Graft-versus-host disease (GVHD) has been a significant barrier to successful myeloablative conditioning (MAC) allogeneic hematopoietic cell transplantation (HCT). Traditional GVHD prophylaxis with a calcineurin inhibitor and methotrexate (TAC/MTX) is associated with substantial GVHD. Controversy exists over whether post-transplantation cyclophosphamide (PTCy) should replace TAC/MTX as the standard of care for MAC HCT using HLA-matched donors. We conducted a retrospective cohort study of 237 adult patients with acute myeloid leukemia (AML; n = 164) or acute lymphoblastic leukemia (ALL; n = 73) who underwent MAC followed by HLA-matched HCT at our center between 2018 and 2025. Patients were evaluated based on GVHD prophylaxis received: PTCy/TAC/mycophenolate mofetil (MMF) or TAC/MTX. Kaplan-Meier and competing-risks methods were applied, with outcomes further stratified by pre-HCT measurable residual disease (MRD). Of the 237 patients, 46 received PTCy/TAC/MMF and 191 received TAC/MTX. Baseline characteristics, remission status, and pre-HCT MRD were comparable in the 2 groups. One-year chronic GVHD-free survival was significantly superior with PTCy compared to TAC/MTX (86.3% versus 61.7%; P = .006), attributed to significantly lower moderate to severe chronic GVHD at 1 year (7% versus 21%; P = .02) and significantly lower NRM at 1 year (2.2% versus 10.5%; P = .04) with PTCy. Overall survival (OS) and progression-free survival (PFS) were similar in the PTCy and TAC/MTX groups (OS: 93.3% versus 82.1%, P = .2; PFS: 70.2% versus 74.8%, P = .6). One-year GVHD-free, relapse-free survival (GRFS) trended higher in the PTCy group (63.5% versus 50.2%; P = .09). We then evaluated the outcomes in the 2 groups stratified by pre-HCT MRD status (PTCy: MRD+ 35% [n = 16]; MRD-, 63% [n = 29]; unknown, 2% [n = 1]; TAC/MTX: MRD+, 34% [n = 65]; MRD-, 50% [n = 96]; unknown, 16% [n = 30]). Similar trends toward superior rates of GVHD, NRM, and GRFS were observed following PTCy in both the MRD+ and MRD- cohorts. The cumulative incidence of relapse at 1 year did not differ between PTCy and TAC/MTX among MRD- patients (14.1% versus 9%; P = .41); however, we observed a strikingly high incidence of relapse among MRD+ patients treated with PTCy relative to TAC/MTX (51.9% versus 23.3%; P = .06). In this single-center analysis, PTCy-based GVHD prophylaxis demonstrated superior chronic GVHD-free survival, significantly reduced NRM, and a trend toward higher GRFS compared with TAC/MTX in MAC HLA-matched HCT for acute leukemia. However, a suggestion of increased relapse, particularly among patients with detectable MRD before HCT, warrants further investigation. Integrating enhanced antileukemic strategies with PTCy platforms may optimize long-term outcomes. © 2026 American Society for Blood and Marrow Transplantation. Published by Elsevier Inc. All rights reserved.

Background High-risk (HR) B-cell acute lymphoblastic leukemia (B-ALL) remains difficult to cure in adults despite autologous CAR T cells or allogeneic hematopoietic cell transplant (HCT). Building on preclinical work showing CAR T cell safety post-HCT (Ghosh A, Smith M Nature Medicine 2017), we tested whether allogeneic CAR-T cells combined with myeloablative graft-engineered HCT (Orca-T) could enhance antileukemic activity without increasing GVHD or graft failure. We now report final clinical outcomes from this Phase 1 trial (NCT05507827). Methods This single-center trial tested allogeneic anti-CD19/CD22 CAR T cells combined with myeloablative conditioning and Orca-T (D0 HSPCs/Tregs; D+2 Tcons, per Meyer Blood 2025) in adults with HR B-ALL. Donor-derived CAR T cells were administered on D+2, tacrolimus began on D+3. The primary endpoint was engraftment without grade 3+ acute GVHD at D+42; secondary endpoints included survival outcomes, CAR persistence, and immune reconstitution. Results Eighteen patients (pts) enrolled between Sept 2022 and May 2025; 16 received both Orca-T and allogeneic CAR T cells; 1 received only Orca-T due to active infection at time of planned CAR T infusion and 1 did not proceed on trial. Median age was 31 years (range, 21–58); 70% were Hispanic, 76% were MRD+ post-induction. Most (76%) received matched sibling grafts; 24% were from matched unrelated donors. All pts have now reached the primary endpoint: engraftment occurred in 100% and no pts have developed 3+ acute GVHD. Acute GVHD occurred in 1 pt (grade 1) and chronic GVHD in 2 pts (1 mild; 1 moderate). There were no high-grade CAR mediated toxicities.With median follow-up of 14 months (range, 3-35), disease-free and overall survival are both 100% (Figure 1A, 1B). Figure 1C depicts pre-and post-treatment MRD. Following allogeneic CAR T plus Orca-T, all pts achieved MRD clearance by flow cytometry (10-4) and remain undetectable to date. Two pts with pre-treatment MRD have ongoing detectable MRD by clonoSEQ (10-6) without evidence of relapse. Median time to peak CAR expansion was 13 days. Median circulating CAR T cells at peak expansion was 1,205 copies/100ng DNA, with a median D0-28 AUC of 13,324 copies/100ng DNA. Figure 2 shows ongoing CAR detection by qPCR (LOD 10 copies/100ng DNA) averaged across patients; only 4 pts have evidence of functional B cell recovery. Conclusion Here, we report final safety and anti-tumor activity of the combination of allogeneic anti-CD19/CD22 CAR T cells with a myeloablative graft-engineered HCT in pts with HR B-ALL. This paradigm-shifting combination of CAR T and HCT resulted in 100% DFS without graft failure, significant GVHD, or severe CAR-mediated toxicity. We hypothesize this is due to tolerance for CAR molecules, resulting in persistent CAR expression and improved antitumor activity. Our all-in-one allo-CAR-HCT represents a rational approach that warrants additional study.

Background Transplant-associated thrombotic microangiopathy (TA-TMA) is a potentially severe complication following allogeneic stem cell transplant with a multifactorial etiology. In clinical practice, tacrolimus (Tac) may be replaced with sirolimus (Siro) for graft-versus-host disease (GVHD) prophylaxis in patients with TA-TMA, but evidence supporting the safety and efficacy of this practice are limited. Methods We conducted a single-center retrospective review of patients who transitioned from Tac to Siro for presumed TA-TMA between 1/2022 – 4/2025. TA-TMA was assessed and risk stratified using Harmonizing Definitions criteria (Schoettler et al) prior to and 2, 4, and 8 weeks following the transition from Tac to Siro. Results This study included 21 consecutive patients. Most (62%) received reduced intensity conditioning and 48% received matched unrelated donor grafts. GVHD prophylaxis included post-transplant cyclophosphamide (PTCy)/Tac/Mycophenolate mofetil (MMF) (43%), Tac/methotrexate (33%), and Tac/MMF (24%).The median time from transplant to TA-TMA development was 37 days (range 22–47). Eighteen patients (86%) met criteria for high-risk TA-TMA, most commonly due to TMA-attributed organ dysfunction (73%) or elevated LDH (59%). Patients received Tac for a median of 31 days (range 10–260) prior to Siro transition. The median maximum Tac level was 12 mg/dL (range 7–19), occurring a median of 9 days prior to Siro transition.Following transition to Siro, 15 (71%) patients developed resolution of TA-TMA, defined as no longer meeting Harmonizing Definitions criteria. The median time to TA-TMA resolution was 21 days (range 10 -58). At 8 weeks post-Siro transition, the most common TMA features to resolve were refractory hypertension (71% reduction in the number of patients meeting criteria), anemia (70%), thrombocytopenia (52%), and elevated urine protein to creatine ratio (42%). Nine patients (22%) received at least one dose of eculizumab (range 1 – 18 doses). Notably, 11 patients achieved TA-TMA resolution without eculizumab treatment.The incidence of any acute GVHD was 29%. Three patients developed grade IV aGVHD, two of which occurred prior to Siro conversion and all in non-PTCy regimens. The 1-year cumulative incidence of any and moderate-severe chronic GVHD was 38% and 19%, respectively. The 1-year cumulative incidence of non-relapse mortality was 38% and 1-year overall survival was 57%. Cause of death included aGVHD (25%), sepsis (25%), and multiorgan failure (50%). Conclusions In patients with TA-TMA, transitioning from Tac to Siro may represent a cost-effective strategy for at least partial TA-TMA resolution without a significant increase in severe GVHD. Interpretation of these outcomes are limited by incomplete assessment of TA-TMA biomarkers across timepoints. These finding warrant study in larger cohorts with comparison against Tac continuation.

Abstract Introduction: Brexucabtagene autoleucel (BA) is an effective chimeric antigen receptor T cell (CAR-T) therapy for B cell acute lymphoblastic leukemia (ALL); however, it causes high-grade immune toxicities. Preclinical models show that short dasatinib (D) pulses given after CAR-T transiently disrupt CAR signaling, promoting a reversible “rest” state that improves T cell function. We hypothesized that D given soon after BA in vivo could induce transient rest during rapid expansion, thereby mitigating toxicities while preserving efficacy. We therefore designed a trial to evaluate safety and feasibility of D pulses after BA in relapsed/refractory (r/r) ALL patients (pts). Methods: Adult r/r ALL pts meeting treatment criteria for BA were eligible for this open-label Phase 1b trial at Stanford University (BA+D group). After BA infusion, D 100mg daily was started between Day +4 to +10 and continued on a 3 days on/4 days off pulse schedule during month 1. Primary endpoints were feasibility (≥ 2 D pulses in month 1) and safety. Clinical outcomes were compared to a cohort of 11 Stanford pts who received BA for r/r ALL from 2022-2024 (BA-only group). Results: Eleven pts were enrolled; 4 withdrew prior to receiving BA; 7 were evaluable and received BA+D. At time of BA infusion, pt median age was 44 (range 35-56), median prior lines of therapy was 2 (1-3), 4 pts (57%) had morphologic disease, and 3 (43%) had measurable residual disease (MRD). D pulses began at median Day +5 after BA (range 4-13). Feasibility was met as 6/7 pts (86%) completed ≥ 2 D pulses following BA. D was well-tolerated without excess toxicity.For BA+D vs BA-only, respectively, rates of cytokine release syndrome [CRS, all grade (AG): 100% vs 73%; G3+: 0% vs 0%], were similar; rates of immune effector cell-associated (IEC) neurotoxicity syndrome (ICANS, AG: 29% vs 55%; G3+: 29% vs 36%), and IEC hemophagocytic syndrome (IECHS, AG: 29% vs 36%; G3+: 0% vs 18%) were numerically lower. Rates of complete remission (CR, 85% vs 73%), MRD-negative CR (57% vs 45%), 1-year relapse-free survival (57% vs 44%) and 1-year overall survival (85% vs 73%) were similar. Pts in BA+D who had immune toxicity trended towards lower total steroid exposure relative to similar pts in BA-only (median 2 vs 6 days). For BA+D, CAR-T expansion was assessed by flow assisted cell sorting. 5/7 pts (71%) had CAR-T cells that expanded despite D pulses, but with lower median peak (34 CAR-Ts/uL) than reported with BA-only. All 5 pts with CAR expansion had detectable circulating CAR-T at D+28. Further comparative correlative data will be presented at AACR. Conclusion: This direct translation of preclinical work shows that 3-day pulses of D after BA are feasible and safe. While we could not clearly determine if D pulses reduced CAR-T toxicity in this small cohort, BA does expand in the setting of D. Citation Format: Nikeshan Jeyakumar, Parveen Shiraz, Evan Weber, Alyssa Kanegai, Caroline Wagner, Arvind Ramakrishnan, Bita Sahaf, Matthew Frank, Saurabh Dahiya, Melody Smith, Surbhi Sidana, Crystal Mackall, David Miklos, Lori Muffly. Brexu-cel + dasatinib: Safety and feasibility of dasatinib pulses after brexucabtagene autoleucel to modulate CAR T cell activity in relapsed/refractory B cell acute lymphoblastic leukemia [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(8_Suppl):Abstract nr CT190.

Introduction Obecabtagene autoleucel (obe-cel) and brexucabtagene autoleucel (brexu-cel) are CD19 targeted chimeric antigen receptor T cell (CAR-T) therapies, approved for adults with relapsed/refractory (r/r) B-cell acute lymphoblastic leukemia (ALL). Mechanistic differences between obe-cel and brexu-cel including differing costimulatory domains (4-1BB vs. CD28), CD19 binding domains (intermediate vs. high affinity) and split dose (Days 1 and 10) vs. single infusion may impact in-vivo cellular kinetics that translate into variant clinical outcomes. Real-world utilization and outcomes with obe-cel are unknown given the relatively recent approval. Methods The ROCCA database, comprising real world data from patients (pts) with r/r ALL treated at 40 North American institutions was used in this analysis. Pts with r/r ALL were eligible if they were apheresed for obe-cel since its approval (11/8/2024) or brexu-cel over a comparable period (since 8/1/24) and had at least 30 days of follow up. Data cut off was 7/15/2025. CRS/ICANS were graded per ASTCT criteria. Measurable residual disease (MRD) was assessed by flow cytometry and/or next generation sequencing per institutional standards. Results 38 pts have undergone apheresis for obe-cel (36 infused, all received both infusions) and 54 (53 infused) for brexu-cel over the study period. Baseline characteristics are shown in Table 1.CAR-mediated toxicity differed significantly between the cohorts (Table 2). CRS occurred in 56% of obe-cel pts compared to 94% of brexu-cel pts (p < 0.0001). There were no Gr3+ CRS events among the obe-cel pts; 3 (6%) brexu-cel pts had Gr3+ CRS (p = 0.27). ICANS occurred in 17% of obe-cel pts vs. 51% of brexu-cel pts (p = 0.001). Gr3+ ICANS occurred in 6% of obe-cel vs. 32% of brexu-cel pts (p = 0.0027). Among the obe-cel pts, CRS occurred in 31% after the first infusion and 46% after the second; ICANS occurred in 3% after the first infusion and 15% after the second. Prolonged Gr4 neutropenia (ANC < 500 cells/uL beyond day 30 from infusion) occurred in 24% of obe-cel vs. 28% of brexu-cel pts (p = 0.73). Deaths within the first 28 days of infusion occurred in 0 obe-cel pts and 4 brexu-cel pts (2 of infection, 1 of infection/brain bleed, and 1 of liver failure in the setting of Gr4 CRS and HLH).Response rates were high and did not significantly differ between cohorts (p = 0.85) (Table 3). 81% of obe-cel pts vs. 80% of brexu-cel pts achieved an MRD- CR/CRi. Conclusion Pts selected for obe-cel apheresis were similar to those for brexu-cel over the study period (noting that not all centers had access to obe-cel during this time). Similar to clinical trial results, obe-cel was associated with lower rates of CRS/ICANS. Rates of MRD-negative CR were high and did not differ between cohorts. A larger sample and longer follow up are required for further analyses; we anticipate a cohort of ∼75 obe-cel treated pts by the annual meeting and will provide updated data.

More than half of patients with relapsed/refractory large B-cell lymphoma experience disease progression after CD19-directed chimeric antigen receptor (CAR19) T-cell therapy. We investigated CAR22 therapy in 38 patients with CAR19-refractory disease, achieving 68% overall response rate (ORR) and 53% complete response rate (CR)(NCT04088890). Long-term follow-up (median 43.5 months), revealed sustained clinical benefit among complete responders, who achieved a median progression-free survival of 52 months and a 75% estimated 3-year overall survival rate. Using multi-omics analyses, we identified that intrinsic T-cell stemness characteristics present at apheresis associated with therapeutic success. Responding patients exhibited elevated TCF7 and LEF1 transcription factor activity and enhanced chromatin accessibility at TCF/LEF binding motifs. CAR T-cell products from CR patients demonstrated higher T-cell receptor diversity. Immune effector cell-associated hemophagocytic lymphohistiocytosis-like syndrome (IEC-HS) was associated with interferon-stimulated gene expression and STAT2 activity. These findings challenge the paradigm that T cells are irreversibly compromised after CAR therapy failure and provide mechanistic insights for optimizing sequential CAR therapies.

Coenzyme A (CoA) biosynthesis is controlled by the four isoforms of the rate-limiting enzyme pantothenate kinase (PANK), whose tissue expression and subcellular localization regulate CoA homeostasis. Pantazines are positive allosteric modulators of PANK that increase cellular CoA levels by disrupting feedback inhibition by acyl-CoA esters. In this study, a structure-guided design was used to modify the Pantazine scaffold near the ATP-binding site to address metabolic liabilities of earlier leads. Replacement of a metabolically labile cyclopropyl group with a sulfonamide introduced a new hydrogen-bonding interaction with the γ-phosphate of ATP in the PANK3•ATP•Pantazine complex. This interaction improved ligand affinity, solubility, and metabolic stability. Analysis of isoform-specific inhibition revealed that cellular CoA elevation correlates with the difference in affinity between PANK3 and PANK1β, defining an “activation window” for CoA induction. Lead sulfonamide Pantazines were metabolically stable and increased hepatic CoA levels, supporting their potential for treating metabolic CoA deficiencies.

ABSTRACT:Brexucabtagene autoleucel (brexu-cel) is a chimeric antigen receptor T-cell therapy approved for relapsed/refractory mantle cell lymphoma (R/R MCL). Here, we report real-world effectiveness and safety outcomes of brexu-cel in a prospective study of patients with R/R MCL, including subgroups based on prior treatment with Bruton's tyrosine kinase inhibitor, bendamustine, or autologous hematopoietic cell transplant (auto-HCT) and number of prior therapy lines, using Center for International Blood and Marrow Transplant Research registry data. A total of 476 patients with R/R MCL who received brexu-cel between July 2020 and December 2022 were included in the analysis. With a median follow-up of 13.5 months, the overall response rate was 91% and complete response rate was 82%. One-year overall survival and progression-free survival rates were 76% and 63%, respectively. One-year cumulative incidence of nonrelapse mortality was 8%. Prior auto-HCT was associated with better duration of response within 6 months after infusion (hazard ratio [HR], 0.49; 95% confidence interval [CI], 0.28-0.85) but greater risk of immune effector cell-associated neurotoxicity syndrome (odds ratio [OR], 1.66; 95% CI, 1.06-2.60). Prior bendamustine was associated with increased risk of prolonged thrombocytopenia (OR, 1.90; 95% CI, 1.13-3.21). In patients with 1 to 2 prior therapy lines, relapse or progression was less frequent compared with those with ≥3 prior lines (HR, 0.64; 95% CI, 0.42-1.00). Collectively, our results suggest that real-world outcomes with brexu-cel were consistent with those of the ZUMA-2 trial, regardless of prior therapy type or number of prior therapy lines.

Background: IEC-HS is a potentially life-threatening complication following CAR-T therapy in RRMM. Reliable diagnostic biomarkers are needed to help expeditiously identify cases to initiate prompt treatment and supportive care. Serum ferritin, a routinely available laboratory parameter, is commonly elevated in IEC-HS and has been used to identify cases. However, ferritin can also be elevated in cytokine release syndrome (CRS) or secondary to baseline tumor-related inflammation. The optimal diagnostic threshold for post-CAR-T ferritin in IEC-HS in RRMM has not been previously established. Methods: This study used data from 15 centers within the US Multiple Myeloma Immunotherapy Consortium to identify the optimal post-CAR-T ferritin threshold to distinguish RRMM patients (pts) with and without a diagnosis of IEC-HS. Receiver operating characteristic (ROC) analysis was used to determine the optimal threshold based on Youden's Index. The performance of the threshold was evaluated overall and stratified by CAR-T product (cilta-cel, ide-cel). Additional analyses included the temporal relationship of peak ferritin and IEC-HS diagnosis, the evaluation of IEC-HS criteria according to ferritin levels, comparison of IEC-HS criteria co-occurrence, and comprehensive baseline characteristic comparisons across ferritin strata. Results: Of 1502 RRMM CAR-T recipients (ide-cel, n=712; cilta-cel, n=790), 74 patients (4.9%) had a provider-determined diagnosis of IEC-HS. A post-CAR-T ferritin threshold of 7470 ng/mL was identified as optimal for distinguishing pts with and without IEC-HS (AUC 0.938). Sensitivity (0.904) and specificity (0.934) were both very high, indicating high discriminatory ability. Stratified ROC analyses showed near-identical optimal thresholds for cilta-cel (7450 ng/mL; sensitivity 0.885, specificity 0.936, AUC 0.94) and ide-cel (7470 ng/mL; sensitivity 0.952, specificity 0.933, AUC 0.95), indicating minimal impact of CAR-T product on ferritin's prognostic utility. Baseline pt characteristics (N=1,413) differed significantly by ferritin threshold. Pts above the ferritin threshold of 7470 (N=154) were younger (median 64 vs 67 years; p=0.004), more frequently male (65% vs 56%; p=0.043), had higher baseline ferritin (1,300 vs 187; p<0.001), higher ECOG at apheresis (p=0.001), more likely penta-refractory (p=0.016), had higher baseline bone marrow plasma cell burden (p<0.001), and had higher R-ISS scores (p<0.001). Evaluation of IEC-HS criteria (Hines et al, TCT 2023) demonstrated significantly higher rates of laboratory and clinical criteria, including hepatic transaminase elevation (43% vs 15%), hypofibrinogenemia (53% vs 0%), cytopenias (95% vs 81%), hypertriglyceridemia (43% vs 8%), ICANS (52% vs 23%), renal insufficiency (20% vs 0%), and soluble IL-2 receptor elevations (47% vs 4%), in pts with ferritin >7500 ng/mL compared to those with lower ferritin. Heatmap visualization revealed distinct patterns of co-occurring criteria in high- and low-ferritin groups. Assessment of the timing of peak ferritin and IEC-HS diagnosis among IEC-HS cases revealed a median difference of 0 days (IQR: -1, 0), suggesting simultaneous occurrence. Median time to max ferritin was 9 days (IQR 8,12) in IEC-HS pts compared to 8 days (IQR 5,10) in non-IEC-HS pts (Wilcoxon p<0.05). Conclusions: In this analysis of over 1500 patients, a post-CAR-T ferritin level of 7500 ng/mL robustly identifies RRMM pts with IEC-HS following either cilta-cel or ide-cel. Pts exceeding this threshold demonstrate marked enrichment in IEC-HS diagnostic criteria and significant differences in baseline characteristics, warranting further study of the role of ferritin in IEC-HS diagnosis and early intervention.

ABSTRACT:The treatment patterns and clinical outcomes for patients experiencing progression of disease (POD) following CD19-directed chimeric antigen receptor (CAR) T-cell therapy for relapsed or refractory (R/R) mantle cell lymphoma (MCL) are undefined. We identified all patients who received CD19-directed CAR T-cell therapy for R/R MCL therapy across 15 international centers, and studied those experiencing POD post-CAR T-cell therapy in detail. We extracted clinical/treatment/pathologic variables, and associated these features with survival outcomes. In total, 384 patients received CAR T-cell therapy, and 135 (35%) experienced POD. POD occurred at a median of 6 months following CAR T-cell therapy infusion, and most (64%) patients with POD had complete response as best response to CAR T-cell therapy. Tumor features at POD included blastoid/pleomorphic morphology in 29 of 78 (37%) patients, and TP53 mutation in 21 of 41 (51%) patients. Following POD, 17 patients received no further therapy, 13 underwent local therapy, and 105 received systemic therapy. The most common first-line systemic therapies were chemo(immuno)therapy (22 patients; overall response rate [ORR], 40%), pirtobrutinib (17 patients; ORR, 36%), and bispecific antibodies (13 patients; ORR, 67%). Among patients experiencing POD, the median progression-free survival and overall survival (OS) were 2.5 months and 5.4 months, respectively, from POD. Lack of response to CAR T-cell therapy and short time from CAR T-cell therapy infusion to POD (<3 vs 3-6 vs >6 months), among other factors, were associated with inferior OS after POD. In conclusion, we confirm the challenging prognosis for patients experiencing POD following CD19 CAR T-cell therapy for R/R MCL, and establish a benchmark for future investigations in this patient population.

Introduction: Based on efficacy of CD22-targeted CAR T-cells in a phase I trial in adults with relapsed/refractory (r/r) large B-cell lymphoma (LBCL)—including in those with relapse following CD19 CAR T-cells (CAR19) (Frank M, et al. Lancet 2024), firicabtagene autoleucel (firi-cel/CRG-022), an autologous CD22-directed chimeric antigen receptor (CAR) T-cell therapy was tested in a Phase 2 study. Methods: The primary objective of this phase 2, open-label multicenter study was to evaluate efficacy of firi-cel in adults with r/r LBCL who progressed after CAR19 (cohort 1). The primary endpoint was overall response rate (ORR) as determined by blinded central review using Lugano Response Criteria. Cohort 2 was for those with a non-conforming product; cohort 3 was for those who received prior CAR19 and bispecific T-cell engagers. In contrast to the phase I study, CD22 expression was not required. Secondary objectives were to evaluate toxicity and additional efficacy endpoints, including ORR, complete response (CR), duration of response (DOR), progression-free survival (PFS) and overall survival (OS) as determined by individual investigators. Firi-cel was centrally manufactured using the Miltenyi Prodigy and utilized a different, more rapid in-culture timeline (5-9 days) compared to the phase I trial (7-12 days). Enrollment started Aug 2023 and data cut-off was 4/8/2025. Results: 138 patients underwent screening and 101 proceeded to leukapheresis (37 screen failures). 93 products were manufactured and 84 patients were infused. 15 patients dropped out due to manufacturing failures (7), disease progression (3), PI decision (4), or other (1). The median vein-to-vein time was 35 days (range, 24-86 days). For those infused, the median age was 65.5 years (19-87 years), 56 (67%) were male, 6 (7%) were non-white and 12 (14%) were Hispanic. The median number of prior lines of therapy was 3 (2-8) and the median time from prior CAR19 to apheresis was 7.4 months (1.6-66 months). 12 (14%) had bulky disease and 46 (55%) had elevated LDH. The median H-score for tumor CD22 expression was 65 (range 0-300). Among 52 patients with an available sample, 10 had undetectable CD22. At data cut-off (median follow-up of 4.8 months) and using investigator-determined responses (as central review was not available after trial closure), for cohort 1 (n=69), the ORR and CR rates were 73% (95% CI, 60-83%) and 46% (34-59%), respectively. The median DOR was 2.4 months (95% CI, 2.0-5.1). The median PFS and OS were 3.1 months (2.6-4.9) and 12.4 months (7.4-non-estimable (NE)). Results for cohort 2 (n=3) were comparable and will be reported later. For cohort 3 (n=12), the ORR and CR rates were 50.0% (21-79%) and 25% (6-57%) respectively. The median DOR was 2.2 months (1.1-NE), while the median PFS and OS were 2.8 months (0.9-3.4) and 5.9 months (2.8-NE), respectively. Any and grade 3+ CRS occurred in 66 (79%) and 4 (5%) patients. 8 (10%) had any grade ICANS with no Gr3+ seen. Immune effector cell associated hemophagocytic lymphohistiocytosis (IEC-HS) occurred in 21 (25%) subjects and was grade 3+ in 11 (13%). 5 (6%) had a fatal treatment-emergent adverse event, all related to IEC-HS or complications thereof. Firi-cel harvested after 5 (n=23), 7 (n=31), or 9 (n=15) days associated with 3-month CR rates of 32%, 15%, and 7%, respectively, and circulating firi-cel detectable in the peripheral blood in 91%, 58%, and 0% of patients at 3 months, respectively. Interestingly, day 5 products were enriched with central memory T-cells; while day 9 products were enriched with effector memory T-cells. CD22 tumor expression did not correlate with ORR or IEC-HS incidence or severity. Longer follow up is needed to determine whether CD22 tumor expression significantly correlates with DOR/PFS; so far patients with undetectable CD22 tumor expression trended toward shorter DOR/PFS. The trial was terminated due to limited durable responses and higher than anticipated toxicity.Conclusions: Firi-cel demonstrated high ORR in patients with r/r LBCL after prior CAR19. However, DOR was low likely due to altered manufacturing protocols and enrollment of patients with undetectable CD22 disease. Altered manufacturing may also have contributed to higher incidence and severity of IEC-HS. Further exploration of firi-cel pharmacokinetics and biology in relationship to toxicity will be essential to better understand the continued potential of CD22-targeting in LBCL.

SIGNIFICANCE:Late leukapheresis (>6 months after CAR19) resulted in less residual CAR19, higher CAR22 CD4+ naïve T and TCM cells, less TEM cells, and higher CD8+ TCM cells, but similar clinical outcomes to those with early leukapheresis. CAR22 responses were associated with higher transduction efficiency and CD8+ TCM and less CD8+ TEM cells.

Background: Adults with high-risk (HR), relapsed/refractory (r/r) B-ALL who receive CAR-T often require consolidative allogeneic HCT to achieve long-term remission. Emerging data suggests that adult B-ALL patients (pts) with prior HCT have superior PFS relative to HCT-naïve pts (Roloff JCO 2025). Our group is interested in combining CAR-T cells with allogeneic HCT to determine whether an all-in-one strategy is feasible and efficacious in HR B-ALL. We conducted two successive Phase 1 trials in adults with HR B-ALL using the same CD19/22 CAR construct. The first tested autologous CAR19/22 in adults with r/r or MRD+ B-ALL (Spiegel Nat Med 2021; NCT03233854). The second tested donor-derived, allogeneic CAR19/22 as a component of Orca-T in pts with HR genomics, MRD+, or r/r B-ALL (NCT05507827). We present results comparing toxicity, efficacy, and CAR kinetics of these two approaches. Methods: All pts received CAR-T cells engineered with a bivalent lentiviral vector to express CAR19/22 (murine anti-CD19 FMC63/fully human anti-CD22 m971 scFv, 41BB co-stim). Autologous CAR recipients (auto cohort) received Flu/Cy followed by CAR19/22 (1 or 3x106cells/kg) +/- IL15 receptor agonist. Allogeneic recipients (allo cohort) received myeloablative conditioning followed by Orca-T (HSPCs plus regulatory T cells on D0; conventional T cells on D+2 as per Meyer Blood 2025; NCT01660607) and donor-derived, allogeneic CD19/22 (1, 2, or 3x106cells/kg) on D+2 from the same donor. Single-agent tacrolimus began on D+3 and continued until ~D+180. Pts with >5% marrow blasts or prior CAR-T were excluded from the current analysis. Results: Twenty-eight pts with <5% marrow blasts at enrollment were included: 13 auto and 15 allo. 100% of the auto and 60% of the allo cohort received the maximum tested CAR-T dose of 3x106cells/kg. Median age was 36, 50% were female, and 65% were Hispanic; demographics were similar across cohorts. Adverse-risk ALL genomics included Ph-like (auto 23%, allo 20%), complex karyotype (auto 8%, allo 13%), KMT2ar (auto 8%, allo 7%), and TP53m (auto 0, allo 7%). Among the auto cohort, 70% had prior HCT. At enrollment, 92% of auto and 40% of allo pts had detectable MRD. Toxicities were mild in both cohorts; no grade 3-4 CAR-related toxicities were reported. Among the auto cohort, 69% experienced CRS (46% grade 1, 23% grade 2); among the allo cohort, 100% experienced CRS (80% grade 1, 20% grade 2). ICANS was rare, with only one grade 1 case in the allo cohort. All pts engrafted neutrophils (median days: auto 7, allo 13); platelet recovery occurred in 92% of auto and 100% of allo pts. Bacterial infections were more common in allo (auto 15%, allo 47%) while viral infections were similar (auto 15%, allo 13%); all infections were treated to resolution. Two pts (1 in auto, 1 in allo) developed mod/severe chronic GVHD following CAR19/22. GVHD began in the auto recipient following HCT and was worsened by CAR19/22. Three pts in the auto cohort received post-CAR consolidative HCT in CR. Thus, 12 out of 13 pts (92.3%) in the auto cohort received HCT during B-ALL treatment. At a median follow-up of 2.5 yrs, 7 pts died in the auto cohort; 6 from refractory B-ALL. There have been no relapses or deaths in the allo cohort. Estimated 18-month PFS was 38.5% and 100% (p<0.001), while OS was 77% and 100% (p=0.176) in the auto and allo cohorts, respectively. Within the first 28 days, peak CAR expansion (auto 1,365 vs allo 1,096, p=0.552) and AUC (auto 13,288 vs allo 13,057, p=0.988) were comparable. Median time to peak expansion was also similar (auto 13 days; allo 13 days). CARs persisted longer in the allo compared to auto recipients. At last follow-up, CARs were detectable by flow (LOD 10-4) in all but 2 pts in the allo cohort, with a median CAR persistence of 270 days. Conversely, median CAR persistence was 28 days in the auto cohort. Product characterization will be available by the time of the ASH Annual Meeting. Conclusion: In adults with HR B-ALL, Orca-T-allogeneic CAR 19/22 resulted in superior relapse prevention, survival, and CAR persistence relative to autologous CAR 19/22. We hypothesize this is due to tolerance for CAR molecules, resulting in persistent CAR expression and improved antitumor activity. Safety data were comparable between the two cohorts. Most adults with HR B-ALL receive dyssynchronous CAR-T and HCT during their treatment course. Thus, all-in-one HCT-allo-CAR represents a rational approach that warrants additional study.