CAR T-Cell Persistence Correlates with Improved Outcome in Patients with B-Cell Lymphoma

Elevated CD10- neutrophils correlate with non-response and poor prognosis of CD19 CAR T-cell therapy for B-cell acute lymphoblastic leukemia

BACKGROUND

The primary challenges in CD19-specific chimeric antigen receptor T-cell (CD19 CAR T) therapy for patients with refractory/relapsed B-cell acute lymphoblastic leukemia (r/r B-ALL) are non-response and relapse; it is urgent to reveal these mechanisms. Neutrophils play a critical role in the immunosuppressive tumor microenvironment (TME), which can hinder CAR T efficacy. Our previous research identified a subset of immunosuppressive neutrophils with a special phenotype (CD14-CD10-CD45-HLA-DR-SSC++, termed CD10- neuts), which suppress T cell function. Therefore, we speculate that CD10- neuts may also influence CAR T efficacy, and this study aims to clinically validate this hypothesis.

METHODS

We enrolled 44 patients with r/r B-ALL undergoing CD19 CAR T therapy and 47 healthy controls (HCs). Peripheral blood samples were obtained prior to CAR T infusion to detect CD10- neuts levels by flow cytometry. Key parameters included the percentage of CD10- neuts in neutrophils (CD10- neuts/neutrophils), in all nucleated cells (CD10- neuts/nucleated cells), and the absolute count of CD10- neuts. We analyzed the correlations between these indicators and therapeutic response, relapse-free survival (RFS), overall survival (OS), and CAR T cell persistence time.

RESULTS

CD10- neuts levels were significantly elevated in patients with r/r B-ALL compared to HCs. Additionally, non-responding patients exhibited higher CD10- neuts levels than those in remission. Specifically, CD10- neuts/neutrophils, CD10- neuts/nucleated cells, and absolute CD10- neuts count were 64.44% vs. 25.43% (p = 0.004), 28.61% vs. 9.81% (p = 0.018), and 766.1/μL vs. 152.9/μL (p = 0.04), respectively. Among these indices, only CD10- neuts/neutrophils emerged as an independent risk factor for CAR T response (OR = 19.8, p = 0.013), relapse (HR = 4.704, p = 0.004), and survival (HR = 6.417, p = 0.001). Patients with CD10- neuts/neutrophils ≥ 21.57% demonstrated significantly shorter RFS and OS compared to those with lower levels (p = 0.001; p = 0.0002). Furthermore, CD10- neuts/neutrophils were negatively correlated with the persistence time of CAR T cells.

CONCLUSIONS

As one of the key factors in the TME, abnormally elevated CD10- neuts correlate with CAR T therapy resistance. Targeting these neutrophils could enhance the effectiveness of CAR T treatment.

Longitudinal analysis of lentiviral and retroviral chimeric antigen receptors' integration sites reveals distinct clonal evolutionary patterns

T-cell malignancies following chimeric antigen receptor (CAR) therapies are partly related to insertional mutagenesis, but the longitudinal evolution of CAR-integration sites (IS) remains understudied. We performed an IS analysis in blood from three tisagenlecleucel (lentiviral), one axicabtagene-ciloleucel and one brexucabtagene-autoleucel (gammaretrovirals) patient at peak expansion and 1-year follow-up. All were complete responders. Peak expansion IS patterns were vector dependent: lentiviral CAR integrated mostly in introns and gammaretrovirals in intergenic regions, closer to transcription start sites. At 1-year post-infusion, lentiviral CAR showed no major clonal proliferation. Gammaretroviral CARs had divergent outcomes: no detectable CAR (axicabtagene-ciloleucel) or low-level oligoclonal persistence (brexucabtagene-autoleucel). Whether this latter evolution is at risk of further CAR malignancies needs further investigations.

Dissecting the role of CAR signaling architectures on T cell activation and persistence using pooled screens and single-cell sequencing

Chimeric antigen receptor (CAR) T cells offer a promising cancer treatment, yet challenges such as limited T cell persistence hinder efficacy. Given its critical role in modulating T cell responses, it is crucial to understand how the CAR signaling architecture influences T cell function. Here, we designed a combinatorial CAR signaling domain library and performed repeated antigen stimulation assays, pooled screens, and single-cell sequencing to systematically investigate the impact of modifying CAR signaling domains on T cell activation and persistence. Our data reveal the predominant influence of membrane-proximal domains in driving T cell phenotype. Notably, CD40 costimulation was crucial for fostering robust and lasting T cell responses. Furthermore, we correlated in vitro generated CAR T cell phenotypes with clinical outcomes in patients treated with CAR T therapy, establishing the foundation for a clinically informed screening approach. This work deepens our understanding of CAR T cell biology and may guide future CAR engineering efforts.

CD4 T cell depletion increases memory differentiation of endogenous and CAR T cells and enhances the efficacy of Super2 and IL-33-armored CAR T cells against solid tumors

BACKGROUND

Responsiveness to chimeric antigen receptor (CAR) T cell therapy correlates with CAR T cell expansion and persistence in vivo. Multiple strategies improve persistence by increasing stem-like properties or sustaining CAR T cell activity with combination therapies. Here, we describe the intrinsic ability of CAR T cells to differentiate into memory T cells, the effect of cytokine armoring, and neoadjuvant CD4 depletion therapy on CAR and tumor-specific endogenous memory T cells.

METHODS

TRP1-specific or NKG2D CAR T cells alone or with Super2+IL-33 (S233) armoring and/or CD4 depletion were evaluated in immunocompetent B16F10 melanoma or MC38 colon cell carcinoma models without preconditioning. We characterized CAR and endogenous tumor-specific memory T cell precursors, establishment of circulating (TCIRC) and resident (TRM) memory T cell subsets, and ability to protect against secondary tumors.

RESULTS

TRP1-specific or NKG2D CAR T cells had no effect on primary tumor growth in immunocompetent mice unless they were combined with S233 armoring or CD4 depletion. Unarmored CAR T cells expressed a stem-like phenotype in the tumor-draining lymph node and differentiated into CAR TCIRC memory cells in lymphoid organs and CAR TRM cells in the skin. In contrast, S233-armored CAR T cells exhibited an activated effector phenotype and differentiated inefficiently into CAR effector and central memory T cells. Combining CD4 therapy with unarmored CAR T cells increased CAR TCIRC and TRM memory T cells. Either CD4 depletion therapy or S233-armored CAR T cells induced activation of tumor-specific endogenous T cells that differentiated into both TCIRC and TRM memory T cells. CD4 depletion and S233-armored CAR T cell combination therapy synergized to increase endogenous memory T cells.

CONCLUSIONS

Unarmored TRP-1-specific or NKG2D CAR T cells have intrinsic stem-like properties and differentiate into memory T cell subsets but are non-protective against primary or secondary tumors. S233 cytokine armoring alone or with CD4 depletion improved effector responses but limited CAR memory T cell generation. S233-armored CAR T cells or CD4 depletion therapy induced endogenous tumor-specific TCIRC and TRM T cells, but the combination potentiated endogenous memory T cell generation and resulted in improved protection against B16F10 rechallenge.

Late-onset relapsing neurotoxicity after Brexucabtagene autoleucel associated with high chimeric antigen receptor T cells in cerebrospinal fluid

BACKGROUND AIMS

Mounting evidence suggests that persistent cell expansion is the main driver for both efficacy and toxicity of chimeric antigen receptor (CAR) T-cell therapy. Hereby, we describe a case of delayed recurrent neurotoxicity associated with late CAR T-cells re-expansion.

CASE DESCRIPTION

A 44-year-old man suffering from mantle cell lymphoma received brexu-cel. After infusion, he developed grade 2 cytokine release syndrome. On day +11, grade 3 neurotoxicity was reported and high-dose methylprednisolone was started with a complete resolution of neurological manifestations. On day +30, he experienced a late-onset CAR T-cell toxicity associated with CAR T-cell re-expansion. The patient was treated with tocilizumab and dexamethasone, with resolution of symptoms. On day +58, he was readmitted for new onset of neurotoxicity. Notably, a new CAR T-cell expansion was observed, with an unexpectedly elevated cerebrospinal fluid/blood ratio. The patient was promptly treated with dexamethasone and then escalated to high-dose methylprednisolone and anakinra, with resolution of his neurologic condition noted.

CONCLUSIONS

CAR T-cell-related neurotoxicity usually has an early monophasic course. To our knowledge, this is the first case of late-onset, recurrent neurotoxicity. Moreover, an elevated level of cerebrospinal fluid CAR T cells was observed, which may suggest that the delayed neurotoxicity was primarily caused by the brain infiltration of CAR T cells rather than driven by cytokine-mediated neuroinflammation.

The Role of Radiotherapy in Lymphoma Patients Undergoing CAR T Therapy: Past, Present, and Future

Chimeric antigen receptor (CAR) T-cell receptor therapy has transformed outcomes for patients with relapsed and refractory diffuse large B-cell lymphoma (R/R DLBCL). It is currently approved in the third line for all patients and in the second line for early relapsed or primary refractory disease. Although CAR T cell therapy offers the potential for improved outcomes, its use may also include logistical delays related to referral, medical, social, and financial clearance as well as manufacturing time; more than half of patients experience disease recurrence or progression while awaiting CAR T infusion. Bridging radiotherapy, defined as radiation delivered between the decision to pursue CAR T and infusion of CAR T cells, has become an attractive option for patients who would benefit from local disease control or palliation of symptoms. Additionally, patterns of failure analyses have revealed a dominant role of local disease progression, which has fueled investigations on bridging and early salvage radiation to improve long-term outcomes in patients, particularly those with localized or high-risk disease. Several potential mechanisms by which radiation therapy may improve CAR T efficacy have been proposed that include cytoreduction, tumor debulking, neutralization of immunosuppressive hypoxic and acidic tumor microenvironments, and immunologic and pro-apoptotic synergy between radiation and CAR T. Prospective clinical trials and translational work are ongoing and are needed to inform our conceptual understanding of potential mechanisms by which radiation therapy may improve CAR T efficacy and toxicity, identify which patients may be most likely to benefit, and confirm proposed clinical benefits.

Comprehensive analysis of the efficacy and safety of CAR T-cell therapy in patients with relapsed or refractory B-cell acute lymphoblastic leukaemia: a systematic review and meta-analysis

BACKGROUND

Relapse/refractory B-cell acute lymphoblastic leukaemia (r/r B-ALL) represents paediatric cancer with a challenging prognosis. CAR T-cell treatment, considered an advanced treatment, remains controversial due to high relapse rates and adverse events. This study assessed the efficacy and safety of CAR T-cell therapy for r/r B-ALL.

METHODS

The literature search was performed on four databases. Efficacy parameters included minimal residual disease negative complete remission (MRD-CR) and relapse rate (RR). Safety parameters constituted cytokine release syndrome (CRS) and immune effector cell-associated neurotoxicity syndrome (ICANS).

RESULTS

Anti-CD22 showed superior efficacy with the highest MRD-CR event rate and lowest RR, compared to anti-CD19. Combining CAR T-cell therapy with haploidentical stem cell transplantation improved RR. Safety-wise, bispecific anti-CD19/22 had the lowest CRS rate, and anti-CD22 showed the fewest ICANS. Analysis of the costimulatory receptors showed that adding CD28ζ to anti-CD19 CAR T-cell demonstrated superior efficacy in reducing relapses with favorable safety profiles.

CONCLUSION

Choosing a more efficacious and safer CAR T-cell treatment is crucial for improving overall survival in acute leukaemia. Beyond the promising anti-CD22 CAR T-cell, exploring costimulatory domains and new CD targets could enhance treatment effectiveness for r/r B-ALL.

Systemic toxicity of CAR-T therapy and potential monitoring indicators for toxicity prevention

Malignant tumors of the hematologic system have a high degree of malignancy and high mortality rates. Chimeric antigen receptor T cell (CAR-T) therapy has become an important option for patients with relapsed/refractory tumors, showing astonishing therapeutic effects and thus, it has brought new hope to the treatment of malignant tumors of the hematologic system. Despite the significant therapeutic effects of CAR-T, its toxic reactions, such as Cytokine Release Syndrome (CRS) and Immune Effector Cell-Associated Neurotoxicity Syndrome (ICANS), cannot be ignored since they can cause damage to multiple systems, including the cardiovascular system. We summarize biomarkers related to prediction, diagnosis, therapeutic efficacy, and prognosis, further exploring potential monitoring indicators for toxicity prevention. This review aims to summarize the effects of CAR-T therapy on the cardiovascular, hematologic, and nervous systems, as well as potential biomarkers, and to explore potential monitoring indicators for preventing toxicity, thereby providing references for clinical regulation and assessment of therapeutic effects.

A Comprehensive ddPCR Strategy for Sensitive and Reliable Monitoring of CAR-T Cell Kinetics in Clinical Applications

In this study, we present the design, implementation, and successful use of digital droplet PCR (ddPCR) for the monitoring of chimeric antigen receptor T-cell (CAR-T) expansion in patients with B-cell malignancies treated with different CAR-T products at our clinical center. Initially, we designed a specific and highly sensitive ddPCR assay targeting the junction between the 4-1BB and CD3ζ domains of tisa-cel, normalized with RPP30, and validated it using blood samples from the first tisa-cel-treated patient in Switzerland. We further compared this assay with a published qPCR (quantitative real-time PCR) design. Both assays showed reliable quantification of CAR-T copies down to 20 copies/µg DNA. The reproducibility and precision were confirmed through extensive testing and inter-laboratory comparisons. With the introduction of other CAR-T products, we also developed a corresponding ddPCR assay targeting axi-cel and brexu-cel, demonstrating high specificity and sensitivity with a limit of detection of 20 copies/µg DNA. These assays are suitable for CAR-T copy number quantification across multiple sample types, including peripheral blood, bone marrow, and lymph node biopsy material, showing robust performance and indicating the presence of CAR-T cells not only in the blood but also in target tissues. Longitudinal monitoring of CAR-T cell kinetics in 141 patients treated with tisa-cel, axi-cel, or brexu-cel revealed significant expansion and long-term persistence. Peak expansion correlated with clinical outcomes and adverse effects, as is now well known. Additionally, we quantified the CAR-T mRNA expression, showing a high correlation with DNA copy numbers and confirming active transgene expression. Our results highlight the quality of ddPCR for CAR-T monitoring, providing a sensitive, precise, and reproducible method suitable for clinical applications. This approach can be adapted for future CAR-T products and will support the monitoring and the management of CAR-T cell therapies.

The Spectrum of CAR Cellular Effectors: Modes of Action in Anti-Tumor Immunity

Chimeric antigen receptor-T cells have spearheaded the field of adoptive cell therapy and have shown remarkable results in treating hematological neoplasia. Because of the different biology of solid tumors compared to hematological tumors, response rates of CAR-T cells could not be transferred to solid entities yet. CAR engineering has added co-stimulatory domains, transgenic cytokines and switch receptors to improve performance and persistence in a hostile tumor microenvironment, but because of the inherent cell type limitations of CAR-T cells, including HLA incompatibility, toxicities (cytokine release syndrome, neurotoxicity) and high costs due to the logistically challenging preparation process for autologous cells, the use of alternative immune cells is gaining traction. NK cells and γδ T cells that do not need HLA compatibility or macrophages and dendritic cells with additional properties such as phagocytosis or antigen presentation are increasingly seen as cellular vehicles with potential for application. As these cells possess distinct properties, clinicians and researchers need a thorough understanding of their peculiarities and commonalities. This review will compare these different cell types and their specific modes of action seen upon CAR activation.

Fueling CARs: metabolic strategies to enhance CAR T-cell therapy

CAR T cells are widely applied for relapsed hematological cancer patients. With six approved cell therapies, for Multiple Myeloma and other B-cell malignancies, new insights emerge. Profound evidence shows that patients who fail CAR T-cell therapy have, aside from antigen escape, a more glycolytic and weakened metabolism in their CAR T cells, accompanied by a short lifespan. Recent advances show that CAR T cells can be metabolically engineered towards oxidative phosphorylation, which increases their longevity via epigenetic and phenotypical changes. In this review we elucidate various strategies to rewire their metabolism, including the design of the CAR construct, co-stimulus choice, genetic modifications of metabolic genes, and pharmacological interventions. We discuss their potential to enhance CAR T-cell functioning and persistence through memory imprinting, thereby improving outcomes. Furthermore, we link the pharmacological treatments with their anti-cancer properties in hematological malignancies to ultimately suggest novel combination strategies.

Role of radiation in chimeric antigen receptor T-cell therapy for patients with relapsed/refractory non-Hodgkin lymphoma: Current studies and future prospects

Chimeric antigen receptor T-cell (CAR-T) therapy has revolutionized the treatment approach for patients with relapsed/refractory non-Hodgkin lymphoma (R/R NHL). However, the long-term prognosis has been discouraging. Moreover, the urgent resolution of two critical issues is necessary: minimize tumor burden before CAR-T infusion and control fatal toxicities post CAR-T therapy. By combining radiotherapy (RT), the safety and efficacy of CAR-T can be improved. RT can serve as bridging therapy, reducing the tumor burden before CAR-T infusion, thus enabling safe and successful CAR-T infusion, and as salvage therapy in cases of CAR-T therapy failure. This review aims to discuss the current evidence supporting the use of RT in CAR-T therapy for patients with R/R NHL. Although most studies have shown a positive role of RT in combined modality treatments for patients undergoing CAR-T therapy, the synergy gained from these remains uncertain. Furthermore, the optimal dose/fraction and radiation response require further investigation.

Effects of Cannabidiol on the Functions of Chimeric Antigen Receptor T Cells in Hematologic Malignancies

Introduction: CD19-chimeric antigen receptor (CAR) T cell therapy is a promising immunotherapy for cancer treatment that has shown remarkable clinical responses, leading to approval by the FDA for relapsed and refractory B cell hematological malignancy treatment. Cannabidiol (CBD) is a nonpsychoactive cannabinoid compound that has been utilized as a palliative treatment in cancer patients due to its immunosuppressive properties. Currently, studies on using CBD during immunotherapy have gained increasing attention. However, the possible interaction between CBD and CAR T cell therapy has not been studied. Therefore, in this study, we aimed to examine the direct effects of CBD on CD19-CAR T cell function against hematologic malignancies. Materials and Methods: The cytotoxic effect of CBD was determined by a cell proliferation reagent water-soluble tatrazolium salt (WST-1) assay. CAR T cells were generated by retroviral transduction and treated with CBD at a nontoxic dose. The effect of CBD on immune characteristics, including transgene expression, T cell subset, and memory phenotype, was analyzed by flow cytometry. Proliferation, apoptosis, and cell cycle distribution were analyzed with standard methods. The effect on cytotoxic function was evaluated using degranulation assays, and antitumor activity was evaluated using flow cytometry. Results: The half-maximum inhibitory concentration (IC50) of CBD on NALM6, Raji, and T cells ranged from 16 to 22 μM. The maximum nontoxic dose of CBD that maintained cell viability at ∼100% was 8 μM. For the generation of CD19-CAR T cells, primary T cells were activated and transduced with a retroviral vector encoding CD19-CAR. CBD did not alter the surface expression or immune characteristics, including the T cell subset and memory phenotype, of CD19-CAR T cells. However, CBD suppressed CD19-CAR T cell proliferation by inducing apoptosis, as evidenced by an increase in the proportion of cells in the Sub-G1 phase in cell cycle arrest. However, the antitumor activity and cytokine secretion of CD19-CAR T cells were not altered by exposure to CBD in this study. Conclusions: In this study, a nontoxic dose of CBD affected CD19-CAR T cell proliferation but not its immune characteristics or cytotoxic function.

Deleting the mitochondrial respiration negative regulator MCJ enhances the efficacy of CD8+ T cell adoptive therapies in pre-clinical studies

Mitochondrial respiration is essential for the survival and function of T cells used in adoptive cellular therapies. However, strategies that specifically enhance mitochondrial respiration to promote T cell function remain limited. Here, we investigate methylation-controlled J protein (MCJ), an endogenous negative regulator of mitochondrial complex I expressed in CD8 cells, as a target for improving the efficacy of adoptive T cell therapies. We demonstrate that MCJ inhibits mitochondrial respiration in murine CD8+ CAR-T cells and that deletion of MCJ increases their in vitro and in vivo efficacy against murine B cell leukaemia. Similarly, MCJ deletion in ovalbumin (OVA)-specific CD8+ T cells also increases their efficacy against established OVA-expressing melanoma tumors in vivo. Furthermore, we show for the first time that MCJ is expressed in human CD8 cells and that the level of MCJ expression correlates with the functional activity of CD8+ CAR-T cells. Silencing MCJ expression in human CD8 CAR-T cells increases their mitochondrial metabolism and enhances their anti-tumor activity. Thus, targeting MCJ may represent a potential therapeutic strategy to increase mitochondrial metabolism and improve the efficacy of adoptive T cell therapies.

Efficient combination of radiotherapy and CAR-T - A systematic review

Chimeric antigen receptor T (CAR-T) cell therapy, a groundbreaking immunotherapy. However, it faces formidable challenges in treating solid tumors, grappling with issues like poor trafficking, limited penetration, and insufficient persistence within the tumor microenvironment (TME). CAR-T cells are engineered to express receptors that target specific cancer antigens, enhancing their ability to recognize and eliminate cancer cells. This review paper explores the intricate interplay between CAR-T therapy and radiotherapy (RT), investigating their synergistic potential. Radiotherapy, a standard cancer treatment, involves using high doses of radiation to target and damage cancer cells, disrupting their ability to grow and divide. We highlight that RT modulates the TME, augments antigen presentation, and promotes immune cell infiltration, bolstering CAR-T cell-mediated tumor eradication. Molecular insights shed light on RT-induced alterations in tumor stroma, T cell recruitment promotion, and induction of immunogenic cell death. Noteworthy, strategies, such as combining hypofractionated radiotherapy with myeloid-derived suppressor cell blockade, underscore innovative approaches to enhance CAR-T cell therapy in solid tumors. Bridging indications for RT and CAR-T cells in hematological malignancies are discussed, emphasizing scenarios where RT strategically enhances CAR-T cell efficacy. The paper critically evaluates the RT as a bridge compared to traditional chemotherapy, highlighting timing and dosage considerations crucial for optimizing CAR-T therapy outcomes. In summary, the paper provides valuable insights into the intricate molecular mechanisms activated by RT and innovative strategies to improve CAR-T cell therapy, fostering a deeper understanding of their combined potential in cancer treatment.

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.

Identification of novel targets for immunotherapies in subsets of patients with diffuse large B-cell lymphoma (DLBCL)

Personalized treatment options for subsets of patients with DLBCL are beginning to emerge. Caracciolo et al. explore UMG1, an epitope of CD43 as a potential target for certain patients with DLBCL, and demonstrate promising preclinical activity of an Anti-UMG1-antibody. Commentary on: Caracciolo et al. UMG1/CD3ε-bispecific T-cell engager (BTCE) redirects T-cell cytotoxicity against diffuse large B-cell lymphoma (DLBCL). Br J Haematol 2024;204:555-560.

Tumor microenvironment and CAR-T cell immunotherapy in B-cell lymphoma

Chimeric receptor antigen T cell (CAR-T cell) therapy has demonstrated effectiveness and therapeutic potential in the immunotherapy of hematological malignancies, representing a promising breakthrough in cancer treatment. Despite the efficacy of CAR-T cell therapy in B-cell lymphoma, response variability, resistance, and side effects remain persistent challenges. The tumor microenvironment (TME) plays an intricate role in CAR-T cell therapy of B-cell lymphoma. The TME is a complex and dynamic environment that includes various cell types, cytokines, and extracellular matrix components, all of which can influence CAR-T cell function and behavior. This review discusses the design principles of CAR-T cells, TME in B-cell lymphoma, and the mechanisms by which TME influences CAR-T cell function. We discuss emerging strategies aimed at modulating the TME, targeting immunosuppressive cells, overcoming inhibitory signaling, and improving CAR-T cell infiltration and persistence. Therefore, these processes enhance the efficacy of CAR-T cell therapy and improve patient outcomes in B-cell lymphoma. Further research will be needed to investigate the molecular and cellular events that occur post-infusion, including changes in TME composition, immune cell interactions, cytokine signaling, and potential resistance mechanisms. Understanding these processes will contribute to the development of more effective CAR-T cell therapies and strategies to mitigate treatment-related toxicities.

CAR T cell therapy for patients with solid tumours: key lessons to learn and unlearn

Chimeric antigen receptor (CAR) T cells have been approved for use in patients with B cell malignancies or relapsed and/or refractory multiple myeloma, yet efficacy against most solid tumours remains elusive. The limited imaging and biopsy data from clinical trials in this setting continues to hinder understanding, necessitating a reliance on imperfect preclinical models. In this Perspective, I re-evaluate current data and suggest potential pathways towards greater success, drawing lessons from the few successful trials testing CAR T cells in patients with solid tumours and the clinical experience with tumour-infiltrating lymphocytes. The most promising approaches include the use of pluripotent stem cells, co-targeting multiple mechanisms of immune evasion, employing multiple co-stimulatory domains, and CAR ligand-targeting vaccines. An alternative strategy focused on administering multiple doses of short-lived CAR T cells in an attempt to pre-empt exhaustion and maintain a functional effector pool should also be considered.

Low-Frequency PPM1D Gene Mutations Affect Treatment Response to CD19-Targeted CAR T-Cell Therapy in Large B-Cell Lymphoma

Chimeric antigen receptor T (CAR T)-cell therapy has become a standard treatment option for patients with relapsed or refractory diffuse large B-cell lymphoma (r/r DLBCL). Mutations in the PPM1D gene, a frequent driver alteration in clonal hematopoiesis (CH), lead to a gain of function of PPM1D/Wip1 phosphatase, impairing p53-dependent G1 checkpoint and promoting cell proliferation. The presence of PPM1D mutations has been correlated with reduced response to standard chemotherapy in lymphoma patients. In this study, we analyzed the impact of low-frequency PPM1D mutations on the safety and efficacy of CD19-targeted CAR T-cell therapy in a cohort of 85 r/r DLBCL patients. In this cohort, the prevalence of PPM1D gene mutations was 20% with a mean variant allele frequency (VAF) of 0.052 and a median VAF of 0.036. CAR T-induced cytokine release syndrome (CRS) and immune effector cell-associated neuro-toxicities (ICANS) occurred at similar frequencies in patients with and without PPM1D mutations. Clinical outcomes were globally worse in the PPM1D mutated (PPM1Dmut) vs. PPM1D wild type (PPM1Dwt) subset. While the prevalent treatment outcome within the PPM1Dwt subgroup was complete remission (56%), the majority of patients within the PPM1Dmut subgroup had only partial remission (60%). Median progression-free survival (PFS) was 3 vs. 12 months (p = 0.07) and median overall survival (OS) was 5 vs. 37 months (p = 0.004) for the PPM1Dmut and PPM1Dwt cohort, respectively. Our data suggest that the occurrence of PPM1D mutations in the context of CH may predict worse outcomes after CD19-targeted CAR T-cell therapy in patients with r/r DLBCL.

CAR-T Cell Therapy Shows Similar Efficacy and Toxicity in Patients With DLBCL Regardless of CNS Involvement

Efficacy and toxicity of chimeric antigen receptor T (CAR-T) cell therapy in relapsed/refractory (r/r) diffuse large B-cell lymphoma (DLBCL) with central nervous system (CNS) involvement remain understudied. Here we analyzed the outcomes of CAR-T cell therapy in r/r DLBCL patients with CNS involvement and compared them with patients without CNS disease. Retrospective and monocentric comparative analysis of patient cohort with r/r DLBCL treated with CAR-T cell therapy: 15 patients with CNS versus 65 patients without CNS involvement. Overall response rates (80% versus 80%; P = 1.0), progression-free survival (P = 0.157), and overall survival (P = 0.393) were comparable for both cohorts. The frequency of cytokine release syndrome was comparable in the CNS and non-CNS cohorts; 93% versus 80%; P = 1.0. Numerically, immune effector-cell-associated neurotoxicity syndrome (all grades) was more frequent in patients with CNS manifestation (53% versus 29%; P = 0.063), although no grade 4 events were documented. Our study suggests that CAR-T cell therapy is effective and feasible in patients with r/r DLBCL and CNS manifestation.

CD19 CAR-T cell therapy for relapsed or refractory diffuse large B cell lymphoma: Why does it fail?

Chimeric antigen receptor T (CAR-T) cell therapy is an effective treatment for relapsed or refractory diffuse large B cell lymphoma (DLBCL) with 3 CD19 targeting products now FDA-approved for this indication. However, up to 60% of patients ultimately progress or relapse following CAR-T cell therapy. Mechanisms of resistance to CAR-T cell therapy in patients with DLBCL are likely multifactorial and have yet to be fully elucidated. Determining patient, tumor and therapy-related factors that may predict an individual's response to CAR-T cell therapy requires ongoing analysis of data from clinical trials and real-world experience in this population. In this review we will discuss the factors identified to-date that may contribute to failure of CAR-T cell therapy in achieving durable remissions in patients with DLBCL.

INSPIRED Symposium Part 2: Prevention and Management of Relapse Following Chimeric Antigen Receptor T Cell Therapy for B Cell Acute Lymphoblastic Leukemia

Although CD19-directed chimeric antigen receptor (CAR) T cell therapy (CAR-T) for relapsed/refractory B cell acute lymphoblastic leukemia (B-ALL) has been transformative in inducing and sustaining remission, relapse rates remain unacceptably high, with approximately 50% of children and young adults experiencing relapse within the first year postinfusion. Emerging strategies to extend the durability of remission involve the use of prognostic biomarkers to identify those at high risk of relapse or incorporate strategies aimed to enhancing functional CAR T cell persistence. Nonetheless, with antigen loss/down-regulation or evolution to lineage switch as major mechanisms of relapse, optimizing single antigen targeting alone is insufficient. Here, with a focus on relapse prevention strategies, including postinfusion surveillance and treatment approaches being explored to optimize post-CAR-T management (eg, combinatorial antigen targeting strategies, preemptive hematopoietic cell transplantation), we review the current state of the art in the prevention and management of post CAR-T relapse. We highlight the advancements in the field and identify gaps in the literature to guide future research in optimizing the prevention and management of post-CAR-T relapse in children and young adults with B-ALL.

Strategies for enhancing CAR T cell expansion and persistence in HIV infection

Chimeric Antigen Receptor (CAR) T cell therapies are tremendously successful in hematological malignancies and show great promise as treatment and curative strategy for HIV. A major determinant for effective CAR T cell therapy is the persistence of CAR T cells. Particularly, antigen density and target cell abundance are crucial for the engagement, engraftment, and persistence of CAR T cells. The success of HIV-specific CAR T cells is challenged by limited antigen due to low cell surface expression of viral proteins and the scarcity of chronically infected cells during antiretroviral therapy. Several strategies have been explored to increase the efficacy of CAR T cells by enhancing expansion and persistence of the engineered cells. This review highlights the challenges of designing CAR T cells against HIV and other chronic viral infections. We also discuss potential strategies to enhance CAR T cell expansion and persistence in the setting of low antigen exposure.

Clinical Impact of Single Nucleotide Polymorphism in CD-19 on Treatment Outcome in FMC63-CAR-T Cell Therapy

Chimeric antigen receptor (CAR)-T cell therapy is effective in patients with relapsed or refractory diffuse large B-cell lymphoma (r/r DLBCL) with response rates of 63-84% and complete response observed in 43-54%. Common germline variants of the target antigen CD19 may elicit different responses to CAR-T cell therapy. The CD19 gene single nucleotide polymorphism rs2904880 encoding leucine or valine at amino acid position 174 of the CD19 antigen was prevalent in 51% of the studied DLBCL patients. In a retrospective comparative analysis of clinical outcome, there were significant differences in CD19 L174 versus V174 carriers: the median time of progression-free survival was 22 vs. 6 months (p = 0.06), overall survival was 37 vs. 8 months (p = 0.11), complete response rates were 51% vs. 30% (p = 0.05), and refractory disease rates were 14% vs. 32% (p = 0.04). The single nucleotide polymorphism in CD19 was shown to influence the treatment outcome in FMC63-anti-CD19-CAR-T cell therapy, and the CD19 minor allele L174 predicted a favorable treatment outcome.