Study Evaluating The Safety, Tolerability And Brain Function Of 2 Doses Of PF-0254920 In Subjects With Early Huntington's Disease

An AE was any untoward medical occurrence without regard to causality in a participant who received study drug. An SAE was an AE resulting in any of the following outcomes or deemed significant for any other reason: death; initial or prolonged inpatient hospitalization; life-threatening experience (immediate risk of dying); persistent or significant disability/incapacity; congenital anomaly. Treatment-emergent are events between first dose of treatment and up to the follow-up period that were absent before treatment or that worsened relative to pretreatment state. AEs included both SAEs and non-serious AEs.

The following laboratory parameters were analyzed: hematology (hemoglobin, hematocrit, red blood cell [RBC] count, platelet count, white blood cell [WBC] count, total neutrophils, eosinophils, monocytes, basophils, lymphocytes); blood chemistry (blood urea nitrogen [BUN], creatinine, glucose, calcium, sodium, potassium, chloride, total bicarbonate, aspartate aminotransferase [AST], alanine aminotransferase [ALT], total and direct bilirubin, alkaline phosphatase, uric acid, albumin, and total protein; urinalysis (pH, glucose, protein/albumin, hemoglobin/blood, ketones/acetone, nitrites, leukocyte esterase, microscopy [if urine dipstick was positive for blood, protein, nitrites or leukocyte esterase]); others (urine/serum pregnancy test, glycosylated hemoglobin [HbA1c, if diabetic]).

Vital signs assessment included pulse rate and blood pressure. Criteria for vital sign values meeting potential clinical concern included: supine/sitting pulse rate less than (<)40 or greater than (>)120 beats per minute (bpm), standing pulse rate <40 or >140 bpm; systolic blood pressure (SBP) of greater than or equal to (>=)30 millimeters of mercury (mmHg) change from baseline or SBP <90 mmHg, diastolic blood pressure (DBP) >=20 mmHg change from baseline or DBP <50 mmHg.

ECG parameters included PR interval, QRS complex, and corrected QT interval using Fridericia's formula (QTcF). Criteria for ECG changes meeting potential clinical concern included: PR interval ≥200 milliseconds (msec) or ≥25% increase when baseline is >100 msec; QRS interval ≥50% increase from baseline when baseline is less than or equal to (<=)200 msec; and QTcF ≥450 msec or ≥30 msec increase from baseline.

Weight assessment was performed by a study physician or a trained study nurse and was included in the physical examination.

Absolute neutrophil count (ANC) and WBC were monitored for safety. Participants with WBC <3000 but >=2000 cells/mm^3 or ANC <1500 but >=1000 cells/mm^3 were to have study treatment suspended. Participants with WBC <2000 or ANC <1000 cells/mm^3 were to be discontinued from study participation.

The UHDRS is a clinical rating scale to provide a uniform assessment of the clinical features and course of Huntington Disease. The Total Motor Score (TMS) is 1 of the 6 components of UHDRS, includes 31 items, and ranges from a scale of 0 to 124 (higher scores indicate more severe disease).

C-SSRS is a participant rated questionnaire to assess suicidal ideation, suicidal behavior, actual attempts (yes or no responses), and intensity of ideation (rated 1=low severity to 5=high severity). Yes/No responses are mapped to Columbia Classification Algorithm of Suicide Assessment (C-CASA) categories: completed suicide, suicide attempt, preparatory acts towards imminent suicidal behavior, suicidal ideation, and self-injurious behavior, or no suicidal intent. A participant could have a yes or no response in more than 1 category.

C-SSRS is a participant rated questionnaire to assess suicidal ideation, suicidal behavior, actual attempts (yes or no responses), and intensity of ideation (rated 1=low severity to 5=high severity). Yes/No responses are mapped to Columbia Classification Algorithm of Suicide Assessment (C-CASA) categories: completed suicide, suicide attempt, preparatory acts toward imminent suicidal behavior, suicidal ideation, and self-injurious behavior, or no suicidal intent. A participant could have a yes or no response in more than 1 category.

C-SSRS is a participant rated questionnaire to assess suicidal ideation, suicidal behavior, actual attempts (yes or no responses), and intensity of ideation (rated 1=low severity to 5=high severity). Yes/No responses are mapped to Columbia Classification Algorithm of Suicide Assessment (C-CASA) categories: completed suicide, suicide attempt, preparatory acts toward imminent suicidal behavior, suicidal ideation, and self-injurious behavior, or no suicidal intent. A participant could have a yes or no response in more than 1 category.

The monetary incentive delay (MID) task is established as a reliable method to elicit ventral striatal (VS) activity in relation to reward/punishment anticipation and tracked with dysfunctionalities across a range of conditions in which incentive motivation is thought to be abnormal (schizophrenia, depression, substance abuse, and pathological gambling). Pharmacological intervention has demonstrated reversal of observed deficit. The beta contrast value of 'REW' is for analysis of reward-related activity in VS within the task-related 'reward network' during the gain condition (relative to neutral) of the MID task. The changes in beta contrasts (fMRI) provided are changes in parameter estimates and do not have a unit of measure.

This incentive force task was developed to independently dissociate the degree to which a participant responds to reward motivation versus emotional motivation. The task itself included 12 repetitions of 9 trial types, for a total of 108 trials, grouped in a single session lasting about 20 minutes. The trial types were generated according to a combination of 3 emotional categories (negative, neutral, and positive pictures presented) and to 3 monetary incentives (0.01, 0.1, and 1€). Emotional categories and monetary incentives were randomly distributed over the trials and the sequence was fixed such that all subjects were assessed on the exact same task. For each trial, the subject was first presented with an emotional picture displayed on screen for 3000 milliseconds (ms).