Key Inclusion Criteria:  Subject and their legally authorized representative must be willing to provide informed consent Confirmed genetic diagnosis of PWS  Body mass index (BMI) within the following range at Screening:  Female and male subjects 18 to 65 years of age: 27 to 60 kg/m2; or Female and male subjects 13 to 17 years of age with BMI that is at least 85th percentile for age and sex; Female subjects must be of non-child-bearing potential Documented stable body weight Moderate hyperphagia at Screening and at Baseline Participants must have a reliable and stable caregiver who should be able to spend an adequate amount of time with the participants to be able to address behaviors, activities and symptoms  Key Exclusion Criteria:  Females who are pregnant, breastfeeding, or actively intending to become pregnant during the study  Sitting BP that meets the following criteria after 5 minutes of rest at Screening:  Adult subjects with systolic BP >/=145 mmHg or <100 mmHg; or Adult subjects with diastolic BP >/=95 mmHg or <70 mmHg; or Adolescent subjects with a systolic or diastolic BP that is 95th percentile or greater for age and sex Type 1 diabetes mellitus History of dementia (eg, Alzheimer's disease, Parkinson's disease) History of bulimia or anorexia nervosa Active clinical symptoms of delusions, hallucinations, major depressive disorder, hypomania, or suicidality within 90 days prior to Screening, as defined by the Diagnostic and Statistical Manual of Mental Disorders, 5th edition (DSM-5) Uncontrolled endocrine disorders (eg, Cushing syndrome, Addison's, hypothyroidism, hyperthyroidism) Medical condition or recent systemic infection that, in the opinion of the Investigator, could impact the safety of the subject Use of prohibited medications, including current use of SSRIs/SNRIs