Bergsagel, P. Leif

Abstract Abstract 201 Background: Pomalidomide at doses of 2 or 4 mg/d has demonstrated excellent activity in patients with relapsed multiple myeloma (MM). Between November 2007 and March 2012, we opened 6 sequential phase 2 trials and treated 345 patients with relapsed MM with pomalidomide at differing doses with weekly dexamethasone (Pom/dex). Results of 164 of these patients have been previously published. Here we describe long term follow up of these patients as well as results of an additional 181 patients with relapsed MM treated with the Pom/dex regimen. Methods: The six cohorts consisted of: Cohort 1 (N=60): relapsed MM with 1–3 prior regimens, 2 mg dose; Cohort 2 (N=34): lenalidomide (LEN) refractory, 2 mg dose; Cohort 3 (N=35): BZ)/LEN refractory, 2 mg dose; Cohort 4 (N=35): BZ/LEN refractory, 4 mg dose; Cohort 5 (N=60) LEN refractory, 1–3 prior regimens, 4 mg dose; and Cohort 6 (N=120) LEN refractory, 4 mg dose. Pomalidomide was given orally 2 mg daily or 4mg daily on days 1–28(cohorts 1–5) or 1–21 (cohort 6) of a 28-day cycle with oral dexamethasone given 40 mg daily on days 1, 8, 15 and 22. Response was assessed by the International Myeloma Working Group Uniform Response criteria. All patients received aspirin 325 mg daily for deep venous thrombosis (VTE) prophylaxis or full dose anticoagulation. Results: A total of 345 patients were enrolled across all 6 cohorts. One patient was ineligible and excluded from analysis. The median age was 64 years (32–88). The median time since diagnosis was 53 months. The median number of prior therapies was 3 (1–14). 147 (44%) had high-risk molecular markers by mSMART criteria. Prior therapies consisted of thalidomide 52%, lenalidomide 87%, bortezomib 75%, autologous stem cell transplant 70% and allogeneic transplant 3%. The median follow-up is 10.4 months (5.4–34 months). Sixty-seven percent are alive and 32% remain progression free. 46 patients are continuing to receive treatment. The most common toxicities (grade 3 or higher) were neutropenia (31%), anemia (16%), thrombocytopenia (12%), pneumonia (8%) and fatigue (8%). VTE was seen in 10 patients (3%). Outcomes are shown in Table 1. Across all 6 cohorts confirmed responses of partial response (PR) or better were seen in 34%. The response rate in all patients with mSMART high risk status was 30.6%. Responses and duration of response (DOR) in those with high risk molecular markers include: 17p– 19 of 56 (34%) DOR 8.2 months; t(4;14) 6 of 24 (25%) and DOR 4.8 months; t(14;16) 7 of 11(64%) and DOR 9.5 months; deletion 13 by cytogenetics 13 of 37 (35%) with DOR 8.2 months. In a multivariate analysis, only LDH > ULN, number of prior regimens, and prior BZ therapy were predictive of a shorter TTP and factors associated with a poor OS following initiation of pomalidomide therapy included B2M > 5.5, LDH > ULN,number of prior regimens, and prior BZ therapy. Conclusions: Pom/dex is active and well tolerated even in heavily pretreated patients and those with high risk molecular markers. Remissions are durable. Response rates and toxicity are similar between the 2 mg and 4 mg doses. Disclosures: Lacy: Celgene: Research Funding. Stewart:Celgene: Consultancy, Honoraria. Reeder:Celgene: Mayo Clinic receives funding from Celgene to support clinical trials Other, Research Funding.

Abstract Abstract 724 Background: Chromosome content identifies two pathogenic pathways, each occurring in about half of patients with MGUS and multiple myeloma (MM). Hyperdiploid MM (HRD) has 48–75 chromosomes with multiple trisomies selectively involving chromosomes 3, 5, 7, 9, 11, 15, 19 and 21; only 10% of these HRD tumors have primary IgH translocations and no frequent focal genetic mutations have been identified. In contrast primary IgH translocations are identified in over 70% of non-hyperdiploid MM (NHRD). Rearrangements of MYC have been detected by FISH in only 16% of untreated MM, but over 90% of MM cell lines, identifying a late role for MYC in the progression of MM. The introduction of a MYC transgene into a mouse strain predisposed to MGUS results in mice that uniformly develop MM, suggesting a distinct early role of MYC in the progression of MGUS to MM. We report here that rearrangements in a 4Mb region surrounding MYC are present in 70% of HRD, representing the most frequent focal genetic mutation in this genetic subtype of MM. Results: We analyzed the MMRC reference collection of gene expression (Affymetrix Hu133Plus2) and copy number (Agilent 244k CGH) data and performed FISH to identify MYC rearrangements with IgH or IgL loci in 218 patients with untreated and relapsed MM. We found MYC rearrangements in 48% of MM (identified only by FISH in 5%, only by aCGH in 33%, and by both FISH and aCGH in 10%), including 43% of untreated, and 51% of relapsed MM. Using a hyperdiploid index calculated from the median copy number of the chromosomes involved in trisomies we determined that rearrangements of MYC were present in 70% of the top third, 35% of the middle third, and 25% of the bottom third. Using the paired gene expression data we found that the expression of MYC was approximately two-fold higher in the samples with rearrangements compared to those without rearrangements (p<0.001) and about three-fold higher in MM tumors without rearrangements compared to MGUS (p<0001). Using paired RNA and DNA from the MMRC reference collection we determined in 22 informative patients that MYC rearrangements are associated with monoallelic expression of MYC (p<0.01), consistent with cis-dysregulation of MYC. Analysis of the various changes on aCGH, and fine mapping of the genetic architecture of the rearrangements using next generation sequencing identifies a promiscuous array of rearrangements that often result in the introduction of an enhancer within the MYC locus, resulting in its cis-dysregulation. Since they cannot be comprehensively identified by either CGH or FISH alone, more sensitive techniques, such as next generation sequencing approaches, will be required to comprehensively identify all MYC rearrangements in MM. Conclusions: Rearrangements of MYC are the most frequent focal genetic mutation in untreated MM and are particularly prevalent in hyperdiploid MM. While only one third involve an immunoglobulin locus, they all result in cis-dysregulated expression of MYC, and may be one mechanism responsible for the progression of MGUS to MM. Tumors lacking MYC rearrangements bi-allelically over-express MYC by a trans mechanism including potentially inactivating mutations of BLIMP1/PRDM1, or activating mutations of IRF4. We propose two largely non-overlapping pathogenic pathways in MM: HRD associated with frequent MYC rearrangements, and NHRD associated with frequent primary IgH translocations. The prevalence of MYC rearrangements increases with tumor progression, identifying a role for MYC both early and late in tumorigenesis. As therapies that have been reported to target MYC (e.g., IMiDs®, bortezomib, bromodomain inhibitors) are used in the clinic, it will be important to associate their effect with the presence or absence of MYC rearrangements. Disclosures: Bergsagel: Constellation Pharmaceuticals: Consultancy. Keats:Tgen: Employment.

Abstract Abstract 576 Stat3 appears to play a critical role in sustaining and generating memory B-cells and long-lived plasma cells (PCs) the normal counterparts of myeloma cells. In contrast to the transient nature of Stat3 activation in normal cells, many hematological tumors including multiple myeloma (MM) harbor constitutive Stat3 activity. Aberrant STAT signaling is recognized as a master regulator of direct and indirect tumor processes including proliferation, apoptosis, invasion, angiogenesis and cancer inflammation and thus Stat3 represents an important therapeutic target. Using structure-based design, targeting the phosphotyrosine (pY)-SH2 domain interactions that stabilizes active Stat3 dimers, phosphopeptides have been identified that block Stat3 dimerization and DNA binding activity. Peptidic agents however suffer from limited cell permeability and metabolic lability, properties that have restricted their practical application in vivo at therapeutic doses. Here we describe the dependence of myeloma tumors on Stat3 and characterize the anti-tumor activity of BP-2-047, a novel, non-phosphorylated small molecule with reduced peptidic character. We analyzed the activity of Stat3 using a Stat3 gene expression index based on Stat3 target genes in 60 human myeloma cell lines (HMCLs). Several available myeloma cell lines (XG6, XG7, JJN3 and UTMC2) demonstrated elevated STAT3 gene expression signatures (2.3 to 14.8) with confirmed constitutive Stat3 phosphorylation by Western blot analysis. RNA interference revealed that Stat3 is essential for XG6, JJN3, and UTMC2 survival. We similarly analyzed the activity of Stat3 in publicly available gene expression profile data sets derived from newly diagnosed MM patients. Approximately a third of patients demonstrated a functionally significant level of Stat3 signature, comparable to those in the Stat3-dependent cell lines. We next evaluated the anti-myeloma activity of the BP-2-047 in cell-based assays against a panel of HMCLs with high and low STAT3 activity. BP-2-047 delivered a desirable activity profile for targeted therapy. Consistent with its predicted mechanism of action, we observed dose-dependent inhibition of Tyr705Stat3 phosphorylation in XG6, XG7, JJN3 and UTMC2 cells, presumably through the blockade of Stat3 binding to the pTyr motifs of gp130 and the prevention of de novo phosphorylation by JAKs. Using a luciferase reporter assay we confirmed inhibition of Stat3 transcriptional activity in MM cells stably expressing the Stat3-dependent luciferase reporter (pLucTKS3). Inhibition of transcription was associated with decreased expression of short half-life proteins, c-Myc and Mcl-1. BP-2-047 inhibited viability of myeloma tumors with IC50 values of 3.1–7.4 microM, in cell lines with constitutive Stat3 activity. Inhibition of Stat3 phosphorylation resulted in induction of dose-dependent apoptosis as determined by PI/annexin V staining and PARP cleavage. However, cells were resistant to BP-2-047-induced apoptosis when co-cultured with bone marrow stroma cells. Identification of factors that confer survival advantage in the presence of stroma is in progress. Exposure of MM patient derived bone marrow mononuclear cells to < 15 microM BP-2-047 preferentially induced apoptosis of CD138 + MM cells. In contrast, BP-2-047 at concentrations of 30 microM failed to inhibit normal bone marrow-derived CD34 colony formation. In vitro combination studies in cell lines demonstrate synergy with dexamethasone, bortezomib and lenalidomide. Studies assessing in vivo activity of BP-2-047 as a single agent and in combination with bortezomib against Stat3 activated myeloma tumors in xenograft mice are ongoing and will be reported. These data suggest that Stat3 may represent an important therapeutic target in a subset of myeloma patients and supports innovative drug development with a focus on Stat3. Disclosures: No relevant conflicts of interest to declare.

Abstract Abstract 834 Multiple myeloma (MM) is an incurable bone marrow cancer. Events mediating transformation from the pre-malignant monoclonal gammopathy of undetermined significance (MGUS) to MM is unknown. We analyzed 2 gene expression datasets generated on the Affymetrix U133 platform. The test set consisted of 22 MGUS and 101 MM (GEO Accession GSE6477) and the validation set 50 MGUS and 351 MM (GEO Accession GSE2658 and GSE5900). The gene expression profiles of MM were compared to MGUS using gene-set enrichment analysis. Genes over-expressed in MM were enriched for cell cycle, proliferation and MYC activation gene-sets. We dissected the relationship between MYC and cell cycle, and identified a MYC activation signature dissociated from proliferation. We validated our MYC signature in publicly available mouse and human cell line gene expression dataset (GEO Accession GSE3151 and GSE3158 respectively), showing specific expression of our MYC signature in cell lines forced to expressed MYC but not when over-expressing other oncogene such as E2F, HER2. In these analyses, we noted that tumors with RAS mutation also consistently express this signature. Applying this signature to the test dataset, we showed that MYC is activated in 60% of myeloma but none of MGUS. This pattern is reproduced in an independent validation dataset. In order to validate the hypothesis that RAS mutation may also lead to the MYC activation signature, we correlated RAS mutation with MYC activation as measured by a MYC index calculated from the median expression of genes that constitute the MYC activation signature, and showed that almost all cases with RAS mutation have a high MYC index. Together with samples with very high expression of MYC mRNA corresponding to those with MYC translocations, these 2 mechanisms account for 67% of cases with MYC activation. To further confirm MYC activation, we performed immunohistochemistry using a validated MYC antibody together with CD138 double-staining. We can clearly identify CD138 positive plasma cells with and without nuclear MYC expression and found that nuclear expression of MYC, a marker of MYC activation, correlated strongly with the MYC signature, therefore providing clear evidence that MYC activation is present in majority of newly diagnosed MM but not in MGUS. MYC activation is not very well correlated with proliferation as assessed by the plasma cell labeling index. Among newly diagnosed myeloma patients with plasma cell labeling index less than 1, those with nuclear MYC expression have significantly shorter survival than those without (Median survival 77.7 months versus 37.9 months, log-rank p-value 0.04). Multiple pathways converge on MYC activation, which is a common transforming event in MM associated with poor prognosis. MYC nuclear staining by IHC can be a useful clinical surrogate. Targeting MYC can be a chemoprevention strategy. Disclosures: Fonseca: Amgen: Consultancy; Medtronic: Consultancy; Celgene: Consultancy; Bristol Mayor Squibs: Consultancy; Genzyme: Consultancy; Otsuka: Consultancy.

Abstract Abstract 573 Using high throughput RNA interference screening on 6,722 druggable genes we previously identified XPO1/CRM1 as one of the 50 most vulnerable targets in Multiple Myeloma (MM)1. XPO1 knockdown proved lethal in MM cell lines, but had no effect on human embryonic kidney (293) cells or lung cancer (A549) cells, showing that XPO1 is a specific myeloma vulnerability, and that myeloma cell survival is dependent upon XPO1 expression. XPO1 encodes the protein exportin 1, a nuclear transport protein that exports tumor suppressor proteins from the nucleus, where they are active, to the cytoplasm, where they become inactive. We next analyzed XPO1 in MM via gene expression profiling (GEP). XPO1 expression is up-regulated as the disease progresses: patients with active MM have a higher level of XPO1 compared to normal plasma cells (p<0.04) and to patients with monoclonal gammopathy of undetermined significance or smoldering MM (p<0.0001). The highest levels were in human MM cell lines. TC classification revealed highest levels in t(11;14) and lowest levels in t(4;14) disease. Selective inhibitors of nuclear export (SINE) compounds have recently been developed that irreversibly inhibit XPO1/CRM1 and its nuclear export function. One such inhibitor, KPT-276, decreased the viability of all 12 MM cell lines tested in vitro, as shown by MTT assay. After 72 hours of drug treatment, a median IC50 value of approximately 175 nM (range 30–1000 nM) was observed. No synergy with other commonly used anti-MM therapeutics was observed in vitro. In contrast, the drug had little effect in 8 solid tumor cell lines with the exception of the B cell lymphoma line Ramos. KPT-276 was also consistently active in inducing apoptosis against MM primary patient samples. Using an IC80 dose of KPT-276, drug-treated samples had a reduced population of cells in S phase (8%) compared to cells treated with DMSO (21%). Using the vkappa*myc transgenic MM model, KPT-276 reduced monoclonal spikes (by a mean of 56%) in all mice treated orally with 150 mg/kg dose three times per week for 4 weeks. Furthermore, KPT-276 significantly reduced tumor growth in a xenograft MM1.S mouse model. GEP was performed in the presence or absence of drug in two different MM cell lines. Two genes of probable relevance, cell division cycle 25 homolog A (CDC25A) and Bromodomain-containing protein 4 (BRD4), were dysregulated by SINE treatment. Both are involved in cell cycle control and have been linked to MYC. RT-PCR and western blotting confirm that MYC, CDC25A and BRD4 are down-regulated, as soon as six hours, after treatment with KPT-276. KPT-276 has shown marked anticancer activities against B cell malignancies in vitro and is active and tolerated in Phase I canine studies. KPT-330, a close analog of KPT-276, is currently in Phase 1 studies in human with advanced hematological and solid tumors. Disclosures: Schmidt: Karyopharm: Research Funding. McCauley:Karyopharm Therapeutics Inc: Employment. Shacham:Karyopharm Therapeutics: Employment. Kauffman:Karyopharm Therapeutics Inc: Employment. Stewart:Millenium: Consultancy, Honoraria, Research Funding; Onyx: Consultancy; Celgene: Consultancy.

Abstract Abstract 4029 Introduction: Chromosomal translocation of the FGFR3 oncogene in t(4;14)-positive multiple myeloma (MM) causes FGFR3 overexpression in plasma cells, chemoresistance, and poor prognosis leading to shorter overall survival in MM patients (pts). MFGR1877S is a human monoclonal antibody that targets FGFR3 to prevent ligand binding, receptor-receptor association, and FGFR3 signaling. In preclinical studies, anti-FGFR3 antibody suppresses FGFR3-mediated cell proliferation, and exerts strong anti-tumor activity in mouse xenograft models of both t(4;14)-positive MM and bladder carcinoma. Methods: This Phase I study assessed the safety, tolerability, and biologic activity of MFGR1877S given intravenously, weekly for 3 weeks, followed by every 28-day dosing, to eligible patients with t(4;14)-positive MM. Dose escalation started with single-pt cohorts at 1 and 2 mg/kg, followed by a standard 3+3 dose-escalation scheme at doses ranging from 4–15 mg/kg. Dose escalation decisions were made based on monitoring pts for dose-limiting toxicities (DLT) during the first 22 days on study. FGFR3 expression, safety, pharmacokinetics (PK), and response (EBMT/IMWG criteria) were assessed. Main efficacy outcome measures include serum/urine M protein and free light chain (FLC) quantities. Results: A total of 14 pts (median age 66, range 45–78; 43% female) with a baseline ECOG status of 0–2, and a median number of 5 prior therapies (range 1–10), received a median of 3.5 doses (range 1–7) of MFGR1877S. Adverse events (AEs) deemed related to MFGR1877S were diarrhea, fatigue, and nausea (14% each), and anemia, increased creatinine, bone pain, confusion, decreased appetite, myalgia, and fever (7% each). The only Grade ≥ 3 related AE was fatigue (7%). Six pts experienced 9 serious AEs (SAE), one of which was Grade 2 pyrexia attributed to MFGR1877S that occurred within 24 hours of infusion and required hospitalization. This pt later discontinued due to a second SAE of Grade 2 pyrexia requiring hospitalization not attributed to MFGR1877S. One pt died of intracranial hemorrhage not attributed to MFGR1877S. No Grade 4 SAEs were reported. Other reported SAEs included Grade 3 hypercalcemia, neutropenia, pain in extremity, and musculoskeletal chest pain (1 pt each), Grade 2 ankle fracture, pneumonia, and pyrexia × 2 (1 pt each). No maximum tolerated dose was identified, as no DLTs were observed through the highest dose tested (15 mg/kg). Preliminary PK analysis for limited number of multiple myeloma patients (n=14) by non-linear mixed effect modeling demonstrated a trend of dose proportional increase of exposure (area under the concentration-time curve and maximal concentration) from 2 to 15 mg/kg. Population clearance of MFGR1877S was estimated to be ∼0.62 L/day, suggesting that MFGR1877S appeared to have a slightly faster clearance in MM patients, compared to the typical IgG1 monoclonal antibody clearance in human. The central volume of distribution of MFGR1877S was ∼3.4 L, which approximated human serum volume and appeared similar to the central volume of distribution of other typical IgG1 monoclonal antibodies. While some degree of FGFR3 expression was detected by immunohistochemistry in 10/14 patient bone marrow samples taken at screening, FACS analysis of FGFR3 surface expression on myeloma cells, although largely consistent with IHC measurements, also revealed heterogeneity in the levels of detectable surface FGFR3 expression. Six pts had stable disease as their best response: 2 pts up to 4 cycles, 1 pt up to 3 cycles, and 3 pts up to 1 cycle. Conclusions: MFGR1877S was well-tolerated overall in these patients with multiple relapsed or refractory MM. Although no objective responses were observed, stable disease was observed in 3 pts for 3–4 cycles. Disclosures: Off Label Use: MFGR1877S is a human monoclonal antibody that targets FGFR3 to prevent ligand binding, receptor-receptor association, and FGFR3 signaling. Singhal:Millennium and Celgene: Speakers Bureau. Niesvizky:Onyx, Millemium, Celgene. Speakers bureau: Millenium and Celgene: Consultancy, Research Funding. Comenzo:Millenium, Neotope; Onyx, Osiris, Millenium: Consultancy, Research Funding. Lebovic:Genentech: Speakers Bureau. Choi:Genentech: Employment. Lu:Genentech: Employment. French:Genentech: Employment. Penuel:Genentech: Employment. Ho:Genentech: Employment.

Abstract Abstract 718 Introduction: In a previously reported phase 2 study of single agent lenalidomide in 25 untreated CLL patients (pts), we reported an overall response rate (ORR) of 56% (14 pts), 40% SD (10 pts) and no CR at a median follow-up of 20.7 months (Chen et al. JCO 2010;29:1175). Although an amended protocol with conservative lenalidomide dosing was used to mitigate tumor lysis and severe myelosuppression observed in the first 2 accrued pts, we continued to observe frequent toxicities of grade 3–4 neutropenia (72%) and tumor flare (TF 88%). We now report long-term efficacy and toxicity from this study at a median follow-up of 47 months (mos). Methods: Patients were eligible if previously untreated and symptomatic (cytopenias, symptomatic adenopathy/organomegaly, constitutional symptoms, lymphocyte doubling count <12 mos). The amended starting dose for lenalidomide was 2.5mg daily on days 1–21 of a 28 day cycle, with slow monthly dose escalations (2.5mg cycle 1, 5mg cycle 2, 10mg cycle 3 and if required for response, further 5mg increments to a maximum of 25mg daily were allowed). Results: Longterm toxicities: Hematologic toxicities were common: grade 3–4 neutropenia (76%), thrombocytopenia (28%), anemia (20%). With longer term use, neutropenia tended to recur (12% of all cycles) and 10 pts required GCSF support (5 routinely during each cycle). Most common non-hematologic toxicities (all grades) were TF (88%), fatigue (76%), rash (60%), muscle cramping (40%), diarrhea (40%). All non-hematologic toxicities were mild (grade 1–2), except for 1 pt each with grade 3 rash and diarrhea. Although TF was most common during cycle 1, repeat flare symptoms upon resuming lenalidomide after the 7 day rest period of each cycle were noted in 16% of all 898 cycles administered, and as late as at cycle 28. Infections were mild (most respiratory, skin) with only 2 grade 3 events (disseminated zoster, S.pneumoniae bacteremia). Other malignancies: 2 pts developed transformed large cell lymphoma 7 and 18 mos after study discontinuation, 1 pt developed squamous cell carcinoma of skin at cycle 51, and 1 pt developed recurrence of remote non-small cell lung cancer at cycle 34. Dose modifications/discontinuation: The median highest dose achieved for all 25 pts was 15 mg (range 2.5–25 mgs); 8 pts were able to escalate to the maximal 25mg dose. Ten pts (40%) required dose reductions for grade 3 cytopenias [neutropenia (2), thrombocytopenia (2), both (2)], febrile neutropenia (2), and diarrhea (2). Of all 25 pts, the median duration on therapy was 31.1 mos (range 28 days – 60.6 mos). Twelve pts (52%) currently remain on study, receiving a median of 59 cycles of therapy (range 48–66). Causes of discontinuation for 13 pts included: treatment-related toxicity (8), lack of response/progressive disease (4), and recurrence of remote lung cancer (1). Toxicities leading to discontinuation included: prolonged cytopenias (3), recurrent infections (1), atrial fibrillation (1), disseminated herpes zoster (1), persistent grade 2 diarrhea (1), and grade 3 skin rash (1). Efficacy: With extended median follow-up from 20.7 to 47 mos, the ORR improved from 56% (14 pts) to 72% (18 pts), with 3 pts in PR upgrading to CR, and 1 SD to PR. Although the median time to response was 7.7 mos, responses occurred as quickly as 1.8 mos to as late as 27.0 mos of therapy. For the 3 CR pts, prolonged therapy with an additional 14.9, 28.3 and 40.6 mos beyond the time of first response was required to achieve CR. To date, 7 pts have progressed with 3-year PFS 68.8% (95% CI:52–91%) and OS 85.3% (95% CI:71.1–100%). Correlatives: Cereblon (CRBN), recently identified as a direct protein target of lenalidomide, was evaluated by gene expression profiling and Western blot and found to be uniformly expressed in all 19 evaluable day 1 pt samples regardless of lenalidomide response. Thus, baseline CRBN expression does not appear to be a useful predictive biomarker of response in this population. The mechanism by which CRBN is linked to response is reported by Trudel et al, ASH 2012. Conclusions: Long-term followup of this study demonstrates that when using low doses of single agent lenalidomide in CLL, prolonged therapy is feasible and may be required for the achievement of durable, high quality responses. Maximal daily doses of 25mg can be reached and may also be needed for optimal response, though recurrent myelosuppression remains limiting. Disclosures: Chen: Celgene: Honoraria, Research Funding; GlaxoSmithKline: Research Funding; Lundbeck: Consultancy; Janssen: Consultancy, Research Funding. Off Label Use: Lenalidomide is not approved for use in chronic lymphocytic leukemia. Kukreti:Roche: Honoraria; Celgene: Honoraria; Janssen Ortho: Honoraria. Trudel:Celgene: Honoraria, Research Funding, Speakers Bureau.

Abstract Abstract 1802 Poster Board I-828 Background Heterogeneity in multiple myeloma (MM) leads to disparate outcomes with a wide variation in overall survival (OS). Based upon the evidence predominantly gathered from newly diagnosed patients treated with standard chemotherapy and/or transplantation, the current Mayo (mSMART) prognostic model uses a combination of metaphase cytogenetics, fluorescence in-situ hybridization (FISH) and plasma cell labeling index (PCLI) for risk-stratification at diagnosis of MM. The objective of our study was to evaluate the significance of this stratification model in the era of novel therapies, and to assess the independent prognostic value of each of the components in the model. Methods Data were abstracted from a cohort of 1556 consecutive patients with MM who presented to our institution between January 1999 and March 2009 within ninety days of diagnosis of MM A total of three hundred and eighty six patients had been evaluated with conventional cytogenetics near diagnosis in addition to interphase FISH. Out of this cohort, three hundred and sixty six patients had availability of all the three tests, including the slide-based PCLI. High-risk MM was defined as presence of any one or more of the following: cytogenetics: hypodiploidy, monosomy of chromosome 13 or deletion 13q ; FISH: deletion of p53 (locus 17p13) or immunoglobulin heavy chain (IgH) translocations, t(4;14) (p16.3;q32) or t(14;16)(q32;q23); PCLI ≥3%. Survival estimates were created using the Kaplan-Meier method and compared by log-rank tests. The impact of each of the three tests was assessed by a multivariate (MV) analysis using Cox proportional hazards model. Results The median OS of the cohort of 366 patients was 65 months from presentation. One hundred and twelve (31%) patients were deemed high risk by any one or more of the three tests: Metaphase cytogenetics, FISH or PCLI (current mSMART definition of high-risk MM). The median OS of high risk patients was 52 months versus 71 months for standard-risk (P=0.007). We then studied the prognostic value of the three tests separately. Patients classified as high risk by FISH had a median OS of 35 months versus 65 months for the standard risk, HR= 2.3, P<0.001. Similarly, cytogenetics alone was also able to classify patients into high and standard risk with a comparable HR of 2.1 (P=0.008, median survival 37 vs. 64 months). In contrast, PCLI did not have a significant prognostic value (HR =1.41, P=0.32). This was confirmed on multivariate analysis in a model that included all 3 tests. FISH (HR=2.36, P=0.001) and cytogenetics (HR=1.99; P=0.017) emerged as independent determinants of prognosis in the multivariable analysis, while PCLI (HR=1.03, P=0.93) did not provide additional prognostic value. We then examined whether the prognostic value of FISH contributed additionally in patients classified into high and standard risk by conventional cytogenetics, and vice versa. Those classified as high risk by cytogenetics (n=44, 11 %), were further categorized into 2 groups by additional prognostic information obtained by FISH (median survival 18 vs. 52 months; P=0.005). Similarly, those classified as standard risk by cytogenetics (n=342, 89 %), were further categorized into 2 groups (median survival 52 vs. 71 months; P=0.017) by additional FISH-based stratification. Similarly, high-risk patients defined by FISH (n=65, 17 %) were further classified into 2 groups with significant difference in median OS (18 vs. 52 months, P=0.004), based on the presence or absence of high-risk features on cytogenetics. In contrast, no additional prognostic information was gained by cytogenetics in patients who were stratified as standard risk by FISH alone (n=321, 83%). Conclusion Our study validates high risk features defined by FISH and conventional cytogenetics in the mSMART risk stratification model among patients treated after the introduction of novel therapies. Either test identifies a high risk cohort with a hazard ratio of approximately 2 (median survival ∼37 versus ∼65 months). In patients known to have high risk disease by one of the two tests, knowledge of the other appears to add additional prognostic value. Disclosures Fonseca: Amgen, BMS, Celgene, Otsuka, Genzyme and Medtronic: Consultancy. Gertz:celgene, millennium: Honoraria. Dispenzieri:celgene: Research Funding. Kumar:celgene, genzyme, millennium, novartis, bayer: Research Funding; genzyme: Membership on an entity's Board of Directors or advisory committees.

Abstract Abstract 194 Background: Immunomodulatory drugs (IMiDs) are key components of treatment for hematologic malignancies, especially multiple myeloma (MM). Recently, we demonstrated that CRBN expression is the major mediator of IMiD action operating at least in part via interferon regulatory factor 4 (IRF4), however the clinical significance of this finding remains unclear. Methods: To better understand clinical impact, we retrospectively reviewed 148 MM patients whose tumor cells were tested for CRBN expression by Gene Expression Profiling (GEP) prior to treatment with an IMiD containing therapy. Results: GEP studies show no significant differences in CRBN expression between MGUS, smoldering MM (SMM), untreated symptomatic MM and normal plasma cells. However, differences were observed between MM cell lines of varying drug sensitivity to IMiDs and between other B-cell Neoplasia (eg low grade lymphoma has higher levels). Within the genetic subtypes of MM, levels were significantly higher for hyperdiploid patients (median 1.26) as opposed to significantly lower levels for TC class D2 (median 0.76) and average for the 4p16 (median 0.97). We next screened the University of Arkansas Medical School (UAMS) GEP database of MM patients treated with combination therapies and did not find significant correlation between CRBN expression and survival in this multi-agent regimen. We then focused on patients that received only single agent IMiD therapy with low dose dexamethasone. Review of the twelve lowest expressing patients demonstrated a lack of response to IMiDs in any patient. Finally we analyzed 53 relapsed or relapsed/refractory patients treated homogeneously in a study with pomalidomide 2–4mg daily and weekly dexamethasone 40mg. CRBN levels were assessed prior to therapy initiation. Response rates varied significantly based on gene expression level. The percentage of patients that demonstrated at least a partial response was 0% for CRBN <0.81, 19% for CRBN expression of 0.81–0.90, and 33% for CBN expression >0.9. Significant differences in PFS (3.0 months vs. 8.9 months, p = 0.0006) and in OS (9.1 months vs. 27.2 months, p = 0.01) were observed when the lowest quartile of CRBN expression was compared to the top three quartiles. Values used for the cut offs are as follows: (25%: 0.889687; 50%: 1.026542, 75%: 1.211133). While this study demonstrates a positive correlation between CRBN expression and response to pomalidomide and dexamethasone, an important caveat with respect to PFS and OS is that CRBN mRNA level is primarily a reflection of the number of copies of CRBN. Since focal deletions are uncommon, this mostly reflects chromosome 3p copy number. Since trisomy 3 is common in hyperdiploid, good prognosis disease, CRBN not only is required for IMiD function but higher levels also serve as a surrogate for low risk disease. Optimal gene expression cut offs for survival were determined using the Contal and O'Quigley method. The optimal cut point for PFS was 1.18443 and for OS was 1.17816. Conclusion: In summary, this study demonstrates, for the first time, a clinical correlation between CRBN expression and response to IMiD and dexamethasone therapy. CRBN expression is also predictive of survival outcomes and when quantified prior to therapy could potentially be utilized as a predictive biomarker for response to an IMiD based treatment. Disclosures: Stewart: Celgene: Consultancy, Honoraria.

Abstract Abstract 832 We hypothesized that new therapeutic targets for multiple myeloma (MM) could be discovered through the integrative computational analysis of genomic data. Accordingly, we generated gene expression profiling and copy number data on 250 clinically-annotated MM patient samples. Utilizing an outlier statistical approach, we identified HOXA9 as the top candidate gene for further investigation. HOXA9 expression was particularly high in patients lacking canonical MM chromosomal translocations, and allele-specific expression analysis suggested that this overexpression was mono-allelic. Indeed, focal copy number amplifications at the HOXA locus were observed in some patients. Outlier HOXA9 expression was further validated in both a collection of 52 MM cell lines and 414 primary patient samples previously described. To further verify the aberrant expression of HOXA9 in MM, we performed quantitative RT-PCR, which confirmed expression in all MM patients and cell lines tested, with high-level expression in a subset. To further investigate the mechanism of aberrant HOXA9 expression, we interrogated the pattern of histone modification at the HOXA locus because HOXA gene expression is particularly regulated by such chromatin marks. Accordingly, immunoprecipitation studies showed an aberrantly low level of histone 3 lysine 27 trimethylation marks (H3K27me3) at the HOXA9 locus. H3K27me3 modification is normally associated with silencing of HOXA9 in normal B-cell development. As such, it appears likely that the aberrant expression of HOXA9 in MM is due at least in part to defects in histone modification at this locus. To determine the functional consequences of HOXA9 expression in MM, we performed RNAi-mediated knock-down experiments in MM cell lines. Seven independent HOXA9 shRNAs that diminished HOXA9 expression resulted in growth inhibition of 12/14 MM cell lines tested. Taken together, these experiments indicate that HOXA9 is essential for survival of MM cells, and that the mechanism of HOXA9 expression relates to aberrant histone modification at the HOXA9 locus. The data thus suggest that HOXA9 is an attractive new therapeutic target for MM. Disclosures: No relevant conflicts of interest to declare.