1. Male or female and 5 through 30 years of age
2. Prader-Willi syndrome with a documented disease-causing mutation
3. Increased appetite with decreased satiety accompanied by food seeking (consistent with PWS Nutritional Phase 3)
4. HQ-CT total score of ≥13 at Screening and Baseline
5. CGI-S score for hyperphagia in PWS of ≥4 at Screening and Baseline
6. Lives with a caregiver who understands and is willing and able to adhere to study-related procedures and is willing to participate in all study visits

1. Genetically diagnosed with Schaaf-Yang syndrome or another genetic, hormonal, or chromosomal cognitive impairment besides PWS
2. An active upper respiratory infection at the Screening visit or the Baseline visit
3. Any clinically significant cardiovascular disorder, renal, hepatic, gastrointestinal, or respiratory disease, including severe asthma
4. History of, or current, cerebrovascular disease, brain trauma, epilepsy, or frequent migraines. A history of febrile seizures is not exclusionary
5. Nasal surgery within 1 month of Screening visit or planning to have nasal surgery during the study.
6. Unwilling to abstain from nasal saline, other nasal irrigation, and other intranasal medications during the Screening period and through the treatment period of the study
7. Clinically significant irritability or agitation, requiring initiation of or increase in the dose of antipsychotic medication, within the 6 months prior to the Screening visit
8. Used prostaglandins, prostaglandin analogues, or prostaglandin agonists in the 3 months prior to the 9. Baseline visit. Inhibitors of prostaglandin synthesis, such as nonsteroidal anti-inflammatory drugs, are not exclusionary.
9. Started a glucagon-like peptide 1 (GLP-1) agonist within the 6 months prior to the Screening visit. 11. Treatment with GLP-1 agonist is allowed if the subject has been taking it for more than 6 months prior to Screening.
10. Used oxytocin, desmopressin (DDAVP), or tesofensine within 6 months prior to the Baseline visit
11. Active psychotic symptoms, a history of psychotic symptoms, or a psychotic disorder
12. History of suicide attempt or inpatient psychiatric hospitalization
13. New food-related interventions, including environment or dietary restrictions, within 1 month of the Screening visit

Additional inclusion/exclusion criteria apply. Subjects will be evaluated at screening to ensure that all criteria for study participation are met.