AT-007 in Adult Subjects With Classic Galactosemia (CG)

An Open-Label Study to Evaluate the Long-Term Safety and Pharmacodynamic Efficacy of AT-007 in Adult Subjects With Classic Galactosemia (CG)

This study is a 12-month open-label extension (OLE) study of AT-007 in adult subjects with CG who previously participated in Study AT-007-1001 Part D and/or Part D Extension. The study is designed to assess the long-term safety of AT-007 in subjects with CG as well as the pharmacodynamics (PD) (inhibition of galactitol) and PK of AT-007. The effect of 12-month treatment with AT-007 on the levels of galactose and other galactose metabolites in subjects with CG will also be evaluated.

Primary: - To evaluate the long-term safety of 12-month oral administration of AT-007 in adult subjects with Classic Galactosemia (CG) Secondary: To evaluate the long-term inhibition of galactitol, a biomarker of aldose reductase (AR) activity, induced by 12-month oral administration of AT-007 to adult subjects with CG To evaluate the pharmacokinetic (PK) parameters of 12-month oral administration of AT-007 in adult subjects with CG Exploratory: To evaluate the effect of 12-month oral administration of AT-007 on the levels of galactose and its other metabolites in adult subjects with CG To evaluate the burden of illness (BOI) of adult subjects with CG To evaluate quality of life (QOL) measures of adult subjects with CG To evaluate the effect of 12-month oral administration of AT-007 on the BOI and QOL of adult subjects with CG

To evaluate the long-term safety of 12-month oral administration of AT-007 in adult subjects with CG as assessed by adverse events.

Number of participants with treatment-emergent adverse events and broken down by organ class and relatedness.

To evaluate the long-term safety of 12-month oral administration of AT-007 in adult subjects with CG as assessed by clinical laboratory test results.

To evaluate the long-term safety of 12-month oral administration of AT-007 in adult subjects with CG as assessed by physical exam parameters.

Number of participants with clinically-significant changes in physical examination findings, vital sign abnormalities, and electrocardiogram findings.

To evaluate the long-term change of galactitol, a biomarker of AR activity, induced by 12-month oral administration of AT-007 to adult subjects with CG

To evaluate the pharmacokinetic (PK) parameter maximum concentration (Cmax) of 12-month oral administration of AT-007 in adult subjects with CG

To evaluate the pharmacokinetic (PK) parameter Area-Under-the-Curve (AUC) of 12-month oral administration of AT-007 in adult subjects with CG (mg*h/L)

To evaluate the effect of 12-month oral administration of AT-007 on the levels of galactose and its other metabolites in adult subjects with CG

Narrative description of natural course of CG as extracted by chart review and physical exam findings noted in chart review including the baseline neurologic exam upon entering the clinical trial. (There are no units for a descriptive narrative of medical history)

NIH Motor Battery produces normalized percentile scores with higher scores being more normal. As an exploratory endpoint, changes in the score from baseline to month 12 will assessed.

Spiral Drawing Test produces normalized percentile scores with higher scores being more normal. As an exploratory endpoint, changes in the score from baseline to month 12 will assessed.

To evaluate quality of life (QOL) measures of adult subjects with CG- PROMIS Emotional Distress questionnaire

The questionnaire assesses this function with higher scores relating to better function and may be used to compare over time for change from baseline to month 12. [PROMIS: Patient Reported Outcome Measure Information System]

To evaluate quality of life (QOL) measures of adult subjects with CG- PROMIS Emotional Support questionnaire

The questionnaire assesses this function with higher scores relating to better function and may be used to compare over time for change from baseline to month 12. [PROMIS: Patient Reported Outcome Measure Information System]

To evaluate quality of life (QOL) measures of adult subjects with CG- PROMIS Companionship questionnaire

The questionnaire assesses this function with higher scores relating to better function and may be used to compare over time for change from baseline to month 12. [PROMIS: Patient Reported Outcome Measure Information System]

To evaluate quality of life (QOL) measures of adult subjects with CG- PROMIS Social Isolation questionnaire

The questionnaire assesses this function with higher scores relating to better function and may be used to compare over time for change from baseline to month 12. [PROMIS: Patient Reported Outcome Measure Information System]

To evaluate quality of life (QOL) measures of adult subjects with CG- PROMIS Ability to Participate in Social Roles and Activities questionnaire

The questionnaire assesses this function with higher scores relating to better function and may be used to compare over time for change from baseline to month 12. [PROMIS: Patient Reported Outcome Measure Information System]

Inclusion Criteria: Male or non-pregnant, non-lactating female subject with a CG diagnosis Previous participation in Study AT-007-1001 Part D and/or Part D Extension No other significant health problems which preclude participation Exclusion Criteria: Concomitant use of certain medications or over-the-counter therapies Discontinuation from Study AT-007-1001 Part D and/or Part D Extension due an adverse event