Allele-Selective ASO Therapy Overcomes Childhood-Onset Rare Epilepsy, Enabling First Independent Walking
Background
Rare epilepsies that develop during childhood significantly impact the lives of affected children and their families. Specifically, developmental and epileptic encephalopathy (DEE) caused by gain-of-function mutations in the sodium channel subunit alpha 2 gene (SCN2A) is notoriously difficult to treat. This is because the sodium ion channels, which are responsible for electrical signal transmission in neurons, become excessively active, leading to constant overexcitation in the brain. Most affected children experience severe seizures from infancy and suffer from cognitive impairment and motor dysfunction. Existing antiepileptic drugs indiscriminately reduce overall brain activity, resulting in limited therapeutic efficacy and potentially causing serious side effects such as cognitive decline. There was an urgent need for personalized therapies that precisely target and control the mutated gene.
Key Findings
A joint research team from the University of California San Diego (UCSD) and the Rady Children's Institute for Genomic Medicine (RCIGM) has developed a therapy that selectively silences one copy of the mutated gene. The researchers performed precise analysis of individual genetic variations in patients and designed customized antisense oligonucleotides (ASOs) that target only the mutated gene while preserving the normal gene. These ASOs bind to the mutated messenger RNA (mRNA), blocking protein translation and inhibiting excessive sodium ion influx.
According to clinical results published in the international journal Nature Medicine, the therapy was administered to two patients, aged 9 and 14, for two years. The treatment resulted in a significant reduction in the frequency of seizures in both patients. Notably, a 14-year-old patient named Connor, who had been dependent on a wheelchair, was able to walk independently after two years of treatment, surprising those around him. This suggests that normalization of the sodium channel function may have reorganized neural circuits, restoring signal transmission in the motor cortex. This demonstrates a fundamental recovery at the gene level, which was difficult to achieve with conventional symptomatic drug treatments.
Significance and Prospects
Although this study involved only two patients, it demonstrates that personalized gene therapy can be a fundamental alternative for rare encephalopathies. It has transformed the possibility of precision medicine, which targets the unique mutation sequence of each individual patient, into a reality.
However, there are still challenges to be addressed before commercialization. The process of designing and producing ASOs that are optimized for the genetic variations of individual patients requires significant time and resources. It is also necessary to streamline the regulatory framework to facilitate the approval process for the safety and efficacy of each therapeutic agent. Despite these challenges, this achievement is considered a milestone that shows that gene silencing technology can not only extend life but also substantially restore the physical function of patients. Furthermore, it opens up the possibility of expanding to other neurological disorders with similar genetic mechanisms. If a system is established to shorten the initial design phase and rapidly verify efficacy, the widespread adoption of precision medicine for rare diseases may not be far off.
Nature, Published online: 24 July 2026; doi:10.1038/d41586-026-02267-0Switching off one copy of a gene also enabled one of the children to walk independently for the first time.
The success of personalized ASO therapy has not only 'treated' genetic defects but has also enabled patients to live as independent members of society by providing practical rehabilitation. In particular, the fact that motor areas damaged by epileptic seizures can be normalized through gene silencing therapy provides a new benchmark for clinical practice. It has demonstrated that a 'bench-to-bedside' model, in which hospitals and research institutions collaborate to immediately develop and administer a treatment for a single patient, can function effectively in pediatric neurological diseases. From the perspective of the pharmaceutical industry, the rapid approval and supply chain establishment of ultra-precise medical products for a small number of patients is likely to become a new paradigm in the market. Ultimately, this is expected to provide tangible benefits, such as independent walking and cognitive recovery, to many children with genetic developmental delays.