424 Clinical Translational Approach to Targeted Therapy in SLC6A1-related Neurodevelopmental Disorder

Abstract

OBJECTIVES/GOALS: SLC6A1-Related Neurodevelopmental Disorder (SLC6A1-NDD) is a leading genetic cause of epilepsy and autism. Haploinsufficiency of SLC6A1 leads to reduced uptake of GABA from the synaptic cleft, and increased extracellular GABA in mice. It is a candidate for gene transfer therapy, but translational read outs are needed. EEG is a promising biomarker. METHODS/STUDY POPULATION: The SLC6A1-NDD program includes a specialty clinic and prospective cohort study run in parallel with pre-clinical gene therapy development. Characterization and pre-clinical testing of a homozygous knock-out, heterozygous knock-out, and two humanized knock-in models are on-going, including EEG analyses before and after treatment. Patients with a confirmed diagnosis of SLC6A1-NDD are seen annually in a specialty clinic and a subset participate in the cohort study which collects standardized questionnaires, EEGs, and MR Spectroscopy to measure glutamate and GABA. Gene Therapy Program investigators meet weekly to discuss progress on pre-clinical and clinical trial readiness on SLC6A1-NDD and to align efforts on translational read outs, including EEG, in both humans and the pre-clinical models. RESULTS/ANTICIPATED RESULTS: We have enrolled the full cohort of 20 participants in the prospective SLC6A1-NDD cohort study. Preliminary results have shown that all but 1 individual has a history of developmental delay, and 8 of the 24 individuals in our clinical cohort had at least one episode of developmental regression. Over 90% have epilepsy, and 17/20 in the cohort study have intermittent rhythmic delta activity on EEG. The full knock out mice have behavioral and learning deficits and abnormal electrical brain activity on telemetry, including bursts of spike trains, analogous to epileptiform activity seen in humans. Next steps include quantitative analysis of both mouse and human EEG to develop a translational brain-based biomarker. We plan to assess delta power and investigate genotype-phenotype correlations in mice and humans. DISCUSSION/SIGNIFICANCE: With targeted therapies in development for SLC6A1-NDD, translational biomarkers that demonstrate engagement with the brain are critical. With clinical heterogeneity in SLC6A1-NDD, biomarkers can objectively capture change. Collaborative translational projects may improve efficiency in rare disease research to facilitate early phase trials.