significantly increased (p=0.02, log-rank test) in animals treated with 30mg/kg MLN8237. In vivo anti-MM effects of MLN8237 were further validated by performing TUNEL apoptosis-cell death assay in tumor tissues excised from control or treated animals. Importantly, a significant dose-related increase in apoptotic cells was observed in tumors from animals that received MLN8237 versus controls. These results suggest that MLN8237 represents a promising novel targeted therapy in MM. Disclosures: Ecsedy: Millennium Pharmaceutical: Employment. Munshi:Celgene: Membership on an entity's Board of Directors or advisory committees; Millennium: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees. Richardson:Celgene: Membership on an entity's Board of Directors or advisory committees; Millennium: Membership on an entity's Board of Directors or advisory committees. Anderson:Millennium: Research Funding; Novartis: Research Funding; Celgene: Research Funding.

A Novel SIRT1 Activator SIRT1720 Triggers In Vitro and In Vivo Cytotoxicity In Multiple Myeloma Via ATM-Dependent Mechanism

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 3007-3007
Author(s):  
Dharminder Chauhan ◽  
Madhavi Bandi ◽  
Ajita V Singh ◽  
Teru Hideshima ◽  
Nikhil C. Munshi ◽  
...  
Keyword(s):  
Multiple Myeloma ◽  
Board Of Directors ◽  
Cell Lines ◽  
Annexin V ◽  
Immunoblot Analysis ◽  
Advisory Committees ◽  
Rpmi 8226 ◽  
Sirt1 Activator

Abstract Abstract 3007 Background and Rationale: SIRT1 belongs to the silent information regulator 2 (Sir2) family of proteins and functions as NAD+-dependent deacetylase. Previous studies showed that resveratrol, a polyphenolic SIRT1 activator, inhibits tumorigenesis in various solid tumor and hematologic malignancies, including human multiple myeloma (MM) cells. This notion led to the discovery and development of more potent and selective pharmacological activators of SIRT1 as potential anti-cancer therapeutics. In this context, a recent medicinal chemistry research using high-throughput screening, and mass spectrometry identified SRT1720, a small molecule activator of SIRT1 that is structurally distinct from resveratrol. Here, we examined the anti-tumor activity of SRT1720 in MM cells using in vitro and in vivo model systems. Methods and Model: We utilized MM.1S, MM.1R, RPMI-8226, U266, KMS12BM, H929, and INA-6 (an IL-6 dependent) human MM cell lines, as well as purified tumor cells from patients with MM relapsing after prior therapies including lenalidomide or bortezomib. Cell viability, proliferation, and apoptosis assays were performed using trypan blue, MTT, thymidine incorporation, and Annexin V staining. Signal transduction pathways were evaluated using immunoblot analysis, ELISA, and enzymology assays. Results: We first confirmed the functional specificity of SRT1720 against SIRT1 using different experimental strategies. First, we utilized Fluor de Lys Deacetylase Assay to measure whether SRT1720 affects the SIRT1 deacetylase enzymatic activity. Treatment of MM.1R and RPMI-8226 MM cells with SRT1720 markedly increased the deacetylating activity; conversely, pre-treatment of cells with nicotinamide (NAM) - an inhibitor of SIRT1 – significantly blocked SRT1720-triggered deacetylating activity. Second, immunoblot analysis using antibodies specific against acetylated p53 (a known substrate of SIRT1) showed a marked decrease in acetylated state of p53 in SRT1720-treated MM cells. These findings in MM cells confirm SIRT1 as a selective target of SRT1720. We next examined the efficacyof SRT1720 in MM cells. Treatment of MM cell lines and primary patient cells for 24h significantly decreased their viability (IC50 range 3–7 uM) (P < 0.005; n=3) without markedly affecting the viability of normal peripheral blood mononuclear cells, suggesting specific anti-MM activity and a favorable therapeutic index for SRT1720. SRT1720-triggered apoptosis was confirmed in MM.1R and RPMI-8226 cells, evidenced by a marked increase in Annexin V+ and PI- cell population (P < 0.001, n=3). Importantly, SRT1720 induced apoptosis in MM cells even in the presence of bone marrow stromal cells. Mechanistic studies showed that SRT1720-triggered apoptosis in MM cells is associated with 1) activation of caspase-8, caspase-9, caspase-3, and PARP; 2) activation of pATM, CHK2, endoplasmic reticulum stress molecules pEIF2, and BIP; as well as an increase in reactive oxygen species (ROS); 3) inhibition of MM cell growth and survival pathway via NF-kB; and 4) inhibition of VEGF-induced migration of MM cells and associated angiogenesis. Importantly, blockade of pATM using a biochemical inhibitor KU-5593 significantly attenuated SRT1720-induced MM cell death (P value < 0.002; n=2). These data suggest that SRT1720-induced MM cell apoptosis is predominantly mediated by an ATM-dependent apoptotic pathway. We next examined the in vivo efficacy of SRT1720 using a human plasmacytoma xenograft mouse model. Treatment of tumor-bearing mice with SRT1720 (200 mg/kg, 5 days a week for three weeks), but not vehicle alone, significantly (P < 0.008) inhibits MM tumor growth in these mice. Finally, the combination of SRT1720 with bortezomib or dexamethasone triggered synergistic anti-MM activity. Conclusions: These preclinical studies provide the rationale for novel therapeutics targeting SIRT1 to improve patient outcome in MM. Disclosures: Munshi: Millennium Pharmaceuticals: Honoraria, Speakers Bureau. Richardson:Celgene: Membership on an entity's Board of Directors or advisory committees; Millenium: Membership on an entity's Board of Directors or advisory committees. Anderson:Millennium Pharmaceuticals: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau.

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