CBDV vs Placebo in Children and Adults up to Age 30 With Prader-Willi Syndrome (PWS)

Repetitive behavior will be evaluated using the RBS-R. RBS-R is a 43-item self-report questionnaire used to measure the breadth or repetitive behaviors in children, adolescents, and adults with ASD. The RBS-R consists of 6 subscales: Stereotyped Behavior, Self-injurious Behavior, Compulsive Behavior, Ritualistic Behavior, Sameness Behavior, and Restricted Behavior that have no overlap of item content. Each of the 43 items are rated on a 4-point Likert scale ranging from 0 ("Behavior does not occur") to 3 ("Behavior occurs and is a severe problem"), yielding an overall scoring range of 0-129, such that higher scores are associated with increased severity of the problem behavior. RBS-R scores for Week 4, Week 8, and Week 12 are summarized in the table by study arm using descriptive statistics. Baseline results for this outcome can be found in the Baseline Characteristics module.

Obsessive-compulsive symptoms will be assessed using the CY-BOCS. The CY-BOCS is 10-item clinician-rated measure designed to assess the severity of obsessive-compulsive symptoms in children/adolescents over the prior week. It consists of 5 primary sections: Time, Distress, Interference, Resistance, and Control of Symptoms. The 10 items are rated on a scale from 0 ("No symptoms") to 4 ("Extreme symptoms"), for an overall possible range of 0-40, with higher scores indicative of greater severity of symptoms. CY-BOCS scores for Week 4, Week 8, and Week 12 are summarized by study arm using descriptive statistics. Baseline results for this outcome can be found in the Baseline Characteristics module.

Hyperphagia will be assessed using the Hyperphagia Questionnaire for Clinical Trials (HQ-CT). The HQ-CT is a 9-item caregiver-reported measure of the frequency and intensity of food-seeking behaviors in participants with Prader-Willi Syndrome (PWS) over the prior two-week period. The 9 items are graded on a Likert scale ranging from 0 ("No Hyperphagia") to 4 ("Most severe hyperphagia"), yielding an overall possible scoring range of 0-36, with higher scores indicating greater, more severe hyperphagia. HQ-CT scores for Week 4, Week 8, and Week 12 are summarized by study arm using descriptive statistics. Baseline results for this outcome can be found in the Baseline Characteristics module.

Global Functioning will be assessed using the Clinical Global Impression Scale - Improvement (CGI-I). The CGI-I is a global assessment which measures the change in a participant's illness severity, relative to a baseline, considering all symptoms, behaviors, and functional impairment. It consists of a 7-point clinician-rated scale as follows: 1 = very much improved, 2 = much improved, 3 = minimally improved, 4 = no change, 5 = minimally worse, 6 = much worse, 7 = very much worse. such that higher scores are indicative of worsening global function. CGI-I scores for Week 4, Week 8, and Week 12 are summarized by study arm using basic descriptive statistics.

Caregiver Strain will be evaluated using the Caregiver Strain Questionnaire (CSQ). The CSQ is a 21-item self-report questionnaire, consisting of 3 subscales, developed to assess caregiver strain/stress for families with a child living with an emotional or behavioral disorder. Items 1-11 assess Objective Strain. Items 12, 16-18, and 20-21 assess Subjective Internalized Strain. Items 13-15, and 19 assess Subjective Externalize Strain. All CSQ items are rated from 1 ("Not at all a problem") to 5 ("Very much a problem"). Scores are calculated by averaging items within each subscale to handle missing data and calculating a Global Score by summing the 3 subscale means for a total possible scale range of 3-15. Higher Global Scores are associated with increased Caregiver Strain. Global results scores for Week 4, Week 8, and Week 12 are summarized by study arm using descriptive statistics. Baseline results for this outcome can be found in the Baseline Characteristics module.

Rigid behavior will be assessed based using the MERS-R-PWS. The MERS-R-PWS is a clinician-rated scale designed to assess 3 domains of rigid behavior in individuals with PWS:

Behavioral Rigidity (e.g., Insistence on sameness, things must be done in his/her way, etc.) Cognitive Rigidity (e.g., Special interests, inflexible adherence to rules, etc.) Protest (in response to deviation from rigidity; e.g., tantrum, irritability, arguing)

Each domain consists of 4 items rated on a 5-point scale ranging from 0 ("No/None/Not difficult") to 4 ("Extreme/Extremely Difficult"), yielding a range of 0-16. Scores at Week 12 will only be completed for subjects who display rigid behaviors at baseline, week 4, week 8 and week 12. A total MERS-R-PWS score (0-48) is obtained by summing subscale score. Individual subscale scores (0-16) are also summarized. Higher MERS-R-PWS scores are indicative of greater rigidity within each domain and overall rigidity.

Aberrant Behavior will be assessed using the Aberrant Behavior Checklist (ABC). The ABC is a 58-item informative rating instrument used to measure maladaptive behaviors in individuals with developmental disabilities and ASD which resolves into 5 subscales: Irritability (15 items); Lethargy/Social withdrawal (16 items); Stereotypic behavior (7 items); Hyperactivity/noncompliance (16 items); and Inappropriate speech (4 items). The ABC is completed by a parent/caregiver who knows the participant well. The ABC measures behavior on a 4-point Likert severity scale: (0 = "Not all a problem," 1 = "Slight problem," 2 = "Moderately serious problem," and 3 = "Severe problem"). Scores for 4 of the 5 subscales are reported below (ABC-I results reported as part of the primary outcome). Higher ABC subscale scores indicate greater behavioral severity/dysfunction of that subscale. Week 4, Week 8, and Week 12 scores are summarized by study arm. See Baseline Characteristics module for baseline data.

Sleep quality will be assessed using ActiGraph GT9X-BT® activity monitors. Successfully screened patients will receive the actigraphy device prior to the onsite baseline visit and will record a minimum of three days of baseline activity data prior to study initiation. The ActiGraph GT9X-BT activity monitors are a well validated activity and sleep monitoring device widely utilized in clinical trials and health research. For this study the ActiGraph monitors will measure: Sleep Latency (the time it takes to fall asleep), Total Sleep Time (the total amount of time spent asleep), and sleep efficiency (percentage of time in bed actually spent sleeping). Sleep data is captured automatically via cloud service. All parameters will be reported in hours/minutes and summarized by study arm.