An Open-label Study of NNZ-2591 in Pediatric Participants With Phelan-McDermid Syndrome

NCT07593391 | Not Yet Recruiting Phase 3 DMC FDA Drug

• 1 other identifier: NEU-2591-PMS-302
• Study Type: interventional
• Target: 180
• Locations: 0 countries
• Sites: N/A

Brief Summary

This Phase 3, open-label extension, multicenter study will evaluate long-term safety, tolerability and efficacy of NNZ-2591 in pediatric participants with Phelan- McDermid Syndrome.

Conditions

Phelan-McDermid Syndrome

Keywords

Phelan McDermid Syndrome; NEU-2591-PMS-301; NNZ-2591; Neuren

Outcome Measures

Primary Outcomes (14)

• Long-term safety and tolerability of NNZ-2591 as assessed by the incidence of adverse events across participants

  Incidence of TEAEs, AESI and SAEs across participants

  Baseline through Safety Follow-Up (Month 12)

• Long-term safety and tolerability of NNZ-2591 as assessed by changes from Baseline assessments of ECG parameters events across participants.

  Change from Baseline in ECG Heart Rate (bpm)

  Baseline through Month 12

• Long-term safety and tolerability of NNZ-2591 as assessed by changes from Baseline assessments of ECG parameters events across participants.

  Change from Baseline PR Interval (ms QRS interval (ms)

  Baseline through Safety Follow-Up (Month 12)

• Long-term safety and tolerability of NNZ-2591 as assessed by changes from Baseline assessments of ECG parameters events across participants.

  Change from Baseline in QT interval (ms)

  Baseline through Safety Follow-Up (Month 12)

• Long-term safety and tolerability of NNZ-2591 as assessed by changes from Baseline assessments of ECG parameters events across participants.

  Change from Baseline in QTcB interval (ms)

  Baseline through Safety Follow-Up (Month 12)

• Long-term safety and tolerability of NNZ-2591 as assessed by changes from Baseline assessments of ECG parameters events across participants.

  Change from Baseline in QTcF interval (ms)

  Baseline through Safety Follow-Up (Month 12)

• Long-term safety and tolerability of NNZ-2591 as assessed by changes from Baseline assessments of ECG parameters events across participants.

  Change from Baseline in RR interval (ms)

  Baseline through Safety Follow-Up (Month 12)

• Long-term safety and tolerability of NNZ-2591 as assessed by changes from Baseline assessments of vital sign parameters events across participants.

  Change from Baseline for heart rate (bpm)

  Baseline through Month 12

• Long-term safety and tolerability of NNZ-2591 as assessed by changes from Baseline assessments of vital sign parameters events across participants.

  Change from Baseline for respiration rate (breaths per minute)

  Baseline through Month 12

• Long-term safety and tolerability of NNZ-2591 as assessed by changes from Baseline assessments of vital sign parameters events across participants.

  Change from Baseline for Temperature (Celsius)

  Baseline through Month 12

• Long-term safety and tolerability of NNZ-2591 as assessed by changes from Baseline assessments of vital sign parameters events across participants.

  Change from Baseline for Diastolic Blood Pressure (mm Hg)

  Baseline through Month 12

• Long-term safety and tolerability of NNZ-2591 as assessed by changes from Baseline assessments of vital sign parameters events across participants.

  Change from Baseline for Systolic Blood Pressure (mm Hg)

  Baseline through Month 12

• Long-term safety and tolerability of NNZ-2591 as incidence of abnormal, clinically significant clinical laboratory parameters events across participants.

  Incidence of abnormal and clinically significant laboratory parameters

  Baseline through Month 12

• Long-term safety and tolerability of NNZ-2591 as incidence of abnormal, clinically significant physical examination findings across participants.

  Incidence of abnormal, clinically significant physical examination findings

  Baseline through Month 12

Secondary Outcomes (7)

• Efficacy of NNZ-2591 as measured by the Phelan-McDermid Syndrome Assessment of Change (PMSA-C) overall score

  Months 3 and 12

• Efficacy of NNZ-2591 as measured by the change from baseline in the Vineland Adaptive Behavior Scales-3, Interview version (Vineland-3) receptive communication subdomain raw score.

  Months 3 and 12

• Efficacy of NNZ-2591 as measured by the Phelan-McDermid Syndrome Assessment of Change (PMSA-C) domain scores.

  Months 3 and 12

• Efficacy of NNZ-2591 as measured by the Caregiver Impression of Change (CIC) domain scores.

  Months 3 and 12

• Efficacy of NNZ-2591 as measured by the change from baseline in Phelan-McDermid Syndrome Assessment of Severity (PMSA-S) domain scores.

  Months 3 and 12

Study Arms (1)

NNZ-2591 Arm

EXPERIMENTAL

The total duration of this study for each participant will be up to up to 56 weeks.

Drug: NNZ-2591

Interventions

NNZ-2591 DRUG

The study drug will be administered twice daily orally.

NNZ-2591 Arm

Eligibility Criteria

• Age: 3 Years - 12 Years
• Sex: all
• Healthy Volunteers: No
• Age Groups: Child (0-17)

You may qualify if:

• Male or female pediatric participants with Phelan-McDermid syndrome ages 3 to 12 years (inclusive) at the time of signing the informed consent for the antecedent study.
• Participant must have completed all applicable study visits for the antecedent study in which they participated.
• Body weight ≥ 10 kg at Screening/Baseline.
• Participants with a PMSA-S overall score ≥ 3 at the Screening and Baseline visits.
• Not actively undergoing regression or loss of skills.

You may not qualify if:

• 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.

Sponsors & Collaborators

• Neuren Pharmaceuticals Limited: lead

MeSH Terms

Conditions

Telomeric 22q13 Monosomy Syndrome

Interventions

cyclo-L-glycyl-L-2-allylproline

Central Study Contacts

Medical Information Lead

CONTACT

231-203-8050; medicalinformation@neurenpharma.com

Study Design

• Study Type: interventional
• Phase: phase 3
• Allocation: NA
• Masking: NONE
• Purpose: TREATMENT
• Intervention Model: SINGLE GROUP
• Sponsor Type: INDUSTRY
• Responsible Party: SPONSOR

Study Record Dates

• First Submitted: March 24, 2026
• First Posted: May 18, 2026
• Study Start: May 6, 2026
• Primary Completion (Estimated): October 29, 2028
• Study Completion (Estimated): November 12, 2028
• Last Updated: May 18, 2026

Record last verified: 2026-05

Data Sharing

• IPD Sharing: Will not share