Rare diseases affect hundreds of millions worldwide, with most cases having genetic origins and primarily impacting children. Despite advancements in diagnosis, the development of personalized and effective treatment strategies remains limited, with only 6% of rare diseases having effective therapies. This lack of treatments contributes to high mortality rates, especially among young patients. Many of these diseases result from mutations that affect RNA splicing, a crucial process in gene expression. Mutations in cis-acting elements, such as splice sites, can lead to aberrant splicing, causing dysfunctional proteins and disease. These mutations can be targeted using antisense oligonucleotides (ASOs): highly versatile therapeutic molecules capable of modulating RNA transcripts to slow or halt the progression of rare genetic diseases, offering personalized treatments options. ASOs have already demonstrated success in treating conditions like spinal muscular atrophy and familial hypercholesterolemia, with several therapies receiving market approval and others undergoing clinical trials. For example, Nusinersen (Spinraza®) and Eteplirsen (Exondys 51®) have been approved by the FDA and have shown effectiveness in treating splicing disorder, thus making patient-customized ASO treatments a promising new avenue for rare disease therapy by targeting specific RNA sequences to modulate gene expression.
In this context, a recent study published in Experimental and Molecular Medicine explored five distinct splicing mutations linked to various rare genetic disorders. Researchers developed tailored ASOs to correct aberrant splicing using minigenes assays in vitro as a more feasible alternative to patient-derived cells. Different ASO chemical modifications were tested, with 2’-O-methoxyethyl phosphorothioate (2’-MOE-PS) and Vivo-morpholino emerging as the most effective in restoring normal splicing.
Furthermore, advancements in clinical sequencing technologies are expected to improve the identification of patients with pathogenic genetic variants that are responsive to ASO therapies, enabling more targeted approaches. Another recent study published in Nature highlighted a scalable platform for generating patient-derived cellular models, which can serve as tools for evaluating personalized ASOs in preclinical settings. In this work, researchers successfully developed protocols for ASO delivery in patient-derived organoid models and validated their therapeutic effects. By leveraging induced pluripotent stem cell (iPSC) technology, researchers established a rapid and scalable pipeline to generate patient-derived models using cryopreserved peripheral blood mononuclear cells (PBMCs). This 6-week approach significantly accelerates the preclinical evaluation process, addressing key challenges associated with patient-derived cellular models as time and cost constraints. In this study, cardiac organoids derived from a Duchenne muscular dystrophy (DMD) patient, who carried a structural deletion in dystrophin (DMD) gene showed reversal of disease-associated phenotypes upon ASO treatment. Additionally, novel ASOs were designed for two more DMD patients with deep intronic variants causing aberrant splicing and premature transcript termination. Treatment of cardiac organoids from these patients with custom-designed ASOs successfully restored DMD expression and corrected disease-related cellular abnormalities.
Overall, these findings demonstrate that ASOs can effectively correct different types of mutations, proving their potential as therapeutic agents for rare genetic disorders. Given the urgent need for personalized therapies, innovative approaches such as scalable organoid-based systems could accelerate ASO development while advancing our understanding of genetic diseases.
Since 70-80% of rare disorders are caused by single-gene mutations, ASOs present a promising avenue for disease-modifying treatments, especially for conditions lacking targeted therapies. However, challenges remain, including efficient delivery to affected tissues, determining the optimal level of gene modulation, and managing patient expectations. In addition, ASO effectiveness depends on factors such as mutation location and proximity to wild-type splice sites, necessitating robust screening strategies.
The recent findings discussed here highlight the importance of tailored ASO therapies in treating splicing-related rare diseases. As ASO technology advances, optimizing design and delivery methods will be crucial for broader clinical applications, paving the way for more effective and personalized treatments for rare genetic disorders.
By Roberto Oleari, Department of Pharmacological and Biomolecular Sciences “Rodolfo Paoletti”, University of Milan
Source:
Link: https://www.nature.com/articles/s12276-024-01292-1 and https://www.nature.com/articles/s41586-024-08462-1
Doi: https://doi.org/10.1038/s12276-024-01292-1 and https://doi.org/10.1038/s41586-024-08462-1