Practical considerations for chimeric antigen receptor design and delivery

A new vision of the efficacy of both CAR-NK and CAR-T cells in treating cancers and autoimmune diseases

Chimeric Antigen Receptor (CAR) based therapies are becoming increasingly important in treating patients. CAR-T cells have been shown to be highly effective in the treatment of hematological malignancies. However, harmful therapeutic barriers have been identified, such as the potential for graft-versus-host disease (GVHD), neurotoxicity, and cytokine release syndrome (CRS). As a result, CAR NK-cell therapy is expected to be a new therapeutic option. NK cells act as cytotoxic lymphocytes, supporting the innate immune response against autoimmune diseases and cancer cells by precisely detecting and eliminating malignant cells. Genetic modification of these cells provides a dual approach to the treatment of AD and cancer. It can be used through both CAR-independent and CAR-dependent mechanisms. The use of CAR-based cell therapies has been successful in treating cancer patients, leading to further investigation of this innovative treatment for alternative diseases, including AD. The complementary roles of CAR T and CAR NK cells have stimulated exploration in this area. Our study examines the latest research on the therapeutic effectiveness of these cells in treating both cancer and ADs.

Modifying CAR-T cells with anti-checkpoints in cancer immunotherapy: A focus on anti PD-1/PD-L1 antibodies

Chimeric antigen receptor-modified T (CAR-T) are genetically engineered cells to express tumor-specific antigens revolutionizing the treatment of hematologic malignancies. The hostile tumor microenvironment (TME) remains a challenge for CAR-T cell therapy in solid tumors. As a solution, combinational therapy with immune checkpoint inhibitors (ICIs) is shown to improve the safety and efficacy of CAR-T cell therapy. To avoid side effects related to the application of ICIs in combinational therapy, engineering CARs to express tumor-specific antigens may help improvement of clinical outcomes. Those CARs expressing single chain variable fragments (scFvs) or nanobodies against immune checkpoint stimulatory or inhibitory molecules, such as the programmed death-1 (PD-1)/programmed death-ligand 1 (PD-L1) signaling axis are being extensively studied in various clinical trials. In this review, we discuss the significance of anti-PD-(L)1 scFv-expressing CAR-T cells in the treatment of human cancers, describing current challenges and potential strategies to overcome such predicaments in the area of cancer immunotherapy.

Immune modulation via T regulatory cell enhancement: Disease-modifying therapies for autoimmunity and their potential for chronic allergic and inflammatory diseases-An EAACI position paper of the Task Force on Immunopharmacology (TIPCO)

Therapeutic advances using targeted biologicals and small-molecule drugs have achieved significant success in the treatment of chronic allergic, autoimmune, and inflammatory diseases particularly for some patients with severe, treatment-resistant forms. This has been aided by improved identification of disease phenotypes. Despite these achievements, not all severe forms of chronic inflammatory and autoimmune diseases are successfully targeted, and current treatment options, besides allergen immunotherapy for selected allergic diseases, fail to change the disease course. T cell-based therapies aim to cure diseases through the selective induction of appropriate immune responses following the delivery of engineered, specific cytotoxic, or regulatory T cells (Tregs). Adoptive cell therapies (ACT) with genetically engineered T cells have revolutionized the oncology field, bringing curative treatment for leukemia and lymphoma, while therapies exploiting the suppressive functions of Tregs have been developed in nononcological settings, such as in transplantation and autoimmune diseases. ACT with Tregs are also being considered in nononcological settings such as cardiovascular disease, obesity, and chronic inflammatory disorders. After describing the general features of T cell-based approaches and current applications in autoimmune diseases, this position paper reviews the experimental models testing or supporting T cell-based approaches, especially Treg-based approaches, in severe IgE-mediated responses and chronic respiratory airway diseases, such as severe asthma and COPD. Along with an assessment of challenges and unmet needs facing the application of ACT in these settings, this article underscores the potential of ACT to offer curative options for patients with severe or treatment-resistant forms of these immune-driven disorders.

Treatment of Multiple Myeloma Using Chimeric Antigen Receptor T Cells with Dual Specificity

Chimeric antigen receptor (CAR) T-cell therapy has shown remarkable successes in fighting B-cell leukemias/lymphomas. Promising response rates are reported in patients treated with B-cell maturation antigen (BCMA) CAR T cells for multiple myeloma. However, responses appear to be nondurable, highlighting the need to expand the repertoire of multiple myeloma-specific targets for immunotherapy and to generate new CAR T cells. Here, we developed a "dual-CAR" targeting two multiple myeloma-associated antigens and explored its safety and efficacy. To reduce the "off-target" toxicity, we used the recognition of paired antigens that were coexpressed by the tumor to induce efficient CAR T-cell activation. The dual-CAR construct presented here was carefully designed to target the multiple myeloma-associated antigens, taking into consideration the distribution of both antigens on normal human tissues. Our results showed that the CD138/CD38-targeted dual CAR (dCAR138-38) elicited a potent anti-multiple myeloma response both in vitro and in vivo NSG mice transplanted with a multiple myeloma cell line and treated with dCAR138-38 showed median survival of 97 days compared with 31 days in the control group treated with mock-lymphocytes. The dCAR138-38 showed increased specificity toward cells expressing both targeted antigens compared with single-antigen-expressing cells and low activity toward primary cells from healthy tissues. Our findings indicated that the dCAR138-38 may provide a potent and safe alternative therapy for patients with multiple myeloma.

Efficacy and Safety of CD28- or 4-1BB-Based CD19 CAR-T Cells in B Cell Acute Lymphoblastic Leukemia

CD19-directed chimeric antigen receptor-T (CAR-T) cells with a 4-1BB or CD28 co-stimulatory domain have shown impressive antitumor activity against relapsed or refractory B cell acute lymphoblastic leukemia (r/r B-ALL). However, a parallel comparison of their performances in r/r B-ALL therapy has not been sufficiently reported. Here, we manufactured 4-1BB- and CD28-based CD19 CAR-T cells using the same process technology and evaluated their efficacy and safety in r/r B-ALL therapy based on pre-clinical and exploratory clinical investigations. In B-ALL-bearing mice, a similar antitumor effect and CAR-T kinetics in peripheral blood were observed at the CAR-T dose of 1 × 10⁷/mouse. However, when the dose was decreased to 1 × 10⁶/mouse, 4-1BB CAR-T cells were more potent in eradicating tumor cells and showed longer persistence than CD28 CAR-T cells. Retrospective analysis of an exploratory clinical study that used 4-1BB- or CD28-based CAR-T cells to treat r/r B-ALL was performed. Compared with CD28 CAR-T cells, 4-1BB CAR-T cells resulted in higher antitumor efficacy and less severe adverse events. This study demonstrated that the performance of 4-1BB CAR-T cells was superior to that of CD28 CAR-T cells in suppressing CD19⁺ B-ALL, at least under our manufacturing process.

A High-Throughput Method for Characterizing Novel Chimeric Antigen Receptors in Jurkat Cells

Chimeric antigen receptor (CAR) development involves extensive empirical characterization of antigen-binding domain (ABD)/CAR constructs for clinical suitability. Here, we present a cost-efficient and rapid method for evaluating CARs in human Jurkat T cells. Using a modular CAR plasmid, a highly efficient ABD cloning strategy, plasmid electroporation, short-term co-culture, and flow-cytometric detection of CD69, this assay (referred to as CAR-J) evaluates sensitivity and specificity for ABDs. Assessing 16 novel anti-CD22 single-chain variable fragments derived from mouse monoclonal antibodies, CAR-J stratified constructs by response magnitude to CD22-expressing target cells. We also characterized 5 novel anti-EGFRvIII CARs for preclinical development, identifying candidates with varying tonic and target-specific activation characteristics. When evaluated in primary human T cells, tonic/auto-activating (without target cells) EGFRvIII-CARs induced target-independent proliferation, differentiation toward an effector phenotype, elevated activity against EGFRvIII-negative cells, and progressive loss of target-specific response upon in vitro re-challenge. These EGFRvIII CAR-T cells also showed anti-tumor activity in xenografted mice. In summary, CAR-J represents a straightforward method for high-throughput assessment of CAR constructs as genuine cell-associated antigen receptors that is particularly useful for generating large specificity datasets as well as potential downstream CAR optimization.

Critical factors in chimeric antigen receptor-modified T-cell (CAR-T) therapy for solid tumors

The success of chimeric antigen receptor-modified T-cell (CAR-T) therapy for B-cell lymphocyte malignancies targeting CD19 places it in a rapidly growing field in cancer immunotherapy for both hematological and solid tumors. However, the two types of tumor are quite different in the following respects. Solid tumors are characterized by complex vasculatures and matrix barriers that significantly affect T-cell functions and migration. Moreover, various immunosuppressive molecules expressed in the tumor microenvironment can impede T-cell activation, and the high metabolic rate of tumors competitively suppresses the metabolism of immune cells. All these factors will exert their influences on the development of a cancer, which is a dynamic balance between the host's immune system and the tumor. At present, solid tumors are treated primarily by surgical resection combined with radiotherapy and chemotherapy, a treatment process that is painful and not always effective. With advantages over traditional treatments, the recently developed CAR-T immunotherapy has been applied and has shown highly promising results. Nevertheless, the complexity of solid tumors presents a great challenge to this technique. This review focuses on elucidating the factors influencing the anti-tumor effects of CAR-T in the specific tumor environment, and hence exploring feasible approaches to overcome them.

Strategies to Address Chimeric Antigen Receptor Tonic Signaling

Adoptive cell transfer using chimeric antigen receptors (CAR) has emerged as one of the most promising new therapeutic modalities for patients with relapsed or refractory B-cell malignancies. Thus far, results in patients with advanced solid tumors have proven disappointing. Constitutive tonic signaling in the absence of ligand is an increasingly recognized complication when deploying these synthetic fusion receptors and can be a cause of poor antitumor efficacy, impaired survival, and reduced persistence in vivo In parallel, ligand-dependent tonic signaling can mediate toxicity and promote T-cell anergy, exhaustion, and activation-induced cell death. Here, we review the mechanisms underpinning CAR tonic signaling and highlight the wide variety of effects that can emerge after making subtle structural changes or altering the methodology of CAR transduction. We highlight strategies to prevent unconstrained tonic signaling and address its deleterious consequences. We also frame this phenomenon in the context of endogenous TCR tonic signaling, which has been shown to regulate peripheral tolerance, facilitate the targeting of foreign antigens, and suggest opportunities to coopt ligand-dependent CAR tonic signaling to facilitate in vivo persistence and efficacy. Mol Cancer Ther; 17(9); 1795-815. ©2018 AACR.

The Use of the Humanized Mouse Model in Gene Therapy and Immunotherapy for HIV and Cancer

HIV and cancer remain prevailing sources of morbidity and mortality worldwide. There are current efforts to discover novel therapeutic strategies for the treatment or cure of these diseases. Humanized mouse models provide the investigative tool to study the interaction between HIV or cancer and the human immune system in vivo. These humanized models consist of immunodeficient mice transplanted with human cells, tissues, or hematopoietic stem cells that result in reconstitution with a nearly full human immune system. In this review, we discuss preclinical studies evaluating therapeutic approaches in stem cell-based gene therapy and T cell-based immunotherapies for HIV and cancer using a humanized mouse model and some recent advances in using checkpoint inhibitors to improve antiviral or antitumor responses.

Engineered Tolerance: Tailoring Development, Function, and Antigen-Specificity of Regulatory T Cells

Regulatory T cells (Tregs) are potent suppressors of immune responses and are currently being clinically tested for their potential to stop or control undesired immune responses in autoimmunity, hematopoietic stem cell transplantation, and solid organ transplantation. Current clinical approaches aim to boost Tregs in vivo either by using Treg-promoting small molecules/proteins and/or by adoptive transfer of expanded Tregs. However, the applicability of Treg-based immunotherapies continues to be hindered by technical limitations related to cell isolation and expansion of a pure, well-characterized, and targeted Treg product. Efforts to overcome these limitations and improve Treg-directed therapies are now under intense investigation in animal models and pre-clinical studies. Here, we review cell and protein engineering-based approaches that aim to target different aspects of Treg biology including modulation of IL-2 signaling or FOXP3 expression, and targeted antigen-specificity using transgenic T cell receptors or chimeric antigen receptors. With the world-wide interest in engineered T cell therapy, these exciting new approaches have the potential to be rapidly implemented and developed into therapies that can effectively fine-tune immune tolerance.