Gene therapy for monogenic disorders: challenges, strategies, and perspectives

Translation of genomics into routine cardiological practice: insights from a European Society of Cardiology Cardiovascular Round Table

Cardiovascular diseases (CVD) remain the leading cause of death globally and there is an urgent need for innovative approaches to treatment. One emerging avenue is genetic therapies, which hold particular promise for diseases with a monogenic basis. Gene silencing techniques using antisense oligonucleotides or ribonucleic acid interference strategies are currently at the forefront of genetic therapies in CVD, with several ribonucleic acid-targeted therapies already approved for the treatment of conditions such as familial hypercholesterolaemia and transthyretin amyloidosis. For diseases caused by loss-of-function genetic variants, there is growing interest in gene therapy, applying either gene replacement strategies using adeno-associated virus vectors or gene editing strategies using tools such as the clustered regularly interspaced short palindromic repeats and clustered regularly interspaced short palindromic repeats-associated protein-9 system. Preclinical studies have highlighted the potential of this technology in CVD and promising data are beginning to emerge from early-phase clinical trials. During a European Society of Cardiology Cardiovascular Round Table workshop, the challenges of translating these novel therapeutic strategies to the routine cardiology clinic were discussed. Several key priorities were identified, including the need for disease-specific preclinical models, precision diagnostics, adequately powered clinical trials with meaningful endpoints, and enhanced education of healthcare professionals and patients. The Cardiovascular Round Table also considered the role of polygenic risk scores in risk stratification and how these can potentially be implemented in clinical practice.

Balancing benefits and burdens: a systematic review on ethical and social dimensions of gene and cell therapies for hereditary blood diseases

BACKGROUND

Sickle cell disease (SCD) and Diamond-Blackfan anemia syndrome (DBAS) are two hereditary blood diseases that present significant challenges to patients, their caregivers, and the healthcare system. Both conditions cause severe health complications and have limited treatment options, leaving many individuals without access to curative therapies like hematopoietic stem cell transplantation. Recent advancements in gene and cell therapies offer the potential for a new curative option, marking a pivotal shift in the management of these debilitating diseases. However, the implementation of these therapies necessitates a nuanced understanding of the ethical and social implications.

METHODS

In this mixed methods systematic review, we explore the responsible development and implementation of gene and cell therapies for SCD and DBAS and aim to sketch a path toward ethically and socially sound implementation. Drawing upon principles of Responsible Research & Innovation and the 4A framework of availability, accessibility, acceptability, and affordability, we thematically analyze existing research to illuminate the ethical and social dimensions of these therapies. Following established PRISMA and JBI Manual guidelines, a search across multiple databases yielded 51 peer-reviewed studies with publication dates ranging from 1991 to 2023.

RESULTS

Our thematic analysis shows that the theme of acceptability is heavily shaped by interactions between patients, caregivers, healthcare professionals and researchers, influencing treatment decisions and shaping the development of curative gene and cell therapies. Despite the generally positive perspective on these therapies, factors like the limited treatment options, financial constraints, healthcare professional attitudes, and (historical) mistrust can impede stakeholder decision-making. While acceptability focuses on individual decisions, the themes of availability, accessibility, and affordability are interconnected and primarily driven by healthcare systems, where high research and development costs, commercialization and a lack of transparency challenge equitable access to these therapies. This diminishes the acceptability for patients, revealing a complex interdependence of the themes.

CONCLUSIONS

The findings suggest the need for improved communication strategies in clinical practice to facilitate informed decision-making for patients and caregivers. Policy development should focus on addressing pricing disparities and promoting international collaboration to ensure equitable access to therapies. This review has been pre-registered in PROSPERO under registration number CRD42023474305.

Plasmid Gene Therapy for Monogenic Disorders: Challenges and Perspectives

Monogenic disorders are a group of human diseases caused by mutations in single genes. While some disease-altering treatments offer relief and slow the progression of certain conditions, the majority of monogenic disorders still lack effective therapies. In recent years, gene therapy has appeared as a promising approach for addressing genetic disorders. However, despite advancements in gene manipulation tools and delivery systems, several challenges remain unresolved, including inefficient delivery, lack of sustained expression, immunogenicity, toxicity, capacity limitations, genomic integration risks, and limited tissue specificity. This review provides an overview of the plasmid-based gene therapy techniques and delivery methods currently employed for monogenic diseases, highlighting the challenges they face and exploring potential strategies to overcome these barriers.

Biallelic variants in SREBF2 cause autosomal recessive spastic paraplegia

Hereditary spastic paraplegias (HSPs) refer to a genetically and clinically heterogeneous group of neurodegenerative disorders characterized by the degeneration of motor neurons. To date, a significant number of patients still have not received a definite genetic diagnosis. Therefore, identifying unreported causative genes continues to be of great importance. Here, we perform whole exome sequencing in a cohort of Chinese HSP patients. Three homozygous variants (p.L604W, p.S517F, and p.T984A) within the sterol regulatory element-binding factor 2 (SREBF2) gene are identified in one autosomal recessive family and two sporadic patients, respectively. Co-segregation is confirmed by Sanger sequencing in all available members. The three variants are rare in the public or in-house database and are predicted to be damaging. The biological impacts of variants in SREBF2 are examined by functional experiments in patient-derived fibroblasts and Drosophila. We find that the variants upregulate cellular cholesterol due to the overactivation of SREBP2, eventually impairing the autophagosomal and lysosomal functions. The overexpression of the mature form of SREBP2 leads to locomotion defects in Drosophila. Our findings identify SREBF2 as a causative gene for HSP and highlight the impairment of cholesterol as a critical pathway for HSP.

Autologous transplantation of mitochondria/rAAV IGF-I platforms in human osteoarthritic articular chondrocytes to treat osteoarthritis

Despite various available treatments, highly prevalent osteoarthritis (OA) cannot be cured in patients. In light of evidence showing mitochondria dysfunction during the disease progression, our goal was to develop a novel therapeutic concept based on the transplantation of mitochondria as a platform to deliver recombinant adeno-associated virus (rAAV) gene vectors with potency for OA. For the first time, to our best knowledge, we report the successful creation of a safe mitochondria/rAAV system effectively promoting the overexpression of a candidate insulin-like growth factor I (IGF-I) by administration to autologous human osteoarthritic articular chondrocytes versus control conditions (reporter mitochondria/rAAV lacZ system, rAAV-free system, absence of mitochondria transplantation; up to 8.4-fold difference). The candidate mitochondria/rAAV IGF-I system significantly improved key activities in the transplanted cells (proliferation/survival, extracellular matrix production, mitochondria functions) relative to the control conditions (up to a 9.5-fold difference), including when provided in a pluronic F127 (PF127) hydrogel for reinforced delivery (up to a 5.9-fold difference). Such effects were accompanied by increased levels of cartilage-specific SOX9 and Mfn-1 (mitochondria fusion) and decreased levels of Drp-1 (mitochondria fission) and proinflammatory tumor necrosis factor alpha (TNF-α; up to 4.5-fold difference). This study shows the potential of combining the use of mitochondria with rAAV as a promising approach for human OA.

Engineered tRNAs efficiently suppress CDKL5 premature termination codons

The CDKL5 deficiency disorder (CDD) is a severe neurodevelopmental disorder characterized by early-onset epilepsy, intellectual disability, motor and visual dysfunctions. The causative gene is CDKL5, which codes for a kinase required for brain development. There is no cure for CDD patients; treatments are symptomatic and focus mainly on seizure control. Several pathogenic variants are loss-of-function, but recent studies suggest that the CDD phenotype is sensitive to the CDKL5 gene dosage. Therefore, mRNA-targeted correction strategies that respect the physiological regulation of CDKL5 could be a valid alternative to augmentative gene therapy. Nonsense mutations cause ~ 11% of CDD cases, and these patients might benefit from readthrough therapies. We proved that drug-mediated readthrough efficiently suppresses premature CDKL5 nonsense codons, but the recoded kinase remained highly hypomorphic, curtailing the translational value of this pharmacological approach. In this study we explored if the recently developed Anticodon-edited tRNAs (ACE-tRNAs) offer an alternative readthrough strategy for CDD. Transfecting cells expressing different CDKL5 nonsense variants, we demonstrated that ACE-tRNAs efficiently restore full-length kinase synthesis. The recoded CDKL5 is correctly localized and catalytically active, thereby bringing tRNA-based therapy back into the spotlight for future investigations to assess the efficacy of this approach in correcting the pathological phenotype of CDD.

Gene therapy and gene editing strategies in inherited blood disorders

Gene therapy has shown significant potential in treating various diseases, particularly inherited blood disorders such as hemophilia, sickle cell disease, and thalassemia. Advances in understanding the regulatory network of disease-associated genes have led to the identification of additional therapeutic targets for treatment, especially for β-hemoglobinopathies. Erythroid regulatory factor BCL11A offers the most promising therapeutic target for β-hemoglobinopathies, and reduction of its expression using the commercialized gene therapy product Casgevy has been approved for use in the UK and USA in 2023. Notably, the emergence of innovative gene editing technologies has further broadened the gene therapy landscape, presenting possibilities for treatment. Intensive studies indicate that base editing and prime editing, built upon CRISPR technology, enable precise single-base modification in hematopoietic stem cells for addressing inherited blood disorders ex vivo and in vivo. In this review, we present an overview of the current landscape of gene therapies, focusing on clinical research and gene therapy products for inherited blood disorders, evaluation of potential gene targets, and the gene editing tools employed in current gene therapy practices, which provides an insight for the establishment of safer and more effective gene therapy methods for a wider range of diseases in the future.

Assessment the carrier frequency of monogenic diseases in populations requiring assisted reproductive technology

PURPOSE

The objective of this study is to assess the carrier frequency and pathogenic variation of monogenetic diseases in a population of 114 subjects in Han Chinese from Hebei province who are undergoing assisted reproductive technology through the utilization of Expanded Carrier Screening (ECS).

METHODS

The study utilized a panel consisting of 155 severe monogenic recessive genetic diseases for ECS. Next-generation sequencing technology was employed to identify specific variants associated with ECS in a cohort of 114 subjects from 97 couples, comprising 97 females and 17 male spouses.

RESULTS

A total of 114 individuals received ECS. The carrier rate of pathogenic genes in the enrolled population was 44.74% (51/114). Among the 97 females, the carrier rate of pathogenic genes was higher in those without assisted reproduction indicators than in those with assisted reproduction indicators (59.09% vs. 41.33%). However, the carrier rate of pathogenic genes in males without assisted reproductive technology was slightly lower than that with assisted reproductive technology (40% vs. 41.67%). Among both female and male participants, the carrier rate of pathogenic genes between individuals without indicators of assisted reproduction and those with such indicators was 55.55% vs. 41.38%. In 51 carriers, 72.55% (37/51) carried one genetic variant, 25.49% (13/51) carried two genetic variants, and 1.96% (1/51) carried three genetic variants. A total of 38 pathogenic genes were detected in this study, and GJB2 and MMACHC were most common. The carrier rates of the two genes were both 5.26% (6/114). A total of 55 variations were detected, and c.235delC was most frequently found. The carrier rate was 3.51% (4/114). The incidence of couples carrying the same pathogenic genes was 1.03% (1/97).

CONCLUSIONS

The findings elucidate the carrier rate of pathogenic genes among 155 severe monogenic recessive genetic diseases and underscore the significance of ECS as a preventive measure against congenital anomalies. When both partners carry the same genetic mutation for a monogenic disease, preventive strategies can be taken in offspring through preimplantation genetic testing (PGT), prenatal genetic testing, or the utilization of donor gametes. ECS is instrumental in assessing reproductive risk, guiding fertility-related decisions, and reducing the prevalence of monogenic recessive genetic disorders in subsequent generations.

Recent Insights in Pyrin Inflammasome Activation: Identifying Potential Novel Therapeutic Approaches in Pyrin-Associated Autoinflammatory Syndromes

Pyrin is a cytosolic protein encoded by the MEFV gene, predominantly expressed in innate immune cells. Upon activation, it forms an inflammasome, a multimolecular complex that enables the activation and secretion of IL-1β and IL-18. In addition, the Pyrin inflammasome activates Gasdermin D leading to pyroptosis, a highly pro-inflammatory cell death. Four autoinflammatory syndromes are associated with Pyrin inflammasome dysregulation: familial Mediterranean fever, hyper IgD syndrome/mevalonate kinase deficiency, pyrin-associated autoinflammation with neutrophilic dermatosis, and pyogenic arthritis, pyoderma gangrenosum, and acne syndrome. In this review, we discuss recent advances in understanding the molecular mechanisms regulating the two-step model of Pyrin inflammasome activation. Based on these insights, we discuss current pharmacological options and identify a series of existing molecules with therapeutic potential for the treatment of pyrin-associated autoinflammatory syndromes.