Novel Treatment & Screening Strategies in Gamma-Hydroxybutyric Aciduria

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DESCRIPTION (provided by applicant): Human succinic semialdehyde dehydrogenase (SSADH; aldehyde dehydrogenase 5a1 (Aldh5a1)) deficiency is a rare neurogenetic disorder affecting the GABA neurotransmitter system. Aldh5a1-/- mice manifest early absence seizures which evolve into lethal generalized convulsive epilepsy, similar to seizure phenotypes observed in the human disease. The investigators' long-term goals are to define an effective treatment strategy for patients and springboard that treatment into expanded newborn screening for SSADH deficiency. The investigators will work toward these goals via the following hypotheses and aims: Hypothesis 1 is that chronic application of SGS-742, an orally active GABAB receptor (GABABR) antagonist, to Aldh5a1-/- mice will prevent early lethality and normalize neuropharmacological abnormalities. Specific Aim 1 will characterize anthropormorphics, neuropharmacology, seizure threshold, and GABABR structure in Aldh5a1-/- mice treated with SGS-742. Hypothesis 2 is that SGS-742 intervention in adult SSADH-deficient patients will improve neuropsychological deficits and restore GABABR function downregulated by chronic exposure to supraphysiological GABA levels. Specific Aim 2 will be a pilot trial of SGS-742 in six adult SSADH-deficient patients using neuropsychiatric evaluations and transcranial magnetic stimulation (TMS; estimating GABABR function) as outcome measures. Hypothesis 3 is that guanidinobutyrate (GB), a GABA analogue elevated in SSADH-deficient physiological fluids, represents a reliable biomarker to identify SSADH deficiency in newborn bloodspots. Specific Aim 3 implements a pilot evaluation of newborn screening for SSADH deficiency that will establish normative ranges and sensitivity/specificity correlations. The design is cohort-control except for Aim 2, where each patient will serve as their own control. Accepted methodology is applied throughout (neuropharmacology, tandem mass spectrometry, neuropsychological batteries), although the use of noninvasive TMS in this disorder is novel.