This is a multi-center, multi-period study with an open-label period followed by a double-blind, placebo-controlled, randomized withdrawal period evaluating the safety and efficacy of DCCR treatment.

115 PWS participants who completed clinical study C601 will be enrolled into the OLE Period. All participants in the Open Label Extension (OLE) Period will receive open-label DCCR. The actual number of participants eligible to enroll in the double-blind, placebo-controlled, randomized withdrawal (RW) period will be limited to those participants taking DCCR in the OLE Period at the time of the RW Period Visit 1 (Baseline/Randomization Visit).The treatment groups in the C602 RW Period are those participants randomized to receive DCCR and those participants randomized to receive Placebo. Participants will be randomized in a 1:1 ratio (DCCR:Placebo).

OLE Period Key Inclusion Criteria:

• Successful completion of clinical study C601
• Provide voluntary, written informed consent (parent(s) / legal guardian(s) of patient); provide voluntary, written assent (subjects, as appropriate)

OLE Period Key Exclusion Criteria:

• Positive urine pregnancy test (in females of child-bearing potential) or females who are pregnant or breastfeeding, and/or plan to become pregnant or to breast-feed during or within 90 days after study participation
• Any new disease, condition, or circumstance which would prevent, in the opinion of the Investigator, the patient from completing all study visits and assessments required by the protocol (e.g., an anticipated change of care setting)

RW Period Key Inclusion Criteria:

• Provide voluntary, written informed consent (parent[s] / legal guardian[s] of participant); provide voluntary, written assent (participants, as appropriate); this includes consent for randomization and potential treatment with placebo for up to 16 weeks
• Currently participating in clinical study C602 and complete the OLE End of Treatment Visit procedures

RW Period Key Exclusion Criteria:

• Positive urine pregnancy test (in females of child-bearing potential)
• Females who are pregnant or breastfeeding, and/or plan to become pregnant or to breast-feed during or within 30 days after study participation