Citations

e19531 Background: Effective treatment and elimination of clonal plasma cells (PC) in multiple myeloma (MM) are typically associated with recovery of polyclonal (normal) plasma cells (PPC). Studies suggest that robust PPC recovery is associated with better outcomes. However, it is unclear if this remains valid in the context of monoclonal antibodies, such as Daratumumab, that selectively target plasma cells, and in turn, may adversely impact PPC recovery. Methods: We identified patients with MM who underwent MRD testing using Euroflow method at 6-12 months after treatment initiation. Eight patients had disease progression prior to MRD testing and were excluded from further analysis. PPC was quantitated by the proportion of total events acquired during flow examination. Patients were considered MRD-negative if they had <1 clonal PCs in 10 5 cells, as detected in the marrow. We first examined the impact of initial therapy (Daratumumab vs. non-Daratumumab based regimens) and MRD status on PPC recovery. Subsequently, we analyzed impact of PPC recovery on patient outcomes in terms of progression-free survival (PFS) and overall survival (OS). Results: We identified 572 patients who had MRD testing by flow at a median of 9 months (range 6-12) after treatment initiation. The median age was 63 years, 58% were male. Daratumumab was part of initial therapy in 17% of patients; the most common induction therapies were PI-IMiD triplets (73%), and dara-PI-IMiD quads (15%). In our cohort, 74% of patients were MRD-negative. In our practice, only samples with no monotypic PCs identified on initial low-sensitivity flow proceed to MRD testing, hence, the proportion of MRD-negative patients appears higher in our study than previously reported. Median PPC was 0.02% and was similar between MRD-negative and -positive patients. We found the median PPC was significantly low in patients who received Daratumumab compared to the non-Daratumumab treated cohort (0.011% vs. 0.023%; p<0.01). There was a trend towards lower PFS and OS among the lowest PPC quartile group compared to the upper 3 quartiles, although this was not significant (p=0.07 for PFS and OS, Wilcoxon). This trend was more evident among patients who did not receive Daratumumab. Conclusions: Our study demonstrates negative impact of anti-CD38 therapy with Daratumumab on recovery of PPCs after initial treatment, consistent with the persistent hypogammaglobulinemia seen in clinical practice among these patients. However, unlike the observation with the non-Daratumumab treated cohort, the low proportion of PPCs does not significantly impact patient outcomes among patients who received Daratumumab.

e19545 Background: Cytogenetic abnormalities (CA) at diagnosis are important prognostic factors in multiple myeloma (MM), but there is limited information on how these abnormalities evolve at first relapse and their significance. Methods: This retrospective study included patients aged ≥18 years, with a confirmed diagnosis of MM who experienced at least one disease relapse and had fluorescence in situ hybridization analysis within six months of both diagnosis and relapse. Data on CA and clinical outcomes were collected. High-risk (HR) secondary CA were defined as the presence of deletion of chromosome 17p (del17p) or gain or amplification of chromosome 1q. The primary objective was to evaluate changes in HR secondary CA at first relapse, while the secondary objective was to assess the impact of the cytogenetic changes on overall survival (OS) from diagnosis. Based on the presence or absence of HR secondary CA, patients who were tested for HR secondary CA at both time points were classified into four groups: 1) persistent absence of HR secondary CA, 2) emergence of HR secondary CA at relapse, 3) persistent presence of HR secondary CA, and 4) loss of HR secondary CA at relapse. Results: A total of 233 patients diagnosed between 2004 and 2023 were included. HR secondary CA were tested in 98.7% (n= 230) of patients at diagnosis, with 24.8% (n=57) testing positive. At first relapse, testing for HR secondary CA was performed in 97.4% (n=227) of patients, of whom 23.8% (n=54) tested positive. Del17p was evaluated in 98.3% (n=229) of patients at baseline and 95.7% (n=223) at relapse, with positivity increasing from 10.9% (n=25) to 15.3% (n=34). Gain or amplification of chromosome 1q was evaluated in 49.4% (n=115) at baseline and 25.5% (n=60) at relapse, with positivity rate rising from 28.7% (n=33) to 38.3% (n=23). There were no differences in overall response rate or very-good-partial-response-or-better rates to the initial therapy at diagnosis between the groups. (Table) Emergence/persistence of HR CA were associated with lower OS from diagnosis. Conclusions: Emergence of HR secondary CA at first relapse in MM has prognostic significance. These findings highlight the importance of serial cytogenetic testing for risk stratification. Response rate to initial line of therapy and overall survival from diagnosis among patients tested for HR secondary CA both at diagnosis and first relapse (n=224). Outcome Persistent absence of HR secondary CA(n=142) Emergence of HR secondary CA at relapse (n=25) Persistent presence of HR secondary CA (n=27) Loss of HR secondary CA at relapse(n=30) p-value Overall response rate a 75% (106) 76% (19) 63% (17) 67% (20) 0.5 b Very-good-partial response or better response rate 43% (61) 36% (9) 44% (12) 40% (12) >0.9 b Median (95% CI) OS from diagnosis in years 11.3 (9.7-13.4) 7.5 (5.1-12.1) 6.1 (4.2-9.4) 10.1 (6.5-14.1) <0.0001 c a Partial response or better; b Chi-square test; c Log-rank test.

e19503 Background: The uptake of BCMA directed ADCs in MM has been hindered by ocular toxicity. Belantamab mafodotin (BM) and MEDI2228 (MEDI) are BCMA directed monoclonal antibodies conjugated to the microtubule inhibitor, monomethyl auristatin F and the alkylator, pyrrolobenzodiazepine, respectively. Differences in the ADCs payload, antibody specificity and linker stability influence ocular toxicity. We investigated the patterns of ocular toxicity and tolerability of BCMA directed ADC therapy. Methods: Retrospective study of MM patients who commenced treatment with a commercial or investigational BCMA directed ADC at the Mayo Clinic between 2019-22. Results: 111 patients were included, the median age was 69 and median follow up 40 months. The median number of prior treatments was 6, 87% of patients were triple class refractory, 50% penta class refractory, 14% had prior BCMA directed therapy and 24% had extraosseous disease. Treatments included BM (n=56, 50%), BM in combination with other MM therapy (n=12, 11%) and MEDI (n=43, 39%). The overall response rate was 30% for BM and 44% for MEDI. The median OS and PFS for BM was 8 and 2 months, the median OS and PFS for MEDI was 11 and 5 months. The median number of ADC cycles was 2.5. Ocular toxicity is summarized in the table 1. Keratopathy was more common with BM (p=0.004). Only 4 MEDI patients developed keratopathy, all grade 1 and associated with dry eyes and/or photophobia. In contrast, 60% of BM patients developed keratopathy (13% grade 3-4 keratopathy). The median time to keratopathy onset was 1 month with BM, and 2.8 with MEDI. The median time until keratopathy was 4.6 months for BM. Loss of best-corrected visual acuity (VA) was significantly more common with BM (p<0.001). The median time to any decline in VA was 1.5 months for BM and 2.3 for MEDI. The median time until VA returned to baseline was 2.4 months for BM and 2.3 for MEDI. The frequency of dose delays for ocular toxicity was comparable between ADCs, as was the number of dose reductions (16% BM vs. 12% MEDI, p=0.5). The most common reasons for treatment discontinuation were progression or death (BM=69%, MEDI=44%) and ocular toxicity (BM=18%, MEDI=30%). Conclusions: Treatment interruptions, dose reductions and drug discontinuation are common with BCMA directed ADC therapy. Further research to optimize the administration schedule of these agents is warranted. BM and MEDI produce distinct patterns of ocular side effects, namely keratopathy and reduced VA with the former, and photophobia and dry eyes with the latter. BM N = 68 MEDI N = 43 p-value 2 Prophylactic steroid eye drops 4 (6%) 28 (68%) <0.001 Prophylactic lubricant eye drops 42 (63%) 33 (80%) 0.051 Max grade keratopathy 0.004 1-2 29 (47%) 4 (19%) 3-4 8 (13%) 0 (0%) VA equal or worse than 20/40 26 (68%) 6 (20%) <0.001 Days of ADC treatment 59 (33, 167) 68 (41, 105) 0.9 Dose delay for ocular toxicity 19 (28%) 8 (19%) 0.2 n (%); Median (IQR); 2 Chisq test; Wilcoxon rank sum.

e13622 Background: Chimeric antigen receptor T-cell (CAR-T) therapy has revolutionized treatment of hematologic malignancies; however, severe toxicities like cytokine release syndrome (CRS) remain a limitation to broader utilization. Using a large dataset of patients treated with CAR-T, we developed a machine learning (ML) model leveraging multi-model patient characteristics to predict the risk of CRS onset with clinically meaningful lead times. Methods: A prospectively maintained dataset of CAR-T patients treated at Mayo Clinic was used. Baseline disease/patients characteristics, labs, ECG, echocardiogram, and vital signs (including data from remote patient monitoring program) were collected. A 24-hour rolling window was used to generate daily averages, maximum, minimum, and deltas for each parameter. ECG and echocardiogram data were forward-imputed; vital signs and labs were not imputed. Each day-post-infusion served as a potential event (CRS onset vs. no CRS). A gradient boosting classifier was trained and tested on a subset of patients (n = 351) using 1,000 bootstrap iterations, evaluating 24-, 48-, and 72-hour lead times. Shapley-based feature importance guided simplification to an 11-feature model, externally validated on an independent cohort (n = 51). Models’ performance assessed using the area under the receiver operating characteristic curve (AUC). Results: A total of 402 patients treated with CAR-T were examined. Median age was 64 years and 36% were female. Primary diagnosis was B-cell lymphoma (n = 240) or multiple myeloma (n = 162). A total of 226,332 vital sign measurements and 372,871 lab values, as well as ECG and echocardiogram data, were collected for 30 days post-infusion. Overall, 79.8% of patients experienced CRS within 30 days. The full ML model demonstrated AUCs of 0.90 (95% CI 0.86–0.93), 0.83 (95% CI 0.77–0.88), and 0.82 (95% CI 0.77–0.87) for 24-, 48-, and 72-hour predictions of CRS, respectively. Including “day of CRS onset post CAR-T” as a feature improved the 72-hour AUC to 0.87 (95% CI 0.83–0.90). A model restricted to vital signs alone showed AUCs of 0.88, 0.75, and 0.71 for 24-, 48-, and 72-hour horizons. An 11-feature model—focusing on temperature, blood pressure, fibrinogen, CRP, serum sodium level, QRS interval, and lymphocyte counts—maintained high accuracy at 24 hours (AUC 0.90, 95% CI 0.86–0.93) and was validated externally using an independent dataset with an AUC of 0.92. Conclusions: Our ML model provides a reliable approach for predicting if/when CRS will occur, with up to three days of lead time before clinical manifestation, offering an opportunity for proactive management. The robust performance of a parsimonious 11-feature model supports practical adoption across clinical settings and real-time risk stratification to enhance patient safety. Prospective validation and integration into clinical workflows will be critical to translating these findings into practice.

7541 Background: Multiple myeloma (MM) is characterized by recurrent cytogenetic abnormalities, including translocations involving the immunoglobulin heavy chain locus on chromosome 14 and trisomies, which are considered primary and clonal. Throughout disease progression, MM cells may acquire additional abnormalities, which include chromosome 1 abnormalities (gain or amplification of 1q or deletion of 1p) and chromosome 17 abnormalities (del 17p or monosomy 17p). All these factors are considered high-risk markers that predict below-average outcomes. While outcomes related to 1q have been documented, their relationship with other abnormalities and clinical characteristics is less clearly defined. Methods: We created a cohort of newly diagnosed MM (NDMM) patients from April 1996 to December 2023 for whom FISH testing was performed using a panel that included 1q findings. Data on clinical and laboratory characteristics, other FISH abnormalities, and survival outcomes were collected from existing databases and the electronic medical record (EMR). Results: The cohort included 875 patients, with a median age of 65. Of these patients, 60% were male and 91% identified as white. A 1q abnormality was observed in 443 patients (51%); 87% exhibited a gain of 1q, while 13% showed amplification of 1q. Among those tested, other abnormalities included del13 (58%), t(11;14) (25%), t(4;14) (17%), t(14;16) (6%), del 17p (13%), and trisomies (51%). The distribution of abnormalities concerning the presence of 1q is presented in the table. Patients with 1q abnormalities were more likely to present with additional high-risk cytogenetic abnormalities. The median overall survival (OS) for those with a 1q abnormality was 73 months, compared to 105 months for those without it. Among these, patients with 1q amplification tended to have worse outcomes than those with a 1q gain, though this observation did not reach statistical significance. Conclusions: Abnormalities of chromosome 1, including 1q gain and amplification, can be seen in nearly 50% of patients with NDMM who are tested. 1q abnormalities are associated with other high-risk cytogenetic abnormalities. Measures of disease burden are higher among those with a 1q abnormality. Interestingly, we observed a higher proportion of patients with lambda light chain and those with IgA among those with a 1q abnormality. The presence of a 1q abnormality was associated with inferior survival, with a trend towards worse outcomes among those with 1q amplification compared to 1q gain. Clinical characteristics and cytogenetic associations of multiple myeloma patients with and without 1q abnormalities. 1q abnormality present 1q abnormality absent P del13 78% 39% <0.01 t(4;14) 25% 8% <0.01 t(11;14) 22% 27% NS t(14;16) 15% 3% <0.01 Trisomies 48% 53% NS 17p del 24% 12% <0.01 Lambda light chain 45% 26% <0.01 IgA 32% 16% <0.01 Hemoglobin 10.3 g/dL 11.2 g/dL <0.01

7540 Background: The combination of a proteasome inhibitor (PI) with lenalidomide (R) and dex (d) has been a common initial therapy for newly diagnosed myeloma (NDMM). We designed a randomized phase 3 trial to examine if carfilzomib (K), a next generation PI, improved progression free survival (PFS) compared with bortezomib (V) when either is combined with Rd for initial treatment of NDMM. Initial analysis at a median follow up of 15.3 months (mos) showed comparable PFS for both triplets. We present the long-term results of the trial with ~70 months median follow up. Methods: Patients (Pts) with NDMM, were randomized 1:1 to receive VRd or KRd for 36 weeks followed by a 2 nd randomization (1:1) to indefinite versus 2 yrs of R maintenance. Pts without del17p, t(14;16), t(14;20), plasma cell leukemia or high-risk GEP70 profile, were enrolled. VRd arm included V 1.3 mg/m 2 on days(d) 1, 4, 8, and 11 (d1, 8 for cycles 9-12), R 25 mg d1-14, and d 20 mg d1, 2, 4, 5, 8, 9, 11, 12 of a 3-week (wk) cycle for 12 cycles, while pts in the KRd arm received K 36 mg/m 2 d1, 2, 8, 9, 15, 16 with R 25 mg daily on d1-21 and d 40 mg wkly, in 4 wk cycles for 9 cycles. Maintenance used 15 mg R d1-21 q4 wks. Results: The study accrued 1087 pts (VRd=542, KRd=545). Median age was 65y; baseline characteristics including intent to transplant were similar across the arms. Median induction duration (mos; IQR) was 7.2 (3.4-8.9) and 8.4 (5.1-9.1) for VRd and KRd, respectively; 59.8% in VRd and 45.3% in KRd did not proceed to Step 2. Median PFS (mos) was VRd=41.9 and KRd=44.6; HR = 0.89 (0.76-1.04). Toxicity data, PFS sensitivity analyses and OS probabilities are as in the table. Conclusions: In this randomized trial, with median follow up of nearly 6 years, KRd and VRd had comparable PFS and OS in an intent to treat analysis. While similar numbers proceeded to SCT in the 2 arms, more did so during induction in the VRd arm while more patients in the KRd arm went to SCT later. VRd remains a standard triplet induction regimen in standard and intermediate risk NDMM, and a suitable backbone for 4 drug combinations. Clinical trial information: NCT01863550 . N (%) VRd(n=527) KRd(n=526) SCT anytime 186 (34.3) 183 (33.6) SCT without Step 2 registration 146 112 Median Time to SCT (mos; range) 7.7 (3.5-83.9) 10.6 (3.7-70.6) Grade 3-4 Treatment-Related Toxicity 315 (59.8) 344 (65.4) Grade 5 Treatment-Related Toxicity 2 (0.4) 9 (1.7) Grade 5 All Events 11 (2.1) 20 (3.8) Survival outcomes HR Median (95% CI) Median (95% CI) PFS Primary: PD or death within 3 months of last evaluation as events 0.89(0.76-1.04) 41.9(35.7, 50.3) 44.6(38.2, 51.9) PFS Sensitivity: All deaths as events, 0.87(0.75-1.02) 39.5(34.9, 46.0) 42.8(37.4, 49.7) PFS Sensitivity: Censor at alternate Rx 0.83(0.69-0.99) 35.0(31.3, 42.6) 38.7(34.7, 49.0) PFS Sensitivity: Event at alternate Rx 0.84(0.73-0.97) 18.0(14.2, 23.0) 24.4(20.9, 27.9) Overall survival 0.92(0.75-1.12) 119(100, NE) 118(103-NE)

7522 Background: Movement and neurocognitive treatment emergent adverse events (MNTs), cranial nerve palsies (CNPs) and immune-effector cell enterocolitis (IEC-EC) are late onset toxicities associated with cilta-cel and are associated with significant morbidity and mortality. We aimed to identify predisposing risk factors to allow for formulating risk-reduction strategies. Methods: Retrospective study of MM pts who received FDA approved cilta-cel at Mayo Clinic between Feb 2022-Dec 2024. Interrogated factors included demographics, disease and treatment characteristics, and selected lab values at different time points. In odds ratio (OR) analyses, pts were divided by toxicity type (1) No delayed toxicity (2) MNT (3) IEC-EC without MNT (4) isolated CNP. Differences between pts in the MNT, IEC-EC and CNP groups were compared separately in a pairwise manner vs. those with no delayed toxicity. Results: Of 235 pts, 26 (11%) had delayed toxicity [MNT = 8 (3%), IEC-EC = 9 (4%), CNP = 14 (6%)]; 3 pts had both MNT/IEC-EC and 2 had both CNP/IEC-EC. Median onset from CAR-T infusion for MNT, IEC-EC and CNP was 19 (range 8-96), 106 (35-169) and 21 (7-43) days respectively. Of 164 evaluable pts, those who had ICANS had increased odds for any delayed toxicity (OR 4.7; 95% CI 1.6-13.8). Pts who had ICANS (OR 7.7; 1.6-36.9), HLH/MAS (OR 6.2; 1.1-6.7) and Ferritin >400mcg/L at time of lymphodepletion (OR 6.3; 1.5-32) had increased odds for MNTs. Pts who received alkylator-based bridging therapy had increased odds (OR 6.1; 1.1-35) for IEC-EC. Analysis of serial post-CAR infusion lab values showed that peak ALC was the most significant variable with differences between groups shown in table. Median time to peak ALC was 12 days (IQR 11-13). ROC analysis determined peak ALC >3 x 10 9 /L as a meaningful cut point. Pts with peak ALC >3.0 x 10 9 /L had increased odds of developing any delayed toxicity (OR 9.3; 3.5-29.3), MNT and CNP (table). Absolute risk of any delayed toxicity was 33% in pts with peak ALC >3 x 10 9 /L vs 5% without. At this threshold, number needed to treat was 3.6. Conclusions: Real-world data shows that cilta-cel associated delayed toxicity is seen in ~10% of patients, with specific toxicity rates between 4-8%. Factors associated with these toxicities predominantly occur in the post CAR-T infusion period. Given that ALC expansion in the first 2 weeks correlate with CAR-T expansion, peak ALC is potentially predictive of toxicity and 3 x 10 9 /L may be an interventional threshold for primary prophylaxis. Peak ALC by toxicity groups. No ToxN=138 MNTN=8 CNPN=12 IEC-ECN=6 p value Peak ALC (10 9 /L), median (IQR) 1.8 (1.0-4.1) 6.2 (4.8-14.4) 4.3 (3.2-6.7) 3.6 (1.9-5.2) <0.001 1 ALC >3 x 10 9 /L, n (%) 43 (31%) 7 (88%) 10 (83%) 4 (67%) <0.001 2 Odd Ratios vs no Tox 3 , 95% CI 15.5 (2.6-293.7) 11.0 (2.8-73.9) 4.4 (0.8-25.0) 1 Wilcoxon/Kruskal-Wallis Tests, 2 Chi square test, 3 Logistic regression analysis.

PURPOSE Cytokine release syndrome (CRS) of any grade occurs in 56%-80% of bispecific antibodies (BsAbs) used in multiple myeloma (MM). Risk mitigation strategies are required to expedite escalation of care if toxicities develop. The rarity of grade 3 or 4 CRS compels protocolized outpatient management of BsAbs as outpatient practice may avoid hospital admissions and costly resource utilization without compromising safety. MATERIALS AND METHODS Patients with MM who received BsAb step-up dosing (SUD) from August 23, 2023, to March 29, 2024, were enrolled. Baseline demographics, patient outcomes, and CRS management were reviewed to assess the safety of outpatient practice. Resource utilization was also analyzed. RESULTS In this study, 34 patients received outpatient SUD of BsAbs (teclistamab n = 17, talequetamab n = 17) with 16 remaining outpatient throughout the entire SUD period. CRS occurred in seven patients who did not require hospitalization, demonstrating the safety of outpatient management of BsAb toxicity, regardless of low-grade CRS. CRS was observed in 24 patients (maximum grade 2) and immune effector cell–associated neurotoxicity syndrome in four patients (maximum grade 3). All patients with CRS received steroids, including 12 patients at home when instructed. Tocilizumab was given to 13 patients, accounting for 18 doses. If all doses of BsAbs and tocilizumab were given outpatient, the medication margin would be $115,004 in US dollars (USD). CONCLUSION An outpatient-based practice for BsAb administration demonstrated safety and cost savings. The description of our practice and results of this study provide valuable insights into the safety, feasibility, and resource stewardship of outpatient management of BsAbs. Future research should attempt to predict and stratify CRS risk to deliver a tailored supportive strategy and continued increase of outpatient management.

ABSTRACT As the treatment paradigm for Waldenström macroglobulinemia (WM) continues to evolve, the debate surrounding the prioritization of depth of response versus disease control as therapeutic goals gains significant relevance. However, the impact of depth of response from fixed‐duration therapy on overall survival (OS) was unclear. This multicenter study evaluated the prognostic impact of depth of response using a landmark survival analysis. A total of 440 patients with WM treated with frontline fixed‐duration regimens were included. Attaining a major response (MaR) was associated with superior outcomes, including significantly longer OS. The estimated 5‐year PFS rates for patients with MaR at 6 months versus not were 50% versus 32%, respectively, p < 0.001, and the estimated 5‐year OS rates for patients with MaR at 6 months versus not were 89% versus 70%, respectively, p < 0.001. In a multivariable analysis, MaR at 6 months was independently associated with superior PFS (HR 0.66, p = 0.007) and OS (HR 0.28, p < 0.001). Similar results were seen when considering deeper responses (CR + VGPR vs. PR). Depth of response at 6 months is an important prognostic marker in WM and an independent predictor of PFS and OS. These results support its utilization as a suitable endpoint in clinical studies in WM.

Abstract In this study, we first analyzed data from 147 patients with solitary plasmacytomas treated at the Mayo Clinic between 2005 and 2022 and then expanded our investigation through a systematic review and meta-analysis of 62 studies, encompassing 3487 patients from the years 1960 to 2022. Our findings reveal that patients with up to 10% clonal plasma cells in their bone marrow (BM), denoted as plasmacytoma +, had a significantly reduced median disease-free survival (DFS) of 15.7 months vs 79 months, P &lt; .05, observed in patients with true solitary plasmacytomas, with no clonal cells in the BM. Risk factors identified for shorter DFS included the presence of clonal plasma cells in the marrow and a difference between involved and uninvolved free light chains of &gt;5 mg/dL. The meta-analysis portion of our study highlighted a male predominance among patients, with a median age of 58 years, and confirmed radiation therapy as the predominant treatment modality. We also found that DFS rates at 3, 5, and 10 years were 66.9%, 55%, and 42.1%, respectively, and noted a significant difference in outcomes between patients with bone and extramedullary plasmacytomas, with the latter group exhibiting better survival rates. This dual-faceted approach provides a thorough overview of survival rates and critical risk factors for patients with plasmacytoma, underscoring the vital role of accurate disease staging at diagnosis and the impact of tumor location on patient prognosis.