Ma, Qiufei

e19504 Background: Initiation of bsAbs requires SUD with close monitoring, typically in IP settings, to mitigate early toxicities. As bsAb use expands, it is crucial to understand the financial viability for administering bsAbs, particularly non–PPS-exempt hospitals paid via a capitated, DRG-based method where costs may exceed payout. We compared net costs and payments for Medicare pts initiating bsAbs in the IP setting at non-PPS-exempt hospitals and explored cost variations for hospital characteristics and adverse events (AEs). Methods: Using Medicare FFS Parts A/B claims (10/25/21–10/20/24), pts ≥65 years with MM, IP bsAb initiation, and 12 mos continuous pre-index coverage were identified. Pts receiving other MM therapies <30 days post-index or treated in PPS-exempt hospitals were excluded. Hospital costs were estimated by applying revenue center–specific Medicare cost–charge ratios from CMS Hospital Cost Reports to IP facility charges. Outpatient (OP) bsAb costs were estimated using ASP/unit administered/wasted at the time of the claim. Costs for other OP services were estimated using revenue center–specific cost–charge ratios. Medicare payments were defined as total allowed amounts on IP and OP claims, and net cost as payments minus estimated costs. IP resource use and net cost recovery by academic vs nonacademic hospital, length of stay (LOS), and AEs were analyzed. Results: Of 3074 pts with a bsAb claim, 1129 met inclusion criteria. Mean IP LOS was 9 days (range 1–68). Hospital mean estimated IP cost/day for index hospitalization was $3963. Mean estimated costs for index hospitalization were $36964 per pt for IP SUD and $28366 for mean Medicare payments with a mean loss of $8598 per pt (median −$5616). Payments exceeded estimated costs on average by $2764–8149 for 1–4-day hospitalizations and roughly equal costs for hospitalizations at 5 days. For pts with LOS of 6–9 days and ≥10 days, payments were lower than costs by $6735 and $16659, respectively, suggesting a loss. For pts with subsequent OP administrations (74%) observable in this sample, cumulative payments and costs were assessed following the index hospitalization, mean cumulative longitudinal payments were ≥ cumulative costs within 2–3 mos. IP stay net losses were higher among pts with infection (−$6406 vs no infection), neutropenia (−$7006), and febrile neutropenia (−$10018). Payment patterns and estimated costs were similar across hospital types. Conclusions: Results suggest a large financial burden on non-PPS-exempt hospitals for IP-administered bsAb SUD. While shorter LOS for IP SUD generally did not result in financial losses, longer LOS was associated with disproportionately higher costs relative to payments. Care models (e.g. OP SUD) are key to manage initiation costs and ensure delivery of care for bsAbs remains financially sustainable.

e19503 Background: The anti-B-cell maturation antigen (BCMA) antibody-drug conjugate (ADC) belantamab mafodotin is approved in the USA and EU for relapsed/refractory multiple myeloma (RRMM). Understanding treatment options and patient outcomes following ADC failure is clinically important. This study describes post-ADC treatment patterns and clinical outcomes in real-world patients with RRMM. Methods: Adult patients with MM who received an ADC and initiated ≥1 subsequent line of therapy (LOT) were included. The index date was the start of the first post-ADC LOT. Data were obtained from chart reviews at International Myeloma Foundation International Myeloma Working Group (IMF IMWG) academic sites, and US electronic health records from largely community sites (COTA and Guardian Research Network [GRN]). Patient characteristics and index regimens were summarized descriptively. Time to next treatment (TTNT) and overall survival (OS) were estimated with the Kaplan-Meier estimator. Results: The IMF IMWG cohort (n=40) had a mean age of 70.8 years, median of 7 prior LOTs and 82.5% were triple-class refractory (TCR). Overall, 85% received ADC monotherapy (70% belantamab mafodotin) and 15% combination therapy. Pre-ADC and not considering corticosteroids, patients were commonly exposed to lenalidomide (R; 100%), bortezomib (V; 92.5%), daratumumab (D) and pomalidomide (P; 90% each). Over a median follow-up of 26 months after index date, 29 unique index post-ADC regimens were reported, frequently selinexor (27.5%) and bispecific antibodies (15%). CAR T-cell therapy was administered to 5%, with 60% re-treated with a pre-ADC drug class (PI/IMiD/anti-CD38) after ADC. Median (95% CI) TTNT and OS were 10.8 (7.0–20.6) and 19.0 (13.4–25.1) months, respectively. The COTA-GRN cohort (n=39) had a mean age of 67.5 years, median of 8 prior LOTs, and 51.3% were TCR. Overall, 56% received ADC monotherapy (belantamab mafodotin) and 44% combination therapy. Pre-ADC and not considering corticosteroids, patients were commonly exposed to D and R (97.4% each), and carfilzomib, V and P (94.9% each). Over a median follow-up of 9.2 months, 32 unique index post-ADC regimens were reported, frequently selinexor (23.1%) and venetoclax (17.9%) based; 0% received CAR Ts and 54% were re-treated with a pre-ADC drug class (PI/IMiD/anti-CD38) after ADC. Median (95% CI) TTNT and OS were 4.9 (2.8–non-estimable [NE]) and 12.0 (4.9–NE) months, respectively. Conclusions: Findings highlight that most patients with heavily pretreated BCMA-ADC exposed MM were re-treated with similar classes. Academic centers used novel therapies (ie, CAR T, bispecific antibodies) more often and their patients had longer survival than those treated at community sites. However, clinical outcomes remained sub-optimal, emphasizing the unmet need for effective, accessible post-ADC treatments.

e19521 Background: Blindedindependent central review (BICR) committees are often established for oncology trials to assessbestoverall response (BOR), while real-world (RW) studies typically rely on physician-assessed responses. To emulate clinical trial rigor, a BICR committee was implemented in the R5458-ONC-21101 RW data-derived external control arm study (NCT05673967) to evaluate BOR using International Myeloma Working Group (IMWG) criteria. A pre-specified concordance analysis compared BOR assessments between the BICR committee and treating site physicians. Methods: RW data were obtained from chart reviews at 15 participating International Myeloma Foundation IMWG sites. The BICR committee, comprised of three multiple myeloma experts, evaluated BOR through consensus voting. Per protocol, the committee reviewed case report forms consisting of data on serum and urine myeloma protein and free light chain levels; and, where available, bone marrow plasma cell percentage, presence of plasmacytomas, and bone lesion changes. Concordance between BICR- and physician-assessed BOR was evaluated for objective response rate defined as ≥partial response (PR), ≥very good partial response (VGPR), ≥complete response (CR), and stringent complete response (sCR), with non-evaluable responses excluded from the analysis. Cohen’s kappa (κ) was used to measure agreement, with values >0.6 indicating strong concordance. 1 Results: Of 279 evaluable lines of therapy from 203 patients (Table), the BOR of ≥PR was 45.2% by BICR assessment and 42.3% by treating physicians (κ=0.622). Concordance improved for BOR of ≥VGPR (22.2% by BICR vs 24.7% by treating physicians; κ=0.731) but was low for BOR of ≥CR (3.9% vs. 10.8%; κ=0.508) and sCR (1.1% vs. 4.7%; κ=0.364). Conclusions: BICR- and physician-assessed responses showed strong concordance for BOR of ≥PR and ≥VGPR. However, as expected, lower concordance for ≥CR and sCR was observed, as evaluation of CR per IMWG criteria requires a bone marrow biopsy, which is rarely performed in clinical practice. While the reliability of CR and sCR in RW data is less certain, these results suggest that BOR of ≥VGPR or ≥PR may be reliably ascertained in academic settings based on treating physician evaluations. 1. Landis JR, Koch GG. Biometrics 1977;33(1):159–74. Clinical trial information: NCT05673967 . Agreement of BICR- and physician-assessed responses. BICR assessed Physician assessed Observed agreement, % Cohen’s kappa* Number of evaluable lines of therapy 279 279 - - ≥PR, n (%) 126 (45.2) 118 (42.3) 81.4 0.622 ≥VGPR, n (%) 62 (22.2) 69 (24.7) 90.3 0.731 ≥CR, n (%) 11 (3.9) 30 (10.8) 93.2 0.508 sCR, n (%) 3 (1.1) 13 (4.7) 96.4 0.364 *A kappa value >0.6 indicates strong concordance. 1

Introduction: Oncologists increasingly recognize the need to evaluate the impact of cancer therapies on patients' time, known as “treatment-related time toxicity”, which is measured as the number of days of contact with the healthcare system (Gupta A et al. J Clin Oncol 2022). Current standard-of-care options for patients with TCE RRMM require frequent clinic visits for treatment administration. Reducing treatment-related time toxicity of treatment without compromising efficacy or safety may have an impact on patients' quality of life and influence treatment choice. BCMA-directed bispecific antibodies (BCMA bsAbs) provide a novel treatment option for TCE RRMM, with response-adapted dosing frequency allowing for extended dosing intervals for patients. The frequency of extended dosing intervals varies between BCMA bsAbs according to their prescribing information or pivotal trial protocol. The aim of this analysis was to evaluate the impact of BCMA bsAbs' extended dosing intervals on treatment-related contact (TRC) days corresponding to treatment administration as a component of time toxicity. Methods: An Excel-based longitudinal model was developed to quantify the number of TRC days experienced by patients with TCE RRMM within the healthcare system when receiving treatment with BCMA bsAbs (linvoseltamab, teclistamab, or elranatamab) over 1-2 years. TRC days included all planned treatment administration days. Model inputs were sourced from product labels or pivotal trial protocols for bsAbs, as well as the published literature. To allow for a comparison of total dosing regimens, it was assumed that patients continued receiving treatment throughout the study period with no discontinuation. Dosing intervals for each product during the first 6 months were once weekly (QW), except for linvoseltamab (QW for Weeks 1-14, then once every 2 weeks [Q2W] from Weeks 16-24, per Phase 2 trial protocol). The extended dosing interval for linvoseltamab was Q4W for patients reaching very good partial response or better at or after 24 weeks, and Q2W for both teclistamab patients who maintained a complete response (CR) or better for ≥6 months and for elranatamab patients who reached partial response or better at or after 6 months. Two switching scenarios were considered for teclistamab: an earliest possible switch (at Week 26), and a time-varying switch based on digitized time to CR data from MajesTEC-1 (Usmani SZ et al. ASCO 2023). Results were calculated to evaluate the difference in TRC days between the scenarios with and without extended dosing intervals for each treatment. Results: In the first year of treatment, the total number of TRC days with and without extended dosing intervals was lowest with linvoseltamab. TRC days with linvoseltamab were reduced from 33 to 26 days with extended dosing intervals. Next lowest was elranatamab (53 to 39 days), followed by teclistamab (54 to 41 days for earliest possible switch and 54 to 50 days with time-varying switching). Over 2 years, linvoseltamab had the lowest number of TRC days (59 to 39 days), followed by elranatamab (105 to 65 days) and teclistamab (106 to 67 days for earliest possible switch and 106 to 80 days with time-varying switching). Conclusions: Extended dosing intervals with BCMA bsAbs can substantially reduce time toxicity for patients with RRMM. Linvoseltamab had the lowest number of TRC days among BCMA bsAbs.

Introduction Multiple myeloma (MM) is considered incurable. Despite improved outcomes with novel agents, including BCMA-targeted chimeric antigen receptor (CAR) T-cell therapies, antibody-drug conjugates (ADCs), and bispecific antibodies, patients with relapsed/refractory MM (RRMM) often have poor prognoses. LINKER-MM1 (NCT03761108) is a global, single-arm, Phase 1/2 study of linvoseltamab, a BCMA×CD3 bispecific antibody, in patients with RRMM who were either triple-class exposed (TCE; previously treated with a proteasome inhibitor, immunomodulatory drug, and anti-CD38 antibody) during ≥3 prior lines of therapy (LOTs), or triple-class refractory to these therapies. Here, we present comparisons of clinical outcomes from LINKER-MM1 with those of a current, international, real-world (RW) external control arm (ECA; NCT05673967). Methods The ECA was derived from 16 academic sites of the International Myeloma Foundation International Myeloma Working Group (IMWG) (N=203; 309 eligible LOTs) and compared with linvoseltamab (N=105; Phase 2 200 mg cohort). Patients in the ECA initiated ≥1 anti-MM therapy after meeting key LINKER-MM1 eligibility criteria. Weighted random sampling and inverse probability of treatment weighting were used to select 1 LOT per patient and balance the ECA and trial populations on prespecified prognostic factors (Kumar S, et al. IMS 2023). The primary endpoint was objective response rate (ORR; IMWG criteria) determined by an independent central review committee (ICRC) based on myeloma laboratories. An independent data review committee reviewed comparability of cohorts and endpoint assessments prior to conducting comparative analyses. Results Median follow-up was 14.3 months for the linvoseltamab cohort (data cutoff: Jan 6, 2024) and 13.4 months for the ECA. After weighting, 15 prognostic factors were balanced between cohorts. Patients in the ECA received 68 distinct regimens, most commonly CAR T-cell therapies (11.3%) and ADCs (10.3%). After balancing the cohorts, patients in the ECA evaluable for response had ICRC-assessed ORR of 46.3% (40.8% by treating physician assessment), among whom 24.0% had very good partial response or better (≥VGPR). When including patients who died without evaluable response, ECA ICRC-assessed ORR was 44.2%. Linvoseltamab induced significantly higher ICRC-assessed ORR (69.5% vs 46.3%, odds ratio [OR] 2.65 [95% confidence interval (CI) 1.66-3.69]) and rate of ≥VGPR (62.9% vs 24.0%, OR 5.37 [95% CI 3.61-8.49]) compared with ECA regimens. Conclusion Despite current use of novel therapies, there is no well-established RW standard of care (SOC) for patients with TCE RRMM treated at IMWG sites. To our knowledge, this is the first RW ECA study in MM with a high percentage of anti-BCMA therapies and response ascertainment for all patients by ICRC. Linvoseltamab induced significantly higher response rates, including rate of ≥VGPR, compared with current RW SOC therapies, highlighting its potential as a highly effective treatment in patients with TCE RRMM.

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 &lt;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 &gt;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 &lt;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 &lt;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.