Severe CRS Research Articles

EASIX and m-EASIX predict CRS and ICANS in pediatric and AYA patients after CD19-CAR T-cell therapy

AbstractCytokine release syndrome (CRS) and immune effector cell–associated neurotoxicity syndrome (ICANS) are complications of CD19-directed chimeric antigen receptor (CD19-CAR) T-cell therapy. The Endothelial Activation and Stress Index (EASIX) and modified EASIX (m-EASIX) scores have been retrospectively proven to be predictive of CRS and ICANS in adult CAR T-cell recipients. However, these scores have not been evaluated in pediatric cohorts. We retrospectively report on 76 pediatric and adolescent and young adult (AYA) patients with relapsed/refractory B-cell acute lymphoblastic leukemia treated with CD19-CAR T cells at St. Jude Children’s Research Hospital or John’s Hopkins Hospital. Data included patient, disease, and treatment characteristics. EASIX and m-EASIX scores were calculated at days –5 before, 0, and +3 after CAR T-cell infusion. CRS and ICANS occurred in 47 and 17 patients, respectively. At all evaluated time points, the median EASIX scores were higher for patients who developed severe CRS and any grade ICANS, and the median m-EASIX scores were higher in patients who developed severe CRS and severe ICANS than those with no/mild CRS/ICANS. Receiver operating characteristic curve analysis showed that both scores were strong predictors of CRS, especially severe CRS, at all time points. Any grade and severe ICANS were best predicted by both scores at day +3. m-EASIX uniformly outperformed EASIX, except for predicting any grade ICANS. Our results validate the potential utility of EASIX and m-EASIX scores for predicting CAR T-cell–related complications for pediatric and AYA patients.

Venous Thromboembolism Risk in Hematological Malignancies Post-Chimeric Antigen Receptor T-Cell (CAR-T) Therapy: A Meta-Analysis of Phase 2 and Phase 3 Clinical Trials.

Chimeric Antigen Receptor T-cell (CAR-T) therapy uses genetically engineered T-cells with specific binding sites. This therapy allows for tumor specificity and durable treatment responses for patients with hematological malignancies. In this review, we study the risk of venous thromboembolism (VTE) associated with CAR-T therapy. We searched the National Institutes of Health library, Cochrane Library Databases, ClinicalTrials.gov database, and medical literature search engines PubMed and Google Scholar for Phase 2 and Phase 3 drug-efficacy and safety trials to determine the aggregate incidence and risk of VTE treated with CAR-T. Of 1127 search results, nine studies were identified and included in our meta-analysis. Of the 1017 patients who received therapy, 805 patients (79.15%) experienced some degree of CRS, and 122 patients (11.9%) experienced severe CRS (higher than grade 3). Only three out of one thousand and seventeen patients were reported to have experienced venous thromboembolism. Our study did not find a statistically significant association between increased VTE incidence (OR = 0.0005, 95% CI [0.0001, 0.0017]) and CRS/ICANS (p < 0.0001). There was a 0.0050 (95% confidence interval [0.0019, 0.0132]) relative risk for VTE. In our study, we did not find a statistically significantly increased risk of developing VTE despite CRS and underlying malignancy, which have been associated with increased risk of VTE.

Adverse Reactions in Relapsed/Refractory B-Cell Lymphoma Administered with Chimeric Antigen Receptor T Cell Alone or in Combination with Autologous Stem Cell Transplantation.

(1) Background: The combination of CAR-T with ASCT has been observed to enhance the efficacy of CAR-T cell therapy. However, the impact of this combination on adverse reactions is still uncertain. (2) Methods: Between January 2019 and February 2023, 292 patients diagnosed with r/r B-cell lymphoma received either CAR-T therapy alone or in combination with ASCT at our institution. We evaluated the incidence of CRS and CRES and utilized a logistic regression model to identify factors contributing to severe CRS (grade 3-4) and CRES (grade 3-4). (3) Results: The overall incidence of CRS and CRES was 78.9% and 8.2% in 147 patients receiving CAR-T alone, and 95.9% and 15.2% in 145 patients receiving CAR-T combined with ASCT, respectively. The incidence of overall CRS (p < 0.0001) and mild CRS (grade 1-2) (p = 0.021) was elevated in the ASCT combined with CAR-T group. No significant difference was observed in severe CRS and CRES between the groups. Among the 26 cases of lymphoma involving the central nervous system (CNS), 96.2% (25/26) developed CRS (15.4% grade 3-4), and 34.6% (9/26) manifested CRES (7.7% grade 3-4). Female patients had a lower incidence of severe CRS but a higher incidence of severe CRES. Lymphomas with CNS involvement demonstrated a higher risk of CRES compared to those without central involvement. (4) Conclusions: The combination of ASCT with CAR-T demonstrated a preferable option in r/r B-cell lymphoma without an increased incidence of severe CRS and CRES.

Unlocking Predictive Power: Quantitative Assessment of CAR-T Expansion with Digital Droplet Polymerase Chain Reaction (ddPCR).

Flow cytometry (FCM) and quantitative PCR (qPCR) are conventional methods for assessing CAR-T expansion, while digital droplet PCR (ddPCR) is emerging as a promising alternative. We monitored CAR-T transcript expansion in 40 B-NHL patients post-infusion of CAR-T products (axi-cel; tisa-cel; and brexu-cel) with both His-Tag FCM and ddPCR techniques. Sensitivity and predictive capacity for efficacy and safety outcomes of ddPCR were analyzed and compared with FCM. A significant correlation between CAR-T counts determined by FCM and CAR transcripts assessed by ddPCR (p < 0.001) was observed. FCM revealed median CD3+CAR+ cell counts at 7, 14, and 30 days post-infusion with no significant differences. In contrast, ddPCR-measured median copies of CAR-T transcripts demonstrated significant lower copy numbers in tisa-cel recipients compared to the other products at day 7 and day 14. Patients with a peak of CAR transcripts at day 7 exceeding 5000 copies/microg gDNA, termed "good CAR-T expanders", were more likely to achieve a favorable response at 3 months (HR 10.79, 95% CI 1.16-100.42, p = 0.036). Good CAR-T expanders showed superior progression-free survival at 3, 6, and 12 months compared to poor CAR-T expanders (p = 0.088). Those reaching a peak higher than 5000 copies/microg gDNA were more likely to experience severe CRS and ICANS. DdPCR proves to be a practical method for monitoring CAR-T expansion, providing quantitative information that better predicts both treatment outcomes and toxicity.

Corrigendum: Prediction of severe CRS and determination of biomarkers in B cell-acute lymphoblastic leukemia treated with CAR-T cells

Corrigendum: Prediction of severe CRS and determination of biomarkers in B cell-acute lymphoblastic leukemia treated with CAR-T cells

IL-10 Levels Differentially Regulate IFNg Signaling of CART19 and CART22

Introduction: CD19-directed CART (CART19) are highly effective in the treatment of relapsed or refractory B-cell acute lymphoblastic leukemia (B-ALL). However, some pts relapse with CD19 negative disease after CART19, which has led to the development of CD22-directed CART (CART22). While CART22 has produced 70% CR in CD19 negative ALL, this is lower than CART19 and there is less evidence for long-term disease control compared to CART19. Interestingly, toxicity patterns are different with CART22 pts experiencing a later and less severe CRS even at high disease burden. To better understand these differences in efficacy and toxicity we conducted comprehensive serum proteomic profiling on serial samples from pts treated with CART-19 or -22. Methods: Serial serum samples from pts enrolled on two clinical trials of the murine CART19 CTL019 (NCT01626495 &amp; NCT02906371) and CART22 (NCT02650414) were examined. Pts were categorized as having severe (Grade 3 or 4) or minimal CRS (Grade 1 or 2). All statistical analyses were performed using R (v4.2.2) and PRISM (v9). Differential expression analyses were performed between CART19 and CART22 pts. Significance was defined as an absolute fold change &amp;gt; 2, and a false discovery rate (FDR) &amp;lt; 0.05. All in vitro experiments were performed in triplicate. Two-tailed t tests were calculated. Results: 43 pts (CART19 N=26 and CART22 N=17) with 223 unique timepoints were included in this analysis. All CART22 pts had minimal CRS; 13 CART19 pts had minimal and 13 had severe CRS. Both cohorts had high disease burden prior to infusion (CART19 mean = 29.9%, CART22 mean=44.3%, p=0.19). All pts who received CART22 had previously received CD19 directed immunotherapy (CART19 N=16, blinatumomab N=1). At the pre-infusion timepoint, 12 proteins were significantly different between pts in the CART19 and CART22 cohorts. The protein most significantly differentially expressed in patients who subsequently underwent CART22 treatment was the anti-inflammatory cytokine IL-10. IL-10 levels were consistently elevated in patients who received CART22, surpassing levels at all observed timepoints, even when compared with patients treated with CART19 who developed severe CRS (See Fig 1). We therefore hypothesized the IL-10 levels may be impacting the efficacy and CRS associated with CART22. We next tested the impact of IL-10 on IFNγ as a surrogate marker of CRS in a series of in vitro experiments. CART-19 or -22 cells from the same donor were co-cultured with NALM-6 cells in the presence and absence of IL-10. Without IL-10 present, CART22 cells produced higher levels of IFNγ than CART19 cells (8959 vs 6395 pg/mL, p=0.005). Inversely, with IL-10 present, CART19 cells produced more IFNγ than CART22 cells (21006 vs 15157 pg/mL, p=0.05). We evaluated the length of immune synapse (IS) formation, the time between CART cell interaction and blast killing, using live-cell microscopy, and found that CART22 cells had a trend towards a prolonged IS formation relative to CART19 cells (median time to detachment 9.1 min vs. 3.5 min, p=ns). Finally, given the differences in time of onset of CRS following CART19 vs CART22, we looked at levels of IFNγ and its canonical responder CXCL9 between pts with minimal CRS only. As expected, we found a later peak of IFNγ in CART22 pts compared to CART19 pts (Figure 2). Interestingly, despite similar peaks in IFNγ, CXCL9 levels were higher in CART22 pts, implying dysregulation of the IFNγ/CXCL9 axes in CART22 but not CART19 pts. Conclusions: Comparing comprehensive serum proteomic profiling between CART19 and CART22 pts we make several novel observations. First, IL-10 levels are significantly higher in CART22 pts at pre-infusion, suggesting that previous immunotherapy has caused an upregulation of this anti-inflammatory cytokine. Second, we show that IL-10 levels have a differential impact on IFNγ levels in CART19 vs CART22 cells. This may impact both CRS associated with CART cells and efficacy and may contribute to observed differences in IFNγ and CXCL9 levels seen between the two patient populations. These findings are significant for the clinical translation of CART22 and other immunotherapies, as previous immunotherapy may lead to sustained alterations in the cytokine milieu. Furthermore, IL-10 is a targetable cytokine that could be modulated in future studies to improve efficacy of CART22.

A Multicenter Study of CAR-T Cell Therapy for Relapse of B-ALL Post Allogeneic Stem Cell Transplantation

BACKGROUND: Patients with acute B-cell lymphoblastic leukemia (B-ALL) relapsed after allogeneic stem cell transplantation (allo-HSCT) have very poor prognosis. Chimeric antigen receptor T (CAR-T) cells targeting CD19 have been developed as one of the effective immunotherapies for relapsed/refractory B-ALL. The safety and efficacy of CAR-T cells in patients relapsed after allo-HSCT remain unclear. METHODS: This study analyzed 60 B-ALL patients relapsed after allo-HSCT treated with CAR-T cells between October 2015 and February 2022 from four Chinese centers. Their pre-treatment patient characteristics, treatment regimens, efficacy, adverse effects, and follow-up data were comprehensively analyzed. RESULTS: One patient refused efficacy evaluation. 7 patients died before day 28 after CAR-T infusion. A total of 52 were assessed for efficacy within 28 days after CAR-T infusion.76.92% (40/52) patients achieved complete remission (CR) at Day 28 after CAR-T infusion, including 38 patients who achieved MRD-negative CR. 4 of the 40 patients relapsed at a median follow-up date of 12.1 months. The 1-year OS and EFS of all patients were 52.8% ± 7.0% and 51.5% ± 7.0%, respectively, and the 2-year OS and EFS were 40.1% ± 8.6% and 45.1% ± 8.6%, respectively. Multifactorial analysis showed that patients with severe CRS had worse OS and EFS, and other factors including age, gender, site of CAR-T tumor involvement, type of previous transplantation, previous transplantation type, CAR-T product and CRS grade, etc., did not affect the long-term survival of patients. The incidence of CRS was 80.00%, the incidence of grade ≥3 CRS was 20.83%, and the median time of CRS was 2 days after CAR-T cell infusion (range: 0-34 days). 3 patients (5.00%) died due to multiorgan failure caused by severe CRS, and the rest of the patients' CRS was controlled, and the grade of CRS was related to the proportion of blast cells in the bone marrow prior to CAR-T cell infusion., independent of the type of transplantation and the source of CAR-T cells. The incidence of ICANS was 5.00%. The incidence of aGvHD was 30.00%, and patients who had received prior haploidentical allogeneic HSCT were significantly more likely to develop aGvHD after CAR-T cell infusion than those who had received prior matched allogeneic HSCT. The occurrence of aGvHD after CAR-T treatment was not associated with the occurrence of CRS (p = 1), the presence of aGvHD after prior transplantation (p = 0.3484), the presence of cGvHD after prior transplantation (p = 0.3167), the presence of cGvHD at the time of CAR-T infusion (p = 0.5136), and the presence of prior donor lymphocyte infusion (p = 0.7404), and whether CAR-T cells were from autologous or donor (p = 0.4819). CONCLUSIONS: CAR-T cells are safe and effective in treating B-ALL patients with post-transplant relapse, and donor-derived CAR-T cells do not exacerbate CRS with aGVHD, and there is a high incidence of aGVHD after CAR-T therapy in patients with HLA-haplotype-matched transplantation.

Enhanced T Cell Function of PTPN2 Deleted CAR-T Cells Comes at a Cost: PTPN2 Knockout CAR-Ts Secrete More Cytokines and Demonstrate Increased Cytotoxicity, but Exhibit More Severe CRS and Icans in a Non-Human Primate Model

Background: Despite the success of CD19 CAR-T cells (CAR-Ts) in inducing remission, relapse remains a major issue. Previous studies have shown that upregulation of negative T cell regulators can contribute to CAR-T failure, and that deletion of these regulators can enhance CAR-T efficacy. A potent negative regulator is PTPN2, which inhibits T cell function by modulating T cell receptor and cytokine signaling pathways. While murine models have shown that PTPN2-knockout T cells improve tumor control, these models fail to reliably predict clinical efficacy or toxicity. To improve this predictability, we investigated PTPN2 KO CAR-Ts in primary human cells and in a NHP model of B-cell directed CAR-T therapy. Methods: CRISPR/Cas9-mediated PTPN2 deleted (‘KO‘) human CD19 CAR-Ts were assessed for phenotype/function using cytokine secretion and cytotoxicity assays. PTPN2 KO NHP CD20 CAR-Ts were administered to lymphodepleted NHPs using our established model and a dose escalation with Level 1: 6x10 4, Level 2: 6x10 5, Level 3: 3x10 6, and Level 4: 6x10 6 CAR-T/kg, followed by assessment for CAR-T expansion, B cell aplasia, CRS and ICANS. Results: PTPN2 KO was successfully achieved in human CAR-Ts (83.8 + 5.2% deletion). IFNγ production was significantly higher in PTPN2 KO CD19 CAR-Ts vs control cells (35.1 + 0.97% vs 23.4 + 0.98%, p=0.001). In cytotoxicity assays targeting the B-ALL cell line NALM6, PTPN2 KO CD19 CAR-Ts demonstrated significantly increased killing vs control cells (for example, at E:T ratio 1:1 59.6 + 9.8% vs 42.5 + 12.9% p = 0.03). We evaluated the proliferation, efficacy, and toxicity of PTPN2 KO CD20 CAR-Ts in 5 NHPs. The CAR-T PTPN2 KO rate ranged from 63-91%. During dose escalation, no expansion of CAR-Ts was observed at dose levels 1 and 2 (n=1 for each, Fig 1). However, all animals infused at dose level 3 (n=3, 3x10 6 CAR-Ts/kg) demonstrated CAR-T expansion (max expansion 18.6 + 6.8% CAR-Ts) and B cell aplasia, and all animals developed laboratory and clinical signs of CRS and ICANS ( Fig 1). One animal at dose level 3 experienced CRS on day +4 that was severe enough to require tocilizumab, with symptoms subsequently improving. On day +6, this animal also developed ICANS, including ataxia and muscle weakness, requiring 1 dose of Dexamethasone (1mg/kg), after which symptoms resolved. One animal received dose level 4 (6x10 6 CAR-Ts/kg). This recipient displayed earlier and higher expansion of CAR-Ts (day 3: 16.7%, day 7: 56.3% CAR-Ts, Fig.1), and developed severe CRS (with elevated CRP, LDH (not shown) and Ferritin, Fig.1) and ICANS that were unresponsive to treatment with 2 doses of tocilizumab and multiple doses of dexamethasone, with this recipient meeting humane euthanasia endpoints. Importantly, previous animals (n=5) receiving 6-12 x 10 6PTPN2 expressing (WT) CAR-Ts/kg, did not develop severe CRS nor ICANS (and did not require Toci or Dex). This suggests that PTPN2 KO CAR-Ts are associated with augmented toxicities. An extensive terminal analysis of the Dose Level 4 animal was performed; pathology demonstrated widespread cerebral edema and CAR-T CNS infiltration. Because the CAR-T infusion contained both PTPN2 KO and PTPN2 WT CAR-Ts, an assessment could be made for enrichment of PTPN2 KO CAR-Ts in the blood and brain parenchyma. Compared to the infused product (63% KO CAR-Ts, Fig.2), there was enrichment for KO CAR-Ts in the blood (72% KO CAR-Ts) and the brain parenchyma (84% KO CAR-Ts, Fig 2). This suggests increased expansion and CNS infiltration of PTPN2 KO versus PTPN2 WT CAR-Ts. Flow cytometry analysis of the PTPN2 KO CAR-Ts from the blood at maximum expansion revealed high expression of the proliferation and activation markers Ki67 and GZMB (84.6%, 74.5% of all CAR-Ts). Of note, at Dose Level 3, neither CAR-T persistence (15 + 2 days vs 20 + 5 days) nor duration of B cell aplasia (41+ 5 days vs 37 + 3 days) were increased with PTPN2 KO CAR-Ts vs historic controls infused with PTPN2 WT CAR-Ts. Conclusion: We demonstrate that PTPN2 KO CAR-T cells possess increased effector function, proliferation, and CNS infiltration versus PTPN2 WT CAR-Ts. However, this enhanced efficacy was associated with increased severity of CRS and ICANS, emphasizing that careful attention to the dose of PTPN2 KO CAR-Ts would be important. These results also highlight the utility of evaluating gene-modified CAR-Ts in clinically relevant animal models, to thoroughly assess their efficacy and toxicity profiles.

Phase I/II Study to Evaluate the Safety, Feasibility, and Efficacy of FP-1201 (Intravenous Interferon-Beta-1a) to Prevent Toxicities after CD19-Directed CAR T-Cell Therapy: Trial in Progress

BACKGROUND CD19 chimeric antigen receptor (CAR) T-cell therapy has revolutionized the treatment of patients with relapsed/refractory B-cell malignancies. Yet it remains limited by potentially life-threatening toxicities such as CRS and ICANS. The risk of CRS and ICANS restricts the use of CD19 CAR T-cell therapy to large academic centers and leads to high healthcare resource utilization. Current toxicity prevention strategies have shown limited efficacy to date (prophylactic steroids with axi-cel: CRS, 80%; ICANS, 60%; Oluwole, BJH, 2021; early intervention with brexu-cel: CRS, 89%; ICANS, 60%; Shah, The Lancet, 2021). Our group has shown that endothelial activation and dysfunction are associated with the development of CRS and ICANS, suggesting a key role of increased vascular permeability and blood-brain barrier damage in their pathogenesis (Hay, Blood, 2017). Type-I interferons (IFN-alpha and beta) are major regulators of CD73 expression by endothelial cells, an enzyme critical to the maintenance of endothelial integrity. CD73 breaks down extracellular pro-inflammatory ATP into anti-inflammatory adenosine. In addition, extracellular ATP has been shown to be a major and early driver of systemic inflammation upstream from IL-6 production (Cauwels, Cell Death Dis, 2014), which is associated with severe CRS and ICANS. Preclinical models have demonstrated that IFN-beta-1a treatment is associated with reduced capillary and blood-brain barrier permeability via upregulation of CD73 expression (Floris, J Neuroimmunol, 2002; Kraus., Ann Neurol, 2004; Niemela, Eur J Immunol, 2008). In humans, two recombinant IFN-beta-1a therapies are FDA-approved for the treatment of multiple sclerosis. IFN-beta-1a given intravenously (IV) maximizes the drug's bioavailability and its protective effects on the endothelium. In a study of patients with ARDS, IV IFN-beta-1a (FP-1201 and FP-1201-lyo) was safe and induced CD73 expression (Bellingan, Lancet Respir Med 2014). Given the known effects of IFN-beta-1a on preserving endothelial function and blood-brain barrier integrity, we hypothesize that IV IFN-beta-1a (FP-1201) may prevent CRS and ICANS following CD19 CAR T-cell therapy ( Figure 1A). Since higher rates of severe CRS and ICANS have been reported after axi-cel and brexu-cel, which contain CD28-costimulatory domains, we will restrict the inclusion criteria to patients treated with these products to analyze a population with a higher unmet need and a more homogeneous risk of CRS/ICANS. STUDY DESIGN AND METHODS Objectives and endpoints: Primary objective: To evaluate the safety and feasibility of FP-1201 in patients undergoing treatment with axi-cel or brexu-cel with two co-primary endpoints: i) to estimate the incidence of dose-limiting toxicity rates within the first 14 days following the last administration of FP-1201; ii) to study the type, frequency, and severity of adverse events according to the NCI CTCAE v5.0 from the first administration of FP-1201 and until day +28 after CAR T-cell infusion Secondary objectives: i) To decrease the incidence and severity of ICANS; ii) to decrease the incidence and severity of CRS; iii) to decrease corticosteroid usage; iv) to evaluate the effect of FP-1201 on anti-tumor efficacy Exploratory objectives: To characterize the in vivo effects of FP-1201 on endothelial function, the systemic cytokine milieu, and CAR T-cell function Key inclusion criteria: Adults ≥18 years of age with Karnofsky performance status ≥60% and B-cell non-Hodgkin lymphoma eligible for treatment with axi-cel or brexu-cel Key exclusion criteria: Known hypersensitivity to IFN-beta or major organ dysfunction FP-1201 administration: The FDA-approved IFN-beta-1a Rebif® will be formulated for IV administration (FP-1201). Participants will receive FP-1201 at one of four dose levels detailed in Figure 1B. Statistical design and sample size: We will use a Bayesian Optimal Interval Design to guide the FP-1201 dose escalation. We will plan to treat up to 24 participants. SUMMARY This is a phase I/II study of IV IFN-beta-1a in preventing CRS and ICANS following axi-cel and brexu-cel. The aim is to demonstrate safety and efficacy and to investigate the biologic mechanisms of IFN-beta-1a in preventing endothelial dysfunction.Additional preclinical and preliminary clinical data will be presented at the meeting. This study is registered on clinicaltrials.gov as NCT05936229.

The Therapeutic Efficacy of CD19 Chimeric Antigen Receptor T Cells in Immune Thrombocytopenia Model

Abstract Introduction: ITP is a hemorrhagic autoimmune disease characterized by excessive platelet destruction and impaired platelet production,resulting in a high risk of bleeding. The pathogenesis of ITP involves immune intolerance towards platelet antigen, with platelet autoantibodies produced by plasma cells playing a significant role. Current treatments targeting this pathogenesis mainly rely on CD20 monoclonal antibodies, such as rituximab. However, as CD20 expression is present at the pre-B cell and mature B cell stages but absent on the surface of mature plasma cells. This can explain why a subset of autoantibody-positive patients do not respond to B-cell depletion therapy. CAR-T cell therapy, a form of adoptive cellular immunotherapy, has shown great potential in hematological malignancies and solid tumors. Recent studies have demonstrated its potential effectiveness of CAR-T cell therapy in various autoimmune diseases. CD19, expressed at all stages of B cell differentiation, presents an opportunity for CAR-T cell therapy in ITP. This study aims to evaluate the efficacy of CD19 CAR-T cell immunotherapy in an active murine ITP model. Methods: CD42-knockout mice were immunized with wild type (WT) C57BL/6 mice and splenocytes from these immunized mice were transplanted into irradiated WT mice to construct a murine model of active ITP. The ITP mice were then randomized into two groups, with the experimental group receiving an intraperitoneal injection with 1×10 6 CD19 CAR-T cells. Platelet counts were monitored weekly, and after 3 weeks, the ITP mice were euthanized and sacrificed. Single-cell suspensions were prepared from harvested spleens for analysis. Anti-murine antibodies were analyzed using flow cytometry (Beckmann Coulter, Brea, CA, USA). All data were analyzed by Statistical Package for the Social Sciences (SPSS) software, version 25.0 (IBM Corp., Armonk, NY, USA). P &amp;lt; 0.05 was considered statistically significance. Results: Our results demonstrated that the platelet counts of ITP mice reached their lowest level on day 7 after spleen cell transplantation, gradually recovering within a week. Platelet counts were significantly higher in the CD19 CAR-T cell therapy group compared to the control group on day 7 and persisted until day 21. There were no significant differences in weight between two groups, indicating no severe complication or CRS were identified. In the third week CD19 CAR-T cell therapy, the proportion of plasma cells in the spleen was determined, showing a marked decrease in the percentage of CD138+ plasma cells in the CAR-T group compared to the control group. Additionally, at day 14, the titers of anti-platelet CD42-specific antibodies were significantly lower in the CAR-T cell treated group compared to the control group. Furthermore, the mean fluorescence intensity (MFI) of CD19+ B cells in the spleen cells of the CD19 CAR-T cell immunotherapy group was significantly decreased compared to the control group. Conclusion: This study demonstrates the effectiveness of CD19 CAR-T cell therapy in treating thrombocytopenia by suppressing plasma and B cells in a mouse model of active ITP. These findings provide valuable insights into the potential therapeutic application of CD19 CAR-T cell immunotherapy for immune thrombocytopenia. Disclosure: No conflict of interest.

Progression-Free Survival but Not Overall Survival Is Superior in Relapsed/Refractory Large B-Cell Lymphomas Treated with Axicabtagene Ciloleucel Compared to Tisagenlecleucel: Results of the CART-SIE Real Life Italian Study

Introduction The CART-SIE is a national prospective/retrospective observational study aimed at collecting the real-life data of all consecutive lymphoma patients treated with CAR-T cells in the Italian centers. Given the recognized efficacy of axicabtagene ciloleucel (axi-cel) and tisagenlecleucel (tisa-cel) in relapsed/refractory large B-cell lymphoma (R/R LBCL) after at least two previous treatments, the best product in terms of efficacy and safety is still a matter of debate. Riedell reported comparable outcomes between axi-cel and tisa-cel in patients treated in 8 US centers; on the other hand, Bachy demonstrated, in a matched comparison, that axi-cel had a higher efficacy and a higher toxicity compared to tisa-cel. Methods On these bases, we conducted a subgroup analysis in the CART-SIE study, with the aim to evaluate the outcome (ORR, DoR, OS, PFS), and the safety (CRS, ICANS) of all R/R LBCL treated with different CAR-T (axi-cel versus tisa-cel) (primary mediastinal B-cell lymphoma, PMBCL, were excluded). A propensity score (PS) model estimated for the probability of being treated with tisa-cel (arbitrary) was performed. Variables used for the PS model (accordingly to Bachy, 2022) were: histology, age, sex, disease status (relapse vs. refractory), Ann Arbor stage (I/II vs. III/IV), IPI (&amp;lt; 3 vs. &amp;gt;=3), LDH, C reactive protein, bulky disease, N of previous treatments, ASCT, bridging therapy (no vs. yes with response vs. yes without response), time since last treatment and centers size (&amp;gt;=25 vs. &amp;lt; 25 cases contributed). Results From March 2019 to June 2023, 659 patients were leukapheresed; 562 were infused and 556 with adequate follow-up were analyzed: 419 LBCL (229 diffuse large B-cell lymphomas, DLBCL; 77 arising from indolent lymphoma, tFL; 113 high-grade B-cell, HGBCL), 70 PMBCL and 67 mantle cell lymphomas. Here, we analyzed the results of the 419 LBCL: 45% (190) received axi-cel, 55% (229) tisa-cel. Clinical characteristics for axi-cel vs. tisa-cel were: median age 57 years (IQR 50;65) vs. 61 (IQR 52;66), p 0.059; refractory to the last treatment 74% (141) vs. 64% (146), p 0.0309; intermediate-high/high risk IPI 39% (74) vs. 46% (105), p 0.1336. Bridging therapy was performed in 82% (156) patients candidate to receive axi-cel and in 85% (195) tisa-cel, p 0.4263; the ORR to bridging was 28% (53) in patients candidate to axi-cel vs. 30% (68) tisa-cel, p 0.1840. All grade CRS was observed in 88% (168) infused with axi-cel, and in 77% (177) with tisa-cel, p 0.0030. The severe (grade 3-4) CRS was registered in 8% (15) axi-cel and in 8% (18) tisa-cel. All grade ICANS was recorded in 32% (61) treated with axi-cel and in 9% (20) with tisa-cel, p 0.0001; severe ICANS was reported in 9% (18) axi-cel and in 3% (6) tisa-cel. Treatment related mortality was 2% (4) in axi-cel vs. 1% (3) tisa-cel. Median follow-up time for infused patients was 12.07 months (IQR: 6.05, 22.37). The ORR at 30-days after CAR-T was 74% (141) with 53% complete response (CR) in axi-cel; ORR 58% (133) with 39% CR in tisa-cel, p 0.001. DoR at 12-months was 56% (95% CI: 48-67) for axi-cel vs. 49% (95% CI: 40-59) for tisa-cel, p 0.2745. The 12-months OS was 71% (95% CI: 64-79) for axi-cel vs. 60% (95% CI: 53-67) for tisa-cel, p 0.1086. The 12-months PFS was 48% (95% CI: 41-57) for axi-cel vs. 32% (95% CI: 26-39) for tisa-cel, p 0.0003. In a multivariable model with all the clinically relevant variables, the OS for the two products was similar (HR tisa vs. axi: 1.23, 95% CI:0.86-1.75, p 0.2546), whereas the PFS was statistically superior for axi-cel compared to tisa-cel (HR: 1.65, 95% CI: 1.25-2.17, p 0.0004). The stabilized inverse propensity score weighting was applied to the subset of 277 LBCL (DLBCL, HGBCL, tFL) patients with complete data. The final population for weighted analysis included 201 patients, 100 treated with axi-cel and 101 with tisa-cel. The propensity score weighted analysis for tisa-cel vs. axi-cel was calculated; weighted log-rank test p-value for PFS was 0.0287 (Fig 1A), weighted log-rank test p-value for OS was 0.1547 (Fig 1B). Conclusions In the CART-SIE study, the outcome of patients treated with CAR-T was similar to those reported by pivotal trials and real-life studies, with manageable toxicities. At a median follow-up of 12 months, PFS for axi-cel was superior compared to PFS for tisa-cel; this advantage was confirmed in a propensity score analysis. The difference in PFS did not translate in a different OS, so far. CRS and ICANS were higher with axi-cel.

Proteomics Reveals the Potential Pathogenesis of Coagulopathy in Patients with Hematological Malignancies Following CAR-T Therapy

Background: Chimeric antigen receptor (CAR)-T cells have achieved great success in treating hematological malignancies. However, the management process during hospitalization can be complicated by the adverse events of coagulopathy. CAR-T-associated coagulopathy (CARAC) has a high prevalence and may develop into disseminated intravascular coagulation in severe cases. Meanwhile, the underlying mechanisms have not been fully elucidated. Our study aims to comprehensively analyze the profiles of CARAC and explore its potential pathogenesis. Methods: We collected peripheral blood samples from patients received CAR-T therapy in two cohorts at Wuhan Union Hospital. Cohort 1 included patients with acute B-lymphoblastic leukemia (B-ALL) from August 2019 to March 2021, and cohort 2 included patients with ALL and lymphoma from December 2021 to December 2022. Samples were collected at various timepoints, including before fludarabine/cyclophosphamide lymphodepletion (pre-FC), D0, D7, D14, D28, and at the peak of IL-6 after CAR-T cell transfusion. In cohort 1, we analyzed the peripheral blood protein profiles using proteomics, and in cohort 2, we verified the fibrinolysis-related indicators. The diagnosis of CARAC was based on the consensus of CARAC in 2022, and the CRS classification followed the ASTCT standard. Results: We found no significant differences in baseline characteristics among the patients in cohort 1 (n=20). All CARAC patients (n=10) had CRS, with half of them (n=5) having G≥3 CRS. In contrast, patients with CRS but not CARAC (CNC, n=3) had only G1-2 CRS, indicating that severe CRS is more likely to be associated with CARAC, consistent with our previous study. We identified 293 differentially expressed proteins (DEPs, p&amp;lt;0.05, |log2FC|&amp;gt;0.585) that were mostly downregulated in CARAC patients compared to CNC patients at the six timepoints. Enrichment analysis indicated that these DEPs were mainly involved in immune response, complement and coagulation pathways, fibrinolytic pathways, and acute inflammation response. We selected the top 10 DEPs with the highest degree of inter-protein correlation, including C3, C4A, C4B, MBL2, C8A, C8B, CRP, A2M, CLU, and FGA, which further suggest that complement and acute inflammation response play crucial roles in the pathogenesis of CARAC. Based on the clinical manifestations of hemorrhage in CARAC patients, hyperfibrinolysis is presumed to be the main mechanism. Interestingly, compared to patients without CRS (NC, n=7), CNC patients showed increased levels of SERPING1, CPB2, F2, FGA, FGB, FGG, KLKB1, PLG, and PROS1, which are proteins involved in the fibrinolysis pathway (p&amp;lt;0.05) (figure 1). Although there were no statistically significant differences, the levels of these proteins were higher in patients with G≥3 CRS compared to G1-2 CRS patients. Furthermore, compared to CNC patients, CARAC patients showed decreased levels of these proteins at D28 (p&amp;lt;0.05) (figure 1). Additionally, the nadirs of PLT and fibrinogen levels were markedly lower in CARAC patients compared to CNC patients, while the fibrinolytic indicators D-dimer and FDP were significantly higher in CARAC patients. Furthermore, we observed the activation of the fibrinolysis system in cohort 2. Among patients with CARAC (n=7), the levels of tPA, PAI-1, and uPAR were higher compared to patients with CNC (n=6). These findings indicate the activation of the coagulation system and hyperactivity of the fibrinolytic system in CARAC patients. Conclusions: Through proteomic analysis of cohort 1 and validation of cohort 2, we have preliminarily revealed that the core pathogenesis of CARAC involves the network regulation of immune, inflammatory, coagulation, and fibrinolytic systems.

Double Step-up Dosing (2SUD) Regimen Mitigates Severe Icans and CRS While Maintaining High Efficacy in Subjects with Relapsed/Refractory (R/R) B-Cell Non-Hodgkin Lymphoma (NHL) Treated with AZD0486, a Novel CD19xCD3 T-Cell Engager (TCE): Updated Safety and Efficacy Data from the Ongoing First-in-Human (FIH) Phase 1 Trial

Background: AZD0486 (formerly TNB-486) is a novel, IgG4 fully human CD19xCD3 bispecific TCE incorporating a unique low affinity anti-CD3 moiety designed to reduce cytokine release while retaining potent T-cell mediated cytotoxicity of malignant B cells. A silenced Fc prevents nonspecific binding, antibody-dependent cellular cytotoxicity, and confers a long half-life suitable for intermittent administration. Preliminary clinical activity in Diffuse Large B-cell Lymphoma (DLBCL) and Follicular Lymphoma (FL) was reported [ Hou et al, Blood 2022; Jacobs et al, HemaSphere 2023] following fixed and single step-up dosing (1SUD). We now present focused updated safety data following implementation of 2SUD in the ongoing FIH phase 1 study (NCT04594642). Methods: Patients with R/R CD19+ B-NHL failing ≥2 prior lines of therapy, including prior CD19 CART and/or CD20 TCE, were enrolled. AZD0486 was administered in escalating doses in either no SUD (Day (D)1, D15 0.03-2.4mg), 1SUD (D1 0.27-1 mg, D15 2.4-10 mg), or 2SUD (D1 0.27 mg, D8 1 mg, D15 2.4-7.2 mg, FL/DLBCL only) schedules. AZD0486 was given IV every 2 weeks in 28D Cycles (C) up to 2 years. Monthly dosing was considered for patients in complete response (CR) at C6. Responses were assessed by RECIL 2017 by Central Imaging Review, AEs by CTCAE v5.0, and CRS/ICANS by 2019 ASTCT criteria. Results: As of 03 July 2023, 62 patients (27 DLBCL, 25 FL, 5 mantle cell lymphoma, 4 marginal zone lymphoma, 1 other) received AZD0486 and were evaluable for safety. Median age was 68 (range 22-86), with 58% male, 81% stage III/IV. Median prior lines of therapy was 3 (range 2-16) including 23 (37%) failing CART and 3 (4.8%) failing CD20 TCE. Fifteen (24%) were CD20 negative at study entry. The complete response (CR) rate was 91% (10/11) in patients with FL treated in 2.4 mg dose cohorts and for all FL efficacy evaluable subjects dosed at 2.4mg or above, CR was achieved in 14/17 (83%) with an overall response rate (ORR) of 88%. Median duration of response (DOR) has not beenreached. With the implementation of 2SUD regimen, no Grade 3+ CRS or ICANS events were observed (Table 1). Grade 1-2 CRS events decreased from 62.5% to 22.2% (fixed/1SUD, 15/24 and 2SUD, 4/18). Grade 1-2 ICANS events decreased from 20% (5/24) to 5.6% (1/18), presented mainly as confusion, and typically resolved in 1-2 days. The most common AEs (occurring in &amp;gt;20%) of any grade and regardless of drug causality were CRS (48%), anemia (34%), neutropenia (32%), lymphopenia (29%), ICANS (27%) and decreased WBC (20.9%). Treatment-related events of Grade ≥3 included lymphopenia (24%), neutropenia (15%), ICANS (9.7%) and anemia (3.2%). No treatment related deaths were reported (1 death due to COVID19, unrelated) and no treatment-related AEs lead to discontinuation (1 patient discontinued due to COVID-19, unrelated). Preliminary analysis (TNF-a, IL-6, IL-8, IL-10) suggests a decrease in cytokine levels after target dose with 2 SUD compared to fixed dosing and 1SUD, regardless of target dose. Conclusions: AZD0486 (formerly TNB-486) is an active treatment in patients with advanced R/R B-NHL and has a predictable safety profile characterized by mainly low-grade AEs and fully transient and reversible CRS/ICANS events. The 2 SUD schedule reduced the overall rate of low grade CRS and ICANS (Grade 1-2) and abrogated Grade 3 events further improving the risk/benefit profile of AZD0486. Dose escalation is ongoing to identify the RP2D.

Brexucabtagene Autoleucel in Adults with Relapsed/Refractory B-Cell ALL: Outcomes and Novel Insights from the Real-World Outcomes Collaborative of CAR T in Adult ALL (ROCCA)

Introduction In October 2021, brexucabtagene autoleucel (brexu-cel) received U.S. FDA approval as the first CAR T-cell therapy for adults with relapsed/refractory (r/r) B-cell acute lymphoblastic leukemia (B-ALL) based on the 55-patient ZUMA-3 Phase II study. We subsequently established ROCCA and now report on the largest cohort of patients treated with commercial brexu-cel for r/r B-ALL to date. Methods Adults (18+) with r/r B-ALL infused with commercial brexu-cel across 25 U.S. institutions were included. ASTCT consensus criteria were used to score CRS and ICANS. Methodologies for assessing MRD (minimal threshold of 10 -4) included flow cytometry, NGS, or qPCR depending on institution practice. Duration of remission (DOR) was calculated from time of complete response (CR); progression-free survival (PFS) and overall survival (OS) were calculated from day of brexu-cel infusion and were not censored for hematopoietic cell transplant (HCT) or maintenance. All living patients were censored at the time of last follow-up prior to data lock, which occurred on June 30, 2023. Results Among 152 infused, the median age was 46 (range, 18-81), 57% were male, and 34% were Hispanic. Most (67%) had Ph- ALL, were heavily pre-treated (median 4 prior lines), and entered apheresis with high disease burden (57%). At time of apheresis, 23% of patients only had MRD+ disease and 15% were in complete molecular remission. While 82% developed CRS, the majority was grade 1-2, with 9% of the overall cohort experiencing grade 3-4 CRS. In contrast, 55% developed ICANS, with 32% of the entire cohort experiencing grade 3-4 ICANS. Eight patients (5%) died of toxicity/infection prior to D+28 response assessment. Among 133 patients with response assessment, 120 (90%) achieved morphologic CR, of whom 82% were MRD-, 15% were MRD+, and 3% MRD unknown. The median follow-up for survivors was 8.4 months; 45 patients have relapsed and 42 patients died. Median DOR was not reached. Median PFS and OS were 8.6 months and 15.6 months, respectively. Estimated PFS and OS of the entire cohort at 6-months were 61% (95% CI, 52-68) and 81% (95% CI, 73-87) and at 12-months were 47% (95% CI, 37-56) and 63% (95% CI, 53-72), respectively. We found no association between pre-CAR disease burden and post-CAR PFS/OS. However, patients with MRD- response to CAR had superior PFS relative to patients with MRD+ CR (median 14 months vs. 5 months, P=0.002). Forty-four patients received post-CAR consolidation/maintenance therapy while in CR: 25 allogeneic HCT, 15 TKI, 2 POMP, and 3 other/unknown. To examine the effect of consolidation/maintenance following brexu-cel, we performed a landmark analysis of PFS limited to patients alive and in CR at 2-months post-CAR infusion (N=113) and suggests superior PFS in patients receiving either HCT or other forms maintenance, relative to those receiving no further therapy following brexu-cel ( P=0.055). We then investigated post-CAR MRD-response in combination with receipt of post-CAR consolidation/maintenance and found that even among patients achieving MRD-negative response, post-CAR consolidation/maintenance led to superior PFS (Figure 1). Conclusions Among 152 adults treated with commercial brexu-cel for r/r B-ALL across 25 U.S. institutions, we found very high response rates (CR/CRi: 90%; 82% MRD-) consistent with the Zuma-3 data. While rates of severe CRS are low, grade 3-4 ICANS was observed in 32% of patients and warrants further investigation We demonstrate the prognostic impact of achieving an MRD-negative CR and an emerging role for consolidation/maintenance therapies to enhance the durability of response following brexu-cel in adults r/r B-ALL.

A Phase I Study of CD19-Targeted 19(T2)28z1xx CAR T Cells in Adult Patients with Relapsed or Refractory Diffuse Large B-Cell Lymphoma

Background: Autologous CD19 CAR T cell therapies have demonstrated favorable clinical responses in relapsed or refractory (R/R) diffuse large B-cell lymphomas (DLBCL), but only a subset of patients (pts) experience durable remissions. We hypothesized that the redundancy of CD28 and CD3ζ signaling in a CAR design incorporating all 3 CD3ζ immunoreceptor tyrosine-based activation motifs (ITAMs) might negatively affect T cell differentiation and promote exhaustion. Therefore, we created a new CD19 CAR construct with calibrated CAR activation potential by mutating 2 of the 3 ITAMs, termed 1XX, and hypothesized that a 1XX CAR would afford durable responses at lower dose and fewer toxicities compared to CARs comprising 3 ITAMs. We previously presented the data from the dose-escalation portion of the phase I clinical trial of 19(T2)28z-1XX CAR T cells in DLBCL (Park J et al. ASH 2022). We have now completed accrual and report the updated results from both dose escalation and expansion portion of the study with a longer follow-up (NCT04464200). Methods: This is a single-center, phase I, dose-escalation and expansion trial of 19(T2)28z1XX CAR T cells in adult pts with R/R DLBCL conducted at Memorial Sloan Kettering Cancer Center. Pts received fludarabine and cyclophosphamide lymphodepleting chemotherapy followed by a single infusion of CAR T cells. There were 4 dose levels in the dose escalation cohort: dose level (DL) 1 (25x10 6), DL2 (50x10 6), DL3 (100x10 6) and DL4 (200x10 6 CAR T cells). The primary objective of the trial was to evaluate safety and tolerability and determine the recommended phase 2 dose. Key secondary objectives include assessment of overall response and complete response rates. Results: 28 pts have been enrolled and treated; 16 pts on the dose escalation and 12 pts on the dose expansion phase of the study. Median age was 62 (range, 48-86). 20 pts (71%) had primary refractory disease, 3 pts (11%) had prior autologous HSCT, and 2 pts (7%) had prior autologous CD19 CAR T therapy. In the dose-escalation phase (n=16), 15 pts experienced grade 1-2 CRS (94%) and no pt experienced ≥grade 3 CRS. Two pts (13%) experienced ICANS: 1 pt with grade 1 and 1 pt with grade 3 (Table 1). Eight pts received tocilizumab and 5 pts received corticosteroid. Complete response (CR) was observed in 11 of 16 pts (69%) and partial remission (PR) in 1 pt (6%) with overall response rate (ORR) of 75%. Responses were seen across all dose levels (Table 1). The lowest dose (DL1: 25x10 6) was selected for dose-expansion based on exposure-response analysis and 12 additional pts were treated at that dose level. In a pooled analysis of 16 pts who received DL1 dose (4 in dose escalation and 12 in dose expansion), 12 pts and 1 pt experienced grade 1-2 (75%) and grade 3 CRS (6%), respectively. Only 1 pt experienced ICANS (6%) at grade 3 (same pt who had grade 3 CRS), which was reversible and transient (Table 1). 11 pts received tocilizumab and 9 pts received corticosteroids. Twelve pts achieved CR (75%) and 2 pts (12%) PR with the best ORR of 87% (Table 1). A lower metabolic tumor volume (MTV) at screening but not at post-bridging was associated with a higher likelihood of achieving CR (p=0.039). With a median follow-up of 345 days (range, 33-1024), 4 pts experienced relapse (1 CR and 3 PR pts) and 16 pts have ongoing CR &amp;gt; 6 months (Figure 1). While CAR T cell persistence analysis is ongoing, 5 pts have CAR T cells detected beyond one year in ongoing CR including a patient treated at DL1 with detectable CAR T cells at 2 years. Conclusions: Treatment with 19(T2)28z1XX CAR T cells was shown to be safe with durable remissions with low rates of severe CRS (4%) and ICANS (7%). The overall CR rate of 71% is encouraging and appears durable with the majority of CR patients in ongoing remission &amp;gt; 6 months at a median follow-up of 345 days and with persisting CAR T cells. With more patients treated at DL1 with a longer follow-up, the study demonstrates a high efficacy of 19(T2)28z1XX CAR T cells at a dose significantly lower (25x10 6) than those of approved CD19 CAR T cells (100-300x10 6) and support that the 1XX single ITAM signaling domain may lead to enhanced efficacy of CD19 CARs and allow infusion of a lower T cell dose with favorable toxicity profiles.

Prediction of severe CRS and determination of biomarkers in B cell-acute lymphoblastic leukemia treated with CAR-T cells.

CAR-T cell therapy is a novel approach in the treatment of hematological tumors. However, it is associated with life-threatening side effects, such as the severe cytokine release syndrome (sCRS). Therefore, predicting the occurrence and development of sCRS is of great significance for clinical CAR-T therapy. The study of existing clinical data by artificial intelligence may bring useful information. By analyzing the heat map of clinical factors and comparing them between severe and non-severe CRS, we can identify significant differences among these factors and understand their interrelationships. Ultimately, a decision tree approach was employed to predict the timing of severe CRS in both children and adults, considering variables such as the same day, the day before, and initial values. We measured cytokines and clinical biomarkers in 202 patients who received CAR-T therapy. Peak levels of 25 clinical factors, including IFN-γ, IL6, IL10, ferritin, and D-dimer, were highly associated with severe CRS after CAR T cell infusion. Using the decision tree model, we were able to accurately predict which patients would develop severe CRS consisting of three clinical factors, classified as same-day, day-ahead, and initial value prediction. Changes in serum biomarkers, including C-reactive protein and ferritin, were associated with CRS, but did not alone predict the development of severe CRS. Our research will provide significant information for the timely prevention and treatment of sCRS, during CAR-T immunotherapy for tumors, which is essential to reduce the mortality rate of patients.

CART‐SIE REAL LIFE STUDY: PRIMARY MEDIASTINAL B‐CELL LYMPHOMA (PMBCL) HAVE A SUPERIOR OUTCOME COMPARED TO LARGE B‐CELL LYMPHOMA (LBCL) TREATED WITH AXICABTAGENE CILOLEUCEL

Introduction: In Italy, axicabtagene ciloleucel (axi-cel) is commercially available for the treatment of LBCL, including diffuse large B-cell lymphoma (DLBCL-NOS), high grade B-cell lymphoma (HGBCL), transformed follicular lymphoma (tFL), and PMBCL patients, relapsed/refractory (R/R) after at least two prior treatments. Methods: The CART-SIE is an ongoing prospective and retrospective study collecting data on the outcome of all consecutive lymphoma patients treated with CAR-T cells. The aim of this analysis was to compare the outcome of PMBCL and LBCL treated with axi-cel in the Italian real life. Results: From 2019 to 2022, 444 patients were infused. Axi-cel was administered in 192 patients: 57 PMBCL and 135 LBCL, including DLBCL-NOS (85), HGBCL (28) and tFL (22), respectively. The clinical characteristics for PMBCL versus LBCL showed: median age 35 versus 56 (p = 0.0001), bulky 33/57 (58%) versus 47/135 (35%) (p = 0.0035), limited stage 35/57 (61%) versus 41/135 (31%) (p = 0.0001), respectively. Median follow-up time for infused patients was 10.99 months (IQR 4.18, 18.03). The Overall Response Rate (ORR, complete CR + partial PR) at 30-days after the infusion was 44/57 (77%) with 30 (53%) CR in PMBCL, and 97/135 (72%) with 67 (50%) CR in LBCL, (p = 0.4206). The 12-months Overall Survival (OS) was 89% (95% CI: 81–98) in PMBCL versus 70% (95% CI: 62–80) in LBCL (log-rank p = 0.0016); by different histology subtypes, the 12-months OS was 89% (95% CI: 81–98) in PMBCL versus 74% (95% CI: 63–86) in DLBCL-NOS, 58% (95% CI: 41–81) in HGBCL, 76% (95% CI: 58–100) in tFL (log-rank p = 0.0013). The 12-months PFS was 65% (95% CI: 53–80) in PMBCL versus 47% (95% CI: 39–57) in LBCL (log-rank p = 0.0160); by different histology subtypes, the 12-months PFS was 65% (95% CI: 53–80) in PMBCL versus 40% (95% CI: 30–54) in DLBCL-NOS, 51% (95% CI: 35–75) in HGBCL, 65% (95% CI: 47–90) in tFL (log-rank p = 0.0420). All grades CRS was observed in 49/57 (86%) PMBCL and 118/135 (87%) LBCL patients, with 9 (16%) and 12 (9%) severe (grade 3–4) CRS, respectively; all grades ICANS were reported in 25 (44%) PMBCL patients and in 46 (34%) LBCL, with 12 (21%) and 14 (10%) severe (grade 3–4) ICANS, respectively. Tocilizumab was administered in 41 (72%) PMBCL and in 90 (67%) LBCL; steroids in 20 (35%) PMBCL and in 36 (27%) LBCL patients. Twelve (21%) PMBCL and 15 (11%) LBCL patients were admitted in the intensive care unit. Treatment related mortality was reported in 3 (5%) PMBCL and 3 (2%) LBCL patients. In a multivariable model with all clinically important and unbalanced variables, PMBCL maintained its significantly superior outcome as compared to LBCL, for OS and for PFS. Conclusions: CART-SIE is the first real-life study comparing the prognosis of patients affected by R/R PMBCL and LBCL treated with axi-cel. PMBCL patients had a superior OS and PFS compared to LBCL, with a similar incidence of CRS and ICANS. Encore Abstract—previously submitted to EHA 2023 Keywords: aggressive B-cell non-Hodgkin lymphoma, cellular therapies Conflicts of interests pertinent to the abstract A. Chiappella Consultant or advisory role: Celgene-BMS, Gilead-Sciences, Ideogen, Janssen, Roche, SecuraBIO, Takeda Other remuneration: Lecture fees/Educational activities: Astrazeneca, Celgene-BMS, Gilead-Sciences, Incyte, Janssen-Cilag, Novartis, Roche, Takeda

A systematic review and meta-analysis of CD22 CAR T-cells alone or in combination with CD19 CAR T-cells.

https://www.crd.york.ac.uk/prospero, identifier CRD42020193027.

Monitoring of kinetics and exhaustion markers of circulating CAR-T cells as early predictive factors in patients with B-cell malignancies.

CAR-T cell therapy has proven to be a disruptive treatment in the hematology field, however, less than 50% of patients maintain long-term response and early predictors of outcome are still inconsistently defined. Here, we aimed to optimize the detection of CD19 CAR-T cells in blood and to identify phenotypic features as early biomarkers associated with toxicity and outcomes. In this study, monitoring by flow cytometry and digital PCR (dPCR), and immunophenotypic characterization of circulating CAR-T cells from 48 patients treated with Tisa-cel or Axi-cel was performed. Validation of the flow cytometry reagent for the detection of CAR-T cells in blood revealed CD19 protein conjugated with streptavidin as the optimal detection method. Kinetics of CAR-T cell expansion in blood confirmed median day of peak expansion at seven days post-infusion by both flow cytometry and digital PCR. Circulating CAR-T cells showed an activated, proliferative, and exhausted phenotype at the time of peak expansion. Patients with increased expansion showed more severe CRS and ICANs. Immunophenotypic characterization of CAR-T cells at the peak expansion identified the increased expression of co-inhibitory molecules PD1 and LAG3 and reduced levels of the cytotoxicity marker CD107a as predictors of a better long-term disease control. These data show the importance of CAR-T cells in vivo monitoring and identify the expression of PD1LAG3 and CD107a as early biomarkers of long-term disease control after CAR-T cell therapy.

Abstract 4150: Novel preclinical model for the evaluation of cytokine release syndrome in response to CD19xCD3 bispecific antibody in humanized mice

Abstract Cytokine Release Syndrome (CRS) is a systemic inflammatory response that is caused by the large, rapid release of cytokines in the blood by immune cells affected by infection or immunotherapy and remains a prominent challenge for T cell-based therapeutics. Bispecific T cell engagers (BiTEs) are fusion proteins that are generated by linking the targeting region of two antibodies: one arm binds to the tumor-associated antigen, and the other arm binds to T cells to promote T cell-mediated cytotoxicity in an MHC-independent manner. A CD19xCD3 BiTE has been approved by the FDA for the treatment of CD19-positive B-cell lymphoma. Despite having great clinical efficacy, CRS remains a major concern for BiTE therapy. This necessitates the development of a translational model that could predict CRS toxicity more accurately. Various in-vitro models proposed to assess BiTE-related CRS have several shortcomings as they do not provide details about the systemic immune response, off-target effects, neurotoxicity, tissue damage, and organ failure. Here we propose an in-vivo approach to concomitantly assess the efficacy and CRS toxicity of CD19xCD3 BiTE either alone or in combination with Rituximab (monoclonal antibody targeting CD20) in the Raji luciferase xenograft model of Burkitt’s lymphoma in PBMC humanized NSG-MHC Class I/II knockout mice. Five days post human PBMC engraftment (Study Day- SD 5), the mice were injected with Raji-luciferase cells. On SD 6, the mice were treated with BiTE, Rituximab, or the combination of BiTE and Rituximab. Additional control groups included OKT3 and Anti-CD28, the anti-T cell antibodies that failed clinically due to severe CRS. Efficacy was assessed through in-vivo imaging on SD5, SD8, and SD11. We observed tumor growth inhibition with BiTE, Rituximab, and the combination treatment. Clinical observations were recorded daily post treatment. Following cytokines were measured 6 hours after dosing and at study termination - IL-2, IL-4, IL-6, IL-10, TNF-α, and IFN-γ. Elevated cytokine levels were observed in the BiTE/combination group 6 hours post dosing but not in the Rituximab alone group. Together, the data suggest that the model could be used to assess the preclinical efficacy and CRS toxicity of BiTE. Citation Format: Deep S. Shah, Catalina Simion, Sang hu, Rhonda Chronis, Tre McClellan, Jae Hwang, Ryan Yang, Heather Baker, Danying Cai, James Keck, Lindsay Shopland. Novel preclinical model for the evaluation of cytokine release syndrome in response to CD19xCD3 bispecific antibody in humanized mice. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4150.