The hyperactive Sleeping Beauty transposase SB100X improves the genetic modification of T cells to express a chimeric antigen receptor

Non-industrial production of therapeutic lentiviral vectors: How to provide vectors to academic CAR-T

Bringing effective cancer therapy in the form of chimeric antigen receptor technology to untapped markets faces numerous challenges, including a global shortage of therapeutic lentiviral or retroviral vectors on which all current clinical therapies using genetically modified T cells are based. Production of these lentiviral vectors in academic settings in principle opens the way to local production of therapeutic cells, which is the only economically viable approach to make this therapy available to patients in developing countries. The conditions for obtaining and concentrating lentiviral vectors have been optimized and described. The calcium phosphate precipitation method was found to be suitable for transfecting high cell-density cultures, a prerequisite for high titers. We describe protocols for gradually increasing production from 6-well plates to P100 plates, T-175 flasks, and 5-layer stacks while maintaining high titers, >108 transducing units. Concentration experiments using ultracentrifugation revealed the advantage of lower centrifugation speeds compared to competing protocols. The resulting batches of lentiviral vectors had a titer of 1010 infectious particles and were used to transduce primary human T lymphocytes generating chimeric antigen receptor T cells, the quality of which was checked and found potential applicability for treatment.

Engineering strategies to safely drive CAR T-cells into the future

Chimeric antigen receptor (CAR) T-cell therapy has proven a breakthrough in cancer treatment in the last decade, giving unprecedented results against hematological malignancies. All approved CAR T-cell products, as well as many being assessed in clinical trials, are generated using viral vectors to deploy the exogenous genetic material into T-cells. Viral vectors have a long-standing clinical history in gene delivery, and thus underwent iterations of optimization to improve their efficiency and safety. Nonetheless, their capacity to integrate semi-randomly into the host genome makes them potentially oncogenic via insertional mutagenesis and dysregulation of key cellular genes. Secondary cancers following CAR T-cell administration appear to be a rare adverse event. However several cases documented in the last few years put the spotlight on this issue, which might have been underestimated so far, given the relatively recent deployment of CAR T-cell therapies. Furthermore, the initial successes obtained in hematological malignancies have not yet been replicated in solid tumors. It is now clear that further enhancements are needed to allow CAR T-cells to increase long-term persistence, overcome exhaustion and cope with the immunosuppressive tumor microenvironment. To this aim, a variety of genomic engineering strategies are under evaluation, most relying on CRISPR/Cas9 or other gene editing technologies. These approaches are liable to introduce unintended, irreversible genomic alterations in the product cells. In the first part of this review, we will discuss the viral and non-viral approaches used for the generation of CAR T-cells, whereas in the second part we will focus on gene editing and non-gene editing T-cell engineering, with particular regard to advantages, limitations, and safety. Finally, we will critically analyze the different gene deployment and genomic engineering combinations, delineating strategies with a superior safety profile for the production of next-generation CAR T-cell.

Evolution of the clinical-stage hyperactive TcBuster transposase as a platform for robust non-viral production of adoptive cellular therapies

Cellular therapies for the treatment of human diseases, such as chimeric antigen receptor (CAR) T and natural killer (NK) cells have shown remarkable clinical efficacy in treating hematological malignancies; however, current methods mainly utilize viral vectors that are limited by their cargo size capacities, high cost, and long timelines for production of clinical reagent. Delivery of genetic cargo via DNA transposon engineering is a more timely and cost-effective approach, yet has been held back by less efficient integration rates. Here, we report the development of a novel hyperactive TcBuster (TcB-M) transposase engineered through structure-guided and in vitro evolution approaches that achieves high-efficiency integration of large, multicistronic CAR-expression cassettes in primary human cells. Our proof-of-principle TcB-M engineering of CAR-NK and CAR-T cells shows low integrated vector copy number, a safe insertion site profile, robust in vitro function, and improves survival in a Burkitt lymphoma xenograft model in vivo. Overall, TcB-M is a versatile, safe, efficient and open-source option for the rapid manufacture and preclinical testing of primary human immune cell therapies through delivery of multicistronic large cargo via transposition.

CAR-T-Cell-Based Cancer Immunotherapies: Potentials, Limitations, and Future Prospects

Cancer encompasses various elements occurring at the cellular and genetic levels, necessitating an immunotherapy capable of efficiently addressing both aspects. T cells can combat cancer cells by specifically recognizing antigens on them. This innate capability of T cells has been used to develop cellular immunotherapies, but most of them can only target antigens through major histocompatibility complexes (MHCs). New gene-editing techniques such as clustered regularly interspaced short palindromic repeat (CRISPR)-associated protein 9 (CRISPR-cas9) can precisely edit the DNA sequences. CRISPR-cas9 has made it possible to generate genetically engineered chimeric antigen receptors (CARs) that can overcome the problems associated with old immunotherapies. In chimeric antigen receptor T (CAR-T) cell therapy, the patient's T cells are isolated and genetically modified to exhibit synthetic CAR(s). CAR-T cell treatment has shown remarkably positive clinical outcomes in cancers of various types. Nevertheless, there are various challenges that reduce CAR-T effectiveness in solid tumors. It is required to address these challenges in order to make CAR-T cell therapy a better and safer option. Combining CAR-T treatment with other immunotherapies that target multiple antigens has shown positive outcomes. Moreover, recently generated Boolean logic-gated advanced CARs along with artificial intelligence has expanded its potential to treat solid tumors in addition to blood cancers. This review aims to describe the structure, types, and various methods used to develop CAR-T cells. The clinical applications of CAR-T cells in hematological malignancies and solid tumours have been described in detail. In addition, this discussion has addressed the limitations associated with CAR-T cells, explored potential strategies to mitigate CAR-T-related toxicities, and delved into future perspectives.

Targeted gene delivery systems for T-cell engineering

T lymphocytes are indispensable for the host systems of defense against pathogens, tumors, and environmental threats. The therapeutic potential of harnessing the cytotoxic properties of T lymphocytes for antigen-specific cell elimination is both evident and efficacious. Genetically engineered T-cells, such as those employed in CAR-T and TCR-T cell therapies, have demonstrated significant clinical benefits in treating cancer and autoimmune disorders. However, the current landscape of T-cell genetic engineering is dominated by strategies that necessitate in vitro T-cell isolation and modification, which introduce complexity and prolong the development timeline of T-cell based immunotherapies. This review explores the complexities of gene delivery systems designed for T cells, covering both viral and nonviral vectors. Viral vectors are known for their high transduction efficiency, yet they face significant limitations, such as potential immunogenicity and the complexities involved in large-scale production. Nonviral vectors, conversely, offer a safer profile and the potential for scalable manufacturing, yet they often struggle with lower transduction efficiency. The pursuit of gene delivery systems that can achieve targeted gene transfer to T cell without the need for isolation represents a significant advancement in the field. This review assesses the design principles and current research progress of such systems, highlighting the potential for in vivo gene modification therapies that could revolutionize T-cell based treatments. By providing a comprehensive analysis of these systems, we aim to contribute valuable insights into the future development of T-cell immunotherapy.

AAV-mediated delivery of a Sleeping Beauty transposon and an mRNA-encoded transposase for the engineering of therapeutic immune cells

Engineering cells for adoptive therapy requires overcoming limitations in cell viability and, in the efficiency of transgene delivery, the duration of transgene expression and the stability of genomic integration. Here we report a gene-delivery system consisting of a Sleeping Beauty (SB) transposase encoded into a messenger RNA delivered by an adeno-associated virus (AAV) encoding an SB transposon that includes the desired transgene, for mediating the permanent integration of the transgene. Compared with lentiviral vectors and with the electroporation of plasmids of transposon DNA or minicircle DNA, the gene-delivery system, which we named MAJESTIC (for 'mRNA AAV-SB joint engineering of stable therapeutic immune cells'), offers prolonged transgene expression, as well as higher transgene expression, therapeutic-cell yield and cell viability. MAJESTIC can deliver chimeric antigen receptors (CARs) into T cells (which we show lead to strong anti-tumour activity in vivo) and also transduce natural killer cells, myeloid cells and induced pluripotent stem cells with bi-specific CARs, kill-switch CARs and synthetic T-cell receptors.

Anti-CD117 CAR T cells incorporating a safety switch eradicate human acute myeloid leukemia and hematopoietic stem cells

Discrimination between hematopoietic stem cells and leukemic stem cells remains a major challenge for acute myeloid leukemia immunotherapy. CAR T cells specific for the CD117 antigen can deplete malignant and healthy hematopoietic stem cells before consolidation with allogeneic hematopoietic stem cell transplantation in absence of cytotoxic conditioning. Here we exploit non-viral technology to achieve early termination of CAR T cell activity to prevent incoming graft rejection. Transient expression of an anti-CD117 CAR by mRNA conferred T cells the ability to eliminate CD117+ targets in vitro and in vivo. As an alternative approach, we used a Sleeping Beauty transposon vector for the generation of CAR T cells incorporating an inducible Caspase 9 safety switch. Stable CAR expression was associated with high proportion of T memory stem cells, low levels of exhaustion markers, and potent cellular cytotoxicity. Anti-CD117 CAR T cells mediated depletion of leukemic cells and healthy hematopoietic stem cells in NSG mice reconstituted with human leukemia or CD34+ cord blood cells, respectively, and could be terminated in vivo. The use of a non-viral technology to control CAR T cell pharmacokinetic properties is attractive for a first-in-human study in patients with acute myeloid leukemia prior to hematopoietic stem cell transplantation.

Development of Beta-Amyloid-Specific CAR-Tregs for the Treatment of Alzheimer's Disease

BACKGROUND

Alzheimer's disease (AD) is a neurodegenerative disease that remains uncured. Its pathogenesis is characterized by the formation of β-amyloid (Aβ) plaques. The use of antigen-specific regulatory T cells (Tregs) through adoptive transfer has shown promise for the treatment of many inflammatory diseases, although the effectiveness of polyspecific Tregs is limited. Obtaining a sufficient number of antigen-specific Tregs from patients remains challenging.

AIMS AND METHODS

To address this problem, we used an antibody-like single-chain variable fragment from a phage library and subsequently generated a chimeric antigen receptor (CAR) targeting β-amyloid.

RESULTS

The β-amyloid-specific CARs obtained were stimulated by both recombinant and membrane-bound Aβ isolated from the murine brain. The generated CAR-Tregs showed a normal Treg phenotype, were antigen-specific activatable, and had suppressive capacity.

CONCLUSION

This study highlights the potential of CAR technology to generate antigen-specific Tregs and presents novel approaches for developing functional CARs.

Challenges and new technologies in adoptive cell therapy

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

Scalable continuous-flow electroporation platform enabling T cell transfection for cellular therapy manufacturing

Viral vectors represent a bottleneck in the manufacturing of cellular therapies. Electroporation has emerged as an approach for non-viral transfection of primary cells, but standard cuvette-based approaches suffer from low throughput, difficult optimization, and incompatibility with large-scale cell manufacturing. Here, we present a novel electroporation platform capable of rapid and reproducible electroporation that can efficiently transfect small volumes of cells for research and process optimization and scale to volumes required for applications in cellular therapy. We demonstrate delivery of plasmid DNA and mRNA to primary human T cells with high efficiency and viability, such as > 95% transfection efficiency for mRNA delivery with < 2% loss of cell viability compared to control cells. We present methods for scaling delivery that achieve an experimental throughput of 256 million cells/min. Finally, we demonstrate a therapeutically relevant modification of primary T cells using CRISPR/Cas9 to knockdown T cell receptor (TCR) expression. This study displays the capabilities of our system to address unmet needs for efficient, non-viral engineering of T cells for cell manufacturing.

Therapeutic immune cell engineering with an mRNA : AAV- Sleeping Beauty composite system

Adoptive cell therapy has shown clinical success in patients with hematological malignancies. Immune cell engineering is critical for production, research, and development of cell therapy; however, current approaches for generation of therapeutic immune cells face various limitations. Here, we establish a composite gene delivery system for the highly efficient engineering of therapeutic immune cells. This system, termed MAJESTIC ( m RNA A AV-Sleeping-Beauty J oint E ngineering of S table T herapeutic I mmune C ells), combines the merits of mRNA, AAV vector, and transposon into one composite system. In MAJESTIC, the transient mRNA component encodes a transposase that mediates permanent genomic integration of the Sleeping Beauty (SB) transposon, which carries the gene-of-interest and is embedded within the AAV vector. This system can transduce diverse immune cell types with low cellular toxicity and achieve highly efficient and stable therapeutic cargo delivery. Compared with conventional gene delivery systems, such as lentiviral vector, DNA transposon plasmid, or minicircle electroporation, MAJESTIC shows higher cell viability, chimeric antigen receptor (CAR) transgene expression, therapeutic cell yield, as well as prolonged transgene expression. CAR-T cells generated by MAJESTIC are functional and have strong anti-tumor activity in vivo . This system also demonstrates versatility for engineering different cell therapy constructs such as canonical CAR, bi-specific CAR, kill switch CAR, and synthetic TCR; and for CAR delivery into various immune cells, including T cells, natural killer cells, myeloid cells, and induced pluripotent stem cells.

Construction and Quantitative Evaluation of a Tissue-Specific Sleeping Beauty by EDL2-Specific Transposase Expression in Esophageal Squamous Carcinoma Cell Line KYSE-30

Gene delivery to esophageal tissue could provide novel treatments for diseases, such as cancer. The Sleeping Beauty (SB) transposon system, as a natural and non-viral tool, is efficient at transferring transgene into the human genome for human cell genetic engineering. The plasmid-based SB transposon can insert into chromosomes through an accurate recombinase-mediated mechanism, providing long-term expression of transgene integrated into the target cells. In this study, we aimed to investigate the activity of ED-L2 tissue-specific promoter that was engineered from the Epstein-Barr Virus (EBV) and combined with the hyperactive SB100X transposase to achieve the stable expression of T2-Onc3 transposon in esophageal squamous epithelial cells. Here we constructed an SB transposon-based plasmid system to obtain the stable expression of transposon upon introduction of a hyperactive SB transposase under the control of tissue-specific ED-L2 promoter via the lipid-based delivery method in the cultured esophageal squamous cell carcinoma cells. Among established human and mouse cell lines, the (ED-L2)-SB100X transposase was active only in human esophageal stratified squamous epithelial and differentiated keratinocytes derived from skin (KYSE-30 and HaCaT cell lines), where it revealed high promoter activity. Data offered that the 782 bp sequence of ED-L2 promoter has a key role in its activity in vitro. The (ED-L2)-SB100X transposase mediated stable integration of T2-Onc3 in KYSE-30 cells, thereby providing further evidence of the tissue specificity of ED-L2 promoter. The KYSE-30 cells modified with the SB system integrate on average 187 copies of the T2-Onc3 transposon in its genome. In aggregate, the (ED-L2)-SB100X transposase can be efficiently applied for the tissue-specific stable expression of a transgene in human KYSE-30 cells using SB transposon.

Passer, a highly active transposon from a fish genome, as a potential new robust genetic manipulation tool

The discovery of new, active DNA transposons can expand the range of genetic tools and provide more options for genomic manipulation. In this study, a bioinformatics analysis suggested that Passer (PS) transposons, which are members of the pogo superfamily, show signs of recent and current activity in animals and may be active in some species. Cell-based transposition assays revealed that the native PS transposases from Gasterosteus aculeatus and Danio rerio displayed very high activity in human cells relative to the Sleeping Beauty transposon. A typical overproduction inhibition phenomenon was observed for PS, and transposition capacity was decreased by ∼12% with each kilobase increase in the insertion size. Furthermore, PS exhibited a pronounced integration preference for genes and their transcriptional regulatory regions. We further show that two domesticated human proteins derived from PS transposases have lost their transposition activity. Overall, PS may represent an alternative with a potentially efficient genetic manipulation tool for transgenesis and mutagenesis applications.

Tn5 DNA Transposase in Multi-Omics Research

Tn5 transposase use in biotechnology has substantially advanced the sequencing applications of genome-wide analysis of cells. This is mainly due to the ability of Tn5 transposase to efficiently transpose DNA essentially randomly into any target DNA without the aid of other factors. This concise review is focused on the advances in Tn5 applications in multi-omics technologies, genome-wide profiling, and Tn5 hybrid molecule creation. The possibilities of other transposase uses are also discussed.

A Cre-LoxP-based approach for combinatorial chromosome rearrangements in human HAP1 cells

Alterations of human karyotype caused by chromosomal rearrangements are often associated with considerable phenotypic effects. Studying molecular mechanisms underlying these effects requires an efficient and scalable experimental model. Here, we propose a Cre-LoxP-based approach for the generation of combinatorial diversity of chromosomal rearrangements. We demonstrate that using the developed system, both intra- and inter-chromosomal rearrangements can be induced in the human haploid HAP1 cells, although the latter is significantly less effective. The obtained genetically modified HAP1 cell line can be used to dissect genomic effects associated with intra-chromosomal structural variations.

Noise-Reduction and Sensitivity-Enhancement of a Sleeping Beauty-Based Tet-On System

Tetracycline-inducible systems are widely used control elements for mammalian gene expression. Despite multiple iterations to improve inducibility, their use is still compromised by basal promoter activity in the absence of tetracyclines. In a mammalian system, we previously showed that the introduction of the G72V mutation in the rtTA-M2 tetracycline activator lowers the basal level expression and increases the fold-induction of multiple genetic elements in a long chimeric antigen receptor construct. In this study, we confirmed that the G72V mutation was effective in minimising background expression in the absence of an inducer, resulting in an increase in fold-expression. Loss of responsiveness due to the G72V mutation was compensated through the incorporation of four sensitivity enhancing (SE) mutations, without compromising promoter tightness. However, SE mutations alone (without G72V) led to undesirable leakiness. Although cryptic splice site removal from rtTA did not alter the inducible control of the luciferase reporter gene in this simplified vector system, this is still recommended as a precaution in more complex multi-gene elements that contain rtTA. The optimized expression construct containing G72V and SE mutations currently provides the best improvement of fold-induction mediated by the rtTA-M2 activator in a mammalian system.

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.

The Past, Present, and Future of Non-Viral CAR T Cells

Adoptive transfer of chimeric antigen receptor (CAR) T lymphocytes is a powerful technology that has revolutionized the way we conceive immunotherapy. The impressive clinical results of complete and prolonged response in refractory and relapsed diseases have shifted the landscape of treatment for hematological malignancies, particularly those of lymphoid origin, and opens up new possibilities for the treatment of solid neoplasms. However, the widening use of cell therapy is hampered by the accessibility to viral vectors that are commonly used for T cell transfection. In the era of messenger RNA (mRNA) vaccines and CRISPR/Cas (clustered regularly interspaced short palindromic repeat-CRISPR-associated) precise genome editing, novel and virus-free methods for T cell engineering are emerging as a more versatile, flexible, and sustainable alternative for next-generation CAR T cell manufacturing. Here, we discuss how the use of non-viral vectors can address some of the limitations of the viral methods of gene transfer and allow us to deliver genetic information in a stable, effective and straightforward manner. In particular, we address the main transposon systems such as Sleeping Beauty (SB) and piggyBac (PB), the utilization of mRNA, and innovative approaches of nanotechnology like Lipid-based and Polymer-based DNA nanocarriers and nanovectors. We also describe the most relevant preclinical data that have recently led to the use of non-viral gene therapy in emerging clinical trials, and the related safety and efficacy aspects. We will also provide practical considerations for future trials to enable successful and safe cell therapy with non-viral methods for CAR T cell generation.

Characterizing piggyBat-a transposase for genetic modification of T cells

Chimeric antigen receptor (CAR) T cells targeting CD19 have demonstrated remarkable efficacy in the treatment of B cell malignancies. Current CAR T cell manufacturing protocols are complex and costly due to their reliance on viral vectors. Non-viral systems of genetic modification, such as with transposase and transposon systems, offer a potential streamlined alternative for CAR T cell manufacture and are currently being evaluated in clinical trials. In this study, we utilized the previously described transposase from the little brown bat, designated piggyBat, for production of CD19-specific CAR T cells. PiggyBat demonstrates efficient CAR transgene delivery, with a relatively low variability in integration copy number across a range of manufacturing conditions as well as a similar integration site profile to super-piggyBac transposon and viral vectors. PiggyBat-generated CAR T cells demonstrate CD19-specific cytotoxic efficacy in vitro and in vivo. These data demonstrate that alternative, naturally occurring DNA transposons can be efficiently re-tooled to be exploited in real-world applications.

Towards maximum acceleration of monoclonal antibody development: Leveraging transposase-mediated cell line generation to enable GMP manufacturing within 3 months using a stable pool

In recent years, acceleration of development timelines has become a major focus within the biopharmaceutical industry to bring innovative therapies faster to patients. However, in order to address a high unmet medical need even faster further acceleration potential has to be identified to transform "speed-to-clinic" concepts into "warp-speed" development programs. Recombinant Chinese hamster ovary (CHO) cell lines are the predominant expression system for monoclonal antibodies (mAbs) and are routinely generated by random transgene integration (RTI) of the genetic information into the host cell genome. This process, however, exhibits considerable challenges such as the requirement for a time-consuming clone screening process to identify a suitable clonally derived manufacturing cell line. Hence, RTI represents an error prone and tedious method leading to long development timelines until availability of Good Manufacturing Practice (GMP)-grade drug substance (DS). Transposase-mediated semi-targeted transgene integration (STI) has been recently identified as a promising alternative to RTI as it allows for a more rapid generation of high-performing and stable production cell lines. In this report, we demonstrate how a STI technology was leveraged to develop a very robust DS manufacturing process based on a stable pool cell line at unprecedented pace. Application of the novel strategy resulted in the manufacturing of GMP-grade DS at 2,000 L scale in less than three months paving the way for a start of Phase I clinical trials only six months after transfection. Finally, using a clonally derived production cell line, which was established from the parental stable pool, we were able to successfully implement a process with an increased mAb titer of up to 5 g per liter at the envisioned commercial scale (12,000 L) within eight months.

Engineered NK Cells Against Cancer and Their Potential Applications Beyond

Cell therapy is an innovative therapeutic concept where viable cells are implanted, infused, or grafted into a patient to treat impaired or malignant tissues. The term was first introduced circa the 19th century and has since resulted in multiple breakthroughs in different fields of medicine, such as neurology, cardiology, and oncology. Lately, cell and gene therapy are merging to provide cell products with additional or enhanced properties. In this context, adoptive transfer of genetically modified cytotoxic lymphocytes has emerged as a novel treatment option for cancer patients. To this day, five cell therapy products have been FDA approved, four of which for CD19-positive malignancies and one for B-cell maturation antigen (BCMA)-positive malignancies. These are personalized immunotherapies where patient T cells are engineered to express chimeric antigen receptors (CARs) with the aim to redirect the cells against tumor-specific antigens. CAR-T cell therapies show impressive objective response rates in clinical trials that, in certain instances, may reach up to 80%. However, the life-threatening side effects associated with T cell toxicity and the manufacturing difficulties of developing personalized therapies hamper their widespread use. Recent literature suggests that Natural Killer (NK) cells, may provide a safer alternative and an 'off-the-shelf' treatment option thanks to their potent antitumor properties and relatively short lifespan. Here, we will discuss the potential of NK cells in CAR-based therapies focusing on the applications of CAR-NK cells in cancer therapy and beyond.

Enzymatically produced piggyBac transposon vectors for efficient non-viral manufacturing of CD19-specific CAR T cells

The piggyBac transposon system provides a non-viral alternative for cost-efficient and simple chimeric antigen receptor (CAR) T cell production. The generation of clinical-grade CAR T cells requires strict adherence to current good manufacturing practice (cGMP) standards. Unfortunately, the high costs of commonly used lentiviral or retroviral vectors limit the manufacturing of clinical-grade CAR T cells in many non-commercial academic institutions. Here, we present a manufacturing platform for highly efficient generation of CD19-specific CAR T cells (CAR19 T cells) based on co-electroporation of linear DNA transposon and mRNA encoding the piggyBac transposase. The transposon is prepared enzymatically in vitro by PCR and contains the CAR transgene flanked by piggyBac 3′ and 5′ arms. The mRNA is similarly prepared via in vitro transcription. CAR19 T cells are expanded in the combination of cytokines interleukin (IL)-4, IL-7, and IL-21 to prevent terminal differentiation of CAR T cells. The accurate control of vector copy number (VCN) is achieved by decreasing the concentration of the transposon DNA, and the procedure yields up to 1 × 10⁸ CAR19 T cells per one electroporation of 1 × 10⁷ peripheral blood mononuclear cells (PBMCs) after 21 days of in vitro culture. Produced cells contain >60% CAR+ cells with VCN < 3. In summary, the described manufacturing platform enables a straightforward cGMP certification, since the transposon and transposase are produced abiotically in vitro via enzymatic synthesis. It is suitable for the cost-effective production of highly experimental, early-phase CAR T cell products.

Associação Brasileira de Hematologia, Hemoterapia e Terapia Celular Consensus on genetically modified cells. VII. Present and future of technologies for production of CAR cell therapies

Chimeric Antigen Receptor T (CAR-T) cells are certainly an important therapy for patients with relapsed and/or refractory hematologic malignancies. Currently, there are five CAR-T cell products approved by the FDA but several research groups and/or biopharmaceutical companies are encouraged to develop new products based on CAR cells using T or other cell types. Production of CAR cells requires intensive work from the basic, pre-clinical to translational levels, aiming to overcome technical difficulties and failure in the production. At least five key common steps are needed for the manipulation of T-lymphocytes (or other cells), such as: cell type selection, activation, gene delivery, cell expansion and final product formulation. However, reproducible manufacturing of high-quality clinical-grade CAR cell products is still required to apply this technology to a greater number of patients. This chapter will discuss the present and future development of new CAR designs that are safer and more effective to improve this therapy, achieving more selective killing of malignant cells and less toxicity to be applied in the clinical setting.

CAR T-Cell Production Using Nonviral Approaches

Chimeric antigen receptor T-cells (CAR T-cells) represent a novel and promising approach in cancer immunotherapy. According to the World Health Organization (WHO), the number of oncological patients is steadily growing in developed countries despite immense progress in oncological treatments, and the prognosis of individual patients is still relatively poor. Exceptional results have been recorded for CAR T-cell therapy in patients suffering from B-cell malignancies. This success opens up the possibility of using the same approach for other types of cancers. To date, the most common method for CAR T-cell generation is the use of viral vectors. However, dealing with virus-derived vectors brings possible obstacles in the CAR T-cell manufacturing process owing to strict regulations and high cost demands. Alternative approaches may facilitate further development and the transfer of the method to clinical practice. The most promising substitutes for virus-derived vectors are transposon-derived vectors, most commonly sleeping beauty, which offer great coding capability and a safe integration profile while maintaining a relatively low production cost. This review is aimed at summarizing the state of the art of nonviral approaches in CAR T-cell generation, with a unique perspective on the conditions in clinical applications and current Good Manufacturing Practice. If CAR T-cell therapy is to be routinely used in medical practice, the manufacturing cost and complexity need to be as low as possible, and transposon-based vectors seem to meet these criteria better than viral-based vectors.

Genetic engineering of T cells for immunotherapy

Genetically engineered T cell immunotherapies have provided remarkable clinical success to treat B cell acute lymphoblastic leukaemia by harnessing a patient's own T cells to kill cancer, and these approaches have the potential to provide therapeutic benefit for numerous other cancers, infectious diseases and autoimmunity. By introduction of either a transgenic T cell receptor or a chimeric antigen receptor, T cells can be programmed to target cancer cells. However, initial studies have made it clear that the field will need to implement more complex levels of genetic regulation of engineered T cells to ensure both safety and efficacy. Here, we review the principles by which our knowledge of genetics and genome engineering will drive the next generation of adoptive T cell therapies.

Mesothelin-targeted CAR-T cell therapy for solid tumors

Introduction: Mesothelin (MSLN) is a tumor differentiation antigen normally restricted to the body's mesothelial surfaces, but significantly overexpressed in a broad range of solid tumors. For this reason, MSLN has emerged as an important target for the development of novel immunotherapies. This review focuses on anti-MSLN chimeric antigen receptor (CAR) T cell immunotherapy approaches.Areas covered: A brief overview of MSLN as a therapeutic target and existing anti-MSLN antibody-based drugs and vaccines is provided. A detailed account of anti-MSLN CAR-T cell approaches utilized in preclinical models is presented. Finally, a comprehensive summary of currently ongoing and completed anti-MSLN CAR-T cell clinical trials is discussed.Expert opinion: Initial trials using anti-MSLN CAR-T cells have been safe, but efficacy has been limited. Employing regional routes of delivery, introducing novel modifications leading to enhanced tumor infiltration and persistence, and improved safety profiles and combining anti-MSLN CAR-T cells with standard therapies, could render them more efficacious in the treatment of solid malignancies.

Genetic and epigenetic modification of human primary NK cells for enhanced antitumor activity

Cancer immunotherapy using genetically modified immune cells such as those expressing chimeric antigen receptors has shown dramatic outcomes in patients with refractory and relapsed malignancies. Natural killer (NK) cells as a member of the innate immune system, possessing both anticancer (cytotoxic) and proinflammatory (cytokine) responses to cancers and rare off-target toxicities have great potential for a wide range of cancer therapeutic settings. Therefore, improving NK cell antitumor activity through genetic modification is of high interest in the field of cancer immunotherapy. However, gene manipulation in primary NK cells has been challenging because of broad resistance to many genetic modification methods that work well in T cells. Here we review recent successful approaches for genetic and epigenetic modification of NK cells including epigenetic remodeling, transposons, mRNA-mediated gene delivery, lentiviruses, and CRISPR gene targeting.

Latest Advances for the Sleeping Beauty Transposon System: 23 Years of Insomnia but Prettier than Ever: Refinement and Recent Innovations of the Sleeping Beauty Transposon System Enabling Novel, Nonviral Genetic Engineering Applications

The Sleeping Beauty transposon system is a nonviral DNA transfer tool capable of efficiently mediating transposition-based, stable integration of DNA sequences of choice into eukaryotic genomes. Continuous refinements of the system, including the emergence of hyperactive transposase mutants and novel approaches in vectorology, greatly improve upon transposition efficiency rivaling viral-vector-based methods for stable gene insertion. Current developments, such as reversible transgenesis and proof-of-concept RNA-guided transposition, further expand on possible applications in the future. In addition, innate advantages such as lack of preferential integration into genes reduce insertional mutagenesis-related safety concerns while comparably low manufacturing costs enable widespread implementation. Accordingly, the system is recognized as a powerful and versatile tool for genetic engineering and is playing a central role in an ever-expanding number of gene and cell therapy clinical trials with the potential to become a key technology to meet the growing demand for advanced therapy medicinal products.

Engineering and Design of Chimeric Antigen Receptors

T cells engineered with chimeric antigen receptors (CARs) have emerged as a potent new class of therapeutics for cancer, based on their remarkable potency in blood cancers. Since the first clinical reports of their efficacy emerged 7 years ago, investigators have focused on the mechanisms and properties that make CARs effective or toxic, and their effects on T cell biology. Novel CAR designs coupled with improvements in gene transfer technology, incorporating advances in gene editing, have the potential to increase access to engineered cell therapies, as well as improve their potency in solid tumors.

Wide Awake and Ready to Move: 20 Years of Non-Viral Therapeutic Genome Engineering with the Sleeping Beauty Transposon System

Gene therapies will only become a widespread tool in the clinical treatment of human diseases with the advent of gene transfer vectors that integrate genetic information stably, safely, effectively, and economically. Two decades after the discovery of the Sleeping Beauty (SB) transposon, it has been transformed into a vector system that is fulfilling these requirements. SB may well overcome some of the limitations associated with viral gene transfer vectors and transient non-viral gene delivery approaches that are being used in the majority of ongoing clinical trials. The SB system has achieved a high level of stable gene transfer and sustained transgene expression in multiple primary human somatic cell types, representing crucial steps that may permit its clinical use in the near future. This article reviews the most important aspects of SB as a tool for gene therapy, including aspects of its vectorization and genomic integration. As an illustration, the clinical development of the SB system toward gene therapy of age-related macular degeneration and cancer immunotherapy is highlighted.

Biomanufacturing for clinically advanced cell therapies

The achievements of cell-based therapeutics have galvanized efforts to bring cell therapies to the market. To address the demands of the clinical and eventual commercial-scale production of cells, and with the increasing generation of large clinical datasets from chimeric antigen receptor T-cell immunotherapy, from transplants of engineered haematopoietic stem cells and from other promising cell therapies, an emphasis on biomanufacturing requirements becomes necessary. Robust infrastructure should address current limitations in cell harvesting, expansion, manipulation, purification, preservation and formulation, ultimately leading to successful therapy administration to patients at an acceptable cost. In this Review, we highlight case examples of cutting-edge bioprocessing technologies that improve biomanufacturing efficiency for cell therapies approaching clinical use.

Chimeric antigen receptor T cell (CAR-T) immunotherapy for solid tumors: lessons learned and strategies for moving forward

Recently, the US Food and Drug Administration (FDA) approved the first chimeric antigen receptor T cell (CAR-T) therapy for the treatment CD19-positive B cell acute lymphoblastic leukemia. While CAR-T has achieved remarkable success in the treatment of hematopoietic malignancies, whether it can benefit solid tumor patients to the same extent is still uncertain. Even though hundreds of clinical trials are undergoing exploring a variety of tumor-associated antigens (TAA), no such antigen with comparable properties like CD19 has yet been identified regarding solid tumors CAR-T immunotherapy. Inefficient T cell trafficking, immunosuppressive tumor microenvironment, suboptimal antigen recognition specificity, and lack of safety control are currently considered as the main obstacles in solid tumor CAR-T therapy. Here, we reviewed the solid tumor CAR-T clinical trials, emphasizing the studies with published results. We further discussed the challenges that CAR-T is facing for solid tumor treatment and proposed potential strategies to improve the efficacy of CAR-T as promising immunotherapy.

An Efficient In Vitro Transposition Method by a Transcriptionally Regulated Sleeping Beauty System Packaged into an Integration Defective Lentiviral Vector

The Sleeping Beauty (SB) transposon is a non-viral integrating system with proven efficacy for gene transfer and functional genomics. To optimize the SB transposon machinery, a transcriptionally regulated hyperactive transposase (SB100X) and T2-based transposon are employed. Typically, the transposase and transposon are provided transiently by plasmid transfection and SB100X expression is driven by a constitutive promoter. Here, we describe an efficient method to deliver the SB components to human cells that are resistant to several physical and chemical transfection methods, to control SB100X expression and stably integrate a gene of interest (GOI) through a "cut and paste" SB mechanism. The expression of hyperactive transposase is tightly controlled by the Tet-ON system, widely used to control gene expression since 1992. The gene of interest is flanked by inverted repeats (IR) of the T2 transposon. Both SB components are packaged in integration defective lentiviral vectors transiently produced in HEK293T cells. Human cells, either cell lines or primary cells from human tissue, are in vitro transiently transduced with viral vectors. Upon addition of doxycycline (dox, tetracycline analog) into the culture medium, a fine-tuning of transposase expression is measured and results in a long-lasting integration of the gene of interest in the genome of the treated cells. This method is efficient and applicable to the cell line (e.g., HeLa cells) and primary cells (e.g., human primary keratinocytes), and thus represents a valuable tool for genetic engineering and therapeutic gene transfer.

Preclinical and clinical advances in transposon-based gene therapy

Transposons derived from Sleeping Beauty (SB), piggyBac (PB), or Tol2 typically require cotransfection of transposon DNA with a transposase either as an expression plasmid or mRNA. Consequently, this results in genomic integration of the potentially therapeutic gene into chromosomes of the desired target cells, and thus conferring stable expression. Non-viral transfection methods are typically preferred to deliver the transposon components into the target cells. However, these methods do not match the efficacy typically attained with viral vectors and are sometimes associated with cellular toxicity evoked by the DNA itself. In recent years, the overall transposition efficacy has gradually increased by codon optimization of the transposase, generation of hyperactive transposases, and/or introduction of specific mutations in the transposon terminal repeats. Their versatility enabled the stable genetic engineering in many different primary cell types, including stem/progenitor cells and differentiated cell types. This prompted numerous preclinical proof-of-concept studies in disease models that demonstrated the potential of DNA transposons for ex vivo and in vivo gene therapy. One of the merits of transposon systems relates to their ability to deliver relatively large therapeutic transgenes that cannot readily be accommodated in viral vectors such as full-length dystrophin cDNA. These emerging insights paved the way toward the first transposon-based phase I/II clinical trials to treat hematologic cancer and other diseases. Though encouraging results were obtained, controlled pivotal clinical trials are needed to corroborate the efficacy and safety of transposon-based therapies.

Axicabtagene ciloleucel, a first-in-class CAR T cell therapy for aggressive NHL

The development of clinically functional chimeric antigen receptor (CAR) T cell therapy is the culmination of multiple advances over the last three decades. Axicabtagene ciloleucel (formerly KTE-C19) is an anti-CD19 CAR T cell therapy in development for patients with refractory diffuse large B cell lymphoma (DLBCL), including transformed follicular lymphoma (TFL) and primary mediastinal B cell lymphoma (PMBCL). Axicabtagene ciloleucel is manufactured from patients' own peripheral blood mononuclear cells (PBMC) during which T cells are engineered to express a CAR that redirects them to recognize CD19-expressing cells. Clinical trials have demonstrated the feasibility of manufacturing axicabtagene ciloleucel in a centralized facility for use in multicenter clinical trials and have demonstrated potent antitumor activity in patients with refractory DLBCL. Main acute toxicities are cytokine release syndrome and neurologic events. Axicabtagene ciloleucel holds promise for the treatment of patients with CD19-positive malignancies, including refractory DLBCL.

Gene Therapy with the Sleeping Beauty Transposon System

The widespread clinical implementation of gene therapy requires the ability to stably integrate genetic information through gene transfer vectors in a safe, effective, and economical manner. The latest generation of Sleeping Beauty (SB) transposon vectors fulfills these requirements, and may overcome limitations associated with viral gene transfer vectors and transient nonviral gene delivery approaches that are prevalent in ongoing clinical trials. The SB system enables high-level stable gene transfer and sustained transgene expression in multiple primary human somatic cell types, thereby representing a highly attractive gene transfer strategy for clinical use. Here, we review the most important aspects of using SB for gene therapy, including vectorization as well as genomic integration features. We also illustrate the path to successful clinical implementation by highlighting the application of chimeric antigen receptor (CAR)-modified T cells in cancer immunotherapy.

Going non-viral: the Sleeping Beauty transposon system breaks on through to the clinical side

Molecular medicine has entered a high-tech age that provides curative treatments of complex genetic diseases through genetically engineered cellular medicinal products. Their clinical implementation requires the ability to stably integrate genetic information through gene transfer vectors in a safe, effective and economically viable manner. The latest generation of Sleeping Beauty (SB) transposon vectors fulfills these requirements, and may overcome limitations associated with viral gene transfer vectors and transient non-viral gene delivery approaches that are prevalent in ongoing pre-clinical and translational research. The SB system enables high-level stable gene transfer and sustained transgene expression in multiple primary human somatic cell types, thereby representing a highly attractive gene transfer strategy for clinical use. Here we review several recent refinements of the system, including the development of optimized transposons and hyperactive SB variants, the vectorization of transposase and transposon as mRNA and DNA minicircles (MCs) to enhance performance and facilitate vector production, as well as a detailed understanding of SB's genomic integration and biosafety features. This review also provides a perspective on the regulatory framework for clinical trials of gene delivery with SB, and illustrates the path to successful clinical implementation by using, as examples, gene therapy for age-related macular degeneration (AMD) and the engineering of chimeric antigen receptor (CAR)-modified T cells in cancer immunotherapy.

Redirecting Specificity of T cells Using the Sleeping Beauty System to Express Chimeric Antigen Receptors by Mix-and-Matching of VL and VH Domains Targeting CD123+ Tumors

Adoptive immunotherapy infusing T cells with engineered specificity for CD19 expressed on B- cell malignancies is generating enthusiasm to extend this approach to other hematological malignancies, such as acute myelogenous leukemia (AML). CD123, or interleukin 3 receptor alpha, is overexpressed on most AML and some lymphoid malignancies, such as acute lymphocytic leukemia (ALL), and has been an effective target for T cells expressing chimeric antigen receptors (CARs). The prototypical CAR encodes a V_H and V_L from one monoclonal antibody (mAb), coupled to a transmembrane domain and one or more cytoplasmic signaling domains. Previous studies showed that treatment of an experimental AML model with CD123-specific CAR T cells was therapeutic, but at the cost of impaired myelopoiesis, highlighting the need for systems to define the antigen threshold for CAR recognition. Here, we show that CARs can be engineered using V_H and V_L chains derived from different CD123-specific mAbs to generate a panel of CAR⁺ T cells. While all CARs exhibited specificity to CD123, one V_H and V_L combination had reduced lysis of normal hematopoietic stem cells. This CAR’s in vivo anti-tumor activity was similar whether signaling occurred via chimeric CD28 or CD137, prolonging survival in both AML and ALL models. Co-expression of inducible caspase 9 eliminated CAR⁺ T cells. These data help support the use of CD123-specific CARs for treatment of CD123⁺ hematologic malignancies.

Enhanced CAR T-cell engineering using non-viral Sleeping Beauty transposition from minicircle vectors

Immunotherapy with T cell modified with gamma-retroviral or lentiviral (LV) vectors to express a chimeric antigen receptor (CAR) has shown remarkable efficacy in clinical trials. However, the potential for insertional mutagenesis and genotoxicity of viral vectors is a safety concern, and their cost and regulatory demands a roadblock for rapid and broad clinical translation. Here, we demonstrate that CAR T cells can be engineered through non-viral Sleeping Beauty (SB) transposition of CAR genes from minimalistic DNA vectors called minicircles (MCs). We analyzed genomic distribution of SB and LV integrations and show that a significantly higher proportion of MC-derived CAR transposons compared with LV integrants had occurred outside of highly expressed and cancer-related genes into genomic safe harbor loci that are not expected to cause mutagenesis or genotoxicity. CD19-CAR T cells engineered with our enhanced SB approach conferred potent reactivity in vitro and eradicated lymphoma in a xenograft model in vivo. Intriguingly, electroporation of SB MCs is substantially more effective and less toxic compared with conventional plasmids, and enables cost-effective rapid preparation of therapeutic CAR T-cell doses. This approach sets a new standard in advanced cellular and gene therapy and will accelerate and increase the availability of CAR T-cell therapy to treat hematologic malignancies.

Transcriptionally regulated and nontoxic delivery of the hyperactive Sleeping Beauty Transposase

The Sleeping Beauty (SB) transposase and, in particular, its hyperactive variant SB100X raises increasing interest for gene therapy application, including genome modification and, more recently, induced pluripotent stem cells (iPS) reprogramming. The documented cytotoxicity of the transposase, when constitutively expressed by an integrating retroviral vector (iRV), has been circumvented by the transient delivery of SB100X using retroviral mRNA transfer. In this study, we developed an alternative, safe, and efficient transposase delivery system based on a tetracycline-ON regulated expression cassette and the rtTA2(S)-M2 transactivator gene transiently delivered by integration-defective lentiviral vectors (IDLVs). Compared with iRV-mediated delivery, expression of tetracycline-induced SB100X delivered by an IDLV results in more efficient integration of a GFP transposon and reduced toxicity. Tightly regulated expression and reactivation of the transposase was achieved in HeLa cells as wells as in human primary keratinocytes. Based on these properties, the regulated transposase-IDLV vectors may represent a valuable tool for genetic engineering and therapeutic gene transfer.

Adoptive transfer of T cells transduced with a chimeric antigen receptor to treat relapsed or refractory acute leukemia: efficacy and feasibility of immunotherapy approaches

Treatment outcomes of acute leukemia (AL) have not improved over the past several decades and relapse rates remain high despite the availability of aggressive therapies. Conventional relapsed leukemia treatment includes second allogeneic hematopoietic stem cell transplantation (allo-HSCT) and donor lymphocyte infusion (DLI), which in most cases mediate, at best, a modest graft-versus-leukemia effect, although their clinical efficacy is still limited. Although allo-HSCT following myeloablative conditioning is a curative treatment option for younger patients with acute myeloid leukemia (AML) in a first complete remission (CR), allo-HSCT as a clinical treatment is usually limited because of treatment-related toxicity. The overall DLI remission rate is only 15%-42% and 2-year overall survival (OS) is approximately 15%-20%, with a high (40%-60%) incidence of DLI-related graft-versus-host disease (GVHD). Therefore, development of new, targeted treatment strategies for relapsed and refractory AL patients is ongoing. Adoptive transfer of T cells with genetically engineered chimeric antigen receptors (CARs) is an encouraging approach for treating hematological malignancies. These T cells are capable of selectively recognizing tumor-associated antigens and may overcome many limitations of conventional therapies, inducing remission in patients with chemotherapy-refractory or relapsed AL. In this review, we aimed to highlight the current understanding of this promising treatment modality, discussing its adverse effects and efficacy.

Sleeping Beauty Transposition

Sleeping Beauty (SB) is a synthetic transposon that was constructed based on sequences of transpositionally inactive elements isolated from fish genomes. SB is a Tc1/mariner superfamily transposon following a cut-and-paste transpositional reaction, during which the element-encoded transposase interacts with its binding sites in the terminal inverted repeats of the transposon, promotes the assembly of a synaptic complex, catalyzes excision of the element out of its donor site, and integrates the excised transposon into a new location in target DNA. SB transposition is dependent on cellular host factors. Transcriptional control of transposase expression is regulated by the HMG2L1 transcription factor. Synaptic complex assembly is promoted by the HMGB1 protein and regulated by chromatin structure. SB transposition is highly dependent on the nonhomologous end joining (NHEJ) pathway of double-strand DNA break repair that generates a transposon footprint at the excision site. Through its association with the Miz-1 transcription factor, the SB transposase downregulates cyclin D1 expression that results in a slowdown of the cell-cycle in the G1 phase, where NHEJ is preferentially active. Transposon integration occurs at TA dinucleotides in the target DNA, which are duplicated at the flanks of the integrated transposon. SB shows a random genome-wide insertion profile in mammalian cells when launched from episomal vectors and "local hopping" when launched from chromosomal donor sites. Some of the excised transposons undergo a self-destructive autointegration reaction, which can partially explain why longer elements transpose less efficiently. SB became an important molecular tool for transgenesis, insertional mutagenesis, and gene therapy.

Chimeric Antigen Receptors Modified T-Cells for Cancer Therapy

The genetic modification and characterization of T-cells with chimeric antigen receptors (CARs) allow functionally distinct T-cell subsets to recognize specific tumor cells. The incorporation of costimulatory molecules or cytokines can enable engineered T-cells to eliminate tumor cells. CARs are generated by fusing the antigen-binding region of a monoclonal antibody (mAb) or other ligand to membrane-spanning and intracellular-signaling domains. They have recently shown clinical benefit in patients treated with CD19-directed autologous T-cells. Recent successes suggest that the modification of T-cells with CARs could be a powerful approach for developing safe and effective cancer therapeutics. Here, we briefly review early studies, consider strategies to improve the therapeutic potential and safety, and discuss the challenges and future prospects for CAR T-cells in cancer therapy.

Minicircle-Based Engineering of Chimeric Antigen Receptor (CAR) T Cells

Plasmid DNA is being used as a pharmaceutical agent in vaccination, as well as a basic substance and starting material in gene and cell therapy, and viral vector production. Since the uncontrolled expression of backbone sequences present in such plasmids and the dissemination of antibiotic resistance genes may have profound detrimental effects, an important goal in vector development was to produce supercoiled DNA lacking bacterial backbone sequences: Minicircle (MC) DNA. The Sleeping Beauty (SB) transposon system is a non-viral gene delivery platform enabling a close-to-random profile of genomic integration. In combination, the MC platform greatly enhances SB transposition and transgene integration resulting in higher numbers of stably modified target cells. We have recently developed a strategy for MC-based SB transposition of chimeric antigen receptor (CAR) transgenes that enable improved transposition rates compared to conventional plasmids and rapid manufacturing of therapeutic CAR T cell doses (Monjezi et al. 2016). This advance enables manufacturing CAR T cells in a virus-free process that relies on SB-mediated transposition from MC DNA to accomplish gene-transfer. Advantages of this approach include a strong safety profile due to the nature of the MC itself and the genomic insertion pattern of MC-derived CAR transposons. In addition, stable transposition and high-level CAR transgene expression, as well as easy and reproducible handling, make MCs a preferred vector source for gene-transfer in advanced cellular and gene therapy. In this chapter, we will review our experience in MC-based CAR T cell engineering and discuss our recent advances in MC manufacturing to accelerate both pre-clinical and clinical implementation.