RARE DISEASE
STXBP1-related encephalopathy
STXBP1-related encephalopathy
STXBP1-related encephalopathy
Drug discovery
2
drugs
With orphan designations
Overview
STXBP1-related encephalopathy is a rare genetic neurodevelopmental disorder caused by pathogenic variants in the STXBP1 gene, which disrupts synaptic neurotransmitter release. It presents with severe intellectual disability, developmental delay, and early-onset epilepsy (85-90% of cases), often featuring infantile spasms, focal seizures, or refractory seizures. Motor impairments (hypotonia, ataxia, spasticity) and autism spectrum features are common. Phenotypic variability exists, with seizure trajectories ranging from remission to lifelong refractory epilepsy [1][2][14].
Therapies
Antiseizure medications (e.g., levetiracetam, phenobarbital) and ketogenic diet for seizure control; 25% have refractory epilepsy [2][5].
Multidisciplinary care (physical, occupational, speech therapy) for neurodevelopmental support [12][17].
Emerging therapies: Gene replacement (CAP-002 in preclinical trials) and STXBP1 protein-enhancing agents (e.g., 4-phenylbutyrate under investigation) [3][7].
Categories: rare genetic diseases, rare neurological diseases
Research Papers
35 drug discovery papers about STXBP1-related encephalopathy, with 2 first-in-class and 4 next-in-class emerging drug candidates forecasted to outperform the average preclinical success rate. Recent publications:
35 drug discovery papers about STXBP1-related encephalopathy, with 2 first-in-class and 4 next-in-class emerging drug candidates forecasted to outperform the average preclinical success rate. Recent publications:
2026-06-10 | Virtual Screening and Zebrafish Phenotype-Based Evaluation Argues Against Repurposing 4-Phenylbutyrate for STXBP1-Related Disorders.
Syntaxin-binding protein 1 (STXBP1) mutations lead to severe epilepsy, intellectual disability, developmental delay, and movement disorder. Effective treatments for these conditions do not exist. Recent studies in Munc18-1 (STXBP1) C. elegans models demonstrate that 4-phenylbutyrate (4-PBA) or related pharmacological chaperones stabilize Munc18-1 protein levels and rescue locomotion deficits. These studies suggest a novel treatment strategy for these patients. Here, we used a stxbp1a zebrafish model with a profound movement disorder to screen 4-PBA and alternative structural analogs identified using artificial intelligence (AI)-based screening. Automated locomotion assays conducted on larval stxbp1a mutant zebrafish at 5 days post-fertilization (dpf) confirm and extend the movement disorder endophenotype. Drug treatment (4-PBA or 16 identified candidates) failed to rescue the stxbp1a mutant zebrafish locomotion deficit. Electrophysiology studies in a stxbp1b zebrafish model characterized by spontaneous seizure activity (i.e., epilepsy) failed to detect a reduction in ictal-like events with 4-PBA treatment. Taken together, our results suggest caution in repurposing 4-PBA or related compounds for the treatment of STXBP1 disorders.
2026-06-09 | CRISPR-mediated Stxbp1 gene activation ameliorates epileptic and aggressive phenotypes in Stxbp1 -haploinsufficient mice
Abstract Mutations in the syntaxin-binding protein 1 ( STXBP1 ) gene, which encodes the presynaptic protein Munc18-1, cause a spectrum of severe epileptic encephalopathies and neurodevelopmental disorders, including Ohtahara syndrome, for which no curative treatment is currently available. Because the disease pathomechanism is thought to be driven by haploinsufficiency, restoring expression of the wild-type allele to physiological levels could provide therapeutic benefit. Here, we evaluated CRISPR-mediated transcriptional activation (CRISPR-ON), based on a dCas9-VPR transcriptional activator, as a strategy to upregulate endogenous Stxbp1 expression in a Stxbp1 -haploinsufficient ( Stxbp1 +/− ) mouse model. Screening of guide RNAs (gRNAs) targeting the Stxbp1 promoter in Neuro2A cells identified a multiplexed four-gRNA cassette that elevated Stxbp1 mRNA approximately six-fold. AAV-PHP.eB vectors co-expressing this 4xgRNA cassette and Cre recombinase under the EF1a promoter were administered intracerebroventricularly to neonatal Stxbp1 +/− /dCas9-VPR fl/+ mice. CRISPR-ON treatment restored not only brain Stxbp1 mRNA but also Munc18-1 protein levels to those of wild-type controls. Electrocorticographic recordings revealed an approximately 50% reduction in the frequency of spike-wave discharges in CRISPR-ON–treated Stxbp1 +/− mice compared with untreated Stxbp1 +/− controls, and aggressive behavior in the resident-intruder test was also partially attenuated. In contrast, locomotor activity remained unaffected, indicating that CRISPR-ON treatment achieves selective rescue of disease-related phenotypes without inducing motor side effects. Together, these findings demonstrate that CRISPR-ON–mediated activation of endogenous Stxbp1 is a promising therapeutic strategy for STXBP1 -related encephalopathies and support endogenous gene activation as a broadly applicable platform for haploinsufficiency disorders.
2026-02-28 | Cognitive and Motor Dysfunction in STXBP1 R406H Mice.
The STXBP1 protein critically regulates synaptic vesicle fusion and neurotransmitter release, with its mutations implicated in neurodevelopmental disorders. STXBP1 R406H can lead to the occurrence of early-onset epileptic encephalopathy (EOEE). To better elucidate the molecular mechanisms underlying pathogenesis，we generated an STXBP1 R406H mutation mouse model that recapitulated key cognitive-social deficits observed in patients. Behavioral and transcriptomic analyses revealed synaptic impairments and glial activation in mutant mice. Specifically, there is abnormal expression of synaptic proteins in hippocampal neurons, which are correlated with cognitive and motor deficits. Our study establishes that the STXBP1 R406H mutation drives neurodevelopmental pathology via excitatory synaptic dysfunction, offering new mechanistic insights and therapeutic avenues for the treatment of STXBP1-related disorders.
2025-12-16 | Infantile Spasms (West Syndrome): Integrating Genetic, Neurotrophic, and Hormonal Mechanisms Toward Precision Therapy
Background and Objectives: Infantile spasms (ISs), or West syndrome (WS), represent an early-onset epileptic encephalopathy in which diverse structural, genetic, metabolic, infectious, and neurocutaneous conditions converge on a shared pattern of hypsarrhythmia, clustered spasms, and later developmental impairment. Growing use of genomic diagnostics has revealed that variants in STXBP1, KCNQ2, GRIN2A, GRIN2B, and TSC-related genes are more common than previously recognized and can be linked to partially actionable pathways. This review aimed to synthesize current evidence on the multifactorial etiology, network-based pathogenesis, and evolving targeted therapies for ISs, with particular attention to TSC-related forms. Materials and Methods: A structured narrative review was undertaken of publications from 1990 to 2025 in PubMed, Scopus, Web of Science, and Embase using terms related to ISs, WS, genetics, mTOR, ACTH, vigabatrin, ketogenic diet, and precision therapies. Authoritative guidance from ILAE and AAN was incorporated. Clinical, molecular, and therapeutic data were grouped under etiological, pathogenetic, and management domains. Results: Structural causes remained the largest group, but combined genetic, genetic–structural, and metabolic etiologies accounted for about one third of contemporary cohorts. Early network disruption involving cortex, thalamus, basal ganglia, and brainstem, together with imbalances in NGF, BDNF, and IGF-1, explained why distinct primary insults produce a uniform electroclinical phenotype. Early treatment with ACTH or high dose prednisolone, with or without vigabatrin, was consistently associated with higher electroclinical remission and better developmental outcome. Everolimus and related mTOR inhibitors showed benefit in TSC-associated ISs, while agents directed at NMDA receptors or KCNQ channels are emerging for genotype defined subgroups. Conclusions: ISs should be approached as a heterogeneous but mechanistically convergent disorder in which rapid diagnosis, parallel genetic testing, and early disease modifying therapy improve prognosis. Integration of molecular profiling with standardized outcome monitoring is likely to move management from symptomatic seizure control to pathway-specific intervention.
2025-08-10 | EpiPred: A gene-specific machine learning model for classifying missense variants in the epilepsy-related gene STXBP1
ABSTRACT Missense variants in the STXBP1 gene are a frequent cause of early-onset developmental and epileptic encephalopathies and related neurodevelopmental disorders, but the clinical interpretation of these variants remains a major challenge. Most reported STXBP1 missense variants are classified as variants of uncertain significance (VUS), complicating diagnosis, counseling, and patient eligibility for precision therapies. Here, we developed EpiPred, a gene-specific machine learning classifier that predicts the pathogenicity of STXBP1 missense variants by integrating computational features with empirical evidence from cellular assays. Trained on a curated set of pathogenic and benign variants, EpiPred outperformed leading global prediction tools in accuracy, sensitivity, and specificity. We validated the model’s predictions using functional assays that measure protein abundance, solubility, stability, and interaction with the SNARE complex partner syntaxin 1. These biochemical readouts aligned closely with model outputs and enabled reclassification of several likely misdiagnosed variants. We deployed EpiPred in an interactive web application that allows clinicians, researchers, and patients to explore predictions for all possible missense variants in STXBP1. Our approach illustrates the power of gene-specific predictive modeling combined with experimental validation to improve variant interpretation and diagnostic resolution. By identifying likely pathogenic STXBP1 variants, including those that may respond to emerging therapies such as molecular chaperones, EpiPred supports more precise genetic diagnoses and offers a generalizable framework for other clinically relevant genes in neurological disease. ONE SENTENCE SUMMARY EpiPred improves STXBP1 variant interpretation, enabling precision genetic diagnoses and promoting access to targeted precision therapies
2026-06-10 | Virtual Screening and Zebrafish Phenotype-Based Evaluation Argues Against Repurposing 4-Phenylbutyrate for STXBP1-Related Disorders.
Syntaxin-binding protein 1 (STXBP1) mutations lead to severe epilepsy, intellectual disability, developmental delay, and movement disorder. Effective treatments for these conditions do not exist. Recent studies in Munc18-1 (STXBP1) C. elegans models demonstrate that 4-phenylbutyrate (4-PBA) or related pharmacological chaperones stabilize Munc18-1 protein levels and rescue locomotion deficits. These studies suggest a novel treatment strategy for these patients. Here, we used a stxbp1a zebrafish model with a profound movement disorder to screen 4-PBA and alternative structural analogs identified using artificial intelligence (AI)-based screening. Automated locomotion assays conducted on larval stxbp1a mutant zebrafish at 5 days post-fertilization (dpf) confirm and extend the movement disorder endophenotype. Drug treatment (4-PBA or 16 identified candidates) failed to rescue the stxbp1a mutant zebrafish locomotion deficit. Electrophysiology studies in a stxbp1b zebrafish model characterized by spontaneous seizure activity (i.e., epilepsy) failed to detect a reduction in ictal-like events with 4-PBA treatment. Taken together, our results suggest caution in repurposing 4-PBA or related compounds for the treatment of STXBP1 disorders.
2026-06-09 | CRISPR-mediated Stxbp1 gene activation ameliorates epileptic and aggressive phenotypes in Stxbp1 -haploinsufficient mice
Abstract Mutations in the syntaxin-binding protein 1 ( STXBP1 ) gene, which encodes the presynaptic protein Munc18-1, cause a spectrum of severe epileptic encephalopathies and neurodevelopmental disorders, including Ohtahara syndrome, for which no curative treatment is currently available. Because the disease pathomechanism is thought to be driven by haploinsufficiency, restoring expression of the wild-type allele to physiological levels could provide therapeutic benefit. Here, we evaluated CRISPR-mediated transcriptional activation (CRISPR-ON), based on a dCas9-VPR transcriptional activator, as a strategy to upregulate endogenous Stxbp1 expression in a Stxbp1 -haploinsufficient ( Stxbp1 +/− ) mouse model. Screening of guide RNAs (gRNAs) targeting the Stxbp1 promoter in Neuro2A cells identified a multiplexed four-gRNA cassette that elevated Stxbp1 mRNA approximately six-fold. AAV-PHP.eB vectors co-expressing this 4xgRNA cassette and Cre recombinase under the EF1a promoter were administered intracerebroventricularly to neonatal Stxbp1 +/− /dCas9-VPR fl/+ mice. CRISPR-ON treatment restored not only brain Stxbp1 mRNA but also Munc18-1 protein levels to those of wild-type controls. Electrocorticographic recordings revealed an approximately 50% reduction in the frequency of spike-wave discharges in CRISPR-ON–treated Stxbp1 +/− mice compared with untreated Stxbp1 +/− controls, and aggressive behavior in the resident-intruder test was also partially attenuated. In contrast, locomotor activity remained unaffected, indicating that CRISPR-ON treatment achieves selective rescue of disease-related phenotypes without inducing motor side effects. Together, these findings demonstrate that CRISPR-ON–mediated activation of endogenous Stxbp1 is a promising therapeutic strategy for STXBP1 -related encephalopathies and support endogenous gene activation as a broadly applicable platform for haploinsufficiency disorders.
2026-02-28 | Cognitive and Motor Dysfunction in STXBP1 R406H Mice.
The STXBP1 protein critically regulates synaptic vesicle fusion and neurotransmitter release, with its mutations implicated in neurodevelopmental disorders. STXBP1 R406H can lead to the occurrence of early-onset epileptic encephalopathy (EOEE). To better elucidate the molecular mechanisms underlying pathogenesis，we generated an STXBP1 R406H mutation mouse model that recapitulated key cognitive-social deficits observed in patients. Behavioral and transcriptomic analyses revealed synaptic impairments and glial activation in mutant mice. Specifically, there is abnormal expression of synaptic proteins in hippocampal neurons, which are correlated with cognitive and motor deficits. Our study establishes that the STXBP1 R406H mutation drives neurodevelopmental pathology via excitatory synaptic dysfunction, offering new mechanistic insights and therapeutic avenues for the treatment of STXBP1-related disorders.
2025-12-16 | Infantile Spasms (West Syndrome): Integrating Genetic, Neurotrophic, and Hormonal Mechanisms Toward Precision Therapy
Background and Objectives: Infantile spasms (ISs), or West syndrome (WS), represent an early-onset epileptic encephalopathy in which diverse structural, genetic, metabolic, infectious, and neurocutaneous conditions converge on a shared pattern of hypsarrhythmia, clustered spasms, and later developmental impairment. Growing use of genomic diagnostics has revealed that variants in STXBP1, KCNQ2, GRIN2A, GRIN2B, and TSC-related genes are more common than previously recognized and can be linked to partially actionable pathways. This review aimed to synthesize current evidence on the multifactorial etiology, network-based pathogenesis, and evolving targeted therapies for ISs, with particular attention to TSC-related forms. Materials and Methods: A structured narrative review was undertaken of publications from 1990 to 2025 in PubMed, Scopus, Web of Science, and Embase using terms related to ISs, WS, genetics, mTOR, ACTH, vigabatrin, ketogenic diet, and precision therapies. Authoritative guidance from ILAE and AAN was incorporated. Clinical, molecular, and therapeutic data were grouped under etiological, pathogenetic, and management domains. Results: Structural causes remained the largest group, but combined genetic, genetic–structural, and metabolic etiologies accounted for about one third of contemporary cohorts. Early network disruption involving cortex, thalamus, basal ganglia, and brainstem, together with imbalances in NGF, BDNF, and IGF-1, explained why distinct primary insults produce a uniform electroclinical phenotype. Early treatment with ACTH or high dose prednisolone, with or without vigabatrin, was consistently associated with higher electroclinical remission and better developmental outcome. Everolimus and related mTOR inhibitors showed benefit in TSC-associated ISs, while agents directed at NMDA receptors or KCNQ channels are emerging for genotype defined subgroups. Conclusions: ISs should be approached as a heterogeneous but mechanistically convergent disorder in which rapid diagnosis, parallel genetic testing, and early disease modifying therapy improve prognosis. Integration of molecular profiling with standardized outcome monitoring is likely to move management from symptomatic seizure control to pathway-specific intervention.
2025-08-10 | EpiPred: A gene-specific machine learning model for classifying missense variants in the epilepsy-related gene STXBP1
ABSTRACT Missense variants in the STXBP1 gene are a frequent cause of early-onset developmental and epileptic encephalopathies and related neurodevelopmental disorders, but the clinical interpretation of these variants remains a major challenge. Most reported STXBP1 missense variants are classified as variants of uncertain significance (VUS), complicating diagnosis, counseling, and patient eligibility for precision therapies. Here, we developed EpiPred, a gene-specific machine learning classifier that predicts the pathogenicity of STXBP1 missense variants by integrating computational features with empirical evidence from cellular assays. Trained on a curated set of pathogenic and benign variants, EpiPred outperformed leading global prediction tools in accuracy, sensitivity, and specificity. We validated the model’s predictions using functional assays that measure protein abundance, solubility, stability, and interaction with the SNARE complex partner syntaxin 1. These biochemical readouts aligned closely with model outputs and enabled reclassification of several likely misdiagnosed variants. We deployed EpiPred in an interactive web application that allows clinicians, researchers, and patients to explore predictions for all possible missense variants in STXBP1. Our approach illustrates the power of gene-specific predictive modeling combined with experimental validation to improve variant interpretation and diagnostic resolution. By identifying likely pathogenic STXBP1 variants, including those that may respond to emerging therapies such as molecular chaperones, EpiPred supports more precise genetic diagnoses and offers a generalizable framework for other clinically relevant genes in neurological disease. ONE SENTENCE SUMMARY EpiPred improves STXBP1 variant interpretation, enabling precision genetic diagnoses and promoting access to targeted precision therapies
Access all drug discovery papers and probability of success in trials forecasts:
Access all drug discovery papers and probability of success in trials forecasts:
Drug Discovery Landscape
2 orphan drug designations for STXBP1-related encephalopathy.
2 orphan drug designations for STXBP1-related encephalopathy.
Drug | Therapy type | Regulator | Orphan designation | Approval | Sponsor |
|---|---|---|---|---|---|
recombinant adeno-associated virus capsid enclosing a single-stranded DNA construct encoding human STXBP1 transgene | gene therapies | FDA | 2024-10-19 | — | Capsida Biotherapeutics |
Glycerol phenylbutyrate | small molecules | EMA | 2023-10-13 | — | Immedica Pharma AB |
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