Serum M-protein Research Articles

P879: EXENT AND FLC MASS SPECTROMETRY FOR SEROLOGICAL IDENTIFICATION AND QUANTIFICATION OF MONOCLONAL IMMUNOGLOBULINS IN MULTIPLE MYELOMA

Background: Mass spectrometry has broad potential for screening and monitoring monoclonal gammopathies. The technology overcomes some of the limitations inherent to standard electrophoretic methods for identifying monoclonal immunoglobulins and is amenable to automation. Aims: Here we assess the performance of the EXENT assays for the quantification of M-proteins and whether free light chain evaluation by mass spectrometry (FLC-MS) offers added sensitivity during multiple myeloma monitoring. Methods: The MM5 trial compared two regimens of bortezomib-based induction therapy and of lenalidomide consolidation followed by lenalidomide maintenance in newly diagnosed multiple myeloma patients. We used mass spectrometry for identifying serum M-proteins in samples at baseline (n=434), post-induction (n=340), and post-consolidation (n=294). Briefly, polyclonal antibodies (anti-IgG,-IgA,-IgM,-total κ and -total λ [EXENT, The Binding Site, UK] and anti-free κ and -free λ [FLC-MS]) covalently attached to paramagnetic microparticles were separately incubated with serum, washed, treated to elute and reduce patient immunoglobulins, and spotted onto MALDI plates with HCCA matrix. Spectra were generated using the MALDI-TOF-MS system. Light chain mass spectra were obtained using EXENT software to yield immunoglobulin isotype, mass-to-charge ratio (m/z) and quantity (g/L). Results were compared to serum protein electrophoresis, immunofixation, and FLC ratios (Freelite®, The Binding Site, UK). Results: EXENT demonstrated improved sensitivity over immunofixation for identifying the M-protein at each time-point of the MM5 trial: 99% vs. 95% at baseline; 91% vs 80% post-induction; and 63% vs. 46% post-consolidation. Agreement between methods was 87%. The addition of FLC-MS to EXENT further improved sensitivity to 100%, 95.0%, and 72% at each respective time-point, whereas the combination of immunofixation and FLC ratios resulted in sensitivities of 100%, 90%, and 54%. Overall concordance between EXENT+FLC-MS and the combination of immunofixation and FLC ratios was 100% at baseline, 93% post-induction, and 73% post-consolidation. In all, 158 (11%) samples had an M-protein by EXENT+FLC-MS only, and 28 (2%) by the combination of immunofixation and FLC ratios. 18 and 92 patients achieved an IMWG complete response after induction and consolidation, respectively. EXENT identified an M-protein in 5 (28%), and 23 (25%) of these patients, whereas EXENT+FLC-MS was more sensitive and detected monoclonal proteins in 11 (61%), and 38 (41%) patients, respectively. There was acceptable quantitative agreement for M-protein measurements between EXENT and serum protein electrophoresis (n=631: Passing-Bablok fit: y=0.85x-0.58; coefficient of determination R2= 0.89; Bland-Altman relative bias (95%CI): -32.62% (-123.79-58.55%)). However, there was a substantial discordance in 285 samples <10g/L by serum protein electrophoresis (y=0.58x+0.54; R2=0.28; -44.84% (-179.29 – 84.60%)) compared to 346 samples >10g/L (y=0.85x-0.25; R2=0.82; -19.91% (95%CI: -97.32 – 23.56%)); suggesting overestimation by serum protein electrophoresis at lower levels. Summary/Conclusion: EXENT provides superior performance for the identification of M-proteins throughout monitoring. Sensitivity can be improved by incorporating FLC-MS assessments, thus providing a means for determining serological residual disease in patients at complete response by IMWG criteria. Quantification of the M-protein by mass spectrometry compares well to standard methods and offers accurate results at levels below the analytical threshold of confidence for electrophoretic approaches.

Aiding early clinical drug development by elucidation of the relationship between tumor growth inhibition and survival in relapsed/refractory multiple myeloma patients.

Early prognosis of clinical efficacy is an urgent need for oncology drug development. Herein, we systemically examined the quantitative approach of tumor growth inhibition (TGI) and survival modeling in the space of relapsed and refractory multiple myeloma (MM), aiming to provide insights into clinical drug development. Longitudinal serum M‐protein and progression‐free survival (PFS) data from three phase III studies (N = 1367) across six treatment regimens and different patient populations were leveraged. The TGI model successfully described the longitudinal M‐protein data in patients with MM. The tumor inhibition and growth parameters were found to vary as per each study, likely due to the patient population and treatment regimen difference. Based on a parametric time‐to‐event model for PFS, M‐protein reduction at week 4 was identified as a significant prognostic factor for PFS across the three studies. Other factors, including Eastern Cooperative Oncology Group performance status, prior anti‐myeloma therapeutics, and baseline serum ß2‐microglobulin level, were correlated with PFS as well. In conclusion, patient disease characteristics (i.e., baseline tumor burden and treatment lines) were important determinants of tumor inhibition and PFS in MM patients. M‐protein change at week 4 was an early prognostic biomarker for PFS.

Joint modelling and simulation of M-protein dynamics and progression-free survival for alternative isatuximab dosing with pomalidomide/dexamethasone.

AimsAddition of isatuximab (Isa) to pomalidomide/dexamethasone (Pd) significantly improved progression‐free survival (PFS) in patients with relapsed/refractory multiple myeloma (RRMM). We aimed to characterize the relationship between serum M‐protein kinetics and PFS in the phase 3 ICARIA‐MM trial (NCT02990338), and to evaluate an alternative dosing regimen of Isa by simulation.MethodsData from the ICARIA‐MM trial comparing Isa 10 mg/kg weekly for 4 weeks then every 2 weeks (QW‐Q2W) in combination with Pd versus Pd in 256 evaluable RRMM patients were used. A joint model of serum M‐protein dynamics and PFS was developed. Trial simulations were then performed to evaluate whether efficacy is maintained after switching to a monthly dosing regimen.ResultsThe model identified instantaneous changes (slope) in serum M‐protein as the best on‐treatment predictor for PFS and baseline patient characteristics impacting serum M‐protein kinetics (albumin and β2‐microglobulin on baseline levels, non‐IgG type on growth rate) and PFS (presence of plasmacytomas). Trial simulations demonstrated that switching to a monthly Isa regimen at 6 months would shorten median PFS by 2.3 weeks and induce 42.3% patients to progress earlier.ConclusionsTrial simulations supported selection of the approved Isa 10 mg/kg QW‐Q2W regimen and showed that switching to a monthly regimen after 6 months may reduce clinical benefit in the overall population. However, patients with good prognostic characteristics and with a stable, very good partial response may switch to a monthly regimen after 6 months without compromising the risk of disease progression. This hypothesis will be tested in a prospective clinical trial.

Population pharmacokinetic and exposure\u2013response analyses of elotuzumab plus pomalidomide and dexamethasone for relapsed and refractory multiple myeloma

PurposeElotuzumab plus pomalidomide/dexamethasone (E-Pd) demonstrated efficacy and safety in relapsed and refractory multiple myeloma (RRMM). The clinical pharmacology of elotuzumab [± lenalidomide/dexamethasone (Ld)] was characterized previously. These analyses describe elotuzumab population pharmacokinetics (PPK), the effect of Pd, and assess elotuzumab exposure–response relationships for efficacy and safety in patients with RRMM.MethodsA previously established PPK model was updated with E-Pd data from the phase 2 ELOQUENT-3 study (NCT02654132). The dataset included 8180 serum concentrations from 440 patients with RRMM from 5 clinical trials. Elotuzumab PK parameter estimates were used to generate individual daily time-varying average concentrations (daily Cavg) for multi-variable time-to-event exposure–response analyses of progression-free survival (PFS) and time to the first occurrence of grade 3 + adverse events (AEs) in RRMM.ResultsElotuzumab PK were well-described by a two-compartment model with parallel linear and Michaelis–Menten elimination from the central compartment (Vmax) and non-renewable target-mediated elimination from the peripheral compartment (Kint). Co-administration with Pd resulted in a 19% and 51% decrease in elotuzumab linear clearance and Kint, respectively, versus Ld; steady-state exposures were similar. Vmax increased with increasing serum M-protein. Hazard ratios (95% confidence intervals) for daily Cavg were 0.9983 (0.9969–0.9997) and 0.9981 (0.9964–0.9998) for PFS and grade 3 + AEs, respectively.ConclusionsThe PPK model adequately described the data and was appropriate for determining exposures for exposure–response analyses. There were no clinically relevant differences in elotuzumab exposures between Pd and Ld backbones. In ELOQUENT-3, increasing elotuzumab daily Cavg prolonged PFS without increasing grade 3 + AEs.

Relationship of tumor load parameters before and after autologous stem cell transplantation with clinical prognosis in transplant-eligible patients with multiple myeloma: A retrospective analysis

We retrospectively examined 57 patients with multiple myeloma who underwent autologous stem cell transplantation (ASCT) at our institution. A receiver-operating characteristic curve (ROC) analysis showed that the reduction rate of quantitative serum monoclonal protein (M-protein) before ASCT and the difference in involved and uninvolved free light chains (dFLC) 30 days after ASCT, respectively, had the greatest predictive value for all patients (area under the curve [AUC] 0.791 and 0.660, respectively). Based on the ROC curve-based cutoff values of tumor burden parameters, progression-free survival (PFS) in the high serum M-protein reduction (≥90 %) group was significantly better than that in the low serum M-protein reduction group (<90 %) (2-year PFS 79.5 % vs. 17.0 %, p < 0.001), but there were no significant differences in PFS between the low (<5.2 mg/L) and high (≥5.2 mg/L) dFLC groups (2-year PFS, 72.0 % vs. 46.0 %; p = 0.149). A multivariate analysis identified the reduction in serum M-protein as an independent predictive factor before ASCT for PFS (hazard ratio [HR] 0.287, p = 0.022) and high dFLC on day 30 after ASCT for PFS (HR 3.902, p = 0.040). These results demonstrate that a good prognosis can be expected with a reduction of serum M-protein before and after ASCT.

Validated Method Based on Immunocapture and Liquid Chromatography Coupled to High-Resolution Mass Spectrometry to Eliminate Isatuximab Interference with M-Protein Measurement in Serum

In multiple myeloma (MM) disease, malignant plasma cells produce excessive quantities of a monoclonal immunoglobulin (Ig), known as M-protein. M-protein levels are measured in the serum of patients with MM using electrophoresis techniques to determine the response to treatment. However, therapeutic monoclonal antibodies, such as isatuximab, may confound signals using electrophoresis assays. We developed a robust assay based on immunocapture and liquid chromatography coupled to high-resolution mass spectrometry (IC-HPLC-HRMS) in order to eliminate this interference. Following immunocapture of Ig and free light chains (LC) in serum, heavy chains (HC) and LC were dissociated using dithiothreitol, sorted by liquid chromatography and analyzed using HRMS (Q-Orbitrap). This method allowed the M-proteins to be characterized and the signals from isatuximab and M-proteins to be discriminated. As M-protein is specific to each patient, no standards were available for absolute quantification. We therefore used alemtuzumab (an IgG kappa mAb) as a surrogate analyte for the semiquantification of M-protein in serum. This assay was successfully validated in terms of selectivity/specificity, accuracy/precision, robustness, dilution linearity, and matrix variability from 10.0 to 200 μg/mL in human serum. This method was used for clinical assessment of samples and eliminated potential interference due to isatuximab when monitoring patients with MM.

M-Protein Sequencing and Monitoring in Serum of LC-Only Multiple Myeloma Patients

M-Protein Sequencing and Monitoring in Serum of LC-Only Multiple Myeloma Patients

Prevalence of Smoldering Multiple Myeloma: Results from the Iceland Screens, Treats, or Prevents Multiple Myeloma (iStopMM) Study

Prevalence of Smoldering Multiple Myeloma: Results from the Iceland Screens, Treats, or Prevents Multiple Myeloma (iStopMM) Study

Assessment of Associations between Derived Response and Overall Survival in Patients with Multiple Myeloma Using a US-Based Electronic Health Records Database

Assessment of Associations between Derived Response and Overall Survival in Patients with Multiple Myeloma Using a US-Based Electronic Health Records Database

Characteristics and Outcomes of Non-Transplanted Patients with Newly Diagnosed Multiple Myeloma (NDMM) Initiating Treatment with Bortezomib, Lenalidomide, and Dexamethasone (VRd) As First-Line of Therapy

Introduction: In the US, bortezomib, lenalidomide, and dexamethasone (VRd) is one of the preferred treatment regimens in transplant-ineligible patients with newly diagnosed multiple myeloma (NDMM) based on the results from the phase 3 Southwest Oncology Group (SWOG) S0777 study. Although the efficacy of VRd in transplant-ineligible or -deferred NDMM patients was demonstrated in SWOG S0777, clinical trials have strict eligibility criteria that may not translate to the real-world. There is limited real-world data on the characteristics and outcomes of non-transplanted patients with NDMM treated with VRd, especially in older, frail patients with comorbidities. This study aimed to address these knowledge gaps by evaluating the characteristics and outcomes of patients with NDMM who received VRd as first-line of therapy (LOT) in US oncology practice.Methods: This retrospective observational study included patients from the Flatiron Multiple Myeloma Core Registry who received VRd as first LOT between November 1, 2015 and February 28, 2021. The index date was defined as the first observed record of the VRd regimen. Non-transplanted patients were defined as those who did not receive a stem cell transplant (SCT) from the diagnosis date to the index date. Patients were excluded if they were <18 years of age on index date; were enrolled in a clinical trial; had other malignancies prior to the index date; had a diagnosis of amyloid light-chain amyloidosis prior to the index date; or had a SCT prior to index date. Demographics, clinical characteristics, and outcomes were assessed in the overall study cohort and among specific subgroups: older adults (≥75 years of age on index date); frail patients (frailty score ≥2, calculated using age on index date, Charlson Comorbidity Index during the pre-index period, and Eastern Cooperative Oncology Group performance status [ECOG PS] score on the closest date to the index date ≤90 days prior to and ≤7 days after the index date, patients with missing ECOG were not excluded); patients with high-risk cytogenetics, and patients with acute renal impairment ([RI], serum creatinine >2 mg/dL on the closest date to the index date or having diagnosis codes of ICD-9-CM 584.5-584.9, ICD-9-CM 586, ICD-10-CM N17.0-2, N17.8-9, and N19, measured ≤90 days prior to and ≤7 days after the index date). Duration of therapy was measured as the time between the index date and end of the LOT. Progression-free survival (PFS) was measured as time between the index date and disease progression or death, whichever occurred first. PFS did not account for treatment discontinuation for reasons other than progression or death. Disease progression was defined as a clinically meaningful increase in serum M-protein, urine M-protein, or the free light chain ratio according to the International Myeloma Working Group criteria. PFS was analyzed using the Kaplan-Meier method.Results: A total of 2342 eligible NDMM patients treated with VRd as first LOT were identified, with a median follow-up of 21.0 months. A majority of patients were ≥65 years (64.3%), with the mean (SD) age at index date being 67 (±10) years. Most patients were male (53.3%), had International Staging System [ISS] stage I/II (48.4%; 33% missing) and the ECOG PS score 0/1 (63.5%; 22% missing). Of the 2342 patients, 597 (25.5%) patients were categorized as older adults (≥75 years of age); 1122 (47.9%) as frail; 374 (16.0%) as patients with high-risk cytogenetics; and 250 (10.7%) as patients with RI. About 28% of the patients received a SCT within 1-year of the index date. The median duration of therapy was 5.6 months. The median PFS for the overall study group was 33.2 months. Median PFS was substantially shorter for patients who were ≥75 years of age (22.8 months), were frail (28.7 months), had high-risk cytogenetics (25.1 months), or had RI (25.1 months) (Figure).Conclusions: The majority of patients with NDMM treated with VRd in the real-world setting were aged ≥65 years, were ISS stage I or II, had an ECOG PS score of 0 or 1, and had standard-risk cytogenetics. Median PFS observed in the real-world setting was shorter than that observed in the SWOG S0777 clinical trial. Patients who were ≥75 years of age, were frail, had high-risk cytogenetics, or had RI demonstrated shorter median PFS than patients in the overall study population. Alternate treatment options with demonstrated efficacy in the older, frail, and transplant ineligible patients are available. [Display omitted] DisclosuresMedhekar: Janssen: Current Employment. Ran: Janssen Scientific Affairs, LLC: Current Employment. Fu: Janssen: Current Employment. Patel: Janssen: Current Employment. Kaila: Janssen Scientific Affairs, LLC: Current Employment. OffLabel Disclosure:Bortezomib, and lenalidomide are both FDA approved agents for treating multiple myeloma. The combination of bortezomib, lenalidomide, and dexamethasone is commonly used in clinical practice and is listed as a preferred regimen in NCCN guidelines.

Selective Cell State in the Clonally Expanded T-Cell Compartment of Vκ*MYC Mice Responding to Treatment with Checkpoint Inhibitors

Introduction: Immune checkpoint receptor (ICR) blockade has emerged as an effective anti-tumour modality, but only in a subset of cancer patients. Moreover, in Multiple myeloma (MM), single-agent activity has not been observed, highlighting the need to better understand the mechanism of action of this class of drugs. We recently showed that combinatorial ICR blockade using αLAG3 and αPD-1 delays disease progression and improves survival in the transplantable Vκ*MYC model of MM (Croucher et al. ASH 2018). However, despite this being a controlled study with genetically-homogeneous tumours, anti-tumour immune responses were heterogeneous, with only a subset of mice demonstrating a delay in tumour progression (17/29 mice, response rate = 58.6%). Thus, using this model, we set out to define mechanisms underlying variability in response to ICR blockade.Methods: We established a cohort of mice by engrafting 5-week-old C57BL/6 mice with Vκ12598 cells via tail vein injection. Treatment with αLAG3/αPD-1 or Ig-control was initiated 1-week post-engraftment and bone marrow (BM) samples were collected 3 weeks after the start of treatment. Following FACS-enrichment of T cells and plasma cells (PCs), single cell suspensions were subjected to matched single-cell gene expression (5' scRNA-seq) and T cell receptor (TCR)/B cell receptor (BCR) profiling (10x Genomics).Results: Samples were selected for profiling based on response to treatment, with responders (n=4) defined by significantly lower disease burden compared to non-responders (n=3) and control-treated mice (n=5), as measured by serum M-protein and %PCs in BM/spleen at sacrifice. Unsupervised clustering of scRNA-seq data from PCs (n=3,318 cells) identified no gene expression or BCR repertoire differences between control and treated, or between responder and non-responder samples, supporting that variability in response was not related to malignant Vκ12598 cells themselves. Across all samples, a statistically significant difference was not detected between the total number of unique TCR sequences (clonotypes) comparing control-treated (351-2369), non-responders (1185-2327) and responders (1378-1698), with no overlapping TCR sequences between top clonotypes. Evaluation of TCR repertoire diversity revealed that αLAG3/αPD-1 treatment induces clonal T cell expansion in control versus treated mice, but this was not significantly different between responders and non-responders. Analysis of paired scRNA-seq data (n=21,520 cells) revealed that expanded T cells from αLAG3/αPD-1-treated mice occupy a different cell state in responder vs. non-responder mice. We speculate that underlying differences in the TCR repertoire may dictate the downstream phenotype of expanded, anti-tumour T cells in mice treated with combinatorial αLAG3/αPD-1. Tumour control following treatment was associated with clonal expansion of T cells expressing genes related to cytoxicity and activation (Ccl5, Ifng, Fasl, Gzmb), whereas tumour progression was associated with clonal expansion of proliferative T cells (Cdkn3, Birc5, Ccna2, Aurka, Mki67). Although T cell proliferation is typically a phenotype ascribed to effector T cells, recent studies have similarly observed this proliferative cell state in dysfunctional T cells within melanoma tumours. Moreover, emerging evidence supports suppression of T cell proliferation by CDK4/6 inhibitors as a means to augment anti-tumour activity of ICR-based therapy. Thus, studies exploring whether reversal of the observed proliferative T cell state can restore response to αLAG3/αPD-1 treatment in non-responding Vκ12598 mice are ongoing and will be reported.Conclusions: ICR inhibitors demonstrate significant activity in some cancers, however many patients fail to respond and a similarly promising level of efficacy has not been achieved in MM. Studies aimed at unraveling the mechanisms of response and resistance to ICR inhibitors are therefore needed to improve the utility of this class of drugs for all patients. Our approach of using paired single-cell gene expression and TCR repertoire profiling has enabled identification of molecular cell states specifically in expanded T cells of responder vs. non-responder mice. In turn, our work nominates novel mechanisms that may be used as potential biomarkers for anti-tumour immune responses as well as potential targets to augment responses to ICR blockade therapy. DisclosuresChesi: Abcuro: Patents & Royalties: Genetically engineered mouse model of myeloma; Novartis: Consultancy, Patents & Royalties: human CRBN transgenic mouse; Pfizer: Consultancy; Pi Therapeutics: Patents & Royalties: Genetically engineered mouse model of myeloma; Palleon Pharmaceuticals: Patents & Royalties: Genetically engineered mouse model of myeloma. Bergsagel: GSK: Consultancy, Honoraria; Genetech: Consultancy, Honoraria; Janssen: Consultancy, Honoraria; Oncopeptides: Consultancy, Honoraria; Novartis: Consultancy, Honoraria, Patents & Royalties: human CRBN mouse; Pfizer: Consultancy, Honoraria; Celgene: Consultancy, Honoraria. Sebag: Janssen: Research Funding; Bristol Myers-Squibb: Consultancy, Honoraria; Takeda: Consultancy, Honoraria; Novartis: Consultancy, Honoraria; Amgen: Consultancy, Honoraria; Sanofi: Consultancy, Honoraria; Karyopharm Therapeutics: Consultancy, Honoraria. Trudel: BMS/Celgene: Consultancy, Honoraria, Research Funding; Amgen: Honoraria, Research Funding; Janssen: Honoraria, Research Funding; GlaxoSmithKline: Consultancy, Honoraria, Research Funding; Roche: Consultancy; Sanofi: Honoraria; Pfizer: Honoraria, Research Funding; Genentech: Research Funding.

Magnetismm-3: An Open-Label, Multicenter, Non-Randomized Phase 2 Study of Elranatamab (PF-06863135) in Patients with Relapsed or Refractory Multiple Myeloma

Background: Multiple myeloma (MM) is a hematological B-cell malignancy that remains incurable for most patients. Almost all patients, including those who initially respond to treatment, are expected to relapse and subsequently cycle through multiple lines of treatment. The addition of proteasome inhibitors, immunomodulatory drugs and monoclonal antibodies has improved patient outcomes; however, survival of patients after these agents is very poor and highlights an unmet medical need in the relapsed/refractory MM population. Elranatamab (PF-06863135) is a humanized bi-specific antibody that targets both BCMA-expressing MM cells and CD3-expressing T cells, with binding resulting in T-cell mediated cytotoxicity. Elranatamab preclinical studies have demonstrated anti-tumor activity and delayed tumor progression. A Phase 1 study, MagnetisMM-1 (ClinicalTrials.gov ID: NCT03269136), with the aim of characterizing the efficacy, safety, pharmacokinetics, and pharmacodynamics of elranatamab as single agent and in combination with immunomodulatory agents for patients with relapsed/refractory MM is ongoing.Study Design and Methods: MagnetisMM-3 is an open-label, multicenter, non-randomized, Phase 2 study to evaluate the efficacy and safety of elranatamab monotherapy in patients with relapsed/refractory MM who are refractory to at least one proteasome inhibitor, one immunomodulatory drug, and one anti-CD38 antibody (ClinicalTrials.gov ID: NCT04649359). Approximately 150 patients will be enrolled to one of two independent parallel cohorts: those naïve to BCMA-directed therapies (Cohort A) and those with previous exposure to BCMA-directed therapy (Cohort B). The primary endpoint is objective response rate, according to International Myeloma Working Group [IMWG] response criteria. Secondary endpoints include duration of response, cumulative complete response (CR) rate, duration of cumulative CR, progression-free survival, time to response, minimal residual disease negativity rate, overall survival, safety, plasma concentrations, and immunogenicity of elranatamab.Key inclusion criteria are age ≥18 years, MM diagnosis according to IMWG criteria and with measurable disease based on IMWG criteria as defined by at least 1 of the following: Serum M-protein ≥0.5 g/dL by SPEP, Urinary M-protein excretion ≥200 mg/24 hours by UPEP; Serum immunoglobulin free light chain ≥10 mg/dL (≥100 mg/L) and abnormal serum immunoglobulin kappa to lambda free light chain ratio (<0.26 or >1.65). Eligible patients should also have ECOG performance status ≤2, be refractory to at least one proteasome inhibitor, one immunomodulatory drug, and one anti-CD38 antibody and be relapsed/refractory to their last treatment regimen. Key exclusion criteria are smoldering MM, active plasma cell leukemia, amyloidosis, POEMS syndrome, active, uncontrolled bacterial, fungal or viral infections, stem cell transplant within 12 weeks of enrollment, any other active malignancy within 3 years prior to enrollment (except for adequately treated basal cell or squamous cell skin cancer, or carcinoma in situ), or having received previous administration of an investigational drug within 30 days or 5 half-lives (whichever is longer) of the first dose of elranatamab. This study is, or is planned to be, open at centers in the USA, Australia, Canada, Belgium, France, Germany, Japan, Poland, Spain, and the UK. DisclosuresLesokhin: Genetech: Research Funding; Serametrix, Inc: Patents & Royalties; pfizer: Consultancy, Research Funding; Behringer Ingelheim: Honoraria; Trillium Therapeutics: Consultancy; bristol myers squibb: Research Funding; Iteos: Consultancy; Janssen: Honoraria, Research Funding. Iida: Ono: Honoraria, Research Funding; Glaxo SmithKlein: Research Funding; Janssen: Honoraria, Research Funding; Abbvie: Research Funding; Chugai: Research Funding; Celgene: Honoraria, Research Funding; Sanofi: Honoraria, Research Funding; Takeda: Honoraria, Research Funding; Bristol-Myers Squibb: Research Funding; Daiichi Sankyo: Research Funding; Amgen: Research Funding. Ma: Pfizer Inc: Current Employment, Current equity holder in publicly-traded company. Sullivan: Pfizer Inc: Current Employment, Current equity holder in publicly-traded company. Raab: Janssen: Membership on an entity's Board of Directors or advisory committees; Abbvie: Consultancy, Honoraria; Amgen: Consultancy, Membership on an entity's Board of Directors or advisory committees; BMS: Consultancy, Membership on an entity's Board of Directors or advisory committees; GSK: Honoraria, Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees, Research Funding; Sanofi: Membership on an entity's Board of Directors or advisory committees, Research Funding; Roche: Consultancy; Celgene: Membership on an entity's Board of Directors or advisory committees.

Single-Cell Transcriptomic Analysis Reveals Loss of Activated Bone Marrow NK Cells in Multiple Myeloma Patients Which Associates with Disease Progression in Mice

IntroductionMultiple Myeloma (MM) disease progression and therapy response are the net result of tumor cell-intrinsic features and tumor cell-extrinsic cues from the bone marrow (BM) microenvironment. Natural killer (NK) cells are mediators of the cytotoxic immune response against MM and are important effector cells in antibody-based immune therapies, especially anti-CD38 monoclonal antibodies such as Daratumumab. Classically, NK cells are divided into a cytotoxic CD56 dim subset, important for antibody-dependent cellular cytotoxicity, and a cytokine-producing CD56 bright subset releasing inflammatory mediators such as IFNγ, TNFα and GM-CSF. However, accumulating evidence suggests greater heterogeneity in the NK cell compartment and modulation of these NK cell subsets could impact disease progression and response to NK cell-driven immunotherapies. Here, we combined the 5TGM1 murine model of MM with single-cell RNA sequencing of bone marrow (BM) NK cells of newly diagnosed MM patients to map NK cell heterogeneity and to investigate their role in MM progression.ResultsTo gain insight in NK cell heterogeneity in MM disease we performed single-cell RNA sequencing on immune cells of viably frozen BM aspirates from 19 newly diagnosed MM patients and 5 non-cancer control patients. NK cells were identified in silico by transcription of KLRF1, KLRD1, GNLY and NKG7 resulting in a single-cell transcriptomic dataset of 30,373 NK cells from MM patients and 8,865 NK cells from control patients. Conventional CD56 bright and CD56 dim NK-cells were identified by increased transcription of GZMK or GZMB, respectively. The GZMK +CD56 bright NK cells contained clusters of naïve and activated NK cells. The GZMB+CD56 dim NK cells consisted of 5 subclusters. To identify MM-induced alterations in NK cell subsets, we compared GZMK +CD56 bright vs GZMB+CD56 dim cluster composition and distribution between controls and MM patients. Control BM was dominated by GZMB-transcribing cytotoxic CD56 dim NK cells, resulting in a low ratio of cytokine-producing GZMK +CD56 bright vs cytotoxic GZMB+CD56 dim NK cells. In contrast, MM bone marrow was characterized by heterogeneity of this ratio with a subset of patients presenting with complete reversal of this ratio . In this subset of patients, the altered composition was due to a loss of cytotoxic GZMB +CD56 dim NK cells, and more specifically a loss of NK cells with a transcriptome suggesting recent activation.To better examine the significance of cytotoxic NK cells in MM disease course we utilized the well-established 5TGM1 mouse model. C57Bl/6 and KaLwRij mice both received 10 6 5TGM1-GFP cells intravenously. Three weeks after tumor injection all KaLwRij mice (18/18) developed MM, defined by >5% tumor cells in BM (“unrestrained tumor”) and serum M-protein >2mg/ml. Interestingly, while 39% (7/18) of C57Bl/6 mice had no tumor, 44% (8/18) had low but detectable levels of MM cells (0.1-5% of BM cells, “restrained tumor”) and 17% (3/18) presented with an unrestrained MM with BM tumor load similar to that seen in KaLwRij mice. With time the percentage of mice with unrestrained tumor increased (5/12, 42%) at the expense of restrained tumor (2/12, 16%). We hypothesized that C57Bl/6 mice with low tumor load could represent a model of immune-mediated tumor control. Detailed analysis of the NK cell compartment revealed an expansion of activated mature (CD69 + CD11b +CD27 +) NK cells in C57Bl/6 mice with restrained BM MM (p=0.0031). In contrast, high BM tumor burden in both genotypes was associated with a sharp decline in absolute numbers of activated NK cells.Conclusion:Through a combination of single-cell transcriptomic analyses of the BM immune microenvironment in MM patients and experimental mouse models we found a loss of activated NK cells in a subset of patients and mice. Our data suggests that loss of these activated NK cells is associated with MM progression in vivo. A subset of MM patients presented with a loss of activated cytotoxic GZMB +CD56 dim NK cells in the BM, suggestive of reduced cytotoxic anti-tumor responses. Meanwhile, in vivo, high disease burden only occurred in mice with an absence of activated NK cells. Current analyses are focused on differences in human disease progression and efficacy of Daratumumab-based therapies in patients with various NK cell phenotypes. DisclosuresBroijl: Janssen, Amgen, Sanofi, Celgene/BMS: Honoraria, Membership on an entity's Board of Directors or advisory committees. Sonneveld: Janssen: Consultancy, Honoraria, Research Funding; Karyopharm: Consultancy, Honoraria, Research Funding; Celgene/BMS: Consultancy, Honoraria, Research Funding; Amgen: Consultancy, Honoraria, Research Funding; SkylineDx: Honoraria, Research Funding; Takeda: Consultancy, Honoraria, Research Funding.

Prognostic Impact of MYD88 L265P Mutation By Droplet Digital PCR in IgM MGUS and Smoldering Waldenström Macroglobulinemia

BACKGROUND: MYD88 L265P mutation is highly prevalent in IgM monoclonal gammopathy of undetermined significance (MGUS), smoldering Waldenström macroglobulinemia (SWM) and symptomatic WM. Allele-specific PCR (AS-PCR) has been used routinely to assess MYD88 mutation; however, with the advent of more precise high-throughput technologies such as droplet digital PCR (ddPCR), absolute quantification can be achieved. There is no data regarding ddPCR applicability in asymptomatic IgM monoclonal gammopathies or as a prognostic biomarker. Here, we aimed to compare MYD88 quantification by ddPCR with clinical and laboratory features and to analyze the prognostic impact in a series of patients (pts) with IgM MGUS and SWM.METHODS: We analyzed bone marrow (BM) and peripheral blood (PB) samples stored from pts diagnosed with IgM MGUS and SWM at our institution from 1980 to 2020. DNA extraction methods followed manufacturer instructions (Qiagen) to obtain genomic DNA from unsorted BM samples and cell-free DNA (cfDNA) from PB. MYD88 L265P mutation was quantified by ddPCR using a Bio-Rad commercial assay (HEX-labeled wild-type allele; FAM-labeled mutant allele). We used OCI-Ly3 DLBCL ABC cell line, homozygous for MYD88 L265P, as a positive control. ddPCR was performed following Bio-Rad technical specifications using the QX200 droplet reader. Data was analyzed using QuantaSoft v.1.0 software (Bio-Rad). Absolute quantification of the mutation was expressed as percentage of fractional abundance. For survival analysis, we used a competing risk analysis to evaluate the prognostic impact of MYD88 mutation on progression to symptomatic WM.RESULTS: A total of 217 unsorted samples were analyzed (187 BM and 30 PB). Genomic DNA from unsorted BM samples was extracted from pts diagnosed with IgM MGUS (46%), SWM (44%), and symptomatic WM (10%). cfDNA was obtained from a subgroup of pts with IgM MGUS (52%) and SWM (48%). Median age at diagnosis was 68 (range 61 to 76). AS-PCR could detect the mutation in 22 (31%) pts with IgM MGUS and 49 (75%) with SWM. ddPCR improved precision detection up to 48 (55%) pts with IgM MGUS and 68 (83%) with SWM. All pts with symptomatic WM harbored the MYD88 mutation, as identified by both techniques. Median absolute quantification from BM was 2.3% and 7% for pts with IgM MGUS and SWM, respectively (p<0.001).Pearson correlation coefficients comparing BM MYD88 mutation quantification by ddPCR with serum M-protein size, IgM concentration, BM lymphoplasmacytic infiltration rate and BM CD19+ cells were 0.3, 0.4, 0.6, and 0.9 (p<0.0004), respectively. Similar coefficients were observed in symptomatic WM regarding BM infiltration rate (0.6; p=0.001) and BM CD19+ cells (0.9; p<0.0001). Spearman correlation coefficients comparing cfDNA MYD88 mutation quantification with BM lymphoplasmacytic infiltration rate and BM CD19+ cells were 0.4 and 0.5 (p<0.008), respectively. Agreement regarding MYD88 mutation detection by ddPCR in BM DNA and cfDNA samples was 82% (Cohen kappa index 0.6).With a median overall survival of 13 years in pts with IgM MGUS and SWM, 13% of them progressed to symptomatic WM while 22% died without progression. Cox univariate analysis using continuous values for MYD88 quantification (p=0.004), serum IgM (p<0.001), BM lymphoplasmacytic infiltration (p<0.001), and serum albumin (p=0.04) were significant. X-tile software was used to find the optimal cutoff point of MYD88 quantification as a biomarker. 4.5% was established for pts with IgM MGUS while 25% for SWM. Using the Fine and Gray regression model in a competing risk analysis taking death without progression as a competing event, higher MYD88 mutation burden negatively impacted the risk of progression of IgM MGUS (SHR 4.6; p=0.003) and SWM (SHR 6; p<0.001) (Figure 1).CONCLUSION: Quantification of the MYD88 L265P mutation by ddPCR has higher precision and sensitivity compared to AS-PCR; thus ddPCR could be used as a potential new and useful biomarker. MYD88 tumor burden correlated with well-known laboratory parameters used for diagnosis and risk stratification, whether using genomic DNA from unsorted BM samples or cfDNA. Risk of progression was higher in patients harboring an increased mutant allele burden. This is the first report showing the prognostic impact of MYD88 quantification in a series of patients with asymptomatic IgM gammopathy and long-term follow up. [Display omitted] DisclosuresCibeira: Akcea: Honoraria, Membership on an entity's Board of Directors or advisory committees; Amgen: Honoraria, Membership on an entity's Board of Directors or advisory committees; Celgene: Honoraria; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees. Bladé Creixenti: Janssen, Celgene, Takeda, Amgen and Oncopeptides: Honoraria. Rosinol: Janssen, Celgene, Amgen and Takeda: Honoraria. Fernandez de Larrea: BMS: Consultancy, Honoraria, Research Funding; Amgen: Consultancy, Honoraria, Research Funding; Takeda: Honoraria, Research Funding; GSK: Honoraria; Sanofi: Consultancy; Janssen: Consultancy, Honoraria, Research Funding.

A Randomized Placebo-Controlled Phase 2 Study of Metformin for the Prevention of Progression of Monoclonal Gammopathy of Undetermined Significance and Low Risk Smoldering Multiple Myeloma

Background: Multiple Myeloma (MM) is thought to evolve from the precursor conditions monoclonal gammopathy of undetermined significance (MGUS) and smoldering MM (SMM), which are common premalignant disorders that progress to overt MM in a subset of individuals for reasons that are poorly understood. Despite increasing interest in preventing disease progression in this patient population, the standard of care still consists of close surveillance until progression to MM; however, once MM develops it cannot be cured. Therefore, the identification of prevention and interception strategies for patients with MGUS and SMM is of considerable importance.A promising pharmacologic intervention to reduce the risk of progression of MGUS/SMM to MM is metformin, a drug commonly used to treat type 2 diabetes but that is also considered safe for use in non-diabetic populations. In vivo and in vitro studies have revealed that metformin has direct antitumor effects across a variety of cancers including MM, and recent epidemiological data suggests it may reduce the risk of MM in diabetic patients with MGUS. Here, we describe the first randomized controlled trial testing the efficacy of metformin in reducing clinical signs of disease progression in patients with MGUS and SMM (NCT04850846).Study Design and Methods: This is a phase II single center, randomized controlled trial of metformin vs. placebo in patients with high-risk MGUS and low-risk SMM. The primary objective of the study is to determine whether metformin can reduce or stabilize serum monoclonal (M-)protein concentrations from baseline to 6-months. Exploratory objectives include mass spectrometry quantification of M-protein, examination of molecular evolution of tumor cells in response to metformin, as well as changes in other clinical laboratory parameters in response to metformin.To be eligible, patients must have high-risk MGUS or low-risk SMM. High-risk MGUS is defined as bone marrow plasma cell concentration <10% with one or more of the following higher-risk features: serum M-protein level ≥1.5 g/dL to <3 g/dL or abnormal free light-chain (FLC) ratio (<0.26 or>1.65); a forthcoming amendment will include non-IgG subtype as an additional high-risk feature. Low-risk SMM is defined as bone marrow plasma cells ≥10%with the absence of any features of high-risk SMM.Metformin and its corresponding placebo are the pharmacological treatments. The metformin dose is 1500 milligrams/day, provided in 500 milligram pills. To minimize gastrointestinal symptoms, metformin is started at a low dose of 500 milligram (1 pill) per day and participants gradually increase the dosage over the course of the first month of treatment until the full 1500 milligram (3 pill) per day regimen is achieved. The study treatment period is 6 months, with primary outcomes assessed at the end of the 6-month treatment period.Conclusions and Future Directions: While the cornerstone of clinical management in MGUS and SMM is to delay therapy until progression to symptomatic MM, patients and oncologists continually seek new ways to prevent end organ damage and incurable malignancy. This trial is positioned to provide preliminary but robust mechanistic data to support the development of novel prevention strategies for MGUS and SMM patients. DisclosuresMarinac: GRAIL Inc: Research Funding; JBF Legal: Consultancy. Sperling: Adaptive: Consultancy. Parnes: Sigilon: Membership on an entity's Board of Directors or advisory committees; Genentech: Membership on an entity's Board of Directors or advisory committees; UniQure: Membership on an entity's Board of Directors or advisory committees; Sunovion: Consultancy; I-mAb: Consultancy; Aspa: Consultancy; Genentech/Hoffman LaRoche: Research Funding; Shire/Takeda: Membership on an entity's Board of Directors or advisory committees, Research Funding. Richardson: Protocol Intelligence: Consultancy; Regeneron: Consultancy; Sanofi: Consultancy; Secura Bio: Consultancy; AbbVie: Consultancy; Janssen: Consultancy; GlaxoSmithKline: Consultancy; AstraZeneca: Consultancy; Karyopharm: Consultancy, Research Funding; Takeda: Consultancy, Research Funding; Celgene/BMS: Consultancy, Research Funding; Oncopeptides: Consultancy, Research Funding; Jazz Pharmaceuticals: Consultancy, Research Funding. Ghobrial: AbbVie, Adaptive, Aptitude Health, BMS, Cellectar, Curio Science, Genetch, Janssen, Janssen Central American and Caribbean, Karyopharm, Medscape, Oncopeptides, Sanofi, Takeda, The Binding Site, GNS, GSK: Consultancy. Nadeem: Karyopharm: Membership on an entity's Board of Directors or advisory committees; Adaptive Biotechnologies: Membership on an entity's Board of Directors or advisory committees; Takeda: 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. OffLabel Disclosure:metformin, which is an anti-diabetic medication

P-064: Heterogeneity of bone marrow biopsy and bone marrow aspirate (BMA) in patients with heavily pretreated relapsed/refractory Multiple Myeloma (RRMM)

<h3>Background</h3> Despite new regimens approved for RRMM, patients still relapse, and new therapies are needed. T-cell directed therapies that target bone marrow plasma cells (BMPCs), including CD3 bispecific antibodies, have shown promise for the treatment of RRMM. REGN5458, a B-cell maturation antigen (BCMA) xCD3 bispecific antibody, demonstrated an acceptable safety and tolerability profile with early, deep, and durable efficacy in heavily pretreated and triple refractory patients with RRMM [1]. <h3>Aim</h3> To elucidate disease aspects amenable to T-cell-directed therapies targeting plasma cells, such as REGN5458, we characterized the plasma and immune composition of baseline BMA and core biopsies from patients with RRMM, and evaluated relationships between bone marrow profile, secretory measures of disease, and response. <h3>Methods</h3> Patients with progressive RRMM (triple refractory or intolerant to prior lines of systemic therapy, including a proteasome inhibitor, immunomodulatory agent, and anti-CD38 antibody), were treated with REGN5458 (NCT03761108). Matched BMA and biopsy samples obtained at screening were analyzed by multiplex immunohistochemistry (IHC, N=48) and multiparameter flow cytometry (N=81). Cell numbers and phenotypes were correlated to secretory measures of disease, including serum M-protein, immunoglobulin-free light chain (FLC) assays and R-ISS staging. <h3>Results</h3> Biopsy analysis revealed a variable BMPC burden in RRMM patients. Median percentage of BMPCs by CD138 IHC was 22.5% (range 1–95%). There was no correlation between BMPC burden and serum M-protein levels, but a modest correlation between BMPC burden and serum FLC (rho=0.66; p=0.01). The majority of CD138 biopsy BMPCs in RRMM patients expressed BCMA by IHC; levels varied between patients (median BCMA+ H scores: 45 and 200 for membrane and cytoplasmic staining). BCMA IHC expression was not associated with IMWG response to REGN5458,¹ and did not correlate with soluble BCMA levels at study initiation. BMA analysis by flow cytometry revealed variable levels of abnormal BMPCs in patients with RRMM (median: 2.2% [range 0–68.7%]). BCMA expression was variable in all BMPCs; 53.1% of patients had higher BCMA staining intensity relative to CD38: ratios ranged from 1.2–6.6. Frequency of CD3+ T-cells in CD45+ BMA from RRMM patients ranged from 1.0–63.5%. Preliminary analysis suggests a higher frequency of T cells in R-ISS stage I compared to stage II. T-cell subset distribution in BMA from patients with RRMM reflected low CD8 T_CM (5.0%) and predominantly T_EM (37.0%) and T_EMRA (41.0%). <h3>Conclusions</h3> Analyses of matched BMA and biopsy samples from heavily pretreated RRMM patients, reveal that most BMPC express BCMA, though soluble vs membrane-bound BCMA levels are heterogenous. Diversity in immune and plasma cell markers and subsets is also observed. Ongoing analyses include correlations of plasma and immune cell profile with response to T-cell-targeting therapies such as REGN5458.

P-072: Progression and dissemination of experimental multiple myeloma is associated with loss of innate and adaptive immune-mediated tumor control

<h3>Background</h3> Multiple myeloma (MM) is an incurable plasma cell malignancy and identifying mechanisms driving disease progression and relapse is crucial for development of novel therapies. Although cytotoxic immunity is an important factor in controlling tumor progression, the cells and signals that constitute an effective anti-myeloma immune response within the bone marrow (BM) are incompletely defined. In this study we set out to identify immune-related mechanisms of disease progression in a murine model of MM. <h3>Methods</h3> C57Bl/6 and KaLwRij mice received 106 5TGM1-GFP murine myeloma cells intravenously. Tumor development was monitored through weekly measurements of M-protein levels. <h3>Results</h3> Three weeks after tumor injection all KaLwRij mice (18/18) developed myeloma, as defined by >5% tumor cells in BM ("unrestrained tumor") and serum M-protein >2mg/ml, and in all mice tumor cells had infiltrated the spleen. Interestingly, while 39% (7/18) of C57Bl/6 mice had no tumor, 44% (8/18) had low but detectable levels of MM cells (0.1-5% of BM cells, "restrained tumor") while 17% (3/18) presented with an unrestrained myeloma with BM tumor load similar to that seen in KaLwRij mice. In all C57Bl/6 mice MM was confined to the bone marrow with no splenic involvement at day 21. When tumor development in 5TGM1-injected C57BL/6 mice was allowed to proceed for a prolonged period of time, the incidence of mice developing a tumor did not change (59%, 7/12 mice). However, the number of mice with unrestrained tumor increased to 42% (5/12 mice), and 2 out of these 5 mice also developed splenic MM involvement. In addition, 17% (2/12) of mice were characterized by restrained tumor, as they contained low but detectable tumor levels up until 42 days post tumor cell transfer. The time-dependent increase in incidence of mice with high tumor burden suggests an initial immune-mediated restraint of MM that eventually fails, leading first to unrestrained BM disease and then to systemic spread of the tumor. The C57Bl/6 mice with restrained bone marrow myeloma had an expansion of activated mature (CD69+ CD11b+) NK cells as well as activated (Lsel-CD44+CD69+) CD8+ cytotoxic T cells. In contrast, high bone marrow tumor burden and spread of MM cells to the spleen was associated with a sharp decline in the absolute numbers of both these cytotoxic immune cell subsets. <h3>Conclusion</h3> Here we provide evidence that loss of innate and adaptive cytotoxic immune populations is associated with progression and dissemination of experimental MM in mice. Transfer of 5TGM1 myeloma cells into C57Bl/6 mice leads to initial tumor control via expansion of innate and adaptive cytotoxic immune cell populations. However, with time, immune-mediated restraint of MM fails, exemplified by loss of NK cell and CD8+ T cell expansion, culminating in tumor outgrowth in the BM and eventual systemic dissemination. This in vivo model will allow for generation of novel insights into the mechanisms of immune escape by MM cells.

P-006: Expanded natural killer cells with daratumumab, lenalidomide and dexamethasone combination potentiates antimyeloma activity in a myeloma xenograft model

<h3>Background</h3> Advances in the treatment of multiple myeloma (MM) significantly improved overall survival of patients. Nonetheless, MM still remains an incurable disease. This emphasizes urgent need for novel combination therapies for the treatment of MM. Recently, natural killer (NK) cells are becoming an attractive and safe tool in the field of immunotherapy. <h3>Methods</h3> Here, we investigated how daratumumab, lenalidomide, and dexamethasone (DRd) treatment potentiate antitumor effects of NK cells in a MM xenograft mouse model. NK cells were expanded and activated using K562-OX40 ligand and membrane-bound IL-18 and IL-21 in the presence of IL-2 and IL-15 from peripheral blood mononuclear cells of MM patients. A human MM xenograft model was established using human RPMI8226-RFP-FLuc cells in NOD/SCID IL-2Rγnull (NSG) mice. Tumor bearing mice were divided into six treatment groups: no treatment, expanded NK cells (eNK), Rd, Rd + eNK, DRd, and DRd + eNK. DRd treatment strongly enhanced the cytotoxicity of eNK by upregulating NK cell's activation ligands and effector function. <h3>Results</h3> DRd combination with eNK significantly prolonged mouse survival and reduced MM progression and serum M-protein level. Moreover, DRd treatment significantly increased eNK persistence and homing into MM sites. <h3>Conclusions</h3> Our findings suggest that DRd treatment augments the anti-myeloma effects of ex vivo expanded and activated NK cells by modulating immune responses in MM-bearing mice.

OAB-005: Update of safety and efficacy of Isatuximab short-duration fixed-volume infusion plus Bortezomib, Lenalidomide, and Dexamethasone combined therapy for NDMM ineligible/with no immediate intent for ASCT

<h3>Introduction</h3> One standard-of-care treatment for patients with newly diagnosed multiple myeloma (NDMM) not eligible for autologous stem cell transplant (ASCT) is the combination of bortezomib (V), lenalidomide (R), and dexamethasone (d). Isatuximab (Isa), a monoclonal antibody targeting a specific epitope of CD38, is approved in combination with pomalidomide/carfilzomib plus d for the treatment of adults with relapsed/refractory multiple myeloma. The objective of this study was to evaluate the efficacy and safety of the approved short-duration fixed-volume infusion of Isa, combined with VRd (Isa-VRd) in patients with NDMM ineligible/with no immediate intent for ASCT. <h3>Methods</h3> In Part A of this Phase 1b study (NCT02513186), a weight-based infusion of Isa-VRd was effective and well tolerated (median infusion duration at first infusion, 3.7 hours). Here, we present results from Part B, where Isa (10 mg/kg) was administered as a fixed-volume infusion of 250 mL with standard doses of VRd (Ocio Blood 2020). The primary endpoint is the complete response (CR) rate of Isa-VRd. <h3>Results</h3> Of 46 patients in Part B, 30 (65.2%) were receiving study treatment at data cutoff (March 17, 2021). Median patient age was 70.0 years (range, 49–87), and 8 (17.4%) had high-risk cytogenetics. There were 13 (28.3%) patients eligible, but with no immediate intent, for ASCT; of these, 7 (53.8%) proceeded to mobilization and 6 (46.2%) performed apheresis (median 8.1×10⁶ CD34+ cells/kg collected). The median duration of Isa infusion decreased to 1.3 hours from the third infusion onward. The overall response rate was 97.8%, including a CR/stringent CR (sCR) rate of 35.6% and very good partial response rate of 55.6%. After implementation of the SEBIA Hydrashift Isa immunofixation assay assessing serum M-protein without Isa interference, the adjusted CR/sCR rate increased to 53.3%. Investigation of minimal residual disease (MRD) negativity by combined next-generation flow cytometry or sequencing methods at a threshold of 10-5 revealed 23/45 (51.1%) of response-evaluable patients with MRD negativity. All patients experienced ≥1 treatment-emergent adverse event (TEAE), 32 (69.6%) had Grade ≥3 TEAEs, 20 (43.5%) had serious TEAEs, and 6 (13.0%) had TEAEs leading to death. Infusion reactions were observed in 13 (28.3%) of patients; none were of Grade ≥3. The most frequently reported TEAEs were constipation (69.6%), asthenia (67.4%), diarrhea (56.5%), and peripheral sensory neuropathy (50.0%). The most common Grade ≥3 hematologic abnormalities were lymphopenia (76.1%) and neutropenia (41.3%). <h3>Conclusions</h3> These results confirm the feasibility, efficacy, and safety of the approved short-duration fixed-volume infusion method of Isa in combination with VRd in patients with NDMM ineligible/with no immediate intent for ASCT. Isa-VRd is under investigation in ongoing Phase 3 studies. <h3>Funding</h3> Sanofi.

Prediction Model for Cereblon Expression in Bone Marrow Plasma Cells Based on Blood Markers in Multiple Myeloma Patients.

BackgroundCereblon (CRBN) is a direct target of immunomodulatory drugs (IMiDs) and is known to be sensitive and responsive to IMiD therapy. We evaluated CRBN expression in bone marrow plasma cells and analyzed whether CRBN expression was associated with multiple myeloma prognosis. Lastly, we developed a nomogram model for predicting high CRBN expression based on clinically significant blood markers.MethodsWe evaluated 143 multiple myeloma patients (internal dataset) who underwent bone marrow examinations. For evaluating the prognostic ability of the nomogram model, two external cohorts (235 patients in external dataset 1 and 156 patients in external dataset 2) were analyzed. The expression of CRBN in bone marrow aspirate samples was evaluated using immunohistochemistry. High CRBN expression was defined as the study-defined H-score ≥6.ResultsIn the high CRBN group, the median progression-free survival (PFS) and overall survival (OS) of patients receiving the IMiD-based therapy and non-IMiD therapy were 29 and 10 months for PFS, and NR (not reached) and 54 months for OS, respectively. IMiD-based therapy was significantly associated with better PFS and OS outcomes. High CRBN expression was independently predicted by female sex, high serum free-light chain (FLC) ratio, higher serum M-protein level, and higher β2-microglobulin level. Based on these results, we constructed a new nomogram model to predict high CRBN expression and the effectiveness of IMiD therapy in multiple myeloma.ConclusionThis nomogram could improve the prognostic evaluation of myeloma patients exhibiting high CRBN expression treated with IMiD therapy and might help provide personalized treatment strategies to clinicians.