ALBERT

Description: Background : Treatment for relapsed multiple myeloma (MM) has evolved with the availability of many novel agents; outcomes in patients with newly diagnosed MM have improved with IMiD® agents (lenalidomide [R] or pomalidomide) and proteasome inhibitor (PI) use. Regardless of autologous stem cell transplant, many patients receive R maintenance therapy (Jagannath, Blood Adv 2018; Palumbo, N Engl J Med 2012). However, there is a lack of data describing the nature of relapse and treatment choices for patients progressing on R maintenance therapy. Recent phase III data do not evaluate these patients who are relapsed or refractory to R; current treatment guidelines do not specifically recommend second-line (2L) treatment options for these patients (Laubach, Leukemia 2016). However, phase III data show that pomalidomide in combination with bortezomib and dexamethasone improves progression-free survival (PFS) (HR 0.54; P = 0.0027) in R-exposed and refractory patients, including those with 1 prior line (Richardson, J Clin Oncol 2018). The Connect MM Registry is a US, multicenter, prospective observational cohort study designed to examine diagnostic and treatment patterns, clinical outcomes and quality of life in patients with MM. For patients who received R maintenance therapy, we describe patterns of relapse, 2L treatment choice, and outcomes. Methods : From 250 sites, transplant eligible and ineligible adult patients ≤ 60 days from MM diagnosis were enrolled (N = 3011). Patients were treated at physicians' discretion and followed up for treatment and outcomes until early discontinuation or study end. Patients who relapsed during R maintenance therapy (≤ 15 mg; assessed by treating physician), were analyzed for baseline (BL) characteristics, nature of relapse, and 2L treatment. Patients with symptoms at time of relapse were defined as the presence of ≥ 1 CRAB (hyperCalcemia, Renal failure, Anemia, and Bone disease) criterion ± 60 d from PD; absence of CRAB criteria at PD in this window was considered nonsymptomatic relapse. Primary endpoint was PFS from start of 2L; safety (serious adverse events; SAE) from start of 2L was also assessed. Logistic regression analyses on all BL factors and factors before start of 2L treatment were performed to determine covariates differentiating comparator groups. Survival outcomes were analyzed using a Cox regression after adjusting for covariates. Results : Data cutoff: 1/15/18. Of 2938 treated patients, 1102 entered 2L, 236 having received R maintenance therapy in 1L. Of those patients, 52% (n = 123) and 47% (n = 112) experienced symptoms at time of relapse and nonsymptomatic relapse, respectively (data not available for 1 patient). The top ten 2L regimens are presented in the Table. Median duration of prior maintenance therapy (367 d [IQR: 577] vs 489 d [IQR: 599]) and time from first progression to start of 2L treatment (0.3 vs 0.3 mo) did not notably differ between nature of relapse groups. Prolonged median PFS from start of 2L was observed for patients receiving triplet+ (≥ 3 agents) vs doublet (≤ 2 agents) regimens (HR: 0.72; Figure 1). PFS was better for IMiD agent + PI group compared with PI (without IMiD agents) group (HR, 0.68; Figure 2). Results of sensitivity analyses and overall survival will be presented. SAEs occurred similarly among treatment groups: 42.6% with IMiD agent + PI, 34.5% with IMiD agent (without PI), and 35.8% with PI. Conclusions: This is the first description of relapse patterns, 2L treatment choice and survival outcomes after PD on R maintenance therapy in community-based patients. Nearly equal numbers of patients had symptoms at time of relapse and nonsymptomatic relapse on R maintenance therapy. After PD on R maintenance, approximately 50% of patients switched to PI regimens without IMiD agents, 25% continued with IMiD agent + PI regimens, and 25% continued in the IMiD agents group. Our data show PFS benefit for triplet+ over doublet treatment in 2L. Patients in the IMiD agent + PI group gained survival benefits over patients in the PI group. Further characterization of the patients continuing with IMiD treatment in 2L after R maintenance therapy relapse (~ 25% of patients) are ongoing. Follow-up with recently approved agents (elotuzumab, daratumumab) and their use in 2L is limited in this analysis. These data may be used to better inform treatment choices after relapse on R maintenance therapy. Disclosures Jagannath: Celgene: Consultancy; Merck: Consultancy; Multiple Myeloma Research Foundation: Speakers Bureau; Medicom: Speakers Bureau; Bristol-Myers Squibb: Consultancy; Novartis: Consultancy. Narang:Janssen: Speakers Bureau; Celgene: Consultancy, Speakers Bureau. Ailawadhi:Takeda: Consultancy; Amgen: Consultancy; Janssen: Consultancy; Pharmacyclics: Research Funding; Celgene: Consultancy. Rifkin:Celgene: Consultancy; Boehringer Ingelheim: Consultancy; McKesson: Equity Ownership; EMD Serono: Consultancy; Amgen: Consultancy; Takeda: Consultancy; Sandoz: Consultancy. Terebelo:Celgene: Consultancy; Janssen: Speakers Bureau; Takeda: Speakers Bureau; Pharmacyclics: Speakers Bureau. Toomey:Celgene: Consultancy; Myriad Genetics: Speakers Bureau; Dava Oncology: Other: Travel. Durie:Takeda: Consultancy; Janssen: Consultancy; Celgene: Consultancy; Amgen: Consultancy. Hardin:Celgene: Consultancy. Gasparetto:Janssen: Consultancy, Honoraria, Other: Travel; Bristol-Myers Squibb: Consultancy, Honoraria, Other: Travel; Takeda: Honoraria; Celgene: Consultancy, Honoraria, Other: Travel, Research Funding. Wagner:EveryFit: Consultancy; Gilead: Consultancy; Janssen: Consultancy. Omel:Takeda Oncology: Honoraria, Membership on an entity's Board of Directors or advisory committees; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees. Srinivasan:Celgene: Employment. Kitali:Celgene: Employment. Agarwal:Celgene Corporation: Employment, Equity Ownership. Abonour:Prothena: Research Funding; Takeda: Consultancy, Research Funding; Celgene: Consultancy, Research Funding.

Description: Background: While B-cell receptor (BCR) signaling is essential for the development, of normal B cells, its aberrant hyper-activation results in neoplastic transformation of B-lymphocytes. Recent investigations using small molecule inhibitors validate the BCR pathway as a valuable target. Bruton’s tyrosine kinase (BTK) is one of the components of a signaling hub that transduces signals from the BCR into the cell for its activation and has been shown to be a therapeutic target. Ibrutinib (PCI-32765), an irreversible BTK inhibitor has shown clinical efficacy in CLL, mantle cell lymphoma (MCL) and Waldenströms macroglobulinemia (WM). Ibrutinib binds to cysteine-481 of the BTK protein and blocks its phosphorylation, resulting in termination of BCR-mediated activation of cells with a concomitant induction of death. Despite the clinical success of ibrutinib, a high percentage of patients achieve only partial response and eventually acquire resistance to the drug, resulting in aggressive relapse of the disease. A mutation of Cys481-Ser in BTK (ibrutinib-BTK binding site) has been reported to be one of the reasons for the development of ibrutinib resistance (IR). To understand the mechanisms resulting in acquisition of IR, we developed preclinical models of IR in WM and MCL. Materials: Ibrutinib was obtained from Pharmacyclics, CA. Validated human WM models (BCWM.1, RPCI-WM1 and MWCL.1 cell lines) and human MCL models (Jeko-1 and Maver cell lines) were used for the study. Results: BTK was constitutively phosphorylated at Y223 and Y551 in all the cell lines tested and this was inhibited by ibrutinib in a dose dependent manner. Phosphorylation of other kinases in the cascade such as SYK (Y323 and Y525/526) and PLCg2 (Y759 and Y1217) were also inhibited while AKT phosphorylation at both Ser473 and Thr308 was consistently increased in presence of ibrutinib. Treatment with ibrutinib induced cell cycle arrest in the G1 phase by 24h followed by apoptosis. Cell growth assays (MTS assay) showed that BCWM.1 was the most sensitive cell line followed by MWCL-1, RPCI-WM1, Maver and Jeko-1. Exposure of WM and MCL cells for prolonged periods of time with progressively increasing concentrations of ibrutinib resulted in outgrowth of clones (IR WM and MCL cell lines) that were resistant to apoptosis with a slow growth rate as compared to wild type parental cells. IR cells attained 2 – 20 fold resistance to ibrutinib as compared to the respective parental lines as determined by MTS assay. Sequence analysis of the BTK gene in all the cell lines revealed no mutation in IR cells at Cys481 suggesting that in an acquired IR state, resistance to ibrutinib can be developed independent of BTK Cys481 mutation. Interestingly, we found p-BTK levels to be markedly reduced in IR cells. Ibrutinib reversal experiments suggested that while a continuous presence of ibrutinib is needed for inhibition of BTK phosphorylation, a stable IR state could be maintained (for 〉1 month) in the absence of ibrutinib. This suggested the cells reliance on a parallel survival pathway, independent of BTK phosphorylation. Focused mRNA (Nanostring nCounter assay) and immunoblot analysis revealed significant changes in the expression profiles of several cellular elements. These included transcription factors such as PU.1, IRF4, BLIMP1, BCL-6 b-catenin as well as the phosphorylated ERK1/2, STAT1 and 3 suggesting a reprogramming of critical cellular networks, which IR tumor cells might be utilizing to overcome ibrutinib-induced cytotoxicity. Importantly, we observed that IR cells retained high levels of p-AKT and showed an increase in expression of BCL2 family members, as well as BCL-2 itself. Treatment of IR cells with ibrutinib +/- MK2206 (AKT inhibitor), or ABT-199 (BCL-2 inhibitor), synergistically induced cytotoxicity in IR cells, suggesting the importance of these parallel survival pathways (AKT/BCL2) in maintaining an IR state. Conclusion: Here we demonstrate that in the absence of BTK Cys481 mutation, an IR state is associated with reprogramming of transcriptional networks countering ibrutinib-induced toxicity by activation of AKT and BCL-2. Our current data exposes multiple vulnerabilities within IR cells, which can be therapeutically exploited to potentially delay onset of IR, by targeting alternative oncogenic mechanisms that are activated in presence of sustained BTK inhibition. Disclosures No relevant conflicts of interest to declare.

Description: Background: Peripheral neuropathy (PN) is associated with multiple myeloma (MM) and often worsened with thalidomide (THAL) and vincristine (VCR) therapy. Bortezomib (BTZ) is a proteasome inhibitor approved for the treatment of MM that has been also shown to cause PN. An increased risk of BTZ-induced PN has been associated with the presence of both PN and diabetes mellitus (DM) before treatment. However, the incidence and characteristics of BTZ-induced PN among MM patients (pts) retreated with another BTZ-containing regimen is unknown. We analyzed the incidence, severity and risk factors for PN after treatment of MM pts with a second BTZ-containing regimen. Methods: Retrospective chart analysis. MM pts that had progressed from at least one prior BTZ-containing regimen and had received treatment with another BTZ-containing regimen were eligible. Pts had to have experienced PN during the course of the first BTZ regimen and could not have received therapy with THAL or VCR. The protocol was later amended to allow inclusion of pts without PN during their first BTZ treatment and those who had received THAL or VCR. Statistical significance was assessed using Fisher’s or McNemar’s tests as appropriate. The relationship between comorbidities, prior THAL or VCR treatment and PN grade after BTZ treatment and re-treatment was analyzed using a multivariate logistics regression model. All statistical analyses were two-sided and were performed at the 0.05 level of significance. Results: As of July 3, 2014, 83 pts have been accrued to the retrospective analysis, and 58 chart reviews have been completed. The median age of pts included in the analysis was 64 years (range: 31-84 years); 57% of the pts were male and 69% were Caucasian. Pts had received a median of 2 prior regimens (range: 2-10); 43% of the pts had received prior regimens containing THAL and 15% of those had also received therapy with VCR. Prior to the protocol amendment, the eligibility criteria required pts to have experienced PN after the first BTZ treatment; therefore, most pts included in this analysis (88%) had PN.During their first BTZ treatment, the most severe grade of PN experienced by the majority of the pts was grade 1 (N=34), followed by grade 2 (N=13) and grade 3 (N=4). A comparison of the symptoms assessed when pts had their most severe grade of PN during this treatment and the severity reported at its onset showed that PN worsened in only 16% of pts. Nearly half (48%) of pts showed no change in PN whereas symptoms improved or resolved in 15% and 9% of the pts, respectively. During treatment with the second BTZ-containing regimen, a comparable proportion of pts (N=44; 76%) reported having experienced PN. Among those experiencing PN upon re-treatment, the most severe grade of PN experienced by the majority of the pts (N=29) was also grade 1, followed by grade 2 (N=12) and grade 3 (N=3). During the second BTZ treatment, a comparison of the symptoms that pts had when PN was at its worst and those recorded at its onset demonstrated that PN worsened in only 7% of the pts. PN showed no change in 47%, improved in 15%, or resolved in 7% of the pts.Interestingly, 17% of the pts (N=10) who had reported PN while receiving their first BTZ-containing regimen did not report this complication during their second BTZ treatment, while 7% of the pts (N=4) experienced PN only upon re-exposure. There was no association between the incidence of PN during the first BTZ treatment and its incidence during re-treatment (p=0.1213) or between the severity of PN (defined as worsening vs. not worsening) after first BTZ treatment and its severity after BTZ re-exposure (p=0.1306). Fifty-four percent of the pts presented with comorbidities, including DM (26%), hypertension (HTN, 22%) and peripheral vascular disease (PVD, 13%). There were no associations between PN grade after BTZ treatment and prior THAL or VCR exposure (p=0.5569) or between PN grade and comorbidities (DM, p=0.6657; HTN, p=0.9966; PVD, p=0.9966). Similar results were found for BTZ re-exposure (THAL or VCR, p=0.8672; DM, p=0.4137; HTN, p=0.2033; PVD, p=0.9954). Conclusions: Results from this retrospective study show that the severity and incidence of PN did not change with a second BTZ-containing regimen. Comorbidities or prior therapy with other PN-inducing agents such as THAL or VCR did not significantly increase the risk of PN after BTZ re-treatment. Enrollment into the study continues and updated results will be presented at the meeting. Disclosures Berenson: Millennium: Consultancy, Honoraria, Research Funding, Speakers Bureau. Tabbara:Millennium: Speakers Bureau. Lutzky:Millennium: Speakers Bureau. Ailawadhi:Millennium: Consultancy. Moezi:Millennium: Speakers Bureau.

Description: Background: Deubiquitinating enzyme (DUB) inhibitors are an emerging class of compounds, which are increasingly being regarded for their anti-cancer activity and therapeutic potential. The 19S regulatory particle of the proteasome contains two DUBs, USP14 and UCHL5, which are critical for the proper unfolding and deubiquitination of proteins prior to their entry into the 20S proteasome β-catalytic core. In B/plasma cell malignancies such as Waldenströms macroglobulinemia (WM) and multiple myeloma (MM), protein homeostasis and optimal proteasome functionality are paramount for tumor survival. This is evidenced by the success of 20S proteasome inhibition with bortezomib and carfilzomib, which have demonstrated remarkable clinical benefit in patients with WM or MM. As such, the proteasome degradation pathway represents a highly attractive and clinically validated, yet still largely unexplored therapeutic target. Here, we provide first evidence of the cytotoxic effects and molecular sequelae associated with a novel 19S proteasome DUB inhibitor, VLX1570, which selectively targets USP14 and UCHL5, in preclinical models of B/plasma cell cancers and their drug resistant tumor subclones. Materials: VLX1570 was obtained from Vivolux AB, Sweden. Bortezomib was purchased from Sellekchem, Houston TX. Human myeloma cell lines (OPM2, U266, KMS11), human WM cell lines (BCWM.1, MWCL-1 and RPCI-WM1), their respective bortezomib-resistant (BR) subclones as well as ibrutinib-resistant (IR) derivatives of BCWM.1 and RPCI-WM1 were used in experiments (total n=12). Peripheral blood mononuclear cells (PBMCs) from healthy donors were used to assess for cytotoxicity of VLX1570 in non-tumor cells. Results: A 72hr MTS assay first established sensitivity of plasma cell cancer models towards VLX1570, including drug resistant subclones (EC50 range, 20 – 90nM). Next we assessed whether loss of viability was due to apoptosis and observed dose-dependent annexin-V staining in ~50 – 70% of wild-type MM and WM cells, ~45 – 55% in corresponding BR models and ~50% in IR subclones when exposed to VLX1570 (100nm – 500nM) for 24hrs. VLX1570 was tested at similar concentrations in PBMCs and induced minimal cell death. To understand if VLX1570-induced apoptosis was mitochondrial mediated, we assessed mitochondrial outer membrane permeability (MOMP) in all plasma cell cancer models treated with the DUB inhibitor (100 – 500nM) and found a dose-dependent increase in MOMP (p

Description: Background: There is a significant variation in disease incidence and outcomes among Multiple Myeloma (MM) patients (pts) from different ethnic backgrounds. Currently, there is a paucity of data regarding the influence of demographics and ethnicity on behavioral patterns of pts, their attitudes, beliefs, and knowledge about MM and its treatment, which could in turn affect outcomes. We conducted a questionnaire-based study to examine behavioral patterns of MM pts, especially focusing on ethnic minorities and how this may impact patient awareness and symptom complex related to the disease and its treatment. Methods: Apaper-basedquestionnaire consisting of 61 questions encompassing four broad categories was provided to participating pts at the University of Southern California Medical Centers. These included demographics, disease/treatment related quality of life (QoL), satisfaction regarding treatment, and satisfaction regarding treating physician/healthcare staff. Information on clinical characteristics and MM-related treatment was collected through an IRB-approved protocol. Pts were stratified by age, gender, and ethnicity (Hispanics vs. Non-Hispanics). Any missing patient responses were withdrawn from the final analysis of that question. Categorical and continuous variables were compared among groups using Chi-square and Kruskal-Wallis tests, respectively. All statistical analysis utilized SAS software (v9.3) with a two-sided significance level of 0.05. Results: A total of 89 pts (males: 40, females: 49) from March 2012 to October 2013 responded to the questionnaire of the 100 pts that were consented (81%). Median age was 59 (range: 23-81) years and 43 (48%) pts were Hispanic while 46 (52%) were Non-Hispanic. Baseline clinical characteristics are shown in Table 1A. As compared to Non-Hispanics, Hispanic pts were less likely to have completed college (70% vs. 30%, p

Description: Background: Chimeric antigen receptor T-cell (CAR-T) therapy has revolutionized the treatment of relapsed/refractory B-cell lymphoid malignancies. Axicabtagene ciloleucel (axi-cel), an anti-CD19 CAR-T not only targets the malignant B-cell, but can potentially also target and eliminate normal B-cells. This can interfere with the normal B-cell repertoire, compromising host humoral immunity such as decreased titers of common vaccines (DTaP, MMR). To assess if this was a clinically significant problem, we evaluated all recipients of axi-cel at our center between 6/2018 through 7/2019. Patients and methods: For patients who received commercial axi-cel, humoral immunity was evaluated both quantitatively [absolute lymphocyte count (ALC)] as well as qualitatively by serology titers [IgG antibodies (Abs)] for diphtheria, tetanus, pertussis, measles, mumps, and rubella, and total Immunoglobulin G (IgG) levels. Data was collected within 30 days prior to CAR-T infusion, then at day +30 and between days +60 and +100 after CAR-T infusion. Results: We identified 10 patients (males = 5, 50%), with a median age of 49.9 years (range 30-65) who received commercial axi-cel during the study period. Patient characteristics and indications for CAR-T therapy are shown in Table 1; the cohort represented a heavily pre-treated aggressive B-cell lymphoma patient population. Baseline information on antibody (Ab) titers was available in 8 patients. At baseline, all patients had positive tetanus IgG Abs (≥0.01 IU/mL), 7 had positive diphtheria IgG Abs (≥0.01 IU/mL), 6 had positive measles IgG Abs (≥ 1.1 AI), 5 had positive rubella IgG Abs (≥ 1.0 AI), 3 had positive mumps IgG Abs (≥ 1.1 AI). None of the patients had a positive pertussis IgG Abs (≥100 IU/mL). At follow-up, all patients with positive Ab at baseline maintained titers in the positive range at day +30 and between days +60 and +100 (Figure 1). None of the patients demonstrated a clinically meaningful decrease in Abs titers, despite a drop in ALC and IgG levels (table 2). Conclusions: Albeit a small sample size, IgG Ab titers for diphtheria, tetanus, measles, mumps, and rubella did not appear to be affected by axi-cel at a short interval follow-up after infusion (up to day +100). We plan to extend this analysis in a larger cohort with a longer-term prospective follow-up to validate our findings, especially in light of dropping absolute lymphocyte counts and IgG levels. Disclosures Ailawadhi: Celgene: Consultancy; Amgen: Consultancy, Research Funding; Cellectar: Research Funding; Janssen: Consultancy, Research Funding; Takeda: Consultancy; Pharmacyclics: Research Funding. Foran:Agios: Honoraria, Research Funding. Tun:Celgene: Research Funding; Curis: Research Funding; TG Therapeutics: Research Funding; Mundi-pharma: Research Funding; DTRM Biopharma: Research Funding; BMS: Research Funding. Chanan-Khan:Pharmacyclics: Research Funding; Merck: Research Funding; Jansen: Research Funding; Mayo Clinic: Employment; Ascentage: Research Funding; Millennium: Research Funding; AbbVie: Research Funding; Xencor: Research Funding. Kharfan-Dabaja:Daiichi Sankyo: Consultancy; Pharmacyclics: Consultancy.

Description: Introduction Immunoglobulin M monoclonal gammopathy of undetermined significance (IgM MGUS) is a relatively common pre-malignant condition that may progress to Waldenstrom macroglobulinemia (WM), an incurable low-grade non-Hodgkin lymphoma. The acquisition of genomic alterations in a multistep process of progression is likely a central mechanism responsible for the progression of IgM MGUS to WM, leading to increased tumor burden and end-organ damage. The exact role of the immune system in this process is still poorly characterized. The modulation of the immune system by malignant cells leading to anti-lymphoma immunity or immune evasion is a well-stablished principle associated with lymphoma survival and progression, respectively. The understanding of the pathobiology of IgM MGUS and WM has grown significantly over the last few years; however, most of the past research has focused on genetics and flow cytometric analysis of malignant cells. The introduction of CyTOF, a novel platform coupling mass spectometry with single-cell flow cytometry using antibody-metal isotope pairs, has allowed a broader single-cell analysis and the study of functional profiles. We here report the use of CyTOF technology to comprehensively profile the immune system of patients with IgM MGUS and WM. Methods Viably-cryopreserved (DMSO 10%) single-cell suspensions containing peripheral blood mononuclear cells from 15 patients (WM n=9 and IgM MGUS n=6) were used in this study. Recovered cells (1-3 x 106 per sample) were stained with a 30-parameter surface protein CyTOF panel designed to characterize multiple cell types and profile the immune system. Nucleated cellular events were identified using a DNA intercalator conjugated to natural abundance iridium (191Ir and 193Ir). Cisplatin (195Pt) was used for dead-live cell discrimination and calibration beads containing natural abundance cerium (140/142Ce), europium (151/153Eu), holmium (165Ho), and lutetium (175/176Lu) were used for normalization of the instrument signal. CyTOF analysis of normalized files was carried out using the Astrolabe Diagnostics platform. Cell clusters were assigned using the FlowSOM package and differential abundance analysis was performed using the edgeR package. Analysis is adjusted for multiple comparisons. Results The median live single-cell count for the entire cohort was 573,300 (range 50,681 to 869,727), representing a median of 81% (range 39% to 87%) of the total event counts [median 820,800 (range 130,452 to 1,000,000]. The cell count and the proportion of event count was similar in patients with WM or IgM MGUS. T cells represented 45.8% of the total events; granulocytes represented 31.3%; NK cells represented 8.6%; monocytes represented 8.1%; B cells represented 2.4% of the total events for the entire cohort. Figure 1 shows a heat map of different immune cell sub-types proportion per patient sample. A difference was noted in the proportion of monocytes (CD14+, CD16+) and B-cells when comparing patients with IgM MGUS and WM (figure 2). Patients with WM had a higher proportion of monocytes compared to IgM MGUS patients (p=0.05). A higher proportion of B-cells was noted in patients with IgM MGUS when compared to WM (4.2% vs 0.6%, p=0.01). When B-cells were sub-classified as naïve, transitional, non-switched memory, switched memory, and plasmablasts, the proportion of non-switched memory B-cells was higher in IgM MGUS compared to WM (p=0.05). While the results of this pilot study suggest important differences between IgM MGUS and WM as regards the immune repertoire, confirmatory studies are in progress in a larger cohort of patients. Conclusion To our knowledge, this is the first study of mass cytometry in patients with WM and IgM MGUS patients. A higher proportion of monocytes and lower proportion of memory B-cells was noted in patients with WM compared to IgM MGUS. CyTOF study of the immune profile in these patients is feasible and can potentially uncover relationships between cell types not typically associated with the disease progression continuum (IgM MGUS to WM). While definitive conclusion cannot be made using this dataset due to the small sample size, CyTOF is a powerful tool in the study of the immune profile of WM patients. Disclosures Gertz: Amgen: Consultancy; Abbvie: Consultancy; Apellis: Consultancy; annexon: Consultancy; spectrum: Consultancy, Honoraria; Teva: Consultancy; Alnylam: Honoraria; Physicians Education Resource: Consultancy; Ionis: Honoraria; janssen: Consultancy; celgene: Consultancy; Prothena: Honoraria; Research to Practice: Consultancy; Medscape: Consultancy. Kapoor:Celgene: Research Funding; Takeda: Research Funding. Ailawadhi:Takeda: Consultancy; Amgen: Consultancy; Janssen: Consultancy; Celgene: Consultancy; Pharmacyclics: Research Funding. Reeder:Affimed: Research Funding. Ansell:Seattle Genetics: Research Funding; Regeneron: Research Funding; Takeda: Research Funding; Pfizer: Research Funding; Merck & Co: Research Funding; Trillium: Research Funding; Affimed: Research Funding; LAM Therapeutics: Research Funding; Celldex: Research Funding; Bristol-Myers Squibb: Research Funding.

Description: Background: Combinations of alkylating agents with proteasome inhibitors have demonstrated efficacy in newly diagnosed and relapsed multiple myeloma (MM), with melphalan or cyclophosphamide combinations being some of the commonly used regimens for initial treatment of MM. Ixazomib (Ixa) is an oral proteasome inhibitor that is approved for use in combination with lenalidomide for patients with relapsed MM. We examined if Ixa can be effectively combined with cyclophosphamide (Ctx) in order to develop a less expensive, all oral regimen for patients with relapsed MM. Patients and Methods: Patients with relapsed MM, who were proteasome inhibitor naïve OR have received less than 6 cycles of therapy with bortezomib and had a better than PR with no progression at the time of discontinuation, were enrolled. The primary objective was to determine overall response rate (ORR). Treatment consisted of Ixa 4mg PO days 1, 8, 15; Ctx 300 mg/m2 PO days 1, 8, 15, 22 and dexamethasone (Dex) 40 mg PO weekly in a 28-day cycle. Overall, 37 patients were accrued; data on 33 eligible patients were available for analysis as of July 18, 2019. Results: The median age was 71 (48-89), 61% were male and the median duration from diagnosis was 46 months (mos). Median number of prior lines of therapy was 4 (range 1-5), 76%, 42% and 67% respectively had a prior IMiD, proteasome inhibitor or stem cell transplant, respectively. At data cutoff, 22 (67%) had progressed, 4 (12%) had died and the median follow up of those alive was 21.3 mos. Fourteen patients are still receiving treatment, with median of 8.5 cycles. Most common reason for treatment discontinuation was disease progression (10 pts; 53%). The ORR was 60% including 6% CR and 24% VGPR. The median event free survival was 11.3 mos (95%CI: 9.0 - 26.8). Overall, 401 cycles have been administered across the study, with dose modifications/ hold required for Ixa, Ctx, and Dex in 9 (27%), 14 (42%), and 22 (67%) patients respectively, the most common reason being hematologic toxicity. A grade 3 or higher adverse event at least possibly attributed to the study drugs was seen in 77% of patients, hematologic in 67% and non-hematologic in 30%. (Table 1) The most commonly observed hematologic toxicities included thrombocytopenia, neutropenia, lymphopenia and anemia; for non-hematologic was nausea, diarrhea, peripheral neuropathy toxicity and fatigue. Conclusions: The combination of Ixa, Ctx and Dex (ICd) offers a convenient, all oral regimen for treatment of relapsed disease not refractory to proteasome inhibitors. The regimen has good efficacy in this group f heavily pretreated patients, with an acceptable toxicity profile. Disclosures Lacy: Celgene: Research Funding. Gertz:Ionis: Honoraria; Spectrum: Honoraria, Research Funding; Janssen: Honoraria; Celgene: Honoraria; Prothena: Honoraria; Alnylam: Honoraria. Ailawadhi:Takeda: Consultancy; Janssen: Consultancy, Research Funding; Cellectar: Research Funding; Pharmacyclics: Research Funding; Amgen: Consultancy, Research Funding; Celgene: Consultancy. Bergsagel:Janssen Pharmaceuticals: Consultancy; Celgene: Consultancy; Ionis Pharmaceuticals: Consultancy. Fonseca:AbbVie, Amgen, Bayer, Celgene, Kite, Janssen, Juno, Merck, Pharmacylics, Sanofi, Takeda: Other: Consultant/Advisor; Prognosticatin of MM based on Genetic Categorization by FISH: Patents & Royalties; Adaptive Biotechnologies: Other: Scientific Advisory Board. Dingli:alexion: Consultancy; Janssen: Consultancy; Millenium: Consultancy; Rigel: Consultancy; Karyopharm: Research Funding. Kapoor:Amgen: Research Funding; Takeda: Honoraria, Research Funding; Glaxo Smith Kline: Research Funding; Sanofi: Consultancy, Research Funding; Celgene: Honoraria; Cellectar: Consultancy; Janssen: Research Funding. Chanan-Khan:AbbVie: Research Funding; Pharmacyclics: Research Funding; Xencor: Research Funding; Merck: Research Funding; Jansen: Research Funding; Mayo Clinic: Employment; Ascentage: Research Funding; Millennium: Research Funding. Larsen:Janssen Oncology: Honoraria, Membership on an entity's Board of Directors or advisory committees; Takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees. Russell:Imanis: Equity Ownership. Stewart:Roche: Consultancy; Seattle Genetics: Consultancy; Takeda: Consultancy; Ionis: Consultancy; Janssen: Consultancy, Research Funding; Oncopeptides: Consultancy; Ono: Consultancy; Amgen: Consultancy, Research Funding; Bristol Myers-Squibb: Consultancy; Celgene: Consultancy, Research Funding. Kumar:Celgene: Consultancy, Research Funding; Janssen: Consultancy, Research Funding; Takeda: Research Funding.

Description: Abstract 2771 Background: NIL is a potent, highly selective Bcr-Abl kinase inhibitor approved for newly diagnosed adult pts with Philadelphia-chromosome positive (Ph+) CML-CP and in Ph+ CML-CP and accelerated-phase pts who are resistant or intolerant to IM. Achieving complete cytogenetic response (CCyR) and major molecular response (MMR, 3-log reduction of Bcr-Abl transcript level from the baseline mean) are favorable prognostic factors for CML. This multicenter, open-label study (ENABL) was designed to explore nilotinib Bcr-Abl effects in pts with CCyR but who have suboptimal molecular response to IM. Methods: This study evaluates change in Bcr-Abl trends in 2 groups of CML-CP pts (total n = 18) who achieved CCyR but have suboptimal molecular response to IM defined as: (Group 1) treated ≥ 1 year with IM, but Bcr-Abl transcript levels did not reach ≤ 0.1% on the international scale (IS) (MMR); or (Group 2) 〉 1-log increase in Bcr-Abl transcript levels from best response regardless of IM treatment duration. Pts are treated with NIL 300 mg twice daily for ≥ 1 year. RQ-PCR analysis is performed by a central lab at screening, then every 3 months (mos) for Group 1. Group 2 pts are monitored by RQ-PCR monthly for the first 3 mos, then every 3 mos. The 1° end point is change in Bcr-Abl transcript levels from a standardized baseline value by RQ-PCR at 12 mos. The data cutoff date for this analysis was June 30, 2011. Results: Eighteen pts (Group 1, n = 17; Group 2, n = 1) have been treated with NIL for a median of 17 mos on study (range 3–34 mos). Thirteen pts have been treated for ≥ 6 mos and 10 for ≥ 12 mos. One pt was deemed ineligible due to lack of evidence of CCyR at baseline but is included in the analysis because there was at least 1 post-baseline evaluation performed. The remaining 17 pts had CCyR at baseline. Before enrollment, pts were treated with at least 400 mg once-daily IM; the mean dose of prior IM treatment was 487 mg/day (range 342–786 mg/day). Median duration of prior IM treatment was 3.4 yrs (range 1.3–10.2 yrs). Three pts had prior interferon treatment. All 18 pts were treated for ≥ 3 mos and had ≥ 1 post-baseline RQ-PCR result. Overall, 15 of 18 evaluable pts (83%) achieved MMR during treatment; 10 pts by 3 mos, 1 pt by 4.5 mos (measured at end of study), 1 pt by 6 mos, 2 pts by 9 mos, and 1 pt by 30 mos (Figure 1). The 3 pts who did not reach MMR at any point were only followed for up to 3 mos before discontinuing from the trial but showed a decreasing Bcr-Abl trend. Overall, pts achieved a median log reduction of PCR transcript levels of 3.1 (0.08% IS) at 3 mos; median 3.3-log reduction (0.05% IS) at 6 mos, and median 3.5-log reduction (0.035% IS) at 9 mos. Four pts had 〉 4-log (≤ 0.01% IS) reduction in Bcr-Abl; of these, 2 pts reached 〉 4.5-log (≤ 0.0032% IS) reduction in Bcr-Abl at least once during the study. Median Bcr-Abl transcript log reduction at 12 mos was 3.6 (0.025% IS, 1° end point) for 10 evaluable pts. All these pts reached MMR during NIL treatment; 9 pts by 12 mos, 1 pt after 30 mos. NIL was well tolerated and brief dose interruptions were sufficient to manage most adverse events (AEs). Seven of 18 pts were dose reduced for NIL-related AEs and re-escalated if the patient recovered from the AEs. Patients were permitted to dose escalate to 400 mg b.i.d. per physician's discretion if MMR was not achieved after 6 mos (n = 1). The Grade 3 AEs reported include 2 cases of rash and 1 case each of pneumonia, squamous cell carcinoma, bladder prolapse, uterine prolapse, bradycardia, hypertension, hyperbilirubinemia and hypophosphatemia. The rashes and bradycardia were suspected to be related to NIL. No Grade 4 AEs were reported. The median dose intensity was 600 mg/day (range 300–683 mg/day). Five pts were discontinued from the study (3 due to abnormal laboratory values, 1 due to an AE, and 1 due to protocol violation). No pts who experienced QTcF changes had differences 〉 33 msec from baseline. No QTcF prolongation 〉 500 msec was observed. Conclusions: NIL treatment results in high molecular response rates in CML-CP pts with suboptimal molecular responses to IM. Overall 83% of pts who switched to NIL achieved MMR, and the median Bcr-Abl log reduction for pts who reached 12 mos on study was 3.6 (0.025% IS). The IRIS study has shown that MMR rates increase with time in pts treated with IM (Hughes Blood 2010); however, this study appears to demonstrate that MMR is achieved relatively quickly in suboptimal molecular IM-treated pts when switched to NIL. Disclosures: Ailawadhi: Novartis Pharmaceuticals: Consultancy, Speakers Bureau. Miller:Incyte: Research Funding; Novartis: Honoraria, Research Funding, Speakers Bureau. Akard:Eisai: Speakers Bureau; Bristol Myers-Squibb: Speakers Bureau; Novartis: Speakers Bureau; Millenium: Speakers Bureau; Chemgenex: Consultancy. Ericson:Novartis Pharmaceuticals Corporation: Employment, Equity Ownership. Lin:Novartis: Employment, Equity Ownership. Radich:Novartis: Consultancy, Research Funding, Speakers Bureau; Pfizer: Consultancy, Speakers Bureau; Bristol-Myers Squibb: Consultancy, Speakers Bureau. DeAngelo:Novartis: Consultancy; Bristol-Myers Squibb: Consultancy.