Stewart, Keith

Abstract Introduction Lenalidomide is an immunomodulatory drug (IMID) used to treat Multiple Myeloma (MM). Although a role for cereblon (CRBN)-mediated degradation of Ikaros proteins (IKZF1 and IKZF3) has been shown, the complete molecular and biochemical mechanisms responsible for lenalidomide-mediated anti-MM activity and/or resistance are undiscovered. Therefore, we aimed to analyze whether IMIDs (thalidomide, lenalidomide, and pomalidomide) are inducing oxidative stress in MM and what determines these drugs varying sensitivity and/or resistance. Methodology Amplex Red Assay has been performed to analyze IMIDs-mediated inhibition of H2O2 decomposition in both, in-vitro and in-vivo assays. Lentiviruses were prepared in 293T cells for CRBN, IgL-λ & IgL-k, and Bim knockdown experiment. Quantification of MM cellular anti-oxidative capacity for determining IMID sensitivity was standardized with H2O2-mediated oxidation of FADH2 and NAD(P)H. To measure apoptosis and gene expression analysis 106 cells were incubated with lenalidomide for 24 to 96 hours before they were examined by annexin-PI and FACS analysis. Gene and protein expression were measured by RT-PCR, western blot, and immunohistochemistry. Results We discovered that IMIDs inhibit peroxidase-mediated decomposition of H2O2 in both, in vitro horseradish peroxidase (HRP) assays and in human MM cell lines (HMCLs). Of the IMIDs analyzed, pomalidomide was the more potent inhibitor. H2O2 treatment effectively degraded IKZF1 and IKZF3 in HMCLs. To confirm the central role of CRBN in IKZF1 and IKZF3 degradation by H2O2-induced oxidative stress, we used CRBN knockdown OPM2 isogeneic cells and the CRBN-overexpressing OCIMY-5 cell line. We treated both sets of isogenic cell lines with lenalidomide and H2O2 for 3 hours, and we showed that H2O2 similarly mediates IKZF1 and IKZF3 degradation in a CRBN-dependent fashion. Next, we tested viability of CRBN present and absent cell lines with increasing concentrations of lenalidomide and H2O2 for 3 days. Lenalidomide-induced cytotoxicity was CRBN dependent, but H2O2 was not after 3 days, as shown by MTT assays. The capacity of MM cells to decompose H2O2 was measured via a biochemical test that quantitatively measured cellular anti-oxidative capacity. IMID sensitivity was well correlated with cellular anti-oxidative capacity, likely, cells more efficiently decompose H2O2was resistant and cells were not sensitive to IMID. This result shows that antioxidant capacity determines lenalidomide sensitivity among HMCLs with similar CRBN protein expression. We discovered that lenalidomide-mediated cytotoxicity in MM was attributable to oxidative damage of intracellular immunoglobulin proteins. By using several sets of isogenic cells lines with and without CRBN expression, we confirmed that lenalidomide treatment caused accumulation of IgL dimers only in CRBN-positive cells. Lenalidomide-induced IgL dimerization lead to decreased secretion and consequent intracellular accumulation of IgL, as evidenced by unchanged IgL mRNA expression, increased total intracellular IgL protein, and decreased secretion of IgL. After 72 hours of lenalidomide treatment we found decreased XBP-1u, increased XBP-1s, and over-expressed GRP78/BiP endoplasmic reticulum stress (ERS) marker proteins in CRBN positive cells but not in CRBN knock-down cells. We observed Bim requirement, especially BimEL, after lenalidomide treatment in CRBN-positive lenalidomide-sensitive cells. Our data reveals that lenalidomide-mediated; progressive ERS can positively enhance bortezomib-induced apoptosis in an in-vitro MM model. We pretreated MM cells with lenalidomide and then treated them with bortezomib. OPM2 cells pretreated with lenalidomide for 2 days clearly showed increased sensitivity to bortezomib-induced apoptosis compared with cells that were not pretreated. Conclusion IMIDs inhibit H2O2 decomposition. Ikaros protein degradation is a consequence of H2O2 mediated oxidative stress. Therefore, cells producing high H2O2 and with less antioxidative capacity are more sensitive to IMIDs. On the basis of this discovery, we would be able to predict which patients will benefit from IMIDs-mediated therapy and develop new drugs other than IMIDs that can inhibit intracellular H2O2 decomposition in MM. At present, CRBN may be required for IMIDs to effectively inhibit H2O2decomposition. Disclosures Chirackal: Mayo Clinic: Patents & Royalties: Filed a professional US patent for quantifying cellular anti-oxidative capacity. Fonseca:Mayo Clinic: Patents & Royalties: Filed a professional US patent for quantifying cellular anti-oxidative capacity.

Abstract Abstract 3803 Background: The MMRC is a non-profit, disease-focused consortium founded in 2004 comprised of 13 North American centers with expertise in multiple myeloma (MM). The MMRC Inc. (Norwalk, CT), MMRC's member institutions, and several pharmaceutical partners work closely to speed early development of new treatment options for MM patients. In December 2007, MMRC headquarters staff implemented multiple project management (PM) business solutions to address trial barriers that delay activation of our phase I-II clinical trials and established trial metric benchmarks considered attainable at our member institutions. In November 2009, we reported initial data1 on trial activation: MMRC trials initiated between Sep08-Jul09 (n=5) demonstrated a 38% decrease in mean time to first patient dosed (FPFD), compared with the Early Group trials (EG) initiated before PM solutions (Jun06-Sept08; n=7 trials). These results also confirmed improvement over published metrics from Dilts et al 2,3. We present additional data on time to FPFD and now enrollment, to assess impact of the MMRC PM resources and processes on trial efficiency. Methods: Twenty-one (21) trials conducted within the MMRC from May 2006 to June 2010 had sufficient trial data for review. Data were collected by MMRC-funded project managers at the clinical centers using a web-based clinical trial management system (CTMS). FPFD was defined as the time from the member institutions' receipt of the final protocol (FP) from the trial sponsor, to the time the first patient was dosed on the trial at any participating MMRC member institution. With respect to enrollment, pre-study enrollment commitment (EC) established between MMRC and the study sponsor was defined as the total number of subjects committed to receive at least one dose of study drug across all participating MMRC centers on a trial; baseline enrollment timeline (BET) was prospectively defined as the target time period to attain EC. Results: Mean time to FPFD was 181 calendar days for the early group trials (EG, n=7) and 122 days for the recent group (RG) trials (n=14, Sep08 – Jun10), representing a 32% reduction of time to FPFD in the RG. Additionally, time from final protocol to first patient dosed at all MMRC centers on a trial decreased 18% from a mean of 7.7 months (EG) to 6.3 months (RG). With respect to MMRC trial enrollment, data was available for 16/21 trials (5 EG and 11 RG). 2 EG trials were missing data and 3 RG trials were still enrolling as of June 2010. The mean MMRC pre-study EC was 39 subjects per trial (n=16 trials; 626 enrollment target); the mean actual MMRC enrollment was 49 subjects per trial (n=16; 783 enrolled through Jun 29, 2010) representing a 25% increase in actual versus committed enrollment. Two trials did not meet MMRC EC: MMRC investigators discontinued their involvement in these trials at approximately 30% target EC due to trial complexity or low patient enrollment. 14/16 evaluable trials (88%) met their EC; 11/16 trials met EC within BET (69%) of which 8/16 trials (50%) reached EC 34% faster than their BET (representing a mean reduction of 4.5 months). The overall pre-study mean BET for 16 trials was 13.1 months. MMRC's actual mean enrollment timeline was 11.3 months for the group of 14 evaluable trials representing improvement over the original BET by a mean of 1.9 months (14%). We believe FP to FPFD is a more meaningful metric beyond that of first patient consented. Moreover, we believe that if all participating trial centers focus their efforts on dosing the first patient and within a targeted timeframe, it may improve our research efforts overall. Conclusion: Development of drugs in the clinical setting has become time and resource intensive. Activating and enrolling trials promptly is a priority for drug development. The MMRC's standardization of processes and support for site-based PM resources results in improved trial metrics. MMRC member centers met or exceeded pre-specified enrollment targets in 88% of the trials analyzed to date. Ongoing monitoring of trial conduct continues to reveal areas where increased focus is needed to realize further trial efficiencies. These trial metrics and measures to improve efficiency may be applied with similar expected benefit in all oncology disciplines. Disclosures: Wear: Multiple Myeloma Research Consortium (MMRC): Employment. Richardson:Multiple Myeloma Research Consortium (MMRC): Member Institution of the MMRC; Millennium: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees; Johnson & Johnson: Membership on an entity's Board of Directors or advisory committees. Revta:Multiple Myeloma Research Consortium (MMRC): Member Institution of the MMRC. Vij:Multiple Myeloma Research Consortium (MMRC): Research Funding; Multiple Myeloma Research Consortium (MMRC): Member Institution of the MMRC. Fiala:Multiple Myeloma Research Consortium (MMRC): Member Institution of the MMRC. Lonial:Bristo-Myers Squibb: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene Corporation: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Millenium Pharmaceuticals Inc: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis Pharmaceuticals: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Onyx: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding. Francis:Multiple Myeloma Research Consortium (MMRC): Member Institution of the MMRC. Siegel:Multiple Myeloma Research Consortium (MMRC): Member Institution of the MMRC; Celgene: Speakers Bureau; Millennium: Speakers Bureau. Schramm:Multiple Myeloma Research Consortium (MMRC): Member Institution of the MMRC. Jakubowiak:Multiple Myeloma Research Consortium (MMRC): Member Institution of the MMRC, Research Funding; Millennium: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Celgene: Honoraria, Speakers Bureau; Centocor Ortho-Biotech: Honoraria, Speakers Bureau; Exelixis: Honoraria, Speakers Bureau; Bristol-Myers Squibb: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Harvey:Multiple Myeloma Research Consortium (MMRC): Member Institution of the MMRC. Reece:Multiple Myeloma Research Consortium (MMRC): Member Institution of the MMRC; Celgene: Honoraria, Research Funding; Ortho Biotech: Honoraria, Research Funding; Merck: Honoraria, Research Funding; Amgen: Honoraria, Research Funding; Facet: Research Funding; Otsuka: Honoraria, Research Funding. Gul:Multiple Myeloma Research Consortium (MMRC): Member Institution of the MMRC. Jagannath:Celgene: Honoraria; Millenium: Honoraria; Orthobiotec: Honoraria; Onyx Pharma: Honoraria; Merck: Honoraria; Proteolix: Honoraria; Multiple Myeloma Research Consortium (MMRC): Member Institution of the MMRC. La:Multiple Myeloma Research Consortium (MMRC): Member Institution of the MMRC. Hofmeister:Multiple Myeloma Research Consortium (MMRC): Member Institution of the MMRC. Jansak:Multiple Myeloma Research Consortium (MMRC): Member Institution of the MMRC. Stewart:Millennium: Consultancy; Celgene: Honoraria; Multiple Myeloma Research Consortium: Member Institution of the MMRC. Hagerty:Mayo Clinic: Employment; Multiple Myeloma Research Consortium (MMRC): Member Institution of the MMRC. Wolf:Multiple Myeloma Research Consortium (MMRC): Member Institution of the MMRC; Celgene: Speakers Bureau; Millennium: Speakers Bureau; Novartis: Speakers Bureau; Orthobiotech: Speakers Bureau. Davis:Multiple Myeloma Research Consortium (MMRC): Member Institution of the MMRC. Krishnan:Celgene: Speakers Bureau; Multiple Myeloma Research Consortium (MMRC): Member Institution of the MMRC. Duarte:Multiple Myeloma Research Consortium (MMRC): Member Institution of the MMRC. Zimmerman:Millennium, Celgene: Speakers Bureau. Cisneros:Multiple Myeloma Research Consortium (MMRC): Member Institution of the MMRC. Kumar:Celgene: Consultancy, Research Funding; Millennium: Research Funding; Merck: Consultancy, Research Funding; Novartis: Research Funding; Genzyme: Consultancy, Research Funding; Cephalon: Research Funding; Bayer: Research Funding; Multiple Myeloma Research Consortium: Member Institution of the MMRC. Birgin:Multiple Myeloma Research Consortium (MMRC): Member Institution of the MMRC. Ott:Multiple Myeloma Research Consortium (MMRC): Employment. Tasca:Multiple Myeloma Research Consortium (MMRC): Employment. Kelley:Multiple Myeloma Research Consortium (MMRC): Employment. Anderson:Millennium: Consultancy; Multiple Myeloma Research Consortium (MMRC): Member Institution of the MMRC; Celgene: Consultancy; Novartis: Consultancy; Onyx: Consultancy; Merck: Consultancy; Bristol-Myers Squibb: Consultancy; Acetylon: Equity Ownership, Membership on an entity's Board of Directors or advisory committees. Giusti:Multiple Myeloma Research Consortium (MMRC): Employment.

Abstract Background: Ixazomib is an experimental, orally bioavailable, proteasome inhibitor that has demonstrated anti-tumor activity in relapsed multiple myeloma (MM). In the dose escalation studies, ixazomib was tolerated up to a dose of 5.5 mg given every week as a single agent, while a dose of 4 mg was utilized in the combination studies with lenalidomide. We undertook this study to examine the efficacy and tolerability of the two doses of ixazomib in combination with dexamethasone in patients with relapsed MM. Patients and methods: This was a randomized phase 2 study of two doses of ixazomib (4mg; Arm A or 5.5 mg; Arm B) given weekly for three weeks with a week off along with weekly dexamethasone (40 mg) in patients with relapsed MM, who are proteasome inhibitor na•ve (including bortezomib) or have received less than 6 cycles of therapy with bortezomib and had a PR or better with no progression at the time of discontinuation. The primary objective was to determine the confirmed overall response rate (>=PR); secondary objectives included progression free and overall survival. A total of 71 patients were accrued from February 2013 to April 2015; one patient was ineligible. Results: Baseline characteristics were similar in the two arms; median age across the study was 70 years (46-84); 53% were male. Median number of prior therapies was 4 (range 2-6); 90% of the patients had prior IMiDs, 70% had prior transplant and 29% had prior bortezomib. At a median follow up of 10 months, 17 (49%) and 19 (54%) of patients had disease progression in arms A and B respectively with 12 (34%) patients in each arm still continuing on treatment. All patients in each arm were evaluable for response; the overall response rates were 31% in arm A (95%CI: 17-49) and 51% (95%CI: 34-69) in Arm B. The depth of response, event free survival and overall survival are outlined in Table 1. Among the patients with no prior bortezomib exposure the response rates were 38% for Arm A and 52% for Arm B. The treatment was well tolerated with 2 patients in each arm discontinuing treatment for adverse events; there were no on study deaths. A grade 3 or higher AE that was at least possibly related to treatment was seen in 21% and 54% in Arms A and B respectively; with 15% and 37% hematologic and 6% and 29% non-hematologic AEs. The most common attributable toxicities encountered included fatigue, thrombocytopenia, diarrhea and nausea with more grade 3 toxicities among Arm B. Peripheral neuropathy, possibly related to ixazomib, was seen in 55% (only grade 1 or 2) in arm A and 43% (2 patients with grade 3) in Arm B. Toxicities led to dose reduction of ixazomib in 17% and 43% of patients in Arm A and B respectively; the median number of cycles administered were 5 (1-24) and 5 (1-22) respectively. Conclusions: Ixazomib in combination with dexamethasone was well tolerated with significant anti-myeloma activity in this group of patients with relapsed MM. Deep responses including stringent CR were observed. The higher dose of ixazomib appears to be associated with a higher response rate but with higher rate of adverse events requiring dose reductions. Table 1. Treatment outcome in all patients Arm B (4 mg) (N=35) Arm C (5.5 mg) (N=35) Response Rate 31% (95%CI: 17-49) 51% (95%CI: 34-69) No. of Responders 11 18 sCR 0 1 CR 1 0 VGPR 7 8 PR 3 9 MR 5 1 Median Overall Survival1 NA NA 6 Months 100% 100% Median Event Free Survival1,2 8.4 mos (95%CI: 4.3-13.2) 8.2 mos (95%CI: 3.8-16.3) %Event Free at 6 Months 60% (95%CI: 45-81) 60% (95%CI: 45-81) Median Duration of Response1 16.7 mos (95%CI: 9.3-22.0) 16.3 mos (95%CI: 7.0-20.1) Median Time to Response 1.1 mos (range: 0.8-3.6) 1.0 mos (range: 0.8-7.5) CI: confidence interval; mo: month; NA: not attained 1Kaplan Meier 2Event-free survival time is defined as the time from registration to the first of disease progression, death due to any cause, or subsequent treatment for multiple myeloma. Disclosures Kumar: Celgene: Consultancy, Research Funding; Sanofi: Consultancy, Research Funding; Skyline: Consultancy, Honoraria; Onyx: Consultancy, Research Funding; Novartis: Research Funding; Janssen: Consultancy, Research Funding; Takeda: Consultancy, Research Funding; BMS: Consultancy.

Abstract Abstract 1923 Our understanding of the genetic abnormalities associated with the development of multiple myeloma has increased significantly in the last decade. However, very little is known about how, or if, myeloma tumor genomes change with time and if therapeutic interventions influence these events. To address these issues we studied a cohort of 29 patients for whom at least two serial samples (1-65 months, median 19 months) were available for analysis. Each serial pair was analyzed by both array-based comparative genomic hybridization (aCGH) and microarray gene expression profiling (GEP) to identify DNA copy number abnormalities (CNA) at a 25kb resolution and gene expression differences present in the bulk of the tumor mass. Though this does not address the intra-clonal heterogeneity that may exist at a given time point, it does answer if the bulk of the tumor mass is changing with time. This study has unearthed several surprising and clinically relevant findings. First, myeloma tumor genomes are not as unstable as previous cytogenetic analyses suggest. In 40% of patients we observed no detectable CNA changes (1-37 months, median 12 months). In 24% of patients we observed the exclusive acquisition of new CNA (1-12, median 3.5) (3-22 months, median 18 months). In 36% of patients we observed both the loss (1-20, median 3) and gain (1-33, median 21) of CNA (5-43 months, median 20 months). Because time was not a significant influence on the detection of stable or unstable genomes we compared CNA changes with TC class and found patients with the high-risk 4p16 and maf IgH translocations were over-represented in the latter subset of patients. These observations raise the question of what happens between multiple rounds of therapy and if different regimens influence these phenotypes differently. For two patients with no CNA changes between the first two time points there was an additional sample that extended the follow-up by 52 and 12 months. Again no CNA changes were seen between diagnosis and these final samples taken 63 and 50 months later. For one patient with CNA changes (5 shared, 29 lost, and 32 gained) we have a detailed time course of 5 samples from diagnosis through to end-stage plasma cell leukemia. This patient received continuous lenalidomide-dexamethasone (Rd) for 20 months and progessed with a clone containing a BIRC2/3 deletion, which activates the NFKB pathway. The patient received single agent PR-171 and a bortezomib containing regimen and unexpectedly, the tumor genome observed in the third sample was almost identical (32 shared, 2 lost, and 4 gained CNA) to the first time point, including two copies of BIRC2/3. Subsequently, the patient received melphalan-prednisone-bortezomib (MPV) and the tumor genome observed in the fourth and fifth samples, which were identical, were similar to that seen in the second sample (24 shared, 13 lost, and 39 gained CNA). To understand these observations better we performed FISH to ascertain if the observed clones were detectable earlier, albeit at a low frequency. These experiments proved that the two dominant subclones observed at time points 1 and 3 versus 2, 4, 5 were mutually exclusive at the single cell level. Moreover, both of these clones were detectable at diagnosis with 12% of the tumor mass being the second subclone that eventually evolved into plasma cell leukemia. Interestingly, we assayed 5 of the 39 unique CNA observed in the final two samples and only one, the 17p13 deletion, was detectable earlier. This suggests the MPV regimen effectively eliminated a clone that was previously sensitive to Rd and selected for a dramatically evolved subclone that was previously sensitive to two different proteasome inhibitors. Although it is clear that the high-risk patients are enriched in the subset with the most changes, it is not clear if the specific drugs used (Melphalan vs IMID vs proteasome inhibitor) or intervention strategy (Cycled vs continuous/maintenance) and perhaps the response achieved (PR vs CR) influences these events. These observations do highlight two important clinical concepts that need to be considered in the future. First, the meaning of a partial response needs further investigation as this may reflect effective elimination of one subclone but not another. Second, because some patients are not changing or can revert back to a previous subclone we need to consider re-chanllenging patients with previously effective regimens when patients progress. Disclosures: Fonseca: Genzyme: Consultancy; Medtronic: Consultancy; BMS: Consultancy; AMGEN: Consultancy; Otsuka: Consultancy; Celgene: Consultancy, Research Funding; Intellikine: Consultancy; Cylene: Research Funding; Onyx: Research Funding; FISH probes prognostication in myeloma: Patents & Royalties. Stewart:Millennium: Consultancy; Celgene: Honoraria. Bergsagel:Amgen: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees; Genentech: Membership on an entity's Board of Directors or advisory committees; Millennium: Speakers Bureau; Novartis: Speakers Bureau.

Abstract Background: Malignant cells alter metabolism in order to enable their highly anabolic state. In addition to a massive increase in glycolysis, malignant cells frequently become dependent on glutamine to feed the TCA cycle and provide key building blocks for cell growth and proliferation. CB-839 is a first-in-class potent and selective inhibitor of glutaminase (GLS), the first step in glutamine metabolism, that has broad in vitro and in vivo anti-tumor activity in solid and heme malignancies, including multiple myeloma. GLS inhibition with CB-839 induces apoptosis and/or growth arrest in multiple myeloma and lymphoma cell lines and is synergistic with pomalidomide and lenalidomide in vitro and as well as in multiple myeloma xenograft models in vivo. Methods: CX-839-002 is an ongoing Ph1 evaluation of escalating doses of CB-839 in patients with relapsed/refractory multiple myeloma (MM) or non-Hodgkins lymphoma (NHL) with the primary objective of assessing the safety profile and selecting a recommended Phase 2 dose (RP2D). Pharmacokinetics (PK) was monitored on Days 1 and 15. Initially, CB-839 was given three times daily (TID) without food, but based on PK and safety data generated across three Ph1 studies in patients with solid and heme malignancies, the drug is now being given twice daily (BID) with meals. Results: Safety data are available for a total of 14 patients (9 MM, 4 follicular lymphoma, 1 diffuse large B cell lymphoma) that have enrolled to date during the dose escalation (100-400 mg TID and 600 mg BID). The patients have received a median of 7 prior lines of systemic therapy. CB-839 has been well tolerated with only three subjects experiencing a Gr3/4 AEs considered possibly related to study drug and there have been no discontinuations due to AEs. A similar tolerability profile has been observed across three Ph1 studies for CB-839. With a total of 119 pts treated with CB-839 across the three studies, Gr3/4 drug-related AEs have occurred in 16 subjects (13%) and 4.3% of discontinuations were due to AEs. Reversible, asymptomatic elevations in transaminases have been the primary Gr3 AEs, occurring primarily on the TID schedule in 6/59 (10.2%) pts; only one occurred among 60 pts (1.7%) receiving the BID regimen. BID dosing with 600 mg was determined to be the RP2D and combination studies with pomalidomide and dexamethasone have been initiated. The half-life of CB-839 is ~4 hr, exposure increases with dose, and trough concentrations generally remain above the target threshold of 200 ng/mL for patients receiving the RP2D. Six of 8 MM pts that received ≥ 400 mg TID achieved steady state (D15) trough concentrations above the PK target threshold while 0 of 5 pts that received ≤ 250 mg TID achieved the PK threshold. Pharmacodynamic assessment of GLS activity in MM patients was consistent with a broader PK/PD assessment (across all 3 Ph1 studies), which established clear exposure-dependent inhibition of the target in peripheral blood platelets 4 hr after the first dose of CB-839, with >90% inhibition being maintained for most patients at the RP2D. Preliminary efficacy data include confirmed stable disease in 4 of 9 evaluable MM patients. Updated efficacy data and correlative studies on clinical samples will also be presented. The first pt treated with the combination of CB-839 and pomalidomide/dexamethasone (Pd) during dose escalation received 400 mg CB-839 BID, pomalidomide at 4 mg/day (D1-21) and dexamethasone at 40 mg on Days 1, 8, 15 and 22 of each 28-day cycle. This pt had a 71% decreased in urine M-protein and an 83% reduction in serum free light chain after the first 2 cycles of treatment. This pt had 11 prior lines of therapy but not pomalidomide and had two stem cell transplants and was progressing rapidly prior to study entry. The pt has tolerated the combination well and is continuing on study. Conclusions: CB-839 has been well tolerated at and above doses that produced robust inhibition of GLS in blood platelets and in tumors. Dosing BID with food has improved the PK profile and mitigated the frequency and severity of LFT elevations, which was the primary safety signal using TID dosing. Strong preclinical combination data, an excellent clinical safety profile, and initial data with CB-839 combined with Pd provide a strong rationale for continued development of CB-839 this combination in pts with relapsed/refractory multiple myeloma. Disclosures Vogl: Constellation Pharmaceuticals: Research Funding; Calithera Biosciences: Research Funding; Celgene Corporation: Consultancy; Acetylon Pharmaceuticals, Inc.: Research Funding; Millennium Pharmaceuticals: Research Funding; GSK: Research Funding. Younes:Celgene: Honoraria; Curis: Research Funding; Sanofi-Aventis: Honoraria; Seattle Genetics: Honoraria, Research Funding; Novartis: Research Funding; Janssen: Honoraria; Takeda Millenium: Honoraria; Bristol Meyer Squibb: Honoraria; Bayer: Honoraria; Incyte: Honoraria; Johnson and Johnson: Research Funding. Orford:Calithera Biosciences: Employment, Equity Ownership. Bennett:Calithera Biosciences: Employment, Equity Ownership. Siegel:Celgene Corporation: Consultancy, Speakers Bureau; Amgen: Speakers Bureau; Takeda: Speakers Bureau; Novartis: Speakers Bureau; Merck: Speakers Bureau. Berdeja:Curis: Research Funding; Acetylon: Research Funding; Novartis: Research Funding; Janssen: Research Funding; Takeda: Research Funding; BMS: Research Funding; Array: Research Funding; MEI: Research Funding; Abbvie: Research Funding; Celgene: Research Funding; Onyx: Research Funding.

Abstract Introduction: In multiple myeloma, randomized trials of maintenance therapy using thalidomide or lenalidomide following autologous transplant (ASCT) demonstrated prolonged progression-free survival (PFS), but overall survival benefit was inconsistent. The MY.10 trial (n=332) demonstrated improved PFS with thalidomide-prednisone maintenance therapy, but quality of life was inferior and overall survival was not improved. As a randomized trial with a no-treatment control arm and biospecimen collection, MY.10 provides a unique opportunity to identify predictors of benefit from therapy that could be used to personalize treatment. Immunomodulatory drug action is mediated in part through binding to cereblon (CRBN) and downregulation of IRF4. Candidate single nucleotide polymorphisms (SNPs) were selected from the CRBN/IRF4 pathway and other genes previously associated with myeloma prognosis, drug response and toxicity from literature review. The aim of this study was to investigate associations between candidate SNPs and benefit from immunomodulatory compound-based maintenance therapy, as well as prognostic impact. Methods: Genomic DNA was extracted from samples preserved in Trizol¨. SNPs were genotyped using TaqMan¨ genotyping assays on the ViiA7 qPCR platform. Analysis was performed on 187 patients with available samples and clinical data (86 in treatment arm; 101 in observation arm). Cox regression models were performed using SAS clinical 2.0 for prognostic impact of a single SNP on PFS, assessed with and without adjusted covariates (age, stage, performance status and response to ASCT). In treatment benefit analysis, PFS was modeled with genotype, treatment assignment and their interaction term. Results: SNPs with significant prognostic impact for PFS in all 187 patients were found in CRBN (rs1672753) (HR 0.59, 95%CI 0.4-0.86; p=0.006) and the following SNPs which had been found to be prognostic in prior studies were validated: CYP1A1 (rs1048943) (HR 1.98, 95%CI 1.19-3.27; p=0.008), CYP1B1 (rs1056836) (HR 0.72, 95%CI 0.52-0.99; p=0.043), and trend toward significance for SNP in CYP1A2 (rs2069514) (HR 2.02, 95%CI 0.98-4.15; p=0.057). Of these, only the CYP1A1 SNP was found to be possibly predictive of greater benefit from maintenance therapy. A SNP in ABCA1 (rs363717), previously associated with thalidomide-induced neuropathy,‎ was prognostic in this study (HR 1.44, 95%CI 1.03-2.02; p=0.033) but not predictive of treatment benefit. Table 1 lists SNPs associated with a differential level of benefit from maintenance therapy, including SNPs in FAM179a and ICAM1 that were possibly associated with harm from maintenance therapy. Table 1. SNPs and treatment interaction with significant impact on PFS. HR represent hazard ratio of treatment versus observation for a given genotype group. Asterisk Indicates trend toward significance. Wildtype Heterozygote & mutant p-value interaction Gene dbSNP ID SNP HR 95% CI HR 95% CI FAM179A rs1053667 T>C 0.46 0.33, 0.66 2.28 0.78, 6.65 0.003 ICAM1 rs1799969 G>A 0.51 0.36, 0.73 1.75 0.83, 3.70 0.007 CASP3 rs1049216 A>G 0.82 0.54, 1.25 0.41 0.25, 0.69 0.029 IRF4 rs12203592 C>T 0.69 0.47, 1.02 0.38 0.21, 0.69 0.062* CYP1A1 rs1048943 A>G 0.62 0.44, 0.87 0.11 0.02, 0.52 0.079* Conclusion: Previously identified SNPs in drug metabolism and drug efflux genes were validated to be prognostic in this cohort. The prognostic but not predictive significance of a SNP in CRBN suggests a possible role for CRBN in multiple myeloma disease biology independent of immunomodulatory therapy. SNPs predictive of differing degrees of benefit from immunomodulatory maintenance were found in genes involved in immunomodulatory activation, drug action and cell adhesion mediated drug resistance; SNPs in FAM179A and ICAM1 were possibly associated with harm from thalidomide maintenance and could potentially be used to identify patients unsuitable for immunomodulatory maintenance therapy. These results may be applicable to lenalidomide and pomalidomide, since immunomodulatory compounds exhibit similar chemical structures and mechanisms of action. Validation of these SNPs in prospective clinical trials involving other immunomodulatory can test this hypothesis. Further studies are needed to confirm our findings. Disclosures Off Label Use: thalidomide and prednisone maintenance for multiple myeloma. Bahlis:Celgene: Consultancy, Honoraria, Research Funding, Speakers Bureau; Amgen: Consultancy; Johnson & Johnson: Speakers Bureau; Johnson & Johnson: Consultancy; Johnson & Johnson: Research Funding. Song:Celgene Canada: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding. White:Celgene Canada: Honoraria, Research Funding. Chen:Celgene: Consultancy, Honoraria, Research Funding. Seftel:Celgene: Honoraria, Research Funding. Howsen-Jan:Celgene: Honoraria, Research Funding. Reece:Amgen: Honoraria; Bristol-Myers Squibb: Research Funding; Merck: Research Funding; Novartis: Honoraria, Research Funding; Onyx: Consultancy; Millennium Takeda: Research Funding; Lundbeck: Honoraria; Otsuka: Research Funding; Janssen-Cilag: Consultancy, Honoraria, Research Funding; Celgene: Consultancy, Honoraria, Research Funding. Shepherd:Celgene: Honoraria, Research Funding. Chen:Celgene: Honoraria, Research Funding. Djurfeldt:Celgene: Research Funding. Reiman:Soricimed Biopharma Inc: Consultancy, Other: Scientific Advisory Board for Soricimed.

Abstract Abstract 2403 Immunoglobulin light chain amyloidosis (AL) is a monoclonal plasma cell disorder characterized by the accumulation of monoclonal light chain fragments that have undergone a conformational transformation and deposit as amyloid fibrils in different tissues. High-dose melphalan (HDM) with autologous hematopoietic stem-cell transplant (ASCT) is increasingly used to treat patients (pts) with AL Amyloidosis. However, transplant-related mortality (TRM) is high, ranging between 13% to 43%. The survival benefit of HDM has been attributed to a patient-selection bias. Recently, a randomized clinical trial by Jaccard A et al, showed longer survival in the group assigned to receive melphalan plus dexamethasone (Mel/Dex) than in the group assigned to receive HDM. The present is a retrospective study aiming to define which pts with AL are most likely to benefit from HDM. Patients and Methods We retrospectively reviewed the medical records of all the pts included in the Princess Margaret Hospital Amyloidosis Database who underwent ASCT from January 2004 to March 2010 to determine: a) TRM, b) Hematological response (HR) and Organ response (OR) and c) Overall survival (OS). We included transplanted pts who had received no more than two previous courses of any chemotherapy regimen who did not have concurrent myeloma, and who had an Eastern Cooperative Oncology Group (ECOG) performance-status score of 2 or better. As part of the ASCT the stem cells were obtained from the peripheral blood with granulocyte colony-stimulating factor (G-CSF) alone (5 μ g/kg subcutaneously, twice daily). Pts then received HDM, 200 mg/m2 given intravenously on day 0, and stem cells were infused on day 1. The HDM was reduced to 140 mg/m2 for pts 65 years of age or older and for those with an important decrease of the ejection fraction, a calculated creatinine clearance of less than 30 ml per minute, or severe liver disease. HR and OR was assessed using 2004 Amyloidosis Consensus Response Criteria (Gertz, M et al, 2004). For statistical evaluation, HR was defined as observing complete or partial remission (CR or PR); stable disease (SD) or progression was considered as no HR. All statistical tests were 2-sided X2 t test and P values less than .05 were considered to be statistically significant. Results Seventy seven pts were evaluated with a median age of 56 years (33-74). Clinical characteristics are seen in Table 1. Only 18/77 pts (23%) received induction therapy: Dexamethasone alone n=9, Cyclophosphamide and Prednisone n=2, Mel/Dex n=4, VAD n=2 and Melphalan and Prednisone n=1. TRM observed was 12% mainly due to congestive heart failure and sepsis. Complete HR was achieved in 38 cases (49%) and OR was seen in 59%. Among the most common complications to ASCT, febrile neutropenia was reported in 67%, transient renal impairment in 10% and congestive heart failure in 3%. Median OS was significantly lower for patients with B-type natriuretic peptide (BNP) >300 pg/ml (17.7 vs 64.46 months) (p0.0004), Troponin I >0.07 ng/ml (19.25 vs 97.4 months) (p0.00001) and those who achieved a complete HR (115 vs 88 months) (p0.0345). Multivariate Cox regression analysis showed that BNP>300 pg/ml and Troponin I >0.07 ng/ml (normal <0.07) were the most important factors to predict OS for patients with AL who underwent ASCT (p0.0002 and 0.04 respectively). Conclusions Based on this study of 77 patients, clinical selection is the most important factor to better improve outcomes for HDM in AL. Patients with BNP>300 pg/ml and/or abnormal levels of Troponin I (>0.07) should not be considered eligible for transplants due to a high degree of mortality. Our series showed a CR rate of 49% which is higher than 33% reported by Palladini et al with Mel/Dex. Stringent case selection may be the most important factor in decreasing mortality rate associated to ASCT leading to better outcomes. Table 1. Clinical Characteristics of patients with AL Amyloidosis undergoing ASCT (at initial diagnosis) Clinical Characteristics N Median Range % Age (years) 77 57 33–74 Hemoglobin (g/L) 77 138 104–182 Creatinine (μ mol/L) 77 129 37–700 **BNP (pg/ml) 44 180 10–1670 ***BMPC (%)– 77 7 1–30 24 Hr Proteinuria (g/d) 77 5.5 0–24.9 Intraventricular Septal Distance (mm) 77 13 9–23 Kappa/lambda ratio 53 4.4 0.001–71.2 Kidney Involvement 71 Heart Involvement 52 Liver involvement 23 GI involvement 10 3 or more organs involved by AL 16 ** B-Type Natriuretic Peptide *** BMPC: Bone marrow plasma cells Disclosures: Stewart: Millennium: Consultancy; Celgene: Honoraria. Reece: Celgene: Honoraria, Research Funding. Chen: Celgene Corporation: Consultancy, Honoraria, Research Funding. Kukreti: Celgene: Honoraria.

Abstract Multiple myeloma tumors universally target one of the three human cyclin D genes (CCND1, CCND2 or CCND3) for dysregulation (Bergsagel et al., 2005, Blood, 106:296). Using a lentivirus expressing CCND2 RNAi we first tested the effects of selective cyclin D2 knock down on My5 and H929 myeloma cell lines and found G0/G1 phase arrest, increased apoptosis and significant selective disadvantage in transfected cells. By comparison, knockout mouse models indicate that most somatic tissues can develop in the total absence of cyclin D1, D2 and D3 (Kozar et al., 2004, Cell,118:477). Targeted inhibition of specific cyclin D expression is therefore a rational therapeutic strategy in myeloma. To identify novel pharmaceutical inhibitors of CCND2 transactivation we developed an assay employing NIH 3T3 cells stably co-expressing the CCND2 transactivator c-Maf and the cyclin D2 promoter driving firefly luciferase (luc) and screened the Lopac (n=1280), Prestwick (n=1120) and Spectrum (n=2000) libraries of drugs and natural compounds. In a parallel MTS assay, the effect of each compound on 3T3 viability was determined, allowing exclusion of compounds that caused secondary suppression of CCND2 due to non-specific cytotoxicity. From the screen we identified 10 c-Maf independent putative CCND2 inhibitors. These included monensin, patulin, β-lapachone, camptothecin, dihydrogambogic acid, gentian violet, thapsigargin, brefeldin A, pristimerin and kinetin riboside. Three of the 10 compounds (gentian violet, thapsigargin and patulin) were not studied further due to toxicity cited in the literature. Subsequent validation studies using selected compounds in human myeloma cell lines (HMCL) confirmed successful suppression of both cyclin D2 and D1 proteins. Each of these compounds was then shown to be cytotoxic to a genetically diverse and standardized panel of 14 HMCL in MTT assays: monensin (10–760 nM), camptothecin (5–700nM), dihydrogambogic acid (250–800 nM), pristimerin (150–500 nM) and kinetin riboside (2.5–20μM). Cell cycle analysis confirmed induction of G0/G1 phase arrest for most compounds, consistent with cyclin D inhibition. However, camptothecin and b-lapachone induced S-phase arrest, suggesting secondary suppression of cyclin D by virtue of S-phase activity. Unsorted myeloma patient bone marrow samples demonstrated selective activity for pristimerin, dihydrogambogic acid and kinetin riboside against CD138+ myeloma cells compared with non malignant hematopoietic cells; by contrast monensin showed almost equal toxicity for normal cells. The triterpenoid, pristimerin, showed potent anti-myeloma activity and was examined in greater detail. Studies confirm that pristimerin rapidly inhibits cyclin D1, D2 and D3 expression (<6 hours) at nanomolar concentrations and induces apoptosis of primary myeloma cells characterized by caspase 9 cleavage and Annexin V binding. While pristimerin is cytotoxic to HMCL and patient myeloma cells at 0.1–0.15 mg/L, toxicity studies in vivo indicate that the drug is tolerated in mice at 2.5 mg/kg i.p. daily. In vivo activity against a xenograft model is currently being determined. Overall this targeted chemical biology screen has identified several compounds, including the triterpenoid, pristimerin, that are being further characterized for promising preclinical anti-myeloma activity.

Abstract INTRODUCTION: PR-171 is a novel, irreversible proteasome inhibitor under investigation for the treatment of hematological malignancies. In preclinical studies, PR-171 was well tolerated in rats and monkeys when given daily × 5 (QDx5), every two weeks. Proteasome inhibition determined in blood and other tissues one hour after dosing at the maximum tolerated dose (MTD) was >80%. Despite the irreversible mechanism of action, the half-life of recovery of proteasome inhibition in tissues was approximately 24 hours. PR-171 was effective in suppression of tumor growth in xenograft studies in mice when administered QDx2 every week for three weeks. Two phase I dose-escalation studies have been initiated, aimed at determining the safety, tolerability, and clinical response to PR-171. METHODS: Two different dose-intensive schedules were employed in these phase I studies. In PX-171-001, PR-171 was administered on a two week cycle, QDx5 with nine days rest, while in PX-171-002, PR-171 was administered on a four week cycle, QDx2 weekly for three weeks with 12 days rest. The objective of these studies was to evaluate the safety and effectiveness of single-agent PR-171 administered according to a modified Fibonacci dose escalation scheme in cohorts of three. Patients with multiple myeloma (MM), non-Hodgkin Lymphoma (NHL), Hodgkin disease, or Waldenstrom’s Macroglobulinemia who received two or more prior treatments were eligible. RESULTS: Both studies were initiated with a dose of 1.2 mg/m2. Thus far, a total of 15 and 23 subjects have been enrolled in PX-171–001 and -002, respectively. PR-171 has been well tolerated at the highest doses thus far, 8.4 and 15 mg/m2, respectively. Proteasome inhibition in whole blood at the highest dose levels exceeded 75%, and in peripheral blood mononuclear cells inhibition exceeded 65%, one hour after the first dose. There have been no dose-limiting toxicities, no adverse events (AEs) considered probably related to study medication, no dose-related increases in the incidence or severity of AEs, and no incidence of painful peripheral neuropathy on either study. Although the MTD has not yet been identified on either study, preliminary evidence of efficacy has been observed with reduction in myeloma paraprotein levels and symptomatic improvement in patients on both protocols. Eleven subjects remain on study with stable disease (SD), which has been observed in MM and NHL patients on both studies, lasting up to eight months. CONCLUSION: PR-171 is well-tolerated in relapsed and refractory MM and NHL patients at proteasome inhibition levels of more than 75%. Several subjects have achieved long-lasting SD, reduction in paraprotein levels or symptomatic improvement. Further data from these ongoing trials will be discussed at the meeting.

Abstract The search for novel and clinically effective anti-myeloma therapies has been hampered by a paucity of good pre-clinical animal models. Most established animal models of multiple myeloma (MM) fail in one or more crucial features to resemble human MM, frequently exhibiting extramedullary tumors or lacking a competent immune system. In addition, competing models are either too expensive or time consuming to generate and maintain. Finally, no model has been shown to reliably predict both drug response and drug inactivity. We have previously described a C57Bl6/J transgenic mouse model in which the expression of the human c-myc oncogene is activated in post-germinal B cells by somatic hypermutation. These mice (Vk*myc) spontaneously develop monoclonal gammopathies and plasma cell expansion beginning at 20 weeks of age. However, in contrast to other models, their plasma cells cannot be found in secondary lymphoid tissues. Now, we report that this model closely reproduces the clinical behavior of human MM. Serum protein electrophoresis (SPEP) as well as ELISA for serum IgG demonstrate that the incidence and quantity of monoclonal paraproteinemia are greatly elevated in the Vk*myc mice as compared to age matched wild type C57Bl6/J controls (50 weeks mean IgG 1.92g/dL Vk*myc vs 0.2g/dL controls; peak IgG levels up to 7.5g/dL). As these mice age, their paraproteins continue rising and remain far higher than that of controls at every time point. Mice with significant paraproteinemia demonstrate marrow with up to 50% plasma cells with evidence of a low proliferative index, similar to what is observed in human MM and unlike what is seen in other models of MM. Anemia is observed, with a mean hemoglobin of 8.9g/dL in the Vk*myc mice vs 13.4g/dL in the wild type. Vk*myc mice analyzed show marked bone thinning with a 20% reduction in total bone volume and in the number of trabeculae per unit area as shown by microCT. In addition a 15% reduction in bone mineral density was demonstrated in affected mice. We next demonstrated the efficacy of 3 drugs, used commonly in clinical practice to treat myeloma (melphalan, dexamethasone and bortezomib). These were given as single courses of daily IP injections for 5 days, for the first two drugs, and bi-weekly IP for 4 weeks for the third. As early as two weeks post treatment, a statistically significant reduction in serum paraprotein levels was observed in the treated mice versus vehicle treated controls. The reductions were maximal at 21d post treatment in the melphalan (−77.2%±39 p<0.02) and dexamethasone (−67.4%±29 p<0.02) groups and at 28d in the bortezomib group (−68.9%±9 p<.001). No reduction was seen in the vehicle treated controls at any time point. As with human myeloma, the effect of one course of treatment was transient in nature. In contrast, treatment of VK*myc mice with 3 drugs that have not shown clinical activity against myeloma as single agents (hydroxyurea, vincristine and fludarabine) did not reduce serum monoclonal proteins. We conclude that our Vk*myc model closely reproduces the clinical characteristics of human MM. We have also shown that this model responds to drugs known to be clinically active, while showing no response to drugs that have little or no effect against human MM. To our knowledge, this is the first time that this level of fidelity to human MM has been demonstrated in a pre-clinical animal model. Our model therefore represents a unique and powerful tool for pre-clinical anti-myeloma drug development.