Emerging Perspectives on Gene Therapy Delivery for Neurodegenerative and Neuromuscular Disorders

All hands on deck: The multidisciplinary rehabilitation assessment and management of hand function in persons with neuromuscular disorders

Hand function is important in every aspect of our lives. Across a wide range of neuromuscular disorders-inherited ataxias, motor neuron diseases, polyneuropathies, and myopathies-people can experience losses in hand strength, tone, movement, dexterity, joint range, and sensation. Such changes can adversely affect function and independence in daily activities, reducing participation and quality of life. People with neuromuscular disorders (pwNMD) known to involve the hand should be assessed at regular intervals for changes both clinically and using impairment, performance, function, and patient-reported outcome measures as appropriate. A patient-centered approach to management is recommended, with clinicians partnering with the individual, their caregivers and the interprofessional teams to create personalized solutions that can overcome barriers to participation and best meet the goals of individuals affected by neuromuscular disorders. Management strategies should be multifaceted, and may include exercise, orthoses, assistive devices, technological solutions, environmental or task adaptations, medications, and/or surgery. Exercise recommendations and orthoses should be individualized and evolve based on disease progression, impairments, and functional limitations. While medications and surgery have a small role for specific clinical situations, there is a plethora of assistive and technological solutions to assist with basic and instrumental activities of daily living, work/education, and leisure for pwNMD with reduced hand function. In addition, clinicians should advocate for appropriate accommodations for reduced hand function at work/school, and the development of and adherence to legislation supporting accessibility and inclusion.

Is Duchenne gene therapy a suitable treatment despite its immunogenic class effect?

INTRODUCTION

Duchenne muscular dystrophy (DMD) is a severe X-linked disorder characterized by progressive muscle weakness and eventual death due to cardiomyopathy or respiratory complications. Currently, there is no cure for DMD, with standard treatments primarily focusing on symptom management. Using immunosuppressive measures and optimized vector designs allows for gene therapies to better address the genetic cause of the disease.

AREAS COVERED

This review evaluates the efficacy and safety of emerging DMD gene therapies as of 2024. It also discusses the potential of utrophin upregulation, gene editing, and truncated dystrophin as therapeutic strategies. It highlights safety concerns associated with these therapies, including adverse events and patient deaths. A comprehensive overview of developments covers topics such as CRISPR-Cas9 therapies, micro-dystrophin, and the potential delivery of full-length dystrophin.

EXPERT OPINION

The FDA's recent approval of delandistrogene moxeparvovec (Elevidys) underscores the promise of gene replacement therapies for DMD patients. Understanding the mechanisms behind the adverse effects and excluding patients with specific pathogenic variants may enhance the safety profiles of these therapies. CRISPR/Cas9 therapies, while promising, face significant regulatory and safety challenges that hinder their clinical application. Optimal DMD therapies should target both skeletal and cardiac muscles to be effective.

Triumphs, Trials, and Future Considerations in Genetic Therapies for Hereditary Neuromuscular Diseases

Neuromuscular diseases include conditions that affect the spinal motor neurons, peripheral nerves, neuromuscular junctions, and muscles, and they can result from acquired and inherited causes. The number of genetic therapies targeting the inherited causes of neuromuscular diseases has surged in the last decade. This review aims to highlight the current state of genetic therapies within the framework of precision medicine, focusing on the achievements and the gaps that remain. A major emphasis is on spinal muscular atrophy, Duchenne muscular dystrophy, and amyotrophic lateral sclerosis, as these neuromuscular diseases have seen tremendous recent advancements. We will also discuss the future considerations necessary to accelerate the development of next-generation genetic therapies and enhance therapeutic outcomes for patients with neuromuscular diseases.

Gut microbiota and Alzheimer's disease: Exploring natural product intervention and the Gut-Brain axis for therapeutic strategies

Numerous studies conducted over the last ten years have shown a strong correlation between the gut microbiota and the onset and progression of Alzheimer's disease (AD). However, the exact underlying mechanism is still unknown. An ongoing communication mechanism linking the gut and the brain is highlighted by the term "microbiota-gut-brain axis," which was originally coined the "gut-brain axis." Key metabolic, endocrine, neurological, and immunological mechanisms are involved in the microbiota‒gut‒brain axis and are essential for preserving brain homeostasis. Thus, the main emphasis of this review is how the gut microbiota contributes to the development of AD and how various natural products intervene in this disease. The first part of the review provides an outline of various pathways and relationships between the brain and gut microbiota, and the second part provides various mechanisms involved in the gut microbiota and AD. Finally, this review provides knowledge about natural products and their effectiveness in treating gut microbiota-induced AD. AD may be treated in the future by altering the gut microbiota with a customized diet, probiotics/prebiotics, plant products, and natural products. This entails altering the microbiological partners and products (such as amyloid protein) that these partners generate.

Clinical and Translational Landscape of Viral Gene Therapies

Gene therapies hold significant promise for treating previously incurable diseases. A number of gene therapies have already been approved for clinical use. Currently, gene therapies are mostly limited to the use of adeno-associated viruses and the herpes virus. Viral vectors, particularly those derived from human viruses, play a critical role in this therapeutic approach due to their ability to efficiently deliver genetic material to target cells. Despite their advantages, such as stable gene expression and efficient transduction, viral vectors face numerous limitations that hinder their broad application. These limitations include small cloning capacities, immune and inflammatory responses, and risks of insertional mutagenesis. This review explores the current landscape of viral vectors used in gene therapy, discussing the different types of DNA- and RNA-based viral vectors, their characteristics, limitations, and current medical and potential clinical applications. The review also highlights strategies to overcome existing challenges, including optimizing vector design, improving safety profiles, and enhancing transgene expression both using molecular techniques and nanotechnologies, as well as by approved drug formulations.

AAV-aMTD-Parkin, a therapeutic gene delivery cargo, enhances motor and cognitive functions in Parkinson's and Alzheimer's diseases

Neurodegenerative disorders, such as Parkinson's disease (PD) and Alzheimer's disease (AD), have a global prevalence and profoundly impact both motor and cognitive functions. Although adeno-associated virus (AAV)-based gene therapy has shown promise, its application for treating central nervous system (CNS) diseases faces several challenges, including effective delivery of AAV vectors across the blood-brain barrier, determining optimal dosages, and achieving targeted distribution. To address these challenges, we have developed a fusion delivery therapeutic cargo called AAV-aMTD-Parkin, which combines a hydrophobic cell-penetrating peptide sequence with the DNA sequences of AAV and Parkin. By employing this fusion delivery platform at lower dosages compared to zolgensma, we have achieved significant enhancements in cell and tissue permeability, while reducing the occurrence of common pathological protein aggregates. Consequently, motor and cognitive functions were restored in animal models of PD and AD. With its dual functionality in addressing PD and AD, AAV-aMTD-Parkin holds immense potential as a novel class of therapeutic biologics for prevalent CNS diseases.

Bioinspired Approaches for Central Nervous System Targeted Gene Delivery

Disorders of the central nervous system (CNS) which include a wide range of neurodegenerative and neurological conditions have become a serious global issue. The presence of CNS barriers poses a significant challenge to the progress of designing effective therapeutic delivery systems, limiting the effectiveness of drugs, genes, and other therapeutic agents. Natural nanocarriers present in biological systems have inspired researchers to design unique delivery systems through biomimicry. As natural resource derived delivery systems are more biocompatible, current research has been focused on the development of delivery systems inspired by bacteria, viruses, fungi, and mammalian cells. Despite their structural potential and extensive physiological function, making them an excellent choice for biomaterial engineering, the delivery of nucleic acids remains challenging due to their instability in biological systems. Similarly, the efficient delivery of genetic material within the tissues of interest remains a hurdle due to a lack of selectivity and targeting ability. Considering that gene therapies are the holy grail for intervention in diseases, including neurodegenerative disorders such as Alzheimer's disease, Parkinson's Disease, and Huntington's disease, this review centers around recent advances in bioinspired approaches to gene delivery for the prevention of CNS disorders.

Gene therapy in Aβ-induced cell and mouse models of Alzheimer's disease through compensating defective mitochondrial complex I function

BACKGROUND

Alzheimer's disease (AD) is the most common neurogenerative disorder without effective treatments. Defects in mitochondrial complex I are thought to contribute to AD pathogenesis. The aim of this study is to explore whether a novel gene therapy transducing yeast complex I gene NDI1 can be used to treat AD with severely reduced complex I function in cell and animal models.

METHODS

The differentiated human neural cells were induced by Aβ1-42 to establish the AD cell model, and adeno-associated virus serotype 9 (AAV9) was used to transduce yeast NDI1 into the cell model. Aβ1-42 was injected into the hippocampus area of the brain to establish the AD mouse model. AAV9-NDI1 was injected stereotaxically into the hippocampus area to test the therapeutic effect.

RESULTS

The expressed yeast complex I had an ameliorating effect on the defective function of human complex I and cellular pathological characteristics in the AD cell model. Furthermore, AAV9-NDI1 gene therapy in the hippocampus had a therapeutic effect on various aspects of mitochondrial function, histopathological characteristics and neurological defects in the AD mouse model. In addition, AAV9-NDI1 injection into the hippocampus of normal mice did not cause any adverse effect.

CONCLUSIONS

Compensating mitochondrial complex I function with yeast NDI1 is effective for gene therapy in Aβ-induced AD cell and mouse models. The results of this study offer a novel strategy and approach for treating AD types characterized by complex I abnormalities.

Gene therapy for primary myopathies: literature review and prospects

Gene therapy has emerged as a promising frontier in the pursuit of effective treatments for primary myopathies. This scientific review explores the application of viral vectors and more specifically of recombinant adeno-associated virus (rAAV) vectors as a potent gene delivery tool in the context of primary myopathies, highlighting its transformative potential. Focusing on primary myopathies, including Duchenne muscular dystrophy (DMD), limb-girdle muscular dystrophies (LGMDs), X-linked myotubular myopathy (XLMTM), and Pompe disease, we review the ongoing pre-clinical and clinical trials that underscore the therapeutic promise of rAAV-based gene therapies. Recent developments in gene therapy have unveiled innovative gene transfer approaches, particularly with rAAV vectors. These vectors offer a well-tolerated and efficient means of delivering corrective genetic material to diseased muscles, thereby addressing the root causes of primary myopathies. Encouraging data from pre-clinical studies and early clinical trials have demonstrated the potential to ameliorate muscle function, reduce pathological manifestations, and enhance the quality of life for patients afflicted with these devastating diseases. However, the transition from bench to bedside is not without challenges. This review emphasizes the critical need for a comprehensive risk management strategy to better handle potential side effects and immune responses associated with gene therapy. As the field of gene therapy for primary myopathies is advancing, it is imperative to refine and optimize safety measures, ensuring that the transformative potential of these therapies is realized while the risks are minimized. © 2023 Published by Elsevier Masson SAS on behalf of French Society of Pediatrics.