Abstract: Background and Scientific Rationale Lenalidomide maintenance after autologous stem cell transplantation (ASCT) in newly diagnosed multiple myeloma (MM) patients has demonstrated an improved progression free survival (PFS) and overall survival (OS) when compared to placebo or observation in a meta-analysis (McCarthy et al. JCO 2017). Despite these improvements, patients on maintenance had higher rates of second primary malignancy and discontinuation due to treatment-emergent adverse events which may lead to decreased quality of life (QoL). Most MM patients are treated with lenalidomide maintenance in the absence of great alternatives. Thus, there is an unmet clinical need to develop alternative maintenance strategies. Daratumumab is well tolerated and effective in MM, with many studies continuing daratumumab as maintenance until disease progression. The proposed study seeks to further investigate and directly compare patient reported QoL between maintenance lenalidomide and daratumumab. Study Design and Methods This is an open-label single-center randomized pilot study of daratumumab versus lenalidomide maintenance in 100 newly diagnosed MM patients (Figure). Clinical trial registry number : NCT04497961, actively recruiting. Study population A total of 100 patients will be enrolled, randomized 1:1 to each arm (50 patients per arm). Randomization for enrollment will be stratified by patient age ( & lt;65 years and ≥65 years) and prior ASCT status (yes or no). Inclusion criteria Newly diagnosed MM treated with combination therapy with or without ASCT Documentation of a very good partial response or better.Enrollment within 6 months of completing initial combination therapy.Enrollment following minimum 100-day washout per standard guidelines in ASCT recipients.ECOG performance status ≤ 2. Exclusion criteria  Progressive or refractory MM.History of disease refractory to lenalidomide or daratumumab.History of prior anti-myeloma therapy for smoldering MM.Currently receiving other investigational agents to treat MM. Study treatment The length of therapy on both arms is 36 cycles of 28 days (~3 years), or until disease progression or unacceptable toxicity. Subjects under the lenalidomide arm will be treated with a maintenance dose of lenalidomide 10mg per day on days 1 to 21 of each cycle. Subjects under the daratumumab arm will be treated with a standard subcutaneous dose of 1800mg weekly in cycles 1 & 2, followed by every 2 weeks in cycles 3-6 and every 4 weeks cycles 7-36. Study assessments Subjects will complete three validated questionnaires - EORTC QLQ-C30 (general QOL in cancer patients), EORTC QLQ-MY20 (QOL in MM patients) and PRO-CTCAE (adverse events). These will be collected at baseline, day 1 of cycle 2, every cycle day 1 thereafter, at study/therapy discontinuation, and at 1-month post therapy follow-up. The GHS score will be calculated based on questions from the EORTC QLQ-C30. Endpoints Primary To compare differences in GHS scores between patients receiving lenalidomide versus daratumumab maintenance Secondary To explore differences in EORTC QLQ-C30, EORTC QLQ-MY20 and PRO-CTCAE scoresTo compare CTCAE adverse eventsTo evaluate differences in PFS and OSTo estimate differences in minimal residual disease statusTo explore the association between minimal residual disease status and clinical outcomes Exploratory To compare minimal residual disease techniques of multi-parametric flow with next-generation sequencing and mass spectrometryTo assess differences in T cell, NKT, NK cell subtypesTo explore associations between disease biology and clinical outcomes using genomic sequencing.To assess changes in the stool microbiome Statistical methods This protocol is a randomized pilot study to estimate the difference in the global health status for patients receiving lenalidomide maintenance to patients receiving daratumumab maintenance. The primary endpoint is the GHS from EORTC QLQ-C30. The primary analysis will be performed using a linear mixed effects model. The randomization stratification factors will be included as covariates in the regression model. The primary endpoint evaluation will use all GHS available up until the final evaluation at 36 cycles. Figure 1 Figure 1. Disclosures Shah: Celgene/BMS: Research Funding; Janssen: Research Funding. Mailankody: Bristol Myers Squibb/Juno: Research Funding; Fate Therapeutics: Research Funding; Physician Education Resource: Honoraria; Evicore: Consultancy; Legend Biotech: Consultancy; Plexus Communications: Honoraria; Jansen Oncology: Research Funding; Allogene Therapeutics: Research Funding; Takeda Oncology: Research Funding. Korde: Medimmune: Membership on an entity's Board of Directors or advisory committees; Amgen: Research Funding. Hultcrantz: Intellisphere LLC: Consultancy; Daiichi Sankyo: Research Funding; Amgen: Research Funding; GlaxoSmithKline: Membership on an entity's Board of Directors or advisory committees, Research Funding; Curio Science LLC: Consultancy. Hassoun: Celgene, Takeda, Janssen: Research Funding. Scordo: Angiocrine Bioscience: Consultancy, Research Funding; Omeros Corporation: Consultancy; Kite - A Gilead Company: Membership on an entity's Board of Directors or advisory committees; i3 Health: Other: Speaker; McKinsey & Company: Consultancy. Dahi: Kite / Gilead: Membership on an entity's Board of Directors or advisory committees. Lahoud: MorphoSys: Membership on an entity's Board of Directors or advisory committees. Landau: Takeda, Janssen, Caelum Biosciences, Celgene, Pfizer, Genzyme: Membership on an entity's Board of Directors or advisory committees; Takeda: Research Funding; Genzyme: Honoraria. Shah: Janssen: Research Funding; Amgen: Research Funding. Giralt: Actinnum: Membership on an entity's Board of Directors or advisory committees; SANOFI: Membership on an entity's Board of Directors or advisory committees; AMGEN: Membership on an entity's Board of Directors or advisory committees; CELGENE: Membership on an entity's Board of Directors or advisory committees; PFIZER: Membership on an entity's Board of Directors or advisory committees; BMS: Membership on an entity's Board of Directors or advisory committees; GSK: Membership on an entity's Board of Directors or advisory committees; JENSENN: Membership on an entity's Board of Directors or advisory committees; JAZZ: Membership on an entity's Board of Directors or advisory committees. Lesokhin: Behringer Ingelheim: Honoraria; bristol myers squibb: Research Funding; pfizer: Consultancy, Research Funding; Serametrix, Inc: Patents & Royalties; Trillium Therapeutics: Consultancy; Genetech: Research Funding; Iteos: Consultancy; Janssen: Honoraria, Research Funding. Landgren: Amgen: Honoraria; Janssen: Other: IDMC; Amgen: Research Funding; Janssen: Research Funding; Janssen: Honoraria; Celgene: Research Funding; Takeda: Other: IDMC; GSK: Honoraria.

Abstract: Background and Scientific Rationale Solitary plasmacytoma of the bone (SPB) is a rare entity representing 5% of all plasma cell dyscrasias. SPB treated with radiation therapy (RT) has a 10% risk of progression to multiple myeloma (MM) over 3 years if there is no marrow involvement, whereas there is a 60% chance of progression over 3 years in patients with minimal marrow involvement. Median time to progression in the latter group is 26 months. Presently, despite mounting evidence of a significant risk of progression to MM, there is no FDA-approved therapy and patients are usually treated with localized RT. This is an area of unmet need. A similar opportunity exists in the setting of MM patients relapsing with localized disease amenable to RT. This group of patients may not immediately require long-term systemic therapy especially if RT combined with epigenetic modulation and lenalidomide results in therapeutically relevant immune responses. A few studies combining lenalidomide and azacitidine have shown responses even in a lenalidomide refractory population with upregulation of cancer testis antigen (CTA) as well as CTA specific T cell responses (Table 1). These synergistic mechanisms focus on: 1) manipulating antigen expression and enhancing antigen presentation (both neoantigens and cancer testis antigens) with oral azacitidine (CC-486), and 2) augmentation of antigen specific immune responses via increased IL2 production leading to an increase in the proliferation of T cells with lenalidomide. This combination with RT would serve to inflame the tumor microenvironment and potentially lead to therapeutically active systemic immune responses via an abscopal effect. Study Design and Methods This is an open-label, single center, single-arm study of CC-486, lenalidomide plus RT, which will enroll a total of 20 patients in two cohorts. Clinical trial registry number NCT04174196, actively recruiting. Study population and inclusion criteria Each cohort will enroll ten patients - Cohort 1: i) Histologically confirmed newly diagnosed solitary plasmacytoma of the bone or lytic bone lesion ii) Minimal marrow involvement (Detectable clonal bone marrow (BM) plasma cells by multicolor flow cytometry and ≤ 10% clonal plasma cells in a BM biopsy by immunohistochemistry, morphology, or flow cytometry) iii) Secretory M protein & lt; 3 g/dL Cohort 2: i) Relapsed multiple myeloma with plasmacytomas appropriate for RT on imaging ii) Relapsed (reappearance of M-spike/serum FLC) or progressive myeloma defined by a 25% increase from nadir in M-spike or involved serum FLC on 2 separate measurements; or with BM involvement by clonal plasma cells detectable by IHC iii) Any prior number of therapies is permitted, including prior RT iv) Allogeneic transplant patients are permitted Statistical methods We estimate the historical rate of stringent complete response (sCR) is approximately 5% (based on the rate for newly diagnosed myeloma with lenalidomide and dexamethasone on the MAIA study of 7.3% and for relapsed myeloma with Rd based on the POLLUX study of 4.6%). The primary endpoint of the study will be reported separately for the two cohorts. With 10 patients in each cohort, the maximum half-width of the exact 95% confidence interval for the response rate is +/- 0.31. A sCR rate of ≥20% would be considered promising for either cohort. Study treatment In the study, patients will be treated with CC-486 100 mg on day 1-21 and lenalidomide 25 mg on day 1-21 for 6 cycles. RT to the plasmacytoma will be initiated after cycle 2. Total dose may vary between 30-50 Gy (45-50 Gy for cohort 1) based on clinical judgement. (Figure 1) Endpoints Primary To provide preliminary efficacy data based on the rate of sCR by 2016 IMWG Criteria on post-treatment BM biopsy and aspirate specimens with no new lesions by PET. Secondary - To assess the safety of this combination. - To estimate the progression free survival and overall survival Exploratory - To evaluate antigen expression at the tumor site pre and post RT - To further characterize the antigen specific T cell response pre and post RT at the tumor site - To assess changes in epigenetic marks - To assess changes in the tumor microenvironment Disclosures Shah: Physicians Education Resource: Honoraria; Celgene/BMS: Research Funding. Mailankody:Juno Therapeutics, a Bristol-Myers Squibb Company: Research Funding; Allogene Therapeutics: Research Funding; Janssen Oncology: Research Funding; Takeda Oncology: Research Funding; PleXus Communications: Honoraria; Physician Education Resource: Honoraria. Korde:Astra Zeneca: Other: Advisory Board; Amgen: Research Funding. Hultcrantz:GSK: Research Funding; Daiichi Sankyo: Research Funding; Amgen: Research Funding; Intellisphere LLC: Consultancy. Smith:Precision Biosciences: Consultancy; Fate Therapeutics: Consultancy; Bristol Myers Squibb: Consultancy, Patents & Royalties, Research Funding. Shah:Janssen Pharmaceutica: Research Funding; Amgen: Research Funding. Lahoud:MorphoSys: Other: Advisory Board. Scordo:McKinsey & Company: Consultancy; Angiocrine Bioscience, Inc.: Consultancy, Research Funding; Omeros Corporation: Consultancy; Kite - A Gilead Company: Other: Ad-hoc advisory board. Dahi:Kite: Consultancy. Chung:Genentech: Research Funding. Hassoun:Novartis: Consultancy; Celgene: Research Funding; Takeda: Research Funding. Barker:Elekta: Research Funding; Amgen: Research Funding; Alpha Tau Medical: Other: Travel expenses, Research Funding; Merck: Research Funding. Giralt:KITE: Consultancy; MILTENYI: Consultancy, Research Funding; OMEROS: Consultancy, Honoraria; CELGENE: Consultancy, Honoraria, Research Funding; AMGEN: Consultancy, Research Funding; NOVARTIS: Consultancy, Honoraria, Research Funding; JAZZ: Consultancy, Honoraria; ACTINUUM: Consultancy, Research Funding; TAKEDA: Research Funding. Landgren:Adaptive: Consultancy, Honoraria; Takeda: Other: Independent Data Monitoring Committees for clinical trials, Research Funding; BMS: Consultancy, Honoraria; Cellectis: Consultancy, Honoraria; Glenmark: Consultancy, Honoraria, Research Funding; Juno: Consultancy, Honoraria; Seattle Genetics: Research Funding; Pfizer: Consultancy, Honoraria; Merck: Other; Karyopharma: Research Funding; Binding Site: Consultancy, Honoraria; BMS: Consultancy, Honoraria; Cellectis: Consultancy, Honoraria; Juno: Consultancy, Honoraria; Pfizer: Consultancy, Honoraria; Merck: Other; Glenmark: Consultancy, Honoraria, Research Funding; Amgen: Consultancy, Honoraria, Research Funding; Celgene: Consultancy, Honoraria, Research Funding; Janssen: Consultancy, Honoraria, Other: Independent Data Monitoring Committees for clinical trials, Research Funding; Takeda: Other: Independent Data Monitoring Committees for clinical trials, Research Funding; Karyopharma: Research Funding; Binding Site: Consultancy, Honoraria; Janssen: Consultancy, Honoraria, Other: Independent Data Monitoring Committees for clinical trials, Research Funding; Seattle Genetics: Research Funding; Celgene: Consultancy, Honoraria, Research Funding. Lesokhin:Janssen: Research Funding; GenMab: Consultancy, Honoraria; BMS: Consultancy, Honoraria, Research Funding; Juno: Consultancy, Honoraria; Takeda: Consultancy, Honoraria; Genentech: Research Funding; Serametrix Inc.: Patents & Royalties. OffLabel Disclosure: CC-486 is an is an oral hypomethylating agent that has been studied in acute myeloid leukemia. This study combines CC-486 with lenalidomide and radiation therapy in plasma cell disorders.

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. Bortezomib, lenalidomide and dexamethasone (VRd) is considered a standard of care combination therapy for newly diagnosed multiple myeloma patients. Prior studies show that ~25% of patients treated with 8 cycles of VRd achieve minimal residual disease (MRD) negativity. Recently, 42% stringent complete response (sCR) rates were reported with the use of VRd combined with the CD38-targeted monoclonal antibody daratumumab (VRd-D). Prior studies using 8 cycles of bi-weekly carfilzomib 36 mg/m2 with lenalidomide and dexamethasone (bKRd) combination therapy in newly diagnosed multiple myeloma show ~40% MRD negativity rates. We were motivated to develop a phase 2 study (total N=82) using weekly dosing of carfilzomib 56 mg/m2 with lenalidomide and dexamethasone (wKRd) in combination with daratumumab (wKRd-D). Our study also included a parallel cohort of bi-weekly dosing of carfilzomib 36 mg/m2 with lenalidomide and dexamethasone (bKRd) in combination with daratumumab (bKRd-D). Primary end-point of our study was to rule out 60% and to target up to 80% MRD negativity rate. METHODS. This is a two-arm, Phase II clinical trial based on Simon's optimal two-stage design. The once-a-week carfilzomib (wKRd) (N=41) has the following treatment schedule: 8 cycles of treatment; 28-day cycles with carfilzomib 20/56 mg/m2 days 1, 8, and 15; lenalidomide 25 mg days 1-21; dexamethasone 40 mg weekly cycles 1-4, 20 mg after cycle 4; and daratumumab 16 mg/kg days 1, 8, 15, and 22 cycles 1-2, days 1 and 15 cycles 3-6, and day 1 cycles 7-8. The bi-weekly carfilzomib (bKRd) (N=41): 8 cycles of treatment; 28-day cycles with carfilzomib 20/36 mg/m2 days 1, 2, 8, 9, 15 and 16; lenalidomide, dexamethasone, and daratumumab are given at the same doses/schedules as the weekly cohort. For fit patients, stem cell collection is recommended after 4 to 6 cycles of therapy; DKRd therapy is resumed after collection to a total of 8 cycles DKRd. Treatment response is being assessed with parallel bone marrow-based MRD assays (10-color single tube flowcytometry and invivoscribe IGHV sequencing); per IMWG guidelines both MRD assays allow detection of 1 myeloma cell in 100,000 bone marrow cells (10^-5). Baseline bone marrow samples are evaluated with targeted DNA sequencing for FISH-Seq and somatic mutational characteristics (myTYPE). RESULTS. The first stage of the weekly cohort (wKRd-D) is fully enrolled (N=28) and the second stage of the cohort (N=13) is anticipated to complete enrollment shortly (total N=41). Currently, 29 patients meeting eligibility criteria were enrolled (14 males, 15 females) between October 2018 and August 2019. Baseline characteristics include; median age 59 years (range 36-70 years); 12 (41%) patients had high-risk FISH/SNP signature defined as one or more of the following: 1q+, t(4;14), t(14;16), t(14;20), and 17p-. At the submission of this abstract, 28 patients have completed one or more cycles wKRd-D; among these, 10 patients have completed therapy. The median number of cycles delivered is currently 6 (range 1-8). Seven of the 10 patients who have completed study treatment are MRD negative. So far, additional 8 patients have become MRD negative while on therapy. Thus, among patients treated on the weekly cohort (wKRd-D) and who were evaluable for the MRD primary end-point at this analysis, we found 15/18 (83%) to be MRD negative. We further show no added major clinical toxicities with wKRd-D compared to our institution standard of care bKRd. The bi-weekly carfilzomib cohort (bKRd-D) shows similar results to the weekly cohort (wKRd-D). With a comparable efficacy and safety profile coupled with a substantial reduction of the number of infusions (total of 51 vs 27 infusions with bKRd-D vs wKRd-D, respectively), we conclude that the weekly dosing (wKRd-D) may offer an attractive treatment modality for newly diagnosed multiple myeloma patients. CONCLUSIONS. Among patients evaluable for the MRD primary end-point, in the absence of an autologous bone marrow transplant, we show an unprecedented 15/18 (83%) MRD negativity rate among newly diagnosed multiple myeloma patients treated on the weekly cohort (wKRd-D) using carfilzomib 56 mg/m2 dosing. Our promising results have prompted the development of a large randomized multi-center study ("ADVANCE") evaluating wKRd-D in relation to established standard of care, which is anticipated to start enrollment in Q3/Q4 of 2019. Disclosures Landgren: Amgen: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Adaptive: 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, Research Funding; Merck: Other: IDMC; Theradex: Other: IDMC; Abbvie: Membership on an entity's Board of Directors or advisory committees; Sanofi: Membership on an entity's Board of Directors or advisory committees; Karyopharm: Membership on an entity's Board of Directors or advisory committees. Lesokhin:GenMab: Consultancy, Honoraria; BMS: Consultancy, Honoraria, Research Funding; Juno: Consultancy, Honoraria; Janssen: Research Funding; Genentech: Research Funding; Takeda: Consultancy, Honoraria; Serametrix Inc.: Patents & Royalties. Mailankody:Juno: Research Funding; Celgene: Research Funding; Janssen: Research Funding; Takeda Oncology: Research Funding; CME activity by Physician Education Resource: Honoraria. Hassoun:Novartis: Consultancy; Celgene: Research Funding; Janssen: Research Funding. Smith:Fate Therapeutics and Precision Biosciences: Consultancy; Celgene: Consultancy, Patents & Royalties, Research Funding. Shah:Physicians' Education Resource: Honoraria. Landau:Caelum: 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; Takeda: Membership on an entity's Board of Directors or advisory committees, Research Funding; Amgen: Research Funding; Karyopharm: Consultancy, Honoraria; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees; Pfizer: Membership on an entity's Board of Directors or advisory committees; Prothena: Membership on an entity's Board of Directors or advisory committees. Scordo:Angiocrine Bioscience, Inc.: Consultancy; McKinsey & Company: Consultancy. Arcila:Invivoscribe, Inc.: Consultancy, Honoraria. Ho:Invivoscribe, Inc.: Honoraria. Roshal:Auron Therapeutics: Equity Ownership, Other: Provision of services; Physicians' Education Resource: Other: Provision of services; Celgene: Other: Provision of Services. Dogan:Corvus Pharmaceuticals: Consultancy; Seattle Genetics: Consultancy; Celgene: Consultancy; Takeda: Consultancy; Novartis: Consultancy; Roche: Consultancy, Research Funding. OffLabel Disclosure: Dara-KRd is not an FDA approved combination therapy for newly diagnosed multiple myeloma.

Abstract: Background: Patients treated with cytotoxic chemotherapies and/or autologous stem-cell transplantation (ASCT) are at risk for therapy-related myeloid neoplasms (tMN). As these agents yield increased mutation burden in relapsed malignancies and leave evidence of exposure via mutational signatures, we studied the genomic and temporal relationship between chemo exposure and progression of clonal hematopoiesis (CH) to tMN. Methods: We analyzed 32 tMN whole genomes (WG) from 31 patients [27 acute myeloid leukemias (AML), 4 myelodysplastic syndromes]. For 7 patients with tMN post-high-dose melphalan/ASCT, we investigated the presence of antecedent CH using targeted sequencing (MSK-IMPACT; Bolton et al. Nat Gen 2020) on pre-melphalan blood mononuclear cells, granulocytes, or CD34+ apheresis samples. Results: TMN was diagnosed a median of 4.2 years (IQR, 2.6-6.6) following primary treatment. When compared to data from 200 de novo AML from TCGA (NEJM, 2013), tMNs had fewer mutations in FLT3 (9.7% v 28.0%; p = 0.028) and NPM1 (3.2% v 27.0%; p = 0.003). TP53 loss was enriched in tMNs (25.8% v 10.5%; p = 0.035 ). Mutational signature analysis revealed 5 known single base substitution (SBS) signatures in tMN: the hematopoietic stem-cell (SBS-HSC), aging (SBS1), melphalan (SBS-MM1), and platinum signatures (E-SBS1, E-SBS20) (Rustad et al. Nat Comm 2020, Pich et al. Nat Gen 2019). Complex structural variants (SV), defined as ≥3 breakpoint pairs involved in simultaneous copy number changes (Rustad et al. Blood Can Disc 2020), were observed in 7 tMNs; including chromothripsis in 6 tumors (19.4%), chromoplexy in 2 (6.5%), templated insertion in 1 (3.2%), and unspecified complex SV in 2 (6.5%). Chromothripsis has not been previously reported in de novo AML and, in 4 cases, involved chromosome 19 with hyper-amplification of the SMARCA4 locus (≥5 copies). CH variants that became clonal in tumor were seen in 5/7 pre-melphalan/ASCT samples and included mutations in TP53, RUNX1, NCOR1, NF1, CREBBP, DNMT3A, and PPM1D. Chemotherapy introduces hundreds of mutations, leaving each exposed cell with a unique catalogue (i.e., barcode). In fact, TMNs with evidence of chemo signatures had a higher mutation burden (median 1574 single nucleotide variants) than those without (median 938; p = 0.004). Detection of chemo signatures in bulk genome sequencing relies on one cell, with its catalogue of mutations, to expand to clonal dominance (Fig 1a, Landau et al. Nat Comm 2020). Given the long latency between exposure and tMN diagnosis, this single-cell expansion model was expected for all samples exposed to melphalan or platinum-based regimens (i.e., agents with a measurable signature). Strikingly, all patients with pre-tMN platinum exposure (n=7) had evidence of platinum SBS signatures whereas only 2 of 7 patients with prior melphalan/ASCT had a melphalan signature (SBS-MM1). As all platinum-exposed tMN had mutational evidence of exposure, a CH clone must have existed prior to exposure, supporting a single-cell expansion model. Absence of a chemo signature for 5/7 post-melphalan/ASCT tumors despite exposure implies tumor progression driven either by multiple clones in parallel (Fig 1b) or by an unexposed clone. As latency largely excludes the former, this suggests pre-tMN CH clones were re-infused during SCT, thus avoiding chemo exposure (Fig 1c). This is supported by two lines of evidence: 1) tMNs from 2 patients exposed to sequential platinum and melphalan/ASCT had platinum but not melphalan signatures confirming single-cell expansion of the pre-tMN CH clone post-platinum but with escape from exposure to melphalan in the ASCT (Fig 1d); 2) targeted sequencing of pre-tMN samples from melphalan/ASCT patients identified tMN genomic mutations at the CH level in 5/7 cases, including in all 3 tested apheresis samples - one of which (TP53) expanded to dominance without a melphalan signature. Conclusion: WG sequencing identified novel features of tMN revealing the key driver role of complex SV. Mutational signature analyses and targeted sequencing of pre-tMN samples can increase our understanding of tMN pathogenesis and demonstrate that tMNs arising post-ASCT are often driven by CH clones that re-engraft after escaping melphalan exposure. This mode of expansion suggests that a permissive, immunosuppressed, post-transplant environment might play a more important role than chemotherapy-induced mutagenesis in tMN pathogenesis. Figure 1 Figure 1. Disclosures Diamond: Sanofi: Honoraria; Medscape: Honoraria. Watts: Rafael Pharmaceuticals: Consultancy; Genentech: Consultancy; Bristol Myers Squibb: Consultancy; Takeda: Consultancy, Research Funding; Jazz Pharmaceuticals: Consultancy; Aptevo Therapeutices: Research Funding. Kazandjian: Arcellx: Honoraria, Membership on an entity's Board of Directors or advisory committees; BMS: Honoraria, Membership on an entity's Board of Directors or advisory committees. Bradley: AbbVie: Consultancy, Speakers Bureau; Novartis: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Bolli: Amgen: Honoraria; Takeda: Honoraria; Janssen: Consultancy, Honoraria; Celgene/BMS: Consultancy, Honoraria. Papaemmanuil: Isabl Technologies: Divested equity in a private or publicly-traded company in the past 24 months; Kyowa Hakko Kirin Pharma: Consultancy. Scordo: Kite - A Gilead Company: Membership on an entity's Board of Directors or advisory committees; i3 Health: Other: Speaker; Omeros Corporation: Consultancy; Angiocrine Bioscience: Consultancy, Research Funding; McKinsey & Company: Consultancy. Lahoud: MorphoSys: Membership on an entity's Board of Directors or advisory committees. Stein: Jazz Pharmaceuticals: Consultancy; Foghorn Therapeutics: Consultancy; Blueprint Medicines: Consultancy; Gilead Sciences, Inc.: Consultancy; Abbvie: Consultancy; Janssen Pharmaceuticals: Consultancy; Genentech: Consultancy; Celgene: Consultancy; Bristol Myers Squibb: Consultancy; Agios Pharmaceuticals, Inc: Consultancy; Novartis: Consultancy; Astellas: Consultancy; Syndax Pharmaceuticals: Consultancy; PinotBio: Consultancy; Daiichi Sankyo: Consultancy; Syros Pharmaceuticals, Inc.: Consultancy. Sauter: Precision Biosciences: Consultancy; Kite/Gilead: Consultancy; Bristol-Myers Squibb: Research Funding; GSK: Consultancy; Gamida Cell: Consultancy; Celgene: Consultancy, Research Funding; Genmab: Consultancy; Novartis: Consultancy; Spectrum Pharmaceuticals: Consultancy; Juno Therapeutics: Consultancy, Research Funding; Sanofi-Genzyme: Consultancy, Research Funding. Hassoun: Celgene, Takeda, Janssen: Research Funding. Mailankody: Bristol Myers Squibb/Juno: Research Funding; Physician Education Resource: Honoraria; Plexus Communications: Honoraria; Takeda Oncology: Research Funding; Jansen Oncology: Research Funding; Fate Therapeutics: Research Funding; Allogene Therapeutics: Research Funding; Legend Biotech: Consultancy; Evicore: Consultancy. Korde: Medimmune: Membership on an entity's Board of Directors or advisory committees; Amgen: Research Funding. Hultcrantz: Daiichi Sankyo: Research Funding; Intellisphere LLC: Consultancy; Curio Science LLC: Consultancy; GlaxoSmithKline: Membership on an entity's Board of Directors or advisory committees, Research Funding; Amgen: Research Funding. Shah: Bristol Myers Squibb: Research Funding; Janssen: Research Funding. Shah: Janssen Pharmaceutica: Research Funding; Amgen: Research Funding. Park: Servier: Consultancy; Affyimmune: Consultancy; Autolus: Consultancy; Minerva: Consultancy; PrecisionBio: Consultancy; BMS: Consultancy; Novartis: Consultancy; Kura Oncology: Consultancy; Curocel: Consultancy; Artiva: Consultancy; Innate Pharma: Consultancy; Intellia: Consultancy; Amgen: Consultancy; Kite Pharma: Consultancy. Landau: Genzyme: Honoraria; Takeda, Janssen, Caelum Biosciences, Celgene, Pfizer, Genzyme: Membership on an entity's Board of Directors or advisory committees; Takeda: Research Funding. Sekeres: BMS: Membership on an entity's Board of Directors or advisory committees; Takeda/Millenium: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees. Ho: Blueprint Medicine: Membership on an entity's Board of Directors or advisory committees. Roshal: Celgene: Other: Provision of services; Auron Therapeutics: Other: Ownership / Equity interests; Provision of services; Physicians' Education Resource: Other: Provision of services. Lesokhin: pfizer: Consultancy, Research Funding; Janssen: Honoraria, Research Funding; Iteos: Consultancy; Serametrix, Inc: Patents & Royalties; Genetech: Research Funding; Trillium Therapeutics: Consultancy; bristol myers squibb: Research Funding; Behringer Ingelheim: Honoraria. Morgan: BMS: Membership on an entity's Board of Directors or advisory committees; Jansen: Membership on an entity's Board of Directors or advisory committees; Karyopharm: Membership on an entity's Board of Directors or advisory committees; Oncopeptides: Membership on an entity's Board of Directors or advisory committees; GSK: Membership on an entity's Board of Directors or advisory committees. Landgren: Janssen: Other: IDMC; Janssen: Research Funding; Amgen: Honoraria; Celgene: Research Funding; Janssen: Honoraria; Amgen: Research Funding; Takeda: Other: IDMC; GSK: Honoraria. Maura: OncLive: Honoraria; Medscape: Consultancy, Honoraria.

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.

Abstract: There are no standard treatments to prevent or hasten the recovery from severe conditioning-regimen–induced thrombocytopenia occurring after autologous hematopoietic cell transplantation (auto-HCT). We conducted an open-label, single-arm pilot study of romiplostim, a thrombopoietin receptor agonist, to enhance platelet recovery in patients with multiple myeloma or lymphoma undergoing auto-HCT. All patients were treated weekly with romiplostim starting day +1 after auto-HCT until the platelet count was & gt;50 × 109/L without transfusion. Compared with contemporary retrospective data from romiplostim-naïve patients (N = 853), romiplostim-treated patients (N = 59) had a similar median number of days of grade 4 thrombocytopenia or days requiring transfusions, time to platelet engraftment, and number of platelets transfusions during the auto-HCT. However, romiplostim-treated patients had enhanced platelet recovery to normal values beginning at approximately day +15. In matched cohort multivariable analyses, romiplostim treatment was associated with higher platelet counts by an average of 40 × 109/L (95% confidence interval (CI) (14, 67), P = .003) and 118 × 109/L (95% CI [84, 152], P & lt;.001) at days +21 and +30, respectively, compared with those of no romiplostim. Only 1 adverse event was deemed possibly attributable to romiplostim: a low-risk pulmonary embolism in a patient with multiple myeloma. In conclusion, romiplostim showed promising activity and safety after auto-HCT, but the improvement in platelet counts occurred later than the goal of shortening the duration and depth of the platelet nadir. This trial was registered at www.clinicaltrials.gov (#NCT04478123).