Ge, Wenzhen

Introduction Linvoseltamab is an investigational, BCMA×CD3 bispecific antibody designed for the treatment of RRMM. High objective response rates (ORR) to linvoseltamab 200 mg in the LINKER-MM1 trial (NCT03761108) were demonstrated across high-risk subgroups, including patients aged ≥75 years, patients with high-risk cytogenetics, and patients with penta-class refractory status. The aim of this study was to compare ORR, overall and in key subgroups, between patients in Phase 2 of the LINKER-MM1 trial and patients in an international RW SOC external control arm (ECA). Methods The ECA was derived from a chart review of 16 academic sites across 10 countries that are part of the International Myeloma Foundation (IMF)-International Myeloma Working Group (IMWG) and 2 US electronic health record databases (COTA and Guardian Research Network [GRN]). Included patients initiated ≥1 anti-MM treatment after meeting key eligibility criteria of LINKER-MM1. Weighted random sampling and inverse probability of treatment weighting (IPTW) were used to select 1 line of therapy (LOT) per patient and balance the overall ECA and trial populations on prespecified prognostic factors (Kumar S, et al. IMS 2023). For ORR assessment, LINKER-MM1 and IMF-IMWG used independent central review committees per IMWG criteria, COTA used algorithmic assessment based on IMWG criteria, and GRN used physician-assessed responses. Prior to conducting comparative analyses, an independent committee of epidemiology and oncology experts reviewed the comparability of the cohorts and endpoint assessments, and approved study continuation. ORR among patients in LINKER-MM1 and patients in the ECA was compared overall and across prespecified subgroups (≥10 patients per subgroup), including age, race, cytogenetic risk score, international Staging System (ISS), presence of extramedullary plasmacytoma (EMP), refractory class, bone marrow plasma cell (BMPC) proportion, and number of prior LOTs. Results Median duration of follow-up was 14.3 months (data cut-off: January 6, 2024) for patients receiving linvoseltamab (n=105) and 13.6 months for the ECA (n=307; n=194, n=72, and n=41 from IMF-IMWG, COTA, and GRN, respectively). Following IPTW, 13 prognostic factors with <30% missingness were balanced between cohorts, with an effective sample size in the ECA of 197. After adjustment, ORR was significantly higher in patients who received linvoseltamab compared with patients in the ECA (69.5% vs 45.7%, odds ratio [OR] 2.5 [95% confidence interval (CI) 1.6-4.1]) and in key subgroups with age 65-74 years (76.9% vs 48.3%, OR 3.6 [1.6-8.6]), age ≥75 years (72.4% vs 48.5%, OR 2.8 [1.1-7.4]), Black or African American race (82.4% vs 25.0%, OR 14.0 [3.0-85.4]), White race (68.9% vs 49.7%, OR 2.2 [1.3-4.0]), standard cytogenetic risk (72.3% vs 51.3%, OR 2.5 [1.3-4.8]), ISS stage III (58.8% vs 19.7%, OR 5.8 [1.5-25.2]), absence of EMP (71.6% vs 49.3%, OR 2.6 [1.5-4.6]), triple-class refractory status (68.2% vs 45.7%, OR 2.6 [1.5-4.4]), quadruple-class refractory status (66.7% vs 45.9%, OR 2.4 [1.3-4.3]), 4-5 prior LOTs (65.1% vs 40.4%, OR 2.8 [1.3-6.0]), and >5 prior LOTs (75.7% vs 36.1%, OR 5.5 [2.4-13.6]). Numerically higher (not statistically significant) or similar ORR was observed for patients receiving linvoseltamab compared with patients in the ECA with age <65 years (59.5% vs 46.8%, OR 1.7 [0.79-3.6]), high-risk cytogenetics (65.0% vs 63.1%, OR 1.1 [0.41-2.9]), ISS stage I (73.3% vs 64.6%, OR 1.5 [0.62-3.7]), ISS stage II (67.6% vs 53.5%, OR 1.8 [0.72-4.7]), presence of EMP (58.8% vs 56.9%, OR 1.1 [0.32-3.8]), penta-class refractory status (64.3% vs 48.5%, OR 1.9 [0.78-4.8]), BMPC <50% (77.0% vs 67.2%, OR 1.6 [0.61-4.3]), BMPC ≥50% (41.7% vs 36.0%, OR 1.3 [0.36-4.7]), and ≤3 prior LOTs (68.0% vs 66.4%, OR 1.1 [0.43-2.9]). Separate findings will be presented for IMF-IMWG and COTA/GRN data at the congress. Conclusions Linvoseltamab induced better ORR vs RW SOC treatments overall, and better or similar ORR in the key subgroups assessed, highlighting its therapeutic value across a range of patients with RRMM with heterogeneous risk profiles and levels of disease burden.

7561 Background: Pts with TCE RRMM have poor outcomes and a high unmet need, with no established SOC tx. LINKER-MM1 (NCT03761108) is a single-arm, Phase 1/2 study investigating linvoseltamab, a B-cell maturation antigen × CD3 bispecific antibody, in pts with RRMM who were previously treated with a proteasome inhibitor, immunomodulatory drug, and anti-CD38 antibody, or were triple-class refractory (TCR) to these tx. The aim of this study was to contextualize LINKER-MM1 by comparing outcomes with linvoseltamab vs a real-world (RW) external control arm (ECA). Methods: A RW ECA was derived from 2 US electronic health record databases (COTA, Guardian Research Network) of pts who started a new line of therapy (LOT) after classification as TCE or TCR and met key eligibility criteria for LINKER-MM1. Eligibility was assessed at the initiation of each new LOT, and all eligible LOTs were included in the ECA. Data in Phase 2 pts who received linvoseltamab 200 mg in LINKER-MM1 were included (data cutoff: Sep 8, 2023). Inverse probability of tx weighting (IPTW) was used to reduce imbalances between the RW and LINKER-MM1 cohorts. Key prognostic factors were identified using a systematic review and rank ordered by an international committee of MM experts (Kumar et al., 2023). Outcomes included overall response rate (ORR), progression-free survival (PFS), time to next treatment (TTNT), and overall survival (OS). An independent committee of epidemiology and oncology experts reviewed the comparability of the cohorts and endpoint assessments prior to conducting comparative analyses. Results: Comparative analyses were performed in 105 pts in the linvoseltamab cohort and 101 RW pts (137 LOTs). Following IPTW, the distribution of cytogenetic risk, age, TCR status, Eastern Cooperative Oncology Group Performance Status, and platelet count were balanced between the 2 cohorts (absolute standardized mean difference <0.10). After adjustment, pts receiving linvoseltamab had significantly improved ORR, PFS, TTNT, and OS vs the RW ECA (see table). Conclusions: Linvoseltamab significantly improved outcomes vs RW SOC in the US, highlighting its potential as a highly effective tx in pts with TCE RRMM. [Table: see text]

e23310 Background: Chimeric antigen receptor T-cell therapy (CAR T) is FDA-approved in pts with triple-class exposed (TCE) relapsed/refractory (RR) MM after four or more prior lines of therapy (LOTs). Real-world access to CAR T remains challenging due to manufacturing capacity, financial barriers, and pt fitness. Pts with certain pre-existing comorbidities (e.g., central nervous system disease, heart disease, secondary malignancies) are commonly excluded from clinical trials, including those investigating CAR T. The objective of this study was to identify the factors associated with the use of CAR T in pts with TCE RRMM to better understand the unmet need in this population. Methods: We conducted an observational cohort study using Medicare fee-for-service data; each pt in the CAR T intention-to-treat (ITT) population between 2021 and 2023 was matched to three non-CAR T pts, without replacement. Pts were eligible if they had an initial MM diagnosis, were continuously enrolled, were TCE, and did not receive treatment in a clinical trial. The index date was the ITT date. Baseline characteristics included age, sex, race/ethnicity, census region, three comorbidity indexes (Charlson, Elixhauser, CMS hierarchical condition categories [HCCs]), a claims-based frailty index (CFI), and dual enrollment in Medicare and Medicaid (as a proxy to social economic status [SES]). Logistic regression was used to derive odds ratios (ORs) and 95% confidence intervals (CIs) comparing the characteristics of CAR T vs non-CAR T pts. Results: Seventy-three ITT CAR T pts (nine underwent apheresis but did not receive CAR T) were matched to 219 non-CAR T pts by LOT and index year. Matched pts were treated with varied standard regimens (daratumumab-containing: 63%). Median prior LOTs were similar in the two cohorts (8; range 2–13). Median time from MM diagnosis to index date was 44.6 and 51.9 months for CAR T and non-CAR T pts, respectively. Compared with non-CAR T pts, pts in the CAR T population were younger (aged < 75 years: 59% CAR T vs 36% non-CAR T), less frail (mean CFI: 0.18 vs 0.20) and had higher SES (without dual enrollment in Medicare and Medicaid: 96% vs 81%), but were similar in terms of sex, region, and race/ethnicity. Variation in individual comorbidity prevalence was observed between CAR T and non-CAR T pts. In a multivariable regression analysis, factors strongly associated with lower odds of CAR T use included age ≥75 years (OR 0.29; 95% CI 0.16–0.53), comorbidities (lung/other severe cancers [OR 0.39; 95% CI 0.20–0.74] and chronic obstructive pulmonary disease [OR 0.32; 95% CI 0.10–0.99] defined by HCCs), and SES (OR 0.09; 95% CI 0.02–0.37). Conclusions: Older age, certain comorbidities, and lower SES are associated with lower odds of receiving CAR T in real-world pts with TCE RRMM, demonstrating an unmet need for more accessible and effective treatment options with acceptable safety profiles for these pts.

Background As therapeutic advances have increased life expectancy for patients (pts) with relapsed/refractory (RR) multiple myeloma (MM), second primary malignancies (SPMs) have become an increasingly important safety consideration. Prior studies have demonstrated that treatment with alkylators, autologous stem cell transplantation, and immunomodulatory drugs (IMiDs), specifically lenalidomide, are associated with increased risk of SPM. Pts who are triple-class exposed (TCE), defined as prior exposure to an IMiD, a proteasome inhibitor (PI), and an anti-CD38 monoclonal antibody (mAb), represent an increasingly large subgroup of RRMM pts. The objective of this study was to describe the incidence and characteristics of SPMs in Medicare-insured pts with TCE RRMM initiating a new line of therapy (LOT). Methods Adult pts with an incident diagnosis (Dx) of MM (≥2 outpatient Dx 30-365 days apart OR ≥1 inpatient Dx AND 6 months of continuous eligibility prior to initial Dx) during the study period (Nov 14, 2006-Dec 31, 2020) who were TCE (≥1 claim each for an IMiD, a PI, and an anti-CD38 mAb) were selected from the Center for Medicare and Medicaid Services Chronic Conditions Data Warehouse (TCE pts were assumed to have RRMM based on exposure). The first LOT after TCE was defined as the index LOT and the associated date of initiation was defined as the index date. Pts with SPMs prior to the index date were excluded. SPMs were identified based on having ≥2 outpatient Dx of SPM (of the same cancer type) 30-365 days apart OR ≥1 inpatient Dx of SPM. Dx of SPM included Dx of invasive malignancies or myelodysplastic syndromes (MDS), excluding MM, Waldenström macroglobulinemia, plasma cell leukemia, non-melanoma skin cancers, or primary bone malignancies that were preceded by a Dx of bone metastases. The incidence of SPM was calculated per 100 person years (PY) of follow-up, considering only the first SPM for each pt. Cumulative incidence of SPM (with death as a competing risk) was also calculated. For pts who experienced SPM, overall survival (OS) and measures of healthcare resource utilization (HRU) and costs (in 2021 USD, on a per patient per month [PPPM] basis) were calculated. Results A total of 3,088 TCE RRMM pts were identified, of whom 989 had no evidence of SPM prior to the index date (Table). These 989 pts had a mean age of 75.2 years, a mean of 2.9 prior LOTs and a mean of 3.1 years since MM Dx. Over a median follow-up of 7.1 months, 166 pts (19.3 per 100 PY) experienced an SPM, including 93 (10.8 per 100 PY) with a solid tumor and 73 (8.5 per 100 PY) with a hematologic malignancy. The latter included 27 (3.1 per 100 PY) with acute myeloid leukemia (AML) and 18 (2.1 per 100 PY) with MDS. The cumulative incidence of SPM (95% confidence interval [CI]) at 12, 24, and 36 months was 15.2% (12.8-17.9%), 19.7% (16.8-22.8%), and 23.8% (20.2-27.6%), respectively (Figure). Median (95% CI) OS from SPM Dx was 7.9 months (5.4-10.9). Kaplan-Meier estimated probability of survival (95% CI) at 12, 24, and 36 months following SPM Dx was 40.3% (31.6-48.9%), 27.6% (18.6-37.4%), and 9.5% (2.1-23.8%), respectively. Mean (95% CI) total costs after SPM were $22,514 ($19,105-$26,404) PPPM. Conclusions The incidence of SPM in Medicare-insured TCE RRMM pts is high. Many SPMs in these pts, such as AML, are life-threatening and may interfere with or prevent MM treatment. Pts with SPMs have poor survival and high HRU and costs. With increasing OS for RRMM pts due to therapeutic advancements, there is a need for effective treatments that are not associated with increased risk of SPMs.