Successful Gene Therapy Research Articles

Spinal muscular atrophy - new therapies, new challenges.

Spinal muscular atrophy (SMA) is a progressive neurodegenerative disease with an autosomal recessive trait of inheritance and great variability of its clinical course - from the lethal congenital type (SMA0) to the adult-onset form (SMA4). The disease is associated with a deficiency of SMN protein, which is encoded by two genes SMN1 and SMN2. Clinical symptoms depend on mutations in the SMN1 gene. The number of copies of twin similar SMN2 gene, which produces small amounts of SMN protein, is the main phenotype modifier, which determines the clinical severity of the disease. Until recently, it was considered that spinal cord motoneurons undergo selective loss. Recent studies have shown the role of SMN protein in various cellular processes and the multisystemic character of SMA. The aim of the therapeutic strategies developed so far has been to increase the expression of SMN protein by modifying the splicing of SMN2 gene (intrathecally administered antisense oligonucleotide - nusinersen; orally available small molecules: RG7916 and LMI070 or SMN1 gene replacement therapy (AAV9-SMN). The first SMN2-directed antisense oligonucleotide (nusinersen) has demonstrated in clinical trials high efficiency, and it has now been registered. The best effects were obtained in patients who were introduced to the drug in the pre symptomatic period. Studies on other substances are ongoing. The great advances in SMA therapy and increased understanding of the pathogenesis of the disease raise hopes for changes to the natural history of the disease. Simultaneously, it increases awareness of the need to improve the standard of patient care and early diagnosis (newborn screening). Many questions (e.g. emerging phenotypes, combined therapies, systemic vs. intrathecal administration, long-term consequences, and complications of the therapy) will require further studies and observations.

Sphingomyelin-Based Nanosystems (SNs) for the Development of Anticancer miRNA Therapeutics.

Gene replacement therapy with oncosuppressor microRNAs (miRNAs) is a promising alternative to interfere with cancer progression. However, miRNAs are highly inefficient in a biological environment, hampering a successful translation to clinics. Nanotechnology can tackle this drawback by providing delivery systems able to efficiently deliver them to cancer cells. Thus, the objective of this work was to develop biocompatible nanosystems based on sphingomyelin (SM) for the intracellular delivery of miRNAs to colorectal cancer cells. We pursued two different approaches to select the most appropriate composition for miRNA delivery. On the one hand, we prepared sphingomyelin-based nanosystems (SNs) that incorporate the cationic lipid stearylamine (ST) to support the association of miRNA by the establishment of electrostatic interactions (SNs–ST). On the other hand, the cationic surfactant (DOTAP) was used to preform lipidic complexes with miRNA (Lpx), which were further encapsulated into SNs (SNs-Lpx). Restitution of miRNA145 levels after transfection with SNs-Lpx was related to the strongest anticancer effect in terms of tumor proliferation, colony forming, and migration capacity assays. Altogether, our results suggest that SNs have the potential for miRNA delivery to develop innovative anticancer therapies.

New treatments for spinal muscular atrophy

5‑q-associated spinal muscular atrophy (SMA) has so far been a causally untreatable disease, which leads to severe, progressive physical restrictions due to the loss of spinal motor neurons. However, the monogenetic cause of the relatively short coding "survival motor neuron" (SMN) 1gene sequence and the presence of almost identical gene copies, the SMN2 genes, offer favorable conditions for the development of new therapeutic approaches. While previously only supportive and palliative therapies could be used, new disease-modifying drugs are now available for the first time. Nusinersen, an antisense oligonucleotide (ASO), is the first drug that has received approval in Germany to treat SMA. Further therapeutic approaches such as the so-called "small molecules" or the gene replacement therapy are currently still being tested in clinical studies or are already waiting for approval by the European Medicines Agency (EMA). In this article, the most important disease-modifying drugs of SMA, the associated studies and their challenges are presented.

Deletion of M-Opsin Prevents M Cone Degeneration in a Mouse Model of Leber Congenital Amaurosis

Mutations in retinoid isomerase (RPE65) or lecithin-retinol acyltransferase (LRAT) disrupt 11-cis-retinal synthesis and cause Leber congenital amaurosis (LCA). Despite the success of recent RPE65 gene therapy, follow-up studies show that patients continue to experience photoreceptor degeneration and lose vision benefit over time. In Lrat-/- mouse model, mislocalized medium (M)-wavelength opsin was degraded, whereas mislocalized short (S)-wavelength opsin accumulated before the onset of cone degeneration. The mechanism for the foveal M/long-wavelength cone photoreceptor degeneration in LCA is unknown. By crossing Lrat-/- mice with a proteasome reporter mouse strain, this study showed that M-opsin-enriched dorsal cones in Lrat-/- mice exhibit proteasome stress because of the degradation of large amounts of M-opsin. Deletion of M-opsin relieves the proteasome stress and completely prevents M cone degeneration in Lrat-/-Opn1sw-/- mice (a pure M cone LCA model, Opn1sw encoding S-opsin) for at least 12 months. These results suggest that M-opsin degradation-associated proteasome stress plays a major role in M cone degeneration in Lrat-/- model. This finding may represent a general mechanism for M cone degeneration in multiple forms of cone degeneration because of M-opsin mislocalization and degradation. These results have important implications for the current gene therapy strategy for LCA that emphasizes the need for combinatorial therapies to both improve vision and slowphotoreceptor degeneration.

Efficient neuronal targeting and transfection using RVG and transferrin-conjugated liposomes

Effective transport of therapeutic nucleic acid to brain has been a challenge for the success of gene therapy for treating brain diseases. In this study, we proposed liposomal nanoparticles modified with brain targeting ligandsfor active brain targeting with enhanced BBB permeation and delivery of genes to brain. We targeted transferrin and nicotinic acetylcholine receptors by conjugating transferrin (Tf) and rabies virus glycoprotein (RVG) peptide to surface of liposomes. Liposomal formulations showed homogeneous particle size and ability to protect plasmid DNA against enzymatic degradation. These nanoparticles were internalized by brain endothelial cells, astrocytes and primary neuronal cells through energy-dependent endocytosis pathways. RVG-Tf coupled liposomes showed superior ability to transfect cells compared to liposomes without surface modification or single modification. Characterization of permeability through blood brain barrier (BBB) and functionality of designed liposomes were performed using an in vitro triple co-culture BBB model. Liposome-RVG-Tf efficiently translocated across in vitro BBB model and, consecutively, transfected primary neuronal cells. Notably, brain-targeted liposomes promoted in vivo BBB permeation. These studies suggest that modifications of liposomes with brain-targeting ligands are a promising strategy for delivery of genes to brain.

Azafaros targets lysosomal storage

The Dutch start-up Azafaros has raised about $28 million in series A financing to develop drugs for lysosomal storage diseases (LSDs), a group of rare metabolic diseases. Some LSDs are treated with enzyme replacement therapies, and many gene therapy firms are developing gene replacement therapies for LSDs. Azafaros is using small molecules discovered by scientists at Leiden University and Amsterdam University Medical Center. Called azasugars, the molecules block the harmful accumulation of glycolipids in LSDs.

Engineering adeno-associated virus vectors for gene therapy.

Adeno-associated virus (AAV) vector-mediated gene delivery was recently approved for the treatment of inherited blindness and spinal muscular atrophy, and long-term therapeutic effects have been achieved for other rare diseases, including haemophilia and Duchenne muscular dystrophy. However, current research indicates that the genetic modification of AAV vectors may further facilitate the success of AAV gene therapy. Vector engineering can increase AAV transduction efficiency (by optimizing the transgene cassette), vector tropism (using capsid engineering) and the ability of the capsid and transgene to avoid the host immune response (by genetically modifying these components), as well as optimize the large-scale production of AAV.

Surgical Techniques for the Subretinal Delivery of Pediatric Gene Therapy

Abstract No widely accepted surgical technique for subretinal gene replacement therapy delivery in pediatric patients exists. We present alternative approaches in patients with inherited retinal diseases that aim to improve surgical success and minimize complications.

The Need for SMN-Independent Treatments of Spinal Muscular Atrophy (SMA) to Complement SMN-Enhancing Drugs.

Spinal Muscular Atrophy (SMA) is monogenic motoneuron disease caused by low levels of the Survival of Motoneuron protein (SMN). Recently, two different drugs were approved for the treatment of the disease. The antisense oligonucleotide Nusinersen/Spinraza® and the gene replacement therapy Onasemnogene Abeparvovec/Zolgensma® both enhance SMN levels. These treatments result in impressive benefits for the patients. However, there is a significant number of non-responders and an intervention delay has a strong negative impact on the efficacy. Obviously, later stages of motoneuron degeneration cannot be reversed by SMN-restoration. Therefore, complementary, SMN-independent strategies are needed which are able to address such SMN-irreversible degenerative processes. Those are defined as pathological alterations which are not reversed by SMN-restoration for a given dose and intervention delay. It is crucial to tailor SMN-independent approaches to the novel clinical situation with SMN-restoring treatments. On the molecular level, such SMN-irreversible changes become manifest in altered signaling modules as described by molecular systems biology. Based on our current knowledge about altered signaling, we introduce a network approach for an informed decision for the most potent SMN-independent treatment targets. Finally, we present recommendations for the identification of novel treatments which can be combined with SMN-restoring drugs.

From Endocytosis to Nonendocytosis: The Emerging Era of Gene Delivery.

Over the past two decades, gene therapy, as a promising way to regulate or replace abnormal gene, has made impressive progress with numerous clinic trials. However, the success of gene therapy was hugely limited by its low translocation into cytoplasm. Therefore, technologies to efficiently protect and deliver therapeutic nucleic acids have been extensively investigated, but most of the delivery strategies involve endosomal entrapment, leading to low delivery efficiency. In this review, we discuss the latest advances in nonendocytosis-dependent strategies for delivering nucleic acids into cells. A highlight is provided on the cellular uptake systems facilitated by the endosome-Golgi-endoplasmic reticulum pathway, pH low insertion peptides, cell-penetrating peptides, scavenger receptor-mediated nonendocytosis, membrane fusion, and the emerged thiol-disulfide exchange. The mechanisms, pros, and cons of these systems are discussed. Finally, current challenges and future perspectives for the translation of nonendocytic gene delivery vectors, especially thiol-mediated cellular uptake, into clinical applications are discussed.

Preclinical efficacy and safety evaluation of scAAV9/CLN7 gene replacement therapy in rodents

Preclinical efficacy and safety evaluation of scAAV9/CLN7 gene replacement therapy in rodents

Twenty-Five Years of Spinal Muscular Atrophy Research: From Phenotype to Genotype to Therapy, and What Comes Next

Twenty-five years ago, the underlying genetic cause for one of the most common and devastating inherited diseases in humans, spinal muscular atrophy (SMA), was identified. Homozygous deletions or, rarely, subtle mutations of SMN1 cause SMA, and the copy number of the nearly identical copy gene SMN2 inversely correlates with disease severity. SMA has become a paradigm and a prime example of a monogenic neurological disorder that can be efficiently ameliorated or nearly cured by novel therapeutic strategies, such as antisense oligonucleotide or gene replacement therapy. These therapies enable infants to survive who might otherwise have died before the age of two and allow individuals who have never been able to sit or walk to do both. The major milestones on the road to these therapies were to understand the genetic cause and splice regulation of SMN genes, the disease's phenotype-genotype variability, the function of the protein and the main affected cellular pathways and tissues, the disease's pathophysiology through research on animal models, the windows of opportunity for efficient treatment, and how and when to treat patients most effectively.This review aims to bridge our knowledge from phenotype to genotype to therapy, not only highlighting the significant advances so far but also speculating about the future of SMA screening and treatment.

A new platform technology for next generation lysosomal enzyme replacement and potential gene therapy in the treatment of lysosomal diseases

A new platform technology for next generation lysosomal enzyme replacement and potential gene therapy in the treatment of lysosomal diseases

Pre-clinical safety and efficacy findings of AT845, a novel gene replacement therapy for Pompe disease targeting skeletal muscle and heart

Pre-clinical safety and efficacy findings of AT845, a novel gene replacement therapy for Pompe disease targeting skeletal muscle and heart

Fundoscopy-directed genetic testing to re-evaluate negative whole exome sequencing results

BackgroundWhole exome sequencing (WES) allows for an unbiased search of the genetic cause of a disease. Employing it as a first-tier genetic testing can be favored due to the associated lower incremental cost per diagnosis compared to when using it later in the diagnostic pathway. However, there are technical limitations of WES that can lead to inaccurate negative variant callings. Our study presents these limitations through a re-evaluation of negative WES results using subsequent tests primarily driven by fundoscopic findings. These tests included targeted gene testing, inherited retinal gene panels, whole genome sequencing (WGS), and array comparative genomic hybridization.ResultsSubsequent genetic testing guided by fundoscopy findings identified the following variant types causing retinitis pigmentosa that were not detected by WES: frameshift deletion and nonsense variants in the RPGR gene, 353-bp Alu repeat insertions in the MAK gene, and large exonic deletion variants in the EYS and PRPF31 genes. Deep intronic variants in the ABCA4 gene causing Stargardt disease and the GUCY2D gene causing Leber congenital amaurosis were also identified.ConclusionsNegative WES analyses inconsistent with the phenotype should raise clinical suspicion. Subsequent genetic testing may detect genetic variants missed by WES and can make patients eligible for gene replacement therapy and upcoming clinical trials. When phenotypic findings support a genetic etiology, negative WES results should be followed by targeted gene sequencing, array based approach or whole genome sequencing.

Haematopoietic Stem Cell Transplant Outcomes in Patients with Thalassemia Major from a Tertiary Care Center in South India.

<h3>Background</h3> Hematopoietic stem cell transplant (HSCT) is widely used as a gene replacement therapy in Thalassemia patients for decades. Survival probabilities after HSCT have increased considerably with advancements in graft versus host disease (GVHD) preventive strategies and conditioning regimens. Here we report our HSCT experience in patients with Thalassemia major, with different graft sources, in terms of transplant outcomes such as neutrophil and platelet engraftment, acute and chronic graft versus host disease (GVHD), thalassemia free survival and overall survival. <h3>Methods</h3> We analysed the data of 164 Thalassemia patients who have undergone HSCT between Jan-2012 to Jun-2019 at our centre. We evaluated the demographic and clinical characteristics of patients, graft source on the HSCT outcomes, such as engraftment, graft versus host disease, day-100 survival, thalassemia-free survival and overall survival. <h3>Results</h3> Out of 164 patients, 100 (61%) were males, the mean age was 9.47±4.41 (range, 1 -24) years. Peripheral blood stem cell (50%) and bone marrow (47%) are the respective graft sources with predominant matched sibling donor transplants (60.4%). One third of the patients received Fludarabine/Busulfan/Cyclophosphamide based conditioning regimen. Twenty-eight percent of the patients developed acute GVHD (grades I-IV) and 7.3% developed chronic GVHD. The average time to neutrophil engraftment was 14 (range, 8-24) days and platelet engraftment was 18 (range, 8-72) days. The average time to neutrophil engraftment and platelets engraftment did not significantly differ between the HLA-donor type (Figure 1). There were 26 deaths (15.9%) and 7 (4.3%) graft rejections during the follow-up. Infections are the major cause of deaths. The day 100 survival was 89%, the overall survival was 84% and the thalassemia free survival was 74.4%. <h3>Conclusion</h3> HSCT with various preparative regimens, GVHD preventive strategies, and varied graft sources is certainly a unique curative option for the Thalassemia major patients in the developing world. The survival after HSCT in Thalassemia patients are similar regardless of stem cell source, donor-HLA type (Figure 2) and GVHD (Figure 3). However, the incidence of GVHD is more with matched unrelated donors.

Identification of 13 novel USH2A mutations in Chinese retinitis pigmentosa and Usher syndrome patients by targeted next-generation sequencing.

Background: The USH2A gene encodes usherin, a basement membrane protein that is involved in the development and homeostasis of the inner ear and retina. Mutations in USH2A are linked to Usher syndrome type II (USH II) and non-syndromic retinitis pigmentosa (RP). Molecular diagnosis can provide insight into the pathogenesis of these diseases, facilitate clinical diagnosis, and identify individuals who can most benefit from gene or cell replacement therapy. Here, we report 21 pathogenic mutations in the USH2A gene identified in 11 Chinese families by using the targeted next-generation sequencing (NGS) technology.Methods: In all, 11 unrelated Chinese families were enrolled, and NGS was performed to identify mutations in the USH2A gene. Variant analysis, Sanger validation, and segregation tests were utilized to validate the disease-causing mutations in these families.Results: We identified 21 pathogenic mutations, of which 13, including 5 associated with non-syndromic RP and 8 with USH II, have not been previously reported. The novel variants segregated with disease phenotype in the affected families and were absent from the control subjects. In general, visual impairment and retinopathy were consistent between the USH II and non-syndromic RP patients with USH2A mutations.Conclusions: These findings provide a basis for investigating genotype–phenotype relationships in Chinese USH II and RP patients and for clarifying the pathophysiology and molecular mechanisms of the diseases associated with USH2A mutations.

Gene-terapia: Ikuspegi terapeutiko berria begietako gaitzen tratamenduan

Gene-terapia etorkizun handiko tresna bezala sortu da tratamendurik ez duten asaldurentzat. Azido nukleiko terapeutikoen administrazioan oinarritzen da gaixotasunak tratatzeko. Gene-terapia arrakastatsua izan dadin material genetikoaren askapen eraginkorra bermatu behar da itu-zeluletan. Geneen administrazio-sistemen artean, bektore biralak asko erabili dira ahalbidetzen duten transferentzia genikorako gaitasun onarengatik. Hala ere, horien arrisku nagusien ondorioz (immunogenizitatea eta mutagenesia), bektore ez-biralen diseinua sustatu da. Bektore ez-biralak seguruagoak dira eta ekoizpena errazagoa da, baina hauen muga nagusia transfekzio-eraginkortasun baxua da. Gene-terapiarako organo interesgarri bat begia da, eskuragarria eta aztertzeko erraza baita. Gainera, immunitate-sistematik babestuta dago. Gene-terapia entsegu kliniko guztien % 1,3 bakarrik tratatzen dituzte begietako gaitzak, baina etorkizun handia aurkeztu dute azken urteetan. Izan ere, 2018an Estatu Batuetan eta Europan gene-terapian oinarritutako begirako lehen medikamentuaren komertzializazioa onartu zen, Luxturna®, Sortzetiko Leberren Amaurosiaren tratamendurako. Berrikuspen honetan, begiko administrazio-bideak, gene-terapia estrategiak eta transferentzia geniko eraginkorrerako gainditu behar diren begiko mugak aurkezten dira. Halaber, gene-terapiaren bidez tratatzeko hautagai diren begietako gaitz ezberdinak ere biltzen dira. Gene-terapiaren inguruan egindako ahaleginei eta aurrerapenei esker, begietako gaitzak tratatzeko medikamentu berriak garatu dira. Horietako asko entsegu klinikoetan ebaluatzen ari dira oraindik, baina beste batzuk jada merkatura eta pazienteetara iritsi dira.

Health economic evaluation of gene replacement therapies: methodological issues and recommendations

ABSTRACT Objective: To provide recommendations for addressing previously identified key challenges in health economic evaluations of Gene Replacement Therapies (GRTs), including: 1) the assessment of clinical effectiveness; 2) the valuation of health outcomes; 3) the time horizon and extrapolation of effects beyond trial duration; 4) the estimation of costs; 5) the selection of appropriate discount rates; 6) the incorporation of broader elements of value; and 7) affordability. Methods: A literature review on economic evaluations of GRT was performed. Interviews were conducted with 8 European and US health economic experts with experience in evaluations of GRT. Targeted literature reviews were conducted to investigate further potential solutions to specific challenges. Recommendations: Experts agreed on factors to be considered to ensure the acceptability of historical cohorts by HTA bodies. Existing prospective registries or, if not available, retrospective registries, may be used to analyse different disease trajectories and inform extrapolations. The importance of expert opinion due to limited data was acknowledged. Expert opinion should be obtained using structured elicitation techniques. Broader elements of value, beyond health gains directly related to treatment, can be considered through the application of a factor to inflate the quality-adjusted life years (QALYs) or a higher cost-effectiveness threshold. Additionally, the use of cost-benefit analysis and saved young life equivalents (SAVE) were proposed as alternatives to QALYs for the valuations of outcomes of GRT as they can incorporate broader elements of value and avoid problems of eliciting utilities for paediatric diseases. Conclusions: While some of the limitations of economic evaluations of GRT are inherent to limited clinical data and lack of experience with these treatments, others may be addressed by methodological research to be conducted by health economists.

Cys-Flanked Cationic Peptides For Cell Delivery of the Herpes Simplex Virus Thymidine Kinase Gene for Suicide Gene Therapy of Uterine Leiomyoma

Uterine leiomyoma (UL) is the most common benign tumor in women of reproductive age. Gene therapy using suicidal genes appears to be a promising approach for UL treatment. One of key factors for success of gene therapy is the right choice of genetic construct carrier. A promising group of non-viral carriers for cell delivery of expression vectors is cationic Cys-flanked peptides which form tight complexes with DNA due to electrostatic interactions and the presence of interpeptide disulfide bonds. The paper reports a comparative study of the physico-chemical, toxic, and transfectional properties of the DNA-peptide complexes obtained by matrix polymerization or oxidative polycondensation of Cys-flanked peptides using the chain growth terminator 2-amino ethanethiol. We have demonstrated the therapeutic effect of the delivery of the pPTK-1 plasmid carrying the herpes simplex virus type 1 (HSV-1) thymidine kinase gene into PANC-1, and HEK-293T cell culture as well as into primary UL cells. It has been shown that the carriers obtained by oxidative polycondensation transform primary UL cells more efficiently than those produced by matrix polymerization. Treatment with ganciclovir resulted in the death of up to 40% of UL cells transfected with the pPTK-1 plasmid. The perspectives of use of the polyR6 carrier produced by oxidative polycondensation as a tool for the development of modular peptide carriers for the purposes of UL gene therapy were discussed.