4-Phenylbutyrate rescues neurobehavioral phenotypes in SLC6A1-related encephalopathy

Developmental and epileptic encephalopathies (DEEs) caused by pathogenic variants in SLC6A1, encoding γ-aminobutyric acid (GABA) transporter 1 (GAT-1), present with seizures and severe comorbidities including cognitive impairment, developmental delay, motor difficulties, and social deficits. Current therapies focus on seizure reduction but do not address the disabling neurobehavioral symptoms. We previously showed that 4-phenylbutyrate (PBA), known as a chemical chaperone and histone deacetylase inhibitor, restores GAT-1 function and reduces seizures in both mouse models and humans with SLC6A1 variants. Here, we tested whether PBA can improve neurobehavioral deficits in the Slc6a1^+/S295L knock-in mouse model of DEE besides seizure mitigation. Longitudinal behavioral analysis revealed deficits in motor reflexes, locomotion, and sleep correlating patient comorbidities. Slc6a1^+/S295L mice exhibited prolonged righting reflexes in neonates and reduced locomotion at 1 month of age. In home cage monitoring, Slc6a1^+/S295L mice traveled less distance at 1 and 7 months; spent less time hanging at 1, 7, and 10 months; and showed changes in sleep patterns at 7 and 10 months. Acute treatment with intraperitoneal PBA (100 mg/kg/day for 7 days) improved travel at 1 month (27 %) and hanging at 1 month (35 %) and 7 months (24 %). Chronic oral PBA treatment (100 mg/kg/day for 28 days) at 7 months further improved hanging (56 %) and travel (16 %). Both acute and chronic PBA treatments increased sleep in the mutant mouse. These results demonstrate that PBA not only reduces seizures but also mitigates comorbidities including motor and behavioral outcomes in SLC6A1 DEE, supporting its potential as a disease-modifying therapy.