Abstract: Background: For multiple myeloma (MM) patients, depth of response after induction therapy and after autologous hematopoietic stem cell transplantation (AHCT) has been shown to be important for progression free (PFS) and overall survival (OS) in some studies. Furthermore, the impact of minimal residual disease (MRD) on outcomes and treatment decisions has been widely discussed. We aimed to evaluate outcomes by depth of response after induction and AHCT. Methods: MM patients who received their first AHCT within 1 year of starting induction were identified from the institutional registry. MRD was assessed by non-10 color flow cytometry. Response was defined by the International Myeloma Working Group criteria. Summary statistics were used to describe the population. Kaplan-Meier methodology estimated PFS and OS by response status pre-AHCT and at post-AHCT restaging. Results: Between 2012 - 2014, 182 MM patients met our inclusion criteria, with 83% alive at last follow-up. The median age at AHCT was 60 years (range 29-76) with 57% male. By the International Staging System (ISS), 50% were stage I, 26% stage II, and 24% stage III. High risk cytogenetics were detected in 24%. Isotype was IgG in 55%, IgA 21%, Kappa Free Light Chain (KFLC) 11%, and lambda FLC (LFCL) 9%. First induction therapy included bortezomib in 90% and lenalidomide in 79%. Median time to AHCT was 5.5 months (range 2.8-11.7). The median follow-up from AHCT was 3.7 years (range 0.22 - 4.6 years), with 84% of patients receiving lenalidomide maintenance, and 9% receiving an additional autologous or allogenic transplant at relapse. Response prior to the initial AHCT was a complete remission (CR) in 13.7% (MRD negative 6.6%, positive 4.4%, unknown 2.7%), very good partial remission (VGPR) 38%, partial remission (PR) 40%, stable disease (SD) 5%, and progressive disease (PD) 4%. At post-AHCT restaging, responses had improved to 42% CR (MRD negative 23%, positive 6%, unknown 13%), 35% VGPR, 19% PR, 2% SD, and 3% PD. Median PFS from AHCT for the entire cohort was 3.2 years (95% CI 2.4 - 4 years) with 1-year and 3-year PFS 85% and 52%, respectively. Median OS was not reached (NR) (95% CI 4.4 years - NR) with 1-year and 3-year OS 97% and 88%, respectively (Figure 1). PFS from AHCT was significantly longer in patients with an MRD negative CR prior to AHCT with median PFS not reached (95% CI 1.7 - NR) compared to MRD positive/unknown CR, VGPR, and ≤ PR [3.64 years (95% CI 1.09-3.64), 3.46 years (95% CI 2.4 - NR), and 2.44 years (1.68-3.56 years), respectively, p=0.048] (Figure 2A). From post-AHCT restaging, PFS was also significantly longer in patients with an MRD negative CR prior to AHCT with median PFS not reached compared to MRD positive/unknown CR, VGPR, and ≤ PR [3.49 years (95% CI 0.86-3.49), 3.56 years (95% CI 2.5 - NR), and 2.4 years (1.6-3.33 years), respectively, p=0.026] (Figure 2B). However, there was no difference in PFS based on the post-AHCT restaging with median PFS in MRD negative CR, MRD positive/unknown CR, VGPR, and ≤ PR of 3.49 years (95% CI 2-NR), not reached (95% CI 1.4-NR), 2.96 years (95% CI 1.7-NR), and 2.86 years (95% CI 1.7 - NR) (p=0.78, Figure 2C), respectively. OS from AHCT was not significantly different by pre-AHCT response, and the median was not reached in any group (p=0.33, Figure 3A). Finally, the median OS from post-AHCT restaging by pre-AHCT response or by post-AHCT response was also not reached in any group (p=0.32 and 0.31, respectively; Figure 3B & C). Conclusion: For MM patients, AHCT deepened responses and increased the CR rate. We were unable to show a significant difference in outcomes at post AHCT restaging, which may be due to the effect of maintenance therapy, the small numbers of MRD negative patients, or the sensitivity of the MRD assay available during this time period, though potentially show that MRD positive patients do as well as MRD negative patients after AHCT. We plan to add additional patients treated in the more recent years who were assessed by more sensitive methods. Disclosures Shah: Janssen: Research Funding; Amgen: Research Funding. Korde:Amgen: Research Funding. Lesokhin:Janssen: Research Funding; Genentech: Research Funding; Takeda: Consultancy, Honoraria; Serametrix, inc.: Patents & Royalties: Royalties; Bristol-Myers Squibb: Consultancy, Honoraria, Research Funding; Squibb: Consultancy, Honoraria. Mailankody:Janssen: Research Funding; Physician Education Resource: Honoraria; Takeda: Research Funding; Juno: Research Funding. Smith:Celgene: Consultancy, Patents & Royalties: CAR T cell therapies for MM, Research Funding. Landgren:Takeda: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Pfizer: Consultancy; Merck: Membership on an entity's Board of Directors or advisory committees; Karyopharm: Consultancy; Janssen: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Amgen: Consultancy, Research Funding; Celgene: Consultancy, Research Funding.

Abstract: Background: Monoclonal immunoglobulin deposition disease (MIDD) is a rare complication of plasma cell dyscrasias in which deposition of immunoglobulin light and/or heavy chains results in organ dysfunction, most commonly affecting the kidneys. MIDD can present with new onset hypertension, hematuria, renal insufficiency and proteinuria. The rarity of MIDD contributes to the uncertainty regarding optimal therapy (typically targeting the clonal plasma cells), and the relationship between hematologic response and renal outcome. We report here the experience at Memorial Sloan Kettering Cancer Center and New York Presbyterian Hospital/Weill Cornell Medical Center. Methods: An electronic query of pathology records was performed to identify patients with a biopsy-proven diagnosis of MIDD. Patients were eligible for inclusion in this analysis if they had received treatment and had been subsequently followed at either institution. A retrospective review of clinical records extracted patients' baseline characteristics and treatment history. Hematologic responses were assessed according to International Myeloma Working Group uniform response criteria (Kumar, S. et al 2016 Lancet Oncol 17(8): e328-346) and renal organ responses were evaluated based on changes in serum creatinine (SCr), and proteinuria, a modification of criteria previously reported (Kourelis, T. V., et al 2016, Am J Hematol 91(11): 1123-1128.; Nasr, S.H. et al. 2009, J Am Soc Nephrol 20(9): 2055-2064. The primary objective was to determine the rate of hematologic response after initial therapy. Secondary objectives included: (i) Estimation of renal response rate; (ii) Identification of risk factors associated with renal response using the Wilcoxon Rank Sum and Fisher's Exact Tests. Results: Among 54 patients identified who were diagnosed and started treatment between 1/1999 and 1/2016, 29 met criteria for inclusion. Baseline characteristics at diagnosis included: Median age of 50 (range, 32-79); 17 (59%) were male; 22 (75%) had hypertension. Renal parameters at diagnosis: median SCr of 2.4 mg/dl (range, 0.4-19), median CrCl 23 ml/min (range, 4-131), median proteinuria 2383.7mg/24h (range 4.7-13,000), nephrotic-range proteinuria syndrome in 13 (45%), hematuria in 4/25 pts (16%; 4 unknown), 7 were on hemodialysis (HD) prior to initiation of therapy, and 26 (90%) patients had monoclonal kappa light chain deposits. Hematologic parameters included median free light chain ratio of 67.9 (2.8-1179.0), detectable M-spike in 11 pts with a mean level of 0.6 g/dL and median bone marrow plasmacytosis of 20% (range, 0-90%). Induction treatment regimens included bortezomib in 18 (62%), lenalidomide in 6 (21%), cyclophosphamide in 8 (28%), and 21 (73%) underwent autologous stem cell transplant (ASCT) during the course of their treatment. Outcomes are shown in Table 1. Hematologic response among the 29 pts at completion of first line therapy included an overall response rate (ORR) of 93% with sCR (N=14, 48%); CR (N=5, 17%), VGPR (N=6, 20%), PR (N=2, 6.9%), Not available (N=2, 7%). Renal response (Table 1) among 29 patients included CR (N=9, 31%), PR (N=14, 48%) and End Stage Renal Disease (ESRD) (N=6, 21%). Among 7 patients on HD at baseline, 3 remained on HD despite treatment, while 4 stopped HD after treatment, 2 as a result of the treatment and 2 after renal transplant. 3 patients progressed to ESRD and required HD during treatment. Baseline beta-2 microglobulin (B2M), SCr, and eGFR at diagnosis were factors associated with renal response (p 〈 0.05). Hematologic response (CR vs. non-CR) was not associated with renal response (p=0.68) in this cohort. Conclusions: In this cohort, we observed a high rate of hematologic response (65.5% reaching CR) to upfront treatment regimens. A majority of patients received bortezomib-based regimens and ASCT. We observed a large proportion of patients whose renal impairment from MIDD improved significantly after receiving therapy directed at the underlying clonal neoplasm, with 75.8% reaching PR or better, nearly a third of patients achieving a renal CR, and 2/7 patients on HD at diagnosis discontinuing HD after treatment. Our experience presented here serves to inform the treatment approach of patients with MIDD. Given the scarcity of outcome data in MIDD, especially in the era of novel anti-myeloma therapy, prospective studies to optimize the management of these patients are needed. Disclosures Rossi: Celgene: Consultancy. Smith:Celgene: Consultancy, Patents & Royalties: CAR T cell therapies for MM, Research Funding. Korde:Amgen: Research Funding. Mailankody:Janssen: Research Funding; Juno: Research Funding; Physician Education Resource: Honoraria; Takeda: Research Funding. Lesokhin:Squibb: Consultancy, Honoraria; Bristol-Myers Squibb: Consultancy, Honoraria, Research Funding; Takeda: Consultancy, Honoraria; Genentech: Research Funding; Janssen: Research Funding; Serametrix, inc.: Patents & Royalties: Royalties. Landgren:Janssen: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Karyopharm: Consultancy; Merck: Membership on an entity's Board of Directors or advisory committees; Pfizer: Consultancy; Celgene: Consultancy, Research Funding; Amgen: Consultancy, Research Funding; Takeda: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding. Hassoun:Oncopeptides AB: Research Funding.

Abstract: Introduction Newly diagnosed multiple myeloma (NDMM) patients who achieve and maintain minimal residual disease (MRD) negativity demonstrate clinical benefit with prolonged progression-free survival and overall survival. Based on available data showing MRD negativity with standard dose KRD (36 mg/m2) approximating 40% (Korde JamaOnc 2015), we designed a MRD response-adapted treatment study for NDMM, where the number of treatment cycles is determined based on MRD status, instead of the traditional paradigm of fixed number of cycles followed by autologous hematopoietic cell transplantation (AHCT). We integrated a flow-based MRD driven platform in this phase I/II study evaluating higher doses of twice-weekly carfilzomib (Car) (45 and 56 mg/m2) in combination with lenalidomide (Len) and dexamethasone (Dex). Methods Eligible NDMM patients were given escalating doses of Car (45 and 56 mg/m2), Len, and Dex in a single arm, phase I standard 3+3 schema design, based on dose-limiting toxicities (DLTs) occurring in cycle 1. Treatment consisted of 28-day cycles with Car 20/45 mg/m2 or 20/56 mg/m2 - days 1, 2, 8, 9 15 and 16; Len 25 mg - days 1-21; and Dex 40 mg weekly cycles 1-4, 20 mg after cycle 4. AHCT eligible patients underwent stem cell collection after 6 cycles, and then continue with protocol therapy. Patients achieving MRD negative status (serum, urine, and bone marrow with 10-color flow) received 2 additional cycles from the time of conversion and then stop therapy. Patients with less than an MRD negative response after any cycle continued therapy until treatment completion (max 12 cycles), disease progression, or unacceptable toxicity. The primary endpoint of the phase II study was to determine the MRD negative rate at the MTD dose, using a Simon's optimal two-stage design. Herein, we have updated results on phase I and phase II portions of the study with a median follow-up of 20.7 months (1.4-31.1). For available data, we present MFC and NGS MRD platforms. Results Twenty-nine patients have enrolled onto study between October 2016 - June 2018, with 18 in phase 1 and stage I of phase II and 11 in stage II of phase II, thus completing target accrual. There were 16 males, 13 females, median age 61 (43-75) years. Baseline characteristics included 18(62%) ISS-I, 9(31%) ISS-II, and 2(7%) ISS-III, and 7(24%) patients high risk FISH (t(4,14), t(14,16), p53 deletion). There were no DLTs within the first cycle that met protocol criteria (0/3 patients in 20/45 mg/m2 cohort and 0/6 patients in 20/56 mg/m2). The MTD chosen was 20/56 mg/m2, and an additional 20 patients were enrolled. Three patients came off study (56 mg/m2 cohort): one due to MI (during C2); one due to intolerable rash (during C2); and one due to personal preference (during C2). Among all 29 patients, grade 3/4 non-hematologic toxicities included 6(21%) rash, 5(17%) electrolyte disturbances, 4(14%) infections, 3(10%) GI, 2(7%) cardiopulmonary, 2(7%) VTE, 2(7%) mood, 2(7%) cataract, and 1(3%) hyperglycemia, and grade 3/4 hematologic toxicities included 12(41%) lymphopenia, 2(7%) leukopenia, 1(3%) neutropenia, and 1(3%) thrombocytopenia. Ten patients had 13 SAEs. For the 15 patients completing protocol therapy, a median number of 11 (7-12) cycles were delivered, and best responses include 9(60%) sCR/CR MRD neg and 6(40%) obtaining VGPR. Among patients reaching sCR/CR MRD neg status, the median time to reach was 8 (5-9) cycles. Among the eleven patients currently remaining on study, 7 have received at least 1 cycle of therapy (response eligible) and best responses thus far, included 1(14%) sCR/CR MRD pending, 4(57%) VGPR, and 2(29%) PR with a median number of 4 (1-8) cycles delivered. Table comparison of MRD platforms shown in sCR/CR patients. Among patients that remain on study, median 20.7 months, no patients have progressed and all remain alive. One patient that came off study due to personal preference during cycle 2 achieved a PR, and has progressed since. Conclusion In this phase I/II clinical trial assessing higher doses of twice-weekly Car dosing in combination with Len and Dex, we established MTD 56 mg/m2 and demonstrated a MRD platform using multi-parametric flow cytometry can be successfully used to tailor individualized treatment plans. Higher doses of twice weekly Car (45 and 56 mg/m2) in combination with Len and Dex, resulted in rapid and deep responses with approximately 60% MRD negative rate, and a safety profile similar to KRD standard dose (Car 36 mg/m2). Table. Table. Disclosures Korde: Amgen: Research Funding. Mailankody:Janssen: Research Funding; Physician Education Resource: Honoraria; Takeda: Research Funding; Juno: Research Funding. Hassoun:Oncopeptides AB: Research Funding. Lesokhin:Janssen: Research Funding; Squibb: Consultancy, Honoraria; Genentech: Research Funding; Bristol-Myers Squibb: Consultancy, Honoraria, Research Funding; Serametrix, inc.: Patents & Royalties: Royalties; Takeda: Consultancy, Honoraria. Smith:Celgene: Consultancy, Patents & Royalties: CAR T cell therapies for MM, Research Funding. Arcila:Invivoscribe, Inc.: Consultancy, Honoraria. Ho:Invivoscribe, Inc.: Honoraria. Landgren:Janssen: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene: Consultancy, Research Funding; Merck: Membership on an entity's Board of Directors or advisory committees; Takeda: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Amgen: Consultancy, Research Funding; Karyopharm: Consultancy; Pfizer: Consultancy.

Abstract: Background: Multiple myeloma (MM) patients who achieve minimal residual disease (MRD) negative status after upfront treatment have prolonged progression-free and overall survival compared with those who remain MRD(+) (Landgren CO, Devlin SM et al. Bone Marrow Transplant. 2016;51(12):1565-8). Commensal intestinal microbial composition has been associated with treatment outcomes in cancer patients. We sought to evaluate whether the composition of the intestinal microbiota is associated with MRD status in patients with MM. Methods: Stool samples were collected prospectively from 34 patients after completion of upfront therapy for MM at the time of MRD testing. MRD was assessed with next-generation flow cytometry of bone marrow aspirates (sensitivity 10-5). Microbial analysis was performed via sequencing of 16S rRNA V4-V5 regions using the Illumina MiSeq platform and sequence data was analyzed using UPARSE (Edgar RC, Nature Methods 2013;10(10):996-8). The linear discriminant effect size method (LEfSe) (Segata N et al. Genome Biol. 2011;12(6):R60.) was used to compare detected clades among all groups and evaluate for associations with outcomes, using MRD as class and autologous stem cell transplant (ASCT) as subclass. Alpha diversity was calculated by the Inverse Simpson index and differential relative abundance were calculated using the phyloseq package and compared using the Wilcoxon rank sum test on the R statistical computing platform. Results: Among 34 patients evaluable for microbiota composition and MRD status, the median age was 62.5 years and 16 (47.1%) were MRD(-) at time of stool collection. 24 (70.6%) were treated with carfilzomib, lenalidomide, and dexamethasone as induction therapy (MRD(-): 14 (87.5%), MRD(+):10 (55.5%). 4 (28.5%) MRD(-) patients had autologous stem cell transplant(ASCT), compared with 10 (55.5%) who were MRD(+). In the cohort's samples, we observed 19 phyla, 315 genera, 654 species, and 1549 operational taxonomic units (OTUs). There was no significant difference in alpha diversity between MRD(-) (median 12.24, IQR = 8.76-13.98) and MRD(+) patients (median 12.44, IQR = 8.36 -16.23), p=0.6 by Wilcoxon rank sum test. A positive association with MRD negativity was noted with two butyrate-producing organisms, Eubacterium hallii (p=0.001) and Faecalibacterium prausnitzii (p= 0.006). To further evaluate these relationships, we performed a differential abundance analysis of these selected taxa in MRD(+) and MRD(-) patients at the genus and species level. The relative abundance of the genera Eubacterium and Faecalibacterium were higher in fecal samples from MRD(-) patients than MRD(+) patients (Eubacterium MRD(-): median 4.51% (IQR = 2.83 - 7.32%) vs. MRD(+): median 3.07% (IQR = 1.35 - 3.87%), p=0.0326; Faecalibacterium MRD(-): median 1.68% (IQR = 0.69 - 7.48%) vs. MRD(+): median 0.003% (IQR = 0 - 3.19%), p=0.022. The relative abundance of both species of interest were higher in MRD(-) patients than in MRD(+) patients: E. hallii MRD(-): median 2.67% (IQR = 2.11 - 3.98%) vs. MRD(+): median 1.01% (IQR = 0 - 2.16%), p=0.001; F. prausnitzii MRD(-): median 1.43% (IQR = 0.53 - 7.28%) vs. MRD(+): median 0.3%, (IQR = 0 - 2.54%), p=0.022. Other species of Eubacterium and Faecalibacterium were not significantly differentially abundant between the two groups. Conclusions: Intestinal microbiota containing several butyrate-producing anaerobes appear to be associated with MRD-negativity in patients with myeloma, with higher relative abundance of Eubacterium hallii and Faecalibacterium prausnitzii in MRD(-) patients compared with MRD(+) patients. Butyrate and other short-chain fatty acids are biologically active metabolites formed during microbial fermentation of dietary or host-derived carbohydrates, which supply the host with energy and also modulate immunity, including exerting anti-inflammatory functions. Microbes of the genus Eubacterium have been associated with reduced risk of relapse in several hematologic cancers after allogeneic hematopoietic cell transplantation, including MM (Peled JU, Devlin SM et al. J Clin Oncol 2017;35(15):1650-9). This is first study to our knowledge to suggest an association between gut microbiota and MRD status in patients with myeloma and supports further investigation of a potential role for intestinal microbiota in the natural history and treatment of myeloma. Disclosures Peled: Seres Therapeutics: Research Funding. Landgren:Karyopharm: Consultancy; Merck: Membership on an entity's Board of Directors or advisory committees; Pfizer: Consultancy; Janssen: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene: Consultancy, Research Funding; Amgen: Consultancy, Research Funding; Takeda: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding. Lesokhin:Squibb: Consultancy, Honoraria; Genentech: Research Funding; Bristol-Myers Squibb: Consultancy, Honoraria, Research Funding; Serametrix, inc.: Patents & Royalties: Royalties; Takeda: Consultancy, Honoraria; Janssen: Research Funding.

Abstract: Introduction Smoldering multiple myeloma (SMM) is an asymptomatic precursor stage to active multiple myeloma (MM), comprised by a heterogenous group of patients with varying rates of progression. While the overall yearly progression rate is 10% the first 5 years, some patients progress at a considerably higher rate. A study from the Mayo Clinic showed that in a subset of 21 patients defined by ≥60% monoclonal bone marrow plasma cells (BMPC), 95% progressed within 2 years. It was subsequently concluded by the International Myeloma Working Group (IMWG) that patients with biomarkers predictive of a 2-year progression rate at 80%, and a median time to progression at 12 months were at ultra-high risk of progression and should be considered to have MM requiring treatment despite being asymptomatic. In 2014, ultra-high risk biomarkers were incorporated in the definition of MM, including BMPC ≥60%, free light chain (FLC) ratio ≥100 and ≥2 focal lesions on magnetic resonance imaging (MRI). While the updated myeloma definition changed the diagnosis of some patients with ultra-high risk SMM to MM, there remain patients classified as SMM progressing at a very high rate. In the present study, we aimed at further identifying ultra-high risk biomarkers predictive of a high rate of progression to active MM. Methods Patients with SMM presenting to Memorial Sloan Kettering Cancer Center between the years 2000 and 2017 were identified and included in the study. Diagnosis of SMM and progression to MM requiring therapy was defined according to the IMWG criteria at the time of diagnosis. Baseline patient and disease characteristics were collected at date of diagnosis with SMM, including pathology reports, laboratory results and imaging data. Time to progression (TTP) was assessed using the Kaplan-Meier method with log-rank test for comparisons. Optimal cut-off values for continuous variables were assessed with receiver operating characteristics (ROC) curve. Patients who had not progressed by the end of study or were lost to follow up were censored at the date of last visit. Univariate Cox regression was used to estimate risk factors for TTP with hazard ratios (HR) and 95% confidence intervals (CI). Significant univariate risk factors were selected for multivariate Cox regression. Results A total of 444 patients were included in the study. Median follow-up time was 78 months. During the study period, 215 (48%) patients progressed to active MM, with a median TTP of 72 months. Cut-off points for BMPC, M-spike, and FLC ratio were determined with ROC curves to be 20%, 2 g/dL, and 18, respectively, for predicting high risk of progression. The following factors were associated with significantly increased risk of progression to active MM: BMPC 〉 20%, M-spike 〉 2g/dL, FLC ratio 〉 18, immunoparesis with depression of 1 and 2 uninvolved immunoglobulins respectively, elevated lactate dehydrogenase, elevated beta-2-microglobulin, and low albumin (Table 1). In the multivariate model, BMPC 〉 20% (HR 2.5, 95% CI 1.6-3.9), M-spike 〉 2g/dL (HR 3.2, CI 1.9-5.5), FLC ratio 〉 18 (HR 1.8, CI 1.1-3.0), albumin 〈 3.5 g/dL (HR 3.9, CI 1.5-10.0), and immunoparesis with 2 uninvolved immunoglobulins (HR 2.3, CI 1.2-4.3), predicted a decreased TTP (Table 1). A total of 12 patients had 4 or 5 of the risk factors from the multivariate model, 8 of these did not meet the 2014 IMWG criteria for MM. These patients had a significantly shorter TTP than patients with less than 4 risk factors (median TTP 11 vs 74 months, p 〈 0.0001, Figure 1). At 16 months, 82% of these patients had progressed, and within 2 years, 91% of the patients progressed. Only one patient remained progression free after 2 years, progressing at 31 months. Of patients with less than 4 risk factors, 19% progressed within the first 2 years. Conclusion In addition to baseline BMPC 〉 20%, M-spike 〉 2g/dL, FLC-ratio 〉 18, we found that albumin 〈 3.5g/dL and immunoparesis of both uninvolved immunoglobulins at the time of diagnosis with SMM were highly predictive of a decreased TTP to MM requiring therapy. These biomarkers are readily available and routinely assessed in clinic. Patients with 4 or 5 of these risk factors represent a new ultra-high risk group that progress to active disease within 2 years, further expanding on the definition of ultra-high risk SMM. In accordance with the rationale on ultra-high risk biomarkers as criteria established by the IMWG in 2014, such patients should be considered to have MM requiring therapy. Disclosures Korde: Amgen: Research Funding. Mailankody:Janssen: Research Funding; Takeda: Research Funding; Juno: Research Funding; Physician Education Resource: Honoraria. Lesokhin:Squibb: Consultancy, Honoraria; Serametrix, inc.: Patents & Royalties: Royalties; Takeda: Consultancy, Honoraria; Genentech: Research Funding; Bristol-Myers Squibb: Consultancy, Honoraria, Research Funding; Janssen: Research Funding. Hassoun:Oncopeptides AB: Research Funding. Smith:Celgene: Consultancy, Patents & Royalties: CAR T cell therapies for MM, Research Funding. Shah:Amgen: Research Funding; Janssen: Research Funding. Mezzi:Amgen: Employment, Equity Ownership. Khurana:Amgen: Employment, Equity Ownership. Braunlin:Amgen: Employment. Werther:Amgen: Employment, Equity Ownership. Landgren:Takeda: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Janssen: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Karyopharm: Consultancy; Merck: Membership on an entity's Board of Directors or advisory committees; Amgen: Consultancy, Research Funding; Pfizer: Consultancy; Celgene: Consultancy, Research Funding.

Abstract: Background Minimal residual disease (MRD) negativity is a strong predictor for outcome in multiple myeloma. Next generation sequencing (NGS) for immunoglobulin heavy chain and kappa light chain VDJ rearrangements has become increasingly more common for MRD assessment. One of the known challenges with NGS for VDJ rearrangements is the vast diversity of sequences that are present, resulting in a need for a multiplex approach as common primers cannot be used to amplify all rearrangements. Also, somatic hypermutation may affect the annealing of primers and decrease the capture rate. The NGS VDJ assay developed by Adaptive Biotechnologies targets all theoretical combinations of VDJ sequences and has been used in several recent large randomized trials in multiple myeloma. The reported ~80% capture rate of the first version of the Sequenta/Adaptive 1.3 assay limited the ability to track MRD status post therapy. The assay has recently been updated and validated to increase resilience to somatic hypermutation. As there is no published reference data using this assay, we were motivated to assess VDJ capture in the clinical setting. Methods In total, 147 patients with newly diagnosed multiple myeloma (NDMM, n=101) or relapse/refractory multiple myeloma (RRMM, n=46) seen at Memorial Sloan Kettering Cancer Center were identified and included in the study. At bone marrow collection, patient samples were sorted for mononuclear cells and a subset of samples were sorted for CD138+ plasma cells. Stored bone marrow samples from these patients underwent DNA extraction and were sequenced with the Adaptive NGS VDJ assay. The same samples were also sequenced for genomic events using our internal NGS panel myTYPE. myTYPE is a custom capture panel targeting the most frequent multiple myeloma associated-somatic mutations, copy number alterations, and IGH translocations. Logistic regression was used to calculate odds ratios (ORs) with 95% confidence intervals (CIs) of detection success in relation to clinical parameters such as age, gender, percent bone marrow plasma cells, as well as immunoglobulin heavy and light chain types, and myTYPE positivity. Results There overall capture rate for a unique VDJ sequence was 80%, 75% in NDMM samples and 89% in RRMM samples, respectively. The VDJ capture rate in samples that were myTYPE positive, e.g. samples with at least one genomic aberration detected by myTYPE, was 94%. In univariate analysis, the ORs of detecting a clonal VDJ sequence was 1.8 (95% CI 1.3-2.5) and 1.5 (1.2-1.9) for every 10% increase in plasma cells on bone marrow aspirate and biopsy, respectively. For every 1g/dL increase in M-spike, the OR of VDJ capture was 1.6 (1.2-2.2). Samples with at least one genomic aberration detected by myTYPE had a significantly higher detection rate of VDJ sequence, the OR of VDJ capture in myTYPE positive samples was 8.8 (3.2-31.3). Conversely, age, gender, type of immunoglobulin heavy chain (IgG or IgA), or light chain type (kappa or lambda) had no significant effect on the VDJ detection rate (Table). In multivariate analysis, myTYPE positivity was found to be an independent predictor of VDJ capture, with an OR of 4.9 (1.6-18.4, p=0.009) for myTYPE positive samples. The ORs were 1.4 (1.1-2.2, p=0.052) for an increase in 10% plasma cells on bone marrow aspirate and 1.5 (0.97-2.3, p=0.083) every 1g/dL increase in M-spike. Conclusion The VDJ capture rate using the updated Adaptive NGS VDJ assay was 94% in multiple myeloma samples of high quality as indicated by myTYPE positivity. The capture success rate was higher in samples with a greater disease burden. As expected, the assay was less sensitive in samples with insufficient DNA content. Our results are supportive of the use of this NGS VDJ in multiple myeloma, but also illustrate the importance of optimal sample ascertainment and processing. Disclosures Jacob: Adaptive Biotechnologies: Employment, Equity Ownership. Korde:Amgen: Research Funding. Mailankody:Juno: Research Funding; Physician Education Resource: Honoraria; Janssen: Research Funding; Takeda: Research Funding. Lesokhin:Serametrix, inc.: Patents & Royalties: Royalties; Squibb: Consultancy, Honoraria; Bristol-Myers Squibb: Consultancy, Honoraria, Research Funding; Takeda: Consultancy, Honoraria; Janssen: Research Funding; Genentech: Research Funding. Hassoun:Oncopeptides AB: Research Funding. Smith:Celgene: Consultancy, Patents & Royalties: CAR T cell therapies for MM, Research Funding. Landgren:Takeda: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Pfizer: Consultancy; Amgen: Consultancy, Research Funding; Janssen: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Karyopharm: Consultancy; Merck: Membership on an entity's Board of Directors or advisory committees; Celgene: Consultancy, Research Funding.

Abstract: Introduction: BCMA targeted CAR T cell therapy has shown promising results in patients with relapsed/refractory multiple myeloma (MM). Herein, we report on the safety and efficacy of MCARH171, a second generation, human derived BCMA targeted autologous 4-1BB containing CAR T cell therapy, including a truncated epidermal growth factor receptor safety system (Smith EL. Mol Ther 2018). Methods: This is a phase I first in human, dose escalation trial of MCARH171. Patients received conditioning chemotherapy with cyclophosphamide (Cy) 3 gm/m2 as a single dose or fludarabine 30 mg/m2 daily and Cy 300 mg/m2 daily for 3 days followed by MCARH171 infusion in 1-2 divided doses. The trial followed a standard 3+3 design with 4 dose levels where patients received the following mean doses per cohort: (1) 72x106, (2) 137x106, (3) 475x106, (4) 818x106 viable CAR+ T cells. The primary objective was to demonstrate safety, and secondary objectives included efficacy and expansion, and persistence of CAR T cells using PCR from the peripheral blood. The last accrued patient received MCARH171 on Dec 6, 2017 and the data cut-off is July 16, 2018. The study is closed to accrual. Results: 11 patients with relapsed and/or refractory MM were treated. Median number of prior lines of therapy was 6 (range: 4-14), and all patients received prior therapy with a proteasome inhibitor, IMiD, anti-CD38 monoclonal antibody, and high dose melphalan/stem cell transplant. Nine (82%) patients had high-risk cytogenetics and 9 (82%) were refractory to their immediate prior line of treatment. One patient was not evaluable for DLTs given the need for early radiation and steroids for impending spinal cord compression by tumor. There are no DLTs reported. Cytokine release syndrome (CRS) grade 1-2 occurred in 4 patients (40%), grade 3 occurred in 2 (20%), and there was no grade 4-5 CRS. Grade 2 encephalopathy occurred in 1 patient (10%) in the setting of high fevers which resolved in less than 24 hours. There was no grade 3 or higher neurotoxicity observed. Tocilizumab was administered to 3 patients; 2 in cohort 2, and 1 in cohort 3. Laboratory values correlating with CRS reaching grade 3 or requiring Tocilizumab (N=4) compared to those with no or milder CRS (N=6) included peak CRP (mean: 28.5 vs 4.6 mg/dL, p 〈 0.001), IFNg (mean peak fold increase: 271 vs 11-fold, p 〈 0.0001), and peak IL6 before Tocilizumab, as IL6 elevation artificially increases after use (mean: 435 vs 68.7 pg/mL, p 〈 0.005). No significant change was seen in ferritin or fibrinogen compared to baseline. Overall response rate was 64% and the median duration of response was 106 days (range: 17 to 235 days). The peak expansion and persistence of MCARH171 as well as durable clinical responses were dose dependent. Patients who were treated on the first two dose cohorts (≤150 X106 CAR T cells) had a lower peak expansion in the peripheral blood (mean 14,098 copies/µL; N=6), compared to patients who were treated on the third or fourth dose cohort 3-4 (≥450 X106 CAR T cells; N=5), where the mean peak expansion was 90,208 copies/µL (p 〈 0.05). Among the 5 patients who received higher doses (450 X106), 5/5(100%) patients responded. The duration of responses was also related to the cell dose, with 3 of 5 patients (60%) treated in the cohorts receiving ≥450 X106 had clinical responses lasting 〉 6 months compared to only 1 of 6 (16.7%) patients who received lower doses. Two patien have ongoing responses (VGPR) at 7.5+ and 10+ months of follow up. To normalize for dose administered we compared the pharmacokinetics of only patients treated at dose levels 3-4 ( ≥450 X106 CAR T cells). Here, we demonstrate that peak expansion correlated to clinical efficacy, with the 3 durable responders all having peak expansion 〉 85,000 copies/µL (mean: 131,732 copies/µL); compared to transient responders, where the maximum peak expansion was 33,213 copies/µL (mean: 27,922; Figure 1). Conclusions: MCARH171 has an acceptable safety profile with no DLTs reported. A dose-response relationship with toxicity was not clearly observed, as noted by distribution of tocilizumab use across dose cohorts. However, a dose-response relationship was observed with promising clinical efficacy at dose levels of ≥450 X106 CAR T cells. Controlling for dose level, peak expansion correlated with durability of response. These results further support the development of CAR T cells for heavily pre-treated patients with relapsed and refractory MM. Disclosures Mailankody: Janssen: Research Funding; Takeda: Research Funding; Juno: Research Funding; Physician Education Resource: Honoraria. Korde:Amgen: Research Funding. Lesokhin:Takeda: Consultancy, Honoraria; Squibb: Consultancy, Honoraria; Janssen: Research Funding; Genentech: Research Funding; Serametrix, inc.: Patents & Royalties: Royalties; Bristol-Myers Squibb: Consultancy, Honoraria, Research Funding. Hassoun:Oncopeptides AB: Research Funding. Park:Juno Therapeutics: Consultancy, Research Funding; Amgen: Consultancy, Membership on an entity's Board of Directors or advisory committees; Pfizer: Consultancy; AstraZeneca: Consultancy; Adaptive Biotechnologies: Consultancy; Kite Pharma: Consultancy; Novartis: Consultancy; Shire: Consultancy. Sauter:Juno Therapeutics: Consultancy, Research Funding; Sanofi-Genzyme: Consultancy, Research Funding; Spectrum Pharmaceuticals: Consultancy; Novartis: Consultancy; Precision Biosciences: Consultancy; Kite: Consultancy. Palomba:Pharmacyclics: Consultancy; Celgene: Consultancy. Riviere:Fate Therapeutics Inc.: Research Funding; Juno Therapeutics, a Celgene Company: Membership on an entity's Board of Directors or advisory committees, Research Funding. Landgren:Takeda: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Amgen: Consultancy, Research Funding; Pfizer: Consultancy; Janssen: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Karyopharm: Consultancy; Merck: Membership on an entity's Board of Directors or advisory committees; Celgene: Consultancy, Research Funding. Brentjens:Juno Therapeutics, a Celgene Company: Consultancy, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties, Research Funding. Smith:Celgene: Consultancy, Patents & Royalties: CAR T cell therapies for MM, Research Funding.