Chng, Wee Joo

Abstract Background Waldenström macroglobulinaemia (WM) is an uncommon indolent B-cell lymphoproliferative characterized by bone marrow infiltration by lymphoplasmacytic cells and an IgM paraproteinemia. This study analyzed the impact of cytogenetics in WM and the pattern of evolution in 73 cases from the Mitelman database and 14 cases evaluated at the Mayo Clinic Arizona (MCA). Patients and Methods The Mitelman database of Chromosome aberrations in cancer (Mitelman et al., 2007) was searched, and 73 WM karyotypes were selected. We also evaluated 14 cases seen at MCA with karyotype analysis at diagnosis. An Excel spreadsheet in which the rows of the first column were labeled to represent each band of a 360-band human chromosome ideogram was created as previously described (Hoglund et al., 2001; Horsman et al., 2003) All karyotypes were scored individually in successive columns for net gain and loss of each chromosome band (loss=0 and gain=1). Recurrent abnormalities were defined as those that were involved in >5% of cases. Histograms of the number of abnormalities per tumor (NAPT) were then plotted, and the modal value extracted as variable called time to occurrence. Statistics correlation between the presence and absence of different abnormalities was analyzed using Spearman correlation matrices. P value of <0.05 was considered as statistical significan Results In total 73 cases of newly diagnosed WM from the Mitelman database were included in the analysis. The median chromosome number was 46 (Range 40 to 49).The most common abnormalities were loss of 6q21 (10%) (Fig 1), +3 (7.1%), loss of X (6%) and −10, −20, −21, +12, +18 and +5 (5.71% respectively). The most common translocation was t(8;14) (4%).The most recurrent breakpoints in our series include: 14q32 (6%), 6q21 (5%), 8q24 (5%), 18q21 (4%) and 19q13 (4%). In the MCA cohort, 14 karyotypes were reviewed and only 3 cases exhibited an abnormal result. Deletion of 6q21, 20q11 and a Robertsonian translocation t(13;14) were reported (3/11, 21%). In the 6q21 case, FISH analysis confirmed the deletion of BLIMP1 on 6q. One case exhibited a 20q deletion in a WM with kidney amyloidosis patient. Discussion In this comprehensive analysis we show a very small complexity of recurrent abnormalities expressed by conventional karyotype analysis in WM. The incidence of 6q21 deletion was 10% by conventional cytogenetics and it is been reported as high as 34% when analysed by FISH (54% when cytoplasmic immunoglobulin M-FISH was used). Interestingly we report the case of a patient with 20q deletion at diagnosis in the MCA cohort. To date, only a limited number of cases with del(20q) as a sole cytogenetic anomaly have been reported in plasma cell dyscrasias, either at diagnosis or later in the disease course. The recurrent immunoglobulin gene translocation is known to be involved in the initial oncogenetic events in plasma cell dyscrasias and, so it is important to identify whether there are any masked translocations involving immunoglobulin genes and 20q in these cases. Figure 1. 6q21 deletion and Waldenstrom Macroglobulinaemia Figure 1. 6q21 deletion and Waldenstrom Macroglobulinaemia

Abstract Bortezomib and related proteasome inhibitors have profound pre-clinical and clinical activity in Multiple Myeloma (MM). However, the critical molecular target(s) modulated by proteosome inhibition remains unknown. The overall response rate to bortezomib in relapsed and refractory MM patients is consistently 35%–50%, suggesting specific molecular targets or resistance mechanisms are inherent in patients. None of the known effects of bortezomib has been shown to correlate with clinical responses in patients or to explain the unique sensitivity of MM (as opposed to other malignancies) to these reagents. Therefore, in this study, we have conducted a small interfering RNA (siRNA) screen of the druggable genome in human myeloma cells to identify genes that modulate sensitivity to bortezomib. KMS11 human myeloma cells were reverse transfected with 13,984 synthetic short interfering RNAs (siRNA) against each of 6992 druggable targets (2 siRNA/gene with a single-siRNA per well/384 well format). At 24 hours post transfection, bortezomib was added at IC10, 30, 60 and 90. Cell viability was measured by ATP-dependent luminescence assay 72 hours post drug treatment. The resulting data from primary screening was evaluated for multiple quality control metrics and found to exceed all expected performance parameters with >99% global transfection efficiency, <0.25 CV values across the dataset with minimal plate-to-plate and set-to-set variation observed. From analysis of the primary screening data, a core panel of 320 (4.6% of druggable targets in library) bortezomib sensitizers were identified. 187 (58%) of these were further confirmed in a secondary screening experiment by multiple (2 to 4) independent siRNA. Among these 187 genes (2.6% of the genes investigated), some known targets, such as proteasome subunits are evident. Other genes belonging to the same functional gene families (e.g. TNF receptor family, Ras family, kinases, oncogenes and transporter proteins) or functioning within the same network of signal transduction (e.g. NF-kB, Wnt and estrogen receptor pathways) are evident. Our primary screen also identified genes that attenuate bortezomib-induced cytotoxicity. Members in this group include genes implicated in the negative regulation of cell proliferation and survival, such as NF-kB inhibitors, JNK pathway activators, tumor suppressors, apoptosis inducers and phosphatases. These studies enable dissection of the molecular mechanism of bortezomib in myeloma cells and may serve to point to biomarkers for response prediction and novel chemotherapeutic combination therapies.

Abstract Genetic abnormalities are important in the pathobiology of myeloma and established prognostic factors. High-density aCGH allow global unbiased detection of genomic gains and losses. In this study, we attempt to identify survival critical genomic aberrations by correlating aCGH-defined abnormalities with survival in 2 different cohorts of patients. aCGH was performed in 64 MM patients treated with high dose therapy from the Mayo Clinic using Agilent’s 44k DNA microarray genechip. In addition, a publicly available aCGH dataset performed in 67 MM patients treated with total therapy from the University of Arkansas Medical School using the lower density Agilent 22k chip (Human 1A v2) was also analyzed. Base 2 logarithms of the ratios between red and green intensities (log-ratios) were treated as a primary measure of copy number ratio between tumor and normal samples. To detect the regions of genomic aberration, values of a sliding window of 15 consecutive log-ratios were compared with those of an artificial ‘reference’ chromosome using the Wilcoxon rank sum test. The reference chromosome, constructed for each sample, was assembled by collecting log-ratio values close to zero. For this, 15 randomly sampled log-ratios from autosomal regions whose p-value of Wilcoxon signed rank test against 0 was larger than 0.05 were recursively accepted until the number of log-ratios in the assembled reference chromosome reached 1000. The p-values and their corresponding false discovery rates (q-values) for the copy number gain or loss were calculated independently for each sliding window and assigned to the center position of corresponding sliding window. The survival difference was examined between samples that had gained or lost a chromosomal region (sliding window) and samples that had not using the method of Kaplan-Meier and the statistical significance was assessed by the log-rank test. The sliding window was identified as gained or lost if P-value < 10 −4 and Q-value < 10[suo]-3. Sliding windows whose gains or losses led to poor survival with log-rank test p-value < 0.5, corresponding q-value < 0.5, and happened to ≥ 10% of all samples were retained. Several regions of genomic gains and losses were significantly associated with poorer survival with 5 deletion hotspots common between the 2 datasets (Table). We validated the prognostic significance of these survival critical loci using FISH in an independent dataset of 169 patients treated with high dose therapy. Clustering of these survival critical loci revealed clusters of MM characterized by low, intermediate or high number of these abnormalities, which are independent of ploidy and translocations subtypes. These subgroups have significantly different survival. In addition, the clustering analysis suggests the chromosome 13 loss is an early event whereas chromosome 1 abnormalities are late events. Our strategy therefore identified novel regions of genomic aberration that are important prognostically. However, it is likely that these regions are manifestation of genomically unstable tumors with complex abnormalities that have poorer prognosis. Chr Start End Length Cytoband 1 74,137,824 75,972,544 1,834,720 p31.1 1 62,433,123 84,792,809 22,359,686 p31.3 – p22.3 20 4,100,452 6,189,410 2,088,958 p13 – p12.3 20 6,717,170 13,142,205 6,425,035 p12.3 – p12.1 20 4,708,668 10,566,333 5,857,665 p13 – p12.2

Abstract Events mediating transformation from the pre-malignant MGUS to MM is largely unknown. Previous studies have highlighted RAS mutation as a progression event. However, this abnormality is present in only a small subset of patients. Global gene expression differences between MGUS and MM have been reported but provided little coherent biological insights. To define progression events, we examined the differences in gene expression profiles (GEP, Affymetrix U133A genechip) between 101 MM and 22 MGUS using a powerful functional genomic tool, Gene Set Enrichment Analysis (Subramanium et al PNAS 2005), that allow extraction of biological information based on enrichment of genes associated with a phenotype within gene-sets derived experimentally or extracted from database. We found that a predominant theme relating to MM progression is the over-expression of proliferation related genes in MM highlighted by the enrichment of cell cycle related gene-sets. Another common theme is the enrichment of gene-sets relating to MYC activation. Seven of eight gene-sets related to MYC activation in the database are significantly enriched (p-value <0.05 and false detection rate <0.05). Leading edge (enriched genes) analysis of enriched MYC-related and proliferation-related gene-sets revealed a core, overlapping signature of 8 genes specific to MYC and not proliferation. These genes are further verified as MYC transcriptional targets using Metacore, a network analysis tool. In addition, 7 of the 8 genes had been validated as MYC target genes by chromatin immunoprecipitation previously (www.myccancergene.org). We validated this signature in independent publicly available cell lines and mouse gene expression experiments where this signature is present in mammary epithelial cell lines engineered to over-express MYC but not E2F3, SRC and BCAT, and mouse embryonic fibroblast over-expressing MYC but not HER2 or with RB knocked-out. In addition, analysis of proliferation index in these datasets showed that there is dissociation of proliferation from this signature. This showed conclusively that our signature is MYC specific and not related to proliferation. Of interest, the signature is also present in cell lines with activating RAS mutation, which also have high expression of MYC, suggesting that MYC activation is a downstream effect of activated RAS signaling. Indeed, in our patient cohort, most patients with RAS mutation express this signature. When applied to 2 large GEP MM patient cohorts, this signature was not present in normal plasma cells, rarely present in MGUS, and present in a significant proportion of MM and almost all the human myeloma cell lines. When analyzed in the context of other B-cell malignancies, the signature is very strong in Burkitt’s lymphoma, present in most myeloma but absent in chronic lymphocytic leukemia, Waldenstrom Macroglobulinemia, and normal B-cells. Our analysis therefore suggests that MYC activation may be a unifying pathological event in MGUS to MM progression. As MYC translocations occur in only about 13% of newly diagnosed MM patients, activating RAS mutations and other trans-mechanisms may mediate MYC activation. Our recent demonstration that sporadic MYC activation in a mouse strain prone to monoclonal gammopathy led to MM development provides important functional proof.

Abstract The use of high-resolution aCGH allows for whole genome screening for copy number changes even in tumors that rarely produce metaphase spreads. The aim of this study was to characterize the aCGH findings in B-CLL, lung MALT lymphoma, Waldenström’s Macroglobulinemia (WM), Multiple Myeloma (MM) and human myeloma cell lines (HMCLs). This study includes 301 B-cell malignancy samples (19 B-CLL, 19 MALT, 20 WM, 48 HMCLs and 195 MM) and an additional 76 melanoma samples. We found MM to have the highest number of abnormalities per karyotype, with 15.8±7.5 (mean ± SD) and 20.6±17.0 in hyperdiploid (H) and non-hyperdiploid MM (NH), respectively. The remaining diseases have a significantly lower number of abnormalities: 5.5±4.5 in B-CLL, 3.5±1.96 in MALT and 4±3.5 in WM. Aneuploidy and biallelic deletions were rare events in these three diseases. B-CLL has two highly recurrent abnormalities involving 11q22-q23 (29%) and 13q14.3 (33%). A minimal deleted region (MDR) of ∼108Kb was identified at 11q comprising ACAT1, NPAT and ATM. In 13q, a 280Kb MDR was recognized, including TRIM13, KCNRG, mir-15a and mir-16. The subgroup of MALT patients with t(11;18) had very few abnormalities and the majority are a consequence of unbalanced translocations (MALT, BIRC2 and BIRC3 deletions). In the remaining MALT samples, trisomy 3 and 18q gain were the most common abnormalities (31% each). The 6q16.3-q26 deletion was the most common abnormality in WM (45%). In 4 of 9 patients with 6q deletion there was an associated 6p gain. The same observation was found in 2 of 3 patients with 8p loss and concomitant 8q gain. Interestingly, 6p and 8q gain were not identified in patients without 6q and 8p deletions. Deletion of 17p was the most common recurrent abnormality observed in our panel of B-cell cancers, being identified in MM, WM and B-CLL. In B-CLL and WM, small mono and biallelic deletions of the NF-kB negative regulators, TRAF3 and NFKBIA, were identified, suggesting a potential involvement of this pathway in the pathogenesis of these diseases. Hierarchical clustering of the aCGH data in MM identified 3 distinct groups, NH-MM, H-MM and MM with deletions of chromosome 13 and 14. Interestingly, MGUS and SMM were more commonly clustered with H-MM. Several sub-clusters were observed in the H-MM group, the most prominent being made up exclusively of patients from TC class D1. This cluster was characterized by the presence of trisomy 11 and 21. The 11q13 TC group clustered and was highly associated with 11q amplifications due to unbalanced t(11;14). The 6q deletion defined a cluster with WM, MM and Melanoma patient with that abnormality. In the case of B-CLL and MALT, the only identifiable clusters were observed in cases with 13q loss and trisomy 3, respectively. These results highlight both, the common and unique aCGH findings in several B-cell cancers. By hierarchical clustering, MM was significantly divergent from the rest of the B-cell diseases. Due to the limited number of abnormalities in B-CLL/MALT/WM, the clustering of these groups was exclusively based on the common abnormalities. The use of aCGH has refined the MDRs of 11q and 13q in B-CLL. Additionally, the identification of deletions affecting the NF-kB pathway in B-CLL and WM has prompted us to hypothesize on the importance of constitutive NF-κB activation in these diseases.

Abstract MM is characterized by widespread genomic instability. Two broad genetic subtypes of MM defined by ploidy exist. Hyperdiploid MM (H-MM) is characterized by trisomies of chromosome 3, 5, 7, 9, 11, 15, and 19, and generally lacked primary translocations involving the immunoglobulin heavy chain locus (IgH) whereas the non-hyperdiploid MM (NH-MM) is characterized by primary IgH translocations such as t(11;14), t(4;14) and t(14;16). Using high-density array comparative genomic hybridization (aCGH, Agilent 44K array), we catalogued the different aberrations on each chromosome arm and also the total number of aberrations per tumor (NAPT), as an indication of the degree of genomic instability, in a large cohort of 194 MM patients. Both H-MM and NH-MM have high number of genomic aberrations, 15.8±7.5 (mean ± standard deviation) versus 20.6±17.0 respective. NH-MM has significantly more genomic losses (11.8±11.0 versus 4.1±3.8), whereas H-MM has slightly more genomic gains (11.7±5.0 versus 8.8±9.0). Most of the abnormalities in NH-MM are structural abnormalities whereas they are mainly whole chromosome abnormalities in H-MM. Based on these abnormalities, we cluster the patients using hierarchical clustering. The 2 main branch of the resulting dendogram delineate hyperdiploid and non-hyperdiploid patients. Sub-clusters of each ploidy subtype are apparent. For H-MM, a cluster with mainly trisomies, including that of chromosome 21, and another cluster with additional deletions (13, 16q, and less trisomy 21 and trisomy 11) were apparent. For NH-MM, a group with 1q amplification and 13 deletion, which also tend to have loss of chromosome 4, 6q, 16q and 14, and another group with little abnormalities or just 6q loss, and chromosome 13 and 14 loss were identified. We identified some genetic difference between NH-MM and H-MM in additional to known difference such as the trisomies and chromosome 13 deletion. Loss of chromosome 4 (18% versus 0.9%, p<0.0001), loss of chromosome 14 (33% versus 16%, p=0.02) and loss of chromosome 22 (21% versus 4%, p=0.0008) are more common in NH-MM. Based on the distribution of NAPT, a cut-off of 20 abnormalities per tumor segregate the patients into 2 groups with significantly different survival. Those with greater NAPT have significantly shorter survival (median overall survival of 20 months versus 88 months, Log-rank p=0.006). There is no correlation between NAPT and ploidy or presence of chromosome 1 abnormalities suggesting that genomic complexity itself is associated with survival. Our study showed that both H-MM and NH-MM are genomically unstable although the pattern of abnormalities is distinct. In addition, based on clustering analysis, new pattern of genetic abnormalities are observed that allow further refinement of the ploidy subtypes. In addition, genomic complexity is also an important prognostic factor.

8095 Background: Multiple myeloma (MM) remains incurable and invariably relapses after initial therapy. There is no uniform approach to management of relapsed MM and is dictated by type of initial therapy and the response seen, and availability of new drugs. The outcomes associated with current approaches have not been systematically examined. Methods: We enrolled 383 patients (pts) with myeloma who had a documented relapse between Jan 2007 and June 2010, including 220 from Europe, 106 from Asia, and 31 from South America and 26 from North America. Time Zero (T0) was defined as date of treatment after first relapse. Results: Across the study, 61% were male and 49% were over 65 years at T0. ISS stage distribution at diagnosis included 26, 40 and 33% of patients in stages 1, 2 and 3, respectively. Among regimens used at first relapse; bortezomib (Btz) containing regimens were most common (54%), followed by lenalidomide (Len, 25%) and cyclophosphamide (21%). The overall response rate (>=PR) to first therapy after relapse was 58% including 14% with a CR. There was a progressive decrease in the response rates with successive regimen; 45%, 30% and 15% for regimens 2, 3 and 4 respectively. Len use was considerably lower in the Asian cohort, while Btz use was comparable across the regions. The median PFS from T0 was 13 mos and OS was 35 mos, for the entire cohort. The PFS to first salvage regimen was similar across the regions, while OS was shorter for the Asian and South American cohorts. In a univariate analysis, ISS stage 3, presence of cytogenetic abnormalities, history of plasma cell leukemia or extramedullary disease (EMD), bone marrow PC% > 33% and presence of renal insufficiency were all associated with a shorter PFS as well as shorter OS (P<=0.01). In a multivariate model, ISS stage 3 and presence of EMD were most associated with short OS. Conclusions: Median PFS for current second line regimens, typically containing Btz or Len appear to be 1 yr with an OS from first relapse of about 3 yrs. The OS from first relapse is nearly double that seen in a cohort of patients in first relapse prior to introduction of new drugs. Clear-cut regional differences can be seen in terms of patterns of drug use and likely reflect drug availability and healthcare costs.

17516 Background: The p53 tumor suppressor is commonly inactivated by mutations. Even in tumors without mutations, there are defects in the response to p53 activation. In MM, the prognostic significance of p53 mutation is unknown, while there has been no systematic study of p53 function. We seek to address these issues in this study. Methods: p53 mutation was studied by conformation sensitive gel electrophoresis with primers encompassing exons 1 to 10 followed by sequencing of DNA fragments with altered electrophoretic pattern in newly diagnosed MM patients entered into ECOG E9486 trial where patients were randomized to receive variations of melphalan-based conventional chemotherapy (VBMCP). Fisher’s exact tests were used to compare variables between patients. Kaplan-Meier survival curves were compared using the log-rank test. To investigate p53 function, we analyzed the expression of p53, and 3 of its transcriptional targets, APAF1, p21 and MDM2, in a separate cohort of 15 normal plasma cells (PC), 14 MGUS, 13 smoldering myeloma (SMM) and 101 MM (73 new and 28 relapsed) from the Mayo Clinic who had gene expression profiling performed on the Affymetrix U133A chip (Santa Clara, Ca). Results: Two hundred and sixty-eight patients had enough materials for study and were included in the analysis. The prevalence of p53 mutation was 3% (n = 9). Five of the 9 patients (56%, p = 0.001) with mutations also had p53 deletion (studied by fluorescent in-situ hybridization) resulting in bi-allelic loss of p53. Soft tissue plasmacytomas (37% v 7%, p = 0.018), and among the common translocations, t(4;14) and t(14;16) (50% v 18%) were more common in patients with p53 mutations. Despite similar response to treatment, those with p53 mutation had very short OS (16.7 v 41.4 months, p < 0.001). There was induction of p53 expression in MGUS and SMM with concurrent induction of APAF1, p21 and MDM2 whereas loss of this pattern was frequent in MM (45% in new MM and 60% in relapse MM compared to 15% in MGUS/SMM (p = 0.03)). Conclusions: p53 mutations are relatively rare in newly diagnosed MM patients but portend a short survival. However, functional abnormalities of p53 are prevalent and may be important in progression from MGUS/SMM to MM. [Table: see text]

8007 Background: We recently described mutations in multiple genes in MM patients that lead to the activation of the non- canonical NF-KB pathway. Among the mutated genes, TRAF3 is the most commonly affected, and is inactivated in about 20% of patients. In this study, we further defined the clinical significance of TRAF3 inactivation in MM. Methods: Deletion of TRAF3 was identified by array- based comparative genomic hybridization using Agilent Human Genome CGH 44k oligonucleotide array and confirmed by fluorescent in situ hybridization. Mutations were detected by sequencing. We use a TRAF3 gene expression cut-off (derived from 127 Mayo clinic patients) as a surrogate for TRAF3 inactivation to investigate its association with Translocations and Cyclin D genetic subtypes, response rates, and survival using 2 large gene expression dataset: UAMS dataset (559 newly diagnosed patients treated with Total therapy II and III) and Millenium datasets (213 relapsed patients entered into randomized study of bortezomib versus dexamethasone). Results: A normalized expression level of less than 0.6 identified all but three of the known TRAF3 inactivated cases in the Mayo dataset (p<0.0001). Using this cut-off, TRAF3 inactivated cases were enriched for t(4;14) (26%, p=0.00002) and rarely D1 (mostly hyperdiploid) (9%, p=9.6E-10) in all 3 datasets. TRAF3 inactivation did not affect survival of patients treated with transplant-based therapy (UAMS and Mayo dataset) but was strongly associated with bortezomib response (89% TRAF3 low versus 40% TRAF3 normal, p0.6 had similar PFS with the two treatment. Conclusion: Mutations resulting in TRAF3 inactivation are common, particularly in non-hyperdiploid MM, and predict for response to bortezomib and resistance to dexamethasone suggesting that inhibition of the non-canonical NF-KB pathway may be one of the principle mechanisms of action of proteasome inhibitors in MM. No significant financial relationships to disclose.

Abstract Introduction Maintenance therapy has been extensively explored as a strategy for prolonging the duration of disease control and potentially survival following ASCT. To date, only lenalidomide has been approved for this indication. However, lenalidomide maintenance is associated with the development of second primary malignancies and tolerability issues. PIs are a backbone of MM treatment, and bortezomib-based maintenance has shown promising activity post-ASCT, yet the benefit of PI-based maintenance has not been demonstrated in a phase 3 trial vs placebo. Moreover, the feasibility of bortezomib maintenance in routine clinical practice is limited due to tolerability and the need for regular parenteral administration. There is a need for an oral PI maintenance therapy that can be administered for a prolonged period, improve depth of response without cumulative or late-onset toxicity, and improve convenience for patients. Methods The phase 3, double-blind, placebo-controlled, multicenter TOURMALINE-MM3 study (NCT02181413) compared weekly ixazomib vs placebo maintenance in NDMM patients who had at least a partial response (≥PR) to induction therapy with a PI and/or immunomodulatory drug (IMiD) followed by single ASCT. Patients were randomized (3:2) to receive ixazomib or matched placebo on days 1, 8, and 15 of 28-day cycles for up to 2 years or until progressive disease (PD) or unacceptable toxicity. Randomization was stratified by induction regimen (PI without IMiD vs IMiD without PI vs PI+IMiD), pre-induction ISS stage (I vs II or III), and post-ASCT response (complete response [CR] or very good partial response [VGPR] vs PR). Patients were ineligible if they had received post-ASCT consolidation or tandem ASCT. The ixazomib dose was 3.0 mg during cycles 1-4, increasing to 4 mg from cycle 5 if tolerated during cycles 1-4. The primary endpoint was PFS per independent review committee (IRC), who were blinded to treatment assignment. The key secondary endpoint was OS. Here, we report data from the final analysis for PFS (data cut-off: April 16, 2018). Results 656 patients were randomized (395 ixazomib; 261 placebo). Patient demographics were balanced between groups; overall median age was 57 years (range, 24-73), 37% vs 63% had ISS I vs II or III, 59%/11%/30% had received PI without IMiD / IMiD without PI / PI+IMiD induction therapy, 34%/45%/21% had achieved CR / VGPR / PR following induction/ASCT, and 18% had high-risk cytogenetics [del(17p), t(4;14), or t(14;16)]. After a median follow-up of 31 months with 54% of PFS events, there was a 28% reduction in the risk of progression/death, corresponding to a 39% improvement in PFS with ixazomib vs placebo (median 26.5 vs 21.3 months; hazard ratio [HR] 0.72; 95% CI: 0.582, 0.890; p=0.002; Figure). In a landmark analysis from ASCT, PFS was 30.7 vs 24.9 months (HR 0.684; 95% CI: 0.551, 0.848; p<0.001). Median PFS2 and OS have not yet been reached in either arm. Ixazomib maintenance led to higher rates of deepened response compared with placebo (relative risk 1.41; 95% CI: 1.10, 1.80; p=0.004). Conversion from documented MRD positivity at study entry to MRD negativity occurred at a higher rate with ixazomib compared with placebo (12% vs 7%). PFS benefit was seen broadly across subgroups, including ISS III (HR 0.661), PI-exposed (HR 0.750), PI-naïve (HR 0.497), and patients with high-risk cytogenetics (HR 0.625). Discontinuation due to AEs was low (7% ixazomib vs 5% placebo). With ixazomib vs placebo, 42% vs 26% of patients had grade ≥3 AEs; 27% vs 20% had serious AEs; and 1 patient vs 0 died on treatment. Common grade ≥3 AEs were infections (15% vs 8%) including pneumonia (6% vs 4%), gastrointestinal disorders (6% vs 1%), neutropenia (5% vs 3%), and thrombocytopenia (5% vs <1%). Peripheral neuropathy rates were 19% vs 15% (<1% vs 0 grade 3). Rate of second primary malignancies was 3% in both arms. Global Quality of Life scores (EORTC QLQ-C30) on ixazomib were similar to placebo. Conclusions This study demonstrated a 28% reduction in the risk of progression/death, corresponding to a 39% improvement in PFS with ixazomib maintenance, with deepening of responses and increased conversions to MRD negativity over control, as well as a favorable safety profile, including an absence of risk of second primary malignancies and low rates of peripheral neuropathy, supporting ixazomib as a valuable option for maintenance therapy in responding patients post-ASCT. Figure. Figure. Disclosures Dimopoulos: Janssen: Honoraria; Takeda: Honoraria; Amgen: Honoraria; Celgene: Honoraria; Bristol-Myers Squibb: Honoraria. Gay:Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees; Janssen Takeda Celgene, Amgen, BMS, and Roche: Other: Advisor; Janssen, Amgen, Takeda, Celgene, BMS: Honoraria; Janssen: 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; Takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees; Abbvie: Consultancy; Bristol Myers Squibb: Honoraria, Membership on an entity's Board of Directors or advisory committees; Roche: Membership on an entity's Board of Directors or advisory committees. Schjesvold:Oncopeptides: Consultancy; Abbvie: Honoraria; Novartis: Honoraria; Janssen: Consultancy, Honoraria, Research Funding; Adaptive: Consultancy; Bayer: Consultancy; Bristol Myers Squibb: Consultancy; Takeda: Consultancy, Honoraria; Celgene: Consultancy, Honoraria; Amgen: Consultancy, Honoraria, Research Funding. Beksac:Bristol Myers Squibb: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Takeda: 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, Speakers Bureau; Novartis: 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, Speakers Bureau; Deva: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Hajek:Amgen: Consultancy, Honoraria, Research Funding; Bristol Myers Squibb: Consultancy, Honoraria; Takeda: Consultancy, Honoraria, Research Funding; Janssen: Consultancy, Honoraria, Research Funding; Celgene: Consultancy, Honoraria, Research Funding; Novartis: Research Funding. Weisel:Amgen, BMS, Celgene, Janssen, and Takeda: Honoraria; Amgen, BMS, Celgene, Janssen, Juno, Sanofi, and Takeda: Consultancy, Membership on an entity's Board of Directors or advisory committees; Amgen, Celgene, Janssen, and Sanofi: Research Funding. Goldschmidt:Novartis: Honoraria, Research Funding; Amgen: Consultancy, Research Funding; Adaptive Biotechnology: Consultancy; Sanofi: Consultancy, Research Funding; Takeda: Consultancy, Research Funding; Chugai: Honoraria, Research Funding; Bristol Myers Squibb: Consultancy, Honoraria, Research Funding; Celgene: Consultancy, Honoraria, Research Funding; Janssen: Consultancy, Honoraria, Research Funding; ArtTempi: Honoraria; Mundipharma: Research Funding. Maisnar: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; Amgen: Honoraria, Membership on an entity's Board of Directors or advisory committees; Bristol Myers Squibb: Membership on an entity's Board of Directors or advisory committees; Takeda: Membership on an entity's Board of Directors or advisory committees; Novartis: Honoraria. Moreau:Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees; Abbvie: 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; Takeda: 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. Chng:Merck: Research Funding; Takeda: Consultancy, Honoraria, Other: Travel, accommodation, expenses; Amgen: Consultancy, Honoraria, Other: Travel, accommodation, expenses; Aslan: Research Funding; Janssen: Consultancy, Honoraria, Other: Travel, accommodation, expenses, Research Funding; Celgene: Consultancy, Honoraria, Other: Travel, accommodation, expenses, Research Funding. Kaiser:Janssen: Consultancy, Honoraria; Takeda: Consultancy, Other: Travel Support; Bristol-Myers Squibb: Consultancy, Other: Travel support; Chugai: Consultancy, Honoraria, Research Funding; Amgen: Consultancy, Honoraria; Celgene: Consultancy, Honoraria, Research Funding. Zweegman:Takeda: Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene Corp.: Membership on an entity's Board of Directors or advisory committees, Research Funding; Takeda: Membership on an entity's Board of Directors or advisory committees, Research Funding; Janssen: Membership on an entity's Board of Directors or advisory committees, Research Funding. Mateos:Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; GSK: Consultancy, Membership on an entity's Board of Directors or advisory committees; Amgen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Abbvie: Consultancy, Membership on an entity's Board of Directors or advisory committees; Amgen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; GSK: Consultancy, Membership on an entity's Board of Directors or advisory committees; Takeda: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees. Spencer:Celgene: Honoraria, Research Funding, Speakers Bureau; Janssen-Cilag: Honoraria, Research Funding, Speakers Bureau; Amgen: Honoraria, Research Funding; BMS: Research Funding; Takeda: Honoraria, Research Funding, Speakers Bureau; STA: Honoraria. Iida:Janssen: Consultancy, Honoraria, Research Funding; Kyowa-Hakko Kirin: Research Funding; Bristol Myers Squibb: Honoraria, Research Funding; Astellas: Research Funding; Chugai: Research Funding; Novartis: Honoraria, Research Funding; Celgene: Honoraria, Research Funding; Ono: Consultancy, Honoraria, Research Funding; Takeda: Consultancy, Honoraria, Research Funding; Toyama Chemical: Research Funding; MSD: Research Funding; Gilead: Research Funding; Teijin Pharma: Research Funding; Sanofi: Consultancy. Morgan:Takeda: Consultancy, Honoraria; Celgene: Consultancy, Honoraria, Research Funding; Janssen: Research Funding; Bristol-Myers Squibb: Consultancy, Honoraria. Teng:Millennium Pharmaceuticals, Inc., Cambridge, MA, USA, a wholly owned subsidiary of Takeda Pharmaceutical Company Limited: Employment. Suryanarayan:Millennium Pharmaceuticals, Inc., Cambridge, MA, USA, a wholly owned subsidiary of Takeda Pharmaceutical Company Limited: Employment. Skacel:Millennium Pharmaceuticals, Inc., Cambridge, MA, USA, a wholly owned subsidiary of Takeda Pharmaceutical Company Limited: Employment; Department of Hematology, Charles University General Hospital, Prague, Czech Republic: Other: Affiliation. Dash:Takeda Pharmaceuticals International Co.: Employment. Labotka:Millennium Pharmaceuticals, Inc., Cambridge, MA, USA, a wholly owned subsidiary of Takeda Pharmaceutical Company Limited: Employment.