A Phase 3 Randomized, Double-blind, Placebo-controlled Study to Investigate the Efficacy and Safety of Orally Administered NNZ-2591 Compared With Placebo in Pediatric Participants With Phelan-McDermid Syndrome

Inclusion Criteria: 1. Male or female pediatric participants with Phelan-McDermid syndrome ages 3 to 12 years (inclusive) at the time of signing the informed consent. 2. Clinical diagnosis of Phelan-McDermid syndrome with a documented disease-causing genetic abnormality of SHANK3. 3. Body weight ≥ 10 kg at Screening. 4. Participants with a PMSA-S overall score ≥ 3 at the Screening and Baseline visits. 5. Not actively undergoing regression or loss of skills. Exclusion Criteria: 1. Use of exclusionary medication or unstable treatment regimens of acceptable concomitant medications as required…