Programmable synthetic receptors: the next-generation of cell and gene therapies

Designer mammalian living materials through genetic engineering

Emerging genome editing and synthetic biology toolboxes can accurately program mammalian cells behavior from the inside-out. Such engineered living units can be perceived as key building blocks for bioengineering mammalian cell-dense materials, with promising features to be used as living therapeutics for tissue engineering or disease modeling applications. Aiming to reach full control over the code that governs cell behavior, inside-out engineering approaches have potential to fully unlock user-defined living materials encoded with tailored cellular functionalities and spatial arrangements. Dwelling on this, herein, we discuss the most recent advances and opportunities unlocked by genetic engineering strategies, and on their use for the assembly of next-generation cell-rich or cell-based materials, with an unprecedent control over cellular arrangements and customizable therapeutic capabilities. We envision that the continuous synergy between inside-out and outside-in cell engineering approaches will potentiate the future development of increasingly sophisticated cell assemblies that may operate with augmented biofunctionalities.

Neoleukin-2/15-armored CAR-NK cells sustain superior therapeutic efficacy in solid tumors via c-Myc/NRF1 activation

Adoptive transfer of chimeric antigen receptor (CAR)-modified natural killer (NK) cells represents a transformative approach that has significantly advanced clinical outcomes in patients with malignant hematological conditions. However, the efficacy of CAR-NK cells in treating solid tumors is limited by their exhaustion, impaired infiltration and poor persistence in the immunosuppressive tumor microenvironment (TME). As NK cell functional states are associated with IL-2 cascade, we engineered mesothelin-specific CAR-NK cells that secrete neoleukin-2/15 (Neo-2/15), an IL-2Rβγ agonist, to resist immunosuppressive polarization within TME. The adoptively transferred Neo-2/15-armored CAR-NK cells exhibited enhanced cytotoxicity, less exhaustion and longer persistence within TME, thereby having superior antitumor activity against pancreatic cancer and ovarian cancer. Mechanistically, Neo-2/15 provided sustained and enhanced downstream IL-2 receptor signaling, which promotes the expression of c-Myc and nuclear respiratory factor 1 (NRF1) in CAR-NK cells. This upregulation was crucial for maintaining mitochondrial adaptability and metabolic resilience, ultimately leading to increased cytotoxicity and pronounced persistence of CAR-NK cells within the TME. The resistance against TME immunosuppressive polarization necessitated the upregulation of NRF1, which is essential to the augmentative effects elicited by Neo-2/15. Overexpression of NRF1 significantly bolsters the antitumor efficacy of CAR-NK cells both in vitro and in vivo, with increased ATP production. Collectively, Neo-2/15-expressing CAR-NK cells exerts superior antitumor effects by exhaustion-resistance and longer survival in solid tumors.

Blood cancer therapy with synthetic receptors and CRISPR technology

Chimeric antigen receptor (CAR)-T and -NK cells showed great success in treating hematological malignancies, including leukemia, lymphoma, and myeloma. CRISPR technology and other synthetic receptors (GPCR and synNotch) have helped to address some of the limitations and challenges associated with CAR-based therapies. Herein, this review aims to discuss how CAR can be integrated with other synthetic receptors and various CRISPR/Cas tools for blood cancer therapy. CAR-expressing cells equipped with other synthetic receptors can conditionally execute tumoricidal functions, prevent tumor escape from immune surveillance, and minimize non-tumor off-target toxicity. We also discussed how various CRISPR-Cas tools can be harnessed to enhance CAR cells functionality and persistence. The advances, pitfalls, and future perspectives for these synthetic receptors and CRISPR technology in blood cancer therapy are comprehensively discussed.

Novel strategies to manage CAR-T cell toxicity

The immune-related adverse events associated with chimeric antigen receptor (CAR)-T cell therapy result in substantial morbidity as well as considerable cost to the health-care system, and can limit the use of these treatments. Current therapeutic strategies to manage immune-related adverse events include interleukin-6 receptor (IL-6R) blockade and corticosteroids. However, because these interventions do not always address the side effects, nor prevent progression to higher grades of adverse events, new approaches are needed. A deeper understanding of the cell types involved, and their associated signalling pathways, cellular metabolism and differentiation states, should provide the basis for alternative strategies. To preserve treatment efficacy, cytokine-mediated toxicity needs to be uncoupled from CAR-T cell function, expansion, long-term persistence and memory formation. This may be achieved by targeting CAR or independent cytokine signalling axes transiently, and through novel T cell engineering strategies, such as low-affinity CAR-T cells, reversible on-off switches and versatile adaptor systems. We summarize the current management of cytokine release syndrome and immune effector cell-associated neurotoxicity syndrome, and review T cell- and myeloid cell-intrinsic druggable targets and cellular engineering strategies to develop safer CAR-T cells.

Engineered receptors for soluble cellular communication and disease sensing

Despite recent advances in mammalian synthetic biology, there remains a lack of modular synthetic receptors that can robustly respond to soluble ligands and, in turn, activate bespoke cellular functions. Such receptors would have extensive clinical potential to regulate the activity of engineered therapeutic cells, but so far only receptors against cell-surface targets have approached clinical translation1. To address this gap, here we adapt a receptor architecture called the synthetic intramembrane proteolysis receptor (SNIPR) for activation by soluble ligands. Our SNIPR platform can be activated by both natural and synthetic soluble factors, with notably low baseline activity and high fold activation, through an endocytic, pH-dependent cleavage mechanism. We demonstrate the therapeutic capabilities of the receptor platform by localizing the activity of chimeric antigen receptor (CAR) T cells to solid tumours in which soluble disease-associated factors are expressed, bypassing the major hurdle of on-target off-tumour toxicity in bystander organs. We further apply the SNIPR platform to engineer fully synthetic signalling networks between cells orthogonal to natural signalling pathways, expanding the scope of synthetic biology. Our design framework enables cellular communication and environmental interactions, extending the capabilities of synthetic cellular networking in clinical and research contexts.

Ligand-restricted synNotch switches enable precision cell therapy

Lim and colleagues demonstrate that synNotch transcriptional circuits engineered into T cells can be used to precisely control location-specific expression of payloads responding to antigen triggers, thus locally inhibiting unwanted immunity or neuroinflammation. With no off-tumor toxicity or systemic immunosuppression upon elimination of mouse brain tumors, this approach can achieve better efficacy than anticipated.

Exploring the potential of CAR-macrophage therapy

Chimeric antigen receptor T cell (CAR-T) cell therapy has achieved significant success in treating hematologic malignancies, but its efficacy in solid tumor treatment is relatively limited. Therefore, researchers are exploring other genetically modified immune cells as potential treatment strategies to address the challenges in solid tumor therapy. Chimeric antigen receptor macrophage (CAR-M) involves the genetic engineering of macrophages to express chimeric antigen receptors, enabling them to recognize and attack tumor cells. In contrast to CAR-T cells, CAR-M cells offer distinct advantages such as enhanced infiltration and survival capabilities, along with a diverse array of anti-tumor mechanisms, making them a promising immunotherapy approach that may yield better results in solid tumor treatment. This article provides an overview of the research advancements in CAR-M-mediated tumor immunotherapy, encompassing topics such as the design and transduction of CAR, cell sources, anti-tumor mechanisms and clinical applications. The future research direction in this field will involve leveraging innovative biological technologies to augment the anti-tumor efficacy of CAR-M, understand the underlying mechanisms, and enhance the safety and efficacy of CAR-M therapy.

Engineering a controllable and reversible switch for CAR-based cellular immunotherapies via a genetic code expansion system

BACKGROUND

As one of the most promising adoptive cell therapies, CAR-T cell therapy has achieved notable clinical effects in patients with hematological tumors. However, several treatment-related obstacles remain in CAR-T therapy, such as cytokine release syndrome, neurotoxicity, and high-frequency recurrence, which severely limit the long-term effects and can potentially be fatal. Therefore, strategies to increase the controllability and safety of CAR-T therapy are urgently needed.

METHODS

In this study, we engineered a genetic code expansion-based therapeutic system to achieve rapid CAR protein expression and regulation in response to cognate unnatural amino acids at the translational level. When the unnatural amino acid N-ε-((tert-butoxy) carbonyl)-l-lysine (BOCK) is absent, the CAR protein cannot be completely translated, and CAR-T is "closed". When BOCK is present, complete translation of the CAR protein is induced, and CAR-T is "open". Therefore, we investigated whether the BOCK-induced device can control CAR protein expression and regulate CAR-T cell function using a series of in vitro and in vivo experiments.

RESULTS

First, we verified that the BOCK-induced genetic code expansion system enables the regulation of protein expression as a controllable switch. We subsequently demonstrated that when the system was combined with CAR-T cells, BOCK could effectively and precisely control CAR protein expression and induce CAR signaling activation. When incubated with tumor cells, BOCK regulated CAR-T cells cytotoxicity in a dose-dependent manner. Our results revealed that the presence of BOCK enables the activation of CAR-T cells with strong anti-tumor cytotoxicity in a NOG mouse model. Furthermore, we verified that the BOCK-induced CAR device provided NK cells with controllable anti-tumor activity, which confirmed the universality of this device.

CONCLUSIONS

Our study systematically demonstrated that the BOCK-induced genetic code expansion system effectively and precisely regulates CAR protein expression and controls CAR-T cell anti-tumor effects in vitro and in vivo. We conclude that this controllable and reversible switch has the potential for more effective, secure, and clinically available CAR-based cellular immunotherapies.

The development and application of chimeric antigen receptor natural killer (CAR-NK) cells for cancer therapy: current state, challenges and emerging therapeutic advances

Immunotherapy has transformed the landscape of cancer treatment, with chimeric antigen receptor (CAR)-engineered T (CAR-T) cell therapy emerging as a front runner in addressing some hematological malignancies. Despite its considerable efficacy, the occurrence of severe adverse effects associated with CAR-T cell therapy has limited their scope and prompted the exploration of alternative therapeutic strategies. Natural killer (NK) cells, characterized by both their innate cytotoxicity and ability to lyse target cells without the constraint of peptide specificity conferred by a major histocompatibility complex (MHC), have similarly garnered attention as a viable immunotherapy. As such, another therapeutic approach has recently emerged that seeks to combine the continued success of CAR-T cell therapy with the flexibility of NK cells. Clinical trials involving CAR-engineered NK (CAR-NK) cell therapy have exhibited promising efficacy with fewer deleterious side effects. This review aims to provide a concise overview of the cellular and molecular basis of NK cell biology, facilitating a better understanding of advancements in CAR design and manufacturing. The focus is on current approaches and strategies employed in CAR-NK cell development, exploring at both preclinical and clinical settings. We will reflect upon the achievements, advantages, and challenges intrinsic to CAR-NK cell therapy. Anticipating the maturation of CAR-NK cell therapy technology, we foresee its encouraging prospects for a broader range of cancer patients and other conditions. It is our belief that this CAR-NK progress will bring us closer to making significant strides in the treatment of refractory and recurrent cancers, as well as other immune-mediated disorders.

Exploring structure-function relationships in engineered receptor performance using computational structure prediction

Engineered receptors play increasingly important roles in transformative cell-based therapies. However, the structural mechanisms that drive differences in performance across receptor designs are often poorly understood. Recent advances in protein structural prediction tools have enabled the modeling of virtually any user-defined protein, but how these tools might build understanding of engineered receptors has yet to be fully explored. In this study, we employed structural modeling tools to perform post hoc analyses to investigate whether predicted structural features might explain observed functional variation. We selected a recently reported library of receptors derived from natural cytokine receptors as a case study, generated structural models, and from these predictions quantified a set of structural features that plausibly impact receptor performance. Encouragingly, for a subset of receptors, structural features explained considerable variation in performance, and trends were largely conserved across structurally diverse receptor sets. This work indicates potential for structure prediction-guided synthetic receptor engineering.

SynNotch-Programmed Macrophages for Cancerous Cell Detection and Sensing

Synthetic Notch (synNotch) receptors have enabled mammalian cells to sense extracellular ligands and respond by activating user-prescribed transcriptional programs. Based on the synNotch system, we describe a cell-based in vivo sensor for cancerous cell detection. We attempted to engineer synNotch-programmed macrophages to sense cancer cells via urinary analysis of human chorionic gonadotropin (HCGB5). Principally, when the synNotch receptors of macrophages bind to the ligands of cancer cells, Notch is activated and undergoes intramembrane proteolysis to release the transcriptional activator into the nucleus. The transcriptional activator targets and activates downstream gene expression, such as human chorionic gonadotropin (HCGB5) in macrophages. When HCGB5 is secreted extracellularly into urine, it can be detected with commercial HCGB5 colloidal gold test strips. As a proof of principle, we demonstrated the feasibility of synNotch-programmed macrophages in detecting breast cancer cells engineered with artificial EGFP ligands. We demonstrated that HCGB5 expression was only induced when the cancer cell expressing EGFP ligands is present; thereby, extracellular HCGB5 expression is directly proportional to the number of cancer cells. Further optimizations of the synNotch system can realize the ultimate goal of establishing cell-based in vivo sensors as the paragon of cancer diagnostics for point-of-care testing and home self-test.

Positions of cysteine residues reveal local clusters and hidden relationships to Sequons and Transmembrane domains in Human proteins

Membrane proteins often possess critical structural features, such as transmembrane domains (TMs), N-glycosylation, and disulfide bonds (SS bonds), which are essential to their structure and function. Here, we extend the study of the motifs carrying N-glycosylation, i.e. the sequons, and the Cys residues supporting the SS bonds, to the whole human proteome with a particular focus on the Cys positions in human proteins with respect to those of sequons and TMs. As the least abundant amino acid residue in protein sequences, the positions of Cys residues in proteins are not random but rather selected through evolution. We discovered that the frequency of Cys residues in proteins is length dependent, and the frequency of CC gaps formed between adjacent Cys residues can be used as a classifier to distinguish proteins with special structures and functions, such as keratin-associated proteins (KAPs), extracellular proteins with EGF-like domains, and nuclear proteins with zinc finger C2H2 domains. Most importantly, by comparing the positions of Cys residues to those of sequons and TMs, we discovered that these structural features can form dense clusters in highly repeated and mutually exclusive modalities in protein sequences. The evolutionary advantages of such complementarity among the three structural features are discussed, particularly in light of structural dynamics in proteins that are lacking from computational predictions. The discoveries made here highlight the sequence-structure-function axis in biological organisms that can be utilized in future protein engineering toward synthetic biology.

Advances in Bioinspired Artificial System Enabling Biomarker-Driven Therapy

Bioinspired molecular engineering strategies have emerged as powerful tools that significantly enhance the development of novel therapeutics, improving efficacy, specificity, and safety in disease treatment. Recent advancements have focused on identifying and utilizing disease-associated biomarkers to optimize drug activity and address challenges inherent in traditional therapeutics, such as frequent drug administrations, poor patient adherence, and increased risk of adverse effects. In this review, we provide a comprehensive overview of the latest developments in bioinspired artificial systems (BAS) that use molecular engineering to tailor therapeutic responses to drugs in the presence of disease-specific biomarkers. We examine the transition from open-loop systems, which rely on external cues, to closed-loop feedback systems capable of autonomous self-regulation in response to disease-associated biomarkers. We detail various BAS modalities designed to achieve biomarker-driven therapy, including activatable prodrug molecules, smart drug delivery platforms, autonomous artificial cells, and synthetic receptor-based cell therapies, elucidating their operational principles and practical in vivo applications. Finally, we discuss the current challenges and future perspectives in the advancement of BAS-enabled technology and envision that ongoing advancements toward more programmable and customizable BAS-based therapeutics will significantly enhance precision medicine.

The next frontier in immunotherapy: potential and challenges of CAR-macrophages

Chimeric antigen receptor macrophage (CAR-MΦ) represents a significant advancement in immunotherapy, especially for treating solid tumors where traditional CAR-T therapies face limitations. CAR-MΦ offers a promising approach to target and eradicate tumor cells by utilizing macrophages' phagocytic and antigen-presenting abilities. However, challenges such as the complex tumor microenvironment (TME), variability in antigen expression, and immune suppression limit their efficacy. This review addresses these issues, exploring mechanisms of CAR-MΦ action, optimal construct designs, and interactions within the TME. It also delves into the ex vivo manufacturing challenges of CAR-MΦ, discussing autologous and allogeneic sources and the importance of stringent quality control. The potential synergies of integrating CAR-MΦ with existing cancer therapies like checkpoint inhibitors and conventional chemotherapeutics are examined to highlight possible enhanced treatment outcomes. Furthermore, regulatory pathways for CAR-MΦ therapies are scrutinized alongside established protocols for CAR-T cells, identifying unique considerations essential for clinical trials and market approval. Proposed safety monitoring frameworks aim to manage potential adverse events, such as cytokine release syndrome, crucial for patient safety. Consolidating current research and clinical insights, this review seeks to refine CAR-MΦ therapeutic applications, overcome barriers, and suggest future research directions to transition CAR-MΦ therapies from experimental platforms to standard cancer care options.

Biosimilars in the Era of Artificial Intelligence-International Regulations and the Use in Oncological Treatments

This research is based on three fundamental aspects of successful biosimilar development in the challenging biopharmaceutical market. First, biosimilar regulations in eight selected countries: Japan, South Korea, the United States, Canada, Brazil, Argentina, Australia, and South Africa, represent the four continents. The regulatory aspects of the countries studied are analyzed, highlighting the challenges facing biosimilars, including their complex approval processes and the need for standardized regulatory guidelines. There is an inconsistency depending on whether the biosimilar is used in a developed or developing country. In the countries observed, biosimilars are considered excellent alternatives to patent-protected biological products for the treatment of chronic diseases. In the second aspect addressed, various analytical AI modeling methods (such as machine learning tools, reinforcement learning, supervised, unsupervised, and deep learning tools) were analyzed to observe patterns that lead to the prevalence of biosimilars used in cancer to model the behaviors of the most prominent active compounds with spectroscopy. Finally, an analysis of the use of active compounds of biosimilars used in cancer and approved by the FDA and EMA was proposed.

Engineered immune cells as therapeutics for autoimmune diseases

Current treatment options for autoimmune disease (AID) are essentially immunosuppressive, inhibiting the inflammatory cascade, without curing the disease. Therapeutic monoclonal antibodies (mAbs) that target B cells showed efficacy, emphasizing the importance of B lymphocytes in autoimmune pathogenesis. Treatments that eliminate more potently B cells would open a new therapeutic era for AID. Immune cells can now be bioengineered to express constructs that enable them to specifically eradicate pathogenic B lymphocytes. Engineered immune cells (EICs) have shown therapeutic promise in both experimental models and in clinical trials in AID. Next-generation platforms are under development to optimize their specificity and improve safety. The profound and durable B cell depletion achieved reinforces the view that this biotherapeutic option holds promise for treating AID.

A Roadmap of CAR-T-Cell Therapy in Glioblastoma: Challenges and Future Perspectives

Glioblastoma (GBM) is the most common primary malignant brain tumor, with a median overall survival of less than 2 years and a nearly 100% mortality rate under standard therapy that consists of surgery followed by combined radiochemotherapy. Therefore, new therapeutic strategies are urgently needed. The success of chimeric antigen receptor (CAR) T cells in hematological cancers has prompted preclinical and clinical investigations into CAR-T-cell treatment for GBM. However, recent trials have not demonstrated any major success. Here, we delineate existing challenges impeding the effectiveness of CAR-T-cell therapy for GBM, encompassing the cold (immunosuppressive) microenvironment, tumor heterogeneity, T-cell exhaustion, local and systemic immunosuppression, and the immune privilege inherent to the central nervous system (CNS) parenchyma. Additionally, we deliberate on the progress made in developing next-generation CAR-T cells and novel innovative approaches, such as low-intensity pulsed focused ultrasound, aimed at surmounting current roadblocks in GBM CAR-T-cell therapy.