Over Half of Infants With Genetic Epilepsy May Benefit From ASO Therapy
A multinational study finds 56% of genetically diagnosed infants with epilepsy have variants potentially amenable to antisense oligonucleotide treatment.
Summary
Researchers from four major pediatric centers across the US, Canada, Australia, and UK analyzed 406 infants with genetic epilepsy to determine how many could potentially benefit from antisense oligonucleotide (ASO) therapy — a precision medicine approach that targets disease-causing genetic variants at the RNA level. Using established ASO amenability criteria, they found that 56% of genetically diagnosed infants had variants that could theoretically be treated with ASO-based approaches. The most common amenable mechanisms included gene silencing for gain-of-function mutations and splice-switching for variants affecting RNA processing. This large-scale systematic assessment highlights ASO therapy as a broadly applicable precision medicine strategy for infantile epilepsies, a group of devastating early-onset neurological conditions with very limited treatment options.
Detailed Summary
Infantile genetic epilepsies represent some of the most severe and treatment-resistant neurological conditions in pediatrics. These disorders, caused by mutations in genes controlling neuronal excitability and development, often begin in the first year of life and are associated with profound developmental impairment, drug-resistant seizures, and high mortality. Antisense oligonucleotides (ASOs) — short synthetic nucleic acid strands that modulate gene expression at the RNA level — have emerged as a promising precision medicine platform, with several already approved for neurological diseases. However, no systematic evaluation had previously quantified what proportion of infants with genetic epilepsy might be candidates for ASO-based treatment.
The Gene-STEPS Study Group conducted a multinational cohort study across four leading pediatric centers: Boston Children's Hospital, The Hospital for Sick Children (Toronto), Murdoch Children's Research Institute/Royal Children's Hospital (Melbourne), and UCL Great Ormond Street Institute of Child Health (London). The study enrolled 406 infants who received a genetic diagnosis of epilepsy within the first year of life. Researchers applied a structured ASO amenability framework — based on published criteria encompassing gene expression in the CNS, variant type, and proposed molecular mechanism — to classify each patient's causative variant as amenable or not amenable to one or more ASO therapeutic strategies.
Of the 406 genetically diagnosed infants, 228 (56%) had at least one variant classified as potentially amenable to ASO therapy. The most frequently implicated ASO mechanisms were gene knockdown (applicable to gain-of-function variants, particularly in sodium channel genes such as SCN2A and SCN8A), splice-switching (for variants disrupting canonical splice sites or creating cryptic splice sites), and translational read-through (for nonsense variants). SCN1A, the gene most commonly mutated in Dravet syndrome, was among the top genes identified, with multiple ASO strategies potentially applicable depending on variant type.
The study also stratified amenability by gene and variant class. Missense variants with established gain-of-function effects and loss-of-function variants with haploinsufficiency mechanisms showed the highest rates of ASO amenability. Notably, the researchers found that a single gene could harbor variants amenable to different ASO strategies depending on the specific mutation, underscoring the need for individualized molecular characterization rather than gene-level treatment decisions. Genes involved in ion channel function, synaptic transmission, and transcriptional regulation were disproportionately represented among amenable cases.
The authors acknowledge several important limitations. ASO amenability was assessed computationally and clinically using established criteria, but actual therapeutic efficacy would require experimental validation for each variant and ASO design. The cohort, while large for this rare disease context, was drawn from specialized academic centers and may not fully represent the broader population of infants with genetic epilepsy. Additionally, the rapidly evolving ASO design landscape means amenability classifications may shift as new chemistries and delivery methods emerge. Several senior authors disclosed relationships with ASO-focused pharmaceutical companies, which should be considered when interpreting enthusiasm for this therapeutic modality.
Despite these caveats, the findings carry significant clinical implications. With more than half of genetically diagnosed infants potentially eligible for ASO-based precision therapy, the study makes a compelling case for integrating rapid genomic diagnosis into neonatal and infant epilepsy care pathways — not merely for diagnostic closure, but as a gateway to targeted treatment. The results also provide a roadmap for prioritizing ASO development programs, suggesting that platform approaches targeting common epilepsy genes could benefit the largest number of patients most efficiently.
Key Findings
- 56% of genetically diagnosed infants with epilepsy (228/406) had variants potentially amenable to at least one ASO therapeutic strategy
- Gene knockdown was the most applicable ASO mechanism, particularly for gain-of-function variants in sodium channel genes (SCN2A, SCN8A, SCN1A)
- Splice-switching ASOs were applicable to a substantial subset of patients with splice-site or cryptic splice-site variants
- A single gene could harbor variants amenable to different ASO strategies depending on the specific mutation, requiring individualized molecular assessment
- Ion channel genes, synaptic transmission genes, and transcriptional regulators were disproportionately represented among ASO-amenable cases
- The cohort spanned four countries (US, Canada, Australia, UK) across four major pediatric epilepsy centers, representing a broad international sample
- Nonsense variants were identified as candidates for translational read-through ASO strategies, expanding the amenable population beyond splice and knockdown targets
Methodology
This was a multinational retrospective cohort study enrolling 406 infants with genetically confirmed epilepsy diagnosed within the first year of life across four academic pediatric centers (Boston, Toronto, Melbourne, London). Each patient's causative variant was systematically evaluated against a structured ASO amenability framework based on published criteria including CNS gene expression, variant type, and molecular mechanism. No control group was used, as this was a prevalence/amenability assessment rather than an interventional trial. Statistical analysis focused on proportions and stratification by gene, variant class, and ASO mechanism type.
Study Limitations
ASO amenability was determined through computational and clinical criteria rather than experimental validation, meaning actual therapeutic benefit for individual variants remains unproven. The cohort was recruited from specialized academic centers, potentially overrepresenting severe or complex cases and limiting generalizability to community settings. Multiple senior authors disclosed financial relationships with ASO-focused pharmaceutical companies, representing a potential conflict of interest in interpreting the breadth of ASO applicability.
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