Inclusion Criteria
1. Male or Female outpatients aged 5 to 30 years.
2. Diagnosis of PWS confirmed by genetic testing and patient medical records and history.
3. Stable pharmacologic, educational, behavioral and/or dietary interventions for 4 weeks prior to the study start, and for the duration of the study.
4. Have a physical exam and laboratory results that are within the norms for PWS
5. Presence of a parent/caregiver/guardian that is able to consent for their participation and complete assessments regarding the patient's development and behavior throughout the study. Child Assent will be obtained if the subject is 7 years of age or older and has the mental capacity to understand and sign a written assent form and/or give verbal assent.
6. Score on the Clinical Global Impression Scale Severity (CGI-S) ≥ 4 (moderate severity) at baseline.
7. Score of ≥18 on the Aberrant Behavior Checklist-Irritability (ABC-I) at baseline.
8. Agree not to drive or operate machinery.
Exclusion Criteria
1. Exposure to any investigational agent in the 30 days prior to randomization.
2. Prior chronic treatment with CBD or CBDV.
3. Positive testing for THC or other drugs of abuse via urine testing at the screening visit or baseline visits upon repeat confirmation testing.
4. History of Drug Abuse Disorder including Cannabis Use Disorder
5. A primary psychiatric diagnosis other than PWS, including bipolar disorder, psychosis, schizophrenia, Post-Traumatic Stress Disorder (PTSD), or Major Depressive Disorder (MDD). These patients will be excluded due to potential confounding results.
6. A medical condition that severely impacts the subject's ability to participate in the study, interferes with the conduct of the study, confounds interpretation of study results or endangers the subject's well-being (including but not limited to hepatic or renal impairment and cardiovascular disease).
7. Known or suspected allergy to CBDV or excipients used in the formulation (i.e. sesame).
8. Clinical indications of renal, pancreatic, or hematologic dysfunction as evidenced by values above upper limits of normal for Blood Urea Nitrogen (BUN)/creatinine, values twice the upper limit of normal for serum lipase and amylase, platelets \<80,000 /microliter, white blood cell (WBC)\<3.0 103 /microliter or \> 2x Upper Limit of Normal (UNL) values of aspartate aminotransferase (AST) or alanine aminotransferase (ALT).
9. ECG abnormality at baseline screening or clinically significant postural drop in systolic blood pressure at screening. If the initial screening ECG shows a Bazett's corrected QT interval (QTcB) of greater than 460 msec, then 2 additional ECGs will be conducted in the same sitting, 5 minutes apart. If not recognized at screening, then a full triplicate repeat showing an average QTcB of 460 msec or less to meet all inclusion/exclusion criteria
10. Female subjects who are pregnant will be excluded from the study. If a female subject is able to become pregnant, she will be given a pregnancy test before entry into the study. Female subjects will be informed not become pregnant while taking CBDV. Female subjects must tell the investigator and consult an obstetrician or maternal-fetal specialist if they become pregnant during the study.
