Kastritis, Efstathios

Solitary plasmacytomas (SPs) are rare localized tumors of clonal plasma cells, either in the bone (solitary bone plasmacytoma) or in soft tissue/extraosseous (extramedullary) with either no or with minimal bone marrow (BM) infiltration (<10% clonal plasma cells by immunohistochemistry) and no evidence of systemic involvement or myeloma defining events. Approximately 50% of SPs will progress to symptomatic myeloma within 5 years after initial definitive local radiotherapy. Increased availability of improved diagnostic and monitoring tools has increased the sensitivity of detection of additional lesions and marrow involvement and has implications for the follow-up strategy after treatment. Thus, the definitions and requirements for the diagnosis and follow-up of SPs are evolving. The diagnosis of SP requires the careful exclusion of multiple myeloma (MM) that would require systemic therapy, by using all the available methods to detect systemic disease (advanced imaging, sensitive BM assessment methods, blood and urine tests). Local radiotherapy remains the mainstay of therapy, and despite the availability of innovative drugs for MM, the clinical benefit of systemic therapy currently remains poorly defined. The International Myeloma Working Group provides here updated recommendations for the diagnosis, evaluation, treatment, and response assessment of patients with SPs, incorporating recent data and advances in diagnostic tools.

PURPOSE In immunoglobulin light chain (AL) amyloidosis, amyloid fibrils cause organ dysfunction. Anselamimab, a monoclonal antibody, selectively binds to amyloid fibrils, accelerating their clearance. METHODS Newly diagnosed patients with European modification of Mayo 2004 stage IIIa or IIIb AL amyloidosis were randomly assigned to receive anselamimab or placebo with cyclophosphamide, bortezomib, and dexamethasone (with or without daratumumab). The primary end point was a hierarchical composite of time to all-cause mortality (ACM) and frequency of cardiovascular hospitalizations (CVHs), analyzed using the Finkelstein-Schoenfeld test and win ratio estimation. RESULTS Among 406 randomly assigned patients, the primary end point win ratio for anselamimab versus placebo was 1.11 (95% CI, 0.83, 1.50; P = .332) and the hazard ratio (HR) for ACM was 0.80 (95% CI, 0.57, 1.13; P = .290). CVH rates in the anselamimab and placebo groups were 0.59 (95% CI, 0.42, 0.83) and 0.89 (95% CI, 0.55, 1.43), respectively ( P = .145). Among patients with kappa isotype (n = 72), the win ratio was 2.06 (95% CI, 0.98, 4.31; P = .100) and anselamimab reduced ACM by 62% versus placebo (HR, 0.38; 95% CI, 0.17 to 0.86; nominal P = .012), and CVH by 71% (IRR, 0.29; 95% CI, 0.10 to 0.87; nominal P = .028) with improvements in Kansas City Cardiomyopathy Questionnaire-Overall Score. There was no clinical benefit observed in the lambda population. Anselamimab was generally well-tolerated; safety data were comparable between treatment arms overall. CONCLUSION Treatment with anselamimab, an antifibril antibody used alongside antiplasma cell dyscrasia therapy, while not meeting the primary end point in the overall population, significantly improved ACM and CVH in patients with kappa AL, potentially offering a new therapeutic option for this isotype.

Abstract The detection of genetic abnormalities is required during diagnostic workup and for potential individualization of therapy selection in multiple myeloma (MM) and its precursor conditions. At present, this relies on invasive bone marrow (BM) biopsies, severely limiting early detection, frequent longitudinal monitoring, and the precise selection of therapy. The current standard for detecting genetic alterations in MM is fluorescence in situ hybridization (FISH), which cannot detect point mutations and other clinically relevant alterations. Consequently, the IMS-IMWG guidelines were recently updated to require next-generation sequencing for the classification of high-risk MM. To address these needs, we recently launched GenoPredicta, a CLIA-approved LDT that enables routine monitoring, informing diagnosis, and treatment selection by comprehensively characterizing MM genomes with whole genome sequencing (WGS) from as few as 50 circulating tumor cells (CTCs) isolated from peripheral blood (PB) or tumor cells from BM. Briefly, tumor cells are isolated from samples using fluorescence-activated cell sorting and subjected to WGS, from which copy number alterations, structural variants, and short variants (SNVs/indels) are identified using a fully automated pipeline generating physician-ready clinical reports from raw sequencing data in ∼6h. Analytical validation of GenoPredicta showed complete concordance with FISH results. Identifying alterations in therapeutic targets (e.g., BCMA, GPRC5D) for guiding MM immunotherapies is becoming increasingly important. Here, we describe GenoPredicta results from relapsed/refractory MM patients, highlighting resistance-conferring alterations that can only be detected by WGS, such as deletions in the kilo- to megabase scales that are observed in conjunction with SNVs and indels, leading to biallelic loss/inactivation of the gene, including at subclonal levels. In addition to biallelic loss of BCMA and GPRC5D in response to CAR T or T cell engager therapies, we observed similar resistance mechanisms for targets of immunomodulatory drugs, e.g., CRBN. The observation of these resistance mechanisms was consistent with patients’ clinical histories. In summary, we demonstrate that low input WGS-based characterization of MM from BM or CTCs is a viable replacement for FISH for clinical diagnosis and monitoring, with CTC-based measurements enabling comprehensive profiling of the MM genome. Crucially, this includes genetic alterations that confer resistance to therapy, allowing for both early detection of such alterations and more precise selection and guidance of therapy. The dramatically improved variant calling ability from WGS, especially in low-input CTC applications, extends to other malignancies and will gain wider adoption as sequencing costs continue to decrease. Citation Format: Bruno Paiva, Peter Voorhees, Patricia T. Greipp, Danielle Sookiasian, Julian Hess, Marisa DeMeo, Vicki Pounder, Sarah Calkins, Reid Meyer, Linda B. Baughn, Christine-Ivy Liacos, Meletios-Athanasios Dimopoulos, Alexandra Papadimou, Taouxi Konstantina, Efstathios Kastritis, Jesus Berdeja, Daniel Auclair, Valentina Nardi, Thomas Mullen, Francois Aguet, Shaji Kunnathu Kumar. Whole genome sequencing of multiple myeloma genomes with a novel clinical assay enables identification of genetic alterations underlying immunotherapy resistance [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 1067.

ABSTRACT Systemic AL amyloidosis is a clonal plasma cell dyscrasia, where toxic free light chains (FLCs) lead to vital organ damage, with risk of early mortality despite effective therapies. Notably, there is a paucity of data on the incidence and predictors of early mortality in the daratumumab (Dara) era. We conducted a multi‐center retrospective cohort study to develop and validate a risk‐prediction model for early mortality (all‐cause death within 6 months) in patients treated with Dara‐based frontline regimens. We used univariate analysis to identify covariates for a logistic regression model predictive of 6‐month mortality and generated a clinical risk score. Among 339 patients across eight centers, 36 (10.6%) experienced early mortality. Multivariate analysis identified four independent predictors: NT‐proBN P > 5300 pg/mL (odds ratio [OR] 3.83, p = 0.006), A ge > 75 years (OR 2.96, p = 0.073), absence of t(11;14) on C ytogenetics (OR 3.0, p = 0.022), and E COG performance status (OR 1.72 per unit increase, p = 0.044). The resulting PACE score stratified patients into three risk groups with a 6‐month mortality of 1.2% (low‐risk), 11.7% (intermediate‐risk), and 50.0% (high‐risk). The PACE score demonstrated superior discrimination (C‐index 0.78) for early mortality compared to Mayo 2004 (0.69) and Mayo 2012 (0.55) staging systems. External validation confirmed robust discrimination (C‐index 0.73) with corresponding 6‐month mortality rates of 4.2%, 15.25%, and 37.04% across respective risk groups. The PACE score provides a clinically applicable tool for early mortality risk stratification in AL amyloidosis patients receiving Dara‐based therapy, and will enable improved patient counseling, clinical trial design, and identification of ultra‐high‐risk patients requiring intensive monitoring and novel therapies.

Abstract Recent therapeutic advances, including bispecific antibodies (bsAbs), have improved outcomes for patients with relapsed/refractory multiple myeloma (RRMM). However, early mortality (EM) remains a significant challenge, even in the era of novel immunotherapies. We conducted a multicenter, retrospective analysis of real-world patients with RRMM treated with commercial bsAbs to evaluate the incidence and causes of EM. Between May 2022 and June 2025, a total of 441 patients were treated across 7 countries. EM, defined as death within 12 months of therapy initiation, occurred in 148 patients (34%), with a median time from bsAb initiation to death of 2.87 months (interquartile range, 1.38-6.85). The leading cause of EM was progressive disease (72%), followed by infection (13%); regardless of the cause of death, 82% had active disease at the time of death. Our findings highlight that despite encouraging efficacy, EM remains high among real-world bsAb recipients, emphasizing the need for improved disease control strategies and supportive care interventions.

Abstract Waldenström macroglobulinemia (WM) is characterized by recurrent MYD88 and CXCR4 mutations, whose prognostic value in patients treated with chemoimmunotherapy remains unclear. Moreover, the typically prolonged progression-free survival (PFS) correlates inconsistently with overall survival (OS), underscoring the importance of examining other surrogates. Progression of disease within 24 months (POD24), an established early end point, delineates functionally high-risk patients in other indolent lymphomas. This international study evaluated 253 patients receiving frontline fixed-duration bendamustine-rituximab (BR), a common chemoimmunotherapy for WM. At a median follow-up of 5.9 years, 5-year PFS and OS were 65% and 87%, respectively; 5-year PFS was similar between MYD88L265P (90%) and MYD88wild-type (WT) subcohorts (64% each; P = .4). Among 89 patients with known CXCR4 status, the subcohort with CXCR4mutation (28%) had shorter PFS (median 3.3 vs 8.8 years; hazard ratio [HR], 2.8; P = .0036) and OS (HR, 2.6; P = .036) compared with CXCR4WT. POD24 occurred in 11.5% of patients who demonstrated inferior subsequent OS (5-year OS, 71% vs 86%; HR, 3.1; P = .005) and higher mortality (standardized mortality ratio [SMR], 3.7), unlike the non-POD24 group, whose mortality was comparable to the matched general population (SMR, 1.1). In conclusion, BR is effective irrespective of the MYD88 status, but CXCR4 mutations and POD24 portend worse outcomes. Patients without POD24 represent a cohort with distinctly favorable outcome.

PURPOSE Outcomes in systemic light chain (AL) amyloidosis have improved with modern therapy limiting utility of existing risk stratification models. We validate a new staging system, incorporating longitudinal strain (LS) to the biomarker-based (NT-proBNP and Troponin-T) staging system in the contemporary treatment era (2015-2024). METHODS AL International Staging System (AL-ISS) was derived from a cohort of patients with AL amyloidosis from the UK National Amyloidosis Centre (2015-2019). The model was validated in patient cohorts from Europe (Greece, Italy, the Netherlands, and Switzerland), the United States (2015-2024), and the United Kingdom (2020-2024). RESULTS In total, 2,493 patients were included (derivation, n = 573; validation n = 1,920). In a multivariable model for the derivation cohort, LS ≥ –9% and cardiac biomarkers at previously validated thresholds (NT-proBNP 332 ng/L and 8,500 ng/L and high-sensitivity troponin T ≥ 50 ng/L) were independent poor prognostic factors stratifying patients into stages I, II, IIIA, IIIB, and IIIC. In the validation cohort, the patient stages were stage I: 317 (17%), II: 782 (41%), IIIA: 551 (29%), IIIB: 174 (9%), and IIIC: 96 (5%), respectively (first-line daratumumab treated: 826; 43%). With a median follow-up of 34 months, median overall survival (OS) was not reached (NR); estimated 1-year, 2-year, and 3-year OS was 82%, 74%, and 70% respectively. The median survival for stages I to II, IIIA, IIIB, and IIIC were NR, 67, 26, and 7 months (1-year OS IIIC 53% v 68% for IIIB in the daratumumab-treated patients), respectively ( P < .001). External validation exhibited good predictive performance: 12-month calibration slope was 1.09, Harrell C 0.69, Royston D 1.19, and R 2 D 0.25. Stage IIIC independently discriminated the poorest outcome across all cohorts. CONCLUSION This defines and validates a new staging system from systemic AL amyloidosis with robust identification of an ultra-poor risk stage (IIIC) in contemporarily treated patients.

Abstract Introduction: Elranatamab (Elra) is a bispecific antibody (BsAb) targeting BCMA that is approved for patients with triple class exposed relapsed refractory myeloma (RRMM) on the basis of the MagnetisMM-3 phase 2 trial. For BCMA naïve patients, an overall response rate (ORR) of 61.0% and median progression free survival (PFS) of 17.2m was observed with a median overall survival (OS) of 24.6m. However, efficacy and safety information in the real world is lacking. Methods: This was an international retrospective study of patients with RRMM treated with Elra monotherapy outside of clinical trials. Data was collected through the International Myeloma Foundation Immunotherapy Database from 7 countries (UK, USA, Canada, Greece, Spain, Czech Republic and Singapore). High-risk cytogenetic abnormalities (HRCA) were defined as 1q+, t(4;14), t(14;16), t(14;20), and/or del(17p). Response was assessed using IMWG consensus criteria. Patient characteristics were summarized by frequency (percentage) or median (range). PFS, OS were evaluated using the Kaplan-Meier method and reported with 95% confidence intervals. Results: 79 patients were included. Median age was 67 years (range: 41-95y) with 20% ≥75 years. Racial distribution was: 75% White, 16% Black/African American, 8% Asian/Pacific. 55% were ECOG performance status (PS) 1-2. Patients received a median of 5 prior lines (range 1-11), and 35% were BCMA exposed (9% CAR-T, 5% ADC, 7% BsAb, 8% BsAb plus CAR-T, 4% ADC plus BsAb). Of those with available data, 45% had HRCA,13% had extramedullary disease (EMD) and 32% had penta-drug refractory RRMM. Overall, 48% would not have been eligible for the MagnetisMM-3 trial. Median follow-up was 6.3m (range 0.5-35.0). ORR was 53% (PR 11%, VGPR 33%, CR 8%, sCR 1%) and 67% for BCMA naïve patients. Responses were significantly lower for BCMA exposed patients (ORR 31%) but did not differ by age (51% &lt;75yrs vs 60% ≥75yrs). On univariate analysis, prior BCMA exposure, platelets &lt;50, presence of HRCA and penta-refractoriness were significantly associated with a lower response rate. PFS for the whole cohort at 6 and 12m was 64% (95%CI, 54-77%) and 52% (40-67%); for BCMA naïve patients, it was 77% (65-90%) and 67% (54-84%), respectively. Within the whole cohort, PFS was shorter for: BCMA exposed (median 4.0m vs not reached (NR)), platelets &lt;50 (2.0 vs 21.7m), HRCA (7.2m vs NR), penta-refractory (4.3m vs NR). PFS did not differ significantly by EMD, PS, age, or creatinine clearance. OS for the whole cohort at 6 and12m was 74% (64-85%) and 58% (45-74%); for BCMA-naïve patients, it was 80% (43-85%) and 70% (57-87%), respectively. Within the whole cohort, OS was shorter for: BCMA exposed (median 10.3m vs NR), platelets &lt;50 (4.3m vs NR), HRCA (10.7m vs NR) and penta-refractory (10.3m vs NR). Univariate regression analysis demonstrated that prior BCMA exposure, platelets &lt;50 and penta-refractoriness were significantly associated with a worse PFS and OS, and HRCA predicted poorer survival CRS was observed in 41% of patients (grade(G)1: 35%, G2: 5%, ≥G3: 0%) with most occurring with the first step up dose (SUD): SUD1: 29%, SUD2: 15%, full dose: 4%. Tocilizumab was used in 20% and steroids in 3%. ICANS was observed in 4 cases (5%): G1: 2, G2: 1, G4: 1. Treatment was with steroids (n=3) and tocilizumab (n=2). G3-4 thrombocytopenia was observed in 19% and 14% required platelet transfusions. G3-4 neutropenia occurred in 25% with overall 31% requiring GCSF. Infections were reported in 33 (42%) patients with median time to infection of 41 days. A total of 94 infection episodes were observed over 581 personal months. There were 2 infection-related deaths reported (1 had IVIG, 1 did not). 64% had hypogammaglobulinemia (IgG &lt; 400mg/dl) and IVIG was given in 65% of patients. Conclusions: In this first international real world analysis, Elranatamab achieved a response rate of 67% and a 12m PFS of 67% in BCMA naïve patients, similar to the MagnetisMM-3 trial despite almost half not meeting trial eligibility. However, prior BCMA exposure, platelets &lt;50, high risk cytogenetics and penta refractory status were predictors of poorer outcomes. Acknowledgements: The International Myeloma Foundation, International Myeloma Working Group (IMWG)

Abstract Introduction AL amyloidosis is a rare disorder caused by amyloid fibrils produced by clonal plasma cells, leading to serious organ dysfunction. Cardiac involvement is a major risk factor for poor survival. CD38-binding Daratumumab (D) targets plasma cells and, with bortezomib, cyclophosphamide and dexamethasone (VCd) is the only approved regimen for newly diagnosed AL amyloidosis. The ANDROMEDA phase 3 study showed significant improvements in hematologic responses, major organ deterioration progression free survival and overall survival, compared with VCd alone. The AQUARIUS study (NCT05250973) evaluated cardiac safety of different D-VCd schedules and potential cardiac toxicity mitigation strategies. Methods This multicenter, open-label, phase 2 study enrolled 151 newly diagnosed AL amyloidosis patients at 37 sites in 10 countries. Patients enrolled in either Cohort 1 (n=120, cardiac involvement [Mayo 2004 stage II/IIIA], randomized 2:1 to receive D + immediate VCd or D + deferred VCd) or Cohort 2 (n=31, racial or ethnic minorities with ≥1 any organ involvement, treated with D + immediate VCd). Immediate VCd began on Cycle 1, deferred VCd on Cycle 4. The primary safety endpoint was the incidence of cardiac treatment emergent adverse events (TEAEs). Cardiac assessments included HS TroponinT, NT-proBNP, echocardiogram (ECHO), ECG, NYHA, and the 6-minute walk test (6MWT). Clinical cardiac signs and symptoms (S&S) were assessed at baseline and monthly. Selected, clinically relevant grade ≥3 and/or serious cardiac TEAEs were defined as Major Cardiac TEAE and were assessed by an independent adjudication committee for causality. Patients were followed for 12 treatment cycles or 12 months from first dose (if treatment discontinued prior to 12 cycles). Results 142 patients from both cohorts had cardiac involvement and received at least one dose of D + immediate VCd (n=103) or D + deferred VCd (n=39). Baseline characteristics were balanced between the two groups, including Mayo 2004 stage (IIIa: immediate VCd, 35.0%; deferred VCd, 35.9%; II: immediate VCd, 62.1%; deferred VCd, 53.8%). Treatment duration (median: 10.4 months) and proportion completing ≥10 cycles (79% vs 85%) were similar. Serious cardiac TEAEs occurred at similar rates across groups (immediate VCd, 7.8%; deferred VCd, 7.7%). The most common serious cardiac TEAE (MedDRA term) was cardiac failure (immediate VCd, 5.8%; deferred VCd, 2.6%). Two deaths occurred within 60 days of first study treatment, both were in the immediate VCd group, cardiac-related and unrelated to treatment. The immediate VCd group had fewer cardiac TEAEs overall (48.5% vs 61.5%) but experienced them more frequently during Cycles 1-3 than deferred VCd (35.9% vs 28.2%). This trend reversed for Cycles 4-6 (immediate VCd, 17.7%; deferred VCd, 28.9%). Cardiac TEAEs were low for both groups for Cycles 7-9 (immediate VCd, 9.3%; deferred VCd, 12.1%) and Cycles 10-12 (immediate VCd, 7.4%; deferred VCd, 12.1%). Levels of NT-proBNP, HS troponin T, the 6MWT, and overall cardiac S&S improved similarly for both treatment groups. Rate of cardiac TEAEs of any grade was similar for Mayo stage III patients in the two groups (immediate VCd, 73.0%; deferred VCd, 68.8%) whereas for Mayo stage II patients the incidence was higher in the deferred group (35.9% vs 57.1%). Twenty patients (Immediate VCd, 13; deferred VCd, 7) experienced 30 Major Cardiac TEAEs (selected grade ≥3 and/or serious). Adjudicators attributed 28 events primarily to amyloid cardiomyopathy and 2 events primarily to treatment. These 20 patients had higher baseline Mayo stage (IIIa: 70% vs 29.5%) than the remaining patients (n=122), higher baseline median NT-proBNP (4862 ng/L vs 1723 ng/L) and overall S&S score (7.5 vs 4.0). Several ECHO measures were worse at baseline in these 20 patients (notably, median GLS: -8.8% vs -13.7% and E prime lateral: 4.4 cm/s vs 6.1 cm/s) as was 6MWT (median distance: 319 m vs 363 m). Complete Response (CR) rates were similar in both groups: immediate VCd, 62.1%; deferred VCd, 59.0%. Median time to CR was 64 days for the immediate VCd group and 113 days for the deferred VCd group. Conclusion The D-VCd regimen (immediate or deferred) had a manageable safety profile consistent with previous studies. Cardiac TEAEs were similar between regimens, and their emergence correlated with the start of VCd. Major cardiac events were associated with underlying disease and baseline risk factors that are quantifiable and monitorable.

Abstract Background B-cell maturation antigen (BCMA)-targeting immunotherapies represent a promising class of treatment for the management of immunoglobulin light chain (AL) amyloidosis, a disease that is related to clonal plasma cells. Etentamig is a 2nd generation, off-the-shelf, fully human BMCA X CD3 bispecific antibody with bivalent BCMA domain and low CD3 affinity that targets both BCMA-expressing plasma cells and CD3-expressing T cells. Etentamig monotherapy is being studied in multiple myeloma (MM) in an ongoing phase 3 study (NCT06158841). Here, we report the first safety and efficacy results from M24-209, an open-label phase 1/2 study evaluating etentamig monotherapy in patients (pts) with relapsed/refractory (RR) AL amyloidosis from dose level 1 (DL1). Methods The phase 1 dose escalation (ESC) portion of the study (NCT06158854) with etentamig enrolled pts with RR AL amyloidosis with ≥1 prior lines of therapy (LOT), including a proteasome inhibitor and an anti-CD38 monoclonal antibody with no prior BCMA exposure. Eligible pts were required to have a difference in involved and uninvolved serum free light chain (dFLC) of ≥50 mg/L, and pts with Mayo Clinic 2004 cardiac risk stage IIIb with NT-proBNP ≥8500 pg/ml were excluded. Three dose groups were explored in dose ESC (etentamig dose levels [DL] 1, 2, and 3). In all cohorts, pts will receive up to 24 cycles of treatment and will be followed until disease progression. In dose ESC, the primary objectives are to determine safety/tolerability, pharmacokinetic/pharmacodynamic, and recommended phase 2 dose. The secondary objectives include evaluation of efficacy as measured by hematologic response and organ response. Responses are investigator assessed per consensus guidelines (Comenzo, et al. Leukemia. 2012. 26[11]:2317-25; Palladini G, et al. Amyloid. 2021 [Epub];28[1]:1-2). Results As of 17 July 2025, all DLs in dose ESC have been fully enrolled, and 12 pts have been treated with etentamig at DL1. Due to short follow-up, this initial report only includes data from DL1, with further follow-up data from ESC to be included at the time of presentation. Median duration of follow up in DL1 was 9.4 months (8.3–13.8) with 83% of pts continuing treatment. Median age for pts was 72 years (range, 56–85 years). Median number of prior LOT was 2 (range, 1–6), and median time from initial diagnosis was 3.6 years. Thirty-three percent have received a prior stem cell transplant and 50% previously received the regimen of daratumumab with cyclophosphamide, bortezomib, and dexamethasone in combination. Median dFLC at study baseline was 110. 5 mg/L (range, 56.6–617.5). At baseline, 83% of pts had cardiac involvement, 25% had renal involvement, and 8% had hepatic involvement. Eighty-three percent of pts had lambda AL amyloidosis. Treatment-emergent adverse events were reported in 100% (42% Grade ≥3) of pts at DL1. Cytokine release syndrome (CRS) occurred in 2 pts (17%, all Grade 1), with no instances of any grade immune effector cell-associated neurotoxicity syndrome (ICANS). CRS occurring after the first dose had median time to onset of 6.8 hours (range, 6.7–6.9). Grade ≥3 infections occurred in 1 pt (8%, all Grade 3). Grade ≥3 neutropenia also occurred in 1 pt (8%, all Grade 3), and no Grade ≥3 events of thrombocytopenia or anemia occurred. No Grade 5 events have occurred. Within the dose ESC DL1 cohort, the overall hematologic response rate was 100%, with all pts achieving ≥VGPR and 83% of pts achieving complete response (CR). The median time to CR was 0.9 months (0.3–9.3). The median duration of response has not yet been reached and 100% of pts remain in their best overall response by investigator assessment. To date, no pts have experienced hematologic progression on study. Cardiac response was observed in 30% of evaluable pts. Renal response was seen in 67% of evaluable pts. Conclusions In the DL1 cohort, etentamig showed a manageable safety profile in AL amyloidosis with low incidence and severity of CRS, no ICANS, and limited Grade ≥3 cytopenia events. Deep and rapid hematologic responses were observed with 100% ≥VGPR rate and 83% hematologic CR rate. Additional dose-level data will be presented at the time of the meeting. All pts remain in ongoing follow-up and evaluation, and the study will begin the dose expansion (EXP) portion after dose selection.