CD3ζ-based chimeric antigen receptors mediate T cell activation via cis- and trans-signalling mechanisms: implications for optimization of receptor structure for adoptive cell therapy

Tuning CAR T-cell therapies for efficacy and reduced toxicity

Chimeric antigen receptor (CAR) T-cell therapies are a standard of care for certain relapsed or refractory B-cell cancers. However, many patients do not respond to CAR T-cell therapy or relapse later, short- and long-term toxicities are common, and current CAR T-cell therapies have limited efficacy for solid cancers. The gene engineering inherent in CAR T-cell manufacture offers an unprecedented opportunity to control cellular characteristics and design products that may overcome these limitations. This review summarises available methods to "tune" CAR T-cells for optimal efficacy and safety. The components of a typical CAR, and the modifications that can influence CAR T-cell function are discussed. Methods of engineering passive, inducible or autonomous control mechanisms into CAR T-cells, allowing selective limitation or enhancement of CAR T-cell activity are reviewed. The impact of manufacturing processes on CAR T-cell function are considered, including methods of limiting CAR T-cell terminal differentiation and exhaustion, and the use of specific T-cell subsets as the CAR T starting material. We discuss the use of multicistronic transgenes and multiplexed gene editing. Finally, we highlight the need for innovative clinical trial designs if we are to make the most of the opportunities offered by CAR T-cell therapies.

Activation of Cell-Intrinsic Signaling in CAR-T Cells via a Chimeric IL7R Domain

Chimeric antigen receptor (CAR) T cells can effectively treat leukemias, but sustained antitumor responses can be hindered by a lack of CAR T-cell persistence. Cytotoxic effector T cells are short-lived, and establishment of CAR-T cells with memory to ensure immune surveillance is important. Memory T cells depend on cytokine support, with IL7 activation of the IL7 receptor (IL7R) being critical. However, IL7R surface expression is negatively regulated by exposure to IL7. We aimed to support CAR T-cell persistence by equipping CAR-T cells with a sustained IL7Rα signal. We engineered T cells to constitutively secrete IL7 or to express an anti-acute myeloid leukemia-targeted IL7Rα-chimeric cytokine receptor (CCR) and characterized the phenotype of these cell types. Canonical downstream signaling was activated in CCR-T cells with IL7R activation. When coexpressed with a cytotoxic CAR, functionality of both the CCR and CAR was maintained. We designed hybrid CAR-CCR and noted membrane proximity of the intracellular domains as vital for signaling. These data show cell-intrinsic cytokine support with canonical signaling, and functionality can be provided via expression of an IL7Rα domain whether independently expressed or incorporated into a cytotoxic CAR for use in anticancer therapy.

SIGNIFICANCE

To improve the phenotype of tumor-directed T-cell therapy, we show that provision of cell-intrinsic IL7R-mediated signaling is preferable to activation of cells with exogenous IL7. We engineer this signaling via independent receptor engineering and incorporation into a CAR and validate maintained antigen-specific cytotoxic activity.

CAR-T cell therapy: a game-changer in cancer treatment and beyond

In recent years, cancer has become one of the primary causes of mortality, approximately 10 million deaths worldwide each year. The most advanced, chimeric antigen receptor (CAR) T cell immunotherapy has turned out as a promising treatment for cancer. CAR-T cell therapy involves the genetic modification of T cells obtained from the patient's blood, and infusion back to the patients. CAR-T cell immunotherapy has led to a significant improvement in the remission rates of hematological cancers. CAR-T cell therapy presently limited to hematological cancers, there are ongoing efforts to develop additional CAR constructs such as bispecific CAR, tandem CAR, inhibitory CAR, combined antigens, CRISPR gene-editing, and nanoparticle delivery. With these advancements, CAR-T cell therapy holds promise concerning potential to improve upon traditional cancer treatments such as chemotherapy and radiation while reducing associated toxicities. This review covers recent advances and advantages of CAR-T cell immunotherapy.

Rationally designed approaches to augment CAR-T therapy for solid tumor treatment

Chimeric antigen receptor T cell denoted as CAR-T therapy has realized incredible therapeutic advancements for B cell malignancy treatment. However, its therapeutic validity has yet to be successfully achieved in solid tumors. Different from hematological cancers, solid tumors are characterized by dysregulated blood vessels, dense extracellular matrix, and filled with immunosuppressive signals, which together result in CAR-T cells' insufficient infiltration and rapid dysfunction. The insufficient recognition of tumor cells and tumor heterogeneity eventually causes cancer reoccurrences. In addition, CAR-T therapy also raises safety concerns, including potential cytokine release storm, on-target/off-tumor toxicities, and neuro-system side effects. Here we comprehensively review various targeting aspects, including CAR-T cell design, tumor modulation, and delivery strategy. We believe it is essential to rationally design a combinatory CAR-T therapy via constructing optimized CAR-T cells, directly manipulating tumor tissue microenvironments, and selecting the most suitable delivery strategy to achieve the optimal outcome in both safety and efficacy.

Endogenous Signaling Molecule Activating (ESMA) CARs: A Novel CAR Design Showing a Favorable Risk to Potency Ratio for the Treatment of Triple Negative Breast Cancer

As chimeric antigen receptor (CAR) T cell therapy continues to gain attention as a valuable treatment option against different cancers, strategies to improve its potency and decrease the side effects associated with this therapy have become increasingly relevant. Herein, we report an alternative CAR design that incorporates transmembrane domains with the ability to recruit endogenous signaling molecules, eliminating the need for stimulatory signals within the CAR structure. These endogenous signaling molecule activating (ESMA) CARs triggered robust cytotoxic activity and proliferation of the T cells when directed against the triple-negative breast cancer (TNBC) cell line MDA-MB-231 while exhibiting reduced cytokine secretion and exhaustion marker expression compared to their cognate standard second generation CARs. In a NOD SCID Gamma (NSG) MDA-MB-231 xenograft mouse model, the lead candidate maintained longitudinal therapeutic efficacy and an enhanced T cell memory phenotype. Profound tumor infiltration by activated T cells repressed tumor growth, further manifesting the proliferative capacity of the ESMA CAR T cell therapy. Consequently, ESMA CAR T cells entail promising features for improved clinical outcome as a solid tumor treatment option.

Refining chimeric antigen receptors via barcoded protein domain combination pooled screening

Chimeric antigen receptor (CAR)-T cells represent a promising frontier in cancer immunotherapy. However, the current process for developing new CAR constructs is time consuming and inefficient. To address this challenge and expedite the evaluation and comparison of full-length CAR designs, we have devised a novel cloning strategy. This strategy involves the sequential assembly of individual CAR domains using blunt ligation, with each domain being assigned a unique DNA barcode. Applying this method, we successfully generated 360 CAR constructs that specifically target clinically validated tumor antigens CD19 and GD2. By quantifying changes in barcode frequencies through next-generation sequencing, we characterize CARs that best mediate proliferation and expansion of transduced T cells. The screening revealed a crucial role for the hinge domain in CAR functionality, with CD8a and IgG4 hinges having opposite effects in the surface expression, cytokine production, and antitumor activity in CD19- versus GD2-based CARs. Importantly, we discovered two novel CD19-CAR architectures containing the IgG4 hinge domain that mediate superior in vivo antitumor activity compared with the construct used in Kymriah, a U.S. Food and Drug Administration (FDA)-approved therapy. This novel screening approach represents a major advance in CAR engineering, enabling accelerated development of cell-based cancer immunotherapies.

ICOS and OX40 tandem co-stimulation enhances CAR T-cell cytotoxicity and promotes T-cell persistence phenotype

Chimeric Antigen Receptor (CAR) T-cell therapies have emerged as an effective and potentially curative immunotherapy for patients with relapsed or refractory malignancies. Treatment with CD19 CAR T-cells has shown unprecedented results in hematological malignancies, including heavily refractory leukemia, lymphoma, and myeloma cases. Despite these encouraging results, CAR T-cell therapy faces limitations, including the lack of long-term responses in nearly 50-70% of the treated patients and low efficacy in solid tumors. Among other reasons, these restrictions are related to the lack of targetable tumor-associated antigens, limitations on the CAR design and interactions with the tumor microenvironment (TME), as well as short-term CAR T-cell persistence. Because of these reasons, we developed and tested a chimeric antigen receptor (CAR) construct with an anti-ROR1 single-chain variable-fragment cassette connected to CD3ζ by second and third-generation intracellular signaling domains including 4-1BB, CD28/4-1BB, ICOS/4-1BB or ICOS/OX40. We observed that after several successive tumor-cell in vitro challenges, ROR1.ICOS.OX40ζ continued to proliferate, produce pro-inflammatory cytokines, and induce cytotoxicity against ROR1+ cell lines in vitro with enhanced potency. Additionally, in vivo ROR1.ICOS.OX40ζ T-cells showed anti-lymphoma activity, a long-lasting central memory phenotype, improved overall survival, and evidence of long-term CAR T-cell persistence. We conclude that anti-ROR1 CAR T-cells that are activated by ICOS.OX40 tandem co-stimulation show in vitro and in vivo enhanced targeted cytotoxicity associated with a phenotype that promotes T-cell persistence.

Clinical applications of gene therapy for rare diseases: A review

Rare diseases collectively exact a high toll on society due to their sheer number and overall prevalence. Their heterogeneity, diversity, and nature pose daunting clinical challenges for both management and treatment. In this review, we discuss recent advances in clinical applications of gene therapy for rare diseases, focusing on a variety of viral and non-viral strategies. The use of adeno-associated virus (AAV) vectors is discussed in the context of Luxturna, licenced for the treatment of RPE65 deficiency in the retinal epithelium. Imlygic, a herpes virus vector licenced for the treatment of refractory metastatic melanoma, will be an example of oncolytic vectors developed against rare cancers. Yescarta and Kymriah will showcase the use of retrovirus and lentivirus vectors in the autologous ex vivo production of chimeric antigen receptor T cells (CAR-T), licenced for the treatment of refractory leukaemias and lymphomas. Similar retroviral and lentiviral technology can be applied to autologous haematopoietic stem cells, exemplified by Strimvelis and Zynteglo, licenced treatments for adenosine deaminase-severe combined immunodeficiency (ADA-SCID) and β-thalassaemia respectively. Antisense oligonucleotide technologies will be highlighted through Onpattro and Tegsedi, RNA interference drugs licenced for familial transthyretin (TTR) amyloidosis, and Spinraza, a splice-switching treatment for spinal muscular atrophy (SMA). An initial comparison of the effectiveness of AAV and oligonucleotide therapies in SMA is possible with Zolgensma, an AAV serotype 9 vector, and Spinraza. Through these examples of marketed gene therapies and gene cell therapies, we will discuss the expanding applications of such novel technologies to previously intractable rare diseases.

Leveraging CD16 fusion receptors to remodel the immune response for enhancing anti-tumor immunotherapy in iPSC-derived NK cells

BACKGROUND

The cytotoxicity of NK cells is largely dependent on IgG Fc receptor CD16a, which mediates antibody-dependent cell-mediated cytotoxicity (ADCC). The high-affinity and non-cleavable CD16 (hnCD16) is developed and demonstrated a multi-tumor killing potential. However, the hnCD16 receptor activates a single CD16 signal and provides limited tumor suppression. How to exploit the properties of hnCD16 and incorporate NK cell-specific activation domains is a promising development direction to further improve the anti-tumor activity of NK cells.

METHODS

To expand the applications of hnCD16-mediated ADCC for NK cell-based immunotherapy in cancer, we designed the hnCD16 Fusion Receptor (FR) constructs with the ectodomain of hnCD16 fused with NK cell-specific activating domains in the cytoplasm. FR constructs were transduced into CD16-negative NK cell line and human iPSC-derived NK (iNK) cells and effective FR constructs were screened. The up-regulation of immune activation- and cytokine-releasing-related pathways in FR-transduced NK cells was screened and validated by RNA sequencing and multiplex cytokines release assay, respectively. The tumor-killing efficiency was tested in vitro and in vivo via co-culture with tumor cell lines and xenograft mice-bearing human B-cell lymphoma, respectively.

RESULTS

We screened the most effective combination to kill B cell lymphoma, which was fused with the ectodomain of hnCD16a, NK-specific co-stimulators (2B4 and DAP10) and CD3ζ in cytoplasmic domains. The screened construct showed excellent cytotoxicity effects and sharp multiple cytokines releasing both in the NK cell line and iNK cells. The transcriptomic analysis and validation assays of hnCD16- and hnCD16FR-transduced NK cells showed that hnCD16FR transduction remodeled immune-related transcriptome in NK cells, where significant upregulation of genes related to cytotoxicity, high cytokines releasing, induced tumor cell apoptosis, and ADCC in comparison with hnCD16 transduction were highlighted. In vivo xenograft studies demonstrated that a single low-dose regimen of engineered hnCD16FR iPSC-derived NK cells co-administered with anti-CD20 mAb treatment mediated potent activity and significantly improved survival.

CONCLUSION

We developed a novel hnCD16FR construct that exhibits more potent cytotoxicity than reported hnCD16, which is a promising approach to treat malignancies with improved ADCC properties. We also offer a rationale for NK activation domains that remodel immune response to enhance CD16 signaling in NK cells.

Specific Activation of T Cells by an ACE2-Based CAR-Like Receptor upon Recognition of SARS-CoV-2 Spike Protein

Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) is the causative agent of the Coronavirus Disease 2019 (COVID-19) pandemic, which is still a health issue worldwide mostly due to a high rate of contagiousness conferred by the high-affinity binding between cell viral receptors, Angiotensin-Converting Enzyme 2 (ACE2) and SARS-CoV-2 Spike protein. Therapies have been developed that rely on the use of antibodies or the induction of their production (vaccination), but despite vaccination being still largely protective, the efficacy of antibody-based therapies wanes with the advent of new viral variants. Chimeric Antigen Receptor (CAR) therapy has shown promise for tumors and has also been proposed for COVID-19 treatment, but as recognition of CARs still relies on antibody-derived sequences, they will still be hampered by the high evasion capacity of the virus. In this manuscript, we show the results from CAR-like constructs with a recognition domain based on the ACE2 viral receptor, whose ability to bind the virus will not wane, as Spike/ACE2 interaction is pivotal for viral entry. Moreover, we have developed a CAR construct based on an affinity-optimized ACE2 and showed that both wild-type and affinity-optimized ACE2 CARs drive activation of a T cell line in response to SARS-CoV-2 Spike protein expressed on a pulmonary cell line. Our work sets the stage for the development of CAR-like constructs against infectious agents that would not be affected by viral escape mutations and could be developed as soon as the receptor is identified.

Sema4D silencing increases the sensitivity of nivolumab to B16-F10 resistant melanoma via inhibiting the PI3K/AKT signaling pathway

Melanoma is a common skin tumor that causes a high rate of mortality, especially in Europe, North America and Oceania. Immunosuppressants such as anti-PD-1 have been used in the treatment of malignant melanoma, however, nearly 60% of patients do not respond to these treatments. Sema4D, also called CD100, is expressed in T cells and tumor tissues. Sema4D and its receptor, Plexin-B1, play crucial roles in the process of immune regulation, angiogenesis, and tumor progression. The role of Sema4D in melanoma with anti-PD-1 resistance is poorly understood. Through a combination of molecular biology techniques and in silico analysis, the role of Sema4D in improving anti-PD-L1 sensitivity in melanoma was explored. The results showed that the expression of Sema4D, Plexin-B1 and PD-L1 was significantly increased in B16-F10R cells. Sema4D knockdown synergizes with anti-PD-1 treatment, cell viability, cell invasion and migration were significantly decreased, while the apoptosis was increased, the growth of tumors on the mice was also inhibited. Mechanistically, bioinformatics analysis revealed that Sema4D is involved in the PI3K/AKT signaling pathway; the downregulation of p-PI3K/PI3K and p-AKT/AKT expression were observed in Sema4D knockdown, therefore, nivolumab resistance is related to Sema4D and Sema4D silencing can improve sensitivity to nivolumab via inhibition of the PI3K/AKT signaling pathway.

The signaling and the metabolic differences of various CAR T cell designs

Chimeric antigen receptor (CAR) T cell therapy is introduced as an effective, rapidly evolving therapeutic to treat cancer, especially cancers derived from hematological cells, such as B cells. CAR T cell gene constructs combine a tumor-targeting device coupled to the T cell receptor (TCR) zeta chain domain with different signaling domains such as domains derived from CD28 or 4-1BB (CD137). The incorporation of each specific co-stimulatory domain targets the immunometabolic pathways of CAR T cells as well as other signaling pathways. Defining the immunometabolic and signaling pathways by which CAR T cells become and remain active, survive, and eliminate their targets may represent a huge step forward in this relatively young research field as the CAR gene can be tailored to gain optimal function also for solid tumors with elaborate immunosuppression and protective stroma. There is a close relationship between different signaling domains applied in CAR T cells, and difficult to evaluate the benefit from different tested CAR gene constructs. In this review, we attempt to collect the latest findings regarding the CAR T cell signaling pathways that affect immunometabolic pathways.

Natural killer cells in antitumour adoptive cell immunotherapy

Natural killer (NK) cells comprise a unique population of innate lymphoid cells endowed with intrinsic abilities to identify and eliminate virally infected cells and tumour cells. Possessing multiple cytotoxicity mechanisms and the ability to modulate the immune response through cytokine production, NK cells play a pivotal role in anticancer immunity. This role was elucidated nearly two decades ago, when NK cells, used as immunotherapeutic agents, showed safety and efficacy in the treatment of patients with advanced-stage leukaemia. In recent years, following the paradigm-shifting successes of chimeric antigen receptor (CAR)-engineered adoptive T cell therapy and the advancement in technologies that can turn cells into powerful antitumour weapons, the interest in NK cells as a candidate for immunotherapy has grown exponentially. Strategies for the development of NK cell-based therapies focus on enhancing NK cell potency and persistence through co-stimulatory signalling, checkpoint inhibition and cytokine armouring, and aim to redirect NK cell specificity to the tumour through expression of CAR or the use of engager molecules. In the clinic, the first generation of NK cell therapies have delivered promising results, showing encouraging efficacy and remarkable safety, thus driving great enthusiasm for continued innovation. In this Review, we describe the various approaches to augment NK cell cytotoxicity and longevity, evaluate challenges and opportunities, and reflect on how lessons learned from the clinic will guide the design of next-generation NK cell products that will address the unique complexities of each cancer.

CAR-T cell potency: from structural elements to vector backbone components

Chimeric antigen receptor (CAR) T cell therapy, in which a patient’s own T lymphocytes are engineered to recognize and kill cancer cells, has achieved remarkable success in some hematological malignancies in preclinical and clinical trials, resulting in six FDA-approved CAR-T products currently available in the market. Once equipped with a CAR construct, T cells act as living drugs and recognize and eliminate the target tumor cells in an MHC-independent manner. In this review, we first described all structural modular of CAR in detail, focusing on more recent findings. We then pointed out behind-the-scene elements contributing to CAR expression and reviewed how CAR expression can be drastically affected by the elements embedded in the viral vector backbone.

CAR T-Cell-Based gene therapy for cancers: new perspectives, challenges, and clinical developments

Chimeric antigen receptor (CAR)-T cell therapy is a progressive new pillar in immune cell therapy for cancer. It has yielded remarkable clinical responses in patients with B-cell leukemia or lymphoma. Unfortunately, many challenges remain to be addressed to overcome its ineffectiveness in the treatment of other hematological and solidtumor malignancies. The major hurdles of CAR T-cell therapy are the associated severe life-threatening toxicities such as cytokine release syndrome and limited anti-tumor efficacy. In this review, we briefly discuss cancer immunotherapy and the genetic engineering of T cells and, In detail, the current innovations in CAR T-cell strategies to improve efficacy in treating solid tumors and hematologic malignancies. Furthermore, we also discuss the current challenges in CAR T-cell therapy and new CAR T-cell-derived nanovesicle therapy. Finally, strategies to overcome the current clinical challenges associated with CAR T-cell therapy are included as well.

De novo-designed transmembrane domains tune engineered receptor functions

De novo-designed receptor transmembrane domains (TMDs) present opportunities for precise control of cellular receptor functions. We developed a de novo design strategy for generating programmed membrane proteins (proMPs): single-pass α-helical TMDs that self-assemble through computationally defined and crystallographically validated interfaces. We used these proMPs to program specific oligomeric interactions into a chimeric antigen receptor (CAR) that we expressed in mouse primary T cells and found that both in vitro CAR T cell cytokine release and in vivo antitumor activity scaled linearly with the oligomeric state encoded by the receptor TMD, from monomers up to tetramers. All programmed CARs stimulated substantially lower T cell cytokine release relative to the commonly used CD28 TMD, which we show elevated cytokine release through lateral recruitment of the endogenous T cell costimulatory receptor CD28. Precise design using orthogonal and modular TMDs thus provides a new way to program receptor structure and predictably tune activity for basic or applied synthetic biology.

T-cell Receptor Is a Threshold Detector: Sub- and Supra-Threshold Stochastic Resonance in TCR-MHC Clusters on the Cell Surface

Stochastic resonance in clusters of major histocompatibility molecules is extended by a more detailed description of adaptive thresholding and by applying the notion of suprathreshold stochastic resonance as a stochastically quantizing encoder of transmembrane signaling downstream of major histocompatibility molecules and T-cell receptors on the side of presenting and recognizing cells, respectively. The adaptive nature of thresholding is partly explained by a mirroring of the noncognate–cognate dichotomy shown by the T-cell receptor structure and the kinetic-segregation model of the onset of T-cell receptor triggering. Membrane clusters of major histocompatibility molecules and T-cell receptors on their host cells are envisioned as places of the temporal encoding of downstream signals via the suprathreshold stochastic resonance process. The ways of optimization of molecular prostheses, such as chimeric antigen receptors against cancer in transmembrane signaling, are suggested in the framework of suprathreshold stochastic resonance. The analogy between Förster resonance energy transfer and suprathreshold stochastic resonance for information transfer is also discussed. The overlap integral for energy transfer parallels the mutual information transferred by suprathreshold stochastic resonance.

Protein engineering: a driving force toward synthetic immunology

The full application of the diverse toolkit of protein engineering has made it easier to control the immune system. In particular, synthetic cytokine variants and engineered immune receptor platforms have shown promise for the treatment of various indications with dysregulated immune function, particularly cancer. Here, we review recent advances in the control of immune cell signaling and therapeutic potency that have employed protein engineering strategies. We further discuss how safety concerns are driving the design of immunotherapeutics toward 'user-defined' control or requiring multiple distinct inputs before a functional response, highlighting emergent control strategies employed for chimeric antigen receptor (CAR) engineering.

From antibodies to living drugs: Quo vadis cancer immunotherapy?

In the last few decades, monoclonal antibodies targeting various receptors and ligands have shown significant advance in cancer therapy. However, still a great percentage of patients experiences tumor relapse despite persistent antigen expression. Immune cell therapy with adoptively transferred modified T cells that express chimeric antigen receptors (CAR) is an engaging option to improve disease outcome. Designer T cells have been applied with remarkable success in the treatment for acute B cell leukemias, yielding unprecedented antitumor activity and significantly improved overall survival. Relying on the success of CAR T cells in leukemias, solid tumors are now emerging potential targets; however, their complexity represents a significant challenge. In preclinical models, CAR T cells recognized and efficiently killed the wide spectrum of tumor xenografts; however, in human clinical trials, limited antitumor efficacy and serious side effects, including cytokine release syndrome, have emerged as potential limitations. The next decade will be an exciting time to further optimize this novel cellular therapeutics to improve effector functions and, at the same time, keep adverse events in check. Moreover, we need to establish whether gene-modified T cells which are yet exclusively used for cancer patients could also be successful in the treatment for other diseases. Here, we provide a concise overview about the transition from monoclonal antibodies to the generation of chimeric antigen receptor T cells. We summarize lessons learned from preclinical models, including our own HER2-positive tumor models, as well as from clinical trials worldwide. We also discuss the challenges we are facing today and outline future prospects.

A Deep Insight Into CAR-T Cell Therapy in Non-Hodgkin Lymphoma: Application, Opportunities, and Future Directions

Non-Hodgkin's lymphoma (NHL) is a cancer that starts in the lymphatic system. In NHL, the important part of the immune system, a type of white blood cells called lymphocytes become cancerous. NHL subtypes include marginal zone lymphoma, small lymphocytic lymphoma, follicular lymphoma (FL), and lymphoplasmacytic lymphoma. The disease can emerge in either aggressive or indolent form. 5-year survival duration after diagnosis is poor among patients with aggressive/relapsing form of NHL. Therefore, it is necessary to understand the molecular mechanisms of pathogenesis involved in NHL establishment and progression. In the next step, we can develop innovative therapies for NHL based on our knowledge in signaling pathways, surface antigens, and tumor milieu of NHL. In the recent few decades, several treatment solutions of NHL mainly based on targeted/directed therapies have been evaluated. These approaches include B-cell receptor (BCR) signaling inhibitors, immunomodulatory agents, monoclonal antibodies (mAbs), epigenetic modulators, Bcl-2 inhibitors, checkpoint inhibitors, and T-cell therapy. In recent years, methods based on T cell immunotherapy have been considered as a novel promising anti-cancer strategy in the treatment of various types of cancers, and particularly in blood cancers. These methods could significantly increase the capacity of the immune system to induce durable anti-cancer responses in patients with chemotherapy-resistant lymphoma. One of the promising therapy methods involved in the triumph of immunotherapy is the chimeric antigen receptor (CAR) T cells with dramatically improved killing activity against tumor cells. The CAR-T cell-based anti-cancer therapy targeting a pan-B-cell marker, CD19 is recently approved by the US Food and Drug Administration (FDA) for the treatment of chemotherapy-resistant B-cell NHL. In this review, we will discuss the structure, molecular mechanisms, results of clinical trials, and the toxicity of CAR-T cell-based therapies. Also, we will criticize the clinical aspects, the treatment considerations, and the challenges and possible drawbacks of the application of CAR-T cells in the treatment of NHL.

Naturally Occurring Genetic Alterations in Proximal TCR Signaling and Implications for Cancer Immunotherapy

T cell-based immunotherapies including genetically engineered T cells, adoptive transfer of tumor-infiltrating lymphocytes, and immune checkpoint blockade highlight the impressive anti-tumor effects of T cells. These successes have provided new hope to many cancer patients with otherwise poor prognoses. However, only a fraction of patients demonstrates durable responses to these forms of therapies and many develop significant immune-mediated toxicity. These heterogeneous clinical responses suggest that underlying nuances in T cell genetics, phenotypes, and activation states likely modulate the therapeutic impact of these approaches. To better characterize known genetic variations that may impact T cell function, we 1) review the function of early T cell receptor-specific signaling mediators, 2) offer a synopsis of known mutations and genetic alterations within the associated molecules, 3) discuss the link between these mutations and human disease and 4) review therapeutic strategies under development or in clinical testing that target each of these molecules for enhancing anti-tumor T cell activity. Finally, we discuss novel engineering approaches that could be designed based on our understanding of the function of these molecules in health and disease.

Cancer Immunology and CAR-T Cells: A Turning Point Therapeutic Approach in Colorectal Carcinoma with Clinical Insight

Cancer immunotherapy endeavours in harnessing the delicate strength and specificity of the immune system for therapy of different malignancies, including colorectal carcinoma. The recent challenge for cancer immunotherapy is to practice and develop molecular immunology tools to create tactics that efficiently and securely boost antitumor reactions. After several attempts of deceptive outcomes, the wave has lastly altered and immunotherapy has become a clinically confirmed treatment for several cancers. Immunotherapeutic methods include the administration of antibodies or modified proteins that either block cellular activity or co-stimulate cells through immune control pathways, cancer vaccines, oncolytic bacteria, ex vivo activated adoptive transfer of T cells and natural killer cells. Engineered T cells are used to produce a chimeric antigen receptor (CAR) to treat different malignancies, including colorectal carcinoma in a recent decade. Despite the considerable early clinical success, CAR-T therapies are associated with some side effects and sometimes display minimal efficacy. It gives special emphasis on the latest clinical evidence with CAR-T technology and also other related immunotherapeutic methods with promising performance, and highlighted how this therapy can affect the therapeutic outcome and next upsurge as a key clinical aspect of colorectal carcinoma. In this review, we recapitulate the current developments produced to improve the efficacy and specificity of CAR-T therapies in colon cancer.

Mesenchymal stem cell therapies for COVID-19: Current status and mechanism of action

The outbreak of COVID-19 in December 2019, has become an urgent and serious public health emergency. At present, there is no effective treatment or vaccine for COVID-19. Therefore, there is a crucial unmet need to develop a safe and effective treatment for COVID-19 patients. Mesenchymal stem cells (MSCs) are widely used in basic science and in a variety of clinical trials. MSCs are able to engraft to the damaged tissues after transplantation and promote tissue regeneration, besides MSCs able to secrete immunomodulatory factors that suppress the cytokine storms. Moreover, the contribution of MSCs to prevent cell death and inhibit tissue fibrosis is well established. In the current review article, the potential mechanisms by which MSCs contribute to the treatment of COVID-19 patients are highlighted. Also, current trials that evaluated the potential of MSC-based treatments for COVID-19 are briefly reviewed.

Current Immunotherapy Approaches in Non-Hodgkin Lymphomas

Non-Hodgkin lymphomas (NHLs) are lymphoid malignancies of B- or T-cell origin. Despite great advances in treatment options and significant improvement of survival parameters, a large part of NHL patients either present with a chemotherapy-refractory disease or experience lymphoma relapse. Chemotherapy-based salvage therapy of relapsed/refractory NHL is, however, capable of re-inducing long-term remissions only in a minority of patients. Immunotherapy-based approaches, including bispecific antibodies, immune checkpoint inhibitors and genetically engineered T-cells carrying chimeric antigen receptors, single-agent or in combination with therapeutic monoclonal antibodies, immunomodulatory agents, chemotherapy or targeted agents demonstrated unprecedented clinical activity in heavily-pretreated patients with NHL, including chemotherapy-refractory cases with complex karyotype changes and other adverse prognostic factors. In this review, we recapitulate currently used immunotherapy modalities in NHL and discuss future perspectives of combinatorial immunotherapy strategies, including patient-tailored approaches.

To Remember or to Forget: The Role of Good and Bad Memories in Adoptive T Cell Therapy for Tumors

The generation of immunological memory is a hallmark of adaptive immunity by which the immune system "remembers" a previous encounter with an antigen expressed by pathogens, tumors, or normal tissues; and, upon secondary encounters, mounts faster and more effective recall responses. The establishment of T cell memory is influenced by both cell-intrinsic and cell-extrinsic factors, including genetic, epigenetic and environmental triggers. Our current knowledge of the mechanisms involved in memory T cell differentiation has instructed new opportunities to engineer T cells with enhanced anti-tumor activity. The development of adoptive T cell therapy has emerged as a powerful approach to cure a subset of patients with advanced cancers. Efficacy of this approach often requires long-term persistence of transferred T cell products, which can vary according to their origin and manufacturing conditions. Host preconditioning and post-transfer supporting strategies have shown to promote their engraftment and survival by limiting the competition with a hostile tumor microenvironment and between pre-existing immune cell subsets. Although in the general view pre-existing memory can confer a selective advantage to adoptive T cell therapy, here we propose that also "bad memories"-in the form of antigen-experienced T cell subsets-co-evolve with consequences on newly transferred lymphocytes. In this review, we will first provide an overview of selected features of memory T cell subsets and, then, discuss their putative implications for adoptive T cell therapy.

CAR-T design: Elements and their synergistic function

Chimeric antigen receptor (CAR) T cells use re-engineered cell surface receptors to specifically bind to and lyse oncogenic cells. Two clinically approved CAR-T–cell therapies have significant clinical efficacy in treating CD19-positive B cell cancers. With widespread interest to deploy this immunotherapy to other cancers, there has been great research activity to design new CAR structures to increase the range of targeted cancers and anti-tumor efficacy. However, several obstacles must be addressed before CAR-T–cell therapies can be more widely deployed. These include limiting the frequency of lethal cytokine storms, enhancing T-cell persistence and signaling, and improving target antigen specificity. We provide a comprehensive review of recent research on CAR design and systematically evaluate design aspects of the four major modules of CAR structure: the ligand-binding, spacer, transmembrane, and cytoplasmic domains, elucidating design strategies and principles to guide future immunotherapeutic discovery.

Engineering Cytoplasmic Signaling of CD28ζ CARs for Improved Therapeutic Functions

Chimeric antigen receptor modified T cells (CAR-T) have yielded impressive clinical outcomes in treating hematopoietic malignancies. However, relapses have occurred in a substantial number of patients and limited the development of CAR-T therapy. Most underlying reasons for these relapses can be attributed to poor persistence and rapid exhaustion of CAR-T cells in vivo. Despite multiple strategies having been developed, how to improve CAR-T persistence or resist exhaustion while maintaining sufficient cytotoxic functions is still a great challenge. Here we discuss engineering cytoplasmic signaling as an important strategy for CAR optimization. This review summarizes recent advances showing that the anti-tumor function of CAR-T cells can be improved by optimizing the CD3ζ domain or downstream signaling of CD28ζ CAR.

Chimeric antigen receptor signaling: Functional consequences and design implications

Chimeric antigen receptor (CAR) T cell therapy has transformed the care of refractory B cell malignancies and holds tremendous promise for many aggressive tumors. Despite overwhelming scientific, clinical, and public interest in this rapidly expanding field, fundamental inquiries into CAR T cell mechanistic functioning are still in their infancy. Because CAR T cells are manufactured from donor T lymphocytes, and because CARs incorporate well-characterized T cell signaling components, it has largely been assumed that CARs signal analogously to canonical T cell receptors (TCRs). However, recent studies demonstrate that many aspects of CAR signaling are unique, distinct from endogenous TCR signaling, and potentially even distinct among various CAR constructs. Thus, rigorous and comprehensive proteomic investigations are required for rational engineering of improved CARs. Here, we review what is known about proximal CAR signaling in T cells, compare it to conventional TCR signaling, and outline unmet challenges to improving CAR T cell therapy.

Recent Advances in Allogeneic CAR-T Cells

In recent decades, great advances have been made in the field of tumor treatment. Especially, cell-based therapy targeting tumor associated antigen (TAA) has developed tremendously. T cells were engineered to have the ability to attack tumor cells by generating CAR constructs consisting of genes encoding scFv, a co-stimulatory domain (CD28 or TNFRSF9), and CD247 signaling domains for T cell proliferation and activation. Principally, CAR-T cells are activated by recognizing TAA by scFv on the T cell surface, and then signaling domains inside cells connected by scFv are subsequently activated to induce downstream signaling pathways involving T cell proliferation, activation, and production of cytokines. Many efforts have been made to increase the efficacy and persistence and also to decrease T cell exhaustion. Overall, allogeneic and universal CAR-T generation has attracted much attention because of their wide and prompt usage for patients. In this review, we summarized the current techniques for generation of allogeneic and universal CAR-T cells along with their disadvantages and limitations that still need to be overcome.

T Cell Reprogramming Against Cancer

Advances in academic and clinical studies during the last several years have resulted in practical outcomes in adoptive immune therapy of cancer. Immune cells can be programmed with molecular modules that increase their therapeutic potency and specificity. It has become obvious that successful immunotherapy must take into account the full complexity of the immune system and, when possible, include the use of multifactor cell reprogramming that allows fast adjustment during the treatment. Today, practically all immune cells can be stably or transiently reprogrammed against cancer. Here, we review works related to T cell reprogramming, as the most developed field in immunotherapy. We discuss factors that determine the specific roles of αβ and γδ T cells in the immune system and the structure and function of T cell receptors in relation to other structures involved in T cell target recognition and immune response. We also discuss the aspects of T cell engineering, specifically the construction of synthetic T cell receptors (synTCRs) and chimeric antigen receptors (CARs) and the use of engineered T cells in integrative multifactor therapy of cancer.

The Role of Checkpoint Inhibitors and Cytokines in Adoptive Cell-Based Cancer Immunotherapy with Genetically Modified T Cells

This review focuses on the structure and molecular action mechanisms of chimeric antigen receptors (CARs) and major aspects of the manufacturing and clinical application of products for the CAR-T (CAR-modified T lymphocyte) therapy of hematological and solid tumors with special emphasis on the strategies for combined use of CAR-T therapy with immuno-oncological monoclonal antibodies (checkpoint inhibitors) and cytokines to boost survival, persistence, and antitumor efficacy of CAR-T therapy. The review also summarizes preclinical and clinical data on the additive effects of the combined use of CAR-T therapy with interleukins and monoclonal antibodies targeting immune checkpoints.

Beta-2 microglobulin knockout K562 cell-based artificial antigen presenting cells for ex vivo expansion of T lymphocytes

Aim: The human K562 leukemia cell line as a scaffold of artificial antigen presenting cells (aAPCs) for ex vivo lymphocyte expansion does not usually express major histocompatibility complex (MHC) molecules. However, when stimulated by supernatants from human T lymphocyte cultures, K562 cells upregulate β-2 microglobulin (B2M) and MHC class I expression, which would induce allo-specific T cells. Methods: We disrupted the B2M locus in K562 cells by CRISPR/Cas9 and achieved MHC class I-negative K562 cells. Results: We further generated K562-based MHC class I-negative aAPC line by zinc-finger nuclease mediated insertion of costimulatory molecules into the AAVS1 locus. This aAPC line could attenuate allogeneic immune responses but support robust antigen-independent and CD19 antigen-specific chimeric antigen receptor-T cell expansion in vitro. Conclusion: B2M-knockout K562 cells provide a new scaffold for aAPC construction and broader application in adoptive immunotherapies.

Chimeric antigen receptor-engineered regulatory T lymphocytes: promise for immunotherapy of autoimmune disease

Regulatory T lymphocytes (Tregs) exist as natural ideal immunosuppressors in the immune system. Autologous or allogeneic Treg transfusion therapy has been carried out in animal models and humans as a new strategy for treating autoimmune disease. Recent studies have shown that Tregs can be engineered with chimeric antigen receptors to be antigen-specific, which are more effective than polyclonal Tregs with fewer target limitations and a lack of major histocompatibility complex restriction. This review describes the potential for applying chimeric antigen receptor-engineered regulatory T cells in autoimmune diseases.

Emerging Cellular Therapies for Cancer

Genetically engineered T cells are powerful new medicines, offering hope for curative responses in patients with cancer. Chimeric antigen receptor (CAR) T cells were recently approved by the US Food and Drug Administration and are poised to enter the practice of medicine for leukemia and lymphoma, demonstrating that engineered immune cells can serve as a powerful new class of cancer therapeutics. The emergence of synthetic biology approaches for cellular engineering provides a broadly expanded set of tools for programming immune cells for enhanced function. Advances in T cell engineering, genetic editing, the selection of optimal lymphocytes, and cell manufacturing have the potential to broaden T cell-based therapies and foster new applications beyond oncology, in infectious diseases, organ transplantation, and autoimmunity.

An immunoproteomic approach to characterize the CAR interactome and signalosome

Adoptive transfer of T cells that express a chimeric antigen receptor (CAR) is an approved immunotherapy that may be curative for some hematological cancers. To better understand the therapeutic mechanism of action, we systematically analyzed CAR signaling in human primary T cells by mass spectrometry. When we compared the interactomes and the signaling pathways activated by distinct CAR-T cells that shared the same antigen-binding domain but differed in their intracellular domains and their in vivo antitumor efficacy, we found that only second-generation CARs induced the expression of a constitutively phosphorylated form of CD3ζ that resembled the endogenous species. This phenomenon was independent of the choice of costimulatory domains, or the hinge/transmembrane region. Rather, it was dependent on the size of the intracellular domains. Moreover, the second-generation design was also associated with stronger phosphorylation of downstream secondary messengers, as evidenced by global phosphoproteome analysis. These results suggest that second-generation CARs can activate additional sources of CD3ζ signaling, and this may contribute to more intense signaling and superior antitumor efficacy that they display compared to third-generation CARs. Moreover, our results provide a deeper understanding of how CARs interact physically and/or functionally with endogenous T cell molecules, which will inform the development of novel optimized immune receptors.

A retrospective comparison of allogenic and autologous chimeric antigen receptor T cell therapy targeting CD19 in patients with relapsed/refractory acute lymphoblastic leukemia

The source of CAR T cells can be autologous (autoCAR) or allogeneic (alloCAR). The latter is seen in patients with a history of allogeneic hematopoietic stem cell transplantation, and can be either donor-derived (DD-alloCAR) or recipient-derived (RD-alloCAR). While autoCAR is activated by CAR only, alloCAR receives activation signals from both T-cell receptor (TCR) and CAR. As a result, the biological differences could impact clinical outcomes. We retrospectively reviewed 31 patients: 17 received autoCAR, 11 received RD-alloCAR, and 3 received DD-alloCAR. After a median follow-up of 9 months, CR rate was 88.2% (95% CI 63.6-98.5%) in autoCAR and 100% (95% CI 71.5-100%) in RD-alloCAR. The median peak expansion in the autoCAR was significantly higher than the RD-alloCAR group (p = 0.007). RD-alloCAR group had significantly less patients with severe CRS (Grade ≥ 3) than the autoCAR group (p = 0.049). Acute graft-versus-host disease (GVHD) occurred in 2 (18.2%) of RD-alloCAR patients and 1 (33.3%) of DD-alloCAR patients. Univariate subgroup analysis of alloCAR group showed the presence of cGVHD at the time of T-cell collection was significantly associated with less than 6-month relapses (p = 0.022). RD-alloCAR patients with or without cGVHD at PBMC collection did not differ regarding the peak CAR T-cell expansion, CRS grades and OS.

Current development of chimeric antigen receptor T-cell therapy

Chimeric antigen receptor (CAR) T-cell therapy has achieved great success in recent years, with encouraging complete remission rate and long-term durability of response, especially in advanced B-cell malignancies. With the approval of tisagenlecleucel and axi-cel by FDA to treat refractory/relapsed acute lymphoblastic leukemia and non-Hodgkin lymphoma, our understanding of CAR T cells has been progressing rapidly. In this review, we discussed the designs of CAR T cells, factors affecting response, adverse effects, as well as application beyond B-cell malignancies.

Chimeric Antigen Receptor-Engineered T Cell Therapy in Acute Myeloid Leukaemia

Acute myeloid leukaemia (AML) is a disease with a very poor outcome and remains an area of significant unmet need, necessitating novel therapeutic strategies. The progress made in the field of immunotherapy, in particular chimeric antigen receptor (CAR)-engineered T cells, has given rise to many hopes for pathologies such as B cell acute lymphoblastic leukaemia and B cell lymphoma, and many studies have attempted to translate these successes to AML. This review summarises the recent advances in, and defines an ideal target for, CAR T cell therapy in AML.

CART cells are prone to Fas- and DR5-mediated cell death

Adoptive transfer of T cells transduced with Chimeric Antigen Receptors (CAR) are now FDA-approved for the treatment of B-cell malignancies. Yet, the functionality of the endogenous TCR in CART cells has not been fully assessed. Here, we demonstrate that CART cells progressively upregulate Fas, FasL, DR5 and TRAIL, which result in their programmed cell death, independently of antigen-mediated TCR or CAR activation. CART cell apoptosis occurs even when the CAR contains a single (co-)activatory domain such as CD3ζ, CD28 or 4-1BB. Importantly, the dominant role of the Fas and DR5 pathways in CART cell apoptosis is demonstrated by the significant rescue of CART cells upon in vivo blockade by combined Fas-Fc and DR5-Fc recombinant proteins. These observations are of crucial importance for the long-term persistence of CART cells and for the development of new applications including the combined TCR and CAR activation against solid tumors.

Tuning ITAM multiplicity on T cell receptors can control potency and selectivity to ligand density

The T cell antigen receptor (TCR) recognizes peptides from pathogenic proteins bound in the major histocompatibility complex (MHC). To convert this binding event into downstream signaling, the TCR complex contains immunoreceptor tyrosine-based activation motifs (ITAMs) that act as docking sites for the cytoplasmic tyrosine kinase ZAP-70. Unique among antigen receptors, the TCR complex uses 10 ITAMs to transduce peptide-MHC binding to the cell interior. Using synthetic, drug-inducible receptor-ligand pairs, it was found that greater ITAM multiplicity primarily enhanced the efficiency with which ligand binding was converted into an intracellular signal. This manifested as an increase in the fraction of cells that became activated in response to antigen, and a more synchronous initiation of TCR-proximal signaling, rather than direct amplification of the intracellular signals. Exploiting these findings, the potency and selectivity of chimeric antigen receptors targeted against cancer were substantially enhanced by modulating the number of encoded ITAMs.

The cytosolic domain of T-cell receptor ζ associates with membranes in a dynamic equilibrium and deeply penetrates the bilayer

Interactions between lipid bilayers and the membrane-proximal regions of membrane-associated proteins play important roles in regulating membrane protein structure and function. The T-cell antigen receptor is an assembly of eight single-pass membrane-spanning subunits on the surface of T lymphocytes that initiates cytosolic signaling cascades upon binding antigens presented by MHC-family proteins on antigen-presenting cells. Its ζ-subunit contains multiple cytosolic immunoreceptor tyrosine-based activation motifs involved in signal transduction, and this subunit by itself is sufficient to couple extracellular stimuli to intracellular signaling events. Interactions of the cytosolic domain of ζ (ζcyt) with acidic lipids have been implicated in the initiation and regulation of transmembrane signaling. ζcyt is unstructured in solution. Interaction with acidic phospholipids induces structure, but its disposition when bound to lipid bilayers is controversial. Here, using surface plasmon resonance and neutron reflection, we characterized the interaction of ζcyt with planar lipid bilayers containing mixtures of acidic and neutral lipids. We observed two binding modes of ζcyt to the bilayers in dynamic equilibrium: one in which ζcyt is peripherally associated with lipid headgroups and one in which it penetrates deeply into the bilayer. Such an equilibrium between the peripherally bound and embedded forms of ζcyt apparently controls accessibility of the immunoreceptor tyrosine-based activation signal transduction pathway. Our results reconcile conflicting findings of the ζ structure reported in previous studies and provide a framework for understanding how lipid interactions regulate motifs to tyrosine kinases and may regulate the T-cell antigen receptor biological activities for this cell-surface receptor system.

Cellular kinetics of CTL019 in relapsed/refractory B-cell acute lymphoblastic leukemia and chronic lymphocytic leukemia

Tisagenlecleucel (CTL019) is an investigational immunotherapy that involves reprogramming a patient's own T cells with a transgene encoding a chimeric antigen receptor to identify and eliminate CD19-expressing cells. We previously reported that CTL019 achieved impressive clinical efficacy in patients with relapsed/refractory B-cell acute lymphoblastic leukemia (ALL) and chronic lymphocytic leukemia (CLL), including the expansion and persistence of CTL019 cells, which correlates with response to therapy. Here, we performed formal cellular kinetic analyses of CTL019 in a larger cohort of 103 patients treated with CTL019 in 2 different diseases (ALL and CLL). CTL019 was measured in peripheral blood and bone marrow, using quantitative polymerase chain reaction and flow cytometry. CTL019 levels in peripheral blood typically peaked at 10 to 14 days postinfusion and then declined slowly over time. Patients with complete response (CR)/CR with incomplete count recovery had higher levels of CTL019 in peripheral blood, with greater maximal concentration and area under the curve values compared with nonresponding patients (P < .0001 for each). CTL019 transgene levels were measurable up to 780 days in peripheral blood. CTL019 trafficking and persistence were observed in bone marrow and cerebrospinal fluid. CTL019 expansion correlated with severity of cytokine release syndrome (CRS) and preinfusion tumor burden in pediatric ALL. The results described here are the first detailed formal presentation of cellular kinetics across 2 diseases and highlight the importance of the application of in vivo cellular kinetic analyses to characterize clinical efficacy and CRS severity associated with CTL019 therapy.

Engineering Chimeric Antigen Receptors

Chimeric antigen receptors (CARs) are recombinant protein molecules that redirect cytotoxic lymphocytes toward malignant and other target cells. The high feasibility of manufacturing CAR-modified lymphocytes for the therapy of cancer has spurred the development and optimization of new CAR T cells directed against a broad range of target antigens. In this review, we describe the main structural and functional elements constituting a CAR, discuss the roles of these elements in modulating the anti-tumor activity of CAR T cells, and highlight alternative approaches to CAR engineering.

Smart CARs engineered for cancer immunotherapy

PURPOSE OF REVIEW

Chimeric antigen receptors (CARs) are synthetic immunoreceptors, which can redirect T cells to selectively kill tumor cells, and as 'living drugs' have the potential to generate long-term antitumor immunity. Given their recent clinical successes for the treatment of refractory B-cell malignancies, there is a strong push toward advancing this immunotherapy to other hematological diseases and solid cancers. Here, we summarize the current state of the field, highlighting key variables for the optimal application of CAR T cells for cancer immunotherapy.

RECENT FINDINGS

Advances in CAR T-cell therapy have highlighted intrinsic CAR design and T-cell manufacturing methods as critical components for maximal therapeutic success. Similarly, addressing the unique extrinsic challenges of each tumor type, including overcoming the immunosuppressive tumor microenvironment and tumor heterogeneity, and mitigating potential toxicity, will dominate the next wave of CAR T-cell development.

SUMMARY

CAR T-cell therapeutic optimization, including intrinsic and extrinsic factors, is critical to developing effective CAR T-cell therapies for cancer. The excitement of CAR T-cell immunotherapy has just begun, and will continue with new insights revealed in laboratory research and in ongoing clinical investigations.

Challenges and opportunities of allogeneic donor-derived CAR T cells

PURPOSE OF REVIEW

As T cells engineered with chimeric antigen receptors (CARs) are entering advanced phases of clinical trial testing with promising results, the potential implications of use in an allogeneic environment are emerging as an important consideration. This review discusses the use of allogeneic CAR therapy, the potential effects of T-cell receptor (TCR) signaling on CAR T-cell efficacy, and the potential for TCR elimination to generate an off-the-shelf product.

RECENT FINDINGS

The majority of preclinical and clinical data regarding allogeneic T cells are focused on safety of their use given the potential for graft-versus-host disease (GVHD) mediated by the T-cell receptor expressed with the introduced CAR. Recent clinical trials using donor-derived CAR T cells are using either rigorous patient selection or T-cell selection (such as enrichment for virus-specific T cells). Although no GVHD has been reported, the efficacy of the allogeneic CAR treatment needs to be optimized. Several preclinical models limit allogeneic CAR-driven GVHD by utilizing memory T-cell selection, virus-specific T cells, gene-editing techniques, or suicide gene engineering.

SUMMARY

In the allogeneic environment, the potential effects of TCR signaling on the efficacy of CAR could affect the clinical responses with the use of donor-derived CAR T cells. Better understanding of the functionality of donor-derived T cells for therapy is essential for the development of universal effector cells for CAR therapy.

Clinical pharmacology of CAR-T cells: Linking cellular pharmacodynamics to pharmacokinetics and antitumor effects

Adoptive cell transfer of T cells genetically modified with tumor-reactive chimeric antigen receptors (CARs) is a rapidly emerging field in oncology, which in preliminary clinical trials has already shown striking antitumor efficacy. Despite these premises, there are still a number of open issues related to CAR-T cells, spanning from their exact mechanism of action (pharmacodynamics), to the factors associated with their in vivo persistence (pharmacokinetics), and, finally, to the relative contribution of each of the two in determining the antitumor effects and accompanying toxicities. In light of the unprecedented curative potential of CAR-T cells and of their predicted wide availability in the next few years, in this review we will summarize the current knowledge on the clinical pharmacology aspects of what is anticipated to be a brand new class of biopharmaceuticals to join the therapeutic armamentarium of cancer doctors.