Long-term follow-up after gene therapy for canavan disease

Gene therapy in pediatrics - Clinical studies and approved drugs (as of 2023)

Gene therapy in pediatrics represents a cutting-edge therapeutic strategy for treating a range of genetic disorders that manifest in childhood. Gene therapy involves the modification or correction of a mutated gene or the introduction of a functional gene into a patient's cells. In general, it is implemented through two main modalities namely ex vivo gene therapy and in vivo gene therapy. Currently, a noteworthy array of gene therapy products has received valid market authorization, with several others in various stages of the approval process. Additionally, a multitude of clinical trials are actively underway, underscoring the dynamic progress within this field. Pediatric genetic disorders in the fields of hematology, oncology, vision and hearing loss, immunodeficiencies, neurological, and metabolic disorders are areas for gene therapy interventions. This review provides a comprehensive overview of the evolution and current progress of gene therapy-based treatments in the clinic for pediatric patients. It navigates the historical milestones of gene therapies, currently approved gene therapy products by the U.S. Food and Drug Administration (FDA) and/or European Medicines Agency (EMA) for children, and the promising future for genetic disorders. By providing a thorough compilation of approved gene therapy drugs and published results of completed or ongoing clinical trials, this review serves as a guide for pediatric clinicians to get a quick overview of the situation of clinical studies and approved gene therapy products as of 2023.

Durable transgene expression and efficient re-administration after rAAV2.5T-mediated fCFTRΔR gene delivery to adult ferret lungs

The dosing interval for effective recombinant adeno-associated virus (rAAV)-mediated gene therapy of cystic fibrosis lung disease remains unknown. Here, we assessed the durability of rAAV2.5T-fCFTRΔR-mediated transgene expression and neutralizing antibody (NAb) responses in lungs of adult wild-type ferrets. Within the first 3 months following rAAV2.5T-fCFTRΔR delivery to the lung, CFTRΔR transgene expression declined ∼5.6-fold and then remained stable to 5 months at ∼26% the level of endogenous CFTR. rAAV NAbs in the plasma and bronchoalveolar lavage fluid (BALF) peaked at 21 days, coinciding with peak ELISpot T cell responses to AAV capsid peptides, after which both responses declined and remained stable at 4-5 months post dosing. Administration of reporter vector rAAV2.5T-gLuc (gaussia luciferase) at 5 months following rAAV2.5T-fCFTRΔR dosing gave rise to similar levels of gLuc expression in the BALF as observed in age-matched reporter-only controls, demonstrating that residual BALF NAbs were functionally insignificant. Notably, the second vector administration led to a 2.6-fold greater ELISpot T cell response and ∼2.3-fold decline in fCFTRΔR mRNA and vector genomes derived from the initial rAAV2.5T-fCFTRΔR administration, suggesting selective destruction of transduced cells from the first vector dose. These findings provide insights into humoral and cellular immune response to rAAV that may be useful for optimizing gene therapy to the cystic fibrosis lung.

Targeting low levels of MIF expression as a potential therapeutic strategy for ALS

Mutations in SOD1 cause amyotrophic lateral sclerosis (ALS), a neurodegenerative disease characterized by motor neuron (MN) loss. We previously discovered that macrophage migration inhibitory factor (MIF), whose levels are extremely low in spinal MNs, inhibits mutant SOD1 misfolding and toxicity. In this study, we show that a single peripheral injection of adeno-associated virus (AAV) delivering MIF into adult SOD1G37R mice significantly improves their motor function, delays disease progression, and extends survival. Moreover, MIF treatment reduces neuroinflammation and misfolded SOD1 accumulation, rescues MNs, and corrects dysregulated pathways as observed by proteomics and transcriptomics. Furthermore, we reveal low MIF levels in human induced pluripotent stem cell-derived MNs from familial ALS patients with different genetic mutations, as well as in post mortem tissues of sporadic ALS patients. Our findings indicate that peripheral MIF administration may provide a potential therapeutic mechanism for modulating misfolded SOD1 in vivo and disease outcome in ALS patients.

Deep mutational scanning reveals a correlation between degradation and toxicity of thousands of aspartoacylase variants

Unstable proteins are prone to form non-native interactions with other proteins and thereby may become toxic. To mitigate this, destabilized proteins are targeted by the protein quality control network. Here we present systematic studies of the cytosolic aspartoacylase, ASPA, where variants are linked to Canavan disease, a lethal neurological disorder. We determine the abundance of 6152 of the 6260 ( ~ 98%) possible single amino acid substitutions and nonsense ASPA variants in human cells. Most low abundance variants are degraded through the ubiquitin-proteasome pathway and become toxic upon prolonged expression. The data correlates with predicted changes in thermodynamic stability, evolutionary conservation, and separate disease-linked variants from benign variants. Mapping of degradation signals (degrons) shows that these are often buried and the C-terminal region functions as a degron. The data can be used to interpret Canavan disease variants and provide insight into the relationship between protein stability, degradation and cell fitness.

Cellular and molecular mechanisms of aspartoacylase and its role in Canavan disease

Canavan disease is an autosomal recessive and lethal neurological disorder, characterized by the spongy degeneration of the white matter in the brain. The disease is caused by a deficiency of the cytosolic aspartoacylase (ASPA) enzyme, which catalyzes the hydrolysis of N-acetyl-aspartate (NAA), an abundant brain metabolite, into aspartate and acetate. On the physiological level, the mechanism of pathogenicity remains somewhat obscure, with multiple, not mutually exclusive, suggested hypotheses. At the molecular level, recent studies have shown that most disease linked ASPA gene variants lead to a structural destabilization and subsequent proteasomal degradation of the ASPA protein variants, and accordingly Canavan disease should in general be considered a protein misfolding disorder. Here, we comprehensively summarize the molecular and cell biology of ASPA, with a particular focus on disease-linked gene variants and the pathophysiology of Canavan disease. We highlight the importance of high-throughput technologies and computational prediction tools for making genotype-phenotype predictions as we await the results of ongoing trials with gene therapy for Canavan disease.

Adeno-associated virus as a delivery vector for gene therapy of human diseases

Adeno-associated virus (AAV) has emerged as a pivotal delivery tool in clinical gene therapy owing to its minimal pathogenicity and ability to establish long-term gene expression in different tissues. Recombinant AAV (rAAV) has been engineered for enhanced specificity and developed as a tool for treating various diseases. However, as rAAV is being more widely used as a therapy, the increased demand has created challenges for the existing manufacturing methods. Seven rAAV-based gene therapy products have received regulatory approval, but there continue to be concerns about safely using high-dose viral therapies in humans, including immune responses and adverse effects such as genotoxicity, hepatotoxicity, thrombotic microangiopathy, and neurotoxicity. In this review, we explore AAV biology with an emphasis on current vector engineering strategies and manufacturing technologies. We discuss how rAAVs are being employed in ongoing clinical trials for ocular, neurological, metabolic, hematological, neuromuscular, and cardiovascular diseases as well as cancers. We outline immune responses triggered by rAAV, address associated side effects, and discuss strategies to mitigate these reactions. We hope that discussing recent advancements and current challenges in the field will be a helpful guide for researchers and clinicians navigating the ever-evolving landscape of rAAV-based gene therapy.

NAAG synthetase deficiency has only low influence on pathogenesis in a Canavan disease mouse model

Canavan disease (CD) is a leukodystrophy caused by mutations in the N-acetylaspartate (NAA) hydrolase aspartoacylase (ASPA). Inability to degrade NAA and its accumulation in the brain results in spongiform myelin degeneration. NAA is mainly synthesized by neurons, where it is also a precursor of the neuropeptide N-acetylaspartylglutamate (NAAG). Hydrolysis of this peptide by glutamate carboxypeptidases is an additional source of extracellular NAA besides the instant neuronal release of NAA. This study examines to what extent NAA released from NAAG contributes to NAA accumulation and pathogenesis in the brain of Aspanur7/nur7 mutant mice, an established model of CD. Towards this aim, Aspanur7/nur7 mice with additional deficiencies in NAAG synthetase genes Rimklb and/or Rimkla were generated. Loss of myelin in Aspanur7/nur7 mice was not significantly affected by Rimkla and Rimklb deficiency and there was also no obvious change in the extent of brain vacuolation. Astrogliosis was slightly reduced in the forebrain of Rimkla and Rimklb double deficient Aspanur7/nur7 mice. However, only minor improvements at the behavioral level were found. The brain NAA accumulation in CD mice was, however, not significantly reduced in the absence of NAAG synthesis. In summary, there was only a weak tendency towards reduced pathogenic symptoms in Aspanur7/nur7 mice deficient in NAAG synthesis. Therefore, we conclude that NAAG metabolism has little influence on NAA accumulation in Aspanur7/nur7 mice and development of pathological symptoms in CD.

Leukodystrophy Imaging: Insights for Diagnostic Dilemmas

Leukodystrophies, a group of rare demyelinating disorders, mainly affect the CNS. Clinical presentation of different types of leukodystrophies can be nonspecific, and thus, imaging techniques like MRI can be used for a more definitive diagnosis. These diseases are characterized as cerebral lesions with characteristic demyelinating patterns which can be used as differentiating tools. In this review, we talk about these MRI study findings for each leukodystrophy, associated genetics, blood work that can help in differentiation, emerging diagnostics, and a follow-up imaging strategy. The leukodystrophies discussed in this paper include X-linked adrenoleukodystrophy, metachromatic leukodystrophy, Krabbe's disease, Pelizaeus-Merzbacher disease, Alexander's disease, Canavan disease, and Aicardi-Goutières Syndrome.

Delivery of Adeno-Associated Virus Vectors to the Central Nervous System for Correction of Single Gene Disorders

Genetic disorders of the central nervous system (CNS) comprise a significant portion of disability in both children and adults. Several preclinical animal models have shown effective adeno-associated virus (AAV) mediated gene transfer for either treatment or prevention of autosomal recessive genetic disorders. Owing to the intricacy of the human CNS and the blood-brain barrier, it is difficult to deliver genes, particularly since the expression of any given gene may be required in a particular CNS structure or cell type at a specific time during development. In this review, we analyzed delivery methods for AAV-mediated gene therapy in past and current clinical trials. The delivery routes analyzed were direct intraparenchymal (IP), intracerebroventricular (ICV), intra-cisterna magna (CM), lumbar intrathecal (IT), and intravenous (IV). The results demonstrated that the dose used in these routes varies dramatically. The average total doses used were calculated and were 1.03 × 1013 for IP, 5.00 × 1013 for ICV, 1.26 × 1014 for CM, and 3.14 × 1014 for IT delivery. The dose for IV delivery varies by patient weight and is 1.13 × 1015 IV for a 10 kg infant. Ultimately, the choice of intervention must weigh the risk of an invasive surgical procedure to the toxicity and immune response associated with a high dose vector.

Update on leukodystrophies and developing trials

Leukodystrophies are a heterogeneous group of rare genetic disorders primarily affecting the white matter of the central nervous system. These conditions can present a diagnostic challenge, requiring a comprehensive approach that combines clinical evaluation, neuroimaging, metabolic testing, and genetic testing. While MRI is the main tool for diagnosis, advances in molecular diagnostics, particularly whole-exome sequencing, have significantly improved the diagnostic yield. Timely and accurate diagnosis is crucial to guide symptomatic treatment and assess eligibility to participate in clinical trials. Despite no specific cure being available for most leukodystrophies, gene therapy is emerging as a potential treatment avenue, rapidly advancing the therapeutic prospects in leukodystrophies. This review will explore diagnostic and therapeutic strategies for leukodystrophies, with particular emphasis on new trials.

Vector-Mediated Delivery of Transgenes and RNA Interference-Based Gene Silencing Sequences to Astrocytes for Disease Management: Advances and Prospectives

Astrocytes are a type of important glial cell in the brain that serve crucial functions in regulating neuronal activity, facilitating communication between neurons, and keeping everything in balance. In this abstract, we explore current methods and future approaches for using vectors to precisely target astrocytes in the fight against various illnesses. In order to deliver therapeutic cargo selectively to astrocytes, researchers have made tremendous progress by using viral vectors such as adeno-associated viruses (AAVs) and lentiviruses. It has been established that engineered viral vectors are capable of either crossing the blood-brain barrier (BBB) or being delivered intranasally, which facilitates their entrance into the brain parenchyma. These vectors are able to contain transgenes that code for neuroprotective factors, synaptic modulators, or anti-inflammatory medicines, which pave the way for multiple approaches to disease intervention. Strategies based on RNA interference (RNAi) make vector-mediated astrocyte targeting much more likely to work. Small interfering RNAs (siRNAs) and short hairpin RNAs (shRNAs) are two types of RNA that can be made to silence disease-related genes in astrocytes. Vector-mediated delivery in conjunction with RNAi techniques provides a powerful toolkit for investigating the complex biological pathways that contribute to disease development. However, there are still a number of obstacles to overcome in order to perfect the specificity, safety, and duration of vector-mediated astrocyte targeting. In order to successfully translate research findings into clinical practise, it is essential to minimise off-target effects and the risk of immunogenicity. To demonstrate the therapeutic effectiveness of these strategies, rigorous preclinical investigation and validation are required.

Developing a human iPSC-derived three-dimensional myelin spheroid platform for modeling myelin diseases

Myelin defects cause a collection of myelin disorders in the brain. The lack of human models has limited us from better understanding pathological mechanisms of myelin diseases. While human induced pluripotent stem cell (hiPSC)-derived spheroids or organoids have been used to study brain development and disorders, it has been difficult to recapitulate mature myelination in these structures. Here, we have developed a method to generate three-dimensional (3D) myelin spheroids from hiPSCs in a robust and reproducible manner. Using this method, we generated myelin spheroids from patient iPSCs to model Canavan disease (CD), a demyelinating disorder. By using CD patient iPSC-derived myelin spheroids treated with N-acetyl-aspartate (NAA), we were able to recapitulate key pathological features of the disease and show that high-level NAA is sufficient to induce toxicity on myelin sheaths. Our study has established a 3D human cellular platform to model human myelin diseases for mechanistic studies and drug discovery.

Gene and Cellular Therapies for Leukodystrophies

Leukodystrophies are a heterogenous group of inherited, degenerative encephalopathies, that if left untreated, are often lethal at an early age. Although some of the leukodystrophies can be treated with allogeneic hematopoietic stem cell transplantation, not all patients have suitable donors, and new treatment strategies, such as gene therapy, are rapidly being developed. Recent developments in the field of gene therapy for severe combined immune deficiencies, Leber's amaurosis, epidermolysis bullosa, Duchenne's muscular dystrophy and spinal muscular atrophy, have paved the way for the treatment of leukodystrophies, revealing some of the pitfalls, but overall showing promising results. Gene therapy offers the possibility for overexpression of secretable enzymes that can be released and through uptake, allow cross-correction of affected cells. Here, we discuss some of the leukodystrophies that have demonstrated strong potential for gene therapy interventions, such as X-linked adrenoleukodystrophy (X-ALD), and metachromatic leukodystrophy (MLD), which have reached clinical application. We further discuss the advantages and disadvantages of ex vivo lentiviral hematopoietic stem cell gene therapy, an approach for targeting microglia-like cells or rendering cross-correction. In addition, we summarize ongoing developments in the field of in vivo administration of recombinant adeno-associated viral (rAAV) vectors, which can be used for direct targeting of affected cells, and other recently developed molecular technologies that may be applicable to treating leukodystrophies in the future.

AAV-based in vivo gene therapy for neurological disorders

Recent advancements in gene supplementation therapy are expanding the options for the treatment of neurological disorders. Among the available delivery vehicles, adeno-associated virus (AAV) is often the favoured vector. However, the results have been variable, with some trials dramatically altering the course of disease whereas others have shown negligible efficacy or even unforeseen toxicity. Unlike traditional drug development with small molecules, therapeutic profiles of AAV gene therapies are dependent on both the AAV capsid and the therapeutic transgene. In this rapidly evolving field, numerous clinical trials of gene supplementation for neurological disorders are ongoing. Knowledge is growing about factors that impact the translation of preclinical studies to humans, including the administration route, timing of treatment, immune responses and limitations of available model systems. The field is also developing potential solutions to mitigate adverse effects, including AAV capsid engineering and designs to regulate transgene expression. At the same time, preclinical research is addressing new frontiers of gene supplementation for neurological disorders, with a focus on mitochondrial and neurodevelopmental disorders. In this Review, we describe the current state of AAV-mediated neurological gene supplementation therapy, including critical factors for optimizing the safety and efficacy of treatments, as well as unmet needs in this field.

Methodology of a Natural History Study of a Rare Neurodevelopmental Disorder: Alternating Hemiplegia of Childhood as a Prototype Disease

Here, we describe the process of development of the methodology for an international multicenter natural history study of alternating hemiplegia of childhood as a prototype disease for rare neurodevelopmental disorders. We describe a systematic multistep approach in which we first identified the relevant questions about alternating hemiplegia of childhood natural history and expected challenges. Then, based on our experience with alternating hemiplegia of childhood and on pragmatic literature searches, we identified solutions to determine appropriate methods to address these questions. Specifically, these solutions included development and standardization of alternating hemiplegia of childhood-specific spell video-library, spell calendars, adoption of tailored methodologies for prospective measurement of nonparoxysmal and paroxysmal manifestations, unified data collection protocols, centralized data platform, adoption of specialized analysis methods including, among others, Cohen kappa, interclass correlation coefficient, linear mixed effects models, principal component, propensity score, and ambidirectional analyses. Similar approaches can, potentially, benefit in the study of other rare pediatric neurodevelopmental disorders.

Adeno-associated virus-mediated gene therapy in a patient with Canavan disease using dual routes of administration and immune modulation

Gene replacement therapy is a rational therapeutic strategy and clinical intervention for neurodegenerative disorders like Canavan disease, a leukodystrophy caused by biallelic mutations in the aspartoacylase (ASPA) gene. We aimed to investigate whether simultaneous intravenous (i.v.) and intracerebroventricular (i.c.v.) administration of rAAV9-CB6-ASPA provides a safe and effective therapeutic strategy in an open-label, individual-patient, expanded-access trial for Canavan disease. Immunomodulation was given prophylactically prior to adeno-associated virus (AAV) treatment to prevent an immune response to ASPA or the vector capsid. The patient served as his own control, and change from baseline was assessed by clinical pathology tests, vector genomes in the blood, antibodies against ASPA and AAV capsids, levels of cerebrospinal fluid (CSF) N-acetylaspartate (NAA), brain water content and morphology, clinical status, and motor function tests. Two years post treatment, the patient's white matter myelination had increased, motor function was improved, and he remained free of typical severe epilepsy. NAA level was reduced at 3 months and remained stable up to 4 years post treatment. Immunomodulation prior to AAV exposure enables repeat dosing and has prevented an anti-transgene immune response. Dual-route administration of gene therapy may improve treatment outcomes.

Novel MECP2 gene therapy is effective in a multicenter study using two mouse models of Rett syndrome and is safe in non-human primates

The AAV9 gene therapy vector presented in this study is safe in mice and non-human primates and highly efficacious without causing overexpression toxicity, a major challenge for clinical translation of Rett syndrome gene therapy vectors to date. Our team designed a new truncated methyl-CpG-binding protein 2 (MECP2) promoter allowing widespread expression of MECP2 in mice and non-human primates after a single injection into the cerebrospinal fluid without causing overexpression symptoms up to 18 months after injection. Additionally, this new vector is highly efficacious at lower doses compared with previous constructs as demonstrated in extensive efficacy studies performed by two independent laboratories in two different Rett syndrome mouse models carrying either a knockout or one of the most frequent human mutations of Mecp2. Overall, data from this multicenter study highlight the efficacy and safety of this gene therapy construct, making it a promising candidate for first-in-human studies to treat Rett syndrome.

Developing Hypoimmunogenic Human iPSC-Derived Oligodendrocyte Progenitor Cells as an Off-The-Shelf Cell Therapy for Myelin Disorders

Demyelinating disorders are among the most common and debilitating diseases in neurology. Canavan disease (CD) is a lethal demyelinating disease caused by mutation of the aspartoacylase (ASPA) gene, which leads to the accumulation of its substrate N-acetyl-l-aspartate (NAA), and consequently demyelination and vacuolation in the brain. In this study, hypoimmunogenic human induced pluripotent stem cell (iPSC)-derived oligodendrocyte progenitor cells (OPC) are developed from a healthy donor as an "off-the-shelf" cell therapy. Hypoimmunogenic iPSCs are generated through CRISPR/Cas9 editing of the human leukocyte antigen (HLA) molecules in healthy donor-derived iPSCs and differentiated into OPCs. The OPCs are engrafted into the brains of CD (nur7) mice and exhibit widespread distribution in the brain. The engrafted OPCs mature into oligodendrocytes that express the endogenous wildtype ASPA gene. Consequently, the transplanted mice exhibit elevated human ASPA expression and enzymatic activity and reduced NAA level in the brain. The transplanted OPCs are able to rescue major pathological features of CD, including defective myelination, extensive vacuolation, and motor function deficits. Moreover, the hypoimmunogenic OPCs exhibit low immunogenicity both in vitro and in vivo. The hypoimmunogenic OPCs can be used as "off-the-shelf" universal donor cells to treat various CD patients and many other demyelinating disorders, especially autoimmune demyelinating diseases, such as multiple sclerosis.

Virus-Based Biological Systems as Next-Generation Carriers for the Therapy of Central Nervous System Diseases

Central nervous system (CNS) diseases are currently a major challenge in medicine. One reason is the presence of the blood-brain barrier, which is a significant limitation for currently used medicinal substances that are characterized by a high molecular weight and a short half-life. Despite the application of nanotechnology, there is still the problem of targeting and the occurrence of systemic toxicity. Viral vectors and virus-like particles (VLPs) may provide a promising solution to these challenges. Their small size, biocompatibility, ability to carry medicinal substances, and specific targeting of neural cells make them useful in research when formulating a new generation of biological carriers. Additionally, the possibility of genetic modification has the potential for gene therapy. Among the most promising viral vectors are adeno-associated viruses, adenoviruses, and retroviruses. This is due to their natural tropism to neural cells, as well as the possibility of genetic and surface modification. Moreover, VLPs that are devoid of infectious genetic material in favor of increasing capacity are also leading the way for research on new drug delivery systems. The aim of this study is to review the most recent reports on the use of viral vectors and VLPs in the treatment of selected CNS diseases.

Amplifying gene expression with RNA-targeted therapeutics

Many diseases are caused by insufficient expression of mutated genes and would benefit from increased expression of the corresponding protein. However, in drug development, it has been historically easier to develop drugs with inhibitory or antagonistic effects. Protein replacement and gene therapy can achieve the goal of increased protein expression but have limitations. Recent discoveries of the extensive regulatory networks formed by non-coding RNAs offer alternative targets and strategies to amplify the production of a specific protein. In addition to RNA-targeting small molecules, new nucleic acid-based therapeutic modalities that allow highly specific modulation of RNA-based regulatory networks are being developed. Such approaches can directly target the stability of mRNAs or modulate non-coding RNA-mediated regulation of transcription and translation. This Review highlights emerging RNA-targeted therapeutics for gene activation, focusing on opportunities and challenges for translation to the clinic.

Aspartoacylase promotes the process of tumour development and is associated with immune infiltrates in gastric cancer

BACKGROUND

Aspartoacylase (ASPA) is a gene that plays an important role in the metabolic reprogramming of cancer. However, the clinical relevance of ASPA in gastric cancer (GC) has not been demonstrated.

METHODS

The link between ASPA and the clinical features of GC was determined using two public genomic databases. The multivariate Cox proportional hazard model and generalised linear regression model were applied to examine whether the ASPA level is associated with the prognosis and other pathological factors. In addition, the role of specific genes in the infiltration of immune cells in the setting of GC was investigated using a further immunological database. The expression level of various proteins was detected using a western blotting assay. Transwell and methyl thiazolyl tetrazolium tests were applied for the detection of cellular invasion and proliferation, with small hairpin ribonucleic acid used to knockdown ASPA.

RESULTS

According to the multivariate Cox regression results, the down-regulated ASPA expression is a distinct prognostic factor. Furthermore, ASPA has significant positive correlations with the infiltration of immune cells in GC lesions. Compared to the non-cancer tissues, the GC tissues had a significantly lower level of ASPA expression (p < 0.05). Using knockdown and overexpression techniques, it was demonstrated that ASPA affects the capacity of cell lines for GC to both proliferate and invade.

CONCLUSION

Overall, ASPA could promote the occurrence and development of GC and presents a promising predictive biomarker for the disease since it is favourably connected with immune infiltrates and negatively correlated with prognosis.

Biochemical Correction of GM2 Ganglioside Accumulation in AB-Variant GM2 Gangliosidosis

GM2 gangliosidosis is a group of genetic disorders that result in the accumulation of GM2 ganglioside (GM2) in brain cells, leading to progressive central nervous system (CNS) atrophy and premature death in patients. AB-variant GM2 gangliosidosis (ABGM2) arises from loss-of-function mutations in the GM2 activator protein (GM2AP), which is essential for the breakdown of GM2 in a key catabolic pathway required for CNS lipid homeostasis. In this study, we show that intrathecal delivery of self-complementary adeno-associated virus serotype-9 (scAAV9) harbouring a functional human GM2A transgene (scAAV9.hGM2A) can prevent GM2 accumulation in in GM2AP-deficient mice (Gm2a^-/- mice). Additionally, scAAV9.hGM2A efficiently distributes to all tested regions of the CNS within 14 weeks post-injection and remains detectable for the lifespan of these animals (up to 104 weeks). Remarkably, GM2AP expression from the transgene scales with increasing doses of scAAV9.hGM2A (0.5, 1.0 and 2.0 × 10¹¹ vector genomes (vg) per mouse), and this correlates with dose-dependent correction of GM2 accumulation in the brain. No severe adverse events were observed, and comorbidities in treated mice were comparable to those in disease-free cohorts. Lastly, all doses yielded corrective outcomes. These data indicate that scAAV9.hGM2A treatment is relatively non-toxic and tolerable, and biochemically corrects GM2 accumulation in the CNS-the main cause of morbidity and mortality in patients with ABGM2. Importantly, these results constitute proof-of-principle for treating ABGM2 with scAAV9.hGM2A by means of a single intrathecal administration and establish a foundation for future preclinical research.

Renewal of Oligodendrocyte Lineage Reverses Dysmyelination and CNS Neurodegeneration Through Corrected N-acetylaspartate Metabolism

Myelinating oligodendrocytes are essential for neuronal communication and homeostasis of the central nervous system (CNS). One of the most abundant molecules in the mammalian CNS is N-acetylaspartate (NAA), which is catabolized into L-aspartate and acetate by the enzyme aspartoacylase (ASPA) in oligodendrocytes. The resulting acetate moiety is thought to contribute to myelin lipid synthesis. In addition, affected NAA metabolism has been implicated in several neurological disorders, including leukodystrophies and demyelinating diseases such as multiple sclerosis. Genetic disruption of ASPA function causes Canavan disease, which is hallmarked by increased NAA levels, myelin and neuronal loss, large vacuole formation in the CNS, and early death in childhood. Although NAA's direct role in the CNS is inconclusive, in peripheral adipose tissue, NAA-derived acetate has been found to modify histones, a mechanism known to be involved in epigenetic regulation of cell differentiation. We hypothesize that a lack of cellular differentiation in the brain contributes to the disruption of myelination and neurodegeneration in diseases with altered NAA metabolism, such as Canavan disease. Our study demonstrates that loss of functional Aspa in mice disrupts myelination and shifts the transcriptional expression of neuronal and oligodendrocyte markers towards less differentiated stages in a spatiotemporal manner. Upon re-expression of ASPA, these myelination and neuronal lineage markers are either improved or normalized, suggesting that NAA breakdown by Aspa plays an essential role in the maturation of neurons and oligodendrocytes. Also, this effect of ASPA re-expression is blunted in old mice, potentially due to limited ability of neuronal, rather than oligodendrocyte, recovery.

AAV vectors applied to the treatment of CNS disorders: Clinical status and challenges

In recent years, adeno-associated virus (AAV) has become the most important vector for central nervous system (CNS) gene therapy. AAV has already shown promising results in the clinic, for several CNS diseases that cannot be treated with drugs, including neurodegenerative diseases, neuromuscular diseases, and lysosomal storage disorders. Currently, three of the four commercially available AAV-based drugs focus on neurological disorders, including Upstaza for aromatic l-amino acid decarboxylase deficiency, Luxturna for hereditary retinal dystrophy, and Zolgensma for spinal muscular atrophy. All these studies have provided paradigms for AAV-based therapeutic intervention platforms. AAV gene therapy, with its dual promise of targeting disease etiology and enabling 'long-term correction' of disease processes, has the advantages of immune privilege, high delivery efficiency, tissue specificity, and cell tropism in the CNS. Although AAV-based gene therapy has been shown to be effective in most CNS clinical trials, limitations have been observed in its clinical applications, which are often associated with side effects. In this review, we summarized the therapeutic progress, challenges, limitations, and solutions for AAV-based gene therapy in 14 types of CNS diseases. We focused on viral vector technologies, delivery routes, immunosuppression, and other relevant clinical factors. We also attempted to integrate several hurdles faced in clinical and preclinical studies with their solutions, to seek the best path forward for the application of AAV-based gene therapy in the context of CNS diseases. We hope that these thoughtful recommendations will contribute to the efficient translation of preclinical studies and wide application of clinical trials.

Systemic administration of novel engineered AAV capsids facilitates enhanced transgene expression in the macaque CNS

BACKGROUND

Adeno-associated virus (AAV) vectors are a promising vehicle for noninvasive gene delivery to the central nervous system via intravenous infusion. However, naturally occurring serotypes have a limited ability to transduce the brain, and translating engineered capsids from mice to nonhuman primates has proved challenging.

METHODS

In this study, we use an mRNA-based directed-evolution strategy in multiple strains of mice as well as a de novo selection in cynomolgus macaques to identify families of engineered vectors with increased potency in the brain and decreased tropism for the liver.

FINDINGS

We compare the transgene expression capabilities of several engineered vectors and show that while some of our novel macaque-derived variants significantly outperform AAV9 in transducing the macaque brain following systemic administration, mouse-derived variants-both those identified in this study and those reported by other groups-universally do not.

CONCLUSIONS

Together, the results of this work introduce a class of primate-derived engineered AAV capsids with increased therapeutic potential and highlight the critical need for using appropriate animal models to both identify and evaluate novel AAVs intended for delivery to the human central nervous system.

FUNDING

This work was funded primarily through an anonymous philanthropic gift to the P.C.S. lab at the Broad Institute of MIT and Harvard and by a grant from the Howard Hughes Medical Institute to P.C.S.

Viral-mediated gene therapy in pediatric neurological disorders

BACKGROUND

Due to the broad application of next-generation sequencing, the molecular diagnosis of genetic disorders in pediatric neurology is no longer an unachievable goal. However, treatments for neurological genetic disorders in children remain primarily symptomatic. On the other hand, with the continuous evolution of therapeutic viral vectors, gene therapy is becoming a clinical reality. From this perspective, we wrote this review to illustrate the current state regarding viral-mediated gene therapy in childhood neurological disorders.

DATA SOURCES

We searched databases, including PubMed and Google Scholar, using the keywords "adenovirus vector," "lentivirus vector," and "AAV" for gene therapy, and "immunoreaction induced by gene therapy vectors," "administration routes of gene therapy vectors," and "gene therapy" with "NCL," "SMA," "DMD," "congenital myopathy," "MPS" "leukodystrophy," or "pediatric metabolic disorders". We also screened the database of ClinicalTrials.gov using the keywords "gene therapy for children" and then filtered the results with the ones aimed at neurological disorders. The time range of the search procedure was from the inception of the databases to the present.

RESULTS

We presented the characteristics of commonly used viral vectors for gene therapy for pediatric neurological disorders and summarized their merits and drawbacks, the administration routes of each vector, the research progress, and the clinical application status of viral-mediated gene therapy on pediatric neurological disorders.

CONCLUSIONS

Viral-mediated gene therapy is on the brink of broad clinical application. Viral-mediated gene therapy will dramatically change the treatment pattern of childhood neurological disorders, and many children with incurable diseases will meet the dawn of a cure. Nevertheless, the vectors must be optimized for better safety and efficacy.

Dual-function AAV gene therapy reverses late-stage Canavan disease pathology in mice

The leukodystrophy Canavan disease is a fatal white matter disorder caused by loss-of-function mutations of the aspartoacylase-encoding ASPA gene. There are no effective treatments available and experimental gene therapy trials have failed to provide sufficient amelioration from Canavan disease symptoms. Preclinical studies suggest that Canavan disease-like pathology can be addressed by either ASPA gene replacement therapy or by lowering the expression of the N-acetyl-L-aspartate synthesizing enzyme NAT8L. Both approaches individually prevent or even reverse pathological aspects in Canavan disease mice. Here, we combined both strategies and assessed whether intracranial adeno-associated virus-mediated gene delivery to a Canavan disease mouse model at 12 weeks allows for reversal of existing pathology. This was enabled by a single vector dual-function approach. In vitro and in vivo biopotency assessment revealed significant knockdown of neuronal Nat8l paired with robust ectopic aspartoacylase expression. Following nomination of the most efficient cassette designs, we performed proof-of-concept studies in post-symptomatic Aspa-null mice. Late-stage gene therapy resulted in a decrease of brain vacuoles and long-term reversal of all pathological hallmarks, including loss of body weight, locomotor impairments, elevated N-acetyl-L-aspartate levels, astrogliosis, and demyelination. These data suggest feasibility of a dual-function vector combination therapy, directed at replacing aspartoacylase with concomitantly suppressing N-acetyl-L-aspartate production, which holds potential to permanently alleviate Canavan disease symptoms and expands the therapeutic window towards a treatment option for adult subjects.

A systematic review of adeno-associated virus gene therapies in neurology: the need for consistent safety monitoring of a promising treatment

Adeno-associated virus (AAV) gene therapies are generating much excitement in the rare disease field, particularly for previously untreatable neurological conditions. Efficacy has been claimed for several gene therapy products and the number of trials is rapidly increasing. However, reports of severe treatment-related adverse reactions are emerging, including death. There is still insufficient knowledge about their aetiology, prevention and treatment. We therefore undertook to systematically review publicly available data on AAV gene therapies in order to collate existing information on both safety and efficacy. Here, we review emerging efficacy reports of these novel therapies, many of which show promise. We also collate an increasing number of adverse reactions. Overwhelmingly, these results make a case for unified reporting of adverse events. This is likely to be critical for improving the safety of these promising treatments.

Routes of administration for adeno-associated viruses carrying gene therapies for brain diseases

Gene therapy is a powerful tool to treat various central nervous system (CNS) diseases ranging from monogenetic diseases to neurodegenerative disorders. Adeno-associated viruses (AAVs) have been widely used as the delivery vehicles for CNS gene therapies due to their safety, CNS tropism, and long-term therapeutic effect. However, several factors, including their ability to cross the blood-brain barrier, the efficiency of transduction, their immunotoxicity, loading capacity, the choice of serotype, and peripheral off-target effects should be carefully considered when designing an optimal AAV delivery strategy for a specific disease. In addition, distinct routes of administration may affect the efficiency and safety of AAV-delivered gene therapies. In this review, we summarize different administration routes of gene therapies delivered by AAVs to the brain in mice and rats. Updated knowledge regarding AAV-delivered gene therapies may facilitate the selection from various administration routes for specific disease models in future research.

Evolving therapies in neuronopathic LSDs: opportunities and challenges

Lysosomal storage disorders (LSD) are multisystemic progressive disorders caused by genetic mutations involving lysosomal function. While LSDs are individually considered rare diseases, the overall true prevalence of these disorders is likely higher than our current estimates. More than two third of the LSDs have associated neurodegeneration and the neurological phenotype often defines the course of the disease and treatment outcomes. Addressing the neurological involvement in LSDs has posed a significant challenge in the rapidly evolving field of therapies for these diseases. In this review, we summarize current approaches and clinical trials available for patients with neuronopathic lysosomal storage disorders, exploring the opportunities and challenges that have emerged with each of these.

Absence of lenadogene nolparvovec DNA in a brain tumor biopsy from a patient in the REVERSE clinical study, a case report

BACKGROUND

Leber Hereditary Optic Neuropathy (LHON) is a rare, maternally-inherited mitochondrial disease that primarily affects retinal ganglion cells (RGCs) and their axons in the optic nerve, leading to irreversible, bilateral severe vision loss. Lenadogene nolparvovec gene therapy was developed as a treatment for patients with vision loss from LHON caused by the most prevalent m.11778G > A mitochondrial DNA point mutation in the MT-ND4 gene. Lenadogene nolparvovec is a replication-defective recombinant adeno-associated virus vector 2 serotype 2 (AAV2/2), encoding the human wild-type MT-ND4 protein. Lenadogene nolparvovec was administered by intravitreal injection (IVT) in LHON patients harboring the m.11778G > A ND4 mutation in a clinical development program including one phase 1/2 study (REVEAL), three phase 3 pivotal studies (REVERSE, RESCUE, REFLECT), and one long-term follow-up study (RESTORE, the follow-up of REVERSE and RESCUE patients).

CASE PRESENTATION

A 67-year-old woman with MT-ND4 LHON, included in the REVERSE clinical study, received a unilateral IVT of lenadogene nolparvovec in the right eye and a sham injection in the left eye in May 2016, 11.4 months and 8.8 months after vision loss in her right and left eyes, respectively. The patient had a normal brain magnetic resonance imaging with contrast at the time of diagnosis of LHON. Two years after treatment administration, BCVA had improved in both eyes. The product was well tolerated with mild and resolutive anterior chamber inflammation in the treated eye. In May 2019, the patient was diagnosed with a right temporal lobe glioblastoma, IDH-wildtype, World Health Organization grade 4, based on histological analysis of a tumor excision. The brain tumor was assessed for the presence of vector DNA by using a sensitive validated qPCR assay targeting the ND4 sequence of the vector.

CONCLUSION

ND4 DNA was not detected (below 15.625 copies/μg of genomic DNA) in DNA extracted from the brain tumor, while a housekeeping gene DNA was detected at high levels. Taken together, this data shows the absence of detection of lenadogene nolparvovec in a brain tumor (glioblastoma) of a treated patient in the REVERSE clinical trial 3 years after gene therapy administration, supporting the long-term favorable safety of lenadogene nolparvovec.

Therapeutic development for Canavan disease using patient iPSCs introduced with the wild-type ASPA gene

Canavan disease (CD) is a devastating neurological disease that lacks effective therapy. Because CD is caused by mutations of the aspartoacylase (ASPA) gene, we introduced the wild-type (WT) ASPA gene into patient iPSCs through lentiviral transduction or CRISPR/Cas9-mediated gene editing. We then differentiated the WT ASPA-expressing patient iPSCs (ASPA-CD iPSCs) into NPCs and showed that the resultant ASPA-CD NPCs exhibited potent ASPA enzymatic activity. The ASPA-CD NPCs were able to survive in brains of transplanted CD mice. The engrafted ASPA-CD NPCs reconstituted ASPA activity in CD mouse brains, reduced the abnormally elevated level of NAA in both brain tissues and cerebrospinal fluid (CSF), and rescued hallmark pathological phenotypes of the disease, including spongy degeneration, myelination defects, and motor function impairment in transplanted CD mice. These genetically modified patient iPSC-derived NPCs represent a promising cell therapy candidate for CD, a disease that has neither a cure nor a standard treatment.

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The wild-type ASPA gene was introduced into CD patient iPSCs to make ASPA-CD iPSCs

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ASPA-CD iPSCs were differentiated into ASPA-CD NPCs with potent ASPA activity

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Engrafted ASPA-CD NPCs could rescue major disease phenotypes in CD mice

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CSF NAA level can be used as a biomarker to monitor the treatment outcome for CD

Gene therapy for neuromuscular disorders: prospects and ethics

Most childhood neuromuscular disorders are caused by mutations causing abnormal expression or regulation of single genes or genetic pathways. The potential for gene therapy, gene editing and genetic therapies to ameliorate the course of these conditions is extraordinarily exciting, but there are significant challenges associated with their use, particularly with respect to safety, efficacy, cost and equity. Engagement with these novel technologies mandates careful assessment of the benefits and burdens of treatment for the patient, their family and their society. The examples provided by spinal muscular atrophy and Duchenne muscular dystrophy illustrate the potential value and challenges of gene and genetic therapies for paediatric neurological conditions. The cost and complexity of administration of these agents is a challenge for all countries. Jurisdictional variations in availability of newborn screening, genetic diagnostics, drug approval and reimbursement pathways, treatment and rehabilitation will affect equity of access, nationally and internationally. These challenges will best be addressed by collaboration by governments, pharma, clinicians and patient groups to establish frameworks for safe and cost-effective use of these exciting new therapies.

Practical Genetics for the Neuroradiologist: Adding Value in Neurogenetic Disease

Genetic discoveries have transformed our understanding of many neurologic diseases. Identification of specific causal pathogenic variants has improved understanding of pathophysiology and enabled replacement of many confusing eponyms and acronyms with more meaningful and clinically relevant genetics-based terminology. In this era of rapid scientific advancement, multidisciplinary collaboration among pediatricians, neurologists, geneticists, radiologists, and other members of the health care team is increasingly important in the care of patients with genetic neurologic diseases. Radiologists familiar with neurogenetic disease add value by (1) recognizing constellations of characteristic imaging findings that are associated with a genetic disease before one is clinically suspected; (2) predicting the most likely genotypes for a given imaging phenotype in clinically suspected genetic disease; and (3) providing detailed and accurate descriptions of the imaging phenotype in challenging cases with unknown or uncertain genotypes. This review aims to increase awareness and understanding of pathogenic variants relating to neurologic disease by (1) briefly reviewing foundational knowledge of chromosomes, inheritance patterns, and mutagenesis; (2) providing concrete examples of and detailed information about specific neurologic diseases resulting from pathogenic variants; and (3) highlighting clinical and imaging features that are of greatest relevance for the radiologist.

Gene Therapy for Rare Neurological Disorders

There are over 7 000 diseases that are individually rare, but collectively affect missions of people worldwide. They are very commonly neurologic single-gene disorders. Recent advances in recombinant adeno-associated virus (rAAV) vectors have enabled breakthroughs, including FDA-approved gene therapies for Inherited Retinal Dystrophy due to RPE65 mutation and spinal muscular atrophy. A range of other gene therapies for rare neurologic diseases are at various stages of development. Future development of gene editing technologies promises further to broaden the potential for more patients with these disorders to benefit from innovative therapies.

Seven-year follow-up of durability and safety of AAV CNS gene therapy for a lysosomal storage disorder in a large animal

Delivery of adeno-associated viral vectors (AAVs) to cerebrospinal fluid (CSF) has emerged as a promising approach to achieve widespread transduction of the central nervous system (CNS) and peripheral nervous system (PNS), with direct applicability to the treatment of a wide range of neurological diseases, particularly lysosomal storage diseases. Although studies in small animal models have provided proof of concept and experiments in large animals demonstrated feasibility in bigger brains, there is not much information on long-term safety or durability of the effect. Here, we report a 7-year study in healthy beagle dogs after intra-CSF delivery of a single, clinically relevant dose (2 × 10¹³ vg/dog) of AAV9 vectors carrying the canine sulfamidase, the enzyme deficient in mucopolysaccharidosis type IIIA. Periodic monitoring of CSF and blood, clinical and neurological evaluations, and magnetic resonance and ultrasound imaging of target organs demonstrated no toxicity related to treatment. AAV9-mediated gene transfer resulted in detection of sulfamidase activity in CSF throughout the study. Analysis at tissue level showed widespread sulfamidase expression and activity in the absence of histological findings in any region of encephalon, spinal cord, or dorsal root ganglia. Altogether, these results provide proof of durability of expression and long-term safety for intra-CSF delivery of AAV-based gene transfer vectors encoding therapeutic proteins to the CNS.

Current and Future Prospects for Gene Therapy for Rare Genetic Diseases Affecting the Brain and Spinal Cord

In recent years, gene therapy has been raising hopes toward viable treatment strategies for rare genetic diseases for which there has been almost exclusively supportive treatment. We here review this progress at the pre-clinical and clinical trial levels as well as market approvals within diseases that specifically affect the brain and spinal cord, including degenerative, developmental, lysosomal storage, and metabolic disorders. The field reached an unprecedented milestone when Zolgensma® (onasemnogene abeparvovec) was approved by the FDA and EMA for in vivo adeno-associated virus-mediated gene replacement therapy for spinal muscular atrophy. Shortly after EMA approved Libmeldy®, an ex vivo gene therapy with lentivirus vector-transduced autologous CD34-positive stem cells, for treatment of metachromatic leukodystrophy. These successes could be the first of many more new gene therapies in development that mostly target loss-of-function mutation diseases with gene replacement (e.g., Batten disease, mucopolysaccharidoses, gangliosidoses) or, less frequently, gain-of-toxic-function mutation diseases by gene therapeutic silencing of pathologic genes (e.g., amyotrophic lateral sclerosis, Huntington's disease). In addition, the use of genome editing as a gene therapy is being explored for some diseases, but this has so far only reached clinical testing in the treatment of mucopolysaccharidoses. Based on the large number of planned, ongoing, and completed clinical trials for rare genetic central nervous system diseases, it can be expected that several novel gene therapies will be approved and become available within the near future. Essential for this to happen is the in depth characterization of short- and long-term effects, safety aspects, and pharmacodynamics of the applied gene therapy platforms.

Clinical Trials for Gene Therapy in Lysosomal Diseases With CNS Involvement

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.

Reduced Immunogenicity of Intraparenchymal Delivery of Adeno-Associated Virus Serotype 2 Vectors: Brief Overview

Pre existing immunity to adeno-associated virus (AAV) poses a concern in AAV vector–mediated gene therapy. Localized administration of low doses of carefully chosen AAV serotypes can mitigate the risk of an immune response. This article will illustrate the low risk of immune response to AAV serotype 2 vector–mediated gene therapy to the brain with support from clinical trial data in aromatic L-amino acid decarboxylase deficiency and Parkinson disease.

Ablating the Transporter Sodium-Dependent Dicarboxylate Transporter 3 Prevents Leukodystrophy in Canavan Disease Mice

Canavan disease is caused by ASPA mutations that diminish brain aspartoacylase activity, and it is characterized by excessive brain storage of the aspartoacylase substrate, N-acetyl-l-aspartate (NAA), and by astroglial and intramyelinic vacuolation. Astroglia and the arachnoid mater express sodium-dependent dicarboxylate transporter (NaDC3), encoded by SLC13A3, a sodium-coupled transporter for NAA and other dicarboxylates. Constitutive Slc13a3 deletion in aspartoacylase-deficient Canavan disease mice prevents brain NAA overaccumulation, ataxia, and brain vacuolation. ANN NEUROL 2021;90:845-850.

Viral gene therapy for paediatric neurological diseases: progress to clinical reality

In the era of genomic medicine, diagnoses of rare paediatric neurological diseases are increasing. Many are untreatable and life-limiting, leading to an exceptional increase in gene therapy development. It is estimated that 20 gene therapy products will have received approval from the US Food and Drug Administration by 2025. With viral gene therapy considered a potential single-dose cure for patients with spinal muscular atrophy type 1 as one example, and contemporaneously tragically resulting in the deaths of three male children with X-linked myotubular myopathy receiving high-dose gene therapy in 2020, what is the current state of gene therapy? What is behind the decades of hype around viral gene therapy and is it high impact, but high risk? In this review, we outline principles of viral gene therapy development and summarize the most recent clinical evidence for the therapeutic effect of gene therapy in paediatric neurological diseases. We discuss adeno-associated virus and lentiviral vectors, antisense oligonucleotides, emerging genetic editing approaches, and current limitations that the field still faces. What this paper adds Viral gene therapy development and clinically used transgenes, regulatory elements, capsids, dosage, and delivery routes are summarized. Viral gene therapy for 18 childhood neurological disorders involving over 600 children in 40 clinical trials are reviewed.

A comprehensive model based on temporal dynamics of peripheral T cell repertoire for predicting post-treatment distant metastasis of nasopharyngeal carcinoma

Many nasopharyngeal carcinoma (NPC) patients develop distant metastases after treatment, leading to poor outcomes. To date, there are no peripheral biomarkers suitable for all NPC patients to predict distant metastasis. Hence, we purposed to develop a noninvasive comprehensive model for predicting post-treatment distant metastasis of all NPC. Since T-cell receptor β chain (TCRB) repertoire has achieved prognostic prediction in many cancers, the clinical characteristics and parameters of TCRB repertoire of 71 cases of peripheral blood samples (pairwise pre-treatment and post-treatment samples from 40 NPC patients who without (nM, n = 21) or with (M, n = 19) post-treatment distant metastasis) were collected. The least absolute shrinkage and selection operator algorithm was used to construct a distant metastasis prediction model. In terms of TCRB repertoire parameters, the diversity of TCRB repertoire was significantly decreased in M group after treatment but not in nM group. Ascending TCRB diversity and higher similarity between pre- and post-treatment samples showed better distant metastasis-free survival (DMFS). The similarity still had robust DMFS prediction in patients with reduced TCRB diversity. More importantly, the 5-factor comprehensive model consisting of basic clinical characteristics and TCRB repertoire indices showed a higher prognostic accuracy than any one individual factor in DMFS predicting. In conclusion, treatment had different effects on the composition of TCRB repertoire in patients without and with post-treatment distant metastasis. The dynamics of TCRB diversity, the similarity of TCRB repertoires, and combinations of these factors with basic clinical characteristics could serve as noninvasive DMFS predictors for all NPC patients.

Emerging Concepts in Vector Development for Glial Gene Therapy: Implications for Leukodystrophies

Central Nervous System (CNS) homeostasis and function rely on intercellular synchronization of metabolic pathways. Developmental and neurochemical imbalances arising from mutations are frequently associated with devastating and often intractable neurological dysfunction. In the absence of pharmacological treatment options, but with knowledge of the genetic cause underlying the pathophysiology, gene therapy holds promise for disease control. Consideration of leukodystrophies provide a case in point; we review cell type – specific expression pattern of the disease – causing genes and reflect on genetic and cellular treatment approaches including ex vivo hematopoietic stem cell gene therapies and in vivo approaches using adeno-associated virus (AAV) vectors. We link recent advances in vectorology to glial targeting directed towards gene therapies for specific leukodystrophies and related developmental or neurometabolic disorders affecting the CNS white matter and frame strategies for therapy development in future.

Adeno-Associated Viral Vectors as Versatile Tools for Parkinson's Research, Both for Disease Modeling Purposes and for Therapeutic Uses

It is without any doubt that precision medicine therapeutic strategies targeting neurodegenerative disorders are currently witnessing the spectacular rise of newly designed approaches based on the use of viral vectors as Trojan horses for the controlled release of a given genetic payload. Among the different types of viral vectors, adeno-associated viruses (AAVs) rank as the ones most commonly used for the purposes of either disease modeling or for therapeutic strategies. Here, we reviewed the current literature dealing with the use of AAVs within the field of Parkinson’s disease with the aim to provide neuroscientists with the advice and background required when facing a choice on which AAV might be best suited for addressing a given experimental challenge. Accordingly, here we will be summarizing some insights on different AAV serotypes, and which would be the most appropriate AAV delivery route. Next, the use of AAVs for modeling synucleinopathies is highlighted, providing potential readers with a landscape view of ongoing pre-clinical and clinical initiatives pushing forward AAV-based therapeutic approaches for Parkinson’s disease and related synucleinopathies.

Alternating hemiplegia of childhood: evolution over time and mouse model corroboration

Alternating hemiplegia of childhood is a rare neurodevelopmental disorder caused by ATP1A3 mutations. Some evidence for disease progression exists, but there are few systematic analyses. Here, we evaluate alternating hemiplegia of childhood progression in humans and in the D801N knock-in alternating hemiplegia of childhood mouse, Mashlool, model. This study performed an ambidirectional (prospective and retrospective data) analysis of an alternating hemiplegia of childhood patient cohort (n = 42, age 10.24 ± 1.48 years) seen at one US centre. To investigate potential disease progression, we used linear mixed effects models incorporating early and subsequent visits, and Wilcoxon Signed Rank test comparing first and last visits. Potential early-life clinical predictors were determined via multivariable regression. We also compared EEG background at first encounter and at last follow-up. We then performed a retrospective confirmation study on a multicentre cohort of alternating hemiplegia of childhood patients from France (n = 52). To investigate disease progression in the Mashlool mouse, we performed behavioural testing on a cohort of Mashlool^- mice at prepubescent and adult ages (n = 11). Results: US patients, over time, demonstrated mild worsening of non-paroxysmal disability index scores, but not of paroxysmal disability index scores. Increasing age was a predictor of worse scores: P < 0.0001 for the non-paroxysmal disability index, intellectual disability scale and gross motor scores. Earliest non-paroxysmal disability index score was a predictor of last visit non-paroxysmal disability index score (P = 0.022), and earliest intellectual disability score was a predictor of last intellectual disability score (P = 0.035). More patients with EEG background slowing were noted at last follow-up as compared to initial (P = 0.015). Similar worsening of disease with age was also noted in the French cohort: age was a significant predictor of non-paroxysmal disability index score (P = 0.001) and first and last non-paroxysmal disability index score scores significantly differed (P = 0.002). In animal studies, adult Mashlool mice had, as compared to younger Mashlool mice, (i) worse balance beam performance; (ii) wider base of support; (iii) higher severity of seizures and resultant mortality; and (iv) no increased predisposition to hemiplegic or dystonic spells. In conclusion, (i) non-paroxysmal alternating hemiplegia of childhood manifestations show, on average over time, progression associated with severity of early-life non-paroxysmal disability and age. (ii) Progression also occurs in Mashlool mice, confirming that ATP1A3 disease can lead to age-related worsening. (iii) Clinical findings provide a basis for counselling patients and for designing therapeutic trials. Animal findings confirm a mouse model for investigation of underlying mechanisms of disease progression, and are also consistent with known mechanisms of ATP1A3-related neurodegeneration.

Nucleic Acid-Based Therapeutics in Orphan Neurological Disorders: Recent Developments

The possibility of rational design and the resulting faster and more cost-efficient development cycles of nucleic acid–based therapeutics (NBTs), such as antisense oligonucleotides, siRNAs, and gene therapy vectors, have fueled increased activity in developing therapies for orphan diseases. Despite the difficulty of delivering NBTs beyond the blood–brain barrier, neurological diseases are significantly represented among the first targets for NBTs. As orphan disease NBTs are now entering the clinical stage, substantial efforts are required to develop the scientific background and infrastructure for NBT design and mechanistic studies, genetic testing, understanding natural history of orphan disorders, data sharing, NBT manufacturing, and regulatory support. The outcomes of these efforts will also benefit patients with “common” diseases by improving diagnostics, developing the widely applicable NBT technology platforms, and promoting deeper understanding of biological mechanisms that underlie disease pathogenesis. Furthermore, with successes in genetic research, a growing proportion of “common” disease cases can now be attributed to mutations in particular genes, essentially extending the orphan disease field. Together, the developments occurring in orphan diseases are building the foundation for the future of personalized medicine. In this review, we will focus on recent achievements in developing therapies for orphan neurological disorders.

Canavan Disease as a Model for Gene Therapy-Mediated Myelin Repair

In recent years, the scientific and therapeutic fields for rare, genetic central nervous system (CNS) diseases such as leukodystrophies, or white matter disorders, have expanded significantly in part due to technological advancements in cellular and clinical screenings as well as remedial therapies using novel techniques such as gene therapy. However, treatments aimed at normalizing the pathological changes associated with leukodystrophies have especially been complicated due to the innate and variable effects of glial abnormalities, which can cause large-scale functional deficits in developmental myelination and thus lead to downstream neuronal impairment. Emerging research in the past two decades have depicted glial cells, particularly oligodendrocytes and astrocytes, as key, regulatory modulators in constructing and maintaining myelin function and neuronal viability. Given the significance of myelin formation in the developing brain, myelin repair in a time-dependent fashion is critical in restoring homeostatic functionality to the CNS of patients diagnosed with white matter disorders. Using Canavan Disease (CD) as a leukodystrophy model, here we review the hypothetical roles of N-acetylaspartate (NAA), one of the brain's most abundant amino acid derivatives, in Canavan disease's CNS myelinating pathology, as well as discuss the possible functions astrocytes serve in both CD and other leukodystrophies' time-sensitive disease correction. Through this analysis, we also highlight the potential remyelinating benefits of gene therapy for other leukodystrophies in which alternative CNS cell targeting for white matter disorders may be an applicable path for reparative treatment.

Mapping the degradation pathway of a disease-linked aspartoacylase variant

Canavan disease is a severe progressive neurodegenerative disorder that is characterized by swelling and spongy degeneration of brain white matter. The disease is genetically linked to polymorphisms in the aspartoacylase (ASPA) gene, including the substitution C152W. ASPA C152W is associated with greatly reduced protein levels in cells, yet biophysical experiments suggest a wild-type like thermal stability. Here, we use ASPA C152W as a model to investigate the degradation pathway of a disease-causing protein variant. When we expressed ASPA C152W in Saccharomyces cerevisiae, we found a decreased steady state compared to wild-type ASPA as a result of increased proteasomal degradation. However, molecular dynamics simulations of ASPA C152W did not substantially deviate from wild-type ASPA, indicating that the native state is structurally preserved. Instead, we suggest that the C152W substitution interferes with the de novo folding pathway resulting in increased proteasomal degradation before reaching its stable conformation. Systematic mapping of the protein quality control components acting on misfolded and aggregation-prone species of C152W, revealed that the degradation is highly dependent on the molecular chaperone Hsp70, its co-chaperone Hsp110 as well as several quality control E3 ubiquitin-protein ligases, including Ubr1. In addition, the disaggregase Hsp104 facilitated refolding of aggregated ASPA C152W, while Cdc48 mediated degradation of insoluble ASPA protein. In human cells, ASPA C152W displayed increased proteasomal turnover that was similarly dependent on Hsp70 and Hsp110. Our findings underscore the use of yeast to determine the protein quality control components involved in the degradation of human pathogenic variants in order to identify potential therapeutic targets.