Engineered T cell therapies

Alongside advancements in gene therapy for inherited immune disorders, the need for effective alternative therapeutic options for other conditions has resulted in an expansion in the field of research for T cell gene therapy. T cells are easily obtained and can be induced to divide robustly ex vivo, a characteristic that allows them to be highly permissible to viral vector-mediated introduction of transgenes. Pioneering clinical trials targeting cancers and infectious diseases have provided safety and feasibility data and important information about persistence of engineered cells in vivo. Here, we review clinical experiences with γ-retroviral and lentiviral vectors and consider the potential of integrating transposon-based vectors as well as specific genome editing with designer nucleases in engineered T cell therapies.

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Clonal Analyses of Retroviral Vector Integrations in ADA-SCID Patients Treated with Stem Cell Gene Therapy.

Blood ◽

10.1182/blood.v108.11.3249.3249 ◽

2006 ◽

Vol 108 (11) ◽

pp. 3249-3249

Author(s):

Barbara Cassani ◽

Grazia Andolfi ◽

Massimiliano Mirolo ◽

Luca Biasco ◽

Alessandra Recchia ◽

...

Keyword(s):

Gene Therapy ◽

T Cells ◽

T Cell ◽

Gene Transfer ◽

Human Genome ◽

Ex Vivo ◽

Cd34 Cells

Abstract Gene transfer into hematopoietic stem/progenitor cells (HSC) by gammaretroviral vectors is an effective treatment for patients affected by severe combined immunodeficiency (SCID) due to adenosine deaminase (ADA)-deficiency. Recent studied have indicated that gammaretroviral vectors integrate in a non-random fashion in their host genome, but there is still limited information on the distribution of retroviral insertion sites (RIS) in human long-term reconstituting HSC following therapeutic gene transfer. We performed a genome-wide analysis of RIS in transduced bone marrow-derived CD34+ cells before transplantation (in vitro) and in hematopoietic cell subsets (ex vivo) from five ADA-SCID patients treated with gene therapy combined to low-dose busulfan. Vector-genome junctions were cloned by inverse or linker-mediated PCR, sequenced, mapped onto the human genome, and compared to a library of randomly cloned human genome fragments or to the expected distribution for the NCBI annotation. Both in vitro (n=212) and ex vivo (n=496) RIS showed a non-random distribution, with strong preference for a 5-kb window around transcription start sites (23.6% and 28.8%, respectively) and for gene-dense regions. Integrations occurring inside the transcribed portion of a RefSeq genes were more represented in vitro than ex vivo (50.9 vs 41.3%), while RIS <30kb upstream from the start site were more frequent in the ex vivo sample (25.6% vs 19.4%). Among recurrently hit loci (n=50), LMO2 was the most represented, with one integration cloned from pre-infusion CD34+ cells and five from post-gene therapy samples (2 in granulocytes, 3 in T cells). Clone-specific Q-PCR showed no in vivo expansion of LMO2-carrying clones while LMO2 gene overexpression at the bulk level was excluded by RT-PCR. Gene expression profiling revealed a preference for integration into genes transcriptionally active in CD34+ cells at the time of transduction as well as genes expressed in T cells. Functional clustering analysis of genes hit by retroviral vectors in pre- and post-transplant cells showed no in vivo skewing towards genes controlling self-renewal or survival of HSC (i.e. cell cycle, transcription, signal transduction). Clonal analysis of long-term repopulating cells (>=6 months) revealed a high number of distinct RIS (range 42–121) in the T-cell compartment, in agreement with the complexity of the T-cell repertoire, while fewer RIS were retrieved from granulocytes. The presence of shared integrants among multiple lineages confirmed that the gene transfer protocol was adequate to allow stable engraftment of multipotent HSC. Taken together, our data show that transplantation of ADA-transduced HSC does not result in skewing or expansion of malignant clones in vivo, despite the occurrence of insertions near potentially oncogenic genomic sites. These results, combined to the relatively long-term follow-up of patients, indicate that retroviral-mediated gene transfer for ADA-SCID has a favorable safety profile.

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Depletion of Alloreactive T Cells after Haploidentical HSCT: Comparison of Outcomes for Ex Vivo Versus In Vivo Treatment Strategies

Blood ◽

10.1182/blood-2018-99-118857 ◽

2018 ◽

Vol 132 (Supplement 1) ◽

pp. 3474-3474

Author(s):

Steven Devine ◽

Stephan Mielke ◽

Eduardo Olavarria ◽

Bert Tuk ◽

Kees Meewisse ◽

...

Keyword(s):

Clinical Trials ◽

T Cells ◽

Single Dose ◽

T Cell ◽

Ex Vivo ◽

Chronic Gvhd ◽

Weighted Average ◽

Alloreactive T Cells ◽

Relapse Rates

Abstract Background: The use of haploidentical allogeneic hematopoietic stem cell transplantation (haplo-HSCT) has increased owing to therapeutic advances that have mitigated the main barriers such as high incidence of graft-versus-host disease (GVHD) and non-relapse mortality (NRM). This is primarily attributable to the elimination of alloreactive T cells in either the patient or the graft. Such T-cell depletion can be performed in vivo early after T-cell-replete haplo-HSCT using post-transplant cyclophosphamide (PTCy). Alternatively, T-cell-depleted haplo-HSCT can be supplemented with T-lymphocytes that are depleted ex vivo of their alloreactive component in the form of ATIR101 (Kiadis Pharma). Patient exposure to PTCy to eliminate donor alloreactive cells can be performed easily and at low cost but may cause patient toxicity and increase relapse rates, and it requires post-transplant immune suppression. Although ATIR101 requires cell manufacturing and is more expensive, it limits toxicity to the patient, enables haplo-HSCT without the use of immunosuppressants, and may reduce relapse rates. Both strategies are promising, but no attempt has yet been made to compare clinical results in similar patient populations to delineate key features of alloreactive T-cell depletion performed either ex vivo or in vivo. Methods: Data from published retrospective studies (single-site or registry data) were analyzed to assess clinical outcomes of haplo-HSCT plus PTCy. The 1-year outcomes from these studies were compared with results from a pooled analysis of 2 phase II clinical trials of a single dose of ATIR101 (N=37, all patients with AML/MDS/ALL [CR-AIR-007, CR-AIR-008]). Studies in which PTCy was used in patient populations with >50% AML/MDS/ALL were identified (Ciurea 2015, Piemontese 2017, Solomon 2012, Ciurea 2012, Devillier 2015, Di Stasi 2014, Esquirol 2016, Sugita 2015). The 1-year rates of relapse, relapse-related mortality (RRM), NRM, GVHD, and overall survival (OS) for the ATIR101 clinical trials were compared with the weighted average of these outcomes for the identified studies. OS is known to correlate with disease risk index (DRI; Armand 2014); therefore, publications reporting both OS and DRI (McCurdy 2017, Ciurea 2015, Devillier 2015, Sugita 2015) were identified to compare OS. Differences in DRI between PTCy and ATIR101 study populations were adjusted according to the relationship between DRI and OS. Finally, PTCy studies reporting GVHD-free and relapse-free survival (GRFS) were identified (Solh 2016, McCurdy 2017, Santoro 2017). There is a clinically relevant and statistically significant correlation between GRFS and DRI, so 1-year GRFS rates from the 2 studies reporting DRI status (Solh 2016, McCurdy 2017) were also normalized according to the DRI profile in the ATIR101 clinical trials to allow comparison. Results: The weighted average of PTCy (N=571) outcomes in populations with >50% AML/MDS/ALL vs ATIR101 patient outcomes were: 29% vs 8% for relapse; 18% vs 8% for RRM; 22% vs 33% for NRM; 5% vs 5% for acute GVHD grade III/IV; 24% vs 3% for chronic GVHD; and 60% vs 58% for OS. The OS in DRI-adjusted studies for PTCy (N=561) was similar to that in ATIR101 clinical trials (63% vs 58%, respectively). The GRFS-reporting studies included a total of 708 patients (Sohl 2016, N=128; McCurdy 2017, N=372; Santoro 2017, N=208); 1-year GRFS rates for PTCy in these studies were 33% (95% CI: 25-41), 45% (95% CI: 40-50), and 33% (average), respectively. In the 2 studies reporting DRI (N=500), the DRI profile was more favorable than in the ATIR101 studies and the 1-year GRFS rates normalized in line with the ATIR101 studies were reduced to 30% (Sohl 2016) and 40% (McCurdy 2017). In patients intended to receive a single dose of ATIR101 after haplo-HSCT, Kaplan-Meier estimate of 1-year GRFS was 53% (95% CI 39-72) (Table 1). Conclusion: This is not a head-to-head comparison, so data should be interpreted with caution. However, in these cross-study analyses, first insights into a potential advantage of ex vivo (ATIR101) over in vivo (PTCy) depletion of alloreactive T cells is suggested, including but not limited to rates of relapse, chronic GVHD, and GRFS. A large, phase III, randomized control trial is thus underway to assess the relative safety and efficacy of ATIR101 after T-cell-depleted haplo-HSCT versus PTCy after T-cell-replete haplo-HSCT (CR-AIR-009 HATCY; NCT02999854). Disclosures Devine: Kiadis Pharma: Consultancy. Mielke:Kiadis Pharma: Other: Travel grants, Research Funding. Tuk:Kiadis Pharma: Consultancy. Meewisse:Kiadis Pharma: Employment. Sandler:Kiadis Pharma: Employment. Roy:University of Montreal: Patents & Royalties: Author on patent; Kiadis Pharma: Other: Travel support; Hopital Maisonneuve Rosemont: Patents & Royalties: Author on patent.

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Gene Therapy Approaches

Qubahan Academic Journal ◽

10.48161/qaj.v1n1a35 ◽

2021 ◽

Vol 1 (1) ◽

pp. 52-56

Author(s):

Hogir Saadi

Keyword(s):

Gene Therapy ◽

Viral Vectors ◽

Nuclear Translocation ◽

Viral Vector ◽

Ex Vivo ◽

Genetic Material ◽

Target Tissue ◽

Human Beings ◽

Vector Systems

Gene therapy can be described broadly as the transfer of genetic material to control a disease or at least to enhance a patient's clinical status. The transformation of viruses into genetic shuttles is one of the core principles of gene therapy, which will introduce the gene of interest into the target tissue and cells. To do this, safe strategies have been invented, using many viral and non-viral vector delivery. Two major methods have emerged: modification in vivo and modification ex vivo. For gene therapeutic approaches which are focused on lifelong expression of the therapeutic gene, retrovirus, adenovirus, adeno-associated viruses are acceptable. Non-viral vectors are much less successful than viral vectors, but because of their low immune responses and their broad therapeutic DNA ability, they have advantages. The addition of viral functions such as receptor-mediated uptake and nuclear translocation of DNA may eventually lead to the development of an artificial virus in order to improve the role of non-viral vectors. For human use in genetic conditions, cancers and acquired illnesses, gene transfer techniques have been allowed. The ideal delivery vehicle has not been identified, although the accessible vector systems are capable of transporting genes in vivo into cells. Therefore, only with great caution can the present viral vectors be used in human beings and further progress in the production of vectors is required. Current progresses in our understanding of gene therapy approaches and their delivery technology, as well as the victors used to deliver therapeutic genes, are the primary goals of this review. For that reason, a literature search on PubMed and Google Scholar was carried out using different keywords.

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PD-L1 Immuno-Gene Therapy Under Cell Fate Control: Persistence of Cellular Delivery Vehicle and Transgene Expression.

Blood ◽

10.1182/blood.v114.22.3580.3580 ◽

2009 ◽

Vol 114 (22) ◽

pp. 3580-3580

Author(s):

Shoba Amarnath ◽

James CM Wang ◽

Paul R. Massey ◽

James L. Riley ◽

Bruce Levine ◽

...

Keyword(s):

Gene Therapy ◽

T Cells ◽

T Cell ◽

Cell Fate ◽

Adoptive Transfer ◽

Transgene Expression ◽

Ex Vivo ◽

Human T Cells ◽

Cell Fate Control

Abstract Abstract 3580 Poster Board III-517 Immune cell expression of programmed death ligand-1 (PD-L1) represents a particularly important molecular mechanism responsible for control of auto- and allo-immunity mediated by effector memory T cells expressing PD1 receptor. As such, we have reasoned that an immuno-gene therapy approach that enables T cell expression of PD-L1 will represent a novel method of immune regulation. Advantageous features of this proposed therapy include a capacity to: (1) enforce long-term, stable expression of PD-L1; (2) build-in an independent surface marker to allow specific transduced cell enrichment; (3) utilize cellular delivery vehicles comprised of highly functional T cells that persist in vivo after adoptive transfer; and (4) incorporate an enhanced cell fate control or ‘suicide’ gene to permit in vivo control of the immuno-gene therapy. Given these considerations, we developed a recombinant lentiviral vector (LV) incorporating an EF1-α promoter that first encodes the cDNA for a fusion protein consisting of human CD19 (truncated, non-signaling) combined with mutated human TMPK that efficiently activates AZT as a pro-drug (Sato et al; Mol Therapy, 2007); then, after an IRES element, the vector encodes full-length human PD-L1. LV was made after transfection of 293T cells and then concentrated and titered. Initial experiments used Jurkat cells to optimize virus infection and to confirm co-expression of CD19 and PD-L1 by flow cytometry. In previous work, we have demonstrated that ex vivo T cell expansion in rapamycin induces an anti-apoptotic phenotype that permits enhanced in vivo T cell persistence in murine models and human-into-mouse xenogeneic transplant models. As such, we established the goal of infecting primary human CD4+ T cells manufactured using ex vivo co-stimulation (anti-CD3, anti-CD28), Th1-type polarization (inclusion of IFN-α), and exposure to high-dose rapamycin (1 μM); using a 6-day culture system and subsequent anti-CD19 column purification, >90% of resultant transduced T cells expressed PD-L1. Next, we utilized a xenogeneic transplantation model (Rag2−/−γc−/− hosts) to assess in vivo persistence of the gene-modified T cells and transgene expression (10,000 T cells transferred i.v. into each host). In vivo experiment #1 demonstrated that recipients of gene-modified T cells had increased numbers of human T cells in the spleen that co-expressed CD19 and PD-L1 relative to recipients of non-transduced but identically expanded human T cells (harvested at day 5 after adoptive transfer; 38,000 cells/spleen vs. 1000 cells/spleen, p=0.02). Such in vivo harvested T cells were secondarily co-stimulated ex vivo and propagated for an additional 5 days: co-expression of CD19 and PD-L1 persisted in ∼ 50% of T cells harvested from the gene-modified T cell cohort, and T cell numbers were maintained ex vivo (yield of CD19+PD-L1+ cells, 28,600 vs. 1500; p=0.0001). In vivo experiment #2 confirmed and extended these results. At day 21 after adoptive transfer, recipients of gene-modified T cells had increased numbers of human T cells that co-expressed CD19 and PD-L1 relative to recipients of non-transduced but identically expanded human T cells in both the spleen (2800 cells/spleen vs. 390 cells/spleen, p=0.01; n=10 per cohort) and bone marrow (71,600 cells/marrow vs. 6500 cells/marrow, p=0.0001; n=10 per cohort). Such in vivo harvested T cells at day 21 after adoptive transfer were secondarily co-stimulated ex vivo and propagated for an additional 6 days: co-expression of CD19 and PD-L1 persisted in ∼ 50% of T cells harvested from the gene-modified T cell cohort, and T cell numbers were maintained ex vivo (yield of CD19+PD-L1+ cells harvested from spleen, 71,200 vs. 1800, p=0.0008; yield of CD19+PD-L1+ cells harvested from marrow, 226,000 vs. 1400, p=0.0001). Because the rapamycin-resistant T cell vehicle utilized in these experiments manifests an anti-apoptotic phenotype that confers long-term engraftment potential, it is likely that the demonstrated durability in transgene expression relates both to the efficiency of the LV method utilized and to a T cell pro-survival function. In conclusion, the LV-mediated transfer of this novel combination of CD19/TMPK fusion protein and PD-L1 results in stable transgene expression in primary human T cells in vitro and in vivo, thereby opening an avenue to assess PD-L1 mediated immuno-gene therapy under cell fate control. Disclosures: No relevant conflicts of interest to declare.

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Clinical Trials for Gene Therapy in Lysosomal Diseases With CNS Involvement

Frontiers in Molecular Biosciences ◽

10.3389/fmolb.2021.624988 ◽

2021 ◽

Vol 8 ◽

Author(s):

Caroline Sevin ◽

Kumaran Deiva

Keyword(s):

Gene Therapy ◽

Central Nervous System ◽

Clinical Trials ◽

Nervous System ◽

Ex Vivo ◽

Central Nervous System Involvement ◽

Large Animal ◽

Hematopoietic Stem ◽

The Brain

There are over 70 known lysosomal storage disorders (LSDs), most caused by mutations in genes encoding lysosomal hydrolases. Central nervous system involvement is a hallmark of the majority of LSDs and, if present, generally determines the prognosis of the disease. Nonetheless, brain disease is currently poorly targeted by available therapies, including systemic enzyme replacement therapy, mostly (but not only) due to the presence of the blood–brain barrier that restricts the access of orally or parenterally administered large molecules into the brain. Thus, one of the greatest and most exciting challenges over coming years will be to succeed in developing effective therapies for the treatment of central nervous system manifestations in LSDs. Over recent years, gene therapy (GT) has emerged as a promising therapeutic strategy for a variety of inherited neurodegenerative diseases. In LSDs, the ability of genetically corrected cells to cross-correct adjacent lysosomal enzyme-deficient cells in the brain after gene transfer might enhance the diffusion of the recombinant enzyme, making this group of diseases a strong candidate for such an approach. Both in vivo (using the administration of recombinant adeno-associated viral vectors) and ex vivo (auto-transplantation of lentiviral vector-modified hematopoietic stem cells-HSCs) strategies are feasible. Promising results have been obtained in an ever-increasing number of preclinical studies in rodents and large animal models of LSDs, and these give great hope of GT successfully correcting neurological defects, once translated to clinical practice. We are now at the stage of treating patients, and various clinical trials are underway, to assess the safety and efficacy of in vivo and ex vivo GT in several neuropathic LSDs. In this review, we summarize different approaches being developed and review the current clinical trials related to neuropathic LSDs, their results (if any), and their limitations. We will also discuss the pitfalls and the remaining challenges.

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Freezing Medium Containing 5% DMSO Enhances the Cell Viability and Recovery Rate After Cryopreservation of Regulatory T Cell Products ex vivo and in vivo

Frontiers in Cell and Developmental Biology ◽

10.3389/fcell.2021.750286 ◽

2021 ◽

Vol 9 ◽

Author(s):

Daniel Kaiser ◽

Natalie Maureen Otto ◽

Oliver McCallion ◽

Henrike Hoffmann ◽

Ghazaleh Zarrinrad ◽

...

Keyword(s):

T Cell ◽

Therapeutic Potential ◽

Ex Vivo ◽

Great Success ◽

Cell Therapies ◽

Cellular Expression ◽

Freezing Medium ◽

Dmso Concentration ◽

Shock Proteins

Cell therapies have significant therapeutic potential in diverse fields including regenerative medicine, transplantation tolerance, and autoimmunity. Within these fields, regulatory T cells (Treg) have been deployed to ameliorate aberrant immune responses with great success. However, translation of the cryopreservation strategies employed for other cell therapy products, such as effector T cell therapies, to Treg therapies has been challenging. The lack of an optimized cryopreservation strategy for Treg products presents a substantial obstacle to their broader application, particularly as administration of fresh cells limits the window available for sterility and functional assessment. In this study, we aimed to develop an optimized cryopreservation strategy for our CD4+CD25+Foxp3+ Treg clinical product. We investigate the effect of synthetic or organic cryoprotectants including different concentrations of DMSO on Treg recovery, viability, phenotype, cytokine production, suppressive capacity, and in vivo survival following GMP-compliant manufacture. We additionally assess the effect of adding the extracellular cryoprotectant polyethylene glycol (PEG), or priming cellular expression of heat shock proteins as strategies to improve viability. We find that cryopreservation in serum-free freezing medium supplemented with 10% human serum albumin and 5% DMSO facilitates improved Treg recovery and functionality and supports a reduced DMSO concentration in Treg cryopreservation protocols. This strategy may be easily incorporated into clinical manufacture protocols for future studies.

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Bone Marrow Cell Based Enzyme Replacement Prolongs Survival and Improves Disease Phenotypes In a Mouse Model Of Lethal Hypophosphatasia

Blood ◽

10.1182/blood.v122.21.2897.2897 ◽

2013 ◽

Vol 122 (21) ◽

pp. 2897-2897 ◽

Cited By ~ 1

Author(s):

Osamu Iijima ◽

Koichi Miyake ◽

Aki Nakamura ◽

Tsutomu Igarashi ◽

Chizu Kanokoda ◽

...

Keyword(s):

Gene Therapy ◽

Viral Vector ◽

Lentiviral Vector ◽

Ex Vivo ◽

Bone Mineralization ◽

Epileptic Seizures ◽

Enzyme Replacement ◽

Alp Activity ◽

Ex Vivo Gene Therapy

Abstract Hypophosphatasia (HPP) is an inherited skeletal disease caused by mutations of the ALPL gene that encodes tissue-nonspecific alkaline phosphatase (TNALP). TNALP is an ectoenzyme and plays an essential role in bone mineralization. The major symptoms of HPP are hypomineralization of systemic bones, respiratory insufficiency and epileptic seizures. Perinatal and infantile forms of HPP are often fatal. Since ALP functions on the exterior of the cells, enzyme replacement therapy (ERT) is a potential approach to treat HPP. Currently, Phase II/III clinical trials of ERT using a recombinant TNALP which linked deca-aspartate (D10) at the C terminus for bone targeting are ongoing in North America, Europe and Japan. The perinatal and infantile patients received the ERT showed apparent improvement of the symptoms. However, the ERT is highly invasive for the young patients because it requires repeated subcutaneous administration of large amounts of the enzyme every 3 times a week for long-term correction. As another approach to treat HPP, we have reported in vivo gene therapy for ALPL (Akp2) knock-out mice (HPP mice). The treated HPP mice were rescued by a single systemic injection of lentiviral vector or adeno-associated viral vector expressing bone targeted form of TNALP (TNALP-D10) during the neonatal or fetal period. Although untreated HPP mice developed apparent growth failure and died by around 20 days of age due to severe skeletal hypomineralization and epileptic seizure, the treated HPP mice were prolonged the survival and improved the physical activity. In the treated HPP mice, plasma ALP activity was kept higher than 1 U/ml (approximately 0.01 U/ml in untreated HPP mice and 0.1 U/ml in wild type (WT) mice) which gives therapeutic effects. However, disadvantages of in vivo gene therapy include the risk of germline gene transfer and induction of immune responses to the vectors or transgene products. To overcome these problems, we examined a feasibility of ex vivo gene therapy using hematopoietic stem cells (HSC) transduced by lentiviral vector expressing TNALP-D10. The potential advantages of this approach are lifelong expression of TNALP-D10 and prevention of risks of in vivo gene therapy. The lineage negative bone marrow cells containing HSC (Lin- BMC) were harvested from B6.CD45.1 mice (Ly5.1) and then enriched using Mouse Hematopoietic Progenitor (Stem) Cell Enrichment Set (BD bioscience). Lin- BMC was transduced with lentiviral vector expressing TNALP-D10 for 20 hrs at an moi of 50 with mSCF, mIL3 and rhIL6 on Retronectin coated plate. Recipient HPP mice (Ly5.2) on day 2 after birth were received a sub-lethal dose of total body irradiation (4Gy) 4hr prior to transplantation. Then, the transduced Lin- BMC (1 x 106 cells) was transplanted intravenously into the HPP mice through the temporal vein or jugular vein. The plasma ALP activity was rapidly elevated approximately 400 fold higher than untreated HPP mice (untreated: 0.014±0.004 units/ml (n=4) and treated: 5.39±2.29 units/ml (n=7), respectively) on 1 week after the transplantation and kept at this level during the observation period. Engraftment rate of Ly5.1 donor cells were sustained at approximately 30-40% with multilineage potential. The treated HPP mice were prolonged their survival over 3 months without epileptic seizures and the physical activities were improved. The histochemical ALP staining indicated TNALP-D10 was accumulated on the surface of trabecular and cortical bones of the treated HPP mice. The bone mineralization was significantly improved, but still not satisfactory compared with age matched WT mice. Contrary to our expectations, 2 of 9 HPP mice transplanted with non-transduced BMC also survived for 3 months. However, the plasma ALP activity was not elevated at all and the bone mineralization was incomplete compared with treated HPP mice. These results indicate that a single transplantation of genetically modified BMC at neonatal period is sufficient for long-term supply of TNALP-D10 and rescue of lethal HPP mice, even though hypomineralization was not completely recovered. Further optimization of viral vector and conditioning of transplantation is required to increase the treatment efficacy for HPP. However, neonatal ex vivo gene therapy using genetically modified BMC would be a possible and practical approach to treat HPP. Disclosures: Watanabe: Alexion Pharmaceuticals, Inc.: Membership on an entity’s Board of Directors or advisory committees.

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Preclinical and clinical advances in transposon-based gene therapy

Bioscience Reports ◽

10.1042/bsr20160614 ◽

2017 ◽

Vol 37 (6) ◽

Cited By ~ 24

Author(s):

Jaitip Tipanee ◽

Yoke Chin Chai ◽

Thierry VandenDriessche ◽

Marinee K. Chuah

Keyword(s):

Gene Therapy ◽

Clinical Trials ◽

Viral Vectors ◽

Ex Vivo ◽

Cell Types ◽

Sleeping Beauty ◽

Target Cells ◽

Hematologic Cancer ◽

Clinical Advances

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.

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