Effect of PBT2 in Patients With Early to Mid Stage Huntington Disease

Change From Baseline in Cognitive Test Battery - Composite z Scores

Cognition composite z-scores were calculated for each participant. The composite scores were defined as the mean of the individual z-scores for the various cognition assessments. The Main Composite z-score was calculated for Category Fluency Test, Trail Making Test Part B, Map Search, Symbol Digit Modalities Test and Stroop Word Reading Test. The Exploratory Composite z-score was calculated for Category Fluency Test, Trail Making Test Part B, Map Search, Symbol Digit Modalities Test, Stroop Word Reading Test and Speeded Tapping test. The Executive Function Composite z-score was calculated from Category Fluency Test and Trail Making Test Part B. There is no unit of measure for the z score as it is the pure number calculated from the SD from the mean. A higher z score indicates an improvement.

Time frame: Baseline to 26 weeks

Change From Baseline in Motor Function

Total motor score calculated from the Unified Huntington Disease Rating Scale - Motor Function. The motor section of the UHDRS assesses motor features of HD with standardized ratings of oculomotor function, dysarthria, chorea, dystonia, gait, and postural stability. The total motor impairment scores is the sum of all the individual motor ratings, with higher scores indicating more severe motor impairment than lower scores. A maximum score of 60 is possible (range 0-60).

Time frame: Baseline to 26 weeks

Change From Baseline in Functional Abilities

Total Functional Capacity (TFC) assessment was based on an individual's ability to perform common daily tasks. TFC score range was 0 to 13. Higher scores on the function scales indicate better functioning than lower scores.

Time frame: Baseline to 26 weeks

Change From Baseline in Behaviour

Total Behavioural score from the Unified Huntington Disease Rating Scale. The behavioural assessment measures the frequency and severity of symptoms related to affect, thought content and coping styles. The total behaviour score is the sum of all responses, with scale range of 0 to 8. Higher scores on the behaviour assessments indicate more severe disturbance than lower scores.

Time frame: Baseline to 26 weeks

Change From Baseline in Investigator Global Assessments by Efficacy Index

Global function was assessed by the Investigator using the clinical global impression (CGI) scale which included assessing the severity of illness and global improvement and calculating the efficacy index for each participant. The efficacy index aims to relate therapeutic effects to reported side effects as assessed by the Investigator (range from 0 \[marked improvement and no side effects\] to 4 \[unchanged or worse\] and side effects outweigh therapeutic effects) and is calculated for each participant by dividing the therapeutic effect score by the side effects score. An improvement is reflected by CGI scale Efficacy Index values \>1.

Time frame: Baseline to 26 weeks

Change From Baseline in Blood Biomarkers

Biomarkers assessed primarily with mutant huntingtin protein, normalised to lysate protein concentrations, as a change from baseline.

Time frame: Baseline to 26 weeks

Change From Baseline in Brain Function (MRI)

Measure of whole brain iron concentrations.

Time frame: Baseline to 26 weeks

Change From Baseline in Blood Biomarkers

Biomarkers assessed primarily with soluble huntingtin protein, normalised to lysate protein concentrations, as a change from baseline.

Time frame: Baseline to 26 weeks

Change From Baseline in Blood Biomarkers - Selenium

Biomarkers assessed primarily with plasma selenium as a change from baseline.

Time frame: Baseline to 26 weeks

Change From Baseline in Urine Biomarkers

Biomarkers assessed primarily with 8-hydroxy-2'-deoxyguanosine, normalised to creatinine concentrations, as a change from baseline.

Time frame: Baseline to 26 weeks

Change From Baseline in Brain Function (MRI)

Measure of the structural brain volume as assessed by the left caudate volume.

Time frame: Baseline to 26 weeks

Change From Baseline in Cognitive Test Battery - TMT Part B

Trail Making Test Part B was assessed by the number of seconds to complete the test (from 0 to 240 seconds). The Trails Making Test Part B actual change from baseline at Week 26 was analysed.

Time frame: Baseline to 26 weeks