Precision therapeutics for early onset epilepsy: Allele-selective antisense oligonucleotides for SCN2A-related epilepsy.

Developmental and epileptic encephalopathies (DEE) frequently present with uncontrolled seizures from birth, and SCN2A is among the most prevalent monogenic epilepsies, with pathogenic variants accounting for 1%–2% of all epileptic encephalopathies. Many causal variants confer gain- of-function or mixed-function effects— increased channel open probability or elevated persistent sodium current—and genotype-phenotype relationships within the gene are correspondingly heterogeneous. Conventional anti-seizure medications and surgical neuromodulatory approaches can confer meaningful therapeutic benefit in patients with DEE; nonetheless seizure control remains challenging in many patients, and developmental trajectories are typically static or slowly progressive despite optimized pharmacotherapy. Targeted genetic therapy directed at the underlying molecular etiology, if identified, may therefore provide additional benefit. Per recent publication in Nature Medicine which was featured in Nature Research Highlight, we conducted two parallel open- label, single-center, single-patient (n-of-1) trials in two male patients harboring a distinct heterozygous pathogenic SCN2A variants. The therapeutic logic—allele-selective suppression of a transcript with a net excitatory consequence—was applied to one gain-of- function and one mixed variant; predominantly loss-of-function SCN2A variants are mechanistically distinct and require an orthogonal, augmentation-based approach. Both participants tolerated investigational therapeutic intervention with no ASO- related adverse events or serious adverse events. Both demonstrated reductions in seizure burden, although the magnitude and statistical robustness of the response differed. There were significant developmental gains—de novo independent ambulation in a 15-year old—of a magnitude unlikely to reflect natural history in a population characterized by static or worsening trajectories. Participants were treated after years of established disease and nonetheless acquired therapeutic benefit. Because the genetic cause is identifiable by neonatal genome sequencing, and intrathecal ASO delivery is tolerable in early infancy, substantially earlier intervention is achievable; these responses in heavily affected, long-symptomatic patients may be a conservative estimate of what earlier treatment might yield. Individualized manufacturing and regulatory pathways, academic infrastructure and expertise for delivery remain resource- intensive and require funding support although haplospecific approach theoretically enables scalability. Mechanistically informed, allele-selective ASO therapy can be safely designed, manufactured, and administered to patients with rare SCN2A variants, yielding clinically meaningful seizure and developmental outcomes in addition to those provided by conventional anti-seizure medications and surgical neuromodulatory approaches—an early but structurally important step toward ASO therapeutics as a treatment paradigm for rare neurogenetic disease, including developmental and epileptic encephalopathies.