Citations

Abstract Teclistamab is an anti-CD3-/B-cell maturation antigen (BCMA) bispecific antibody approved for use in relapsed/refractory multiple myeloma. We undertook a retrospective study of post-approval, real-world outcomes with teclistamab in the US Multiple Myeloma Immunotherapy Consortium. Among 509 patients, 89% would have been ineligible for the MajesTEC-1 trial, primarily due to prior BCMA-directed therapy, cytopenias, or diminished performance status. Cytokine release syndrome occurred in 54% (1.4% grade ≥3) and immune effector cell–associated neurotoxicity syndrome in 11% (2.2% grade ≥3), with no fatal events. Infections occurred in 42% and contributed to death in 5%. Partial response (PR) or better was achieved in 53% and very good PR or better in 45%. With 10.1 months of median follow-up, the estimated median progression-free survival (PFS) was 5.8 months and 12-month overall survival was 61%. Independent predictors of less than very good PR and shorter PFS included BCMA-directed chimeric antigen receptor T-cell therapy in the previous 9 months, high disease burden, lymphopenia, and elevated ferritin. Significance: T cell–engaging bispecific antibodies such as teclistamab represent an important new treatment modality for multiple myeloma and other blood cancers. This study evaluates the real-world safety and efficacy of teclistamab, including its activity in populations not represented in the initial phase I/II study, and identifies clinical variables associated with treatment response. See related commentary by Zweegman et al., p. 542

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.

7032 Background: The impact of immune cell counts pre LD and during immune reconstitution on CAR T therapy outcomes is poorly understood. We investigated the association between CD4, CD8 and NK cell counts and CAR T therapy outcomes in patients with LBCL. Methods: Retrospective study of R/R LBCL patients who received CAR T cells between 2016-24 at Mayo Clinic, Rochester, were included in this analysis. Peripheral blood CD4, CD8 and NK counts were measured pre LD and at M1 post CAR T infusion. The receiver operating characteristic (ROC) curve was used to determine the optimal cutoff for pre LD and M1 immune cells to predict patients who were alive and in remission at 6 months (M6) post CAR T infusion. Patients who progressed or were lost to follow up prior to day 30 were excluded from M1 ROC analysis. Results: Of 140 patients, 81 were alive and in remission at M6 (Group A), while 59 had relapse or death (Group B). Axicabtagene ciloleucel was the CAR T product given in 81% of patients (114/140). Median pre LD CD4 counts were significantly lower in Group B compared to group A (143 vs 280 cells/µL, p = 0.001). No significant difference was observed in median pre LD CD8 counts (205 vs 221 cells/µL, p = 0.8). ROC analysis identified an optimal pre LD CD4 count of 124.5 cells/µL for M6 alive+remission. Lower pre LD CD4 counts (<124.5) predicted worse progression free survival (PFS) in univariate (HR = 3.02, 95% confidence interval [CI]: 1.73–5.27, p< 0.01) and multivariable analysis (MVA) adjusted for IPI and the number of prior lines (aHR = 2.54, 95% CI: 1.39–4.62, p< 0.01).Lower pre LD CD4 counts also predicted inferior overall survival (OS) in MVA (aHR = 2.27, 95% CI: 1.08–4.77, p = 0.03). (Table 1) On day 30 landmark analysis, ROC identified M1 optimal CD4 count of ≥ 99.5 cells/µL to be associated with a trend toward superior PFS (P=0.09), but not OS (p=0.90) in MVA. Median pre LD NK cell counts were significantly lower in Group B (73 vs 98 cells/µL, p = 0.04). ROC analysis identified an optimal pre LD NK count of 151 cells/µL for M6 alive + remission. Lower pre LD NK counts (<151) predicted worse PFS, both on univariate (HR = 4.17, 95% CI: 1.29–13.47, p = 0.02) and MVA (aHR = 4.64, p< 0.01). The lower pre LD NK cell count group had worse OS in MVA (aHR = 5.69, 95% CI: 1.16–28.1, p = 0.01). (Table 1) On D30 landmark analysis, M1 NK cell count of ≥ 128.5 cells/µL was associated with a trend toward superior PFS (P=0.08), but not OS (p=0.30) in MVA. Conclusions: Pre LD CD4 and NK cell counts are significantly associated with PFS and OS post CAR T therapy in patients with R/R LBCL. Pre-treatment immune subset levels may identify patients at higher risk of relapse or death after CAR-T therapy. Groups Median PFS 2 Year PFS Median OS 2 Year OS CD4 ≥124.5 cells/µL (N=75) NR 58% 3.31 years 67% CD4 <124.5 cells/µL (N=30) 2.2 months 22% 1.59 years 45% NK ≥151 cells/µL (N=17) NR 77% NR 84% NK <151 cells/µL (N=82) 10.6 months 44% 3.31 years 62%

e19008 Background: Cytokine release syndrome (CRS) is typically reversible in CAR-T therapy, while hyperinflammatory syndromes like macrophage activation-like syndrome (MAS-L) and high-grade immune effector cell-associated hemophagocytic syndrome (IEC-HS) are associated with significant morbidity and mortality. Early interventions are critical for improving outcomes. We aim to analyze clinical cytokine assays and cellular phenotypes early in hyperinflammatory syndromes to identify profiles for severe cases to inform management decisions. Methods: This study included 113 CAR-T patients (pt) (September 2019-March 2024) with cytokine profiles (CP) performed at the second tocilizumab dose or with suspected hyperinflammatory states (CP1), followed by assessments at 24 hours (CP24) and 48 hours (CP48). 52 pts consented to blood (PB) and bone marrow (BM) cell immune phenotyping at pre-treatment (pre-LD) and day 1 for PB. Results: Among the 113 pts, CRS pts (N=74), when compared to MAS-L(N=19) & IEC-HS (N=20) at CP1, had lower levels of TNF (median in pg/mL; 31, 62.9, 47.7) , IL-18 (794, 1353, 2011), and MCP-1 (689, 2722, 2485.5). While MAS-L and IEC-HS had similar CP1 profiles, CP24 and CP48 differed between them: TNF & MCP-1 levels decreased in MAS-L but remained elevated or increased in IEC-HS. IL-18 was stable in MAS-L but increased steadily daily in IEC-HS. Infections were more frequent in IEC-HS (CRS: 43%; MAS-L: 58%; IEC-HS: 85%; p=0.002). Notably, patients who died with persistent E. faecium bacteremia had higher IL-18 in CP48. In the 52 pts with cell phenotypes available by flow, 33 had CRS, 18 MAS-L and 8 IEC-HS. The correlation between cell phenotypes and cytokine levels showed that elevated TNF at CP1 correlated with increased non-classical monocytes in pre-LD BM and higher NK and NK-T cells in pre-LD PB. Similarly, elevated IL-18 CP48 levels correlated with increased CD8 T-cells, NK-T cells, and intermediate monocytes in pre-LD PB, as well as increased NK cells at both pre-LD and day 1 (Table). Conclusions: We report distinct cytokine profiles in IEC-HS early in the inflammatory course post-CAR-T therapy. These elevated cytokines correlate with specific immune cell subsets, including BM-resident monocytes, intermediate monocytes with heightened cytokine trafficking and inflammatory capacity. This study demonstrates the feasibility for identifying potential biomarkers for early risk stratification and targeted interventions. Cytokine Sample source Immune cells R P value TNF CP1 BM pre-LD Non-classical monocytes (CD14loCD16+) 0.38 0.025 PB pre-LD Monocytes (All) 0.47 0.022 NK cells (CD56+CD16+) 0.34 0.024 NK-T cells (CD3+CD56+CD16-) 0.29 0.04 IL-18 CP48 PB pre-LD CD8+ T-cells 0.59 0.0093 NK-T cells (CD3+CD56+CD16-) 0.53 0.023 Intermediate monocytes (CD14+CD16+) 0.58 0.012 PB pre-LD NK cells (CD56+CD16+) 0.56 0.49 0.015 0.024

ABSTRACT Background and Hypothesis Teclistamab, a novel bispecific monoclonal antibody targeting CD3 and B cell maturation antigen (BCMA), and chimeric antigen receptor T cell (CAR-T) therapy are promising options for treating relapsed/refractory multiple myeloma (MM). However, the rates of acute kidney injury (AKI) associated with teclistamab remain inadequately characterized. This study aims to compare the incidence, severity, and outcomes of AKI between patients receiving teclistamab and CAR-T therapy. Methods This was a retrospective study involving 64 patients with relapsed/refractory MM treated with either teclistamab or CAR-T therapy. All patients had previously received at least four lines of chemotherapy before being treated with either teclistamab or CAR-T. The primary outcome was the incidence of AKI, and secondary outcomes included AKI severity, kidney recovery rates, and mortality. Kaplan–Meier estimates for AKI-free survival were calculated, and hazard ratios (HRs) for AKI risk were determined using Cox proportional hazards models. Results Sixty-four patients met inclusion criteria for this study (30 received CAR-T and 34 received teclistamab therapy). Among these patients, 14 AKI events occurred in total (22%), with 10 events (29%) in the teclistamab group and four events (13%) in the CAR-T group. AKI-free survival estimates at 180 days after treatment initiation were 68% [95% confidence interval (CI): 53%–87%] for teclistamab patients and 90% (95% CI: 79%–100%) for CAR-T patients. While patients receiving teclistamab were found to have an increased risk of an AKI event compared to those receiving CAR-T therapy, the results were not statistically significant [HR (95% CI): 3.38 (0.93–12.31), P = .065]. Conclusions This study suggests that patients treated with teclistamab may experience a higher incidence of AKI compared to those receiving CAR-T therapy. However, further research is required to determine whether this increased risk is attributable to disease progression or teclistamab itself. These results highlight the need for close kidney function monitoring in patients receiving teclistamab.

Introduction: Teclistamab (Tec) is the first approved BCMA x CD3 bispecific antibody for the treatment of triple-class-exposed patients with relapsed/refractory multiple myeloma (RRMM) based on the pivotal MajesTEC-1 study. Tec was associated with high overall response rate (ORR) of 63% in heavily pretreated patients. After a longer follow-up of 30.4 months, CR rate was 46.1%, median duration of response (DOR) was 24 months (95% CI, 17.0 - not estimable), and median progression-free survival (PFS) was 11.4 months (95% CI, 8.8 - 16.4). Herein, we present updated analysis of real-world outcomes and safety with tec in RRMM with extended follow-up of more than 12 months. Methods: This is an international multicenter retrospective study of patients with RRMM treated with tec on-label at 9 academic centers from 5 countries (United States, United Kingdom, Greece, Spain, and Canada) through the International Myeloma Working Group (IMWG) Immunotherapy Committee. Patients with RRMM treated with commercial tec at the respective institutions between May 24, 2022 to January 4, 2024 were included. Median follow-up was 14 months with data collected until July 15, 2024. High-risk cytogenetic abnormalities (HRCA) was defined as 1q+, t(4;14), t(14;16), t(14;20), and/or del(17p). Response was assessed using the IMWG consensus criteria. Patient characteristics were summarized by frequency (percentage) or median (interquartile range [IQR] or range). PFS, overall survival (OS), DOR were evaluated using the Kaplan-Meier method. Results: There were 223 patients included in this analysis with the following characteristics: median age of 67 (range 33-91) with 24% ≥75 years; 45% female; 74% White, 10% Black, 9% Asian, and 7% other/unknown; 86 of 176 (49%) with high risk cytogenetics, including del(17p), t(4;14), t(14;16), t(14;20), and gain/amp 1q; 29.4% (37/126) with known extramedullary disease; 14% with creatinine clearance ≤30 ml/min. Patients received a median of 6 (IQR, 4-8) prior lines of therapy with 52% (107/206) being penta-drug refractory. Among 212 patients with available data, 161 (75.9%) patients would have been ineligible for MajesTEC-1. There were 94 (42%) patients who received prior BCMA-directed therapy (29.8% antibody-drug conjugate [ADC] alone; 45.7% CART alone; 6.3% bispecific antibody alone; 17.0% ADC and CART). Median time from diagnosis to tec initiation was 6.1 (range 0.6-29.2) years. For the 206 response-evaluable patients, ORR was 66%, including 25.2% ≥CR, 33.5% VGPR, and 7.3% PR. ORR for the 90 response-evaluable patients with prior BCMA-directed therapy was 54.5% (21.1% ≥CR, 26.7% VGPR, 6.7% PR). After a median follow-up of 14 (95%CI, 13-14) months, median PFS and OS were 8.8 (95% CI, 5.5-14) and 20 (95% CI, 18-not reached [NR]) months, respectively. 12-month PFS estimate was 46% (95% CI, 40%-54%), and 12-month OS rate was 65% (95% CI, 59%-72%). Median DOR was 17 (95% CI, 17-NR) months with 12-month estimate of 68% (95% CI, 60%-77%). Tec step-up dosing occurred in the outpatient setting for 57 (25.6%) patients. CRS occurred in 119 out of 222 (53.6%) patients with almost all being grade 1-2, except for 1 grade 4 event. ICANS occurred in 18 out of 216 (8.3%) patients (grade 1-2: 5.1%; grade 3-4: 2.8%). Any grade infection occurred in 130 (58.3%) patients; 25.1% of patients had grade ≥3 infection, including 10 patients with grade 5 infection. While receiving teclistamab, 79 (35.4%) patients had ≥2 infections. IVIG was given in 114 out of 164 (69.5%) patients. Conclusion: In this multicenter international real-world analysis of outcomes and safety associated with tec, ORR was high at 66% with 25.2% of patients achieving ≥CR. CR rates may be underestimated due to infrequent bone marrow confirmation in the real-world datasets. Encouragingly, ORR was 54.5% in BCMA exposed RRMM patients, including 21.1% with ≥CR. After a median follow-up of 14 months, heavily pretreated patients including patients with prior BCMA therapy had durable responses with median PFS of 8.8 months and median DOR of 17 months. There were no new safety signals noted in this real-world study. This is the largest real-world study to date of teclistamab with long-term follow-up of more than 12 months. Additional data including more patients, longer follow-up and results from difficult to treat subgroups will be presented at the meeting.

Background: Management of cytokine release syndrome (CRS) with chimeric antigen receptor T cell therapy (CAR-T) has evolved in the last decade. First line treatment tocilizumab (toci) was initially given for grade 2 or higher CRS in clinical trials (Toci/CRS≥2). Earlier use of toci in grade 1 CRS was found to be safe without negative impact on clinical response in cohort 4 of ZUMA-1 study for axicabtagene ciloleucel (axi-cel) for B-cell non-Hodgkin lymphoma (NHL; Toci/CRS1). This practice was also adopted for other CAR-T therapies for other disease indications. Subsequently, FDA also updated the package insert for axi-cel in 2021 to include the use of prophylactic dexamethasone (ppx dex) to be given on days 0, 1, 2 of CAR-T infusion based on the results from cohort 6 of ZUMA-1. We examined CRS and ICANS (immune effector cell associated neurologic syndrome) outcome of patients who received FDA approved axi-cel in standard-of-care (SOC) practice with these evolving practices. Of note, adoption of ppx dex has been variable across CAR-T treatment centers in the US (Khurana et al, Blood 2022). At Mayo Clinic Rochester, patients considered high-risk for severe CRS/ICANS (those who received bridging therapy and had LDH above upper limit of normal and/or with secondary CNS involvement or other CNS pathologies) would be considered for ppx dex. Methods: Medical records of patients who received axi-cel in SOC between 2018 and 2023 at Mayo Clinic Rochester were reviewed. ASTCT guideline was used for CRS and ICANS grading. Categorical variables were compared using Chi-squared test and continuous variables were compared using Kruskal-Wallis test. Results: Among 187 pts receiving SOC axi-cel, the median age was 60 years and 121 (65%) were males, 152 (81%) had CRS, of which 73 (39%) were grade ≥2; 97 (52%) had ICANS, of which 65 (35%) were grade ≥2. Of the 152 CRS pts, 54/152 (36%) pts never received toci or ppx/dex. Of the pts who received Toci, 35/152 (23%) received Toci when CRS is at least grade 2 (Toci/CRS≥2), 49/152 (32%) received Toci/CRS1 without ppx dex (Toci/CRS1), and 14 (9%) received ppx dex with Toci given in CRS1 when pts developed CRS (PPX DEX). Baseline demographics were comparable except age (Toci/CRS≥2: 58y; Toci/ CRS1: 63y; ppx dex: 50y; p=0.001) and pre-LD CRP (Toci/CRS≥2: 34mg/L; Toci/ CRS1: 6mg/L; ppx dex: 16mg/L; p=0.002). Pre-LD LDH and ferritin were also comparable. PPX DEX or Toci/CRS1 had significantly lower rate of maximum grade CRS≥2 (PPX DEX: 4 (29%); Toci/ CRS1: 20 (41%); 35 (100%); p&lt;0.001) and duration of CRS (PPX DEX: 2.5d; Toci/ CRS1: 3d; Toci/CRS≥2: 5d; p&lt;0.001). Time to onset of CRS was not statistically different between the 3 groups. Not surprisingly, Toci/CRS1 group had higher overall rate of toci use, compared to . Interestingly, use rate of ≥2 doses of Toci or siltuximab was significantly higher in Toci/CRS1 or PPX DEX (PPX DEX: 8 (57%); Toci/ CRS1: 26 (53%); 9 (26%); p=0.02). Pt who received PPX DEX or Toci/CRS1 had a significantly lower rate of ICANS (PPX DEX: 6 (43%); Toci/ CRS1: 33 (67%); 32 (91%); p=0.001) and rate of max grade ICANS ≥2 (PPX DEX: 3 (21%); Toci/ CRS1: 23 (47%); 27 (77%); p&lt;0.001). The time to onset and duration of ICANS was not different among the 3 groups. Conclusion: Our real-world study shows that earlier use of Toci in grade 1, compared to its first use in grade 2, can result in lower overall incidence of more severe CRS, duration of CRS, incidence of ICANS and more severe ICANS. While we selected patients at higher risk for having more severe CRS in our PPX DEX cohort, experience to date suggests that these patients, compared to toci/CRS&gt;=2 cohort, could also have reduced severity of CRS and ICANS with this updated management.

Background Emerging evidence has demonstrated rare subacute to late neurological toxicities (NTs) after BCMA CAR T-cell therapy (CAR-T) in multiple myeloma (MM). These adverse events can be categorized as: 1) Parkinsonism (PD), 2) cranial nerve (CN) palsies, and 3) peripheral neuropathies/Guillan Barré syndrome (GBS). These toxicities can cause significant morbidity, but given their relative rarity in clinical trials, there is limited data regarding evaluation and treatment. To our knowledge, this is the largest and only global registry of delayed NTs after BCMA CAR-T. Methods We retrospectively established a registry of NTs via the Immune Therapy Working Committee of the International Myeloma Working Group (IMWG). We gathered data pertaining to demographics, MM characteristics, MM response, NT signs/symptoms, diagnostic workup, and treatment. Result A total of 52 patients with delayed neurotoxicity were included from 14 institutions and 6 countries; 92% received ciltacel, 4% idecel, and 4% investigational CAR-T. Median age at CAR-T infusion was 65 years; 69% were male and 88% were Caucasian. Median bone marrow plasma cell (PC) burden was 15% prior to CAR-T (range 0-95%). Patients received a median of 4 prior lines of therapy (LOT), with 67% progressing on last LOT. Seventeen percent had pre-existing neurological diagnoses (including stroke, epilepsy, migraines). We identified sixteen cases of PD (94% with movement disorder, 69% with cognitive impairment, 75% with personality changes), occurring at a median of 26 days (range: 15-87) after CAR-T. Ninety four percent had CRS (grade (G)1 50%, G2 38%, G3 6%, G4 0%), while 19% had ICANS (G1 13%, G2 6%, G3-G4 0%). Median peak absolute lymphocyte count (ALC) was 9.5 x 109/L, peak C-reactive protein (CRP) 60.9 mg/L, and peak ferritin 1893.5 ug/L within the first 30 days. Concurrently, 3 upper respiratory infections (URIs) and 2 low-level HHV7 in the cerebrospinal fluid (CSF) were detected. A median of 73% of T-cells in the CSF were CAR-T, based on a flow cytometry assay. Ten patients received steroids (median 19 days after symptoms, 70% partial response, 20% no response, 10% unknown), 2 received intrathecal (IT) methotrexate-based therapy (median 32 days after symptoms, 1 with no response, 1 unknown), 5 received intravenous (IV) cyclophosphamide (median 31 days after symptoms, 40% full response, 20% partial response, 40% no response), 4 received high-dose IVIG ≥1g/kg for one or more dose (50% partial response, 50% no response), and 6 received dopamine agonists. There were 37 CN palsies (76% CN7, 15% CN6, 7% CN5, 2% CN3), occurring at a median of 37.5 days (range: 7-482) after CAR-T. Eighty one percent had CRS (G1 68%, G2 14%, G3-G4 0%); 11% had G1 ICANS (G2-G4 0%). Median peak ALC was 4.1 x 109/L, CRP 25.4 mg/L, and ferritin 543 ug/L within the first 30 days. We identified 2 concurrent URIs, 4 CMV viremia (50% with viral load &gt;1500 IU/mL), 1 HHV6 viremia, and 1 HSV in the CSF. Thirty-two (86%) received steroids for a median duration of 12 days, 50% with full response, 3% with no response, and 47% with partial response (of which 43% had later full recovery without further intervention). One received IT methotrexate and another received IV cyclophosphamide without response. Thirteen (41%) received IVIG, of which 38% was high-dose IVIG. Four patients with CN palsies developed peripheral neuropathy/GBS. Eight patients (15%) in this cohort were not heavily pre-treated (≤1 prior LOT); 7 developed CN palsies (6 after ciltacel, 1 after investigational CAR-T) and 1 PD (after idecel). These patients had median &lt;5% PC; none had extramedullary disease. Median ALC was 4.14 x 109/L, CRP 33 mg/L, and ferritin 448.5 ug/L within the first 30 days. Conclusions Delayed NT requires prompt recognition, evaluation for alternative causes, and treatment. In our cohort, the majority of patients were male and Caucasian, suggesting that sex and race may impact the likelihood of developing NT. Individuals with PDs had greater inflammatory response (CRS, ALC, CRP, ferritin) compared to those with CN palsies. CN palsies responded to steroids and/or IVIG, whereas PD had at best partial response to steroids, prompting additional therapy. These toxicities notably did occur in less heavily pre-treated patients, perhaps driven by immune fitness and greater circulating T-cells rather than MM burden. At the time of the annual meeting, data will be updated with additional NTs from less heavily pre-treated patients.

Introduction: Talquetamab (Talq) is a GPRC5D targeting bispecific antibody recently approved for the treatment of relapsed refractory multiple myeloma (MM) based on the MonumenTAL-1 study. Real World Evidence (RWE) is needed to understand the safety and efficacy of Talq in patients treated outside of a clinical trial as they may have different outcomes and toxicities. Here we report outcomes of 118 patients treated with Talq. Methods: Patients treated with standard-of-care Talq were included. Data was collected through a retrospective chart review from 01/2023 until 7/2024 from 7 International Myeloma Foundation (IMF) associated MM academic centers. Results: 118 patients were included in the analysis. The median age was 64, 37% had HR disease, 22% had EMD at presentation. The median LOT was 6, median number of immunotherapies before TAL was 2 (range 1,4) and 71% received prior BCMA therapy. 72% were triple refractory and 44% were penta refractory. 25% (n=60) would not have been eligible for TAL clinical trial due to exclusion criteria and15% had an ECOG of 2 or greater. 18% (n=97) received TAL as an outpatient and the median number of hospital days was 9 (0,37) for inpatients. CRS during Step up Dose (SUD) 1 was present in 30% Gr 1 (57%), Gr2 (11%), Gr 3 (6%), CRS during SUD 2 was present in 31%, Gr 1 (65%), Gr 2 (11%), CRS during SUD 3 when administered was present in 14% , Gr 1 (82%), Gr 2 (6%) and with first full dose was 12% , Gr 1 (71%), unknown (29%). ICANS occurred in 6% (7/97), Gr 1 (14%), Gr 2 (29%), Gr 3 (14%) and unknown in 43% there was no evidence of HLH. Skin toxicity was present in 62% of patients (n=105/118) with 4% needing dose interruptions and presented as rash (20%), dryness (42%) and itching (20%). Nail toxicity was present in 20% (n=65/118), with 9% needing dose interruptions. Dysgeusia was present in 51% (n=97/118), with 10% needing dose interruptions. Oral toxicity manifest as stomatitis (10%), glossitis (1%), ulcerations (2%), dry mouth (27%), was present in 34% (n=61/118), with 12.5% needing dose interruptions. Infections were present in 34% (n=82/118) and CMV reactivation in 23% while only 1 patient needed treatment for CMV. The Overall Response Rate (ORR) was 64.9% with a VGPR rate or higher of 43.3% in this population. Updated efficacy data including PFS will be reported at the time of presentation Conclusions: This is the first largest RWE of the safety and efficacy of Talq in a heavily pretreated population with a high prior BCMA exposure. The ORR is consistent with a prior study by Jakubowiak et al which showed an ORR OF 65.7% after prior T cell engagers. The safety profile - CRS, ICANS, skin and oral toxicities was similar to the MonumenTAL study, CMV reactivation was higher and this may be related to treatment with prior immunotherapies and should be monitored in the future. This report shows that Talq has a similar safety and efficacy profile in the real world when sequenced after prior BCMA therapies.

Background: Chimeric antigen receptor T-cell (CAR-T) therapy has shown substantial promise in treatment of hematological malignancies, including non-Hodgkin Lymphoma (NHL). A subset of patients develop prolonged cytopenia, comprising quality of life, increasing healthcare utilization, and imparting considerable morbidity and mortality. Therapy-related myeloid neoplasms (t-MN), typically seen in patients who receive DNA-damaging agents such as radiotherapy and alkylators, have also been observed in CAR-T recipients. CAR-Hematotox score predicts the development of hematotoxicity in CAR-T recipients using laboratory parameters obtained at lymphodepleting (LD) chemotherapy, a timepoint when the patient has already gone through leukapheresis thus committed to the CAR-T process. Therefore, it is critical to identify patients at the highest risk of prolonged cytopenia and/or t-MN prior to apheresis, making it possible for a better triage of those who will proceed with CAR-T and those who might benefit from other strategies. Methods: A retrospective analysis was conducted in NHL patients who received commercial CAR-T products between January 2018 and March 2024 at Mayo Clinic Rochester, Arizona and Florida. Clinical and laboratory data including age, hemoglobin (Hb), absolute neutrophil count (ANC), platelet (PLT), ferritin, and LDH, obtained at the initial CAR-T evaluation, typically within 1 week of leukapheresis, were used for analysis. Prior lines of therapies including autologous stem cell transplant (ASCT) were collected. Prolonged cytopenias were defined as Hb &lt; 8 g/dL, ANC &lt; 0.5 x 109/L, and/or PLT &lt; 50 x 109/L at 3 months after CAR-T. t-MN was diagnosed per WHO 2016. For prolonged cytopenia, the optimal cutoff points for continuous variables were determined by maximizing the sum of sensitivity and specificity. Logistic regression was then used to determine the factors associated with cytopenia at 3 months post-CAR-T. For t-MN, maximally selected log-rank statistics was used to determine the optimal cutoffs. We used competing risk analysis to determine the factors associated with development of t-MN. Death without t-MN was considered a competing risk. For both analyses, the factors with P &lt; 0.1 in univariate analysis (UVA) were included in multivariate analysis (MVA). Results: Among the 387 NHL patients, with a median follow-up of 11 months (95% CI 8.7 - 12.2 months), 56 (14.4%) developed (41, 10.5% with 1 cytopenia; 14, 3.6% with 2 and 1, 0.2% with cytopenia in all 3 lineages), 20 (5.2%) developed and 315 (81.2%) did not have either. Factors associated with prolonged cytopenia: were age &gt;, PLT ≤ 150, ferritin ≥ 600, and LDH ≥ 250. Univariate analysis identified baseline Hb, ANC, PLT and ferritin to be significantly associated with prolonged cytopenia. MVA identified Hb ≤ 11 (HR = 1.98; 95% CI 1.03-3.85, P = 0.042) and PLT ≤ (HR = 2.56; 95% CI 1.39-4.78; P = 0.003) to be associated with the development of prolonged cytopenia. Factors associated with t-MN:were age &gt; 65 years, Hb ≤ 9 g/dl, ANC &lt; 3.8, PLT ≤ 80, Univariate analysis identified age, Hb, ANC, PLT, ferritin, and ≥ 3 prior lines of treatment to be significantly associated with t-MN. On MVA, age ≥ 65 (HR = 3.91; 95% CI 1.52-10.03; P = 0.004), Hb ≤ 9 (HR = 3.49; 95% CI 1.38-8.85; P = 0.008), ferritin ≥ 300 (HR = 3.06 ; 95% CI 1.08-8.67; P = 0.035) and ≥ 3 prior lines of therapy (HR = 3.25; 95% CI 1.33-7.94 ; P = 0.010) were associated with t-MN development. Association of prolonged cytopenia with t-MN development: Prolonged cytopenia was noted in 45% of patients who developed t-MN and 15% of those who did not (P = 0.002). Cumulative incidence of t-MN at 1 year was 3.3% and the presence of prolonged cytopenia was associated with a higher 1of t-MN (HR 8.93, 95% CI 2.15 - 37.1, P = 0.003). Conclusions: Readily accessible clinical and lab data such as blood count and inflammatory markers at the time of CAR-T evaluation were associated with the development of prolonged cytopenias. Similarly, advanced age, anemia, high ferritin levels and history of ≥3 lines of therapy were associated with the development of t-MN. These findings, when validated in larger dataset, can be used for patient counseling and therapy selection by identifying patients at high-risk of developing hematotoxicity and/or t-MN development.