Targeting IRE1α-XBP1 Pathway Is a Novel Therapeutic Strategy In Multiple Myeloma

Abstract Abstract 4074 Aberrant protein folding results in the accumulation of misfolded/unfolded proteins in the endoplasmic reticulum (ER), which in turn triggers ER stress followed by unfolded protein response (UPR), an adaptive response against ER stress. Since multiple myeloma (MM) cells have high protein synthesis, they are sensitive to ER stress and require strict ER quality control for cell survival. Upon UPR, IRE1α is activated by auto-phosphorylation resulting in activation of its endoribonuclease domain to splice XBP1 mRNA from XBP1 unspliced form (XBP1u: inactive) to XBP1 spliced form (XBP1s: active). Since XBP1 is a transcription factor regulating genes which are responsible for protein folding and ER associated degradation (ERAD), IRE1α-XBP1 pathway acts as a pro-survival signaling pathway under the UPR condition. In this study, we examined whether IRE1α-XBP1 pathway is a potential novel therapeutic option in MM. We first examined IRE1α expression and confirmed its expression in all MM cell lines. In contrast, XBP1s was not detected by RT-PCR in most cell lines except in for RPMI8226 cells. To assess biologic significance of IRE1α in MM cell, we knock-downed its expression using shRNA and found that downregulation of IRE1α inhibited MM cell growth, indicating that IRE1α has a crucial role in MM cell survival. We next examined the impact of inhibition of XBP1 splicing by a small molecule IRE1α endoribonuclease inhibitor MKC-3946 (Mannkind, Valencia CA) in MM cells in vitro. As expected, MKC-3946 significantly inhibited tunicamycin-induced XBP1s without affecting phosphorylation of IRE1α. MKC-3946 induced only modest cytotoxicity in MM cell lines without toxicity in normal mononuclear cells from healthy donors; however, it significantly enhanced cytotoxicity in combination with bortezomib or 17-AAG. Both bortezomib and 17-AAG induced ER stress evidenced by induction of XBP1s; conversely, MKC-3946 blocked XBP1s triggered by these agents. Furthermore, apoptosis induced by these agents was enhanced with MKC-3946 associated with increased CHOP, which is a known pro-apoptotic protein induced in uncompensated ER stress condition. Importantly, MKC-3946 enhanced the cytotoxicity of bortezomib or 17-AAG in INA6 cells, even in the presence of increased IL-6 or bone marrow stromal cells. Finally, MKC-3946 was active inhibiting XBP1 splicing in a model of ER stress and significantly inhibited growth of RPMI8226 plasmacytoma in a xenograft murine model when used in combination with a low dose of bortezomib. Taken together, our results demonstrate that inhibition of XBP1 splicing by blockade of IRE1α is a promising therapeutic option in MM. Disclosures: Blumenthal: Mannkind Corporation: Employment, Equity Ownership. Tam:Mannkind Corporation: Employment, Equity Ownership. Kertesz:Mannkind Corporation: Employment, Equity Ownership. Zeng:Mannkind Corporation: Employment, Equity Ownership. Patterson:Mannkind Corporation: Employment, Equity Ownership. 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; Johnson & Johnson: Membership on an entity's Board of Directors or advisory committees. Anderson: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.

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Blockade of XBP1 Splicing by Inhibition of IRE1α Is a Promising Therapeutic Option in Multiple Myeloma

Blood ◽

10.1182/blood.v118.21.133.133 ◽

2011 ◽

Vol 118 (21) ◽

pp. 133-133 ◽

Cited By ~ 2

Author(s):

Naoya Mimura ◽

Mariateresa Fulciniti ◽

Gullu Gorgun ◽

Yu-Tzu Tai ◽

Diana D. Cirstea ◽

...

Keyword(s):

Growth Inhibition ◽

Er Stress ◽

Board Of Directors ◽

Tumor Cells ◽

Therapeutic Option ◽

Rt Pcr ◽

Employment Equity ◽

Advisory Committees ◽

Equity Ownership

Abstract Abstract 133 Multiple myeloma (MM) cells are characterized by high protein synthesis resulting in chronic endoplasmic reticulum (ER) stress, which is adaptively managed by the unfolded protein response (UPR). Therefore blockade of UPR could provide a novel therapeutic option in MM. Upon UPR, inositol-requiring enzyme 1α (IRE1α) is activated by auto-phosphorylation, resulting in activation of its endoribonuclease domain to cleave XBP1 mRNA from XBP1 unspliced form (XBP1u: inactive) to generate the XBP1 spliced form (XBP1s: active). XBP1s protein in turn regulates genes responsible for protein folding and degradation, playing a pro-survival signaling role in the UPR. In this study, we specifically examined whether IRE1α-XBP1 pathway is a potential therapeutic target in MM. We first examined the biologic significance of IRE1α by knockdown using lentiviral shRNA and observed significant growth inhibition in IRE1α knockdown cells. We next examined the impact of inhibition of XBP1 splicing using a novel small molecule IRE1α endoribonuclease domain inhibitor MKC-3946 (MannKind, Valencia CA). MKC-3946 blocked not only the basal level, but also inducible (by tunicamycin) XBP1s, evidenced by RT-PCR analysis in RPMI8226 cells, without affecting phosphorylation of IRE1α. Importantly, MKC-3946 also inhibited XBP1s in primary tumor cells from MM patients. We also confirmed functional inhibition of XBP1s, with target genes including SEC61A1, p58IPK, and ERdj4 downregulated by MKC-3946 treatment. Importantly, MKC-3946 triggered growth inhibition in MM cell lines, without toxicity in normal mononuclear cells. Furthermore, it significantly enhanced cytotoxicity induced by bortezomib or 17-AAG in RPMI8226 and INA6 cells, as well as primary tumor cells from MM patients. Both bortezomib and 17-AAG induced ER stress with XBP1s, which was markedly blocked by MKC-3946. Moreover, apoptosis induced by bortezomib or 17-AAG was enhanced by MKC-3946, associated with increased CHOP mRNA and protein, a proapoptotic factor triggered by ER stress. We next demonstrated that XBP1s was induced by bortezomib in INA6 cells co-cultured with bone marrow (BM) stromal cells, which was inhibited by MKC-3946, associated with enhanced cytotoxicity induced by the combination. Finally, MKC-3946 inhibited XBP1s in a model of in vivo ER stress induced by tunicamycin. To evaluate the anti-MM effect of MKC-3946, we used the subcutaneous RPMI8226 xenograft model in mice. MKC-3946 significantly reduced MM tumor growth in the treatment versus control group, associated with prolonged overall survival. We also confirmed that MKC-3946 treatment significantly inhibited XBP1s in excised tumors, assessed by RT-PCR. In order to examine the activity of MKC-3946 on MM cell growth in the context of the human BM microenvironment in vivo, we used the SCID-hu model, in which INA6 cells are directly injected into a human bone chip implanted subcutaneously in SCID-mice. MKC-3946 treatment significantly inhibited tumor growth compared with vehicle control. Moreover, XBP1s in excised tumor cells was inhibited, evidenced by RT-PCR. In conclusion, these data demonstrate that blockade of XBP1s by MKC-3946 triggers MM cell growth inhibition in vivo and prolongs host survival. Taken together, our results demonstrate that blockade of XBP1 splicing by inhibition of IRE1α endoribonuclease domain is a potential novel therapeutic option in MM. Disclosures: Tam: MannKind Corporation: Employment, Equity Ownership. Zeng:MannKind Corporation: Employment, Equity Ownership. Patterson:MannKind Corporation: Employment, Equity Ownership. Richardson:Bristol Myers Squibb: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees; Johnson & Johnson: 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. Munshi:Millennium: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees. Anderson:Millennium: Membership on an entity's Board of Directors or advisory committees; Onyx: Membership on an entity's Board of Directors or advisory committees; MannKind: Membership on an entity's Board of Directors or advisory committees.

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Proteolytic Targeting Chimeric Molecules (PROTACs) Specific for Bromodomain-Containing Protein (BRD) 4 Are Active Against Pre-Clinical Models of Multiple Myeloma

Blood ◽

10.1182/blood.v126.23.917.917 ◽

2015 ◽

Vol 126 (23) ◽

pp. 917-917 ◽

Cited By ~ 1

Author(s):

Xiaohui Zhang ◽

Jing Lu ◽

Yimin Qian ◽

Robert Z. Orlowski

Keyword(s):

Multiple Myeloma ◽

Board Of Directors ◽

Cell Lines ◽

Research Funding ◽

Myeloma Cell ◽

Employment Equity ◽

Advisory Committees ◽

Clinical Models ◽

Equity Ownership ◽

Rpmi 8226

Abstract Background: BRD4, a bromodomain and extraterminal domain (BET) family member, has an important role in modulating the expression of essential oncogenes such as c-MYC, and is emerged as a promising therapeutic target in diverse cancer types. Pharmacologic BET inhibitors in development such as JQ1 and OTX015 display preclinical anti-myeloma activity, and induce preferential loss of BRD4 bound to super-enhancers leading to transcriptional repression of c-MYC. Another approach to target this pathway is through the use of bi-functional molecules, which incorporate a small molecule BRD4 binding moiety with an E3 ubiquitin ligase recognition motif, such as ARV-825 and dBET1 (Lu et al. Chem Biol. 22:755, 2015, Winter et al. Science 348:1376, 2015). These agents induce Cereblon (CRBN)-dependent BRD4 ubiquitination and then proteasome-mediated degradation, thereby also reducing downstream c-MYC protein levels. Methods: We performed pre-clinical studies in myeloma cell lines and primary samples using ARV-825 and ARV-763, which are PROTACs that target BRD4 to either the CRBN or the Von Hippel-Lindau (VHL) E3 ligases, respectively. Downstream effects were studied using viability and apoptosis assays, cell cycle profiling, and Western blotting, among others. Results: Tetrazolium assays showed that both PROTACs were able to reduce the viability of a panel of myeloma cell lines, including MM1.S, U266, RPMI 8226, ANBL-6, KAS-6/1, and OPM-2 cells, and this occurred with greater potency than was the case for the BRD4 inhibitors JQ1 or OTX015. Median inhibitory concentrations were 5.66-91.98 nM for ARV-825, and 13.22-1522 nM for ARV-763, respectively. This reduction in viability was both time- and concentration-dependent, and was associated with a reduction of cells in the S phase, and an increase in G0/G1 cells, as well as cells with sub-G0/G1 DNA content, suggesting the onset of apoptosis. Programmed cell death was indeed found to be induced based on the appearance of an increase in Annexin V-positive cells by flow cytometry, and in cleaved caspase 8, caspase 9, caspase 3, and poly-ADP-ribose polymerase by Western blotting. The latter was associated with a specific reduction in the expression levels of both BRD4 and c-MYC that did not influence the abundance of other cellular proteins that were not BRD4 targets, and in a reduction in BRD4 and c-MYC mRNA. In contrast, JQ1 and OTX015 exposure resulted in a slight increase in BRD4 protein expression and a lesser decrease of c-MYC protein. Studies of drug combinations showed that, as expected, lenalidomide and pomalidomide were antagonistic to the effects of the CRBN-targeted ARV-825 PROTAC, but these immunomodulatory drugs showed additive or synergistic effects in combination with the VHL-targeted agent ARV-763. Also as expected, bortezomib and carfilzomib reduced the ability of both ARV-825 and ARV-763 to induce BRD4 degradation, but enhanced anti-proliferative and pro-apoptotic effects were seen in a manner that was influenced by the sequence of drug addition. In studies of drug-resistant cell lines, both PROTACs were able to overcome dexamethasone, melphalan, lenalidomide, and bortezomib resistance, but cross-resistance was seen in RPMI 8226/Dox40 cells, suggesting that these compounds are substrates for P-glycoprotein, which is over-expressed in these cells. Finally, we tested BRD4 PROTACs in primary cells isolated from patients with multiple myeloma, and observed rapid loss of viability of these plasma cells. Conclusions: Taken together, our data demonstrate that BRD4 degraders have promising activity against pre-clinical models of multiple myeloma, and support their translation to the clinic for patients with relapsed/refractory disease. Additional combination and mechanistic studies, as well as data from ongoing in vivo studies, will be presented at the meeting. Disclosures Lu: Arvinas, LLC: Employment, Equity Ownership. Qian:Arvinas, LLC: Employment, Equity Ownership. Orlowski:Acetylon: Membership on an entity's Board of Directors or advisory committees; Bristol-Myers Squibb: Consultancy, Research Funding; Forma Therapeutics: Consultancy; Celgene: Consultancy, Research Funding; Millennium Pharmaceuticals: Consultancy, Research Funding; Array BioPharma: Consultancy, Research Funding; Onyx Pharmaceuticals: Consultancy, Research Funding; Janssen Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees; Genentech: Consultancy; BioTheryX, Inc.: Membership on an entity's Board of Directors or advisory committees; Spectrum Pharmaceuticals: Research Funding.

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SL-401, a Novel IL-3Rα/CD123-Directed Agent Targets Stem-like Cells in Multiple Myeloma

Blood ◽

10.1182/blood.v128.22.4463.4463 ◽

2016 ◽

Vol 128 (22) ◽

pp. 4463-4463 ◽

Cited By ~ 1

Author(s):

Arghya Ray ◽

Yan Song ◽

Deepika Sharma Das ◽

Vincent Macri ◽

Janice Chen ◽

...

Keyword(s):

Multiple Myeloma ◽

Stem Cell ◽

Board Of Directors ◽

Cell Lines ◽

Proteasome Inhibitor ◽

Drug Resistant ◽

Employment Equity ◽

Advisory Committees ◽

Equity Ownership ◽

Rpmi 8226

Abstract Introduction Multiple myeloma (MM) remains incurable despite novel therapies, highlighting the need for further identification of factors mediating disease progression and resistance. One such factor is the development of a drug-resistant stem cell-like subpopulation. Previous studies have shown that MM side population cells (MM-SPs) exhibit stem-cell like features and contribute to relapse of MM. Recent research efforts, which have focused the biology of MM stem-like cells in order to derive specific therapy, have shown that stem-cell transcription factor Oct-4 is linked to stemness and chemoresistance. Here we examined the effect of enforced expression of Oct4 in MM cells and MM-SPs on the development of stem cell-like characteristics and drug-resistance in MM. These studies allow us to establish stable MM cell lines with characteristic stem-cell like features, which in turn facilitate screening of novel agents that effectively target this cell population in MM. Methods MM-SPs were isolated from RPMI-8226 cells by flow-cytometry based Hoechst 33342 staining. RPMI-8226 and RPMI-8226-SP cells were transfected with a phOct4-GFP construct (Gerrard et al., Stem Cell 2005, 23:124-133), and selected with G418 (0.5 mg/ml) to derive stable RPMI-8226-Oct4 and RPMI-8226-SP-Oct4 cell lines. Oct-4 expression was confirmed using FACS. Cell viability was analyzed by WST assays. SL-401 is a targeted therapy directed to IL-3Rα/CD123, comprised of recombinant human IL-3 fused to truncated diphtheria toxin. Drug and reagent source: SL-401 was obtained from Stemline Therapeutics; Bortezomib and flow antibodies were purchased from Selleck Chemicals and BD Biosciences, respectively. Statistical significance was derived using GraphPad Prism. Results 1) RPMI-8226 and RPMI-8226-Oct4 cells were analyzed for the expression of surface markers associated with stem cells (CD123/IL-3Rα, CD133 and CD27) by multicolor flow analysis. Oct-4 transfection does not affect the overall CD123 expression in RPMI-8226 cells, as the % MFI-CD123hi in RPMI-8226 versus RPMI-8226-Oct4 remains unchanged. However, the stable selection makes RPMI-8226-Oct4 more clonal in nature (%CD123hi : RPMI8226; 14.9% vs RPMI-8226-Oct4; 60%). 2) A significant increase in the frequency of CD133+ve cells was observed in RPMI-8226-SP-Oct4-tranfected cells versus either RPMI-8226-SP cells or RPMI-8226-Oct-4 cells [RPMI-8226-SP: 6.3%; RPMI-8226-Oct4: 27.8%; RPMI-8226-SP-Oct4: 40%; p< 0.05]. 3) Analysis of CD27 surface marker showed highest expression in RPMI-8226-SP-Oct4 cells compared to RPMI-8226-Oct4, RPMI-8226-SP, or RPMI-8226 cells (% MFI: RPMI-8226-SP-Oct4 > RPMI-8226-Oct4 > RPMI-8226-SP > RPMI-8226 cells). 4) Treatment of RPMI-8226 and RPMI-8226-Oct4 cells with proteasome inhibitor bortezomib decreased the viability of RPMI-8226 cells; in contrast, bortezomib did not significantly alter the viablity of RPMI-8226-Oct4 cells [% Viability after bortezomib: RPMI-8226; <50% versus RPMI-8226-Oct4; 95%]. Finally, 5) SL-401 significantly decreased the viability of RPMI-8226-Oct4 cells [IC50: RPMI-8226-Oct4 cells: 75 pM; RPMI-8226-SP cells: 350 pM; RPMI-8226 cells: 1367 pM]. We have previously shown anti-MM activity of SL-401 by an additional mechanism of targeting IL-3Rα-expressing plasmacytoid dendritic cells (pDCs) localized in the tumor microenvironment and blocking pDC-induced MM cell growth. Conclusions Our data show that stem-like cells in MM are relatively resistant to proteasome inhibitor therapy. Importantly, a novel agent SL-401 effectively targets these cells. Oct4-driven stable RPMI-8226 MM cell line serves as a novel tool to screen and develop newer agents targeting stem-like cells in MM. Overall, we show the ability of SL-401 to target a drug-resistant stem-like cell population in MM, and provide an additional rationale for clinical evaluation of SL-401 to improve patient outcome. A clinical trial of SL-401 in MM is currently ongoing (NCT02661022). Disclosures Macri: Stemline Therapeutics, Inc.: Employment. Chen:Stemline Therapeutics, Inc.: Employment, Equity Ownership. Richardson:Jazz Pharmaceuticals: Consultancy, Membership on an entity's Board of Directors or advisory committees. Brooks:Stemline Therapeutics, Inc.: Employment, Equity Ownership, Patents & Royalties. Chauhan:Oncopeptide AB: Consultancy; Epicent Rx: Consultancy; C4 Therapeutics: Equity Ownership; Stemline Therapeutics, Inc.: Consultancy. Anderson:Celgene: Membership on an entity's Board of Directors or advisory committees; Sonofi Aventis: Membership on an entity's Board of Directors or advisory committees; Acetylon: Other: Scientific Founder; Oncopep: Other: Scientific Founder; Gilead: Membership on an entity's Board of Directors or advisory committees; Onyx: Membership on an entity's Board of Directors or advisory committees.

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Overcoming CD28-Mediated Multi-Drug Resistance With a Novel PIM2 Inhibitor

Blood ◽

10.1182/blood.v122.21.1931.1931 ◽

2013 ◽

Vol 122 (21) ◽

pp. 1931-1931

Author(s):

Carmen M. Baldino ◽

Jayakumar R. Nair ◽

Justin Caserta ◽

Megan Murray ◽

Stephane Dumas ◽

...

Keyword(s):

Multiple Myeloma ◽

Drug Resistance ◽

Board Of Directors ◽

Cell Lines ◽

Tumor Xenograft ◽

Multi Drug Resistance ◽

Employment Equity ◽

Advisory Committees ◽

Equity Ownership

Abstract Drug resistance in multiple myeloma (MM) is the major cause of treatment failure and is significantly mediated by pro-survival interactions with bone marrow microenvironment. A key myeloma receptor involved in this interaction is CD28, which has been largely characterized as the prototypic T cell costimulatory receptor. However, CD28 expression on myeloma cells is significantly correlated with disease progression, worse prognosis, and is significantly higher in the poor prognosis t(14;16) MAF subgroup. We now report that CD28 signaling mediates significant drug resistance and protects MM against death from multiple chemotherapeutics with different mechanisms of action – including dexamethasone, arsenic trioxide, melphalan or bortezomib. Inhibition of specific signaling (PI3K or Akt) or targets (Foxo3A or Bim) downstream of CD28 activation abrogates this protection. Unexpectedly, we found evidence that the PIM2 kinase (which is largely uncharacterized in MM but is also significantly overexpressed in the MAF subgroup) may be a previously unreported component of the CD28 pro-MM survival pathway. The novel small molecule PIM2 inhibitor JP_11646 (IC50 0.5 nM) abrogates CD28-mediated protection against apoptosis in MM cell lines in vitro, which we have not previously seen for any chemotherapeutic tested. In addition, blockade of CD28 activation sensitized MM cells significantly to JP_11646-induced death. Altogether, these data suggested that PIM2 inhibitors can overcome a major mechanism of multi drug resistance in MM. Jasco’s novel and selective pan-PIM inhibitor (JP_11646) has demonstrated biochemical IC50s of 24, 0.5 and 1 nM for PIM1, PIM2 and PIM3 respectively. The PIM mechanism of action has been confirmed through cell based transphosphorylation assays, where JP_11646 decreased PIM dependent phoshphorylation of the proapoptotic protein BAD at nM levels. JP_11646 increases apoptosis and decreases cell viability in multiple myeloma cell lines with the MAF translocations (<100 nM). JP_11646 is orally bioavailable and has demonstrated in vivo efficacy, inhibiting tumor growth by >80% in a MM1.S tumor xenograft study. These data provide solid rationale for further development of JP_11646 as a targeted therapy in MM, and specifically for patients exhibiting the MAF translocation. Disclosures: Baldino: Jasco pharmaceuticals: Employment, Equity Ownership, Founder and President Other, Membership on an entity’s Board of Directors or advisory committees. Caserta:Jasco Pharmaceuticals: Co-Founder Other, Employment, Equity Ownership, Membership on an entity’s Board of Directors or advisory committees. Dumas:Jasco Pharmaceuticals: Employment. Flanders:Jasco Pharmaceuticals: Employment. Lee:Jasco Pharmaceuticals: Research Funding.

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Carfilzomib, Lenalidomide, and Dexamethasone In Newly Diagnosed Multiple Myeloma: Initial Results of Phase I/II MMRC Trial

Blood ◽

10.1182/blood.v116.21.862.862 ◽

2010 ◽

Vol 116 (21) ◽

pp. 862-862 ◽

Cited By ~ 5

Author(s):

Andrzej J Jakubowiak ◽

Dominik Dytfeld ◽

Sundar Jagannath ◽

David H. Vesole ◽

Tara B. Anderson ◽

...

Keyword(s):

Multiple Myeloma ◽

Phase I ◽

Board Of Directors ◽

Newly Diagnosed ◽

Employment Equity ◽

Advisory Committees ◽

Level 3 ◽

Equity Ownership ◽

Level 1 ◽

Level 2

Abstract Abstract 862 Background: Carfilzomib (Cfz) is a novel, irreversible proteasome inhibitor that has demonstrated promising single-agent activity and favorable toxicity profile, including very low rates of peripheral neuropathy and neutropenia in relapsed/refractory multiple myeloma (MM). Combining Cfz with Lenalidomide (Revlimid®, Len), and Dexamethasone (Dex) into CRd shows an additive anti-MM effect in preclinical studies and lack of overlapping toxicity allowing for the use of these agents at full doses and for extended duration of time in relapsed/refractory MM (Niesvizky et al, ASH, 2009). This Phase I/II study was designed to determine the maximum tolerated dose (MTD) of CRd and to assess safety and evaluate efficacy of this combination in newly diagnosed MM. Methods: In Phase I, dose escalation follows the TITE-CRM algorithm, with Cfz as the only escalating agent starting at 20 mg/m2 (level 1), maximal planned dose 27 mg/m2 (level 2), and 15 mg/m2, if needed (level -1), given IV on days 1, 2, 8, 9, 15, 16 in 28-day cycles. Len is used at 25 mg PO (days 1–21), and Dex at 40/20 mg PO weekly (cycles 1–4/5-8) for all dose levels. Based on toxicity assessment, the study was amended to add dose level 3 with Cfz at 36 mg/m2 and the number of pts in the Phase I was increased to 35. A total of 36 pts are planned to be treated at the MTD in Phase I/II. Pts who achieve ≥ PR can proceed to stem cell collection (SCC) and autologous stem cell transplant (ASCT) after ≥ 4 cycles, although per protocol design, ASCT candidates are offered to continue CRd treatment after SCC. After completion of 8 cycles, pts receive 28-day maintenance cycles with Cfz (days 1, 2 15, 16), Len days 1–21, and Dex weekly at the doses tolerated at the end of 8 cycles. Responses are assessed by IMWG criteria with the addition of nCR. Results: The study has enrolled 24 pts to date, 4 pts at level 1 (Cfz 20), 14 at level 2 (Cfz 27) and at 6 at level 3 (Cfz 36). Toxicity data are available for 21 pts, of which 19 have completed at least the first cycle required for DLT assessment; 2 pts were removed during the first cycle for events unrelated to study therapy (1 at level 1 and 1 at level 2), and 3 are currently within their first cycle of treatment. There was a single DLT event at dose level 2 (non-febrile neutropenia requiring dose reduction of Len per protocol) and the MTD has not been reached. Hematologic toxicities were reversible and included Grade (G) 3/4 neutropenia in 3 pts, G3/4 thrombocytopenia in 3, and G3 anemia in 2. There have been additional G3 non-hematologic AEs including 1 case of DVT while on ASA prophylaxis, 1 fatigue, 1 mood alteration, and 5 glucose elevations; the last 2 AEs were related to Dex. There was no emergence of peripheral neuropathy (PN), even after prolonged treatment, except in 2 pts who developed G1 sensory PN. Twenty-three pts continue on treatment, most (20 pts) without need for any dose modifications. After a median of 4 (range 1–8) months of treatment, preliminary response rates by IMWG in 19 evaluable pts who completed at least 1 cycle are: 100% ≥ PR, 63% ≥ VGPR, 37% CR/nCR, including 3 pts with sCR. Responses were rapid with 17 of 19 pts achieving PR after 1 cycle and improving responses with continuing therapy in all pts. To date, 7 pts proceeded to SCC using growth factors only, with a median 6.3 × 106 CD34+ cells/kg collected (range 4.1–8.2), after a median of 4 cycles of CRd (range 4–8); all resumed CRd treatment after SCC. After a median of 4 months of follow-up, none of evaluable pts progressed and all are alive. Conclusion: CRd is well tolerated and highly active in newly diagnosed MM with ≥ PR of 100%, including 63% ≥VGPR and 37% CR/nCR. Accrual is ongoing, with updated toxicity and efficacy data to be presented at the meeting. The results of this study represent the first report of treatment of frontline myeloma with Cfz to date, and provide additional support to recently initiated Phase 3 trial of CRd vs. Rd in relapsed MM. Disclosures: Jakubowiak: Bristol-Myers Squibb: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Exelixis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Centocor OrthoBiotech: Consultancy, Honoraria, Speakers Bureau; Celgene: Consultancy, Honoraria, Speakers Bureau; Millennium: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees. Off Label Use: Lenalidomide for newly diagnosed multiple myeloma. Jagannath:Millennium: Honoraria; OrthoBiotech (Canada): Honoraria; Celgene: Honoraria; Merck: Honoraria; Onyx Pharmaceuticals: Honoraria; Proteolix, Inc: Honoraria; Imedex: Speakers Bureau; Medicom World Wide: Speakers Bureau; Optum Health Education: Speakers Bureau; PER Group: Speakers Bureau. Vesole:Celgene: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Anderson:Millennium: Honoraria, Speakers Bureau; Celgene: Honoraria, Speakers Bureau. Stockerl-Goldstein:Celgene: Speakers Bureau; Millennium: Speakers Bureau. Barrickman:Celgene: Employment, Equity Ownership. Kauffman:Onyx Pharmaceuticals: Employment, Equity Ownership. Vij:Proteolix: Consultancy; Celgene: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Onyx: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau.

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Absence Of Mutation In Cereblon (CRBN) and DNA Damage Binding Protein 1 (DDB1) Genes In Myeloma Cells and Patients and Its Clinical Significance

Blood ◽

10.1182/blood.v122.21.3139.3139 ◽

2013 ◽

Vol 122 (21) ◽

pp. 3139-3139

Author(s):

Anjan Thakurta ◽

Anita K Gandhi ◽

Michelle Waldman ◽

Chad C. Bjorklund ◽

Suzanne Lentzsch ◽

...

Keyword(s):

Board Of Directors ◽

Cell Lines ◽

Research Funding ◽

Heterozygous Mutation ◽

Employment Equity ◽

Advisory Committees ◽

Single Nucleotide ◽

Truncating Mutation ◽

Equity Ownership

Abstract Background CRBN, a target of thalidomide and IMiDs® immunomodulatory agents lenalidomide (LEN) and pomalidomide (POM), is a component of the E3 ubiquitin cullin 4 ring ligase (CRL4) complex that also includes DDB1, Roc1, and Cul4. Two CRBN mutations have been reported in multiple myeloma (MM) patients: truncating mutation (Q99) and point mutation (R283K). One copy of the CRBN gene was shown to be deleted in the MM1S and MM1S.R cell lines. No DDB1 mutation has been described previously. Results We investigated the incidence of CRBN and DDB1 mutations by next-generation sequencing in 20 MM cell lines and MM subjects. Of 90 MM patients, 24 were newly diagnosed and 66 were relapsed and refractory of which 36 patients were LEN resistant. Out of the cell lines tested, 1 heterozygous CRBN mutation (D249Y) was found in the LEN-resistant ANBL6R cells, which is located in the putative DDB1 binding domain, and 2 single silent mutations were identified in the KMS-12-BM (rs17027638) and OPM-2 cells. One DDB1 heterozygous mutation (E303D) was identified in ANBL6 cells. In the cohort of patients assessed, no CRBN mutation was detected; however, 5 single nucleotide variations (SNV) were identified. Three of the 5 SNVs were at position 735 (Y245Y) and 1 each at position 219 (H73H) and 939 (C313C), respectively. The first 2 SNVs (rs17027638 and rs1045309) are described but not the last. We found a single SNV (P51P; rs2230356) in DDB1 gene the patient samples. Conclusion Mutations within the coding sequences of CRBN and DDB1 are rare in MM patients and cell lines. Most intrinsically LEN-resistant cells and cell lines made resistant to LEN or POM do not have CRBN or DDB1 mutations, suggesting the potential role of other sources, such as genetic or epigenetic pathways in developing resistance to IMiD drug–based therapy. Disclosures: Thakurta: Celgene: Employment, Equity Ownership. Gandhi:Celgene: Employment, Equity Ownership. Waldman:Celgene: Employment, Equity Ownership. Bjorklund:Celgene: Employment, Equity Ownership. Lentzsch:Celgene: Research Funding. Schey:Celgene: Consultancy, Honoraria, Membership on an entity’s Board of Directors or advisory committees, Speakers Bureau; NAPP: Consultancy, Honoraria, Membership on an entity’s Board of Directors or advisory committees, Speakers Bureau; BMS: Consultancy, Honoraria, Membership on an entity’s Board of Directors or advisory committees, Speakers Bureau. Orlowski:Bristol-Myers Squibb: Honoraria, Membership on an entity’s Board of Directors or advisory committees, Research Funding; Celgene: Honoraria, Membership on an entity’s Board of Directors or advisory committees, Research Funding; Millennium: Honoraria, Membership on an entity’s Board of Directors or advisory committees, Research Funding; Onyx: Honoraria, Membership on an entity’s Board of Directors or advisory committees, Research Funding; Resverlogix: Research Funding; Array: Honoraria, Membership on an entity’s Board of Directors or advisory committees; Genentech: Honoraria, Membership on an entity’s Board of Directors or advisory committees; Merck: Membership on an entity’s Board of Directors or advisory committees. Madan:Covance Genomics Lab: Employment. Ning:Celgene: Employment, Equity Ownership. Mendy:Celgene: Employment, Equity Ownership. Lopez-Girona:Celgene: Employment, Equity Ownership. Schafer:Celgene: Employment, Equity Ownership. Avet-Loiseau:Celgene: Research Funding. Chopra:Celgene: Employment, Equity Ownership.

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Novel Inhibitors Of CRM1/XPO1 Nuclear Exporter Exhibit Striking Activity Against AML “primagrafts,” Including AML Leukemia Initiating Cells, While Sparing Normal Hematopoietic Cells

Blood ◽

10.1182/blood.v122.21.3932.3932 ◽

2013 ◽

Vol 122 (21) ◽

pp. 3932-3932

Author(s):

Julia Etchin ◽

Bonnie Thi Le ◽

Alex Kentsis ◽

Richard M. Stone ◽

Dilara McCauley ◽

...

Keyword(s):

Board Of Directors ◽

Cell Lines ◽

Nuclear Export ◽

Hematopoietic Cells ◽

Complex Karyotype ◽

Employment Equity ◽

Advisory Committees ◽

Hematopoietic Stem ◽

Nsg Mice ◽

Equity Ownership

Abstract Current treatments for acute myeloid leukemia (AML) often fail to induce long-term remissions and are also toxic to normal tissues, prompting the need to develop new targeted therapies. One attractive cellular pathway with therapeutic potential is nuclear export, which is mediated in part by nuclear exporter CRM1/XPO1. XPO1 mediates the transport of ∼220 proteins and several mRNAs and is the sole nuclear exporter of the major tumor suppressor and growth regulatory proteins p53, p73, FOXO, IkB/NF-kB, Rb, p21, and NPM. Our findings demonstrate that novel irreversible inhibitors of XPO1, termed Selective Inhibitors of Nuclear Export, or SINE, induce rapid apoptosis in 12 AML and 14 T-ALL cell lines with IC50s of 15-474 nM. In the SINE-sensitive cell lines, BCL2 overexpression suppresses SINE-induced apoptosis, indicating its intrinsic pathway mediation. Oral administration of clinical XPO1 inhibitor, Selinexor (KPT-330), at 15 or 25 mg/kg, induced remarkable growth suppression in MV4-11 human AML cells and MOLT-4 human T-ALL cells engrafted in immunodeficient NSG mice with negligible toxicity to normal mouse hematopoietic cells after 35 days of treatment. Bone marrow biopsies of selinexor - treated mice were remarkable in that they showed normal hematopoietic cell morphology and cellularity after 35 days of treatment. Significant survival benefit was observed in mice treated with selinexor, compared to vehicle-treated mice. Selinexor is now in Phase 1 clinical trial in patients with AML and other hematological malignancies (NCT01607892). Recently, we have established primagraft models of AML, using primary leukemia blasts isolated from AML patients at diagnosis transplanted into immunocompromised NSG mice. We demonstrated that selinexor exhibits striking anti-leukemic activity against different subtypes of primary AML, including AML-M4; FLT3-ITD and complex karyotype subtypes of the disease. To determine whether selinexor targets leukemia-initiating cells (LICs) of primary AML, we re-transplanted serial dilutions of human CD45+ cells isolated from leukemic mice treated with either vehicle or selinexor. The preliminary results of our re-population assays indicate that selinexor greatly diminished LIC frequency in AML-M4; FLT3-ITD AML (∼6 fold) and complex karyotype disease (∼100 fold). These findings demonstrate that selinexor may represent a novel targeted therapy for the treatment of AML, which spares normal hematopoietic stem and progenitor cells. Disclosures: McCauley: Karyopharm Therapeutics Inc.: Employment, Equity Ownership, Patents & Royalties. Kauffman:Karyopharm Therapeutics Inc.: Employment, Equity Ownership, Membership on an entity’s Board of Directors or advisory committees, Patents & Royalties. Shacham:Karyopharm Therapeutics Inc.: Employment, Equity Ownership, Membership on an entity’s Board of Directors or advisory committees, Patents & Royalties.

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Targeted MEK Inhibition in Patients with Previously Treated Multiple Myeloma

Blood ◽

10.1182/blood.v124.21.4775.4775 ◽

2014 ◽

Vol 124 (21) ◽

pp. 4775-4775 ◽

Cited By ~ 4

Author(s):

Christoph Heuck ◽

Yogesh Jethava ◽

Rashid Z Khan ◽

Scott Miller ◽

Alan Mitchell ◽

...

Keyword(s):

Multiple Myeloma ◽

Board Of Directors ◽

Research Funding ◽

Mapk Pathway ◽

Objective Response ◽

Genomic Profiling ◽

Employment Equity ◽

Advisory Committees ◽

Comprehensive Genomic Profiling ◽

Equity Ownership

Abstract Background: Diagnostic and therapeutic advances have significantly improved the outcomes for multiple myeloma (MM) patients. However, pts who are refractory to or relapse after therapy with immune modulatory drugs and proteasome inhibitors remain a therapeutic challenge. Comprehensive genomic profiling via clinical next generation sequencing (NGS)-based assays studies of MM cases have revealed multiple targetable mutations that were previously unexploited in MM. Methods: Between June 2013 and May 2014 we performed genomic profiling of 351 patients who had progressed after initial therapy to assist physicians in therapy planning. Comprehensive genomic profiling was performed using the FoundationOne¨ or FoundationOne Heme¨ assays. FoundationOne assays 374 cancer-related and 24 frequently rearranged genes via DNA-seq, and FoundationOneHeme assays 405 cancer-related and 31 frequently rearranged genes via DNA-seq as well as 265 frequently rearranged genes by RNA-seq. All samples were sequenced in a CLIA-certified CAP-accredited laboratory to an average depth >500x . Patients with activating alterations of KRAS, NRAS or BRAF were considered for therapy with the targeted agent trametinib (TMTB) as were patients who had a gene expression signature suggesting activation of the MAPK pathway. Retrospective review of this case series was approved by the UAMS institutional review board. Results: We identified 63 patients who underwent treatment with Trametinib. 60 were treated based on activating mutations of KRAS, NRAS or BRAF and 3 were treated based on a GEP signature. The median age was 65 and patients had a median of 5 lines of prior therapy (range 1-20). 38 of 63 patients had prior treatment with Total Therapy. 43 underwent salvage with chemotherapy prior to initiation of TMTB, 15 had salvage transplants, 33 patients were exposed to novel agents (Pomalidomide, Carfilzomib) and 33 had Metronomic therapy before TMTB. 25% of patients were ISS stage 3 and 37% had GEP70 defined high risk. 13 had PET defined extra medullary disease (EMD). 41 patients were administered TMTB monotherapy and 22 received TMTB treatment in combination with other agents. In general the treatment was well tolerated. 10 patients discontinued therapy because of toxicities, 29 discontinued because of disease progression or death. None of the deaths were attributed to TMTB, Best treatment responses were SD in 30, PR in 8, VGPR in 2 and CR in 3 of the 63 pts. For 25 patients with evaluable PET data, treatment resulted in complete resolution of FDG avid lesions in 9 patients and a better than 50% reduction in 15 (Figure 1). We will present updated data on clinical responses as well as toxicities. Conclusions: Treatment with targeted therapy guided by prospective comprehensive genomic profiling across all classes of genomic alterations in this heavily pretreated population of MM patients resulted in an unexpectedly high objective response rate. Observation of CR with TMTB monotherapy further supports continued investigation of this individualized approach to MM management. Disclosures Van Laar: Signal Genetics: Employment, Equity Ownership. Ali:Foundation Medicine, Inc.: Employment, Equity Ownership. Miller:Foundation Medicine, Inc: Employment. Zangari:Norvartis: Membership on an entity's Board of Directors or advisory committees; Onyx: Research Funding; Millennium: Research Funding. van Rhee:Millenium: Speakers Bureau; Sanofi: Speakers Bureau; Celgene: Speakers Bureau; Janssen: Speakers Bureau. Morgan:Celgene Corp: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees; Janssen: Membership on an entity's Board of Directors or advisory committees; Myeloma UK: Membership on an entity's Board of Directors or advisory committees; International Myeloma Foundation: Membership on an entity's Board of Directors or advisory committees; The Binding Site: Membership on an entity's Board of Directors or advisory committees; MMRF: Membership on an entity's Board of Directors or advisory committees.

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Final Analysis of Overall Survival from the Phase 3 Panorama 1 Trial of Panobinostat Plus Bortezomib and Dexamethasone Versus Placebo Plus Bortezomib and Dexamethasone in Patients with Relapsed or Relapsed and Refractory Multiple Myeloma

Blood ◽

10.1182/blood.v126.23.3026.3026 ◽

2015 ◽

Vol 126 (23) ◽

pp. 3026-3026 ◽

Cited By ~ 5

Author(s):

Jesús F. San-Miguel ◽

Vania T.M. Hungria ◽

Sung-Soo Yoon ◽

Meral Beksac ◽

Meletios A. Dimopoulos ◽

...

Keyword(s):

Multiple Myeloma ◽

Overall Survival ◽

Board Of Directors ◽

Research Funding ◽

Final Analysis ◽

Employment Equity ◽

Phase 3 ◽

Advisory Committees ◽

Equity Ownership ◽

Study Therapy

Abstract Introduction: Panobinostat is a potent pan-deacetylase inhibitor (pan-DACi) that targets key aberrations in multiple myeloma (MM) cell biology, including epigenetics and protein metabolism. In the phase 3 clinical trial PANORAMA 1, panobinostat in combination with bortezomib and dexamethasone (PAN-BTZ-Dex) led to a statistically significant and clinically relevant increase in progression-free survival of approximately 4 months compared with that with placebo plus bortezomib and dexamethasone (Pbo-BTZ-Dex). Further analyses of patient outcomes by prior treatment demonstrated that the magnitude of PFS benefit was greatest among patients who received at least 2 prior regimens, including bortezomib and an immunomodulatory drug (IMiD; PAN-BTZ-Dex [n = 73]: 12.5 months [95% CI, 7.3-14.0 months]; Pbo-BTZ-Dex [n = 74]: 4.7 months (95% CI, 3.7-6.1 mo; HR 0.47 [95% CI, 0.32-0.72]). These data supported the regulatory approvals of PAN-BTZ-Dex for the treatment of patients with multiple myeloma who received at least 2 prior regimens, including bortezomib and an IMiD. Here we present the final analysis of overall survival (OS) for the entire patient population and among patients who received at least 2 prior regimens, including bortezomib and an IMiD. Methods: The study design for the PANORAMA 1 trial was described previously (San-Miguel. Lancet Oncol. 2014;15:1195-206). The key secondary endpoint was OS. As of June 29, 2015, the 415 events required to conduct the final analysis of OS had been observed. Kaplan-Meier estimation was utilized for OS analyses for the entire population (N = 768), the pre-specified subgroup of patients who received prior bortezomib and IMiD (n = 193), and patients who received at least 2 prior regimens including bortezomib and an IMiD (n = 147). Results: The median OS of patients who received PAN-BTZ-Dex in the overall population was 40.3 months (95% CI, 35.0-44.8 months) vs 35.8 months (95% CI, 29.0-40.6 months) for the Pbo-BTZ-Dex arm with HR 0.94 [95% CI, 0.78-1.14], P = .5435 (Fig 1A). The percentage of patients in each arm who received post-study therapy was 37.7% in the PAN-BTZ-Dex arm and 48.8% in the Pbo-BTZ-Dex arm. The median OS of patients who received at least 2 prior lines, including bortezomib and an IMiD, was 25.5 months (95% CI, 19.6-34.3 months) in the PAN-BTZ-Dex arm vs 19.5 months (95% CI, 14.1-32.5 months) in the Pbo-BTZ-Dex arm (Fig. 1B). The proportion of patients in this subgroup who received post-study therapy was 35.6% in the PAN-BTZ-Dex arm and 66.2% in the Pbo-BTZ-Dex arm. Conclusion: For the overall PANORAMA 1 study population, patients in the PAN-BTZ-Dex arm demonstrated an increase in median OS of 4.5 months vs patients in the Pbo-BTZ-Dex arm, but this result was not statistically significant (P = .5435). Median OS was also slightly longer for the PAN-BTZ-Dex arm among the more heavily pretreated subgroup of patients who received at least 2 prior regimens, including bortezomib and an IMiD. A higher percentage of patients on the Pbo-BTZ-Dex arm received post-study therapy vs the PAN-BTZ-Dex arm, which may have confounded the OS results. In summary, PAN-BTZ-Dex demonstrates statistically significant increases in PFS vs Pbo-BTZ-Dex in patients with relapsed or relapsed and refractory MM; however, this did not translate to a statistically significant increase in OS. Future trials will plan to focus on further optimization of dose and schedule of panobinostat and bortezomib to improve outcome, as well as novel combinations with other agents, including IMiDs and next-generation proteasome inhibitors. Figure 2. Figure 2. Disclosures Beksac: Bristol-Myers Squibb: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Celgene: Consultancy, Speakers Bureau; Amgen: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Takeda: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Janssen-Cilag: Consultancy, Speakers Bureau. Dimopoulos:Janssen: Honoraria; Janssen-Cilag: Honoraria; Onyx: Honoraria; Amgen: Honoraria; Genesis: Honoraria; Celgene: Honoraria; Novartis: Honoraria. Jedrzejczak:Onconova: Membership on an entity's Board of Directors or advisory committees; Roche: Membership on an entity's Board of Directors or advisory committees; Pfizer: Membership on an entity's Board of Directors or advisory committees; Janssen: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees. Siritanaratkul:Pfizer: Research Funding; Roche: Research Funding; Novartis: Research Funding; Janssen-Cilag: Research Funding. Schlossman:Millennium: Consultancy. Hou:Novartis: Membership on an entity's Board of Directors or advisory committees. Moreau:Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees; Bristol-Myers Squibb: Honoraria, Membership on an entity's Board of Directors or advisory committees; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees; Janssen-Cilag: Honoraria, Membership on an entity's Board of Directors or advisory committees; Millennium: Honoraria, Membership on an entity's Board of Directors or advisory committees. Lonial:Bristol-Myers Squibb: Consultancy, Research Funding; Millennium: Consultancy, Research Funding; Janssen: Consultancy, Research Funding; Novartis: Consultancy, Research Funding; Onyx: Consultancy, Research Funding; Celgene: Consultancy, Research Funding. Sopala:Novartis Pharma: Employment, Equity Ownership. Bengoudifa:Novartis: Employment. Corrado:Novartis: Employment, Equity Ownership. Richardson:Bristol-Myers Squibb: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees; Millennium Takeda: Membership on an entity's Board of Directors or advisory committees; Johnson & Johnson: Membership on an entity's Board of Directors or advisory committees.

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Dysregulated Nucleotide Excision Repair (NER) Is a New Target in Multiple Myeloma

Blood ◽

10.1182/blood.v126.23.4187.4187 ◽

2015 ◽

Vol 126 (23) ◽

pp. 4187-4187

Author(s):

Raphaël Szalat ◽

Mehmet Kemal Samur ◽

Alice Cleynen ◽

Anne Calkins ◽

Matija Dreze ◽

...

Keyword(s):

Multiple Myeloma ◽

Board Of Directors ◽

Cell Lines ◽

Drug Sensitivity ◽

Excision Repair ◽

Alkylating Agents ◽

Advisory Committees ◽

Rapid Repair ◽

Nucleotide Excision ◽

Equity Ownership

Abstract Nucleotide excision repair (NER) is involved in the removal of bulky adducts and DNA crosslinks induced by various genotoxins including alkylating agents. In cancer, somatic mutations, genes' up-regulation, and epigenetic silencing of NER may lead to abnormal DNA damage responses. Little is known about the role of NER in biology of multiple myeloma (MM), a heterogeneous disease characterized by genomic instability which is often treated by alkylating agents. In our genome sequencing data we did not observe recurrent mutation in NER although non silent mutations affected 13 genes involved in NER in 20out of 272 distinct patients. Using a functional assay based on the purified DNA-Damage Binding protein 2 (DDB2) proteo-probe complex that allows monitoring of photoproducts removal after UV irradiation, we observed NER variability in MM cell lines (MMCL) allowing to separate the cell lines in 2 groups according to their ability to repair: namely rapid (repair>90% after 2 hours) versus slow (repair < 85% after 2 hours). The separation in two NER phenotypes did not correlate with P53 loss of function or any cytogenetic event with the exception of t (4;14) translocation which was associated with the group showing a repair rate > 90%. Interestingly, the LR5 melphalan resistant cell line harbored a rapid repair phenotype as compared to the parental RPMI-8226 cell line which exhibited a slow repair. We evaluated melphalan sensitivity in relationship to NER activity in rapid and slow MMCL and observed that MMCL with slow NER were more sensitive to melphalan. We next evaluated whether inhibiting NER modified drug sensitivity. We utilized spironolactone which is known to inhibit NER. With the DDB2 proteo-probe assay, we confirmed the ability of spironolactone to inhibit NER in MMCL by degrading the Xeroderma Pigmentosum group B (XPB) protein. Combination of melphalan with NER inhibition in the 20 MMCL induced a significant increase in melphalan sensitivity in MMCL (increase from 15 to 79%). We have also confirmed similar NER activity in CD138 positive patient plasma cells. We then developed a gene expression signature using rapid and slow NER cell lines. In a multivariate analysis, the rapid NER signature was significantly associated with low survival in the IFM 2005-01 trial dataset that included 170 patients treated with high-dose melphalan. In conclusion, we have observed that NER affects MM cells and plays a significant role in drug sensitivity; we have also shown that NER can be targeted to increase melphalan sensitivity and potentially improve patient outcome. Disclosures Avet-Loiseau: onyx: Membership on an entity's Board of Directors or advisory committees; millenium: Membership on an entity's Board of Directors or advisory committees; jansen: Membership on an entity's Board of Directors or advisory committees; celgene: Membership on an entity's Board of Directors or advisory committees; jansen: Membership on an entity's Board of Directors or advisory committees; onyx: Membership on an entity's Board of Directors or advisory committees; BMS: Membership on an entity's Board of Directors or advisory committees; millenium: Membership on an entity's Board of Directors or advisory committees; BMS: Membership on an entity's Board of Directors or advisory committees. Anderson:Celgene: Consultancy; Millennium: Consultancy; BMS: Consultancy; Gilead: Consultancy; Oncopep: Equity Ownership; Acetylon: Equity Ownership.

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