Aguirre, J.F.

Abstract Background: Minimal residual disease (MRD) is a critical prognostic and therapeutic response marker in multiple myeloma (MM). Two main technologies are used for MRD assessment in bone marrow: next-generation flow cytometry (NGF) and next-generation sequencing (NGS), from clonoSEQ. While both methods are FDA-cleared and clinically relevant, they differ in sensitivity, sample handling requirements, and technical differences. Comparative performance in real-world matched samples is understudied. Here we compared the detection rates and concordance between MRD by NGF (flow cytometry) and NGS-based clonoSEQ, using paired bone marrow aspirates collected at the same clinical timepoint. Methods We identified 246 paired bone marrow samples from MM patients, which were evaluated by both flow cytometry (Euroflow, typically sensitivity of 10-5) and clonoSEQ (sensitivity of up to 10-6) on the same collection date.MRD-negativity for clonoSEQ was defined as no detectable clones and below the assay's level of detection (LoD). Continuous variables (clonoSEQ and flow CPS) were analyzed using the Mann-Whitney U test. Categorical variables were assessed using chi-square tests with Yates continuity correction for 2x2. A cox proportional hazards model was used to evaluate the association between overall survival and cytogenetic abnormalities, MRD status, and other clinical covariates including age, sex, treatment type, and disease setting (newly diagnosed, relapsed/refractory). A p-value < 0.05 was considered significant. Results Out of 246 paired bone marrow samples, we identified 173 concordant samples, out of which 26 were concordant positive (clonoSEQ+/NGF+), 147 were concordant negative (clonoSEQ-/NGF-), and 73 were discordant (clonoSEQ+/NGF-). clonoSEQ detected MRD in all cases missed by NGF, including some with relatively high tumor burden, reflecting its higher sensitivity. Among discordant samples, 45 (61.6%) were following treatment of newly diagnosed MM (NDMM) and 28 (38.4%) treatment of relapsed/refractory (RRMM). Among the MRD-positive samples, the concordant group (n=26) showed a mean clonoSEQ count of 11923.5 cells per million (CPM) and a mean NGF CPM of 305.5 (p<0.01). In contrast, the 73 discordant samples had a lower mean clonoSEQ CPM of 156.1. For the 147 MRD-negative samples with concordant results, no residual disease was detected by either assay (CPM = 0 for both). When evaluating sex, race, ethnicity, chromosomal abnormalities, prior treatments to sample collection (immunomodulatory drugs, proteasome inhibitors, CD38 antibodies, CAR Ts/bispecific antibodies), and disease stage (NDMM, RRMM, untreated), patients with t(11;14) were significantly higher in the discordant group (17.9% concordant vs. 32.9% discordant; p = 0.016), while CAR T/bispecific antibody-treated patients were more likely concordant for the tests (27.2% concordant vs. 4.1% discordant; p<0.01). High-risk cytogenetics (t(4;14), t(14;16), gain 1q) were associated with worse survival (HR 6.22, 95% CI 2.02 – 19.2; HR 16.2, 95% CI 3.38-77.1; HR 4.0, 95% CI 1.28 – 12.5, respectively). Discordant MRD status did not impact survival, though only 13/246 patients were deceased (median follow-up approximately 50.6 months).Conclusion: ClonoSEQ demonstrates higher sensitivity compared to NGF for MRD detection in MM, identifying residual disease missed by NGF particularly in t(11;14) cases. Discordance did not affect survival, however, only 13 patients were deceased at the time of last follow up, suggesting longer follow up is needed.

Background Clinical biomarkers are essential for optimizing CAR T-cell therapy in multiple myeloma (MM). Clinicians can anticipate patient responses by evaluating predictive biomarkers, particularly earlier during treatment, tailoring treatments to enhance efficacy and survival outcomes. Ferritin, a general inflammation marker, appears to be a promising predictor of clinical outcome in MM patients receiving therapy with CAR T-cells. Our goal was to evaluate this and other biomarkers in this patient population. Methods We retrospectively analyzed MM-patients treated with idecabtagene vicleucel (ide-cel) and ciltacabtagene autoleucel (cilta-cel) at Mayo Clinic Arizona between September/2019 and November/2023. We evaluated the demographic characteristics, pre-infusion bone marrow samples, adverse events, mortality, and clinical response after CAR T-cell therapy infusion, and clinical laboratory data were interpreted using reference limits established by Mayo Clinic laboratories. Statistical calculations using parametric tests were performed, and survival curves were estimated using the Kaplan-Meier analysis and compared statistically using the log-rank test and Pearson's correlation. Results Forty patients with MM received CAR T cells, and 23 and 17 patients received cilta-cel and Ide-cel, respectively. The median age was 64 years [IQR 40-80], and 62.5% were male. All patients received inpatient CAR T-cell infusions; the median vein-to-vein was 54 days (IQR: 39-109), and the median length of hospital stay was ten days (IQR: 7-25). Cytokine release syndrome (CRS) was observed in 90% of patients (3% grade ≥3), while immune effector cell-associated neurotoxicity syndrome (ICANS) was observed in 23% of patients (3% grade ≥3). At day 90, the overall response rate (ORR) was 87.5%, with 21 patients (52.5%) having a complete response (CR), 9 (22.5%) with a very good partial response (VGPR), 5 (12.5%) had a partial response (PR), 1 (2.5%) had stable disease (SD), and 4 (10%) had progressive disease (PD). 35 patients was evaluated for minimal residual assessment (MRD) using flow cytometry cut-off 10-5. Of the total population eligible (PR, VGPR, and CR) for MRD evaluation, 97% were MRD negative. The median progression-free survival (PFS) was 13.5 months on ide-cel and has not been reached on cilta-cel. The mortality rate was 23.5% Ide-cel vs 8.6% with cilta-cel. In terms of PFS, we did not find any association with age, disease risk, number of previous lines of therapy, time from last treatment to CAR T-cell infusion, absolute lymphocyte counts at leukapheresis, % of plasma cells in bone marrow pre-infusion, vein-to-vein time, use of tocilizumab, or steroids for CRS/ICANS management. However, univariate analyses showed that a ferritin level <337 mcg/L at baseline pre-CAR T-cell infusion strongly correlated independently with improved PFS (median non-reached) compared with patients with ferritin levels >337 mcg/L that had a PFS of 13.50 months HR 0.2 (95% CI 0.07 - 0.83); p=0.0245. In addition, ferritin levels <337 mcg/L pre-infusion correlated with improved overall survival (OS) (median non-reached) compared with 22.23 months in patients with higher ferritin levels HR 0.2 (95% CI 0.02 - 0.53), p=0.0069. Conclusions In conclusion, our analysis shows that ferritin levels pre-CAR T-cell infusion are independent predictive biomarkers of PFS and OS in MM-patients regardless of the CAR T-cell product received. Our cohort of MM-patients treated with the two FDA-approved CAR T-cell products showed the expected PFS, OS, and adverse events. Moreover, our results showed no significant association between clinical response and age, risk stratification, number of previous therapy lines, or other evaluated factors with disease progression. Future prospective studies will help to validate these findings and explore the mechanisms associated with high ferritin levels and their potential implications in the heightened immune-activation state in patients that express high ferritin levels and their correlation with CAR T-cell efficacy.