Impact of extramedullary multiple myeloma on outcomes with idecabtagene vicleucel.

Idecabtagene vicleucel (Ide-cel) has demonstrated excellent efficacy and durable responses in patients with relapsed/refractory multiple myeloma (RRMM). However, the outcomes with ide-cel in patients with extramedullary disease (EMD) remain incompletely characterized. We included patients with RRMM treated with ide-cel between May 2021 and April 2023 across 11 US academic institutions. Visceral or soft tissue lesions non-contiguous from bone was classified as EMD. Time-to-event analyses were performed from date of ide-cel infusion. Among 351 patients, 84 (24%) had EMD prior to infusion. The median follow-up from ide-cel infusion was 18.2 months (95% CI: 17-19.3). The day 90 overall response rates (ORR) were 52% vs. 82% for the EMD and non-EMD cohorts, respectively (p < 0.001). The median progression-free survival (PFS) was 5.3 months (95% CI: 4.1-6.9) for the EMD cohort vs. 11.1 months (95% CI: 9.2-12.6; p < 0.0001) for the non-EMD cohort. In a multivariable analysis, EMD was an independent predictor of inferior PFS [hazard ratio 1.5 (1.1-2.2), p = 0.02]. The median overall survival was 14.8 months [95% CI: 9-Not reached (NR)] vs. 26.9 months (26.3 vs. NR, p = 0.006) for the EMD and non-EMD cohorts, respectively. Extramedullary disease represents an independent predictor of inferior day 90 ORR and PFS among patients treated with ide-cel.

Absolute lymphocyte count after BCMA CAR-T therapy is a predictor of response and outcomes in relapsed multiple myeloma.

ABSTRACT: B-cell maturation antigen (BCMA)-targeting chimeric antigen receptor T cells (CAR-Ts) used in multiple myeloma (MM) are rapidly becoming a mainstay in the treatment of relapsed/refractory (R/R) disease, and CAR-T expansion after infusion has been shown to inform depth and duration of response (DoR), but measuring this process remains investigational. This multicenter study describes the kinetics and prognostic impact of absolute lymphocyte count (ALC) in the first 15 days after CAR-T infusion in 156 patients with relapsed MM treated with the BCMA-targeting agents ciltacabtagene autoleucel and idecabtagene vicleucel. Patients with higher maximum ALC (ALCmax) had better depth of response, progression-free survival (PFS), and DoR. Patients with ALCmax >1.0 × 103/µL had a superior PFS (30.5 months vs 6 months; P < .001) compared with those with ≤1.0 × 103/µL, whereas patients with ALCmax ≤0.5 × 103/µL represent a high-risk group with early disease progression and short PFS (hazard ratio, 3.4; 95% confidence interval, 2-5.8; P < .001). In multivariate analysis, ALCmax >1.0 × 103/µL and nonparaskeletal extramedullary disease were the only independent predictors of PFS and DoR after accounting for international staging systemic staging, age, CAR-T product, high-risk cytogenetics, and the number of previous lines. Moreover, our flow cytometry data suggest that ALC is a surrogate for BCMA CAR-T expansion and can be used as an accessible prognostic marker. We report, to our knowledge, for the first time the association of ALC after BCMA CAR-T infusion with clinical outcomes and its utility in predicting response in patients with R/R MM.