Tethered IL-15 augments antitumor activity and promotes a stem-cell memory subset in tumor-specific T cells

Mitochondria Dictate Function and Fate of HSCs and T Cells

Hematopoietic stem cells (HSC) and T cells are intimately related, lineage-dependent cell populations that are extensively used as therapeutic products for the treatment of hematologic malignancies and certain types of solid tumors. These cellular therapies can be life-saving treatments; however, their efficacies are often limited by factors influencing their activity and cellular properties. Among these factors is mitochondrial metabolism, which influences the function and fate commitment of both HSCs and T cells. Mitochondria, besides being the "cellular powerhouse," provide metabolic intermediates that are used as substrates for epigenetic modifications and chromatin remodeling, thus, driving cell fate decisions during differentiation. Moreover, mitochondrial fitness and mitochondrial quality control mechanisms are closely related to cellular function, and impairment of these mitochondrial properties associates with cellular dysfunction due to factors such as T-cell exhaustion and aging. Here, we give an overview of the role of mitochondria in shaping the behavior of these lineage-related cell populations. Moreover, we discuss the potential of novel mitochondria-targeting strategies for enhancing HSC- and T cell-based cancer immunotherapies and highlight how design and application of such approaches requires consideration of the metabolic similarities and differences between HSCs and T cells. See related article on p. 1302.

Sleeping Beauty kit sets provide rapid and accessible generation of artificial antigen-presenting cells for natural killer cell expansion

Artificial antigen-presenting cells (aAPCs) offer a cost effective and convenient tool for the expansion of chimeric antigen receptor (CAR)-bearing T cells and NK cells. aAPCs are particularly useful because of their ability to efficiently expand low-frequency antigen-reactive lymphocytes in bulk cultures. Commonly derived from the leukemic cell line K562, these aAPCs lack most major histocompatibility complex expression and are therefore useful for NK cell expansion without triggering allogeneic T-cell proliferation. To combat difficulties in accessing existing aAPC lines, while circumventing the iterative lentiviral gene transfers with antibody-mediated sorting required for the isolation of stable aAPC clones, we developed a single-step technique using Sleeping Beauty (SB)-based vectors with antibiotic selection options. Our SB vectors contain options of two to three genes encoding costimulatory molecules, membrane-bound cytokines as well as the presence of antibiotic-resistance genes that allow for stable transposition-based transfection of feeder cells. Transfection of K562 with SB vectors described in this study allows for the surface expression of CD86, 4-1BBL, membrane-bound (mb) interleukin (IL)-15 and mbIL-21 after simultaneous transposition and antibiotic selection using only two antibiotics. aAPCs successfully expanded NK cells to high purity (80-95%). Expanded NK cells could be further engineered by lentiviral CAR transduction. The multivector kit set is publicly available and will allow convenient and reproducible in-house production of effective aAPCs for the in vitro expansion of primary cells.

Severe hematotoxicity after CD19 CAR-T therapy is associated with suppressive immune dysregulation and limited CAR-T expansion

Prolonged cytopenias after chimeric antigen receptor (CAR) T cell therapy are a significant clinical problem and the underlying pathophysiology remains poorly understood. Here, we investigated how (CAR) T cell expansion dynamics and serum proteomics affect neutrophil recovery phenotypes after CD19-directed CAR T cell therapy. Survival favored patients with "intermittent" neutrophil recovery (e.g., recurrent neutrophil dips) compared to either "quick" or "aplastic" recovery. While intermittent patients displayed increased CAR T cell expansion, aplastic patients exhibited an unfavorable relationship between expansion and tumor burden. Proteomics of patient serum collected at baseline and in the first month after CAR-T therapy revealed higher markers of endothelial dysfunction, inflammatory cytokines, macrophage activation, and T cell suppression in the aplastic phenotype group. Prolonged neutrophil aplasia thus occurs in patients with systemic immune dysregulation at baseline with subsequently impaired CAR-T expansion and myeloid-related inflammatory changes. The association between neutrophil recovery and survival outcomes highlights critical interactions between host hematopoiesis and the immune state stimulated by CAR-T infusion.

Pre-clinical validation of a pan-cancer CAR-T cell immunotherapy targeting nfP2X7

Chimeric antigen receptor (CAR)-T cell immunotherapy is a novel treatment that genetically modifies the patients' own T cells to target and kill malignant cells. However, identification of tumour-specific antigens expressed on multiple solid cancer types, remains a major challenge. P2X purinoceptor 7 (P2X7) is a cell surface expressed ATP gated cation channel, and a dysfunctional version of P2X7, named nfP2X7, has been identified on cancer cells from multiple tissues, while being undetectable on healthy cells. We present a prototype -human CAR-T construct targeting nfP2X7 showing potential antigen-specific cytotoxicity against twelve solid cancer types (breast, prostate, lung, colorectal, brain and skin). In xenograft mouse models of breast and prostate cancer, CAR-T cells targeting nfP2X7 exhibit robust anti-tumour efficacy. These data indicate that nfP2X7 is a suitable immunotherapy target because of its broad expression on human tumours. CAR-T cells targeting nfP2X7 have potential as a wide-spectrum cancer immunotherapy for solid tumours in humans.

Cellular and molecular waypoints along the path of T cell exhaustion

Thirty years of foundational research investigating molecular and cellular mechanisms promoting T cell exhaustion are now enabling rational design of T cell-based therapies for the treatment of chronic infections and cancer. Once described as a static cell fate, it is now well appreciated that the developmental path toward exhaustion is composed of a heterogeneous pool of cells with varying degrees of effector potential that ultimately converge on a terminally differentiated state. Recent description of the developmental stages along the differentiation trajectory of T cell exhaustion has provided insight into past immunotherapeutic success and future opportunities. Here, we discuss the hallmarks of distinct developmental stages occurring along the path to T cell dysfunction and the impact of these discrete CD8+ T cell fates on cancer immunotherapy.

Enhancing CAR T-cell Therapy Using Fab-Based Constitutively Heterodimeric Cytokine Receptors

Adoptive T-cell therapy aims to achieve lasting tumor clearance, requiring enhanced engraftment and survival of the immune cells. Cytokines are paramount modulators of T-cell survival and proliferation. Cytokine receptors signal via ligand-induced dimerization, and this principle has been hijacked utilizing nonnative dimerization domains. A major limitation of current technologies resides in the absence of a module that recapitulates the natural cytokine receptor heterodimeric pairing. To circumvent this, we created a new engineered cytokine receptor able to constitutively recreate receptor-heterodimer utilizing the heterodimerization domain derived from the IgG1 antibody (dFab_CCR). We found that the signal delivered by the dFab_CCR-IL2 proficiently mimicked the cytokine receptor heterodimerization, with transcriptomic signatures like those obtained by activation of the native IL2 receptor. Moreover, we found that this dimerization structure was agnostic, efficiently activating signaling through four cytokine receptor families. Using a combination of in vivo and in vitro screening approaches, we characterized a library of 18 dFab_CCRs coexpressed with a clinically relevant solid tumor-specific GD2-specific chimeric antigen receptor (CAR). Based on this characterization, we suggest that the coexpression of either the common β-chain GMCSF or the IL18 dFab_CCRs is optimal to improve CAR T-cell expansion, engraftment, and efficacy. Our results demonstrate how Fab dimerization is efficient and versatile in recapitulating a cytokine receptor heterodimerization signal. This module could be applied for the enhancement of adoptive T-cell therapies, as well as therapies based on other immune cell types. Furthermore, these results provide a choice of cytokine signal to incorporate with adoptive T-cell therapies.

Metabolic glycan labeling immobilizes dendritic cell membrane and enhances antitumor efficacy of dendritic cell vaccine

Dendritic cell (DC) vaccine was among the first FDA-approved cancer immunotherapies, but has been limited by the modest cytotoxic T lymphocyte (CTL) response and therapeutic efficacy. Here we report a facile metabolic labeling approach that enables targeted modulation of adoptively transferred DCs for developing enhanced DC vaccines. We show that metabolic glycan labeling can reduce the membrane mobility of DCs, which activates DCs and improves the antigen presentation and subsequent T cell priming property of DCs. Metabolic glycan labeling itself can enhance the antitumor efficacy of DC vaccines. In addition, the cell-surface chemical tags (e.g., azido groups) introduced via metabolic glycan labeling also enable in vivo conjugation of cytokines onto adoptively transferred DCs, which further enhances CTL response and antitumor efficacy. Our DC labeling and targeting technology provides a strategy to improve the therapeutic efficacy of DC vaccines, with minimal interference upon the clinical manufacturing process.

Challenges and new technologies in adoptive cell therapy

Adoptive cell therapies (ACTs) have existed for decades. From the initial infusion of tumor-infiltrating lymphocytes to the subsequent specific enhanced T cell receptor (TCR)-T and chimeric antigen receptor (CAR)-T cell therapies, many novel strategies for cancer treatment have been developed. Owing to its promising outcomes, CAR-T cell therapy has revolutionized the field of ACTs, particularly for hematologic malignancies. Despite these advances, CAR-T cell therapy still has limitations in both autologous and allogeneic settings, including practicality and toxicity issues. To overcome these challenges, researchers have focused on the application of CAR engineering technology to other types of immune cell engineering. Consequently, several new cell therapies based on CAR technology have been developed, including CAR-NK, CAR-macrophage, CAR-γδT, and CAR-NKT. In this review, we describe the development, advantages, and possible challenges of the aforementioned ACTs and discuss current strategies aimed at maximizing the therapeutic potential of ACTs. We also provide an overview of the various gene transduction strategies employed in immunotherapy given their importance in immune cell engineering. Furthermore, we discuss the possibility that strategies capable of creating a positive feedback immune circuit, as healthy immune systems do, could address the flaw of a single type of ACT, and thus serve as key players in future cancer immunotherapy.

Antigen-dependent IL-12 signaling in CAR T cells promotes regional to systemic disease targeting

Chimeric antigen receptor (CAR) T cell therapeutic responses are hampered by limited T cell trafficking, persistence, and durable anti-tumor activity in solid tumors. However, these challenges can be largely overcome by relatively unconstrained synthetic engineering strategies. Here, we describe CAR T cells targeting tumor-associated glycoprotein-72 (TAG72), utilizing the CD28 transmembrane domain upstream of the 4-1BB co-stimulatory domain as a driver of potent anti-tumor activity and IFNγ secretion. CAR T cell-mediated IFNγ production facilitated by IL-12 signaling is required for tumor cell killing, which is recapitulated by engineering an optimized membrane-bound IL-12 (mbIL12) molecule in CAR T cells. These T cells show improved antigen-dependent T cell proliferation and recursive tumor cell killing in vitro, with robust in vivo efficacy in human ovarian cancer xenograft models. Locoregional administration of mbIL12-engineered CAR T cells promotes durable anti-tumor responses against both regional and systemic disease in mice. Safety and efficacy of mbIL12-engineered CAR T cells is demonstrated using an immunocompetent mouse model, with beneficial effects on the immunosuppressive tumor microenvironment. Collectively, our study features a clinically-applicable strategy to improve the efficacy of locoregionally-delivered CAR T cells engineered with antigen-dependent immune-modulating cytokines in targeting regional and systemic disease.

Constitutive Turbodomains enhance expansion and antitumor activity of allogeneic BCMA CAR T cells in preclinical models

The magnitude of CAR T cell expansion has been associated with clinical efficacy. Although cytokines can augment CAR T cell proliferation, systemically administered cytokines can result in toxicities. To gain the benefits of cytokine signaling while mitigating toxicities, we designed constitutively active synthetic cytokine receptor chimeras (constitutive Turbodomains) that signal in a CAR T cell-specific manner. The modular design of Turbodomains enables diverse cytokine signaling outputs from a single homodimeric receptor chimera and allows multiplexing of different cytokine signals. Turbodomains containing an IL-2/15Rβ-derived signaling domain closely mimicked IL-15 signaling and enhanced CAR T cell potency. Allogeneic TurboCAR T cells targeting BCMA showed no evidence of aberrant proliferation yet displayed enhanced expansion and antitumor activity, prolonging survival and preventing extramedullary relapses in mouse models. These results illustrate the potential of constitutive Turbodomains to achieve selective potentiation of CAR T cells and demonstrate the safety and efficacy of allogeneic BCMA TurboCAR T cells, supporting clinical evaluation in multiple myeloma.

The role of bone marrow microenvironment on CAR-T efficacy in haematologic malignancies

In recent years, chimeric antigen receptor-T (CAR-T) cell therapy has emerged as a novel immunotherapy method. It has shown significant therapeutic efficacy in the treatment of haematological B cell malignancies. In particular, the CAR-T therapy targeting CD19 has yielded unprecedented efficacy for acute B-lymphocytic leukaemia (B-ALL) and non-Hodgkin's lymphoma (NHL). In haematologic malignancies, tumour stem cells are more prone to stay in the regulatory bone marrow (BM) microenvironment (called niches), which provides a protective environment against immune attack. However, how the BM microenvironment affects the anti-tumour efficacy of CAR-T cells and its underlying mechanism is worthy of attention. In this review, we discuss the role of the BM microenvironment on the efficacy of CAR-T in haematological malignancies and propose corresponding strategies to enhance the anti-tumour activity of CAR-T therapy.

Role of stem cell-like memory T cells in autoimmune diseases

Stem cell-like memory T (TSCM) cell is a memory T cell subset with characteristics of long life span, consistent self-renewing, and the multipotent capacity to reconstitute the memory and effector T cell subsets. TSCM cell is the least differentiated cell in the memory T lymphocyte system, endowed with the stem cell-like ability, and it is essential for maintaining functional immunity. In addition, owing to its robust potential for immune reconstitution, it is central player in many physiological and pathological human processes. TSCM cell plays an important role in the occurrence and development of various autoimmune diseases. The specific role of TSCM cell in autoimmune diseases may make it a potential target for the treatment of multiple autoimmune diseases, driving effective immune reconstitution in therapy.

CAR T Cell Therapy: Remedies of Current Challenges in Design, Injection, Infiltration and Working

Chimeric antigen receptor (CAR) T cell therapy, as an innovative immunotherapy, plays a huge role in current cancer therapy. Although CAR T cell therapy has demonstrated therapeutic effects in some subtypes of B cell leukemia or lymphoma, there are many challenges that limit the therapeutic efficacy of CAR T cells in solid tumors. And how to efficiently transport CAR T cells to tumor tissues is a continuing concern for us. In this review, experiments have been extensively studied and compared. We finally compared the influence of different injection methods on therapeutic efficacy. We also carefully explored the difficulties of designing, homing, and working of CAR T cells, and ultimately came up with better solutions for each process to help CAR T cells reach tumor tissue more efficiently and quickly. These results will have significant implications for guiding CAR T cell therapy in cancer treatment.

Comparative Evaluation of Synthetic Cytokines for Enhancing Production and Performance of NK92 Cell-Based Therapies

Off-the shelf immune cell therapies are potentially curative and may offer cost and manufacturing advantages over autologous products, but further development is needed. The NK92 cell line has a natural killer-like phenotype, has efficacy in cancer clinical trials, and is safe after irradiation. However, NK92 cells lose activity post-injection, limiting efficacy. This may be addressed by engineering NK92 cells to express stimulatory factors, and comparative analysis is needed. Thus, we systematically explored the expression of synthetic cytokines for enhancing NK92 cell production and performance. All synthetic cytokines evaluated (membrane-bound IL2 and IL15, and engineered versions of Neoleukin-2/15, IL15, IL12, and decoy resistant IL18) enhanced NK92 cell cytotoxicity. Engineered cells were preferentially expanded by expressing membrane-bound but not soluble synthetic cytokines, without compromising the radiosensitivity required for safety. Some membrane-bound cytokines conferred cell-contact independent paracrine activity, partly attributable to extracellular vesicles. Finally, we characterized interactions within consortia of differently engineered NK92 cells.

Advances in chimeric antigen receptor T cells therapy in the treatment of breast cancer

Breast cancer (BC) is the most frequently occurring cancer type seriously threatening the lives of women worldwide. Clinically, the high frequency of diverse resistance to current therapeutic strategies advocates a demand to develop novel and effective approaches for the efficient treatment of BC. The chimeric antigen receptor T (CAR-T) cells therapy, one of the immunotherapies, has displayed powerful capacity to specifically kill and eliminate tumors. Due to the success of CAR-T therapy achieved in treating hematological malignancy, the effect of CAR-T cells therapy has been tested in various human diseases including breast cancer. This review summarized and discussed the landscape of the CAR-T therapy for breast cancer, including the advances, challenge and countermeasure of CAR-T therapy in research and clinical application. The roles of potential antigen targets, tumor microenvironment, immune escape in regulating CAR-T therapy, the combination of CAR-T therapy with other therapeutic strategies to further enhance therapeutic efficacy of CAR-T treatment were also highlighted. Therefore, our review provided a comprehensive understanding of CAR-T cell therapy in breast cancer which will awake huge interests for future in-depth investigation of CAR-T based therapy in cancer treatment.

Strategies for Reducing Toxicity and Enhancing Efficacy of Chimeric Antigen Receptor T Cell Therapy in Hematological Malignancies

Chimeric antigen receptor T cell (CAR-T) therapy in hematologic malignancies has made great progress, but there are still some problems. First, T cells from tumor patients show an exhaustion phenotype; thus, the persistence and function of the CAR-Ts are poor, and achieving a satisfactory curative effect is difficult. Second, some patients initially respond well but quickly develop antigen-negative tumor recurrence. Thirdly, CAR-T treatment is not effective in some patients and is accompanied by severe side effects, such as cytokine release syndrome (CRS) and neurotoxicity. The solution to these problems is to reduce the toxicity and enhance the efficacy of CAR-T therapy. In this paper, we describe various strategies for reducing the toxicity and enhancing the efficacy of CAR-T therapy in hematological malignancies. In the first section, strategies for modifying CAR-Ts using gene-editing technologies or combining them with other anti-tumor drugs to enhance the efficacy of CAR-T therapy are introduced. The second section describes some methods in which the design and construction of CAR-Ts differ from the conventional process. The aim of these methods is to enhance the anti-tumor activity of CAR-Ts and prevent tumor recurrence. The third section describes modifying the CAR structure or installing safety switches to radically reduce CAR-T toxicity or regulating inflammatory cytokines to control the symptoms of CAR-T-associated toxicity. Together, the knowledge summarized herein will aid in designing better-suited and safer CAR-T treatment strategies.

Research progress of interleukin-15 in cancer immunotherapy

Interleukin-15 (IL-15) is a cytokine that belongs to the interleukin-2 (IL-2) family and is essential for the development, proliferation, and activation of immune cells, including natural killer (NK) cells, T cells and B cells. Recent studies have revealed that interleukin-15 also plays a critical role in cancer immunotherapy. Interleukin-15 agonist molecules have shown that interleukin-15 agonists are effective in inhibiting tumor growth and preventing metastasis, and some are undergoing clinical trials. In this review, we will summarize the recent progress in interleukin-15 research over the past 5 years, highlighting its potential applications in cancer immunotherapy and the progress of interleukin-15 agonist development.

Role of Cytokines and Growth Factors in the Manufacturing of iPSC-Derived Allogeneic Cell Therapy Products

Cytokines and other growth factors are essential for cell expansion, health, function, and immune stimulation. Stem cells have the additional reliance on these factors to direct differentiation to the appropriate terminal cell type. Successful manufacturing of allogeneic cell therapies from induced pluripotent stem cells (iPSCs) requires close attention to the selection and control of cytokines and factors used throughout the manufacturing process, as well as after administration to the patient. This paper employs iPSC-derived natural killer cell/T cell therapeutics to illustrate the use of cytokines, growth factors, and transcription factors at different stages of the manufacturing process, ranging from the generation of iPSCs to controlling of iPSC differentiation into immune-effector cells through the support of cell therapy after patient administration.

Gene-based delivery of immune-activating cytokines for cancer treatment

Tumors evolve together with the tumor microenvironment (TME) and reshape it towards immunosuppression. Immunostimulating cytokines can be used to revert this state leading to effective antitumor immune responses, but their exploitation as anticancer drugs has been hampered by severe toxicity associated with systemic administration. Local, TME-targeted delivery of immune activating cytokines can deploy their antitumoral function more effectively than systemic administration while, at the same time, avoiding exposure of healthy organs and limiting toxicity. Here, we review different gene and cell therapy platforms developed for tumor-directed cytokine delivery highlighting their potential for clinical translation.

Genetic engineering strategies to enhance antitumor reactivity and reduce alloreactivity for allogeneic cell-based cancer therapy

The realm of cell-based immunotherapy holds untapped potential for the development of next-generation cancer treatment through genetic engineering of chimeric antigen receptor (CAR)-engineered T (CAR-T) cell therapies for targeted eradication of cancerous malignancies. Such allogeneic "off-the-shelf" cell products can be advantageously manufactured in large quantities, stored for extended periods, and easily distributed to treat an exponential number of cancer patients. At current, patient risk of graft-versus-host disease (GvHD) and host-versus-graft (HvG) allorejection severely restrict the development of allogeneic CAR-T cell products. To address these limitations, a variety of genetic engineering strategies have been implemented to enhance antitumor efficacy, reduce GvHD and HvG onset, and improve the overall safety profile of T-cell based immunotherapies. In this review, we summarize these genetic engineering strategies and discuss the challenges and prospects these approaches provide to expedite progression of translational and clinical studies for adoption of a universal cell-based cancer immunotherapy.

Explorations of CRISPR/Cas9 for improving the long-term efficacy of universal CAR-T cells in tumor immunotherapy

Chimeric antigen receptor (CAR) T therapy has shown remarkable success in discovering novel CAR-T cell products for treating malignancies. Despite of successful results from clinical trials, CAR-T cell therapy is ineffective for long-term disease progression. Numerous challenges of CAR-T cell immunotherapy such as cell dysfunction, cytokine-related toxicities, TGF-β resistance, GvHD risks, antigen escape, restricted trafficking, and tumor cell infiltration still exist that hamper the safety and efficacy of CAR-T cells for malignancies. The accumulated data revealed that these challenges could be overcome with the advanced CRISPR genome editing technology, which is the most promising tool to knockout TRAC and HLA genes, inhibiting the effects of dominant negative receptors (PD-1, TGF-β, and B2M), lowering the risks of cytokine release syndrome (CRS), and regulating CAR-T cell function in the tumor microenvironment (TME). CRISPR technology employs DSB-free genome editing methods that robustly allow efficient and controllable genetic modification. The present review explored the innovative aspects of CRISPR/Cas9 technology for developing next-generation/universal allogeneic CAR-T cells. The present manuscript addressed the ongoing status of clinical trials of CRISPR/Cas9-engineered CAR-T cells against cancer and pointed out the off-target effects associated with CRISPR/Cas9 genome editing. It is concluded that CAR-T cells modified by CRISPR/Cas9 significantly improved antitumor efficacy in a cost-effective manner that provides opportunities for novel cancer immunotherapies.

Recent advances and applications of CRISPR-Cas9 in cancer immunotherapy

The incidence and mortality of cancer are the major health issue worldwide. Apart from the treatments developed to date, the unsatisfactory therapeutic effects of cancers have not been addressed by broadening the toolbox. The advent of immunotherapy has ushered in a new era in the treatments of solid tumors, but remains limited and requires breaking adverse effects. Meanwhile, the development of advanced technologies can be further boosted by gene analysis and manipulation at the molecular level. The advent of cutting-edge genome editing technology, especially clustered regularly interspaced short palindromic repeats (CRISPR-Cas9), has demonstrated its potential to break the limits of immunotherapy in cancers. In this review, the mechanism of CRISPR-Cas9-mediated genome editing and a powerful CRISPR toolbox are introduced. Furthermore, we focus on reviewing the impact of CRISPR-induced double-strand breaks (DSBs) on cancer immunotherapy (knockout or knockin). Finally, we discuss the CRISPR-Cas9-based genome-wide screening for target identification, emphasis the potential of spatial CRISPR genomics, and present the comprehensive application and challenges in basic research, translational medicine and clinics of CRISPR-Cas9.

CAR immune cells: design principles, resistance and the next generation

The remarkable clinical activity of chimeric antigen receptor (CAR) therapies in B cell and plasma cell malignancies has validated the use of this therapeutic class for liquid cancers, but resistance and limited access remain as barriers to broader application. Here we review the immunobiology and design principles of current prototype CARs and present emerging platforms that are anticipated to drive future clinical advances. The field is witnessing a rapid expansion of next-generation CAR immune cell technologies designed to enhance efficacy, safety and access. Substantial progress has been made in augmenting immune cell fitness, activating endogenous immunity, arming cells to resist suppression via the tumour microenvironment and developing approaches to modulate antigen density thresholds. Increasingly sophisticated multispecific, logic-gated and regulatable CARs display the potential to overcome resistance and increase safety. Early signs of progress with stealth, virus-free and in vivo gene delivery platforms provide potential paths for reduced costs and increased access of cell therapies in the future. The continuing clinical success of CAR T cells in liquid cancers is driving the development of increasingly sophisticated immune cell therapies that are poised to translate to treatments for solid cancers and non-malignant diseases in the coming years.

IL15 modification enables CAR T cells to act as a dual targeting agent against tumor cells and myeloid-derived suppressor cells in GBM

INTRODUCTION

The immunosuppressive tumor microenvironment (TME) is a major barrier to the efficacy of chimeric antigen receptor T cells (CAR-T cells) in glioblastoma (GBM). Transgenic expression of IL15 is one attractive strategy to modulate the TME. However, at present, it is unclear if IL15 could be used to directly target myeloid-derived suppressor cells (MDSCs), a major cellular component of the GBM TME. Here, we explored if MDSC express IL15Rα and the feasibility of exploiting its expression as an immunotherapeutic target.

METHODS

RNA-seq, RT-qPCR, and flow cytometry were used to determine IL15Rα expression in paired peripheral and tumor-infiltrating immune cells of GBM patients and two syngeneic murine GBM models. We generated murine T cells expressing IL13Rα2-CARs and secretory IL15 (CAR.IL15s) or IL13Rα2-CARs in which IL15 was fused to the CAR to serve as an IL15Rα-targeting moiety (CAR.IL15f), and characterized their effector function in vitro and in syngeneic IL13Rα2+glioma models.

RESULTS

IL15Rα was preferentially expressed in myeloid, B, and dendritic cells in patients' and syngeneic GBMs. In vitro, CAR.IL15s and CAR.IL15f T cells depleted MDSC and decreased their secretion of immunosuppressive molecules with CAR.IL15f T cells being more efficacious. Similarly, CAR.IL15f T cells significantly improved the survival of mice in two GBM models. TME analysis showed that treatment with CAR.IL15f T cells resulted in higher frequencies of CD8+T cells, NK, and B cells, but a decrease in CD11b+cells in tumors compared with therapy with CAR T cells.

CONCLUSIONS

We demonstrate that MDSC of the glioma TME express IL15Ra and that these cells can be targeted with secretory IL15 or an IL15Rα-targeting moiety incorporated into the CAR. Thus, IL15-modified CAR T cells act as a dual targeting agent against tumor cells and MDSC in GBM, warranting their future evaluation in early-phase clinical studies.

CARs and Drugs: Pharmacological Ways of Boosting CAR-T-Cell Therapy

The development of chimeric antigen receptor T cells (CAR-T cells) has marked a new era in cancer immunotherapy. Based on a multitude of durable complete remissions in patients with hematological malignancies, FDA and EMA approval was issued to several CAR products targeting lymphoid leukemias and lymphomas. Nevertheless, about 50% of patients treated with these approved CAR products experience relapse or refractory disease necessitating salvage strategies. Moreover, in the vast majority of patients suffering from solid tumors, CAR-T-cell infusions could not induce durable complete remissions so far. Crucial obstacles to CAR-T-cell therapy resulting in a priori CAR-T-cell refractory disease or relapse after initially successful CAR-T-cell therapy encompass antigen shutdown and CAR-T-cell dysfunctionality. Antigen shutdown predominately rationalizes disease relapse in hematological malignancies, and CAR-T-cell dysfunctionality is characterized by insufficient CAR-T-cell proliferation and cytotoxicity frequently observed in patients with solid tumors. Thus, strategies to surmount those obstacles are being developed with high urgency. In this review, we want to highlight different approaches to combine CAR-T cells with drugs, such as small molecules and antibodies, to pharmacologically boost CAR-T-cell therapy. In particular, we discuss how certain drugs may help to counteract antigen shutdown and CAR-T-cell dysfunctionality in both hematological malignancies and solid tumors.

CAR T cell therapy becomes CHIC: "cytokine help intensified CAR" T cells

Chimeric antigen receptors (CARs) in the canonical "second generation" format provide two signals for inducing T cell effector functions; the primary "signal-1" is provided through the TCR CD3ζ chain and the "signal-2" through a linked costimulatory domain to augment activation. While therapy with second generation CAR T cells can induce remissions of leukemia/lymphoma in a spectacular fashion, CAR T cell persistence is frequently limited which is thought to be due to timely limited activation. Following the "three-signal" dogma for inducing a sustained T cell response, cytokines were supplemented to provide "signal-3" to CAR T cells. Recent progress in the understanding of structural biology and receptor signaling has allowed to engineer cytokines for more selective, fine-tuned stimulation of CAR T cells including an artificial autocrine loop of a transgenic cytokine, a cytokine anchored to the CAR T cell membrane or inserted into the extracellular CAR domain, and a cytokine receptor signaling moiety co-expressed with the CAR or inserted into the CAR endodomain. Here we discuss the recent strategies and options for engineering such "cytokine help intensified CAR" (CHIC) T cells for use in adoptive cell therapy.

Antigen-dependent IL-12 signaling in CAR T cells promotes regional to systemic disease targeting

Chimeric antigen receptor (CAR) T cell therapeutic responses are hampered by limited T cell trafficking, persistence, and durable anti-tumor activity in solid tumor microenvironments. However, these challenges can be largely overcome by relatively unconstrained synthetic engineering strategies, which are being harnessed to improve solid tumor CAR T cell therapies. Here, we describe fully optimized CAR T cells targeting tumor-associated glycoprotein-72 (TAG72) for the treatment of solid tumors, identifying the CD28 transmembrane domain upstream of the 4-1BB co-stimulatory domain as a driver of potent anti-tumor activity and IFNγ secretion. These findings have culminated into a phase 1 trial evaluating safety, feasibility, and bioactivity of TAG72-CAR T cells for the treatment of patients with advanced ovarian cancer ( NCT05225363 ). Preclinically, we found that CAR T cell-mediated IFNγ production facilitated by IL-12 signaling was required for tumor cell killing, which was recapitulated by expressing an optimized membrane-bound IL-12 (mbIL12) molecule on CAR T cells. Critically, mbIL12 cell surface expression and downstream signaling was induced and sustained only following CAR T cell activation. CAR T cells with mbIL12 demonstrated improved antigen-dependent T cell proliferation and potent cytotoxicity in recursive tumor cell killing assays in vitro and showed robust in vivo anti-tumor efficacy in human xenograft models of ovarian cancer peritoneal metastasis. Further, locoregional administration of TAG72-CAR T cells with antigen-dependent IL-12 signaling promoted durable anti-tumor responses against both regional and systemic disease in mice and was associated with improved systemic T cell persistence. Our study features a clinically-applicable strategy to improve the overall efficacy of locoregionally-delivered CAR T cells engineered with antigen-dependent immune-modulating cytokines in targeting both regional and systemic disease.

Immune-based therapies in diffuse large B-cell lymphoma

INTRODUCTION

Diffuse large B-cell lymphoma (DLBCL) is an aggressive and clinically heterogeneous malignancy originating from B-cells with up to 40% of patients experiencing primary refractory disease or relapse after first-line treatment. However, the past 5 years have seen a flurry of new drug approvals for DLBCL anchored upon new immune therapies, including chimeric antigen receptor (CAR) T-cells and antibody-based therapies.

AREAS COVERED

This article summarizes recent advances in the treatment of DLBCL, including in the first line and relapsed and refractory setting (second-line and beyond). A literature search was conducted for publications relevant to the immunotherapeutic approach to DLBCL from 2000 through March 2023 within PubMed and articles were reviewed. The search terms were immunotherapy, monoclonal antibodies, chimeric antigen receptor modified T-cell (CAR-T), and classification of DLBCL. Relevant clinical trials and pre-clinical studies exploring the strengths and weaknesses of current immune therapies against DLBCL were chosen. We additionally explored how intrinsic differences amongst DLBCL subtype biology and endogenous host immune recruitment contribute to variable therapeutic efficacy.

EXPERT OPINION

Future treatments will minimize chemotherapy exposure and be chosen by underlying tumor biology, paving the way for the promise of chemotherapeutic free regimens and improved outcomes for poor-risk subgroups.

Reprogramming of IL-12 secretion in the PDCD1 locus improves the anti-tumor activity of NY-ESO-1 TCR-T cells

Introduction

Although the engineering of T cells to co-express immunostimulatory cytokines has been shown to enhance the therapeutic efficacy of adoptive T cell therapy, the uncontrolled systemic release of potent cytokines can lead to severe adverse effects. To address this, we site-specifically inserted the interleukin-12 (IL-12) gene into the PDCD1 locus in T cells using clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9)-based genome editing to achieve T-cell activation-dependent expression of IL-12 while ablating the expression of inhibitory PD-1.

Methods

New York esophageal squamous cell carcinoma 1(NY-ESO-1)-specific TCR-T cells was investigated as a model system. We generated ΔPD-1-IL-12 -edited NY-ESO-1 TCR-T cells by sequential lentiviral transduction and CRISPR knock-in into activated human primary T cells.

Results

We showed that the endogenous PDCD1 regulatory elements can tightly control the secretion of recombinant IL-12 in a target cell-dependent manner, at an expression level that is more moderate than that obtained using a synthetic NFAT-responsive promoter. The inducible expression of IL-12 from the PDCD1 locus was sufficient to enhance the effector function of NY-ESO-1 TCR-T cells, as determined by upregulation of effector molecules, increased cytotoxic activity, and enhanced expansion upon repeated antigen stimulation in vitro. Mouse xenograft studies also revealed that PD-1-edited IL-12-secreting NY-ESO-1 TCR-T cells could eliminate established tumors and showed significantly greater in vivo expansion capacity than control TCR-T cells.

Discussion

Our approach may provide a way to safely harness the therapeutic potential of potent immunostimulatory cytokines for the development of effective adoptive T cell therapies against solid tumors.

Optimization of the proliferation and persistency of CAR T cells derived from human induced pluripotent stem cells

The effectiveness of chimaeric antigen receptor (CAR) T-cell immunotherapies against solid tumours relies on the accumulation, proliferation and persistency of T cells at the tumour site. Here we show that the proliferation of CD8αβ cytotoxic CAR T cells in solid tumours can be enhanced by deriving and expanding them from a single human induced-pluripotent-stem-cell clone bearing a CAR selected for efficient differentiation. We also show that the proliferation and persistency of the effector cells in the tumours can be further enhanced by genetically knocking out diacylglycerol kinase, which inhibits antigen-receptor signalling, and by transducing the cells with genes encoding for membrane-bound interleukin-15 (IL-15) and its receptor subunit IL-15Rα. In multiple tumour-bearing animal models, the engineered hiPSC-derived CAR T cells led to therapeutic outcomes similar to those of primary CD8 T cells bearing the same CAR. The optimization of effector CAR T cells derived from pluripotent stem cells may aid the development of long-lasting antigen-specific T-cell immunotherapies for the treatment of solid tumours.

The peculiar challenge of bringing CAR-T cells into the brain: Perspectives in the clinical application to the treatment of pediatric central nervous system tumors

Childhood malignant brain tumors remain a significant cause of death in the pediatric population, despite the use of aggressive multimodal treatments. New therapeutic approaches are urgently needed for these patients in order to improve prognosis, while reducing side effects and long-term sequelae of the treatment. Immunotherapy is an attractive option and, in particular, the use of gene-modified T cells expressing a chimeric antigen receptor (CAR-T cells) represents a promising approach. Major hurdles in the clinical application of this approach in neuro-oncology, however, exist. The peculiar location of brain tumors leads to both a difficulty of access to the tumor mass, shielded by the blood-brain barrier (BBB), and to an increased risk of potentially life-threatening neurotoxicity, due to the primary location of the disease in the CNS and the low intracranial volume reserve. There are no unequivocal data on the best way of CAR-T cell administration. Multiple trials exploring the use of CD19 CAR-T cells for hematologic malignancies proved that genetically engineered T cells can cross the BBB, suggesting that systemically administered CAR-T cell can be used in the neuro-oncology setting. Intrathecal and intra-tumoral delivery can be easily managed with local implantable devices, suitable also for a more precise neuro-monitoring. The identification of specific approaches of neuro-monitoring is of utmost importance in these patients. In the present review, we highlight the most relevant potential challenges associated with the application of CAR-T cell therapy in pediatric brain cancers, focusing on the evaluation of the best route of delivery, the peculiar risk of neurotoxicity and the related neuro-monitoring.

The role of interleukin-15 in the development and treatment of hematological malignancies

Cytokines are a vital component of the immune system that controls the activation and growth of blood cells. However, chronic overexpression of cytokines can trigger cellular events leading to malignant transformation. The cytokine interleukin-15 (IL-15) is of particular interest, which has been shown to contribute to the development and progression of various hematological malignancies. This review will provide an overview of the impact of the immunopathogenic function of IL-15 by studying its role in cell survival, proliferation, inflammation, and treatment resistance. We will also review therapeutic approaches for inhibiting IL-15 in blood cancers.

T-cell exhaustion and stemness in antitumor immunity: Characteristics, mechanisms, and implications

T cells play a crucial role in the regulation of immune response and are integral to the efficacy of cancer immunotherapy. Because immunotherapy has emerged as a promising treatment for cancer, increasing attention has been focused on the differentiation and function of T cells in immune response. In this review, we describe the research progress on T-cell exhaustion and stemness in the field of cancer immunotherapy and summarize advances in potential strategies to intervene and treat chronic infection and cancer by reversing T-cell exhaustion and maintaining and increasing T-cell stemness. Moreover, we discuss therapeutic strategies to overcome T-cell immunodeficiency in the tumor microenvironment and promote continuous breakthroughs in the anticancer activity of T cells.

Interleukin-15 and chemokine ligand 19 enhance cytotoxic effects of chimeric antigen receptor T cells using zebrafish xenograft model of gastric cancer

Chimeric antigen receptor (CAR) T cells have been proven effective for the treatment of B-cell-mediated malignancies. Currently, the development of efficient tools that supply CAR T cells for the treatment of other malignancies would have great impact. In this study, interleukin (IL)-15 and C-C motif chemokine ligand 19 (CCL19) were introduced into natural killer group 2D (NKG2D)-based CARs to generate 15×19 CAR T cells, which remarkably increased T-cell expansion and promoted the production of central memory T (T_cm) cells. 15×19 CAR T cells showed greater cytotoxicity to gastric cell lines than conventional CAR T cells and produced higher levels of IL-15 and CCL-19, which resulted in increased responder T cell chemotaxis and reduced expression of T cell exhaustion markers. A live zebrafish model was used for single-cell visualization of local cytotoxicity and metastatic cancers. Administration of 15×19 CAR T cells resulted in significant shrinking of gastric cancer xenograft tumors and expansion of 15×19 CAR T cells in zebrafish models. Taken together, these findings demonstrate that 15×19 CAR T cells are highly efficient in killing gastric cancer cells, are effective to avoid off-target effects, and migrate to local and metastatic sites for long-term surveillance of cancers.

Activation of cancer immunotherapy by nanomedicine

Cancer is one of the most difficult diseases to be treated in the world. Immunotherapy has made great strides in cancer treatment in recent years, and several tumor immunotherapy drugs have been approved by the U.S. Food and Drug Administration. Currently, immunotherapy faces many challenges, such as lacking specificity, cytotoxicity, drug resistance, etc. Nanoparticles have the characteristics of small particle size and stable surface function, playing a miraculous effect in anti-tumor treatment. Nanocarriers such as polymeric micelles, liposomes, nanoemulsions, dendrimers, and inorganic nanoparticles have been widely used to overcome deficits in cancer treatments including toxicity, insufficient specificity, and low bioavailability. Although nanomedicine research is extensive, only a few nanomedicines are approved to be used. Either Bottlenecks or solutions of nanomedicine in immunotherapy need to be further explored to cope with challenges. In this review, a brief overview of several types of cancer immunotherapy approaches and their advantages and disadvantages will be provided. Then, the types of nanomedicines, drug delivery strategies, and the progress of applications are introduced. Finally, the application and prospect of nanomedicines in immunotherapy and Chimeric antigen receptor T-cell therapy (CAR-T) are highlighted and summarized to address the problems of immunotherapy the overall goal of this article is to provide insights into the potential use of nanomedicines and to improve the efficacy and safety of immunotherapy.

Synthetic cytokine circuits that drive T cells into immune-excluded tumors

Chimeric antigen receptor (CAR) T cells are ineffective against solid tumors with immunosuppressive microenvironments. To overcome suppression, we engineered circuits in which tumor-specific synNotch receptors locally induce production of the cytokine IL-2. These circuits potently enhance CAR T cell infiltration and clearance of immune-excluded tumors, without systemic toxicity. The most effective IL-2 induction circuit acts in an autocrine and T cell receptor (TCR)- or CAR-independent manner, bypassing suppression mechanisms including consumption of IL-2 or inhibition of TCR signaling. These engineered cells establish a foothold in the target tumors, with synthetic Notch-induced IL-2 production enabling initiation of CAR-mediated T cell expansion and cell killing. Thus, it is possible to reconstitute synthetic T cell circuits that activate the outputs ultimately required for an antitumor response, but in a manner that evades key points of tumor suppression.

The future of engineered immune cell therapies

Immune cells are being engineered to recognize and respond to disease states, acting as a "living drug" when transferred into patients. Therapies based on engineered immune cells are now a clinical reality, with multiple engineered T cell therapies approved for treatment of hematologic malignancies. Ongoing preclinical and clinical studies are testing diverse strategies to modify the fate and function of immune cells for applications in cancer, infectious disease, and beyond. Here, we discuss current progress in treating human disease with immune cell therapeutics, emerging strategies for immune cell engineering, and challenges facing the field, with a particular emphasis on the treatment of cancer, where the most effort has been applied to date.

CAR-T cell combination therapy: the next revolution in cancer treatment

In recent decades, the advent of immune-based therapies, most notably Chimeric antigen receptor (CAR)-T cell therapy has revolutionized cancer treatment. The promising results of numerous studies indicate that CAR-T cell therapy has had a remarkable ability and successful performance in treating blood cancers. However, the heterogeneity and immunosuppressive tumor microenvironment (TME) of solid tumors have challenged the effectiveness of these anti-tumor fighters by creating various barriers. Despite the promising results of this therapeutic approach, including tumor degradation and patient improvement, there are some concerns about the efficacy and safety of the widespread use of this treatment in the clinic. Complex and suppressing tumor microenvironment, tumor antigen heterogeneity, the difficulty of cell trafficking, CAR-T cell exhaustion, and reduced cytotoxicity in the tumor site limit the applicability of CAR-T cell therapy and highlights the requiring to improve the performance of this treatment. With this in mind, in the last decade, many efforts have been made to use other treatments for cancer in combination with tuberculosis to increase the effectiveness of CAR-T cell therapy, especially in solid tumors. The combination therapy results have promising consequences for tumor regression and better cancer control compared to single therapies. Therefore, this study aimed to comprehensively discuss different cancer treatment methods in combination with CAR-T cell therapy and their therapeutic outcomes, which can be a helpful perspective for improving cancer treatment in the near future.

Multiplexed engineering and precision gene editing in cellular immunotherapy

The advent of cellular immunotherapy in the clinic has entirely redrawn the treatment landscape for a growing number of human cancers. Genetically reprogrammed immune cells, including chimeric antigen receptor (CAR)-modified immune effector cells as well as T cell receptor (TCR) therapy, have demonstrated remarkable responses across different hard-to-treat patient populations. While these novel treatment options have had tremendous success in providing long-term remissions for a considerable fraction of treated patients, a number of challenges remain. Limited in vivo persistence and functional exhaustion of infused immune cells as well as tumor immune escape and on-target off-tumor toxicities are just some examples of the challenges which restrain the potency of today's genetically engineered cell products. Multiple engineering strategies are being explored to tackle these challenges.The advent of multiplexed precision genome editing has in recent years provided a flexible and highly modular toolkit to specifically address some of these challenges by targeted genetic interventions. This class of next-generation cellular therapeutics aims to endow engineered immune cells with enhanced functionality and shield them from immunosuppressive cues arising from intrinsic immune checkpoints as well as the hostile tumor microenvironment (TME). Previous efforts to introduce additional genetic modifications into immune cells have in large parts focused on nuclease-based tools like the CRISPR/Cas9 system or TALEN. However, nuclease-inactive platforms including base and prime editors have recently emerged and promise a potentially safer route to rewriting genetic sequences and introducing large segments of transgenic DNA without inducing double-strand breaks (DSBs). In this review, we discuss how these two exciting and emerging fields-cellular immunotherapy and precision genome editing-have co-evolved to enable a dramatic expansion in the possibilities to engineer personalized anti-cancer treatments. We will lay out how various engineering strategies in addition to nuclease-dependent and nuclease-inactive precision genome editing toolkits are increasingly being applied to overcome today's limitations to build more potent cellular therapeutics. We will reflect on how novel information-rich unbiased discovery approaches are continuously deepening our understanding of fundamental mechanisms governing tumor biology. We will conclude with a perspective of how multiplexed-engineered and gene edited cell products may upend today's treatment paradigms as they evolve into the next generation of more potent cellular immunotherapies.

Sleeping beauty generated CD19 CAR T-Cell therapy for advanced B-Cell hematological malignancies

Chimeric antigen receptor (CAR) T-cell therapy has emerged recently as a standard of care treatment for patients with relapsed or refractory acute lymphoblastic leukemia (ALL) and several subtypes of B-cell non-Hodgkin lymphoma (NHL). However, its use remains limited to highly specialized centers, given the complexity of its administration and its associated toxicities. We previously reported our experience in using a novel Sleeping Beauty (SB) CD19-specific CAR T-cell therapy in the peri-transplant setting, where it exhibited an excellent safety profile with encouraging survival outcomes. We have since modified the SB CD19 CAR construct to improve its efficacy and shorten its manufacturing time. We report here the phase 1 clinical trial safety results. Fourteen heavily treated patients with relapsed/refractory ALL and NHL were infused. Overall, no serious adverse events were directly attributed to the study treatment. Three patients developed grades 1-2 cytokine release syndrome and none of the study patients experienced neurotoxicity. All dose levels were well tolerated and no dose-limiting toxicities were reported. For efficacy, 3 of 8 (38%) patients with ALL achieved CR/CRi (complete remission with incomplete count recovery) and 1 (13%) patient had sustained molecular disease positivity. Of the 4 patients with DLBCL, 2 (50%) achieved CR. The SB-based CAR constructs allow manufacturing of targeted CAR T-cell therapies that are safe, cost-effective and with encouraging antitumor activity.

Neomorphic DNA-binding enables tumor-specific therapeutic gene expression in fusion-addicted childhood sarcoma

Chimeric fusion transcription factors are oncogenic hallmarks of several devastating cancer entities including pediatric sarcomas, such as Ewing sarcoma (EwS) and alveolar rhabdomyosarcoma (ARMS). Despite their exquisite specificity, these driver oncogenes have been considered largely undruggable due to their lack of enzymatic activity.

Here, we show in the EwS model that – capitalizing on neomorphic DNA-binding preferences – the addiction to the respective fusion transcription factor EWSR1-FLI1 can be leveraged to express therapeutic genes.

We genetically engineered a de novo enhancer-based, synthetic and highly potent expression cassette that can elicit EWSR1-FLI1-dependent expression of a therapeutic payload as evidenced by episomal and CRISPR-edited genomic reporter assays. Combining in silico screens and immunohistochemistry, we identified GPR64 as a highly specific cell surface antigen for targeted transduction strategies in EwS. Functional experiments demonstrated that anti-GPR64-pseudotyped lentivirus harboring our expression cassette can specifically transduce EwS cells to promote the expression of viral thymidine kinase sensitizing EwS for treatment to otherwise relatively non-toxic (Val)ganciclovir and leading to strong anti-tumorigenic, but no adverse effects in vivo. Further, we prove that similar vector designs can be applied in PAX3-FOXO1-driven ARMS, and to express immunomodulatory cytokines, such as IL-15 and XCL1, in tumor entities typically considered to be immunologically ‘cold’.

Collectively, these results generated in pediatric sarcomas indicate that exploiting, rather than suppressing, the neomorphic functions of chimeric transcription factors may open inroads to innovative and personalized therapies, and that our highly versatile approach may be translatable to other cancers addicted to oncogenic transcription factors with unique DNA-binding properties.

CAR-T cell therapy for hematological malignancies: Limitations and optimization strategies

In the past decade, the emergence of chimeric antigen receptor (CAR) T-cell therapy has led to a cellular immunotherapy revolution against various cancers. Although CAR-T cell therapies have demonstrated remarkable efficacy for patients with certain B cell driven hematological malignancies, further studies are required to broaden the use of CAR-T cell therapy against other hematological malignancies. Moreover, treatment failure still occurs for a significant proportion of patients. CAR antigen loss on cancer cells is one of the most common reasons for cancer relapse. Additionally, immune evasion can arise due to the hostile immunosuppressive tumor microenvironment and the impaired CAR-T cells in vivo persistence. Other than direct antitumor activity, the adverse effects associated with CAR-T cell therapy are another major concern during treatment. As a newly emerged treatment approach, numerous novel preclinical studies have proposed different strategies to enhance the efficacy and attenuate CAR-T cell associated toxicity in recent years. The major obstacles that impede promising outcomes for patients with hematological malignancies during CAR-T cell therapy have been reviewed herein, along with recent advancements being made to surmount them.

CRISPR/Cas9 encouraged CAR-T cell immunotherapy reporting efficient and safe clinical results towards cancer

CRISPR is a customized genome-editing tool that snips DNA in a simpler, cheaper and more precise way than any other gene editing tool. In recent years CRISPR/Cas has completely transformed an existing discipline of genetic engineering. This 'review' focuses on the generations and modifications in CAR-T as an advanced cancer therapeutic tool and CAR-T-approved products. It also highlights three path-breaking successful autologous and allogenic ex vivo CAR-T clinical trials in treating cancer using CRISPR/Cas9 which reported successful results despite the controversies regarding the safety of this technique. Outcomes from the first successful clinical trial showed the beneficial long-term effect on genetically modified T-cells in targeting cancer cells which opens the door for CRISPR to be the most preferred technique to help treat cancer and other diseases in the future. We searched the MEDLINE, EMBASE and PUBMED databases for original studies and meta-analysis on the use of CRISPR/Cas9 to edit T-cells until 2021. We finally selected 15 pre-clinical and 26 clinical studies for the review.

Co-expression IL-15 receptor alpha with IL-15 reduces toxicity via limiting IL-15 systemic exposure during CAR-T immunotherapy

Background

Chimeric antigen receptor (CAR)-T cell therapy is a powerful adoptive immunotherapy against both B-cell malignancies and some types of solid tumors. Interleukin (IL) -15 is an important immune stimulator that may provide ideal long-term persistent CAR-T cells. However, higher base line or peak serum IL-15 levels are also related to severe toxicity, such as cytokine release syndrome (CRS), graft-versus-host disease (GVHD), and neurotoxicity.

Methods

We successfully constructed CD19 specific armored CAR-T cells overexpressing IL-I5 and IL-15 receptor alpha (IL-15Ra). In vitro cell differentiation and viability were monitored by flow cytometry, and an in vivo xenograft mouse models was used to evaluate the anti-tumor efficiency and liver damage of CAR-T cells.

Results

CAR-T cells overexpressing IL-15 alone demonstrated enhanced viability, retarded exhaustion in vitro and superior tumor-inhibitory effects in vivo. However, these tumor-free mice had lower survival rates, with serious liver injuries, as a possible result of toxicity. As expected, CAR-T cells overexpressing IL-15 combined with IL-15Ra had reduced CD132 expression and released fewer cytokines (IFNγ, IL-2 and IL-15) in vitro, as well as had the tendency to improve mouse survival via repressing the growth of tumor cells and keeping livers healthier compared to CAR-IL-15 T cells.

Conclusions

These results indicated the importance of IL-15 in enhancing T cells persistence and IL-15Ra in reducing the adverse effects of IL-15, with superior tumor retardation during CAR-T therapy. This study paves the way for the rapid exploitation of IL-15 in adoptive cell therapy in the future.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12967-022-03626-x.

Treatment of aggressive T-cell lymphoma/leukemia with anti-CD4 CAR T cells

T-cell lymphomas are aggressive lymphomas that often resist current therapy options or present with relapsed disease, making the development of more effective treatment regimens clinically important. Previously, we have shown that CD4 CAR can effectively target T-cell malignancies in preclinical studies. As IL-15 has been shown to strengthen the anti-tumor response, we have modified CD4 CAR to secrete an IL-15/IL-15sushi complex. These CD4-IL15/IL15sushi CAR T cells and NK92 cells efficiently eliminated CD4+ leukemic cell lines in co-culture assays. Additionally, CD4-IL15/IL15sushi CAR out-performed CD4 CAR in in vivo models, demonstrating a benefit to IL-15/IL-15sushi inclusion. In a Phase I clinical trial, CD4-IL15/IL15sushi CAR T cells were tested for safety in three patients with different T-cell lymphomas. Infusion of CD4-IL15/IL15sushi CAR T cells was well-tolerated by the patients without significant adverse effects and led to the remission of their lymphomas. Additionally, infusion led to the depletion of CD4+ Treg cells and expansion of CD3+CD8+ T cells and NK cells. These results suggest that CD4-IL15/IL15sushi CAR T cells may be a safe and effective treatment for patients with relapsed or refractory T-cell lymphomas, where new treatment options are needed.

Non-viral, specifically targeted CAR-T cells achieve high safety and efficacy in B-NHL

Recently, chimeric antigen receptor (CAR)-T cell therapy has shown great promise in treating haematological malignancies^1–7. However, CAR-T cell therapy currently has several limitations^8–12. Here we successfully developed a two-in-one approach to generate non-viral, gene-specific targeted CAR-T cells through CRISPR–Cas9. Using the optimized protocol, we demonstrated feasibility in a preclinical study by inserting an anti-CD19 CAR cassette into the AAVS1 safe-harbour locus. Furthermore, an innovative type of anti-CD19 CAR-T cell with PD1 integration was developed and showed superior ability to eradicate tumour cells in xenograft models. In adoptive therapy for relapsed/refractory aggressive B cell non-Hodgkin lymphoma (ClinicalTrials.gov, NCT04213469), we observed a high rate (87.5%) of complete remission and durable responses without serious adverse events in eight patients. Notably, these enhanced CAR-T cells were effective even at a low infusion dose and with a low percentage of CAR⁺ cells. Single-cell analysis showed that the electroporation method resulted in a high percentage of memory T cells in infusion products, and PD1 interference enhanced anti-tumour immune functions, further validating the advantages of non-viral, PD1-integrated CAR-T cells. Collectively, our results demonstrate the high safety and efficacy of non-viral, gene-specific integrated CAR-T cells, thus providing an innovative technology for CAR-T cell therapy.

Non-viral CAR-T cells with gene-specific targeted integration are safe and effective in patients with lymphoma.

Paving the Way to Solid Tumors: Challenges and Strategies for Adoptively Transferred Transgenic T Cells in the Tumor Microenvironment

T cells are important players in the antitumor immune response. Over the past few years, the adoptive transfer of genetically modified, autologous T cells-specifically redirected toward the tumor by expressing either a T cell receptor (TCR) or a chimeric antigen receptor (CAR)-has been adopted for use in the clinic. At the moment, the therapeutic application of CD19- and, increasingly, BCMA-targeting-engineered CAR-T cells have been approved and have yielded partly impressive results in hematologic malignancies. However, employing transgenic T cells for the treatment of solid tumors remains more troublesome, and numerous hurdles within the highly immunosuppressive tumor microenvironment (TME) need to be overcome to achieve tumor control. In this review, we focused on the challenges that these therapies must face on three different levels: infiltrating the tumor, exerting efficient antitumor activity, and overcoming T cell exhaustion and dysfunction. We aimed to discuss different options to pave the way for potent transgenic T cell-mediated tumor rejection by engineering either the TME or the transgenic T cell itself, which responds to the environment.

Secretory co-factors in next-generation cellular therapies for cancer

Since chimeric antigen receptor (CAR) T-cell therapies for hematologic malignancies were approved by the U.S. Food and Drug Administration, numerous "next-generation" CAR T cells have been developed to improve their safety, efficacy, and applicability. Although some of these novel therapeutic strategies are promising, it remains difficult to apply these therapies to solid tumors and to control adverse effects, such as cytokine release syndrome and neurotoxicity. CAR T cells are generated using highly scalable genetic engineering techniques. One of the major strategies for producing next-generation CAR T cells involves the integration of useful co-factor(s) into the artificial genetic design of the CAR gene, resulting in next-generation CAR T cells that express both CAR and the co-factor(s). Many soluble co-factors have been reported for CAR T cells and their therapeutic effects and toxicity have been tested by systemic injection; therefore, CAR T cells harnessing secretory co-factors could be close to clinical application. Here, we review the various secretory co-factors that have been reported to improve the therapeutic efficacy of CAR T cells and ameliorate adverse events. In addition, we discuss the different co-factor expression systems that have been used to optimize their beneficial effects. Altogether, we demonstrate that combining CAR T cells with secretory co-factors will lead to next-generation CAR T-cell therapies that can be used against broader types of cancers and might provide advanced tools for more complicated synthetic immunotherapies.

HIV cure strategies: which ones are appropriate for Africa?

Although combination antiretroviral therapy (ART) has reduced mortality and improved lifespan for people living with HIV, it does not provide a cure. Patients must be on ART for the rest of their lives and contend with side effects, unsustainable costs, and the development of drug resistance. A cure for HIV is, therefore, warranted to avoid the limitations of the current therapy and restore full health. However, this cure is difficult to find due to the persistence of latently infected HIV cellular reservoirs during suppressive ART. Approaches to HIV cure being investigated include boosting the host immune system, genetic approaches to disable co-receptors and the viral genome, purging cells harboring latent HIV with latency-reversing latency agents (LRAs) (shock and kill), intensifying ART as a cure, preventing replication of latent proviruses (block and lock) and boosting T cell turnover to reduce HIV-1 reservoirs (rinse and replace). Since most people living with HIV are in Africa, methods being developed for a cure must be amenable to clinical trials and deployment on the continent. This review discusses the current approaches to HIV cure and comments on their appropriateness for Africa.