MDS-UPDRS Part III was used to assess the motor signs of Parkinson's disease. It was comprised of 33 sub-scores based on 18 items, several with right, left or other body distribution scores. Each question was anchored with 5 responses that were linked to commonly accepted clinical terms: 0=normal, 1=slight, 2=mild, 3=moderate, and 4=severe. The MDS-UPDRS Part III total score range is 0-132. Higher score indicates more severe motor signs of Parkinson's disease. A negative change from baseline represents an improvement in motor function.

All participants who received at least 1 dose of study treatment (PF-06649751 or placebo) and had a baseline and Week 15 MDS-UPDRS score Part III.

An AE was any untoward medical occurrence in a participant who received study treatment without regard to possibility of causal relationship. An SAE was an AE resulting in any of the following outcomes or deemed significant for any other reason: death; life-threatening (immediate risk of death); initial or prolonged inpatient hospitalization; persistent or significant disability/incapacity; congenital anomaly/birth defect. Treatment-emergent AEs were those with initial onset or increasing in severity after the first dose of study treatment.

All participants who received at least 1 dose of study treatment (PF-06649751 or placebo).

Following safety laboratory parameters were assessed against pre-defined abnormality criteria: hematology (hemoglobin, hematocrit, red blood cell count, mean corpuscular volume, mean corpuscular hemoglobin, mean corpuscular hemoglobin concentration, platelet count, white blood cell count, absolute total neutrophils, absolute eosinophils, absolute basophils, absolute monocytes, and absolute lymphocytes); chemistry (blood urea nitrogen/urea and creatinine, glucose , calcium, sodium, potassium, chloride, total bicarbonate, aspartate aminotransferase [AST], alanine aminotransferase [ALT], total bilirubin, alkaline phosphatase, uric acid, albumin, total protein); urinalysis (pH, qualitative glucose, qualitative protein, qualitative blood, ketones, nitrites, leukocyte esterase, urine bilirubin, urobilinogen, urine creatinine, microscopy, and specific gravity).

All participants who received at least 1 dose of study treatment (PF-06649751 or placebo) and had at least 1 observation of the given laboratory test.

Vital signs categorical summarization criteria: 1) supine and standing systolic blood pressure (SBP) <90 millimeters of mercury (mmHg); 2) supine and standing diastolic blood pressure (DBP) <50 mmHg; 3) supine pulse rate <40 or >120 beats per minute (bpm); 4) standing pulse rate <40 or >140 bpm; 5) maximum change from baseline (increase or decrease) in supine and standing DBP greater than or equal to (>=) 20 mmHg; 6) maximum change from baseline (increase or decrease) in supine and standing SBP >=30 mmHg. Orthostatic hypotension criterion was defined as a decrease of >=20 mmHg for SBP or >=10 mmHg for DBP 2 minutes after standing from a supine position.

All participants who received at least 1 dose of study treatment (PF-06649751 or placebo).

ECG categorical summarization criteria: 1) QRS duration (time from ECG Q wave to the end of the S wave corresponding to ventricle depolarization): >=140 milliseconds (msec), >=50% increase from baseline; 2) PR interval (the interval between the start of the P wave and the start of the QRS complex, corresponding to the time between the onset of the atrial depolarization and onset of ventricular depolarization): >=300 msec, >=25% increase when baseline is > 200 msec or >=50% increase when baseline is less than or equal to (<=) 200 msec; 3) QT interval (time from ECG Q wave to the end of the T wave corresponding to electrical systole): absolute value of >=500 msec; 4) QTcF interval (QT corrected for heart rate using Fridericia's formula): absolute value of 450 to <480 msec, 480 to <500 msec, >=500 msec; an increase from baseline of 30 to <60 msec or >=60 msec.

All participants who received at least 1 dose of study treatment (PF-06649751 or placebo). "Number Analyzed" represents the number of participants evaluable for each specified category.

The C-SSRS is an interview based rating scale to systematically assess suicidal ideation and suicidal behavior. C-SSRS responses were mapped to the Columbia Classification Algorithm of Suicide Assessment (C-CASA). Participants with new onset suicidality were those without suicidal ideation and behavior at baseline and reported any suicidal behavior or ideation post-baseline as assessed by C-CASA code mapped from C-SSRS data. Participants with worsening suicidality were those who moved to a lower numbered C-CASA category than was reported at baseline.

All participants who received at least 1 dose of study treatment (PF-06649751 or placebo).

The QUIP-RS has 4 primary questions pertaining to commonly reported thoughts, urges/desires, and behaviors associated with impulsive-compulsive disorder , each applied to the 4 impulsive-compulsive disorders (compulsive gambling, buying, eating, and sexual behavior) and 3 related disorders (medication use, punding, and hobbyism). Each question is anchored with the following 5 responses: Never (0), Rarely (1), Sometimes (2), Often (3), and Very Often (4). The scoring range for each item (ie, disorder) is 0-16. The QUIP-RS total score range is 0-64. Higher score indicates a greater level of the impulsive compulsive disorder.

All participants who received at least 1 dose of study treatment (PF-06649751 or placebo). "Number Analyzed" = Participants evaluable for this outcome measure at specified time points.

The PWC-20 is a 20-item reliable and sensitive instrument for the assessment of benzodiazepine-like discontinuation symptoms. The total PWC-20 score is the sum of 20 item scores and ranges between 0 and 60. The higher score indicates more frequent/severe symptoms.

All participants who received at least 1 dose of study treatment (PF-06649751 or placebo) and had PWC-20 evaluation.