Sun, Huabin

7533 Background: Ciltacabtagene autoleucel (cilta-cel) shows benefit for patients (pts) with relapsed/refractory multiple myeloma (RRMM). A recently recognized uncommon adverse reaction, IEC-EC is characterized by severe/persistent diarrhea typically 1–3 months post CAR-T cell infusion. Here we summarize incidence and features of IEC-EC in clinical trials of cilta-cel for RRMM. Methods: 483 pts across RRMM studies (CARTITUDE-1, -2, -4, and CARTIFAN-1) were evaluated for evidence of IEC-EC. The clinical picture and nomenclature for IEC-EC were described in the real-world setting after infusion of most pts. As such, retrospective analysis was performed to identify cases consistent with IEC-EC, defined as prolonged (≥3 weeks) and severe (≥grade 3) diarrhea after cilta-cel infusion, without clear infectious etiology. Correlative biomarker analyses included peripheral CAR-T cell expansion/persistence, immune cell composition, and cytokines/inflammatory markers. Centralized pathomorphological review and immunohistochemical analysis of available biopsies was conducted. Results: Across RRMM studies, 6/483 (1.2%) pts demonstrated the clinical picture of IEC-EC, presenting 12–214 days after receiving cilta-cel (median onset 67 days post infusion). Best response was CR/sCR for all subjects. Pts received therapies including steroids (4/6). Four pts experienced symptom resolution within 123–227 days; 2 had persistent symptoms until death (causes: multiorgan failure and COVID19). Pts with IEC-EC had lower levels of B cells and higher levels of CAR+ T cells and inflammatory cytokines (eg, IL-6) at onset compared to a GI symptom-free control group at comparable time; while all cilta-cel–treated pts experienced B cell depletion, pts with IEC-EC had more prolonged deficiency. Histological analyses of GI biopsies from 5 pts with IEC-EC revealed plasma cells, normally present in the GI tract, were absent. CAR-T cells were detected and localized to the lamina propria and were not observed juxtaposed with epithelia, making it unlikely direct damage to epithelia was caused by CAR-T cells. Histologic damage was greater in the small intestine (predominantly duodenum) than the colon. Conclusions: Retrospective analysis of cilta-cel trials identified a low IEC-EC incidence (1.2%). Findings support a reactive mechanism involving plasma cell depletion and immune dysregulation rather than direct CAR-T cell cytotoxicity and highlight the importance of upper endoscopy to identify injury patterns in the small intestine that may be less pronounced in the colon. Although the pathophysiology is not fully defined, increased awareness and earlier diagnosis may improve understanding of management and enhance likelihood of IEC-EC reversibility.

Abstract Introduction: The CARTITUDE-4 study (NCT04181827), which enrolled patients with lenalidomide-refractory multiple myeloma (MM) after 1–3 prior lines of therapy (pLOT), demonstrated a significant benefit of ciltacabtagene autoleucel (cilta-cel) over established triplet regimens. However, the benefit of cilta-cel for patients with standard-risk cytogenetics remains less defined. Here, we report outcomes in patients with standard-risk cytogenetics from the intent-to-treat and as-treated populations in CARTITUDE-4. Methods: InCARTITUDE-4, patients randomized to the cilta-cel arm underwent apheresis and bridging treatment with either pomalidomide, bortezomib, and dexamethasone (PVd) or daratumumab, pomalidomide, and dexamethasone (DPd), followed by lymphodepletion therapy with cyclophosphamide and fludarabine, and then a single cilta-cel infusion. Progression-free survival (PFS) was assessed using a validated computerized algorithm. The intent-to-treat population included 208 patients; 32 patients progressed or died on bridging therapy, resulting in an as-treated population of 176 patients. Patients with high-risk cytogenetics, defined as del(17p), t(14;16), t(4;14), gain/amp(1q) (n=105), or with unknown cytogenetics (n=12), were excluded from the as-treated analysis. The 12-month minimal residual disease (MRD)-negative complete response (CR) was defined per the International Myeloma Working Group criteria as the proportion of participants with CR or better prior to and at 12 months (±3 months), achieving MRD-negative status at 12 months (+3 months) after cilta-cel infusion, as determined by next-generation sequencing (10-5), prior to progressive disease or subsequent anti-myeloma therapy. For the as-treated population, PFS rates were measured from the time of cilta-cel infusion. Results: In CARTITUDE-4, in the intent-to-treat population, at a median follow-up of 33.6 months, patients with standard-risk cytogenetics had a 30-month PFS rate (95% CI) of 71.0% (58.8–80.2) in the cilta-cel arm (N=69) vs 43.2% (31.3–54.5) in the standard-of-care (SOC) arm (N=70). Patients with standard-risk cytogenetics in the as-treated population (n=59) had a 30-month PFS rate of 80.5% (95% CI, 67.2–88.8). In CARTITUDE-1 (NCT03548207), which evaluated cilta-cel in patients with heavily pretreated relapsed/refractory MM (RRMM; ≥3 pLOT), the 30-month PFS rate among patients with standard-risk cytogenetics (negative for del(17p), t(14;16), or t(4;14); n=68) was 59.9% (95% CI, 47.2–70.5). In the CARTITUDE-4 as-treated population with standard-risk cytogenetics, 8 PFS events occurred within 1 year and 4 PFS events beyond 1 year of cilta-cel infusion. Twenty-six patients achieved MRD-negative CR at 12 months after cilta-cel; 100.0% of these patients were progression free at 30 months. Fourteen patients were not evaluable for MRD due to: calibration failure (n=12), no sample availability for testing (n=1), or indeterminate results post baseline (n=1). Conclusions: The PFS rate at 2.5 years for patients with standard-risk RRMM was higher in CARTITUDE-4 compared with CARTITUDE-1, supporting the use of cilta-cel as early as second line in the treatment course. In CARTITUDE-4 (as-treated population), 80.0% of patients with standard-risk cytogenetics were progression free and off treatment at 2.5 years. In patients with standard-risk disease who achieved MRD-negative CR at 1 year, this rate increased to 100.0%. The low rate of progression events in cilta-cel-treated patients with standard-risk cytogenetics shows the profound benefit of a single cilta-cel infusion in this population.

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 .