A Study of NNZ-2591 in Pediatric Participants With Phelan-McDermid Syndrome

After providing informed consent/assent, pediatric participants with Phelan-McDermid syndrome ages 3-12 years of age will enter the 4-week Screening Period and undergo assessments for eligibility, baseline characteristics and symptom severity.

Once eligibility is confirmed, participants will be randomized in a 1:1 ratio to receive either orally administered NNZ-2591 or matching placebo during the 13-week Treatment Period. Subsequently, a 2-week safety follow-up period will occur immediately after the completion of the Treatment Period.

Inclusion criteria

• Male or female pediatric participants with Phelan-McDermid syndrome ages 3 to 12 years (inclusive) at the time of signing the informed consent.
• Clinical diagnosis of Phelan-McDermid syndrome with a documented disease-causing genetic abnormality of SHANK3.
• Body weight ≥ 10 kg at Screening.
• Participants with a PMSA-S overall score ≥ 3 at the Screening and Baseline visits.
• Not actively undergoing regression or loss of skills.

Exclusion criteria

• Use of exclusionary medication or unstable treatment regimens of acceptable concomitant medications as required by the protocol.
• Current treatment with more than 3 allowable psychotropic medications.
• Participants with seizures must be controlled on no more than 2 anticonvulsant medications (not counting rescue medications).
• Psychotropic medications or any other medication used for a chronic illness (not including antibiotics, pain relievers, anti-diarrheals, and laxatives) with doses and dosing regimen that have not been stable for at least 4 weeks before Screening. If the treatment was discontinued, the discontinuation must have occurred no fewer than 2 weeks before the start of Screening.
• Any intercurrent seizures in the past 6 months and /or more than 1 seizure in the past 12 months. •A single febrile seizure in the 6 months prior to screening is allowable if no rescue medication was required.
• Abnormal liver function laboratory results during the Screening period, as defined by the protocol
• Abnormal QT interval on Screening ECG as defined by the protocol.