de, Rocío Montes

Abstract Introduction: Cilta-cel is approved in the US and the EU for the treatment of patients (pts) with lenalidomide-refractory multiple myeloma (MM) after ≥1 prior line of therapy (pLOT), including a proteasome inhibitor and an immunomodulatory agent based on the CARTITUDE-1 (CART-1, NCT03548207) and CARTITUDE-4 (CART-4, NCT04181827) studies. Cilta-cel led to deep and durable responses and significant survival benefit in pts with relapsed/refractory MM (RRMM) after ≥3 pLOT in CART-1. In CART-4, cilta-cel led to a significant overall survival benefit with a higher proportion of pts achieving deep, sustained minimal residual disease negativity vs standard of care in pts with lenalidomide-refractory MM after 1–3 pLOT. We investigated the mechanism of action of cilta-cel by correlating biomarkers from peripheral blood and the bone marrow TME with progression-free survival (PFS) and number of pLOT in pts with RRMM from CART-1 and CART-4. Methods: Biomarker analyses were performed using peripheral blood and bone marrow aspirates (BMAs) collected in both CART-1 and CART-4 studies. Immunophenotyping by flow cytometry was performed using peripheral blood at baseline/time of apheresis in samples from both studies. Immune fitness at baseline was assessed in pts by pLOT and in association with PFS. Gene set enrichment scores were derived from RNA sequencing data of the TME using BMAs. Mixed-effects models were used to identify signatures/pathways modulated over time (day [D] 28 and at 6 months [mo] post infusion vs screening) and in association with PFS and pLOT. Results: In total, 176 CART-4 and 97 CART-1 pts received cilta-cel as study treatment. Immunophenotyping data were available from 248 peripheral blood samples (1 pLOT, n=56; 2 pLOT, n=61; ≥3 pLOT, n=131). At apheresis, CD4+ naïve T cells (%) were higher in pts with 1 or 2 pLOT, compared with those with ≥3 pLOT, while no difference was found in pts with ≥3 pLOT with further breakdown (i.e., 3–4 vs 5–6 vs ≥7 pLOT). Further, higher baseline levels of CD4+ naïve T cells were associated with longer PFS. These data suggest that the negative impact on peripheral immune fitness with the addition of LOT may plateau when pts have received ≥3 pLOT. TME gene expression data were available from 148 BMA samples (screening, n=50; D28, n=50; 6 mo, n=48) from CART-4. Analyses of gene expression signatures suggest depletion of B cells and antibodies at D28 post cilta-cel infusion, with partial recovery at 6 mo. This was corroborated in parallel by flow cytometry and immunoglobulin quantification. Further, elevated expression of genes associated with myeloid cells, including tumor-associated macrophages (TAM, likely M1), and of genes associated with cytotoxic T cells were also observed at D28. Elevated expression of genes associated with B-cell receptors, T-cell differentiation and activation, and cytokine signaling pathways were found at both D28 and 6 mo. Pts with longer PFS (>18 mo) had higher levels of M1 TAM at D28, while those with shorter PFS had higher levels of regulatory T cells and more suppressed interferon pathway genes at 6 mo, suggesting that relapse may be associated with a more suppressive immune response. In pts with fewer pLOT, more profound B-cell depletion on D28, better recovery at 6 mo, and elevated B-cell receptor signaling were inferred from gene expression data. Pts with 1 pLOT also demonstrated higher elevation of M1 TAM expression on D28 from screening as compared with pts with 3 pLOT, similar to what was observed in pts with longer PFS. Conclusions: Correlative biomarker data suggest that longer PFS is associated with better immune fitness at baseline and stronger immune responses post cilta-cel infusion, as observed in peripheral blood and within the TME of pts with RRMM in CART-1 and CART-4. The peripheral immune fitness was more pronounced in pts with 1 and 2 pLOT vs 3 pLOT and beyond, where deterioration plateaued. This suggests the impact of T-cell immune fitness on PFS may be limited beyond the third LOT. Importantly, other covariates, including factors within the immune TME and tumor burden, may play a significant role in balancing this compromised intrinsic T-cell immune fitness at apheresis, thereby contributing to PFS durability after 3 pLOT. Overall, these results support increased benefits in treating pts with MM with cilta-cel in earlier LOTs.

CARTITUDE-1 evaluated ciltacabtagene autoleucel (cilta-cel) in patients with heavily pretreated relapsed/refractory multiple myeloma (RRMM). We describe overall survival (OS), ≥5-year progression-free outcomes, associated biomarkers, and safety, with a median study follow-up of 61.3 months. For the 97 treated patients, median OS was 60.7 months (95% CI, 41.9 to not estimable). One third (32/97) of patients remain alive and progression-free for ≥5 years after a single cilta-cel infusion, without maintenance treatment. Twelve of these patients treated at a single center underwent serial minimal residual disease (MRD) and positron emission tomography-computed tomography assessments, and all (100%) were MRD-negative (at least 10 −5 threshold) and imaging-negative at year 5 or later after cilta-cel. Baseline characteristics, including the presence of high-risk cytogenetics and extramedullary disease, were generally comparable for the 32 patients who were progression-free for ≥5 years versus patients who had progressive disease by year 5. A trend of lower baseline tumor burden, higher fraction of naïve T-cells in the cilta-cel drug product, higher T cell-to-neutrophil ratio, higher hemoglobin and platelets at baseline, and higher effector-to-target ratio were associated with ≥5-year progression-free status. The safety profile of cilta-cel remained consistent with previous reports. To our knowledge, our data provide the first evidence that cilta-cel is potentially curative in patients with RRMM.

7507 Background: CARTITUDE-1 evaluated cilta-cel in pts with heavily pretreated RRMM who historically have an expected median progression-free survival (PFS) of <6 months (mo) and median overall survival (OS) of ~1 year (y). At 33.4 mo median follow-up, median PFS was 34.9 mo, and median OS was not reached (36-mo OS rate, 62.9%; Lin et al, ASCO 2023). We report OS, ≥5 y progression-free outcomes, and safety with a median study follow-up of 60.3 mo. Methods: Pts in CARTITUDE-1 received a single cilta-cel infusion. Correlative analyses were performed utilizing drug product, baseline, and postinfusion samples. Pts are followed for progression, survival, and safety in a 15-y follow-up study, CARTinue (NCT05201781), with pt evaluations per local standard of care (reported annually at a minimum). Results: Of 97 pts treated, 32 (33.0%) remain alive and progression free for ≥5 y after cilta-cel, without further MM treatment. For these 32 pts, prior to enrollment in CARTITUDE-1, median time from start of last line of therapy (LOT) to progression was 4.0 mo (range, 0.7–48.6). Among the 32, median age was 60 y (range, 43–78), median number of prior LOT was 6.5 (range, 3–14), 23.3% had high risk cytogenetics, 12.5% had extramedullary disease (EMD), 90.6% were triple-class refractory, and 46.9% were penta-drug refractory. Baseline characteristics of pts who were progression free for ≥5 y, including those with high-risk cytogenetics and EMD, were comparable to pts with progressive disease (PD) within 5 y. Compared with pts who had PD within 5 y, biomarkers significantly associated with ≥5 y progression free status included a higher fraction of naïve T cells in the drug product, lower neutrophil to T cell ratio, higher hemoglobin and platelets at baseline, and higher effector-to-target ratio (Cmax to sBCMA at baseline). At Cmax, these pts also had significantly higher CD4 central memory CAR+ T cell subsets and CAR+ T cells that were positive for the activation markers CD38, CD25, and PD-1. Data were collected on a subset of pts from a single center where local serial MRD assessments were performed. All 12 pts at this center who were progression free for ≥5 y were MRD negative at 10 –6 and imaging negative by PET/CT yearly for 5 y. Overall, at 60.3 mo median follow-up in CARTITUDE-1 (N=97), median OS was 60.6 mo (95% CI, 41.9–NE). With continued follow-up, 3 additional pts reported a second primary malignancy (1 of which was acute myeloid leukemia; onset, 2.8 y after infusion). No new cases of movement and neurocognitive disorders were reported. Conclusions: The median OS for pts enrolled in CARTITUDE-1 was 5 y, and 33% of pts remain progression free for ≥5 y following a single cilta-cel infusion. These data provide the first evidence that cilta-cel is potentially curative in pts with RRMM. Clinical trial information: NCT03548207 , NCT05201781 .

Ciltacabtagene autoleucel (cilta-cel) consists of autologous T cells genetically modified to express a two-binding domain chimeric antigen receptor (CAR). The target antigen of the CAR is B-cell maturation antigen (BCMA), which is highly expressed on malignant plasma cells (PC) from multiple myeloma subjects. In the Phase 1b/2 CARTITUDE-1 study, cilta-cel led to early, deep, and durable responses and was approved for the treatment of patients with relapsed or refractory multiple myeloma (RRMM) after four or more prior lines of therapy by FDA. Despite cilta-cel's outstanding overall response rate (97.9%) and duration of response (DOR) in RRMM patients, relapse still occurs. Biomarkers associated with this durable response and acquired resistance remain to be elucidated. We present updated correlative data from the CARTITUDE-1 study. At the ~3 year follow-up (October 2022 data cutoff), 97 patients had received a single infusion of cilta-cel (median 0.71 x10 6 cells/kg [range 0.52 x10 6-0.94 x10 6]); the median follow up was 33.4 months (range 1.5-45.2), median DOR was 33.9 months (95% CI, 25.5-not estimable [NE]) and median PFS was 34.9 months (95% CI, 25.2-NE) (Lin Y et al, ASCO 2023). Drug product (DP), baseline and on-treatment whole blood and bone marrow samples from enrolled patients were analyzed by methods including flow cytometry, MSD immunoassays, Cellular Indexing of Transcriptomes and Epitopes by Sequencing (CITE-seq) and TCR sequencing. In CARTITUDE-1, the DP contained a mixture of transduced and non-transduced T cells; the median transduction efficiency was 16% (range 5-32%), with a balanced distribution of CAR+CD4+ and CAR+CD8+ cells, median frequency 12% (range 2-28%) and 6% (range 2-20%), respectively. Further, the DP T cell subset composition was variable but balanced between central (Tcm) and effector memory (Tem) phenotypes. CAR+ T cells expanded reaching a median peak concentration (C max of 730 cells/µL; range 3-13805 cells/µL) in blood between days 12-14 post-infusion and persisted in circulation for a median of 100 days (range 20-912 days). High efficacy (best response) and DOR were achieved despite variable CAR-T cell expansion and lack of detectable CAR-T cell persistence over time. At C max, the CD4:CD8 ratio (based on % of CAR+ cells) was 0.29, demonstrating a CAR+CD8+ T cell preferential expansion, and both CAR+CD4+ and CAR+CD8+ T cells were predominantly of a Tcm phenotype, median 95% (range 62-99.5%) and 96% (range 33-99.7%), respectively. Higher frequency of early-memory T cell phenotypes has been associated with clinical responses to CAR-T therapies in MM (Dancy et al., Blood 2018). CITE-seq analyses showed that DP characteristics such as a high CD8+ stem-like phenotype and a low CD4+ Treg-like phenotype in the CAR+ T cell compartment associated with longer DOR. Some of the most abundant clones in the DP single cell TCR data were CAR+CD8+ T cells expressing granzyme B, suggesting high cytotoxic potential. Additional bulk TCR sequencing data suggest both diversity and individual clonal expansion longitudinally after cilta-cel infusion. We also evaluated tumor and patient intrinsic characteristics at baseline. BCMA expression on bone marrow PC was prevalent and highly variable among RRMM patients; however, expression did not associate with best response or DOR. Further, high ORR was observed in patients with high-risk cytogenetics, high tumor burden (&gt;= 60% bone marrow PC), or baseline plasmacytomas, although with a non-statistically significant shorter PFS. Sustained MRD negativity strongly associated with longer DOR. Conversely, patient-intrinsic characteristics associated with inflammation (CRP, ferritin, neutrophils, pro-inflammatory cytokines) correlated with shorter DOR. Treatment benefit of the magnitude seen with cilta-cel had not been reported with any other approved therapy in this setting. Correlative analyses suggest an emerging profile to help understand such outstanding clinical activity: a balanced CD4/CD8 ratio and Tcm/Tem phenotype of the manufactured DP and preferential expansion of CAR+CD8+ Tcm cells. Further, certain baseline patient-intrinsic and tumor characteristics may explain the longer DOR in the RRMM setting. These investigations help identify markers of response to cilta-cel and may lead to CAR-T cell design or manufacturing strategies that enhance drug product characteristics and thus clinical efficacy.

AbstractThe development of novel agents has transformed the treatment paradigm for multiple myeloma, with minimal residual disease (MRD) negativity now achievable across the entire disease spectrum. Bone marrow–based technologies to assess MRD, including approaches using next-generation flow and next-generation sequencing, have provided real-time clinical tools for the sensitive detection and monitoring of MRD in patients with multiple myeloma. Complementary liquid biopsy–based assays are now quickly progressing with some, such as mass spectrometry methods, being very close to clinical use, while others utilizing nucleic acid–based technologies are still developing and will prove important to further our understanding of the biology of MRD. On the regulatory front, multiple retrospective individual patient and clinical trial level meta-analyses have already shown and will continue to assess the potential of MRD as a surrogate for patient outcome. Given all this progress, it is not surprising that a number of clinicians are now considering using MRD to inform real-world clinical care of patients across the spectrum from smoldering myeloma to relapsed refractory multiple myeloma, with each disease setting presenting key challenges and questions that will need to be addressed through clinical trials. The pace of advances in targeted and immune therapies in multiple myeloma is unprecedented, and novel MRD-driven biomarker strategies are essential to accelerate innovative clinical trials leading to regulatory approval of novel treatments and continued improvement in patient outcomes.