ALBERT

Description: Introduction: Histone deacetylase inhibitors (HDACis) have demonstrated clinical efficacy in multiple myeloma, particularly in combination with proteasome inhibitors. CHR-3996 is a class 1 selective HDACi with potent anti-myeloma activity in vitro. Aminopeptidase inhibitors act downstream of the proteasome and prevent breakdown of proteasome generated peptides into amino acids. Synergistic cytotoxicity was observed in vitro when CHR-3996 was combined with the aminopeptidase inhibitor, tosedostat through rapid activation of NFkB followed by increased expression of the repressors IκBα, A20, CYLD, BIRC3. The MUK-three study was designed to translate these pre-clinical findings into a phase 1 clinical trial. This dose escalation study aimed to determine the maximum tolerated dose, safety and preliminary activity of CHR-3996 administered in combination with Tosedostat for patients with relapsed, refractory MM. Here we present the final study results. Methods: MUK-three was an open label multi-centre UK Phase I/IIa trial for patients with relapsed and relapsed/ refractory myeloma who had failed conventional treatments. Patients were permitted to meet the haematological entry criteria using growth factor and/or blood product support. During dose escalation subjects received CHR-3996 (20-40mg days1-28) and Tosedostat (0-60mg days 1-28) (Table 1) every 28 day cycle until disease progression or withdrawal. Dose limiting toxicities (DLTs) were evaluated during cycle 1 and dose escalation followed the 3+3 design. Responses were assessed using modified IMWG uniform response criteria, with the primary endpoint for the expansion phase of stable disease (SD) rate after 4 cycles of therapy. Toxicity was graded by CTCAE V4.0. Results: The trial was open to recruitment from July 2012 to December 2015. 20 patients were treated during dose escalation, including 8 at the recommended dose (RD) and 12 at dose levels (DL) 1-3. Only 1 DLT was observed at DL3 (grade 4 thrombocytopenia); however, this DL was deemed not tolerable due to the high incidence of low grade gastrointestinal toxicities. Hence the RD was determined as DL3b, CHR-3996 20mg and Tosedostat 60mg. A further 2 patients were treated at RD during dose expansion to make the required 10 patients for the protocol defined initial analysis at which point the trial closed. At the RD (n=10) median age was 63 years (range 47-73). 80% of patients had received at least 4 prior lines of therapy (median 4, range 2-9); 50% were ISS II, 30% ISS III; 4/6 patients with evaluable FISH data had 1q gain. The median time from diagnosis to treatment for the overall population was 85.3 months (27.5-198.8). The median number of cycles received was 2.5 (range 2-8) and 2 patients remain on treatment with 8 stopped due to disease progression. The 2 patients ongoing (received 5 & 9 prior lines) had their schedule adjusted to a 5 day a week dosing to further improve tolerability. Both had a clinical response (1MR, 1PR) and remained progression free at 6 months. 3/10 patients had SD after 4 cycles, the overall response rate (≥PR) was 1/10(10%) and the clinical benefit rate (≥MR) 2/10 (20%). Overall outcomes were: PR 10%, MR 10%, and SD 30%. Median time to maximum response was 1.84 months (95% CI [1.09, 8.65]). Toxicities at the RD were manageable, 30% of patients required a dose reduction. 22 serious adverse events were reported in 16 patients across all doses, mainly infections (10/22, 45.5%). The commonest grade 3-4 toxicities reported for all 22 patients were: platelet count decrease (12, 54.5%), white blood cell decreased (6, 27.2%), diarrhoea (5, 22.7%). The most frequent grade 1-2 toxicities were fatigue (15, 68.2%), nausea (14, 63.3 %), anorexia (14, 63.6%), anaemia (13, 59.1%). 1 patient withdrew due to toxicity, and there were no treatment related deaths. Conclusions: This study demonstrated that the novel combination of CHR-3996 and tosedostat was safe and tolerable in multiply relapsed, refractory myeloma patients many of which had poor bone marrow function. The recommended dose of the combination was 20mg and 60mg, respectively. Following further adjustment to an intermittent 5 day/ week dosing schedule, treatment was well tolerated and clinical benefit observed. This suggests that further evaluation of this novel combination is warranted. Acknowledgments: This trial was part of the Myeloma UK Clinical Trial Network, ISRCTN: 24989786. Disclosures Williams: Novartis: Honoraria; Janssen: Honoraria, Other: Travel support, Speakers Bureau; Celgene: Honoraria, Other: Travel support, Speakers Bureau; Takeda: Honoraria, Other: Travel support, Speakers Bureau; Amgen: Honoraria, Speakers Bureau. Yong:Autolus Ltd: Equity Ownership, Patents & Royalties: APRIL based chimeric antigen receptor; Janssen: Research Funding. Cook:Takeda Oncology: Consultancy, Research Funding, Speakers Bureau; Amgen: Consultancy, Speakers Bureau; Sanofi: Consultancy, Speakers Bureau; Glycomimetics: Consultancy; Celgene: Consultancy, Research Funding, Speakers Bureau; Janssen: Consultancy, Research Funding, Speakers Bureau. Jenner:Amgen: Consultancy, Honoraria, Other: Travel support; Takeda: Consultancy, Honoraria, Other: Travel support; Janssen: Consultancy, Honoraria, Other: Travel support, Research Funding; Novartis: Consultancy, Honoraria; Celgene: Consultancy, Honoraria, Research Funding. Morgan:Univ of AR for Medical Sciences: Employment; Bristol Meyers: Consultancy, Honoraria; Takeda: Consultancy, Honoraria; Janssen: Research Funding; Celgene: Consultancy, Honoraria, Research Funding. Davies:Janssen: Consultancy, Honoraria; Celgene: Consultancy, Honoraria; Takeda: Consultancy, Honoraria.

Description: Key Points IGH translocations in myeloma can occur through at least 5 mechanisms. t(11;14) and t(14;20) DH-JH rearrangement-mediated translocations occur indicating these appear to occur in a pregerminal center cell.

Description: Background Treatment of relapsed/refractory multiple myeloma (RRMM) remains challenging as durable remissions are achieved in patient sub-groups only. Identifying patients that are likely to benefit prior to or early after starting relapse treatments remains an unmet need. MUKseven is a trial specifically designed to investigate and validate biomarkers for treatment optimization in a 'real-world' RRMM population. Design In the randomized multi-center phase 2 MUKseven trial, RRMM patients (≥2 prior lines of therapy, exposed to proteasome inhibitor and lenalidomide) were randomized 1:1 to cyclophosphamide (500 mg po d1, 8, 15), pomalidomide (4 mg days 1-21) and dexamethasone (40 mg; if ≥75 years 20 mg; d1, 8, 15, 21) (CPomD) or PomD and treated until progression. All patients were asked to undergo bone marrow (BM) and peripheral blood (PB) bio-sampling at baseline, cycle 1 day 14 (C1D14, on-treatment) and relapse. For biomarker discovery and validation, IGH translocations were profiled by qRT-PCR, copy number aberrations by digital MLPA (probemix D006; MRC Holland), GEP by U133plus2.0 array (Affymetrix), PD protein markers by IHC and PB T-cell subsets by flow cytometry for all patients with sufficient material. Primary endpoint was PFS, secondary endpoints included response, OS, safety/toxicity and biomarker validation. Original planned sample size was 250 patients but due to a change in UK standard of care during recruitment with pomalidomide becoming available, a decision was made to stop recruitment early. Results In total, 102 RRMM patients were randomized 1:1 between March 2016 and February 2018. Trial entry criteria were designed to include a real-world RRMM population, permitting transfusions and growth factor support. Median age at randomization was 69 years (range 42-88), 28% of patients had received ≥5 prior lines of therapy (median: 3). Median follow-up for this analysis was 13.4 months (95% CI: 12.0-17.5). 16 patients remained on trial at time of analysis (median number of cycles: 19.5; range 8-28). More patients achieved ≥PR with CPomD compared to PomD: 70.6% (95% CI: 56.2-82.5%) vs. 47.1% (CI: 32.9-61.5%) (P=0.006). Median PFS was 6.9 months (CI: 5.7-10.4) for CPomD vs. 4.6 months (CI: 3.5-7.4) for PomD, which was not significantly different as per pre-defined criteria. Follow-up for OS is ongoing and will be presented at the conference. High-risk genetic aberrations were found at following frequencies: t(4;14): 6%, t(14;16)/t(14;20): 2%, gain(1q): 45%, del(17p): 13%. Non-high risk lesions were present as follows: t(11;14): 22%, hyperdiploidy: 44%. Complete information on all high-risk genetic markers was available for 71/102 patients, of whom 12.7% had double-hit high-risk (≥2 adverse lesions), 46.5% single-hit high-risk (1 adverse lesion) and 40.8% no risk markers, as per our recent meta-analysis in NDMM (Shah V, et al., Leukemia 2018). Median PFS was significantly shorter for double-hit: 3.4 months (CI: 1.0-4.9) vs. single-hit: 5.8 months (CI: 3.7-9.0) or no hit: 14.1 months (CI: 6.9-17.3) (P=0.005) (Figure 1A). GEP was available for 48 patients and the EMC92 high-risk signature, present in 19% of tumors, was associated with significantly shorter PFS: 3.4 months (CI: 2.0-5.7) vs. 7.4 (CI: 3.9-15.1) for EMC92 standard risk (P=0.037). Pharmacodynamic (PD) profiling of cereblon and CRL4CRBN ubiquitination targets (including Aiolos, ZFP91) in BM clots collected at baseline and C1D14 is currently ongoing. Preliminary results for the first 10 patients demonstrate differential change of nuclear Aiolos (Figure 1C), with a major decrease in Aiolos H-scores in 7/10 patients from baseline to C1D14 and reconstitution at relapse. T-cell PB sub-sets were profiled at baseline and C1D14 by flow cytometry. Specific sub-sets increased with therapy from baseline to C1D14, e.g. activated (HLA-DR+) CD4+ T-cells, as reported at last ASH. CD4+ T-cell % at baseline was associated with shorter PFS in these analyses in a multi-variable Cox regression model (P=0.005). PD and T-cell biomarker results will be updated and integrated with molecular tumor characteristics and outcome. Discussion Our results demonstrate that molecular markers validated for NDMM predict treatment outcomes in RRMM, opening the potential for stratified delivery of novel treatment approaches for patients with a particularly high unmet need. Additional immunologic and PD biomarkers are currently being explored. Disclosures Croft: Celgene: Other: Travel expenses. Hall:Celgene, Amgen, Janssen, Karyopharm: Other: Research funding to Institution. Walker:Janssen, Celgene: Other: Research funding to Institution. Pawlyn:Amgen, Janssen, Celgene, Takeda: Other: Travel expenses; Amgen, Celgene, Janssen, Oncopeptides: Honoraria; Amgen, Celgene, Takeda: Consultancy. Flanagan:Amgen, Celgene, Janssen, Karyopharm: Other: Research funding to Institution. Garg:Janssen, Takeda, Novartis: Other: Travel expenses; Novartis, Janssen: Research Funding; Janssen: Honoraria. Couto:Celgene Corporation: Employment, Equity Ownership, Patents & Royalties. Wang:Celgene Corporation: Employment, Equity Ownership. Boyd:Novartis: Consultancy, Honoraria; Janssen: Consultancy, Honoraria; Takeda: Consultancy, Honoraria; Amgen: Consultancy, Honoraria; Celgene: Consultancy, Honoraria. Pierceall:Celgene: Employment. Thakurta:Celgene: Employment, Equity Ownership. Cook:Celgene, Janssen-Cilag, Takeda: Honoraria, Research Funding; Janssen, Takeda, Sanofi, Karyopharm, Celgene: Consultancy, Honoraria, Speakers Bureau; Amgen, Bristol-Myers Squib, GlycoMimetics, Seattle Genetics, Sanofi: Honoraria. Brown:Amgen, Celgene, Janssen, Karyopharm: Other: Research funding to Institution. Kaiser:Takeda, Janssen, Celgene, Amgen: Honoraria, Other: Travel Expenses; Celgene, Janssen: Research Funding; Abbvie, Celgene, Takeda, Janssen, Amgen, Abbvie, Karyopharm: Consultancy.

Description: Introduction: Multiple myeloma (MM) is more common in men than women but the mechanism(s) driving this are not understood. In our previous study (Myeloma IX) we found sex disparities in the cytogenetic lesions present in myeloma cells at the time of diagnosis and that female sex was associated with reduced overall survival in the context of treatment with traditional chemotherapy (CVAMP/MP) and thalidomide combinations. Here, we evaluate sex differences in almost 4000 patients recruited to the UK NCRI Myeloma XI trial, in which treatment exposure to lenalidomide predominated. Methods: Myeloma XI recruited newly diagnosed patients of all ages, with pathways for transplant eligible (TE) and ineligible (TNE) patients. An induction randomisation compared the triplet combination of cyclophosphamide, lenalidomide and dexamethasone to a similar combination with thalidomide (CRD vs CTD). Eligible patients underwent autologous stem cell transplant (ASCT) and in both pathways a maintenance randomisation compared lenalidomide (+/-vorinostat) until disease progression versus observation. We compared baseline characteristics of males and females using Fisher's Exact test for categorical characteristics and the Wilcoxon-Mann-Whitney test for continuous characteristics with p1 lesion present. Results: Of 3894 patients enrolled in the trial 2268 (58%) were male and 1626 (42%) were female, in keeping with the known sex disparity in MM. There was no difference in the median age, WHO performance status, ethnicity and most laboratory values of the two groups. Females were more likely to have the molecular risk lesions t(14;16) and del(17p) and had proportionately more HiR and UHiR disease, Table 1. Despite these differences, PFS and OS from induction randomisation did not significantly differ (PFS: Males 25 months, [95% CI 24, 26], Females 24 months, [95% CI 22, 25] and OS: Males 67 months, [95% CI 62, 70], Females 70 months, [95% CI 64, 74]). Molecular lesions that have been associated with outcome remained prognostic in both sexes, with a stepwise reduction in PFS and OS with cumulative risk lesions. PFS: Males SR 29 months, HiR 23 months, UHiR 16 months (p 〈 0.0001), Females SR 27 months, HiR 18 months, UHiR 17 months (p = 0.0007); OS: Males SR 77 months, HiR 59 months, UHiR 34 months (p 〈 0.0001), Females SR 82 months, HiR 54 months, UHiR 41 months (p 〈 0.0001). There was, however, no significant difference in PFS or OS when we compared males and females with a given cytogenetic lesion or cytogenetic risk. There was a significant difference in the proportion of patients of either sex who continued through the trial and underwent ASCT in the TE pathway (Males 72%, Females 67%; p = 0.031), but no significant difference in those that entered the maintenance randomisation (TE: Males 56%, Females 50%, p = 0.107; TNE Males 45%, Females 42%, p = 0.249). There was no significant PFS or OS difference by sex when analysed within each treatment pathway (TE, TNE), induction regimen (CTD, CRD) and maintenance approach (lenalidomide maintenance, observation). Conclusions: Females had a higher proportion of the adverse molecular risk lesions del(17p) and t(14;16) and were more likely to have HiR and UHiR disease. In the context of Myeloma XI trial treatment this did not correspond to a difference in PFS or OS, either overall or within the induction or maintenance randomisation treatment options (even though males were more likely to undergo ASCT). This suggests that in women the treatment delivered may have been able to overcome some of the adverse effect of the risk lesions present or that other factors affecting outcome were more important. on behalf of the NCRI Haematological Oncology Clinical Studies Group. Disclosures Cairns: Celgene, Amgen, Merck, Takeda: Other: Research Funding to Institution. Davies:Janssen, Celgene: Other: Research Grant, Research Funding; Amgen, Celgene, Janssen, Oncopeptides, Roche, Takeda: Membership on an entity's Board of Directors or advisory committees, Other: Consultant/Advisor. Boyd:Novartis: Consultancy, Honoraria; Janssen: Consultancy, Honoraria; Amgen: Consultancy, Honoraria; Celgene: Consultancy, Honoraria; Takeda: Consultancy, Honoraria. Cook:Celgene, Janssen-Cilag, Takeda: Honoraria, Research Funding; Janssen, Takeda, Sanofi, Karyopharm, Celgene: Honoraria, Speakers Bureau. Drayson:Abingdon Health: Consultancy, Equity Ownership. Gregory:Abbvie, Janssen: Honoraria; Amgen, Merck: Research Funding; Celgene: Consultancy, Research Funding. Jenner:Abbvie, Amgen, Celgene, Novartis, Janssen, Sanofi Genzyme, Takeda: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Jones:Celgene: Honoraria, Research Funding. Kaiser:Takeda, Janssen, Celgene, Amgen: Honoraria, Other: Travel Expenses; Celgene, Janssen: Research Funding; Abbvie, Celgene, Takeda, Janssen, Amgen, Abbvie, Karyopharm: Consultancy. Owen:Celgene, Janssen: Honoraria; Celgene, Janssen: Consultancy; Celgene: Research Funding; Janssen: Other: Travel expenses. Russell:DSI: Consultancy, Honoraria, Speakers Bureau; Jazz: Consultancy, Honoraria, Speakers Bureau; Pfizer Inc: Consultancy, Honoraria, Speakers Bureau; Astellas: Consultancy, Honoraria, Speakers Bureau. Morgan:Bristol-Myers Squibb, Celgene Corporation, Takeda: Consultancy, Honoraria; Amgen, Janssen, Takeda, Celgene Corporation: Other: Travel expenses; Celgene Corporation, Janssen: Research Funding. Jackson:Celgene, Amgen, Roche, Janssen, Sanofi: Honoraria. Pawlyn:Amgen, Celgene, Takeda: Consultancy; Amgen, Janssen, Celgene, Takeda: Other: Travel expenses; Amgen, Celgene, Janssen, Oncopeptides: Honoraria. OffLabel Disclosure: CTD/CRD induction therapy for myeloma, Lenalidomide maintenance 10mg 21/28 days

Description: Introduction In a subset of multiple myeloma (MM) patients the t(4;14) deregulates the histone methyltransferase, MMSET and growth factor receptor, FGFR3 and has been associated with poor prognosis. In some patients this has been ameliorated by the introduction of proteasome inhibitors but 50% of t(4;14) cases have a high-risk gene expression profile (GEP70) at presentation and derive less benefit from their use. The t(4;14), therefore, constitutes a very significant target for therapy. Despite international efforts at drug design it has proven difficult to target MMSET directly. Targeting FGFR3 has been attempted and may be effective when the gene is mutated, but this only occurs in a small proportion. We have used multi-level molecular (proteomic, gene expression, metabolomic) and phenotypic analysis to identify downstream molecules upregulated in t(4;14) MM as an alternative approach to defining novel targets for therapy. Materials/Methods The MM cell line KMS11 has t(4;14) which re-locates MMSET downstream of the immunoglobulin heavy chain gene enhancer. From KMS11 the isogenic paired cell lines non-translocated allele knock out (NTKO, retains high MMSET expression) and translocated allele knock out (TKO, low MMSET expression) have been derived using homologous recombination (Lauring et al, Blood 2008). We performed Affymetrix GEP (HG_U133_plus_2) on mRNA extracted from KMS11, NTKO and TKO cells in triplicate and analysed using Partek®. Probes were included in the analysis if they had fold change (FC) 〉2 or

Description: Key Points The type of antibody secreted at relapse can serve as a marker of clonal heterogeneity. It is important to monitor for serum FLC in the suspicion of clinical relapse to ensure that FLC relapse is not missed.

Description: Prognostic markers are important to identify high-risk patients in Multiple Myeloma (MM). Several prognostic models have been published, including parameters of tumor burden and cytogenetics. Recently the International Staging System (ISS) for Multiple Myeloma, which includes beta2-microglobulin (beta2-MG) and albumin, has been introduced for newly diagnosed patients with symptomatic MM. We previously reported about the prognostic significance of circulating proteasome levels (cProteasomes) in MM patients (Jakob et al., Blood 2007). In the present study we investigated the prognostic relevance of the bone resorption marker carboxy-terminal telopeptide of type-I collagen (ICTP) and cProteasome levels in comparison to the classical prognostic factors (beta2-MG), albumin, deletion 13q14 and type of chemotherapy (high-dose-therapy versus conventional dose chemotherapy) in 92 patients with newly diagnosed active MM. ICTP and cProteasome were significantly elevated parallel to ISS stages (P

Description: Background Transplant non-eligible (TNE) myeloma patients are a very heterogeneous group that is not well-defined on the basis of age alone, but rather by the interplay of age, physical function, cognitive function and comorbidity better defined as 'frailty'. The International Myeloma Working Group (IMWG) has published a scoring system for myeloma patient frailty that predicts survival, adverse events and treatment tolerability using age, the Katz Activity of Daily Living (ADL), the Lawton Instrumental Activity of Daily Living (IADL), and the Charlson Comorbidity Index (CCI). It has been proposed to be useful in determining the feasibility of treatment regimens and appropriate dose reductions but has not been validated prospectively. We hypothesize that by defining subgroups of patients based on the IMWG frailty score, and guiding up-front dose adjustments we can personalize therapy to improve treatment tolerability and therefore short-term outcomes, along with quality of life. In addition we plan to compare the use of single agent immunomodulatory (IMiD) based maintenance therapy with an IMiD and proteasome inhibitor maintenance doublet to try and improve long-term outcomes for patients. Study Design and Methods Myeloma XIV (NCT03720041) is a phase III, multi-center, randomized controlled trial to compare standard (reactive) and frailty-adjusted (adaptive) induction therapy delivery with the novel triplet ixazomib, lenalidomide and dexamethasone (IRd), and to compare maintenance lenalidomide (R) to lenalidomide plus ixazomib (IR) in patients with newly diagnosed multiple myeloma not suitable for a stem cell transplant. The trial outline is shown in Figure 1. All participants receive induction treatment with ixazomib, lenalidomide and dexamethasone and are randomized (R1) on a 1:1 basis at trial entry to the use of frailty score-adjusted up-front dose reductions vs. standard up-front dosing followed by toxicity dependent reactive dose modifications during therapy. Following 12 cycles of induction treatment participants alive and progression-free undergo a second randomization (R2) on a 1:1 basis to maintenance treatment with lenalidomide plus placebo versus lenalidomide plus ixazomib. Participants and their treating physicians are blinded to maintenance allocation. The primary objectives of the study are to determine: Early treatment cessation (within 60 days of randomization) for standard versus frailty-adjusted up-front dosingProgression-free survival (PFS, from maintenance randomization) for lenalidomide + placebo (R) versus lenalidomide + ixazomib (IR) The secondary objectives of the study include determining: progression-free survival (PFS) for standard versus frailty-adjusted up-front dosing reductions, overall survival (OS), overall response rate (ORR), treatment compliance and total amount of therapy delivered, toxicity & safety including the incidence of Second Primary Malignancies (SPMs), Quality of Life (QoL), cost-effectiveness of standard versus frailty-adjusted up-front dosing of IRd and cost-effectiveness of IR versus R. Exploratory analyses include the association of molecular subgroups with response, PFS and OS. Seven hundred and forty participants will be enrolled into the trial at R1 to give 80% power to demonstrate a difference in early cessation and ensure that at least 478 participants remain and are randomized at R2 (based on attrition rates in our previous study Myeloma XI). At R2 478 patients will give us 80% power to detect an eight month difference in PFS between R and IR. Disclosures Cairns: Celgene, Amgen, Merck, Takeda: Other: Research Funding to Institution. Pawlyn:Amgen, Janssen, Celgene, Takeda: Other: Travel expenses; Amgen, Celgene, Takeda: Consultancy; Amgen, Celgene, Janssen, Oncopeptides: Honoraria. Royle:Celgene, Amgen, Merck, Takeda: Other: Research Funding to Institution. Best:Celgene, Amgen, Merck, Takeda: Other: Research Funding to Institution. Bowcock:Takeda: Honoraria, Research Funding. Boyd:Takeda: Consultancy, Honoraria; Novartis: Consultancy, Honoraria; Janssen: Consultancy, Honoraria; Amgen: Consultancy, Honoraria; Celgene: Consultancy, Honoraria. Drayson:Abingdon Health: Consultancy, Equity Ownership. Henderson:Celgene, Amgen, Merck, Takeda: Other: Research Funding to Institution. Jenner:Abbvie, Amgen, Celgene, Novartis, Janssen, Sanofi Genzyme, Takeda: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Jones:Celgene: Honoraria, Research Funding. Kaiser:Takeda, Janssen, Celgene, Amgen: Honoraria, Other: Travel Expenses; Celgene, Janssen: Research Funding; Abbvie, Celgene, Takeda, Janssen, Amgen, Abbvie, Karyopharm: Consultancy. Kishore:Celgene, Takeda, Janssen: Honoraria, Speakers Bureau; Celgene, Jazz, Takeda: Other: Travel expenses. Mottram:Celgene, Amgen, Merck, Takeda: Other: Research Funding to Institution. Owen:Janssen: Other: Travel expenses; Celgene, Janssen: Consultancy; Celgene, Janssen: Honoraria; Celgene: Research Funding. Jackson:Celgene, Amgen, Roche, Janssen, Sanofi: Honoraria. Cook:Celgene, Janssen-Cilag, Takeda: Honoraria, Research Funding; Amgen, Bristol-Myers Squib, GlycoMimetics, Seattle Genetics, Sanofi: Honoraria; Janssen, Takeda, Sanofi, Karyopharm, Celgene: Consultancy, Honoraria, Speakers Bureau. OffLabel Disclosure: Frailty adjusted dosing. Ixazomib and lenalidomide combination as maintenance.

Description: Notch pathway inhibition in multiple myeloma (MM) cells is a promising new therapeutic approach since it controls myeloma cell growth as we previously demonstrated (Blood. 2004; 103:3511–3515). Notch signaling is involved in the tight interactions between myeloma cells and the bone marrow microenvironment and induces tumor cell growth in MM. We provided evidence that Notch receptors are expressed on MM cells and that Notch ligands on MM and bone marrow stromal cells activate Notch signaling through homotypic as well as heterotypic interactions in MM cells. In this study, we analyzed whether Notch signaling might be activated in osteoclasts, which express Notch receptors but not the ligands. To that end, we co-cultured MM cells and human osteoclasts, which were generated from mononuclear hematopoietic precursors of healthy donors using in vitro RANKL/M-CSF stimulation. Co-cultivation specifically activated Notch in osteoclasts and induced osteoclast activity as measured by mRNA expression of the tartrate-resistant acid phosphatase. The novel Notch pathway inhibitor, so called γ-secretase inhibitor 1 (GSI1), that we recently identified by structural comparison of known inhibitors with unknown compounds by data bank screening, specifically inhibited Notch signaling in osteoclasts and blocked their activity in this co-cultivation assay. In addition, GSI1 induced apoptosis in osteoclasts in higher concentrations. We suggest from our data that GSI treatment controls MM cell growth and concomitantly aberrant osteoclast activity in vitro and possibly in vivo, that is under current investigation. We further hypothesized that GSI1 can be combined with the proteasome inhibitor bortezomib, which has been known to have in vitro and in vivo activity against MM. We evaluated the activity of the combination of GSI1 and bortezomib against MM cell growth and survival. Proliferation of MM cell lines treated with GSI, bortezomib and their combination was determined by CellTiter-Glo® luminescent cell viability assay. AnnexinV-FITC/PI staining and cleaved poly (ADP-ribose) polymerase (PARP) staining were used to determine the degree of apoptosis. Although treatment of MM cell lines (OPM2, LP1) with either drug alone significantly inhibited proliferation and induced apoptosis with concentrations of GSI1 (30–60 μM) and bortezomib (1–4 nM), the combination resulted in synergistic inhibition of cell growth and survival. Our data suggest that combination of GSI1 and bortezomib is a rational novel treatment option in MM that simultaneously targets different proliferative and anti-apoptotic pathways. Whether this combination might also have synergistic activity against aberrant osteoclast activity in MM will be further investigated.

Description: Abstract 1899 Introduction In multiple myeloma (MM), interactions of the malignant plasma cell clone with the bone marrow microenvironment lead to an enhanced osteoclast recruitment and impaired osteoblast activity. The proteasome inhibitor bortezomib has been shown to suppress osteoclast activity, and there is recent evidence that bortezomib enhances osteoblast differentiation. The aim of this study was to investigate the effects of bortezomib on human osteoblast precursors, focusing on vitamin D (VD) dependent osteoblastic differentiation. Since vitamin D receptor (VDR) is degraded by the proteasome, we hypothesized that bortezomib could influence its signaling and hence vitamin D induced osteoblastic differentiation. This might be of clinical importance, since an increased rate of vitamin D deficiency has recently been reported in patients with MM. Methods Primary human mesenchymal stem cells (hMSC) and primary human osteoblasts (hOB) were isolated from bone marrow aspirates or from bone fragments of healthy donors undergoing orthopedic surgery, respectively. Ascorbic acid and β-glycerolphosphate were used for osteoblastic stimulation (OS), either in combination with or without vitamin D. In order to analyze the effects of proteasome inhibition on osteoblastic differentiation and activity, hMSC and hOB were incubated with bortezomib at subapoptotic doses (1 - 5 nM). In addition, coculture experiments of hMSC, hOB and myeloma cells were performed. Expression of osteocalcin and osteopontin (OPN) were quantified by real-time PCR as markers of osteoblastic lineage differentiation. Expression of VDR was analyzed by western blot in subcellular fractions and VDR signaling was investigated using luciferase reporter assays. Results In coculture experiments, myeloma cells inhibited the vitamin D dependent differentiation and activity of osteoblast precursors, e.g. coculture of hMSC with the myeloma cell line LP-1 for 4 days decreased their osteocalcin expression by 58%. Treatment with bortezomib led to an increased osteoblastic differentiation of hMSC and hOB by OS, represented by an enhanced expression of osteoblast markers osteocalcin and OPN. Importantly, this effect could be further increased, when vitamin D was added. In hMSC stimulated with OS only, addition of 5 nM bortezomib led to an 18.3 fold increase in OPN mRNA expression. In comparison, hMSC stimulated with OS + vitamin D showed a 27.5 fold increase in OPN mRNA with the addition of bortezomib. Osteocalcin expression was increased 1.9 fold by bortezomib in the presence of OS and vitamin D, but not with OS alone. Similar results were obtained with osteoblasts: Incubation with bortezomib slightly increased osteocalcin and OPN mRNA expression in cells stimulated with OS only (1.3 fold and 2.4 fold, respectively). In comparison, in cells stimulated with OS and vitamin D, bortezomib elevated osteocalcin and OPN expression 2.9 fold and 5.5 fold, respectively. Bortezomib led to an increase in nuclear VDR levels in hMSC in western blot analyses. Primary hMSC transfected with a VDR luciferase reporter construct showed a 3.7 fold increase in VDR signaling with bortezomib. Conclusion Our data show that bortezomib stimulates osteoblastic differentiation of hMSCs and hOBs and acts, at least in part, through VDR signaling. Substitution of vitamin D in multiple myeloma patients treated with bortezomib may be beneficial for bone turnover and needs clinical evaluation. Disclosures: Kaiser: Johnson & Johnson: Research Funding. Mieth:Johnson & Johnson: Research Funding. Sezer:Johnson & Johnson: Research Funding. Heider:Johnson & Johnson: Research Funding.