JAG201 Gene Therapy Study in Children & Adults With SHANK3 Haploinsufficiency

A target of 6 pediatric participants aged 2 to 9 years will be treated in Cohorts 1 and 2. In total, all participants will be followed for safety and tolerability for at least 5 years after the date of treatment with JAG201. The study will include 5 periods: Pre-Screening, Screening, Gene Therapy Administration and Perioperative Management, Initial Follow-Up, and Long-Term Follow-Up. Study participants will be evaluated for treatment eligibility during the Pre-Screening and Screening Periods. The Pre-Screening/Screening Period may be up to 90 days before treatment with JAG201 (Day 1). On Day 1, treatment-eligible participants will receive a one-time ICV injection of JAG201. Participant safety will be monitored closely after JAG201 administration in a hospital setting. During the Initial Follow-Up Period, up to Year 2, participants will return at regularly scheduled intervals for safety and clinical activity assessments. Participants will continue the study in the Long-Term Follow-Up Period through Year 5.