The Fate(s) of CAR T-Cell Therapy: Navigating the Risks of CAR+ T-Cell Malignancy.

The introduction of chimeric antigen receptor (CAR) T-cell therapy represents a landmark advancement in treating resistant forms of cancer such as leukemia, lymphoma, and myeloma. However, concerns about long-term safety have emerged following an FDA investigation into reports of second primary malignancies (SPM) after CAR-T cell treatment. This review offers a thorough examination of how genetically modified T cells might transform into CAR+ SPM. It explores genetic and molecular pathways leading to T-cell lymphomagenesis, the balance between CAR T-cell persistence, stemness, and oncogenic risk, and the trade-off of T-cell exhaustion, which may limit therapy efficacy but potentially reduce lymphomagenesis risk. Significance: An FDA probe into 22 cases of second primary T-cell malignancies following CAR T-cell therapy stresses the need to investigate their origins. Few may arise from preexisting genetic and epigenetic alterations and those introduced during therapeutic engineering. Technological advances, regulatory oversight, and patient monitoring are essential to mitigate potential risks.

Integration of ζ-deficient CARs into the CD3ζ gene conveys potent cytotoxicity in T and NK cells.

ABSTRACT: Chimeric antigen receptor (CAR)-redirected immune cells hold significant therapeutic potential for oncology, autoimmune diseases, transplant medicine, and infections. All approved CAR-T therapies rely on personalized manufacturing using undirected viral gene transfer, which results in nonphysiological regulation of CAR-signaling and limits their accessibility due to logistical challenges, high costs and biosafety requirements. Random gene transfer modalities pose a risk of malignant transformation by insertional mutagenesis. Here, we propose a novel approach utilizing CRISPR-Cas gene editing to redirect T cells and natural killer (NK) cells with CARs. By transferring shorter, truncated CAR-transgenes lacking a main activation domain into the human CD3ζ (CD247) gene, functional CAR fusion-genes are generated that exploit the endogenous CD3ζ gene as the CAR's activation domain. Repurposing this T/NK-cell lineage gene facilitated physiological regulation of CAR expression and redirection of various immune cell types, including conventional T cells, TCRγ/δ T cells, regulatory T cells, and NK cells. In T cells, CD3ζ in-frame fusion eliminated TCR surface expression, reducing the risk of graft-versus-host disease in allogeneic off-the-shelf settings. CD3ζ-CD19-CAR-T cells exhibited comparable leukemia control to TCRα chain constant (TRAC)-replaced and lentivirus-transduced CAR-T cells in vivo. Tuning of CD3ζ-CAR-expression levels significantly improved the in vivo efficacy. Notably, CD3ζ gene editing enabled redirection of NK cells without impairing their canonical functions. Thus, CD3ζ gene editing is a promising platform for the development of allogeneic off-the-shelf cell therapies using redirected killer lymphocytes.

Cost-effectiveness of second-line lisocabtagene maraleucel in relapsed or refractory diffuse large B-cell lymphoma.

ABSTRACT: Lisocabtagene maraleucel (liso-cel), a chimeric antigen receptor (CAR) T-cell therapy, received the US Food and Drug Administration approval in 2022 for second-line treatment of diffuse large B-cell lymphoma (DLBCL) for patients with refractory disease or early relapse after first-line chemoimmunotherapy. This decision was based on the TRANSFORM study demonstrating improvements in event-free survival with liso-cel compared with standard care. Given the high costs of CAR T-cell therapies, particularly as they transition to second-line treatment, a cost-effectiveness analysis is essential to determine their economic viability. The study used a partitioned survival model with standard parametric functions to evaluate the cost-effectiveness of liso-cel aganist platinum-based chemotherapy followed by high-dose chemotherapy and autologous hematopoietic stem cell transplantation over a lifetime horizon The analysis relied on data from the TRANSFORM and TRANSCEND trials, established literature, and public data sets to calculate the incremental cost-effectiveness ratio (ICER). For a representative cohort of US adults aged 60 years, ICER of liso-cel was $99 669 per quality-adjusted life-year (QALY) from a health care sector perspective and $68 212 per QALY from a societal perspective, confirming its cost-effectiveness at the $100 000 per QALY threshold. Nonetheless, under certain scenarios, liso-cel surpasses this benchmark but remains within the US acceptable range of $150 000 per QALY. A key finding underlines the importance of incorporating productivity losses into such analyses to capture the broader societal values of novel therapies. Although these therapies offer substantial clinical benefits, their high acquisition costs and limited long-term data critically challenge their economic sustainability.

Integration of ζ-deficient CARs into the CD3-zeta gene conveys potent cytotoxicity in T and NK cells.

Chimeric antigen receptor (CAR)-reprogrammed immune cells hold significant therapeutic potential for oncology, autoimmune diseases, transplant medicine, and infections. All approved CAR-T therapies rely on personalized manufacturing using undirected viral gene transfer, which results in non-physiological regulation of CAR-signaling and limits their accessibility due to logistical challenges, high costs and biosafety requirements. Here, we propose a novel approach utilizing CRISPR-Cas gene editing to redirect T cells and natural killer (NK) cells with CARs. By transferring shorter, truncated CAR-transgenes lacking a main activation domain into the human CD3 ζ (CD247) gene, functional CAR fusion-genes are generated that exploit the endogenous CD3 ζ gene as the CAR's activation domain. Repurposing this T/NK-cell lineage gene facilitated physiological regulation of CAR-expression and reprogramming of various immune cell types, including conventional T cells, TCRγ/δ T cells, regulatory T cells, and NK cells. In T cells, CD3 ζ in-frame fusion eliminated TCR surface expression, reducing the risk of graft-versus-host disease in allogeneic off-the-shelf settings. CD3 ζ-CD19-CAR-T cells exhibited comparable leukemia control to T cell receptor alpha constant ( TRAC )-replaced and lentivirus-transduced CAR-T cells in vivo . Tuning of CD3 ζ-CAR-expression levels significantly improved the in vivo efficacy. Compared to TRAC -edited CAR-T cells, integration of a Her2-CAR into CD3 ζ conveyed similar in vitro tumor lysis but reduced susceptibility to activation-induced cell death and differentiation, presumably due to lower CAR-expression levels. Notably, CD3 ζ gene editing enabled reprogramming of NK cells without impairing their canonical functions. Thus, CD3 ζ gene editing is a promising platform for the development of allogeneic off-the-shelf cell therapies using redirected killer lymphocytes. Key points: Integration of ζ-deficient CARs into CD3 ζ gene allows generation of functional TCR-ablated CAR-T cells for allogeneic off-the-shelf use CD3 ζ-editing platform allows CAR reprogramming of NK cells without affecting their canonical functions.

CAR NK-92 cell-mediated depletion of residual TCR+ cells for ultrapure allogeneic TCR-deleted CAR T-cell products.

Graft-versus-host disease (GVHD) is a major risk of the administration of allogeneic chimeric antigen receptor (CAR)-redirected T cells to patients who are HLA unmatched. Gene editing can be used to disrupt potentially alloreactive T-cell receptors (TCRs) in CAR T cells and reduce the risk of GVHD. Despite the high knockout rates achieved with the optimized methods, a subsequent purification step is necessary to obtain a safe allogeneic product. To date, magnetic cell separation (MACS) has been the gold standard for purifying TCRα/ß- CAR T cells, but product purity can still be insufficient to prevent GVHD. We developed a novel and highly efficient approach to eliminate residual TCR/CD3+ T cells after TCRα constant (TRAC) gene editing by adding a genetically modified CD3-specific CAR NK-92 cell line during ex vivo expansion. Two consecutive cocultures with irradiated, short-lived, CAR NK-92 cells allowed for the production of TCR- CAR T cells with <0.01% TCR+ T cells, marking a 45-fold reduction of TCR+ cells compared with MACS purification. Through an NK-92 cell-mediated feeder effect and circumventing MACS-associated cell loss, our approach increased the total TCR- CAR T-cell yield approximately threefold while retaining cytotoxic activity and a favorable T-cell phenotype. Scaling in a semiclosed G-Rex bioreactor device provides a proof-of-principle for large-batch manufacturing, allowing for an improved cost-per-dose ratio. Overall, this cell-mediated purification method has the potential to advance the production process of safe off-the-shelf CAR T cells for clinical applications.

Long-term response to autologous anti-CD19 chimeric antigen receptor T cells in relapsed or refractory B cell acute lymphoblastic leukemia: a systematic review and meta-analysis.

Chimeric Antigen Receptor (CAR) T cell therapy is an effective treatment approach for patients with relapsed or refractory acute lymphoblastic leukemia (R/R B-ALL). However, identifying the factors that influence long-term response to this therapy is necessary to optimize patient selection and treatment allocation. We conducted a literature review and meta-analysis to investigate the use of autologous anti-CD19 CAR T cell therapy in both pediatric and adult patients with R/R B-ALL, using several databases including MEDLINE, Cochrane Central, ScienceDirect, Web of Science, Journals@Ovid, Embase, and clinicaltrial.gov. A total of 38 reports were analyzed, which enrolled 2134 patients. Time-to-event endpoints were estimated using reconstructed patient survival data. The study explored key modulators of response, including costimulatory domains, disease status, age, and lymphodepletion. The median overall survival and event-free survival were 36.2 months [95% CI 28.9, NR] and 13.3 months [95% CI 12.2, 17], respectively. The overall response rate was 76% [95% CI 71, 81]. The use of 4-1BB costimulatory domain in the CAR construct, administration of low-dose cyclophosphamide lymphodepletion, and pretreatment morphologic remission were associated with better overall survival, with hazard ratios of 0.72, 0.56, and 0.66, respectively. Morphologic remission and 4-1BB domain were associated with better event-free survival, with hazard ratios of 0.66 and 0.72, respectively. These findings suggest that CAR T cell therapy may offer long-term benefits to patients with R/R B-ALL. However, further research is needed to optimize patient selection and better understand the impact of various factors on the outcome of CAR T cell therapy.

Overcoming on-target, off-tumour toxicity of CAR T cell therapy for solid tumours.

Therapies with genetically modified T cells that express chimeric antigen receptors (CARs) specific for CD19 or B cell maturation antigen (BCMA) are approved to treat certain B cell malignancies. However, translating these successes into treatments for patients with solid tumours presents various challenges, including the risk of clinically serious on-target, off-tumour toxicity (OTOT) owing to CAR T cell-mediated cytotoxicity against non-malignant tissues expressing the target antigen. Indeed, severe OTOT has been observed in various CAR T cell clinical trials involving patients with solid tumours, highlighting the importance of establishing strategies to predict, mitigate and control the onset of this effect. In this Review, we summarize current clinical evidence of OTOT with CAR T cells in the treatment of solid tumours and discuss the utility of preclinical mouse models in predicting clinical OTOT. We then describe novel strategies being developed to improve the specificity of CAR T cells in solid tumours, particularly the role of affinity tuning of target binders, logic circuits and synthetic biology. Furthermore, we highlight control strategies that can be used to mitigate clinical OTOT following cell infusion such as regulating or eliminating CAR T cell activity, exogenous control of CAR expression, and local administration of CAR T cells.

Cost-effectiveness of Axicabtagene Ciloleucel and Tisagenlecleucel as Second-line or Later Therapy in Relapsed or Refractory Diffuse Large B-Cell Lymphoma.

Importance: Chimeric antigen receptor (CAR) T cell therapies are approved as a third-line or later therapy for several hematological malignant neoplasms. Recently, randomized clinical trials have investigated their efficacy as a second-line treatment in high-risk relapsed or refractory diffuse large B-cell lymphoma (DLBCL) compared with salvage chemotherapy followed by hematopoietic stem cell transplantation (HSCT). Objective: To evaluate the cost-effectiveness of axicabtagene ciloleucel and tisagenlecleucel vs standard care (SC) as second-line or later therapy for relapsed or refractory DLBCL, from both US health care sector and societal perspectives at a cost-effectiveness threshold of $150 000 per quality-adjusted life-year (QALY). Design, Setting, and Participants: This economic evaluation assessed cost-effectiveness using a partitioned survival model with 2021 US dollars and QALYs over a lifetime horizon. Model inputs were derived from 2 randomized clinical trials (ZUMA-7 and BELINDA) and published literature. In the trials, patients who did not respond to SC received CAR T cells (treatment switching or crossover), either outside the protocol (ZUMA-7) or as part of the protocol (BELINDA). A separate scenario analysis compared second-line axicabtagene ciloleucel with SC alone without treatment crossover to CAR T cell therapy. Data analysis was performed from December 18, 2021, to September 13, 2022. Exposures: CAR T cell therapy (axicabtagene ciloleucel and tisagenlecleucel) compared with salvage chemotherapy followed by HSCT. Main Outcomes and Measures: Costs and QALYs were used to derive incremental cost-effectiveness ratios (ICERs) for the health care sector and societal perspectives. Cost and QALYs were discounted at 3.0% annually. Univariate and multivariate probabilistic sensitivity analysis using 10 000 Monte Carlo simulations were applied to test model uncertainty on the ICER. Results: Second-line axicabtagene ciloleucel was associated with an ICER of $99 101 per QALY from the health care sector perspective and an ICER of $97 977 per QALY from the societal perspective, while second-line tisagenlecleucel was dominated by SC (incremental costs of $37 803 from the health care sector and $39 480 from the societal perspective with decremental QALY of -0.02). Third-line or later tisagenlecleucel was associated with an ICER of $126 593 per QALY from the health care sector perspective and an ICER of $128 012 per QALY from the societal perspective. Based on the scenario analysis of no treatment switching, second-line axicabtagene ciloleucel yielded an ICER of $216 790 per QALY from the health care sector perspective and an ICER of $218 907 per QALY from the societal perspective, compared with SC. When accounting for patients achieving prolonged progression-free survival who would not incur progression-related costs, in this scenario ICER changed to $125 962 per QALY from the health care sector perspective and $122 931 per QALY from the societal perspective. These results were most sensitive to increased list prices of CAR T cell therapy and QALY losses associated with axicabtagene ciloleucel and tisagenlecleucel. Conclusions and Relevance: These findings suggest that second-line axicabtagene ciloleucel and third-line or later tisagenlecleucel were cost-effective in treating patients with relapsed or refractory DLBCL at the cost-effectiveness threshold of $150 000 per QALY. However, uncertainty remains regarding the best candidates who would experience value gains from receiving CAR T cell therapy.

Adoptive transfer of ex vivo expanded regulatory T cells improves immune cell engraftment and therapy-refractory chronic GvHD.

Graft-versus-host disease (GvHD) is still the major non-relapse, life-limiting complication after hematopoietic stem cell transplantation. Modern pharmacologic immunosuppression is often insufficient and associated with significant side effects. Novel treatment strategies now include adoptive transfer of ex vivo expanded regulatory T cells (Tregs), but their efficacy in chronic GvHD is unknown. We treated three children suffering from severe, therapy-refractory GvHD with polyclonally expanded Tregs generated from the original stem cell donor. Third-line maintenance immunosuppression was tapered to cyclosporin A and low-dose steroids shortly before cell transfer. Regular follow-up included an assessment of the subjective and objective clinical development, safety parameters, and in-depth immune monitoring. All patients showed marked clinical improvement with substantially decreased GvHD activity. Laboratory follow-up showed a significant enhancement of the immunologic engraftment, including lymphocytes and dendritic cells. Monitoring the fate of Tregs by next-generation sequencing demonstrated clonal expansion. In summary, adoptive transfer of Tregs was well tolerated and able to modulate an established undesired T cell mediated allo-response. Although no signs of overimmunosuppression were detectable, the treatment of patients with invasive opportunistic infections should be undertaken with caution. Further controlled studies are necessary to confirm these encouraging effects and eventually pave the way for adoptive Treg therapy in chronic GvHD.

Preparing for CAR T cell therapy: patient selection, bridging therapies and lymphodepletion.

Chimeric antigen receptor (CAR) T cells have emerged as a potent therapeutic approach for patients with certain haematological cancers, with multiple CAR T cell products currently approved by the FDA for those with relapsed and/or refractory B cell malignancies. However, in order to derive the desired level of effectiveness, patients need to successfully receive the CAR T cell infusion in a timely fashion. This process entails apheresis of the patient's T cells, followed by CAR T cell manufacture. While awaiting infusion at an authorized treatment centre, patients may receive interim disease-directed therapy. Most patients will also receive a course of pre-CAR T cell lymphodepletion, which has emerged as an important factor in enabling durable responses. The time between apheresis and CAR T cell infusion is often not a simple journey, with each milestone being a critical step that can have important downstream consequences for the ability to receive the infusion and the strength of clinical responses. In this Review, we provide a summary of the many considerations for preparing patients with B cell non-Hodgkin lymphoma or acute lymphoblastic leukaemia for CAR T cell therapy, and outline current limitations and areas for future research.

Scalable Manufacturing of CAR T cells for Cancer Immunotherapy.

As of April 2021, there are five commercially available chimeric antigen receptor (CAR) T cell therapies for hematological malignancies. With the current transition of CAR T cell manufacturing from academia to industry, there is a shift toward Good Manufacturing Practice (GMP)-compliant closed and automated systems to ensure reproducibility and to meet the increased demand for cancer patients. In this review we describe current CAR T cells clinical manufacturing models and discuss emerging technological advances that embrace scaling and production optimization. We summarize measures being used to shorten CAR T-cell manufacturing times and highlight regulatory challenges to scaling production for clinical use. STATEMENT OF SIGNIFICANCE ∣: As the demand for CAR T cell cancer therapy increases, several closed and automated production platforms are being deployed, and others are in development.This review provides a critical appraisal of these technologies that can be leveraged to scale and optimize the production of next generation CAR T cells.

Unproven stem cell interventions: A global public health problem requiring global deliberation.

The unproven stem cell intervention (SCI) industry is a global health problem. Despite efforts of some nations, the industry continues to flourish. In this paper, we call for a global approach and the establishment of a World Health Organization (WHO) Expert Advisory Committee on Regenerative Medicine to tackle this issue and provide guidance. The WHO committee can harmonize national regulations; promote regulatory approaches responsive to unmet patient needs; and formulate an education campaign against misinformation. Fostering an international dialog and developing recommendations that can be adopted by member states would effectively address the global market of unproven SCIs.

Immunogenicity of CAR T cells in cancer therapy.

Patient-derived T cells genetically reprogrammed to express CD19-specific chimeric antigen receptors (CARs) have shown remarkable clinical responses and are commercially available for the treatment of patients with certain advanced-stage B cell malignancies. Nonetheless, several trials have revealed pre-existing and/or treatment-induced immune responses to the mouse-derived single-chain variable fragments included in these constructs. These responses might have contributed to both treatment failure and the limited success of redosing strategies observed in some patients. Data from early phase clinical trials suggest that CAR T cells are also associated with immunogenicity-related events in patients with solid tumours. Generally, the clinical implications of anti-CAR immune responses are poorly understood and highly variable between different CAR constructs and malignancies. These observations highlight an urgent need to uncover the mechanisms of immunogenicity in patients receiving CAR T cells and develop validated assays to enable clinical detection. In this Review, we describe the current clinical evidence of anti-CAR immune responses and discuss how new CAR T cell technologies might impact the risk of immunogenicity. We then suggest ways to reduce the risks of anti-CAR immune responses to CAR T cell products that are advancing towards the clinic. Finally, we summarize measures that investigators could consider in order to systematically monitor and better comprehend the possible effects of immunogenicity during trials involving CAR T cells as well as in routine clinical practice.

COVID-19-Induced ARDS Is Associated with Decreased Frequency of Activated Memory/Effector T Cells Expressing CD11a+.

Preventing the progression to acute respiratory distress syndrome (ARDS) in COVID-19 is an unsolved challenge. The involvement of T cell immunity in this exacerbation remains unclear. To identify predictive markers of COVID-19 progress and outcome, we analyzed peripheral blood of 10 COVID-19-associated ARDS patients and 35 mild/moderate COVID-19 patients, not requiring intensive care. Using multi-parametric flow cytometry, we compared quantitative, phenotypic, and functional characteristics of circulating bulk immune cells, as well as SARS-CoV-2 S-protein-reactive T cells between the two groups. ARDS patients demonstrated significantly higher S-protein-reactive CD4+ and CD8+ T cells compared to non-ARDS patients. Of interest, comparison of circulating bulk T cells in ARDS patients to non-ARDS patients demonstrated decreased frequencies of CD4+ and CD8+ T cell subsets, with activated memory/effector T cells expressing tissue migration molecule CD11a++. Importantly, survival from ARDS (4/10) was accompanied by a recovery of the CD11a++ T cell subsets in peripheral blood. Conclusively, data on S-protein-reactive polyfunctional T cells indicate the ability of ARDS patients to generate antiviral protection. Furthermore, decreased frequencies of activated memory/effector T cells expressing tissue migratory molecule CD11a++ observed in circulation of ARDS patients might suggest their involvement in ARDS development and propose the CD11a-based immune signature as a possible prognostic marker.