More than 300 STXBP1 variants cause epileptic encephalopathy, moving beyond empirical treatment to precision medicine
Background
MUNC18-1 protein, a key component of synaptic signal transmission, is disrupted
In the synaptic cleft where brain nerve cells exchange signals, highly sophisticated molecular mechanisms are at play. In particular, the MUNC18-1 protein, which mediates the fusion of vesicles containing neurotransmitters with the cell membrane, plays an essential role. What happens if a pathogenic variant occurs in the STXBP1 gene that produces this protein? Protein deficiency disrupts cell-to-cell communication, leading to an overall overload of brain function.
Limitations of clinical practice that relies on empirical drug administration
STXBP1-related disorders (STXBP1-RD) are rare diseases, occurring in approximately 1 in 30,000-40,000 newborns, and are among the most common monogenic developmental and epileptic encephalopathies (DEE). Patients experience complex symptoms such as developmental delays and early-onset epilepsy. However, there are no treatments in clinical practice that target the underlying cause. As a result, the primary treatment has been the administration of antiepileptic drugs to temporarily suppress seizures, but it has been pointed out that this approach cannot prevent cognitive decline.
Key Findings
Haploinsufficiency and seizure polarization caused by more than 300 variants
An analysis of studies in medical databases revealed that more than 300 pathogenic variants have been identified in the STXBP1 gene. Most of these variants are de novo heterozygous mutations. The main mechanism is haploinsufficiency, in which a variant occurs in one of the two alleles, reducing protein production by half.
Analysis of clinical cohorts showed that the majority of patients experienced their first seizure within the first year of life. The progression of seizures follows two paths. Some patients experience spontaneous remission of seizures within the first year of life, but the majority progress to drug-resistant epilepsy and experience frequent seizures. Neurological developmental delays are also severe. Only about half of all patients are able to walk independently, and the proportion of patients who can communicate is less than 30%. The overall mortality rate is low, but SUDEP (Sudden Unexpected Death in Epilepsy) accounts for a significant proportion of the causes of death.
Existing management methods and the emergence of next-generation targeted therapies
Among the existing therapies, phenobarbital, clobazam, and ketogenic diet have shown clinical evidence supporting seizure reduction. At the same time, the development of precision therapies that directly target the underlying mechanisms of the disease is also being pursued.
Adeno-associated virus (AAV) gene replacement therapy and antisense oligonucleotide (ASO) technology are representative examples. In addition, chemical chaperones such as 4-phenylbutyrate, CRISPR-based transcriptional activation technology, and microRNA inhibition therapy are being developed as alternatives. Attempts to modulate neuronal network excitability with serotonergic agents are also promising.
Significance and Prospects
Molecularly targeted therapies usher in the era of precision medicine for single-gene brain diseases
This analysis study is a milestone that shows that the treatment of single-gene brain diseases is moving beyond the empirical symptom control of the past to a precision medicine era centered on molecular targets. Next-generation therapies focus on normalizing the expression of MUNC18-1 protein in synapses, rather than simply suppressing seizures. This approach is considered a promising key to improving developmental impairments, such as intellectual disability and gait disturbances, which have been left untreated.
Challenges in establishing early diagnosis infrastructure and improving delivery technology
However, there are still many challenges to be overcome before it can be implemented in clinical practice. The biggest challenge is the technological barrier of efficiently delivering therapeutic agents to all brain nerve cells. It is also essential to establish safety measures to prevent adverse effects due to protein overexpression. Furthermore, there is a growing call for the full implementation of newborn screening systems to enable diagnosis in the early infancy, before brain development progresses.
STXBP1-related disorders (STXBP1-RD), caused by pathogenic variants in STXBP1 encoding the presynaptic protein MUNC18-1, affects approximately 1 in 30,000-40,000 individuals and is among the most common monogenic developmental and epileptic encephalopathies (DEE). It is characterized by universal neurodevelopmental impairment, early-onset epilepsy, movement disorders, and autism spectrum features, yet treatment remains largely empirical. We conducted a comprehensive narrative review of studies indexed in PubMed/MEDLINE, Embase, Cochrane Library, ClinicalTrials.gov, and American Epilepsy Society proceedings through January 2026, synthesizing molecularly confirmed cohorts, mechanistic studies, and therapeutic investigations. Over 300 pathogenic variants have been identified, predominantly de novo heterozygous, with haploinsufficiency as the principal mechanism. Seizure onset typically occurs within the first months of life, with the vast majority presenting in the first year. Two broad trajectories emerge across cohorts: spontaneous seizure remission in a substantial minority - most within the first year - and persistent drug-resistant epilepsy in the remainder, with a significant proportion experiencing frequent seizures at long-term follow-up. Severe to profound intellectual disability affects the great majority of individuals; independent ambulation and functional verbal communication are achieved by roughly half and less than one-third, respectively. Movement disorders and autism spectrum features are common, and mortality, while modest in absolute terms, includes a disproportionate contribution from SUDEP. Current management is empirical, with phenobarbital, clobazam, and ketogenic diet supported by the most consistent retrospective cohort evidence for seizure reduction. Emerging precision approaches include AAV-mediated gene replacement, antisense oligonucleotides, 4-phenylbutyrate, CRISPR-based transcriptional activation, microRNA inhibition, and serotonergic
This analysis is expected to be the foundation for realizing a personalized early intervention scenario based on the genetic information of each patient. In clinical practice, STXBP1 variants are rapidly identified through newborn genetic panel testing or whole-exome sequencing immediately after birth. Subsequently, ASO or CRISPR transcriptional activation therapy is administered in the early infancy, before the first seizures occur, to block brain damage early on. This proactive approach is a promising scenario that can not only prevent intractable seizures but also minimize cognitive and motor developmental delays, enabling patients to live independent lives.