Stewart, A. Keith

Abstract Introduction: We employed a customized Multiple Myeloma (MM) specific Mutation-Panel (M3 P) to screen a homogenous cohort of refractory MM (rMM) patients in a timely and cost-effective manner. rMM was defined as progressive disease (PD) during therapy or within 60 days after discontinuation of therapy. The M3 P provides a practical alternative to whole genome/exome sequencing approaches and includes 88 genes selected for being either actionable targets, potentially related to drug response or part of known key pathways in MM biology. Patients and Methods: Tumor and germline samples of 50 rMM patients were screened using M3 P. Patients received a median of five lines of treatment at the time of tumor sampling (range 2-15 lines). All patients received at least one immunomodulatory agent (IMiD) and proteasome inhibitor (PI), and 88%, 76% and 66% were refractory to either an IMiD, PI or both. All patients had received lenalidomide and bortezomib, 48% and 34% were additionally exposed to pomalidomide and thalidomide and 18% to carfilzomib at any time prior to sampling. The majority of patients had a progressive and refractory disease immediately prior to sampling (82% and 78%), with 43% of them being IMiD-refractory and 46% being PI-refractory in the most recent line of therapy. Cytogenetic data at time of sampling were available from 78% of patients. Adverse cytogenetics were detectable in 82% of patients with gain 1q21 > 2 copies (62%), deletion 17p (33%), t(4;14) (13%) and t(14;16) (8%) being the most common. Results: An average sequencing depth of 750x was obtained across the samples. Our screening revealed an increased prevalence of mutations in the MAPK pathway (72%), including 34% of KRAS, 26% of NRAS, 18% of BRAF (with one patient carrying two BRAF mutations and 8% in actionable p.V600E). Additionally, two mutations (4%) were found in RASA2, a RAS inhibitor. Other potentially actionable mutations were seen in p.R132H IDH1 and p.R248C FGFR3 (2% each). Most prominently, the CRBN pathway was found mutated in 22% of cases, including CRBN (12%, one case with concomitant CUL4B mutations), CUL4B (4%), IRF4 (4%) and IKZF1 (2%). In CRBN we found four cases with mutations leading to a truncated protein (frameshift, nonsense and splicing) and two cases with missense mutations located within the thalidomide-binding domain, suggesting a causal effect on IMiD resistance. All CRBN mutated patients and 91% of the CRBN pathway mutated patients were at least once unresponsive to IMiD based treatment. In one patient with IRF4 mutation sensitivity to IMiDs remained unknown. A majority of patients were also resistant to PI treatment (76%), however mutations in proteasome subunits (PSMD1 and PSMB8) and XBP1 wererare (4%), but only a limited number of this gene family were represented in our panel. Other recurrently mutated genes were TP53 (26%), FAM46C (12%), ATM (10%) and TRAF3 (8%). Notably, DIS3 mutations were identified in only 6% of cases. As previously reported, TP53 mutations were associated with deletion 17p (8/13 cases, 62%). A correlation between the absolute number of mutations and previous lines of treatment was not observed (r=0.05, p=0.73). Conclusion: Targeted sequencing on a homogenous cohort of heavy pretreated rMM patients gives key insights in the landscape of the rMM genome, uncovering an increasing frequency of MAPK, TP53 and CRBN mutations. Importantly, this is the first study showing recurrent mutations in CRBN in patients unresponsive to IMiD treatment, supporting a potential association with resistance to IMiD based therapies. Disclosures Mai: Onyx: Other: Travel Grant; Janssen-Cilag: Other: Travel Grant; Celgene: Other: Travel Grant; Mundipharma: Other: Travel Grant. Merz:Janssen: Other: Travel grants; Celgene: Other: Travel grants. Hillengass:Takeda: Honoraria, Other: Travel support; Novartis: Membership on an entity's Board of Directors or advisory committees, Research Funding; Sanofi: Research Funding; Janssen-Cilag: Honoraria, Other: Travel support; Celgene: Honoraria, Other: Travel support. Goldschmidt:Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Janssen-Cilag: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Millennium: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Onyx: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Chugai: Research Funding, Speakers Bureau. Stewart:Oncospire Genomics: Research Funding.

Abstract Abstract 3031 Background: Treatment-induced peripheral neuropathy (TIPN) can be a debilitating side-effect as well as a therapy-limiting complication in multiple myeloma (MM). Thalidomide (THAL) and bortezomib (BTZ) are two therapies frequently associated with TIPN in MM. Carfilzomib (CFZ) is a novel and highly selective epoxyketone proteasome inhibitor that differs from BTZ both structurally and mechanistically. CFZ overcomes BTZ-resistance in vitro, lacks the off-target activities of BTZ in preclinical studies, and does not cause neurotoxicity in long-term (6–9 month) chronic animal toxicology studies (Kirk et al. Blood, 2008). Single-agent CFZ produces durable responses in relapsed or refractory (R/R) MM without dose-limiting PN. Here we report on the clinical experience with single-agent CFZ in the Ph 2b PX-171-003-A1 trial in patients (pts) with R/R MM and Grade (G) 1/2 PN at study entry. Methods: Pts received CFZ at 20 mg/m2 IV, on Days 1, 2, 8, 9, 15, and 16 in a 28-day cycle (C) for the first C followed by 27 mg/m2 thereafter for up to 12 C. Pts completing 12 C were eligible to enter an extension study. Responses and progression were determined according to the International Myeloma Working Group (IMWG) criteria and were assessed by an Independent Review Committee (IRC). PN data were collected for all pts on study and included neuropathy history, neurological physical exam and PN-related quality of life data (FACT-GOG/NTx v 4.0 scores) collected at screening. Prospective neurological exams and subjective reporting of PN occurred every 2 cycles until study discontinuation to proactively assess for PN. Adverse event (AE) data were also collected, with AEs reported as ‘neuropathy peripheral', ‘neuropathic pain', ‘neuropathy', and ‘peripheral sensory neuropathy' included as PN. AE reports of ‘paraesthesias' and ‘dysesthesias' were counted separately. Results: Of the 266 pts with R/R MM in PX-171-003-A1, 237 (89%) had a history of PN which was attributable to prior anti-myeloma therapy, including THAL (108 pts/41%), BTZ (134 pts/50%), or both BTZ and THAL (17 pts/6.4%). 206 of the 266 (77%) had G1/2 PN at baseline and a median disease duration of 5.9 years. This subset with active PN at baseline had received a median of 5 prior lines of therapy (range 1–20), with a median 13 anti-myeloma agents, and a median of 2 prior BTZ- and 1 prior THAL- containing regimens. Prior therapies included 100% BTZ, and 100% either THAL (77%) or prior lenalidomide (95%). Responses in the subset of pts with baseline PN were nearly identical to those seen in the full study population with an overall response rate (ORR; ≥ partial response [PR]) of 24% and a clinical benefit response rate (CBR; ≥ minimal response [MR]) of 36%. The median duration of response (≥PR) was 7.4 mo (95% CI 5.6–not reached) and median duration of MR was 6.3 months in both the overall and PN-baseline cohorts. OS and TTP data will also be reported. The most common treatment-emergent ≥G3 adverse events regardless of relationship to study drug were primarily hematologic and were as follows: thrombocytopenia (24%), anemia (21%), lymphopenia (11%), pneumonia (9%), neutropenia (9%), fatigue (7%), hypercalcemia (7%), and hyponatremia (6%). Although 77% of pts had G1/2 PN at baseline, new onset PN was infrequent with PN AEs of any grade reported in 31 (15%) pts and G3 PN reported in only 1 (0.4%) pt. New onset or worsening of paraesthesias (6.8%) and dysesthesias (0%) was also infrequent. Conclusions: Analysis of the subset of pts (77%) with active PN (G1/2) in this single-agent Ph 2 trial of CFZ in pts with R/R MM demonstrated that PN has no impact on depth or durability of responses, or on the tolerability of CFZ, in heavily pretreated pts with multiply relapsed and refractory MM. Reports of new or worsening PN were very uncommon, and paraesthesias and dysesthesia were generally infrequent and mild. CFZ can be given to pts with baseline PN with little risk of exacerbation; prolonged therapy is possible in this population. Disclosures: Martin: Celgene: Honoraria; Onyx: Consultancy. Singhal:Celgene: Speakers Bureau; Takeda/Millenium: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Onyx: Research Funding. Vij:Onyx: Honoraria. Wang:Celgene: Research Funding; Onyx: Research Funding; Millenium: Research Funding; Novartis: Research Funding. Stewart:Millennium: Consultancy; Celgene: Honoraria. Jagannath:Millenium, OrthoBiotec, Celgene, Merck, Onyx: Honoraria; Imedex, Medicom World Wide, Optum Health Education, PER Group: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Lonial:Millennium: Consultancy, Research Funding; Celgene: Consultancy, Research Funding; Novartis: Consultancy, Research Funding; BMS: Consultancy, Research Funding; Onyx: Consultancy, Research Funding. Jakubowiak:Millennium Pharmaceuticals, Inc.: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Celgene: Consultancy, Honoraria; Centocor Ortho Biotech: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Exelixis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Bristol-Myers Squibb: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees. Kukreti:Celgene: Honoraria; Roche: Honoraria; Ortho Biotech: Honoraria. Alsina:Millenium: Consultancy, Research Funding; Celgene: Research Funding; Novartis: Consultancy. Zonder:Millenium: Consultancy, Honoraria, Research Funding; Cephalon: Research Funding; Celgene: Honoraria. Wong:Onyx Pharmaceuticals: Employment. Vallone:Onyx Pharmaceuticals: Employment. Chang:Onyx Pharmaceuticals: Employment. Kauffman:Onyx Pharmaceuticals: Employment. Siegel:Millenium: Consultancy, Honoraria; Celgene: Consultancy, Honoraria.

Abstract Introduction Multiple myeloma (MM) is characterized by a highly variable disease course, which can be traced to initiating and acquired genomic events. Whole exome analysis of matched tumor and germline DNA from 287 MM patients identified recurrently somatically mutated genes (RSMGs) (Lohr et al. - Cancer Cell 2014, Bolli et al. - Nat Commun 2014). Despite the fact that these RSMGs affect pathways that are biologically important in MM, the clinical relevance of many of these genes in the context of conventional prognostic markers remains to be elucidated. Aims The aims of this pilot study were: (1) To validate the prevalence of RSMGs in our newly diagnosed MM patient cohort; (2) To assess the correlation between RSMGs, clinical parameters and outcome; (3) To thereby identify the potential clinical usefulness of introducing RSMG mutational profiling in larger MM trial cohorts. Material and Methods CD138+ enriched MM cells and peripheral blood were obtained with informed consent from chemotherapy-naive patients, participating in 3 clinical trials: HOVON-65/GMMG-HD4, HOVON-87/NMSG-18 and Carthadex (EudraCT number 2004-000944-26, 2007-004007-34 and 2009-014922-40, respectively). Matched tumor and germline DNA were sequenced on an Ion Torrent sequencing platform (PGM, Life Technologies), using the M3 P Mutational Panel v3.0, comprising 1327 customized oligos (Life Technologies), targeted at the coding sequences of 88 MM-relevant genes, including the RSMGs. Somatic mutations were considered positive when present in >=10% of tumor reads and <=10% germline reads, with a minimal coverage of 10x and being non-synonymous, or splice donor variants. All statistical analyses were performed in SPSS version 23, using the log-rank and Mann-Whitney U-test, with the Bonferroni test to correct for multiple comparisons. Results A total of 206 DNA samples were sequenced from 103 patients (HOVON-65/GMMG-HD4 (n=16), HOVON-87/NMSG-18 (n=67), Carthadex (n=20)) with an average coverage of 574x in tumor DNA, 451x in germline DNA and an overall coverage of 98%. We collected follow-up data from 102/103 patients, with a median follow-up time of 30 months. 168 somatic mutations were detected in 44/88 genes. 82% of patients had at least 1 somatic mutation. Genes most frequently mutated were: (1) NRAS (26%), (2) KRAS (22%), (3) DIS3 (14%), (4) FAM46C (9%), (5) TP53 (7%) and (6) BRAF (6%) (Figure 1). Of note, NRAS and KRAS mutations were mutually exclusive in our cohort. Moreover, all TP53 mutations were located in its DNA binding domain. Three out of 6 BRAF mutations were predicted to cause a V600E amino acid change. We focused on these 6 RSMGs in all further analyses. Correlating mutational status with Progression Free Survival (PFS) and Overall Survival (OS) showed that TP53 mutated patients had a significantly shorter PFS compared to those with wildtype TP53 (adj. p-value=0,018; n=7 versus n=95). Comparing the mutational status of the 6 RSMGs, transplant versus non-transplant protocol, number of mutated genes in the M3 P panel, del17p and t(4;14) status, EMC92 score and ISS stage between patients with a PFS <=1 year and >1 year (n=23 versus n=79), only showed a significant correlation with TP53 mutational status (adj. p-value=0,012). TP53 mutational status remained the only significant prognostic factor when comparing patients with an OS <=1 year and >1 year (adj. p-value=0,003; n=13 versus n=89). When comparing the number of mutated genes, del17p and t(4;14) status, EMC92 score, transplant versus non-transplant protocol and ISS stage between TP53 mutated and wildtype MM, TP53 mutated patients had a significantly higher number of mutated genes in the M3 P panel (adj. p-value=0,001). Conclusions (1) With the M3 P Mutational Panel, we confirm the published prevalence of RSMGs in MM in our cohort of chemotherapy-naive patients. NRAS, KRAS, DIS3, FAM46C, TP53 and BRAF are the most frequently mutated genes. (2) TP53 mutational status is the strongest unfavorable prognostic factor in our cohort and it seems to be associated with greater mutational burden. Validation in a more extensive population is planned. (3) This warrants further investigation of the mutational status of these genes in larger clinical trial cohorts, enabling a more robust comparison with conventional prognostic markers in a multivariate analysis. Disclosures Broijl: Celgene: Membership on an entity's Board of Directors or advisory committees; Amgen: Membership on an entity's Board of Directors or advisory committees. Zweegman:Takeda: Research Funding; Janssen: Research Funding; Celgene: Research Funding. Sonneveld:Janssen: Honoraria, Research Funding; Celgene: Honoraria, Research Funding; Amgen: Honoraria, Research Funding; Karyopharm: Research Funding; SkylineDx: Membership on an entity's Board of Directors or advisory committees.

Abstract Abstract 39 Three randomized trials have previously reported a progression-free survival (PFS) advantage for patients receiving thalidomide (T) maintenance post ASCT in MM. Two trials reported an overall survival (OS) advantage but the largest trial reported shows no OS advantage and in very high risk MM the use of T was deleterious. Recent trial reports demonstrate a PFS but not yet an OS advantage for patients receiving maintenance lenalidomide. We report results of NCIC CTG MY.10 which compared treatment with T (200 mg daily) and prednisone (50 mg alternate days) (T/P) until progression versus observation alone when used as maintenance therapy following ASCT. Importantly, OS was the 1ry endpoint of this study, 2ry endpoints were PFS, quality of life (QoL), toxicity, and the incidence of venous thromboembolism events (VTE). Eligibility: Patients with MM who had ASCT within 1 year of beginning initial treatment for their disease. Patients were randomized 60–100 days post ASCT and had no other medical condition precluding long term use of T/P. Results: 332 patients were enrolled. Median age was 58 years and the arms were balanced. Patients were stratified by age (<60 or >60), and CR status post transplant. Median follow up is 4 years. Only 14% of patients were in CR post transplant. 111 patients died (50 versus 61 in T/P vs. observation). The median OS was 5 years for observation, and has not yet been reached for T/P, however T/P maintenance therapy did not significantly prolong OS: p = 0.18, HR of maintenance vs. observation 0.77 (95% CI 0.53–1.13). The 4 year survival rate was 68% for T/P and 60% for observation. Age and response to transplant had no significant association with OS (p=0.21), while higher disease stage was associated with shorter OS (p=0.03). The median PFS was 28 months for T/P versus 17 months for observation: p<0.0001, HR of T/P vs. observation 0.56 (95% CI 0.43 – 0.73). The 4 year PFS rate was 32% for T/P treated patients versus 14% for patients on observation. At relapse, treatment by arm (T/P vs observation) included lenalidomide (39 vs 34%), T (13 vs 22%) or bortezomib (50 versus 46%). Non hematologic toxicities were seen in more patients with treatment (Grade 3: 92% T/P vs 49% observation, grade 4: 16% vs 7%). Common toxicities of all grades that were significantly higher in T/P treated patients included hyperglycemia, edema, hypertension, fatigue, Cushingoid appearance, constipation, mouth dryness, dyspepsia, anxiety, memory loss, sensory neuropathy, tremor, blurred vision, depressed consciousness, cataracts, dyspnea and bruising. 7% of patients on maintenance T/P developed a VTE in the absence of prophylaxis versus 0% on observation. NCIC CTG standardized response analysis was use to compare QoL data between the 2 treatment arms. Overall, patients on T/P had worse QoL specifically in physical (p=0.07), role (p=0.08), cognitive (p = 0.01) and global (p=0.06) domains, and worse symptoms with dyspnea (p = 0.0007), constipation (p<0.0001), thirst (p=0.003), swelling in leg (p=0.03), numbness (p=0.02), dry mouth (p<0.0001), and balance problems (p<0.0001). However, patients on T/P reported improvement in appetite (p 0.02), and sleep (p=0.04). Conclusions: T/P maintenance did not improve overall survival, the primary objective of this trial, although a trend in favor of T/P was seen. In contrast, PFS was significantly improved in the T/P arm while toxicity was demonstrably increased and quality of life diminished. Disclosures: Stewart: Millennium: Consultancy; Celgene: Honoraria. Trudel:Celgene: Honoraria. Bahlis:Celgene: Honoraria, Research Funding, Speakers Bureau. White:Celgene: Honoraria, Research Funding. Meyer:Celgene: Honoraria.

Abstract Introduction Gene Expression Profiling studies have resulted in signatures capable of providing robust prognosis for Multiple Myeloma (MM) patients, such as the EMC92 [SKY92, Kuiper et al. Leukemia 2012]. Recently, data from 4720 MM patients from the HOVON-65/GMMG-HD4, UAMS-TT2, UAMS-TT3, MRC-IX, APEX and IFM trials were employed to assessed the majority of currently identified prognostic markers and their combinations (GEP, FISH, and biochemistry data, [Kuiper et al ASH 2014]). The "SKY92 + ISS" was identified and validated as the statistically most optimal (i.e. most significant and robust) prognostic marker combination for MM patients. The combination of the EMC92 (=SKY92) and ISS prognostic features proves to be a very powerful, unprecedented and straightforward prognostic system. It identifies four prognostic risk classes: low risk (ISS I-SKY92 standard risk (SR)), intermediate-low (ISS II-SKY92 SR), intermediate-high (ISS III-SKY92 SR) and high risk (ISS I-III, SKY92 high risk). Previously, the SKY92 has been validated on the 91 MM cases in the MMGI cohort [Van Beers et al. ASH 2013]. Here we present an extension of that validation with the SKY92 + ISS combination on the 78 MM cases for whom both GEP and ISS is available, by both assessing as the "4 risk group" model defined above, but also a "3 risk group" model (the two intermediate groups combined) as this may be more relevant and useful for clinical application. Materials and Methods A public untreated MM dataset (Multiple Myeloma Genomics Initiative, MMGI) had n=78 cases for which OS, GEP, and ISS were available for analysis. The prognostic markers SKY92 and ISS were applied as proposed [Kuiper et al ASH 2014] to classify cases into the risk categories. Results The risks for the 4 group classification model are shown in Table 1 and Figure 1, and the 3 risk group model is shown in Table 2 and Figure 1. In the 4 group model, the intermediate-low group (SKY92 standard + ISS II) was a small and not significantly different (p=0.79) from the low risk. The intermediate-high group (SKY92 standard + ISS III) was also a small group, with significantly worse outcome compared with the low risk group (p=0.012). Although stratification into four groups was statistically superior in the training and validation data [Kuiper et al ASH 2014] the interpretability benefits from aggregation of the middle two groups [Fig 1 right]. Table 1. Classification results for the four risk groups (Fig 1 left) Risk group n % Median OS HR vs low risk SKY92 High Risk regardless of ISS 19 24 28.4 m 10.8 SKY92 standard risk + ISS-III 10 13 63.0 m 4.1 SKY92 standard risk + ISS-II 16 21 NR (0.8) SKY92 standard risk + ISS-I (low risk) 33 42 NR NA NR= Not Reached at 96 months, HR= hazard ratio Table 2. Classification results for the three risk groups (Fig 1 right) Risk group n % Median OS HR vs low risk SKY92 High Risk regardless of ISS 19 24 28.4 m 10.1 SKY92 standard risk + ISS-II/III 26 34 78.5 m (1.8) SKY92 standard risk + ISS-I 33 42 NR NA NR= Not Reached at 96 months, HR= hazard ratio, () not significant Conclusions By applying the SKY92 + ISS risk stratification model in an independent validation cohort of newly diagnosed Multiple Myeloma patients, besides a high risk group of 19 patients (24%), a group of 33 patients (42%) with superior prognosis could be predicted (SKY92 standard risk and ISS I) that translated into 62% OS at 96 months. The 19 high risk (SKY92 high risk) cases had very poor prognosis (median survival of 28 months). The combination of SKY92 Standard Risk and ISS II and III seems useful for definition of "intermediate risk" although sample size currently is insufficient for significance compared to low risk. The intention is to also perform this validation on the relapsed samples from the MMGI cohort, once OS data has been collected. This validated risk model could play a role in the design of future treatment strategies for high and low risk MM patients. Figure 1. Kaplan Meier curves on the 78 MMGI cases, split into four (left) or three (right) risk groups based on the combination of SKY92 + ISS. Hazard Ratios (HR) are from a Cox proportional Hazards model comparing a particular group to the low risk group. Figure 1. Kaplan Meier curves on the 78 MMGI cases, split into four (left) or three (right) risk groups based on the combination of SKY92 + ISS. Hazard Ratios (HR) are from a Cox proportional Hazards model comparing a particular group to the low risk group. Disclosures van Beers: SkylineDx: Employment. van Vliet:SkylineDx: Employment. de Best:SkylineDx: Employment. Chari:Novartis: Consultancy, Research Funding; Millennium/Takeda: Consultancy, Research Funding; Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Biotest: Other: Institutional Research Funding; Array Biopharma: Consultancy, Other: Institutional Research Funding, Research Funding; Onyx: Consultancy, Research Funding. Jagganath:Millennium: Honoraria; Celgene: Honoraria. Jakubowiak:Sanofi-Aventis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Onyx: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Karyopharm: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Bristol-Myers Squibb: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: institutional funding for support of clinical trial conduct, Speakers Bureau; SkylineDx: Membership on an entity's Board of Directors or advisory committees; Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Karyopharm: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; SkylineDx: Membership on an entity's Board of Directors or advisory committees; Onyx: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Sanofi-Aventis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Millennium: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Millennium: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Kumar:Celgene, Millenium, Sanofi, Skyline, BMS, Onyx, Noxxon,: Other: Consultant, no compensation,; Janssen: Research Funding; AbbVie: Research Funding; Sanofi: Research Funding; Millenium/Takeda: Research Funding; Celgene: Research Funding; Onyx: Research Funding; Skyline, Noxxon: Honoraria. Lebovic:Onyx: Speakers Bureau; Celgene: Speakers Bureau. Lonial:Millennium: Consultancy, Research Funding; Bristol-Myers Squibb: Consultancy, Research Funding; Onyx: Consultancy, Research Funding; Janssen: Consultancy, Research Funding; Novartis: Consultancy, Research Funding; Celgene: Consultancy, Research Funding. Reece:Onyx: Honoraria; Novartis: Honoraria; Millennium: Research Funding; Merck: Honoraria, Research Funding; Janssen: Honoraria, Research Funding; Celgene: Honoraria, Research Funding; BMS: Research Funding. Richardson:Millennium Takeda: Membership on an entity's Board of Directors or advisory committees; Celgene Corporation: Membership on an entity's Board of Directors or advisory committees; Jazz Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees, Research Funding; Gentium S.p.A.: Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Membership on an entity's Board of Directors or advisory committees. Siegel:Celgene Corporation: Consultancy, Speakers Bureau; Amgen: Speakers Bureau; Takeda: Speakers Bureau; Novartis: Speakers Bureau; Merck: Speakers Bureau. Stewart:SkylineDx: Membership on an entity's Board of Directors or advisory committees. Vij:Onyx: Consultancy, Honoraria, Research Funding, Speakers Bureau; Celgene: Consultancy, Honoraria, Research Funding, Speakers Bureau; Millennium: Honoraria, Speakers Bureau; BMS: Consultancy; Takeda: Consultancy, Research Funding; Novartis: Consultancy; Sanofi: Consultancy; Janssen: Consultancy; Merck: Consultancy. Zimmerman:Celgene: Honoraria, Speakers Bureau; Millennium: Honoraria, Speakers Bureau; Onyx: Honoraria; Amgen: Honoraria, Speakers Bureau. Fonseca:Onyx/Amgen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties, Research Funding; BMS: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties, Research Funding; Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties, Research Funding; Bayer: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties, Research Funding; Binding Site: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties, Research Funding; Millennium: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties, Research Funding; Applied Biosciences: Membership on an entity's Board of Directors or advisory committees; Sanofi: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties, Research Funding; Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties, Research Funding.

Abstract Abstract 127 Two- and three-drug regimens incorporating bortezomib (Velcade®, Vc), lenalidomide (Revlimid®, Rev), dexamethasone (Dex), and cyclophosphamide (Cy) (Vc–Dex, Rev–Dex, Vc–Dex–Rev [VDR], and Vc–Dex–Cy [VDC]), have been shown to be effective and well tolerated in previously untreated multiple myeloma (MM). Combining Vc and Dex with Rev and Cy in a novel four-drug regimen (VDCR) may result in even greater activity with improved quality and duration of response. Results from the phase 1 dose-escalation portion of the multi-center EVOLUTION study showed that the VDCR regimen is a highly active and generally well-tolerated induction therapy in previously untreated MM patients (pts). Here we report the efficacy and safety of VDR, VDC, and VDCR from the non-comparative phase 2 portion of the study. Methods: Pts were randomized to receive up to eight 21-d cycles of VDR (Vc 1.3 mg/m2 d 1, 4, 8, 11; Dex 40 mg d 1, 8, 15; Rev 25 mg d 1–14) or VDC (VD as in VDR, plus Cy 500 mg/m2 d 1, 8) or VDCR (VDC plus Rev 15 mg d 1–14) as induction therapy, followed by Vc 1.3 mg/m2 (d 1, 8, 15, 22) for four 42-d maintenance cycles in all treatment arms. Pts received prophylactic antibiotics, acyclovir, transfusion support, and anticoagulants as required. Eligible pts wishing to undergo autologous stem cell transplant (ASCT) could undergo stem cell mobilization any time after cycle 2, and undergo ASCT any time after cycle 4. Response categories were based on the IMWG Criteria with the addition of near complete response (nCR). Adverse events (AEs) were graded using the CTCAE v3.0. Results: In the VDR, VDC, and VDCR arms 42, 32, and 43 pts (including 6 pts treated at the maximum planned dose of Cy (500 mg/m2) from phase 1) have been treated, and 42, 31, and 33 are evaluable for response, respectively, as of data cut-off (31 July 2009). Median ages in the VDR, VDC, and VDCR arms were 60, 62, and 62 years, respectively; 62%, 63%, and 66% had International Staging System stage lI/III disease, and 38%, 25%, and 33% had Karnofsky Performance Status ≤80%, respectively. The median number of VDR, VDC, and VDCR cycles received is 4.5, 6, and 4, respectively (range 1–12). Best unconfirmed response rates are shown in the Table; patients categorized as very good partial response (VGPR) include those who have no measurable M-protein but have not yet had bone marrow assessments to confirm CR/nCR status. The overall rates of treatment-emergent AEs were 95%, 97%, and 88% for the VDR, VDC, and VDCR arms, respectively, with ≥grade 3 reported in 67%, 59%, and 65%. Peripheral neuropathy (PN) was reported as grade 2/3 in 12%/12% in the VDR, 31%/3% in the VDC, and 12%/9% in the VDCR arms; there was no grade 4 PN reported. Grade 3/4 neutropenia was reported in 5%/5%, 28%/13%, and 23%/9% of pts in the VDR, VDC, and VDCR arms, and grade 3/4 thrombocytopenia in 5%/2%, 9%/0%, and 5%/0% of pts, respectively. One case of grade 3 deep-vein thrombosis was reported in the VDCR arm. Overall rates of serious AEs were 24%, 13%, and 37% in the VDR, VDC, and VDCR arms, respectively. Two pts have died in the VDCR arm, both due to renal failure, considered possibly treatment-related. To date, 6 pts have undergone ASCT in the VDR arm, 5 in the VDC arm, and 3 in the VDCR arm. Median CD34+ yield was 4.7, 6.3, and 6.8 × 106/kg in the VDR, VDC, and VDCR arms, respectively. Conclusions: VDR, VDC, and VDCR are highly active and generally well-tolerated regimens in previously untreated MM. Response rates in the VDCR arm appeared somewhat higher than in the VDR and VDC arms at this early time point, although there also appeared to be higher rates of serious AEs, including possible treatment-related mortality in the VDCR arm. Following an interim analysis, dosing in the VDC arm was modified to include Cy on day 15 to examine if this will improve CR rates. Ten pts have been enrolled to date. Disclosures: Kumar: CELGENE: Research Funding; MILLENNIUM: Research Funding; BAYER: Research Funding; GENZYME: Research Funding; NOVARTIS: Research Funding. Flinn:Millennium Pharmaceuticals, Inc.: Membership on an entity's Board of Directors or advisory committees, Research Funding. Hari:Milennium Pharmaceuticals Inc.: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Celgene: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Callander:Millenium: Research Funding. Noga:Millennium Pharmaceuticals: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees. Stewart:Takeda-Millenium, Celgene, Novartis, Amgen: Consultancy; Takeda, Millenium: Research Funding; Genzyme, Celgene, Millenium, Proteolix: Honoraria. Raje:Celgene: Research Funding; Novartis: Research Funding; AstraZeneca: Research Funding. Rifkin:Millennium Pharmaceuticals, Inc: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Celgene: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Amgen: Speakers Bureau; Cephalon: Speakers Bureau. Shi:Millennium Pharmaceutical Inc.: Employment. Webb:Millennium: Employment, Equity Ownership. Richardson:Keryx: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Novartis: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Johnson and Johnson: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Millennium Pharmaceuticals, Inc.: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; BMS: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau.

Abstract Introduction: Customized gene panel sequencing is an attractive approach to genomic tumor characterization in clinical care. Based on published MM exome data we developed a MM Mutation Panel (M3 P) that includes the most commonly mutated genes, actionable drug targets, genes targeted by current standard of care (SOC) therapies and which allows tracking of clonal evolution, copy number and sample purity. Methods and Material: M3 P (v3.0) covers 88 genes (1327 amplicons, 181kb). MM samples from 504 patients (pts) have been analyzed (corresponding germline in 81%) through collaborations between Mayo Clinic and Hospital-12-de-Octubre (Madrid, Spain), the DSMM and GMMG (Würzburg, Ulm, Freiburg and Heidelberg, Germany) and the HOVON trial groups (Rotterdam, The Netherlands). The investigated cohort includes 410 untreated pts (81%), which includes a high risk cohort of 72 pts with del17p, 25 paired samples with later follow up from the same cohort, and 94 relapsed patients, of which 50 were relapsed and refractory. Results: Overall coverage per mutation averaged >500x depth. We identified 945 variants (1.9 per pt) and in 83% of the pts a mutation was found. Clonal heterogeneity was assessed with mutations ranging from 3%-100% variant reads suggesting the presence of a significant number of subclones (e.g. 21% of mutations were in < 10% of reads). The mutation incidence was compared with and closely resembles the most recent MM comprehensive genomic data from the MMRF CoMMpass study: We compare here all pts sequenced by M3 P, untreated pts sequenced by M3 P and CoMMpass: KRAS (24%/23%/24%), NRAS (20%/20%/18%), DIS3 (13%/14%/10%), BRAF (9%/7%/6%), FAM46C (6%/6%/8%) and TRAF3 (6%/6%/7%). TP53 mutation incidence, however, was significantly increased in our cohort (14%/12%/4.2%), a difference explained by the inclusion of del17p (untreated) and relapsed refractory MM in panel sequenced pts, cohorts with elevated incidences of TP53 mutations (32% / 26% respectively). Potentially actionable targets include BRAF mutationsin 43 patients (9%), with druggable p.V600E in 19 or 5%, 8 pts (2%) with FGFR3 (p.R248C and p.G375C one patient each), p.R132 mutation in 4 out of 5 IDH1 (1%) and p.R172K IDH2 mutation in 1 of 3 (1%) pts. Mutations in the MAPK pathway (NRAS, KRAS, BRAF) were detected in 59% of pts, ranging from 36% untreated MM to 72% in refractory MM. Similarly, the CRBN/CUL4B/IKZF1/IKZF3/IRF4 pathway, important for IMiD function, harbored a significant enrichment of mutations in advanced disease (6% untreated vs 17% relapsed), including CRBN mutations (0.5% vs 7%). Nine of 17 IRF4 mutations were located at the p.K123R hotspot, with minor difference between early or late disease (1% vs 3%). Notably, in 8 of 9 pts with CRBN mutation and clinical information, all were unresponsive to IMiD therapy, supporting association of these mutations with resistance to IMiDs. Conversely, M3 P genes related to other SOC therapies, including NR3C1 (targeted by steroids) and 5 proteasome subunit genes (proteasome inhibitors), were rarely mutated across the cohorts not exceeding 1% mutation incidence for each gene. Significant differences in DIS3 and FAM46C mutation incidences were observed across cohorts: DIS3 mutations are more common in untreated pts with a 1.7 fold increased predominance (14% untreated and 8% treated). FAM46C has an expected incidence of 8% but was rarely mutated in untreated del17p high risk disease with only one of 100 patients harboring both mutations. The significance of this finding needs to be determined but implies a possible overlap in function. Finally we assessed impact on survival of the mutation variants identified in 142 untreated Mayo patients and found STAT3 mutations negatively impacting PFS (p=0.034) and OS (p=0.001). This gene is rarely mutated in MM (2% of the total cohort) thus the sample size was small and this finding needs further validation. Conclusion: We here describe 504 MM patients sequenced using the M3 P gene panel, which identified mutations in >80% of investigated patients, overlaps well with published whole exome sequence data and provides clinically relevant information. New findings were the high frequency of minor clones, the relative lack of overlap of del17 and FAM46C mutation, a higher frequency of DIS3 mutation at diagnosis compared to relapse, the prognostic significance of STAT3 mutation and the frequent presence of CRBN pathway mutation in drug resistant relapsed patients. Disclosures Sonneveld: Janssen-Cilag, Celgene, Onyx, Karyopharm: Honoraria, Research Funding; novartis: Honoraria. Mai:Janssen-Cilag: Other: Travel Grant; Onyx: Other: Travel Grant; Mundipharma: Other: Travel Grant; Celgene: Other: Travel Grant. Goldschmidt:Takeda: Consultancy, Membership on an entity's Board of Directors or advisory committees; Amgen: Consultancy, Membership on an entity's Board of Directors or advisory committees; Onyx: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Millenium: Honoraria, Research Funding, Speakers Bureau; Bristol-Myers Squibb: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Chugai: Honoraria, Research Funding, Speakers Bureau; Janssen-Cilag: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau. Knop:Celgene Corporation: Consultancy. Kull:Bristol-Myers Squibb: Membership on an entity's Board of Directors or advisory committees. Martinez-Lopez:Novartis: Honoraria, Research Funding; Bristol-Meyer Squibb: Honoraria; Celgene: Honoraria; Janssen: Honoraria. Einsele:Celgene: Consultancy, Honoraria, Research Funding, Speakers Bureau; Janssen: Consultancy, Honoraria, Research Funding, Speakers Bureau; Novartis: Consultancy, Honoraria, Speakers Bureau; Amgen/Onyx: Consultancy, Honoraria, Speakers Bureau. Raab:Novartis: Research Funding. Stewart:Oncospire Inc.: Equity Ownership; Celgene: Consultancy; Novartis: Consultancy; BMS: Membership on an entity's Board of Directors or advisory committees.

Abstract Abstract 3063 Background: The combination of Cyclophosphamide, Bortezomib, and Dexamethasone (CYBOR-D) is proven to be highly active and effective in multiple myeloma. (Reeder, Leukemia 2009) We aim to evaluate the safety and efficacy of this regimen in a separate plasma cell neoplasm, AL Amyloidosis. The primary endpoint of this study is hematologic response. Complete hematologic response is defined as normalization of the free light chain ratio with no evidence of a monoclonal protein by immunofixation. Partial hematologic response is defined as a 50% reduction in M-spike or absolute light chain level (Gertz Am J Heme 2006). Methods: We report a series of patients with symptomatic AL Amyloidosis who received treatment with a combination of Bortezomib (1.3mg/m2 on days 1, 4, 8, and 11 every 28 days or 1.5 mg/m2 weekly), Cyclophosphamide (300 mg/m2 orally weekly) and Dexamethasone (40 mg weekly). We include patients in this study regardless of autologous bone marrow transplant candidacy or previous treatment history. Results: Fifteen patients with AL amyloidosis received two to six cycles of CYBOR-D. The treatment history, bone marrow transplant candidacy prior to treatment, hematological response, and status of transplant after therapy are shown in table 1. Of note, 8 (53%) had symptomatic cardiac involvement all of whom had elevated levels of both cardiac biomarkers (Troponin T and B-natriuretic peptide). Complete hematological response occurred in 11 patients (73.3%) with partial hematological response in 3 patients (20.0%). One patient (6.6%) did not achieve a partial response but did receive autologous bone marrow transplant after treatment with CYBOR-D. Median time to response was 2 months. Six patients (40%) had objective evidence of kidney response to therapy with a greater than 50% decrease in proteinuria. Conclusions: CYBOR-D produces a rapid and complete hematological response in the majority of patients with AL amyloidosis regardless of previous treatment history or bone marrow transplant candidacy. Overall, it is well tolerated with few side effects that included peripheral neuropathy and infectious complications. Two patients originally determined to be not eligible for transplant improved sufficiently on CYBOR-D to become eligible and then went on to receive autologous bone marrow transplant. The retrospective nature and small sample size limit this study, and prospective, randomized studies are needed to further elucidate the role of this regimen in AL amyloidosis. Disclosures: Stewart: Millennium Pharmaceuticals, Inc.: Honoraria, Research Funding; Celgene: Honoraria. Fonseca:Amgen: Consultancy; Bristol-Myers Squibb: Consultancy; Celgene: Consultancy, Research Funding; Genzyme: Consultancy; Onyx: Research Funding; Otsuka: Consultancy; Medtronic: Consultancy.

Abstract Abstract 1954 Background: Carfilzomib (CFZ) is a novel, highly selective epoxyketone proteasome inhibitor that produces potent and sustained proteasome inhibition both in vitro and in vivo. CFZ appears to lack many of the off-target activities frequently associated with bortezomib (BTZ). This lack of off-target activity may account for observed differences in tolerability seen with CFZ including lack of significant neuropathy and minimal neutropenia and diarrhea. To date, single agent CFZ has been evaluated in Ph 1 and 2 studies in >600 patients, and the vast majority of patients treated had relapsed and/or refractory (R/R) MM. In these settings, CFZ has demonstrated durable single-agent activity and was well-tolerated in patients with advanced stage disease with co-morbidities including baseline neuropathy or renal insufficiency. Here we present the results of parallel safety analyses of patients from four Ph 1 and 2 studies with CFZ. Materials and Methods: The present safety analyses were based on data accumulated from patients enrolled in the following trials: PX-171-003 A0 (R/R MM), PX-171-003 A1 (R/R MM), PX-171-004 (relapsed MM), and PX-171-005 (R/R MM with varying degrees of renal function). In all studies, the treatment schedule was based on a 28-day cycle, dosing CFZ QDx2 each week for 3 weeks (Days 1, 2, 8, 9, 15, 16) with 12 days of rest. Doses of CFZ ranged from 15–20 mg/m2 in cycle 1 (005 [15 mg/m2], 003 A0 and A1, 004 [20 mg/m2]). In three studies CFZ was escalated to 27 mg/m2 after the first cycle, as tolerated (003- A1, 004-BTZ naïve subset and 005). In PX-171-005, low-dose dexamethasone was added in the majority of patients. Results: CFZ was well-tolerated by patients across the 4 studies analyzed. The most common treatment-emergent adverse events (AEs) included fatigue, anemia, nausea, dyspnea, and thrombocytopenia. Detailed descriptions of the incidence of treatment-related AEs (all Grades (G) in ≥25% of pts; ≥G3 in ≥5% of pts) across studies are presented in the table. Peripheral neuropathy (PN) occurred infrequently across all 4 studies (N= 517), with only 20 patients (3.9%) experiencing PN of any G and only 2 patients (0.4%) with G3 PN. Febrile neutropenia was likewise uncommon, occurring in only 3 patients (0.6%). Serious treatment emergent AEs (SAEs) occurring in ≥1% of patients and considered possibly/probably related to study drug across all 4 studies included: pneumonia (3.5%), congestive cardiac failure (2.5%), acute renal failure (1.7%), pyrexia (1.2%), and dyspnea (1%). Conclusions: Despite a substantial disease burden present in the patient populations described here, CFZ was well-tolerated by patients with MM across all studies examined. The excellent safety/tolerability profile of CFZ has permitted prolonged administration (in some cases over 24 mos of continuous therapy including extension study) with minimal dose modifications or discontinuations due to toxicity. The low levels of neuropathy seen with CFZ make this agent a potentially important treatment option for patients with pre-existing neuropathy from either underlying disease or prior neuropathic anti-myeloma therapy. Disclosures: Singhal: Celgene: Speakers Bureau; Takeda/Millenium: Membership on an entity’s Board of Directors or advisory committees, Speakers Bureau; Onyx: Research Funding. Siegel:Millenium: Consultancy, Honoraria; Celgene: Consultancy, Honoraria. Martin:Celgene: Honoraria; Onyx: Consultancy. Vij:Onyx: Honoraria. Wang:Celgene: Research Funding; Onyx: Research Funding; Millenium: Research Funding; Novartis: Research Funding. Jakubowiak:Millennium Pharmaceuticals, Inc.: Consultancy, Honoraria, Membership on an entity’s Board of Directors or advisory committees; Celgene: Consultancy, Honoraria; Centocor Ortho Biotec: Consultancy, Honoraria, Membership on an entity’s Board of Directors or advisory committees; Exelixis: Consultancy, Honoraria, Membership on an entity’s Board of Directors or advisory committees; Bristol-Myers Squibb: Consultancy, Honoraria, Membership on an entity’s Board of Directors or advisory committees. Lonial:Millennium: Consultancy, Research Funding; Celgene: Consultancy, Research Funding; Novartis: Consultancy, Research Funding; BMS: Consultancy, Research Funding; Onyx: Consultancy, Research Funding. Kukreti:Celgene: Honoraria; Roche: Honoraria; Ortho Biotech: Honoraria. Zonder:Millenium: Consultancy, Honoraria, Research Funding; Cephalon: Research Funding; Celgene: Honoraria. Wong:Onyx Pharmaceuticals: Employment. McCulloch:Onyx Pharmaceuticals: Employment. Kauffman:Onyx Pharmaceuticals: Employment. Niesvizky:Celgene: Consultancy, Membership on an entity’s Board of Directors or advisory committees, Research Funding, Speakers Bureau; Millenium: Consultancy, Membership on an entity’s Board of Directors or advisory committees, Research Funding, Speakers Bureau; Onyx: Consultancy, Research Funding. Stewart:Millennium: Consultancy; Celgene: Honoraria. Jagannath:Millenium, OrthoBiotec, Celgene, Merck, Onyx: Honoraria; Imedex, Medicom World Wide, Optum Health Education, PER Group: Membership on an entity’s Board of Directors or advisory committees, Speakers Bureau.

Abstract Abstract 303 Background: Carfilzomib (CFZ) is a novel proteasome inhibitor that binds its target selectively and irreversibly, resulting in greater and more sustained proteasomal inhibition compared to BTZ (Demo et al, Cancer Res 2007). CFZ overcomes BTZ-resistance in vitro (Kuhn et al, Blood 2007) and in a previous Phase 2 study (PX-171-003), single-agent CFZ achieved durable responses and maintained disease control [e.g. ≥ Stable Disease (SD)] in patients with progressive multiple myeloma (MM) despite treatment with essentially all available agents. PX-171-004 is an ongoing Phase 2 study of CFZ monotherapy in MM patients with relapsed or refractory disease following 1–3 prior therapies. Here we report updated data for the BTZ-treated cohort. Methods: Patients with relapsed or refractory (defined as < 25% response or disease progression during therapy) MM were enrolled and stratified based on prior BTZ exposure (e.g. BTZ-naïve and BTZ-treated). For the BTZ-treated cohort, tolerability and response to prior BTZ [≥ Minor Response (MR)] was not required. CFZ 20 mg/m2 IV was administered on Days 1, 2, 8, 9, 15 and 16 every 28 days, for up to 12 cycles. The primary endpoint was Overall Response Rate (ORR) [≥ Partial Response (PR)] by IMWG criteria. Secondary endpoints included Clinical Benefit Response (CBR = ORR + MR) and safety. Results: Thirty-five BTZ-treated patients were enrolled. Six (17%) patients had previously received BTZ exclusively as a single agent, 15 (43%) received BTZ as part of a chemotherapy combination and 10 (29%) received BTZ as part of a stem cell transplant (SCT) regimen. An additional 4 (11%) received BTZ in a chemotherapy combination as well as part of a separate transplant regimen. Other prior therapies included alkylators (89%), SCT (81%), thalidomide (69%), lenalidomide (37%), and anthracyclines (31%). Six (17%) patients had disease refractory to BTZ and 9 (26%) additional patients had discontinued BTZ due to toxicities. At baseline, 19 (54 %) patients had an ECOG score ≥ 1, 17 (49%) patients had neuropathy of Grade ≥ 1, 9 (26%) patients had impaired renal function (CrCl <60 mL/min) and 9 (26%) had diabetes. The median time since diagnosis was 3.6 years (range 1.2–13.2). To date, the mean number of CFZ doses administered was 29.3 (∼5 four-week cycles; range 4–72 doses, 0.7–12 cycles). Thirty-three patients who initiated therapy were evaluable for response per protocol. The ORR was 18% (6/33), including 1 CR and 5 PRs. An additional 4 (12%) patients had MR (CBR= 30%) and 13 (39%) had SD for ≥ 6 weeks. For evaluable patients who were either refractory or intolerant to their prior BTZ therapy, responses to CFZ included 1 PR and 1 MR and 8 SDs. The most common adverse events (AEs) (≥ 30% patients) were primarily Grades 1/2 and included fatigue (57%), nausea (54%), vomiting (37%), dyspnea (34%), diarrhea (34%), anemia (31%), increased creatinine (31%) and upper respiratory tract infection (31%). Grade 3/4 AEs occurring in ≥ 10% of patients were anemia (14.3%) and neutropenia (11.4%). There were no reports of febrile neutropenia. Dose modifications were rarely required. Peripheral neuropathy (PN) was uncommon (4 patients, 11%); only 1 patient had a Grade 3 event that lasted < 36 hours and did not result in missed doses or dose modification. None of the 9 patients with baseline renal impairment were discontinued for renal AEs. To date, 6 (17%) patients have completed the full 12-cycle protocol at the initial dose and schedule, 6 (17%) remain on study and 1 patient has received > 19 cycles on a recently initiated extended treatment protocol. Conclusions: In a BTZ-exposed population that includes BTZ treatment failures and significant comorbidities (e.g. diabetes, renal insufficiency, etc), the 18% ORR (CBR 30%) is notable for this steroid- and anthracycline-sparing regimen. Single-agent CFZ is well tolerated, even in patients with renal insufficiency, and both myelosuppression and PN are uncommon. These data support the continuing evaluation of CFZ as a safe and effective treatment option in MM. Disclosures: Siegel: Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Millennium: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Wang:Proteolix, Inc.: Research Funding. Stewart:Genzyme, Celgene, Millenium, Proteolix: Honoraria; Takeda, Millenium: Research Funding; Takeda-Millenium, Celgene, Novartis, Amgen: Consultancy. Kukreti:Celgene: Honoraria. Jakubowiak:Millennium Pharmaceuticals, Inc.: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Centocor Ortho Biotech: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Exelixis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Bristol-Myers-Squibb: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Jagannath:Millennium: Honoraria, Membership on an entity's Board of Directors or advisory committees; Merck: Honoraria, Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees. McDonagh:Proteolix: Research Funding. Belch:Ortho Biotech: Honoraria, Research Funding. Bahlis:Celgene: Honoraria, Speakers Bureau; Ortho Biotech: Honoraria, Speakers Bureau. Le:Proteolix, Inc.: Employment. Kunkel:Proteolix: Consultancy, Employment. Bennett:Proteolix: Employment. Kauffman:Proteolix, Inc.: Employment. Vij:Proteolix, Inc.: Consultancy, Research Funding.