Abstract: Heavy light chain (HLC) assays allow precise measurement of the monoclonal and of the noninvolved polyclonal immunoglobulins of the same isotype as the M‐protein (e.g., monoclonal IgAκ and polyclonal IgAλ in case of an IgAκ myeloma), which was not possible before. The noninvolved polyclonal immunoglobulin is termed ‘HLC‐matched pair’. We investigated the impact of the suppression of the HLC‐matched pair on outcome in 203 patients with multiple myeloma, a phenomenon that likely reflects the host's attempt to control the myeloma clone. Severe ( 〉 50%) HLC‐matched pair suppression was identified in 54.5% of the 156 newly diagnosed patients and was associated with significantly shorter survival (45.4 vs. 71.9 months, P  = 0.019). This correlation was statistically significant in IgG patients (46.4 vs. 105.1 months, P  = 0.017), but not in patients with IgA myelomas (32.9 vs. 54.1 months, P  = 0.498). At best response, HLC‐matched pair suppression improved only in patients with ≥VGPR, indicating partial or complete humoral immune reconstitution during remission in those with excellent response. Severe HLC‐matched pair suppression retained its prognostic impact also during follow‐up after first response. In the 47 pretreated patients with relapsed/refractory disease, a similar correlation between severe HLC suppression and survival was noted (22.8 vs. not reached, P  = 0.028). Suppression of the polyclonal immunoglobulins of the other isotypes than the myeloma protein correlated neither with HLC‐matched pair suppression, nor with outcome. Multivariate analysis identified severe HLC‐matched pair suppression as independent risk factor for shorter survival, highlighting the impact of isotype specific immune dysregulation on outcome in multiple myeloma. Am. J. Hematol. 91:295–301, 2016. © 2015 The Authors. American Journal of Hematology Published by Wiley Periodicals, Inc.

Abstract: Antiapoptotic Bcl-2 family members have recently (re)emerged as key drug targets in cancer, with a tissue- and tumor-specific activity profile of available BH3 mimetics. In multiple myeloma, MCL-1 has been described as a major gatekeeper of apoptosis. This discovery has led to the rapid establishment of clinical trials evaluating the impact of various MCL-1 inhibitors. However, our understanding about the clinical impact and optimal use of MCL-1 inhibitors is still limited. We therefore explored mechanisms of acquired MCL-1 inhibitor resistance and optimization strategies in myeloma. Our findings indicated heterogeneous paths to resistance involving baseline Bcl-2 family alterations of proapoptotic (BAK, BAX, and BIM) and antiapoptotic (Bcl-2 and MCL-1) proteins. These manifestations depend on the BH3 profile of parental cells that guide the enhanced formation of Bcl-2:BIM and/or the dynamic (ie, treatment-induced) formation of Bcl-xL:BIM and Bcl-xL:BAK complexes. Accordingly, an unbiased high-throughput drug-screening approach (n = 528) indicated alternative BH3 mimetics as top combination partners for MCL-1 inhibitors in sensitive and resistant cells (Bcl-xL & gt;Bcl-2 inhibition), whereas established drug classes were mainly antagonistic (eg, antimitotic agents). We also revealed reduced activity of MCL-1 inhibitors in the presence of stromal support as a drug-class effect that was overcome by concurrent Bcl-xL or Bcl-2 inhibition. Finally, we demonstrated heterogeneous Bcl-2 family deregulation and MCL-1 inhibitor cross-resistance in carfilzomib-resistant cells, a phenomenon linked to the MDR1-driven drug efflux of MCL-1 inhibitors. The implications of our findings for clinical practice emphasize the need for patient-adapted treatment protocols, with the tracking of tumor- and/or clone-specific adaptations in response to MCL-1 inhibition.

Abstract: Smoldering multiple myeloma (SMM) is an asymptomatic clonal plasma cell disorder and bridges monoclonal gammopathy of undetermined significance to multiple myeloma (MM), based on higher levels of circulating monoclonal immunoglobulin and bone marrow plasmocytosis without end-organ damage. Until a Spanish study reported fewer MM-related events and better overall survival among patients with high-risk SMM treated with lenalidomide and dexamethasone, prior studies had failed to show improved survival with earlier intervention, although a reduction in skeletal-related events (without any impact on disease progression) has been described with bisphosphonate use. Risk factors have now been defined, and a subset of ultra-high-risk patients have been reclassified by the International Myeloma Working Group as MM, and thus will require optimal MM treatment, based on biomarkers that identify patients with a & gt;80% risk of progression. The number of these redefined patients is small (∼10%), but important to unravel, because their risk of progression to overt MM is substantial (≥80% within 2 years). Patients with a high-risk cytogenetic profile are not yet considered for early treatment, because groups are heterogeneous and risk factors other than cytogenetics are deemed to weight higher. Because patients with ultra-high-risk SMM are now considered as MM and may be treated as such, concerns exist that earlier therapy may increase the risk of selecting resistant clones and induce side effects and costs. Therefore, an even more accurate identification of patients who would benefit from interventions needs to be performed, and clinical judgment and careful discussion of pros and cons of treatment initiation need to be undertaken. For the majority of SMM patients, the standard of care remains observation until development of symptomatic MM occurs, encouraging participation in ongoing and upcoming SMM/early MM clinical trials, as well as consideration of bisphosphonate use in patients with early bone loss.

Abstract: Background: Immunoglobulin-like transcript 2 (ILT2/CD85j) belongs to the Ig superfamily and has homology to the killer cell inhibitory receptors (KIRs). It is expressed on natural killer (NK) cells, monocytes, macrophages, dendritic cells and (naive) B lymphocytes. A differential expression of ILT2 was described for monoclonal gammopathy of undetermined significance (MGUS) and multiple myeloma (MM). Gene expression profiling studies found ILT2 to be downregulated 8.26 fold in myeloma as compared to MGUS, being the most differentially expressed gene between these two subsets. However, as RNA from CD138+ cells was used in this analysis, a varying percentage of normal, non-malignant plasma cells will impact on the results, especially in MGUS cases. Aims: We aimed to delineate ILT2 expression in different plasma cell subsets (normal compared to monoclonal cells) in MGUS and MM and the eventual prognostic impact of a differential expression level. Methods: ILT2 expression was measured by flow cytometry using a PE-conjugated antibody (clone HP-F1, Beckman Coulter) in a series of 30 MGUS patients and 91 myeloma patients. Phenotypically normal and malignant plasma cells were defined by differential expression of CD38, CD45, CD19 and CD56. Expression levels are given as mean fluorescence intensity (MFI) after correction for background staining. Results: ILT2 was not differentially expressed in monoclonal plasma cells from patients with MGUS (MFI median 112.0, range 13.5–274.4) and myeloma (MFI median 96.6, range 0.4–454.5). In contrast, monoclonal cells from MGUS and MM showed a significantly lower expression of ILT2 as compared to phenotypically normal plasma cells in the majority of samples (p=0.007). Results were confirmed by quantitative real time PCR studies in 25 MM patients showing a linear correlation of ILT2 mRNA levels with the intensity of ILT2 protein expression. ILT2 levels did not vary with state of disease and showed no correlation with clinical parameters or prognosis in our series of myeloma patients. Conclusions: In the majority of patients with monoclonal plasma cell disorders, ILT2 seems to be downregulated at an early stage of disease, i.e. upon transformation from a normal plasma cell to the MGUS/MM stage. The expression level of ILT2 in monoclonal plasma cells is neither correlated with the state of disease (MGUS versus newly diagnosed myeloma versus advanced disease) nor to prognosis of myeloma patients or other clinical parameters.

Abstract: Introduction: Outcome of patients (pts) with refractory AML or following relapse is considered dismal and usually reported as refractory/relapsed. Here we analyzed long term outcome of refractory and relapsing pts separately over a 10 year (y) period from two prospective, non-age-limited, adult AML studies. Results have been published or presented previously as part of the German AML Intergroup studies1,2. However, incidence, characteristics, treatment and outcome of refractory and relapsed pts have not been evaluated. Patients and Methods: A total of 1621 pts from the OSHO 2002 ≤60 y (n=740) and 2004 & gt;60 y (n=881) with newly diagnosed AML (except acute promyelocytic leukemia) and eligible for chemotherapy were analyzed. The gender was male in 51.7% of pts. AML type was de novo in 66.6%, followed by secondary AML in 25.8% and therapy related in 7.6%. Cytogenetic risk status was normal in 47.9%, intermediate in 16.3%, unfavorable in 15.3%, monosomal in 12.6% and favorable in 7.9%. Molecular analysis revealed wildtype (wt) FLT3 in 80.9% and FLT3 ITD mutated (mut) in 19.1% of pts. NPM was mutated in 30.2% of 1124 pts. In the AML 2002 and 2004 studies (NCT 01414231; NCT 01497002; NCT00266136), pts were randomly (9:1) assigned to remission induction by cytarabine (1 g/m2 bid d 1, 3, 5, 7) and Idarubicin (AML 2002) 12 mg/m2/d d 1-31 or mitoxantrone (AML 2004) 10 mg/m2/d iv d 1 - 32 or to a common arm consisting of a 3+7 scheme 3. Pts in complete remission (CR) received consolidation and stem cell transplantation (HSCT) according to cytogenetic risk and donor availability1,2. Pts with partial remission (PR) or non-response (NR) to two induction cycles were considered refractory. Pts achieving CR and relapsing thereafter were considered relapses and treated with MitoFlag or Flag-Ida4. Results: The majority of pts [median age 62 (range 17-87) y] entered CR or CRi after one or two induction cycles (n=1144; 70.6%). OS was 31.9 (29.5-34.4) % @5y and 26.0 (23.4-28.9) % @10y. Results were age dependent and superior in younger pts with an OS of 46.8 (43.1-50.7) % @5y compared to 19.3 (16.7-22.4) % @ 5y in elderly. Age, cytogenetics and NPM1 were determinants for CR and WBC (p & lt;0,001), gender (p & lt;0,05) and AML type (p & lt;0,01) for OS. FLT3-ITD mut was an important determinant for relapse free survival in pts ≤60y. A total of 238 (14.7%) of 1621 pts, 23.5% in the younger and 76.5% in the elderly study, were refractory (PR 60.1%, NR 39.9%). Pts had a median age of 66 (range 23-83)y. OS of refractory pts was 11.4 (7.9-16.6)% @5y, and dependent upon PR [(13.1 (8.1-21.1) % @10y] and NR [5.2 (2.1-12.6) % @5y; p=0.0003] . Intensive chemotherapy ± HSCT and hypomethylating agents (HMA) were able to induce CR in 24.8% of pts. CR and non-CR pts had an OS of 42.7 (31.4-58.2) % @5y and an OS of 3.7 (1.7-8.0) % @2y, respectively. Risk factors for OS in refractory pts were age and type of therapy (p & lt;0.0001). Almost all long term survivors were treated with HSCT. Of the 1144 CR/CRi pts, 582 relapsed 1-121 months (mts) after CR. Relapse occurred in 34.0% ≤6 mts, in 38,8% between 7-18 mts and in 12,2% & gt;18 mts. Age, cytogenetic risk, type of AML, interval CR to relapse and HSCT were the dominant factors for relapse. CR2 was achieved after intensive chemotherapy ± HSCT, ± DLI and HMA in 227 pts (39.0%), 54.5% in the AML 2002 and 28.4% in the AML 2004. OS of relapsed pts was 13.8 (11.1 - 17.3) % @5y and 10.9 (7.4 - 16.2) % @10y and was higher in the younger with 23.4 (18.2-29.9) % @5y as compared to elderly pts 6.9 (4.4 - 11.0) % @5y. Pts with CR2 had a LFS of 24.9 (19.5-31.7) % @5y and was highest in patients & lt;60y when intensive chemotherapy followed by HSCT was involved. Independent risk factors for OS in relapsed pts were age, cytogenetic risk, interval CR1 to relapse and type of therapy. Relapsed pts with HSCT in CR1 showed a trend for reduced survival. Conclusions Outcome of pts with refractory and relapsed AML is unsatisfactory but consistent & gt;10% @5y. A differential response is observed in refractory and relapsed pts and is dependent upon PR, NR and the achievement of CR. Increase of CR rate in younger but especially in elderly pts with second generation TKI, reduction of TRM using FLT3-inhibitor monotherapy and the option to treat pts ineligible to chemotherapy promise better outcome in refractory and relapsed AML. 1Büchner et al. JCO 2012; 2Niederwieser et al Blood 2016; 3Mayer et al. NEJM 1994; 4Thiel et al. Ann Oncology 2015 Disclosures Niederwieser: Daichii: Speakers Bureau; Cellectis: Consultancy. Scholl:Gilead: Other: Project funding; Daiichi Sankyo: Other: Advisory boards; AbbVie: Other: Advisory boards; Pfizer: Other: Advisory boards; Novartis: Other: Project funding. Zojer:Amgen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees. Sayer:Novartis: Other: none. Schwind:Daiichi Sankyo: Honoraria; Novartis: Honoraria, Research Funding. Maschmeyer:Gilead, Janssen Cilag, Astra Zeneca; BMS, Merk-Serono: Honoraria. Hochhaus:Pfizer: Research Funding; Novartis: Research Funding; BMS: Research Funding; Incyte: Research Funding; MSD: Research Funding. Al-Ali:Celgene: Research Funding; Novartis: Consultancy, Honoraria, Research Funding; CTI: Honoraria.

Abstract: Abstract 1817 Introduction: Identifying patients with optimal response and long survival is important for clinical guidance because patients with these features are likely not to need further therapy. The techniques applied for classifying these patients should be readily available, standardized, and not liable to subjective interpretation. Here we compare the clinical usability of Hevylite™ (HLC) assay, FLC assay, IFE (immunofixation electropheresis), PMPC (bone marrow plasma cell) infiltration and isotype suppression for identifying patients at their best response with long term survival. Methods and Patients: 65 multiple myeloma patients (median age at maximum response 64, range 33–85; 42 IgG, 23 IgA) were enrolled following the minimum assignment of very good partial response using international myeloma working group guidelines. Patients had been enrolled into various clinical trials and been treated with different induction protocols (VAMP, VMCP+IFNa2b, Thal-Dex, MP, VMP). Median follow was 4.5 years, range 0.5–12 years. Heavy/light chain analysis was retrospectively performed for the monoclonal plasma cell immunoglobulin and its isotype matched pair (42 IgGκ / IgGλ and 23 IgAκ / IgAλ) using commercially available immunoassays (Hevylite™, The Binding Site, Birmingham, UK). Isotype matched immunoparesis was recorded if the patients immunoglobulin concentration was 33% below the bottom of the normal range (IgGk, IgGl, IgAk, IgAl), similarly immunoparesis was assessed if the patients total immunoglobulin levels were 33% below the normal range (IgG, IgA, IgM). Results were compared to bone marrow biopsy, serum free light chain (Freelite™, The Binding Site, Birmingham, UK) and standard immunoglobulin assays. Overall survival was estimated by the product limiting method of Kaplan Meier and survival compared using the log rank test, proportional hazards were assessed using the Cox proportional hazard model. Results: Comparison of patients at maximum response with and without IF-positivity, abnormal HLC ratios, abnormal FLC ratios or BMPC infiltration 〉 5% did not reveal significantly different survival rates. Only patients with an abnormal HLC ratio showed a tendency for shorter survival (table 1). When all markers were combined a difference in the 5 year survival rate was noted (50% as compared to 100%), but due to the limited power, the statistical analysis revealed a tendency for reduced survival only. Discrimination of patients according to HLC pair suppression produced a highly significant difference in overall survival with a 5 year survival rate of 43% compared to 70% (figure 1). Median overall survival was 4.8 years vs. 8.5 years (HR, 2.5 CI: 1.1–5.54,p 〈 0.02). In contrast, suppression of the non-involved isotype immunoglobulin (i.e. IgG concentrations in an IgA MM patient) was not found to be associated reduced overall survival (IgG or IgA, p=0.75, IgM, p=0.9) Discussion: These findings show the importance of immunoparesis at time of maximum response. This phenomenon is specific to the non-involved isotype matched immunoglobulin suggesting a preferential isotype specific inhibition mechanism not previously identified. Interestingly, among the other parameters only abnormal heavy light chain ratio showed a tendency for shorter survival. However, when all of the factors were considered together a small population (4/61, 7%) was identified as having an exceptionally long remission (OS, median: 5.9 years (2.0 – 10.2) Conclusion: The non-involved isotype matched pair suppression has previously been shown to be a prognostic factor in MGUS transformation and in predicting progression free survival in MM patients. Here for the first time we identify this marker as being the most important marker in predicting outcome at maximum response. Disclosures: Carr-Smith: Binding Site: Employment. Hughes:Binding Site: Employment. Harding:Binding Site: Employment.

Abstract: In this study we compare the efficacy and toxicity of double T with M 200 with triple T using M 100 in newly diagnosed pts with MM. 175 pts have as yet been enrolled and 135 have been randomized after VAD induction treatment and stem cell collection to either tandem or triple transplantation. Reasons for non-randomization were too early for T (n=22), PD after induction (n=5), early death (n=3), toxicity (n=3), pt. refusal (n=3), and others (n=4). Median age of the 135 pts randomized was 59 years (range: 27–70 years). Stage I: 8%, stage II: 17%, stage III: 75%, Paraprotein Isotypes: IgG: 55%, IgA: 25%, IgD: 2%, IgM: 1%, Light chain: 17%. Induction treatment: 3 cycles of VAD; stem cell priming: IEV (ifosfamide (2g/m2)-etoposide (150mg/m2), d1–3; epirubicin (50mg/m2), d1) and G-CSF (5mg/kg) from d4. Conditioning regimen: M 200 mg/m2 or M 100 mg/m2 plus G-CSF; day 5 until WBC 〉 2000/ml. Pts with ≥ SD after T were subsequently randomized to interferon 3MU, TIW (Schering Plough) plus prednisone (25mg, po., TIW), or interferon alone. QoL was assessed with the EORTC QLQ C30 instrument. Chi2 test for trend was used for comparison of response and survival endpoints were estimated by the Kaplan-Meier product limit method. Response rates after VAD were CR: 11%, PR: 65%, SD: 22% and PD: 2%. Median time from start of VAD to start of T was 137 in the double and 139 days in the triple T arm. Response rates did not differ between pts treated with double or triple T (CR: 47% vs. 43%, PR: 47% vs. 47%, SD 2% vs. 6%, PD: 4% vs. 4%, p=0.60, respectively). Median PFS for both groups combined was 36 mos, but showed a tendency for shorter PFS in pts on triple T (23 mos. vs. 37.5 mos; HR 1.26, 95% CI: 0.72–2.23, p=0.21). Median of OS has not been reached yet, but did not differ between both groups. Hematological toxicity was similar in both groups. There was a tendency for more grade 2–4 mucositis and for grade 3–4 vomiting, nausea, and fatigue in the double T group. Global QoL (questions 29 and 30) was comparable between both groups, before (5 (2.5–6.5) vs. 5 (4.5–6)) and after double (5.8 (3–8.5) or triple T (6 (2.5–7)). In conclusion, triple T with intermediate dose M resulted in similar response rates, slightly shorter PFS but similar OS and was associated with less mucositis and slightly less vomiting, nausea and fatigue. Progression-free survival by randomization group Progression-free survival by randomization group

Abstract: Background: Acute renal failure (ARF) is a frequent complication of multiple myeloma (MM) and most frequently due to clonotypic light chains (LC) causing cast nephropathy, which is associated with fast deterioration of renal function, increased risk for infections and shortened survival. Here we present the final results of a phase II study employing lenalidomide-dexamethasone as treatment for patients with acute light-chain induced ARF. Patients and methods: 35 patients with LC-induced ARF have been enrolled. Cast nephropathy was confirmed in all 15 patients who had a renal biopsy. Patients with previously unknown MM must have presented with eGFR 〈 50ml/min and serum creatinine ³2.0mg/dL, and those with previously established diagnosis must have had documented eGFR ³ 60ml/min and serum creatinine ≤1.2mg/dL within 6 weeks before deterioration of eGFR to 〈 50ml/min and of serum creatinine to ≥ 2mg/dL due to LC-induced kidney injury. Nine cycles of Lenalidomide, day 1-21, q28 days, with dose adaptation according to eGFR (eGFR 30 – 50ml/min: 10 mg daily, eGFR 〈 30ml/min without requiring dialysis: 15mg q 48 hrs., eGFR 〈 30ml/min requiring dialysis: 5 mg daily following each dialysis) and dexamethasone (Dex), 40 mg, day 1-4, 9-12 and 17-21 during the first cycle and thereafter 40 mg once weekly were planned. Renal response was defined as previously described (Dimopoulos et al, Clin Lymphoma Myeloma. 2009, Ludwig et al. JCO 2010). Results: Patient's median age was: 66 (45-87), 28 patients had newly diagnosed and 7 previously established MM. 5.7% had ISS stage II, 94.3% stage III. 18 patients had light chain myeloma, 14 IgG, and 3 IgA isotype. Adverse cytogenetics t (4; 14) ± del17q ± 1q21 were detected in 14/29 patients. 4/35 patients died and 5 discontinued therapy (3 due to AEs, 1 due to PD, and 1 due to withdrawal of consent) within the first 2 cycles, leaving 26 patients for per protocol (PP) analysis. Median follow up was 17.7 months. Responses were seen in 25/35 (71.4%) patients; 7 (20%) had CR, 3 (8.6%) VGPR, 14 (40%) PR, and 1 (2.9%) MR. Median time to first and to best myeloma response was 28, and 92 days, respectively. Median baseline concentration of involved FLC was 5.465mg/L (range: 147–42.700mg/L) and 8350mg/L (range: 234– 35.500mg/L) in patients reaching ≥PR and ≤MR, respectively, and decreased significantly to a median of 95.75mg/L (range: 11.3–5.630mg/L, p 〈 0.001) in the former, but not in the latter group. Renal response was observed in 16 (45.7%) of 35 patients (CRrenal, 5(14.2%), PRrenal, 7(20%), MRrenal, 5(14%)). Median time to renal and to best renal response was 28 and 157 days, respectively. Median eGFR increased significantly in patients with ≥ PR from 17.1ml/min at baseline to 39.1ml/min at best response (p 〈 0.001), and from 23.7ml/min to 26.0ml/min in patients with ≤ MR (p=0.469) (figure 1A). Median PFS and OS were 5.5 and 21.8 months in the ITT and 12.1 and 31.4 months, respectively, in the PP group (figure 1B). Grade 3/4 anemia was seen in 43%, thrombocytopenia in 23% and neutropenia in 15% patients. Other non-haematologic AEs consisted mainly of grade 3-4/5 infection in 38%/9%, and of grade 3-4/5 cardiac toxicity in 11%/9% patients. Grade 3 diarrhea and vomiting/emesis were noted in 1 patient each. Conclusion: Lenalidomide (with dose adapted to eGFR) plus initial high dose Dex during the first cycle and low dose Dex during subsequent cycles resulted in rapid reduction of involved LC within 28 days in patients with ≥ PR. Overall, 71.4% of patients had a myeloma and 45.7% a renal response. Median eGFR increased significantly in patients with ≥ PR from 17.1ml/min at baseline to 39.1ml/min. Elderly patients experienced more toxicity and had more treatment discontinuations. Figure 1A. Median eGFR in patients with CR-PR and MR-NR at baseline and at best response. Figure 1A. Median eGFR in patients with CR-PR and MR-NR at baseline and at best response. Figure 1B. PFS and OS in the intent to treat and per protocol population. Figure 1B. PFS and OS in the intent to treat and per protocol population. Disclosures No relevant conflicts of interest to declare.

Abstract: Background: Despite significant progress in the treatment of multiple myeloma (MM) through the introduction of immunomodulatory drugs and proteasome inhibitors, therapeutic progress is limited for high-risk patients. Therefore, it is essential to define and validate novel drug targets in myeloma to implement personalized treatment options, predict drug activity and finally improve treatment outcome for all subgroups of MM patients. In the current study we aimed to analyse the prognostic value of maternal embryonic leucine zipper kinase (MELK) in MM and investigated the activity of a small molecule inhibitor of MELK (OTSSP167). Methods: MELK expression levels were analysed in two large cohorts of publically available gene expression (GEP) datasets (GSE2658 and GSE9782; n=551 and n=264, respectively) and 8 human myeloma cell lines (HMCLs). The utility of MELK as potential drug target in MM was investigated by using a selective small molecule inhibitor against MELK (OTSSP167). HMCLs were treated at varying concentrations (0-1000 nM) and analysed for viability, apoptosis and cell cycle status. Regulatory networks involved in the mechanisms of OTSSP167 were revealed by quantitative PCR (qPCR) and proteomic profiling of HMCLs after short-term (5 hours) treatment with OTSSP167 at 25-50 nM. Results: The prognostic impact of MELK was studied in two publically available GEP-datasets (GSE2658 and GSE9782). Interestingly, MELK expression was significantly elevated in the GEP-defined high-risk proliferation associated molecular subgroup (P 〈 0.001). High levels of MELK expression were accordingly associated with poor prognosis. We observed significantly reduced overall survival in patients with high compared to low MELK levels treated within the total therapy 2 (P=0.0003), total therapy 3 (P=0.04) and the APEX trial protocol (P=0.002). These results pointed to a role for MELK as potential drug target in high-risk patients. To test this, we used a highly selective inhibitor of MELK (OTSSP167). In line with their proliferative character, MELK expression was detected in 8 of 8 HMCLs. Treatment with OTSSP167 led to a dose-dependent reduction of viability in all HMCLs tested (median IC50: 10.16 nM, range: 7.6 - 15.2 nM). Importantly, we also detected synergistic and additive drug activity of OTSSP167 in combination with pomalidomide and carfilzomib. OTSSP167 induced apoptosis in all HMCLs investigated, verified by annexin V/7-AAD staining, detection of cleaved PARP and mitochondrial membrane depolarization. The apoptotic effects might be attributed to a significant downregulation of IRF4 (up to 0.75±0.27 fold reduction, P=0.009) and MCL-1 (up to 0.51±0.09 fold reduction, P=0.002) expression. We also observed accumulation of MM cells in the G2 phase of the cell cycle (OPM-2: 24% vs 42%, MM.1S: 23% vs 38.8% of cells in G2 phase without or with OTSSP167 at 25 nM for 48 hours, P 〈 0.001). This was associated with downregulation of central genes involved in the propagation of the cell cycle, including PLK-1, cyclin B1 and aurora kinase A (up to 0.82±0.08, 0.93±0.04 and 0.88±0.08 fold reduction, respectively; P 〈 0.0001). We also detected downregulation of cyclin D1 (up to 0.41±0.3 fold reduction, P=0.03). These results were confirmed at the protein level by using proteomic profiling of three HMCLs after 5 hours of treatment with OTSSP167 at 50 nM. Again, we observed deregulation of proteins involved in the initiation of mitosis (cyclin B1, aurora kinase A, nucleolin). Of note, we also detected upregulation of several proteins involved in protein folding and stabilization (e.g. Csp, HSP90 alpha and HSP90 beta) as well as glycolysis (e.g. ENO1, ALDOA, G3P2, TPI1), suggesting that these factors might regulate potential drug resistance mechanisms. Conclusion: Our findings reveal MELK expression as a novel poor prognostic marker in newly diagnosed and relapsed MM, depicting a group of high-risk patients. Inhibition of MELK with OTSSP167 led to the induction of apoptosis and cell cycle arrest by targeting central genes of the MM signaling network (e.g. MCL-1, cyclin D1, aurora kinase A). Moreover, combination of OTSSP167 with established anti-MM drugs showed synergistic activity. These results emphasize to initiate further pre-clinical and clinical testing of MELK inhibition as a novel drug target in MM, especially for patients at high-risk. Disclosures Ludwig: Takeda: Research Funding; Celgene Corporation: Honoraria, Speakers Bureau; Onyx: Honoraria, Speakers Bureau; Bristol Myers Squibb: Honoraria, Speakers Bureau; Janssen Cilag: Honoraria, Speakers Bureau.

Abstract: Introduction Carfilzomib-based induction therapy is highly effective in newly diagnosed pts with multiple myeloma (NDMM), but information on quality of life (QoL) during first line and maintenance therapy is not available. Here, we analyze patient-reported QoL in transplant-non eligible (TNE) NDMM pts randomized to either KTd or KRd induction therapy followed by second randomization to carfilzomib maintenance, or control. Patients and Methods At time of analysis, 101 TNE pts with NDMM had been enrolled, but QoL data documented for ≥ 2 cycles were available in 78 pts so far (median age: 75 years, ISS stage I: 26.6%, II: 35.4%, III: 38.0%, ECOG status 0: 51.9%, 1: 48.1%). Patients were randomized to either 9 cycles KTd or KRd, and subsequently (46 pts with ≥PR) to either carfilzomib maintenance therapy (d1 and 15) or to control for 12 months. Carfilzomib was administered twice weekly (27mg/m2) during cycles 1 and 2, and thereafter weekly at a dose of 56mg/m2. Thalidomide was given daily at 100mg (50mg in pts ≥75 years), lenalidomide at 25mg, d1-21 per 4 week cycle, and dexamethasone at 40 mg (20mg in pts ³75 years) once weekly. QoL was assessed by the QoL questionnaire EORTC QLQ-C30. Assessments were done at baseline, and monthly thereafter for 21 months. A two-sided t-test was used for comparison with the general population. Wilcoxon signed-rank tests were applied to evaluate differences in QoL dimensions within the treatment groups. A clinically meaningful improvement has been defined as a change of ≥10 score points. Results Comparison with the general population : Mean scores for health-related global QoL (54.1±22.6) and physical functioning (61.2±25.0) were significantly lower in pts compared to those reported for the general population of similar age (67.2±20.6, p & lt;0.001, and 80.6±19.7, p & lt;0.001, respectively) (Nolte S et al., Eur. J. Cancer 2019). Induction therapy: Health-related global QoL showed a clinically relevant improvement during carfilzomib-based induction therapy in both treatment groups (KRd: 54.5±19.9 to 65.0±20.2, p=0.10, KTd 53.6±24.8 to 68.2 ± 19.4, p=0.04), but a statistically significant increase in score points was noted in the KTd arm only. For physical functioning, a clinically relevant improvement was noted solely in pts on KRd, but the increase was not statistically significant (59.2 ± 22 to 73.2 ± 23.8, p=0.15), while during KTd no relevant changes were noted. Further clinically relevant improvements during induction therapy were observed for role functioning (KTd: 45 ± 39.3 to 61.6 ± 33.5, p=0.08, KRD: 51.5 ± 34.9 to 66.7 ± 30.1, p=0.29), emotional functioning (KTd: 61.2 ± 27.4 to 73.2 ± 20.5, p=0.04, KRd: 58.3 ± 23.2 to 73 ± 26.7, p=0.10), and pain with a statistically significant decrease in respective scores in both arms (KTd: 47.7 ± 37.4, to 24.2 ± 26.1, p=0.01, KRd: 54.8 ± 33.2 to 20.8 ± 21.5, p & lt;0.001)(Figure 1). Neuropathy, however, worsened clinically relevant and statistically significant in KTd treated pts (15.4 ± 24 to 27.8 ± 26.4, p=0.03), while during KRd treatment, no change was noted (22.2±30.8 to 22.2±28.0, p=0.66). Likewise, no changes were observed for nausea/vomiting, diarrhoea, constipation, fatigue, and cognitive function, while a clinically relevant improvement in social function was noted in pts during KRd induction (66.2±31.4 to 80.8±27.7, p=0.13). Maintenance phase: Pts randomized to carfilzomib maintenance showed no clinically relevant change in health-related QoL score (70.3± 17 to 63.9±25.3), similar to the findings in the untreated controls, which showed a clinically not relevant improvement in scores (66.7.±21.0 to 75.9±18.8). The scores for physical functioning remained rather stable during the maintenance period and values at end of therapy or observation appeared similar between the carfilzomib (77.1±21.6) and the control group (83.7±25.4). Conclusion Health-related global QoL and physical functioning in our pts with TNE NDMM was significantly impaired at start of therapy compared to the general population. During carfilzomib-based induction TX, clinically meaningful improvements in health-related global QoL, physical (only in KTd), emotional, role, and social (only in KRd) functioning, and pain were achieved. Neuropathy worsened during KTd. Maintenance treatment with carfilzomib was well tolerated without a clinically relevant change during the treatment period or statistical significant difference to the untreated controls. Disclosures Ludwig: Seattle Genetics: Other: Advisory Boards; Sanofi: Other: Advisory Boards, Speakers Bureau; Bristol Myers: Other: Advisory Boards, Speakers Bureau; Janssen: Other: Advisory Boards, Speakers Bureau; Celgene: Speakers Bureau; Amgen: Other: Advisory Boards, Research Funding, Speakers Bureau; Takeda: Research Funding. Podar:Amgen, BMS-Celgene, Janssen, Roche: Consultancy, Honoraria, Research Funding. Willenbacher:Amgen, Janssen, Takeda, BMS-Celgene: Consultancy, Honoraria, Research Funding. Petzer:Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees; Kite-Gilead: Honoraria, Membership on an entity's Board of Directors or advisory committees; Amgen: 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: Honoraria, Membership on an entity's Board of Directors or advisory committees; Roche: Honoraria, Membership on an entity's Board of Directors or advisory committees. Schreder:BMS-Celgene, Amgen: Consultancy. Agis:Janssen: Honoraria, Research Funding; Amgen: Honoraria; BMS: Honoraria; Celgene: Honoraria; Takeda: Honoraria. Greil:Abbvie: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel, accomodations, expenses, Research Funding; Takeda: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel, accomodations, expenses, Research Funding; Daiichi Sankyo, Gilead: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel, accomodations, expenses, Research Funding; MSD Merck: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel, accomodations, expenses, Research Funding; BMS: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel, accomodations, expenses, Research Funding; Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel, accomodations, expenses, Research Funding; Astra zeneca: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel, accomodations, expenses, Research Funding; Janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel, accomodations, expenses, Research Funding; BMS/celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel, accomodations, expenses, Research Funding; F. Hoffmann-La Roche: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel, accomodations, expenses, Research Funding. OffLabel Disclosure: Use of Carfilzomib in myeloma first-line treatment