Open Label Extension to Assess the Long-Term Safety and Tolerability of ZYN002 in Children and Adolescents With FXS

Inclusion Criteria: * Participated in study ZYN2-CL-016 or Study ZYN2-CL-033. * Patients and parents/caregivers agree to abide by all study restrictions and comply with all study procedures. * Patients and parents/caregivers must be adequately informed of the nature, risks of the study, and give written informed consent prior to enrollment in ZYN2-CL-017. * In the Investigator's opinion, the patients and parents/caregivers are reliable and are willing and able to comply with all protocol requirements and procedures. * Females of childbearing potential must have a negative pregnancy test at all designated visits Exclusion Criteria: * Patient is receiving any investigational drugs (not ZYN002) or using any experimental devices. * Patient has an ongoing serious adverse event (SAE) or has experienced a SAE in ZYN2-CL-016 or ZYN2-CL-033, which in the opinion of the Investigator, should exclude them from participation. * Females who are pregnant, nursing, or planning a pregnancy; females of childbearing potential and male patients with a partner of childbearing potential who are unwilling or unable to use an acceptable method of contraception for the duration of therapy and for three months after the last dose of trial drug. * Patients who have alanine aminotransferase (ALT), aspartate aminotransferase (AST), or total bilirubin levels ≥ 2 times the upper limit of normal (ULN) or has alkaline phosphatase levels ≥ 3 times the ULN as determined from patient safety laboratories.