CD19-directed Chimeric Antigen Receptor Research Articles

Relapsed/Refractory Diffuse Large B-Cell Lymphoma: Is There Still a Role for Autologous Stem Cell Transplantation in the CAR T-Cell Era?

Recently, CD19-directed chimeric antigen receptor (CAR) T-cell therapies have revolutionized treatment strategies for diffuse large B-cell lymphoma (DLBCL). CAR T-cell therapy is increasingly used as a second-line therapy for patients with DLBCL with early relapse or refractoriness to initial chemoimmunotherapy and displaced high-dose chemotherapy, followed by autologous stem cell transplantation (ASCT) as the standard of care for these patients. However, patients with late relapse or chemosensitive disease still benefit from autologous stem cell transplantation. We will review practice-changing studies in early relapse (ZUMA-7 and TRANSFORM) under consideration of the negative BELINDA trial, with a focus on register data, comparing CAR T-cell therapy and ASCT for patients responding to salvage therapy.

Circulating Tumor DNA as a Complementary Prognostic Biomarker during CAR-T Therapy in B-Cell Non-Hodgkin Lymphomas.

The emergence of CD19-directed chimeric antigen receptor T-cell (CAR-T) therapy has revolutionized the treatment paradigm for R/R B-cell NHLs. However, challenges persist in accurately evaluating treatment response and detecting early relapse, necessitating the exploration of novel biomarkers. Circulating tumor DNA (ctDNA) via liquid biopsy is a non-invasive tool for monitoring therapy efficacy and predicting treatment outcomes in B-NHL following CAR-T therapy. By overcoming the limitations of conventional imaging modalities, ctDNA assessments offer valuable insights into response dynamics, molecular mechanisms of resistance, and early detection of molecular relapse. Integration of ctDNA monitoring into clinical practice holds promise for personalized therapeutic strategies, guiding the development of novel targeted therapies, and enhancing patient outcomes. However, standardization of assay methodologies and consensus on clinical response metrics are imperative to unlock the full potential of ctDNA in the management of B-NHL. Prospective validation of ctDNA in clinical trials is necessary to establish its role as a complementary decision aid.

Targeting TGFβ-activated kinase-1 activation in microglia reduces CAR T immune effector cell-associated neurotoxicity syndrome.

Cancer immunotherapy with chimeric antigen receptor (CAR) T cells can cause immune effector cell-associated neurotoxicity syndrome (ICANS). However, the molecular mechanisms leading to ICANS are not well understood. Here we examined the role of microglia using mouse models and cohorts of individuals with ICANS. CD19-directed CAR (CAR19) T cell transfer in B cell lymphoma-bearing mice caused microglia activation and neurocognitive deficits. The TGFβ-activated kinase-1 (TAK1)-NF-κB-p38 MAPK pathway was activated in microglia after CAR19 T cell transfer. Pharmacological TAK1 inhibition or genetic Tak1 deletion in microglia using Cx3cr1CreER:Tak1fl/fl mice resulted in reduced microglia activation and improved neurocognitive activity. TAK1 inhibition allowed for potent CAR19-induced antilymphoma effects. Individuals with ICANS exhibited microglia activation in vivo when studied by translocator protein positron emission tomography, and imaging mass cytometry revealed a shift from resting to activated microglia. In summary, we prove a role for microglia in ICANS pathophysiology, identify the TAK1-NF-κB-p38 MAPK axis as a pathogenic signaling pathway and provide a rationale to test TAK1 inhibition in a clinical trial for ICANS prevention after CAR19 T cell-based cancer immunotherapy.

Sequencing of anti-CD19 therapies in the management of diffuse large B-cell lymphoma.

Several second- and third-line immunotherapeutic options for patients with relapsed or refractory diffuse large B-cell lymphoma (DLBCL) ineligible for autologous stem cell transplant are directed against the B-cell antigen CD19. The anti-CD19 monoclonal antibody tafasitamab, paired with the immunomodulator lenalidomide, mediates antibody-dependent cellular toxicity and cellular phagocytosis; the antibody-drug conjugate loncastuximab tesirine delivers the DNA-cross-linking agent tesirine via CD19 binding and internalization; and CD19-directed chimeric antigen receptor T-cell therapy (CAR-T) products are engineered from autologous T cells. While CD19 expression is assessed at diagnosis, clinically relevant thresholds of CD19 expression-which may not be detectable with current routine methodologies-have not been defined and may vary between CD19-directed treatment modalities. Determining optimal treatment sequencing strategies with CD19-directed therapy has been hampered by the exclusion of patients with prior CD19-directed therapies from major clinical trials. Antigen escape, attributed to mechanisms including epitope loss and defective cell-surface trafficking of CD19, is an important cause of CAR-T failure. Limited data suggest that CD19 expression may be maintained after non-CAR-T CD19-directed therapy and retrospective analyses indicate that some patients with disease that relapses after CAR-T may benefit from subsequent CD19-directed therapy. To date, clinical evidence on the effect of anti-CD19 therapy prior to CAR-T is restricted to small case series. Prospective studies and detailed analyses to understand how pre- and post-treatment CD19 expression correlates with clinical responses to subsequent CD19-directed therapy are needed to fully maximize treatment strategies.

388 Prototyping a mobile phone application for Chimeric Antigen Receptor (CAR) T-cell therapy patient monitoring and data collection post-discharge

OBJECTIVES/GOALS: Research objectives include prototyping a mobile phone application that allows physicians to monitor CD19-directed CAR T-cell therapy patients remotely after discharge. This app will also enable standardized data collection across different centers that provide CAR-T cell therapy and allow for the harmonization of follow-up protocols. METHODS/STUDY POPULATION: Literature review and semi-structured interviews with patients, clinical coordinators, and other experts in the field will be used to determine what parameters must be included in the mobile application prototype to effectively monitor the side effects of CD19-directed CAR T-cell therapy. The mobile phone application will be designed using process mapping to integrate data from self-reporting and wearable technologies, including the Garmin smart watch. Figma will then be used to develop new screens based on an existing patient monitoring app for Allogeneic Stem Cell Transplant follow-up. Finally, a preliminary feasibility study will be conducted to collect feedback on the app prototype from CAR T-cell therapy patients, providers, and stakeholders. RESULTS/ANTICIPATED RESULTS: The anticipated results of this study include an app prototype that will include the functionalities required to monitor patients for adverse effects of CD19-directed CAR T-cell therapy. This will include the parameters that will be recorded or measured using a combination of self-reporting, a reliable body temperature sensor, and the Garmin watch which monitors basic vitals, activity, and sleep. Additional parameters may be added during the stakeholder co-design process. The app prototype will include a physician interface where doctors can monitor their patients and will be alerted if they require further physician assessment. It is expected that the app will provide standardized monitoring of patients when they are discharged from the hospital after receiving CAR T-cell therapy. DISCUSSION/SIGNIFICANCE: This app will allow physicians to monitor patients for general follow-up and adverse effects, including cytokine release syndrome and neurotoxicity. Future studies may utilize this app to develop best practices for harmonizing CAR-T follow-up protocols across Canada.

Abstract 46: Mechanisms and impact of bystander killing by CAR T cells

Abstract While CD19-directed chimeric antigen receptor (CAR) T cell therapy has improved outcomes of patients with relapsed/refractory diffuse large B cell lymphoma (r/r DLBCL), a majority will suffer disease relapse following CAR T cell infusion. Therefore, understanding mechanisms of CAR T cell killing is critical to enhance therapeutic efficacy. Cytolysis of CAR T cell targets presumably involves recognition of CD19 antigen by the CAR followed by activation of the granzyme/perforin axis. However, bystander elimination of CD19-negative lymphoma cells by CAR T cells has been reported, indicating that an alternative pathway may be required for optimal killing. Through in-depth phenotyping of a large panel of human DLBCLs and in vitro killing assays, we observed that CD19 expression levels on DLBCL cells and vulnerability to CAR T cell killing were weakly correlated. Conversely, cell surface expression of the death receptor, FAS, on DLBCL cells was strongly associated with susceptibility to CAR T cell killing. Although FAS expression across DLBCL cell lines varied, it could be broadly enhanced following exposure to IFNγ. Potent CAR T cell-mediated cytolysis of CD19-negative, Fas-positive murine DLBCL cells required the presence of CD19-positive lymphoma cells in the culture. CRISPR/Cas9 targeting was employed to delete FAS and/or CD19 in isogenic human DLBCL cells to generate CD19+FAS+, CD19+FAS−, CD19−FAS+, and CD19−FAS− subsets, which enabled us to define the extent to which CD19 engagement by the CAR was required to affect killing via FAS. When CAR T cells were co-cultured with equal numbers of the four gene-modified DLBCL cells described above, CD19+FAS+ DLBCL cells were killed most effectively, followed by CD19+FAS− DLBCL cells, and CD19−FAS+ DLBCL cells. Double-negative DLBCL cells were poorly killed. This result suggested that CD19 engagement by the CAR was required for optimal DLBCL cell killing via FAS, and that CD19 and FAS need not necessarily be engaged on the same target cell. Future studies will determine if Fas/FasL interactions can be exploited by overexpression of FasL in CAR T cells and examination of DLBCL killing in vitro and in vivo. Citation Format: Joanna Chorazeczewski, Lishi Xie, Xiufen Chen, Sidney Wang, Justin Kline. Mechanisms and impact of bystander killing by CAR T cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 46.

Abstract 5121: Next-generation immunocompetent and humanized neuroblastoma murine models for the discovery and validation of novel immunotherapies

Abstract The success of CD19-directed chimeric antigen receptor (CAR)-T cell therapy for ALL has yet to be matched in solid pediatric malignancies. Moreover, immune checkpoint blockade has shown limited benefit in pediatric cancer. Despite this unmet need, there is a lack of reliable preclinical models to facilitate novel target discovery, validate therapeutic benefit, anticipate on- or off-target toxicity, and understand mechanisms of resistance. Syngeneic murine model systems are a critical intermediate for preclinical translation, preserving the complex and heterogenous immune landscape and host-immunotherapy interactions. However, model interpretation and validity are limited as expression and function of murine targets and immune effector cells are not always conserved. We have developed a syngeneic immunocompetent C57BL/6 neuroblastoma system to study CAR efficacy, toxicity, and mechanisms of resistance, as well a variety of vaccination strategies. Specifically, we have built two murine CAR T constructs containing a 100% conserved antigen-directed scFv joined to orthologous murine TCR signaling machinery. In parallel, we engineered the murine neuroblastoma cell line 9464D to stably express surface antigen Gpc2 (Bosse, Cancer Cell 2017), or a novel chimeric single chain trimer of a 9mer peptide from intracellular oncoprotein PHOX2B discovered on HLA-A*24:02 (Yarmarkovich, Nature 2023) as Phox2b/A24*02/H2-kb to generate tumor-bearing B6 or B6-A24-Tg mice. We are currently using this system to demonstrate how vaccination approaches enhance the persistence and potency of CART directed to both targets and are extending our syngeneic murine constructs to additional TH-MYCN allograft models. To further study the innate and adaptive immune response to various therapeutics, we have developed peripheral blood mononuclear cell (PBMC) humanized models. Our autologous humanized PDX mouse models of neuroblastoma use immunocompromised NSG mice engrafted with a PDX and humanized with patient-matched PBMCs to evaluate personalized vaccines in vivo. We have shown the ability to stably engraft both lymphoid and myeloid populations in various human cytokine transgenic NSG variants (i.e. SGM3, Flt3L), allowing for T/B cell and APC crosstalk, thus providing a robust means to study targeted interventions. We are currently using this autologously humanized PDX model to test the ability of multivalent, personalized neoantigen vaccines developed specific to the neoantigen landscape of individual PDXs, with a focus on endogenous T cell responses of patient PBMC against their own PDX in vivo. Citation Format: Timothy T. Spear, Elisabeth Posthill, David Groff, Anna M. Giudice, Kristopher R. Bosse, Leyuan Ma, Stephen P. Schoenberger, John M. Maris. Next-generation immunocompetent and humanized neuroblastoma murine models for the discovery and validation of novel immunotherapies [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5121.

Abstract 3849: Frontline ibrutinib-based therapy enhances CART cell functions in patients with CLL: Analysis of the phase 3 randomized clinical trial ECOG-ACRIN E1912

Abstract Introduction: Despite the remarkable activity of CD19-directed chimeric antigen receptor T cell therapy (CART19), durable remissions remain low, especially in chronic lymphocytic leukemia (CLL). Ibrutinib is an oral irreversible inhibitor of Bruton’s tyrosine kinase and is a first line therapy for CLL. Preclinical and early clinical data indicate that ibrutinib plus CART19 may be synergistic through inhibition of IL2-inducible T cell kinase. To systematically study the effects of prior ibrutinib treatment on subsequent CART functions, we utilized blood samples from the pivotal clinical trial E1912 (NCT02048813). E1912 was a phase 3 randomized trial comparing treatment with ibrutinib/rituximab (IR) to fludarabine/cyclophosphamide/rituximab (FCR) in previously untreated patients with CLL, which led to the FDA approval of ibrutinib as a first-line therapy in CLL. Methods: We evaluated the ex vivo expansion and effector functions of T cells and CART19 generated from patients (n=12) with CLL progression following treatment with IR or FCR. We generated CART19 from longitudinal samples obtained at baseline (pretreatment), 6 months post-treatment, 12 months post-treatment, and disease progression. Isolated T cells were lentivirally transduced to express CD28- or 41BB-costimulated CAR19. To assess antigen specific killing and proliferation, untransduced T cells or CART19 were co-cultured at a 1:1 ratio with the CD19+ cell line, JeKo-1, as a surrogate for CLL cells. Results: Ex vivo T cell expansion increased from an average of 1.5-fold at baseline to 6.7-fold at 6 months, 11.6-fold at 12 months, and 16.9-fold at progression, following ibrutinib-based therapy (p = 0.02, 0.04, and 0.04, respectively). Improved T cell expansion was independent of disease burden (p = 0.89, 0.73, and 0.54 for expansion vs B cell count at 6 months, 12 months, and progression). T cell expansion significantly worsened following treatment with FCR-based therapy compared to ibrutinib-based therapy (0.6- vs 11.6-fold at 12 months and 0.9- vs 16.9-fold at progression; p = 0.031 and 0.039, respectively). Starting at 6 months post-IR, CART19 demonstrated improved antitumor activity and antigen-specific proliferation against JeKo-1. There was no significant difference in the expansion of 41BB- vs CD28-costimulated CART19 following ibrutinib treatment. However, 41BB-CART19 showed enhanced antigen-specific proliferation upon stimulation with JeKo-1 (p = 0.008, 0.02, and 0.02 at 6 months, 12 months, and progression). Conclusion: Our results indicate significant improvement in T cell expansion and CART19 cell functions in patients with CLL following frontline ibrutinib-based therapy, and worsening T cell functions after FCR treatment. Improvement in T cell functions is independent of malignant B cell eradication and is more significant in 41BB-costimulated CART19. Citation Format: Truc Ngoc Huynh, Victoria Wang, Tait Shanafelt, Elizabeth L. Siegler, Carli M. Stewart, Kun Yun, Long K. Mai, Olivia Sirpilla, James H. Girsch, Claudia Manriquez-Roman, Jennifer M. Feigin, Makena Rodriguez, Brooke L. Kimball, Hong Xia, Reona L. Sakemura, Ismail Can, Omar L. Gutierrez-Ruiz, Ekene J. Ogbodo, Erin E. Tapper, Lionel A. Fonkoua, Mehrdad T. Hefazi, Michael W. Ruff, Sameer Parikh, Neil E. Kay, Saad J. Kenderian. Frontline ibrutinib-based therapy enhances CART cell functions in patients with CLL: Analysis of the phase 3 randomized clinical trial ECOG-ACRIN E1912 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3849.

The Implementation of Chimeric Antigen Receptor (CAR) T-cell Therapy in Pediatric Patients: Where Did We Come From, Where Are We Now, and Where are We Going?

CD19-directed Chimeric Antigen Receptor (CAR) T-cell therapy has revolutionized the treatment of patients with B-cell acute lymphoblastic leukemia (B-ALL). Somewhat uniquely among oncologic clinical trials, early clinical development occurred simultaneously in both children and adults. In subsequent years however, the larger number of adult patients with relapsed/refractory (r/r) malignancies has led to accelerated development of multiple CAR T-cell products that target a variety of malignancies, resulting in six currently FDA-approved for adult patients. By comparison, only a single CAR-T cell therapy is approved by the FDA for pediatric patients: tisagenlecleucel, which is approved for patients  25 years with refractory B-cell precursor ALL, or B-cell ALL in second or later relapse. Tisagenlecleucel is also under evaluation in pediatric patients with relapsed/refractory B-cell non-Hodgkin lymphoma, but is not yet been approved for this indication. All the other FDA-approved CD19-directed CAR-T cell therapies available for adult patients (axicabtagene ciloleucel, brexucabtagene autoleucel, and lisocabtagene maraleucel) are currently under investigations among children, with preliminary results available in some cases. As the volume and complexity of data continue to grow, so too does the necessity of rapid assimilation and implementation of those data. This is particularly true when considering “atypical” situations, e.g. those arising when patients do not precisely conform to the profile of those included in pivotal clinical trials, or when alternative treatment options (e.g. hematopoietic stem cell transplantation (HSCT) or bispecific T-cell engagers (BITEs)) are also available. We have therefore developed a relevant summary of the currently available literature pertaining to the use of CD19-directed CAR-T cell therapies in pediatric patients, and sought to provide guidance for clinicians seeking additional data about specific clinical situations.

Reducing and controlling metabolic active tumor volume prior to CAR T-cell infusion can improve survival outcomes in patients with large B-cell lymphoma

Bridging therapy before CD19-directed chimeric antigen receptor (CAR) T-cell infusion is frequently applied in patients with relapsed or refractory Large B-cell lymphoma (r/r LBCL). This study aimed to assess the influence of quantified MATV and MATV-dynamics, between pre-apheresis (baseline) and pre-lymphodepleting chemotherapy (pre-LD) MATV, on CAR T-cell outcomes and toxicities in patients with r/r LBCL. MATVs were calculated semi-automatically at baseline (n = 74) and pre-LD (n = 68) in patients with r/r LBCL who received axicabtagene ciloleucel. At baseline, patients with a low MATV (< 190 cc) had a better time to progression (TTP) and overall survival (OS) compared to high MATV patients (p < 0.001). High MATV patients who remained stable or reduced upon bridging therapy showed a significant improvement in TTP (p = 0.041) and OS (p = 0.015), compared to patients with a high pre-LD MATV (> 480 cc). Furthermore, high MATV baseline was associated with severe cytokine release syndrome (CRS, p = 0.001). In conclusion, patients with low baseline MATV had the best TTP/OS and effective reduction or controlling MATV during bridging improved survival outcomes in patients with a high baseline MATV, providing rationale for the use of more aggressive bridging regimens.

Bendamustine as Lymphodepletion for Brexucabtagene Autoleucel Therapy of Mantle Cell Lymphoma

Brexucabtagene autoleucel (brexu-cel) is an autologous CD19-directed chimeric antigen receptor (CAR) T-cell therapy approved for treatment of relapsed/refractory mantle cell lymphoma (MCL). During a fludarabine shortage, we used bendamustine as an alternative to standard cyclophosphamide/fludarabine (cy/flu) lymphodepletion (LD) prior to brexu-cel. We assessed MCL patient outcomes as well as CAR T-cell expansion and persistence after brexu-cel following bendamustine or cy/flu LD at our center. This was a retrospective single institution study that utilized prospectively banked blood and tissue samples. Clinical efficacy was assessed by 2014 Lugano guidelines. CAR T-cell expansion and persistence in peripheral blood were assessed on day 7 and at ≥month 6 for patients with available samples. Seventeen patients received bendamustine and 5 received cy/flu. For the bendamustine cohort, 14 (82%) received bridging therapy and 4 (24%) had CNS involvement. Fifteen patients (88%) developed CRS with 4 (24%) ≥grade 3 events. Six (35%) patients developed ICANS with 4 (24%) events ≥grade 3. No patient had ≥grade 3 cytopenias at day 90. Best objective (BOR) and complete response (CRR) rates were 82% and 65%, respectively. At 24.5 months median follow-up, 12-month progression-free survival (PFS) was 45%, 24-month PFS was 25%, and median duration of response was 19 months. Median OS was not reached. BOR was 25% (1/4) for patients with CNS involvement. CAR transgene expansion after bendamustine LD was observed on day 7 in all (4/4) patients tested and persisted at ≥6 months (2/2), regardless of response. Bendamustine LD before brexu-cel for MCL is feasible and safe with a lower frequency and shorter duration of cytopenias than reported for cy/flu. Both CAR T-cell expansion and persistence were observed after bendamustine LD. Outcomes appear comparable to the real world outcomes reported with cy/flu LD.

Chimeric antigen receptor-T cell therapy shows similar efficacy and toxicity in patients with diffuse large B-cell lymphoma aged 70 and older compared to younger patients: A multicenter cohort study.

CD19-directed chimeric antigen receptor (CAR)-T cell therapy has become a standard treatment for relapsed/refractory diffuse large B-cell lymphoma (r/r DLBCL). While the benefits of CAR-T cell treatment are clear in the general patient population, there remains a relative scarcity of real-world evidence regarding its efficacy and toxicity in patients (pts) aged ≥70 years with DLBCL. We conducted a multicenter retrospective analysis including 172 r/r DLBCL pts with CAR-T cell treatment, axicabtagene ciloleucel or tisagenlecleucel, between 2019 and 2023 at three tertiary centers. Pts were grouped by age at CAR-T infusion (<70 vs. ≥70 years). Subsequently, descriptive and survival analyses, including propensity score matching, were performed to compare outcomes between both age groups. We identified 109 pts aged <70 and 63 pts aged ≥70 years. Overall response rates for both age groups were comparable (77.7% vs. 78.3%; p = 0.63). With a median follow-up of 8.3 months, median progression-free survival was 10.2 months (95% confidence interval [CI]: 6.5-21.8) and 11.1 months (95% CI: 4.9-NR) (p = 0.93) for both cohorts. Median overall survival reached 21.8 months (95% CI: 11.8-NR) and 34.4 months (95% CI: 10.1-NR) (p = 0.97), respectively. No significant differences in the incidence of cytokine release syndrome (p = 0.53) or grade ≥3 neurotoxicity (p = 0.56) were observed. Relapse and nonrelapse mortality were not significantly different between both groups. Our findings provide additional support that CAR-T cell therapy is feasible and effective in patients with r/r DLBCL aged 70 years or older, demonstrating outcomes comparable to those observed in younger patients. CAR-T cell therapy should be not withheld for elderly patients with r/r DLBCL.

Enhancing chimeric antigen receptor T cell therapy by modulating the p53 signaling network with Δ133p53α

Chimeric antigen receptor (CAR) T cell dysfunction is a major barrier to achieving lasting remission in hematologic cancers, especially in chronic lymphocytic leukemia (CLL). We have shown previously that Δ133p53α, an endogenous isoform of the human TP53 gene, decreases in expression with age in human T cells, and that reconstitution of Δ133p53α in poorly functional T cells can rescue proliferation [A. M. Mondal et al., J. Clin. Invest. 123, 5247-5257 (2013)]. Although Δ133p53α lacks a transactivation domain, it can form heterooligomers with full-length p53 and modulate the p53-mediated stress response [I. Horikawa et al., Cell Death Differ. 24, 1017-1028 (2017)]. Here, we show that constitutive expression of Δ133p53α potentiates the anti-tumor activity of CD19-directed CAR T cells and limits dysfunction under conditions of high tumor burden and metabolic stress. We demonstrate that Δ133p53α-expressing CAR T cells exhibit a robust metabolic phenotype, maintaining the ability to execute effector functions and continue proliferating under nutrient-limiting conditions, in part due to upregulation of critical biosynthetic processes and improved mitochondrial function. Importantly, we show that our strategy to constitutively express Δ133p53α improves the anti-tumor efficacy of CAR T cells generated from CLL patients that previously failed CAR T cell therapy. More broadly, our results point to the potential role of the p53-mediated stress response in limiting the prolonged antitumor functions required for complete tumor clearance in patients with high disease burden, suggesting that modulation of the p53 signaling network with Δ133p53α may represent a translationally viable strategy for improving CAR T cell therapy.

Reinfusion of CD19 CAR T cells for relapse prevention and treatment in children with acute lymphoblastic leukemia

AbstractRelapse after CD19-directed chimeric antigen receptor (CAR)–modified T cells remains a substantial challenge. Short CAR T-cell persistence contributes to relapse risk, necessitating novel approaches to prolong durability. CAR T-cell reinfusion (CARTr) represents a potential strategy to reduce the risk of or treat relapsed disease after initial CAR T-cell infusion (CARTi). We conducted a retrospective review of reinfusion of murine (CTL019) or humanized (huCART19) anti–CD19/4-1BB CAR T cells across 3 clinical trials or commercial tisagenlecleucel for relapse prevention (peripheral B-cell recovery [BCR] or marrow hematogones ≤6 months after CARTi), minimal residual disease (MRD) or relapse, or nonresponse to CARTi. The primary endpoint was complete response (CR) at day 28 after CARTr, defined as complete remission with B-cell aplasia. Of 262 primary treatments, 81 were followed by ≥1 reinfusion (investigational CTL019, n = 44; huCART19, n = 26; tisagenlecleucel, n = 11), representing 79 patients. Of 63 reinfusions for relapse prevention, 52% achieved CR (BCR, 15/40 [38%]; hematogones, 18/23 [78%]). Lymphodepletion was associated with response to CARTr for BCR (odds ratio [OR], 33.57; P = .015) but not hematogones (OR, 0.30; P = .291). The cumulative incidence of relapse was 29% at 24 months for CR vs 61% for nonresponse to CARTr (P = .259). For MRD/relapse, CR rate to CARTr was 50% (5/10), but 0/8 for nonresponse to CARTi. Toxicity was generally mild, with the only grade ≥3 cytokine release syndrome (n = 6) or neurotoxicity (n = 1) observed in MRD/relapse treatment. Reinfusion of CTL019/tisagenlecleucel or huCART19 is safe, may reduce relapse risk in a subset of patients, and can reinduce remission in CD19+ relapse.

Monocytes in leukapheresis products affect the outcome of CD19–targeted CAR T-cell therapy in patients with lymphoma

AbstractCD19–directed chimeric antigen receptor (CAR) T cells can induce durable remissions in relapsed/refractory large B-cell lymphomas (R/R LBCLs), but 60% of patients do not respond or relapse. Biological mechanisms explaining lack of response are emerging, but they are largely unsuccessful in predicting disease response at the patient level. Additionally, to maximize the cost-effectiveness of CAR T-cell therapy, biomarkers able to predict response and survival before CAR T-cell manufacturing would be desirable. We performed transcriptomic and functional evaluations of leukapheresis products in 95 patients with R/R LBCL enrolled in a prospective observational study, to identify correlates of response and survival to tisagenlecleucel and axicabtagene ciloleucel. A signature composed of 4 myeloid genes expressed by T cells isolated from leukapheresis products is able to identify patients with a very short progression-free survival (PFS), highlighting the impact of monocytes in CAR T-cell therapy response. Accordingly, response and PFS were also negatively influenced by high circulating absolute monocyte counts at the time of leukapheresis. The combined evaluation of peripheral blood monocytes at the time of leukapheresis and the 4-gene signature represents a novel tool to identify patients with R/R LBCL at very high risk of progression after CAR T-cell therapy and could be used to plan trials evaluating CAR T cells vs other novel treatments or allogeneic CAR T cells. However, it also highlights the need to incorporate monocyte depletion strategies for better CAR T production.

Real World Outcomes for AYA Patients with Relapsed/Refractory B-Cell ALL Receiving CD19-Directed CAR T-Cell Therapy

Real World Outcomes for AYA Patients with Relapsed/Refractory B-Cell ALL Receiving CD19-Directed CAR T-Cell Therapy

Axicabtagene Ciloleucel versus Tisagenlecleucel for Relapsed or Refractory Large B Cell Lymphoma: A Systematic Review and Meta-Analysis

Axicabtagene ciloleucel (axi-cel) and tisagenlecleucel (tisa-cel) are CD19-directed chimeric antigen receptor T cell (CAR-T) therapies approved for relapsed/refractory aggressive large B cell lymphoma (LBCL). Significant costs and complex manufacturing underscore the importance of evidence-based counseling regarding the outcomes of these treatments. With the aim of examining the efficacy and safety of axi-cel versus tisa-cel in patients with relapsed/refractory aggressive LBCL, we performed a systematic literature search of comparative studies evaluating outcomes in relapsed/refractory aggressive LBCL after treatment with axi-cel or tisa-cel. We calculated odds ratios (ORs) and 95% confidence intervals (CIs) for response, progression-free survival (PFS), overall survival (OS), cytokine release syndrome (CRS), immune effector cell-associated neurotoxicity syndrome (ICANS), and hematotoxicity. Meta-analysis and meta-regression were used to generate summary statistics. A total of 2372 participants were included in the 8 studies in our analysis. The dropout rate between apheresis and infusion was 13% for axi-cel versus 18% for tisa-cel, and the median time from apheresis to infusion was 32 days versus 45 days. Axi-cel showed higher odds for a complete response (OR, 1.65; P < .001) and was associated with higher odds for PFS at 1 year after infusion (OR, .60; P < .001). OS appeared to be improved with axi-cel (OR, .84; 95% CI, .68 to 1.02; P = .08), whereas the cumulative incidence of nonrelapse mortality (NRM) was 11.5% for axi-cel versus 3.7% for tisa-cel (P = .002). The main predictors for survival were lactate dehydrogenase level, Eastern Cooperative Oncology Group Performance Status, and response to bridging, and axi-cel maintained superior efficacy even in elderly patients. In terms of safety, axi-cel was associated with significantly higher odds of any-grade CRS (OR, 3.23; P < .001), but not of grade ≥3 CRS (P = .92). Axi-cel was associated with significantly higher odds of severe ICANS grade ≥3 (OR, 4.03; P < .001). In terms of hematotoxicity, axi-cel was significantly associated with higher odds of severe neutropenia at 1 month after infusion (OR, 2.06; P = .003). As a result, axi-cel was associated with significantly greater resource utilization, including prolonged hospital stay, more frequent intensive care admission, and use of agents such as tocilizumab for toxicity management. We provide strong evidence of the greater efficacy of axi-cel versus tisa-cel in relapsed/refractory aggressive LBCL. The higher toxicity and NRM seen with axi-cel might not counterbalance the overall results, highlighting the need for timely intervention and careful selection of patients, balancing resource utilization and clinical benefit.

Transforming CLL Management with Immunotherapy: Investigating the Potential of CAR T-Cells and Bispecific Antibodies

Immunotherapies, such as chimeric antigen receptor (CAR) T-cell therapy and bispecific antibodies or T-cell engagers, have revolutionized the treatment landscape for various B-cell malignancies, including B-acute lymphoblastic leukemia and many non-Hodgkin lymphomas. Despite their significant impact on these malignancies, their application in chronic lymphocytic leukemia (CLL) management is still largely under investigation. Although the initial success of CD19-directed CAR T-cell therapy was observed in three multiply relapsed CLL patients, with two of them surviving over 10 years without relapse, recent CAR T-cell therapy trials in CLL have shown reduced response rates compared to their efficacy in other B-cell malignancies. One of the challenges with using immunotherapy in CLL is the compromised T-cell fitness from persistent CLL-related antigenic stimulation, and an immunosuppressive tumor microenvironment (TME). These challenges underscore a critical gap in therapeutic options for CLL patients intolerant or resistant to current therapies, emphasizing the imperative role of effective immunotherapy. Encouragingly, innovative strategies are emerging to overcome these challenges. These include integrating synergistic agents like ibrutinib to enhance CAR T-cell function and persistence, and engineering newer CAR T-cell constructs targeting diverse antigens or employing dual-targeting approaches. Bispecific antibodies are an exciting "off-the-shelf" prospect for these patients, with their investigation in CLL currently entering the realm of clinical trials. Additionally, the development of allogeneic CAR T-cells and natural killer (NK) cells from healthy donors presents a promising solution to address the diminished T-cell fitness observed in CLL patients. This comprehensive review delves into the latest insights regarding the role of immunotherapy in CLL, the complex landscape of resistance mechanisms, and a spectrum of innovative approaches to surmount therapeutic challenges.

Determinants of outcomes and advances in CD19-directed chimeric antigen receptor therapy for B-cell acute lymphoblastic leukemia.

Relapsed and refractory B-cell acute lymphoblastic leukemia (B-ALL) is an aggressive B-cell neoplasm associated with poor outcomes. Conventional multiagent chemotherapy and bispecific antibody therapy may induce remission; however, relapse rates remain high and overall survival is poor. Chimeric antigen receptor T-cell (CAR-T) therapy provides durable, deep complete remission, and long-term cures in relapsed and refractory B-ALL. However, with this new treatment modality, 10%-30% of patients do not achieve remission, and over 50% experience relapse after therapy. Currently, there are two approved CD19-specific CAR-T cell constructs in B-ALL, Tisagenlecleucel and Brexucabtagene Autoleucel by the United States Food and Drug Administration, and the European Medicines Agency (EMA). In this review, we discuss patients, disease, and CAR-T predictors of outcomes in B-ALL. We describe the two approved CD19-directed CAR-T cell products, review the current literature, and discuss factors associated with high risks of therapy failure and future direction in CAR-T cell therapy for B-ALL.

Therapeutic options for large B-cell lymphoma relapsing after CD19-directed CAR T-cell therapy.

In recent years, chimeric antigen receptor T-cell therapy (CART) has revolutionized the treatment landscape for large B cell lymphoma (LBCL), demonstrating remarkable efficacy and ushering a new era of therapeutic possibilities. However, a subset of patients may not achieve the desired response with CAR T. This review examines strategies aimed at optimizing outcomes for patients who relapse or progress after CAR T. Available data on utilization of CD19-directed monoclonal antibodies and antibody drug conjugates have shown limited efficacy in this setting. Moreover, bispecific antibodies have also emerged as an alternative therapy in relapsed and or refractory LBCL, but long-term follow up treated cases post-CAR T failure are lacking. Several observational studies have shown efficacy of allogeneic hematopoietic cell transplantation, but attainment of a complete remission prior to allografting is a prerequisite to achieve durable remissions. As we navigate the intricate landscape of treatment of post CAR T failure, it becomes evident that this represents a therapeutic challenge which necessitates a multifaceted approach.