Safety and Pharmacokinetics of AT-007 in Healthy Subjects and in Adult Subjects With Classic Galactosemia

Inclusion Criteria: * Diagnosis of Classic Galactosemia confirmed by evidence of absent or significantly decreased (\<1%) GALT activity in red blood cells and by GALT gene analysis * Urine galactitol \>100 mmol/mol creatinine * Galactose-restricted diet Exclusion Criteria: * Complications of CG resulting in disability that, in the opinion of the Investigator, may prevent the subject from completing all study requirements (e.g., severe neurological deficits, severe cognitive impairment, or severe language difficulty). * Renal disease (eGFR \< 90 mL/min/1.73 m2 or albuminuria).