Phelan-McDermid SyndromePhase 3NCT07593391
An Open-label Study of NNZ-2591 in Pediatric Participants With Phelan-McDermid Syndrome
A Phase 3 study testing NNZ-2591 in people with Phelan-McDermid Syndrome, run by Neuren Pharmaceuticals Limited at 11 sites in United States.
Trial 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. Read more about this study
- Who is it for?
- Ages 3 to 12 years
- Conditions the study is for
- Phelan-McDermid Syndrome
- What is being tested?
- NNZ-2591
- Type of treatment
- Pill or oral medicine
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 180 participants
- Where
- 11 sitesUnited States
- Study dates
- 8 Jun 2026to 12 Nov 2028
- Phase
- Phase 3
- Are there results?
- Not yet: the study is under way
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 3 to 12 years
- All sexes
- No healthy volunteers
- Child
Who may be able to join
- 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.
Who cannot join
- Use of exclusionary medication or unstable treatment regimens of acceptable concomitant medications as required by the protocol.
- 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.
Trial locations and contacts
11 sites in 1 country. Contact the study team or a site near you to ask about taking part.
11 sites in 1 country
United States11 sites, 11 recruiting
- Recruiting
Neuren PMS-302 Site #116
Birmingham, Alabama, 35233
medicalinformation@neurenpharma.com, 231-203-8050, medicalinformation@neurenpharma.com
- Recruiting
Neuren PMS-302 Site#106
Brookline, Massachusetts, 02445
medicalinformation@neurenpharma.com, 231-203-8050, medicalinformation@neurenpharma.com
- Recruiting
Neuren PMS-302 Site#113
Charlottesville, Virginia, 22903
medicalinformation@neurenpharma.com, 231-203-8050, medicalinformation@neurenpharma.com
- Recruiting
Neuren PMS-302 Site#109
Chevy Chase, Maryland, 20815
medicalinformation@neurenpharma.com, 231-203-8050, medicalinformation@neurenpharma.com
- Recruiting
Neuren PMS-302 Site#102
Chicago, Illinois, 60612
medicalinformation@neurenpharma.com, 231-203-8050, medicalinformation@neurenpharma.com
- Recruiting
Neuren PMS-302 Site#108
Cincinnati, Ohio, 02421
medicalinformation@neurenpharma.com, 231-203-8050, medicalinformation@neurenpharma.com
- Recruiting
Neuren PMS-302 Site#122
Glendale, California, 91203
medicalinformation@neurenpharma.com, 231-203-8050, medicalinformation@neurenpharma.com
- Recruiting
Neuren PMS-302 Site#115
Houston, Texas, 77030
medicalinformation@neurenpharma.com, 231-203-8050, medicalinformation@neurenpharma.com
- Recruiting
Neuren PMS-302 Site#104
Lexington, Massachusetts, 02421
medicalinformation@neurenpharma.com, 231-203-8050, medicalinformation@neurenpharma.com
- Recruiting
Neuren PMS-302 Site#101
New York, New York, 10029
medicalinformation@neurenpharma.com, 231-203-8050, medicalinformation@neurenpharma.com
- Recruiting
Neuren PMS-302 Site#111
San Rafael, California, 94903
medicalinformation@neurenpharma.com, 2312038050, medicalinformation@neurenpharma.com
About this study
Official title: A Phase 3 Open-label Extension Study to Investigate the Long-term Safety and Efficacy of Orally Administered NNZ-2591 in Pediatric Participants With Phelan-McDermid Syndrome
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.
Read the detailed description
After providing informed consent/assent, pediatric participants with Phelan-McDermid syndrome who participated in previous studies (NEU-2591-PMS-301 and NEU-2591-PMS-001) will undergo assessments for eligibility, baseline characteristics and symptom severity. Once eligibility is confirmed, participants will receive orally administered NNZ-2591 during the 52-week Treatment Period. A 2-week safety follow-up period will occur immediately after the completion of the Treatment Period.
- Conditions
- Phelan-McDermid Syndrome
- Being tested
- NNZ-2591
- Keywords
- Phelan McDermid Syndrome, NEU-2591-PMS-301, NNZ-2591, Neuren
- Medical subject headings
- Telomeric 22q13 Monosomy Syndrome
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
NNZ-2591Drug
The study drug will be administered twice daily orally.
| Study group | Role | What they receive |
|---|---|---|
| NNZ-2591 Arm | Experimental | The total duration of this study for each participant will be up to up to 56 weeks. Receives: Drug: NNZ-2591 |
What is being measured
The primary outcome is the main question the study is designed to answer.
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
Measured: 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)
Measured: 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)
Measured: 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)
Measured: 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)
Measured: 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)
Measured: 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)
Measured: 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)
Measured: 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)
Measured: 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)
Measured: 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)
Measured: 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)
Measured: 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
Measured: 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
Measured: 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
Efficacy of NNZ-2591 as measured by the Phelan-McDermid Syndrome Assessment of Change (PMSA-C) overall score. The PMSA-C scores range from 1 to 7 with 1 indicating very much improved and 7 indicating very much worse.
Measured: 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.
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. A higher raw score for the receptive communication subdomain indicates better adaptive behavior.
Measured: Months 3 and 12
Efficacy of NNZ-2591 as measured by the Phelan-McDermid Syndrome Assessment of Change (PMSA-C) domain scores.
Efficacy of NNZ-2591 as measured by the Phelan-McDermid Syndrome Assessment of Change (PMSA-C) domain scores. The PMSA-C domain scores range from 1 to 7 with 1 indicating very much improved and 7 indicating very much worse.
Measured: Months 3 and 12
Efficacy of NNZ-2591 as measured by the Caregiver Impression of Change (CIC) domain scores.
Efficacy of NNZ-2591 as measured by the Caregiver Impression of Change (CIC) domain scores. The CIC scores range from 1 to 7 with 1 indicating very much improved and 7 indicating very much worse.
Measured: 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.
Efficacy of NNZ-2591 as measured by the change from baseline in Phelan-McDermid Syndrome Assessment of Severity (PMSA-S) domain scores. The PMSA-S scores range from 1 to 7 with 1 indicating typical for age, not at all impaired and 7 among the most severely impaired.
Measured: Months 3 and 12
Efficacy of NNZ-2591 as measured by the change from baseline in Phelan-McDermid Syndrome Assessment of Severity (PMSA-S) overall score.
Efficacy of NNZ-2591 as measured by the change from baseline in Phelan-McDermid Syndrome Assessment of Severity (PMSA-S) overall score. The PMSA-S scores range from 1 to 7 with 1 indicating typical for age, not at all impaired and 7 among the most severely impaired.
Measured: Months 3 and 12
Efficacy of NNZ-2591 as measured by the change from baseline in PMS Clinician Domain Specific Rating Scale (PMS-DSRS) scores.
Efficacy of NNZ-2591 as measured by the change from baseline in PMS Clinician Domain Specific Rating Scale (PMS-DSRS) scores. The PMS-DSRS scores range from 0 to 4 with 0 indicating Symptom Not Present and 4 indicating Very Severe.
Measured: Months 3 and 12
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted18 May 2026
- Study start8 Jun 2026
- Primary completion29 Oct 2028 (estimated)
- Study completion12 Nov 2028 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Phelan-McDermid SyndromeStudies of the same condition, open and under way.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase 3
- Primary purpose
- Treatment
- Allocation
- Not applicable
- Intervention model
- Single group
- Masking
- None (open label)
- Enrolment
- 180 participants (estimated)
Sponsor and investigators
- Lead sponsor
- Neuren Pharmaceuticals Limited
- Sponsor type
- Industry (pharma, biotech, devices)
- Responsible party
- Sponsor
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT07593391
- Sponsor's protocol ID
- NEU-2591-PMS-302
- Status last verified
- Sep 2026
- First submitted
- 24 Mar 2026
- Last updated
- 19 Oct 2026
- Results posted
- No
- Data monitoring committee
- Yes
- FDA-regulated drug
- Yes
- FDA-regulated device
- No
- Individual data sharing
- No
Study at a glance
From the registry record, last updated by the sponsor on 19 Oct 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- A Phase 3 Open-label Extension Study to Investigate the Long-term Safety and Efficacy of Orally Administered NNZ-2591 in Pediatric Participants With Phelan-McDermid Syndrome
- ClinicalTrials.gov ID
- NCT07593391
- Acronym / sponsor ID
- NEU-2591-PMS-302
- Conditions
- Phelan-McDermid Syndrome
- Keywords
- Phelan McDermid Syndrome, NEU-2591-PMS-301, NNZ-2591, Neuren
- Phase
- Phase 3
- Study type
- Interventional
- Recruitment status
- Recruiting
- Enrolment
- 180 participants (estimated)
- Lead sponsor
- Neuren Pharmaceuticals LimitedIndustry (pharma, biotech, devices)
- Study start
- 8 Jun 2026 (actual)
- Primary completion
- 29 Oct 2028 (estimated)
- Study completion
- 12 Nov 2028 (estimated)
- First posted
- 18 May 2026 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
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.
Detailed description
After providing informed consent/assent, pediatric participants with Phelan-McDermid syndrome who participated in previous studies (NEU-2591-PMS-301 and NEU-2591-PMS-001) will undergo assessments for eligibility, baseline characteristics and symptom severity. Once eligibility is confirmed, participants will receive orally administered NNZ-2591 during the 52-week Treatment Period. A 2-week safety follow-up period will occur immediately after the completion of the Treatment Period.
Study design
- Primary purpose
- Treatment
- Allocation
- Not applicable
- Intervention model
- Single group
- Masking
- None (open label)
- Number of arms
- 1
| Arm | Type | Receives |
|---|---|---|
| NNZ-2591 Arm | Experimental | Drug: NNZ-2591The total duration of this study for each participant will be up to up to 56 weeks. |
Who may qualify
- Ages
- 3 to 12 years
- Sex
- All
- Healthy volunteers
- Not accepted
- Age groups
- Child
Key inclusion criteria (5 listed)
- 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.
Key exclusion criteria (6 listed)
- Use of exclusionary medication or unstable treatment regimens of acceptable concomitant medications as required by the protocol.
- 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
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| NNZ-2591The study drug will be administered twice daily orally. | Drug | NNZ-2591 Arm |
Primary outcome
Long-term safety and tolerability of NNZ-2591 as assessed by the incidence of adverse events across participants
Time frame: Baseline through Safety Follow-Up (Month 12)
Incidence of TEAEs, AESI and SAEs across participants
Long-term safety and tolerability of NNZ-2591 as assessed by changes from Baseline assessments of ECG parameters events across participants.
Time frame: Baseline through Month 12
Change from Baseline in ECG Heart Rate (bpm)
Long-term safety and tolerability of NNZ-2591 as assessed by changes from Baseline assessments of ECG parameters events across participants.
Time frame: Baseline through Safety Follow-Up (Month 12)
Change from Baseline PR Interval (ms QRS interval (ms)
Long-term safety and tolerability of NNZ-2591 as assessed by changes from Baseline assessments of ECG parameters events across participants.
Time frame: Baseline through Safety Follow-Up (Month 12)
Change from Baseline in QT interval (ms)
Long-term safety and tolerability of NNZ-2591 as assessed by changes from Baseline assessments of ECG parameters events across participants.
Time frame: Baseline through Safety Follow-Up (Month 12)
Change from Baseline in QTcB interval (ms)
Long-term safety and tolerability of NNZ-2591 as assessed by changes from Baseline assessments of ECG parameters events across participants.
Time frame: Baseline through Safety Follow-Up (Month 12)
Change from Baseline in QTcF interval (ms)
Long-term safety and tolerability of NNZ-2591 as assessed by changes from Baseline assessments of ECG parameters events across participants.
Time frame: Baseline through Safety Follow-Up (Month 12)
Change from Baseline in RR interval (ms)
Long-term safety and tolerability of NNZ-2591 as assessed by changes from Baseline assessments of vital sign parameters events across participants.
Time frame: Baseline through Month 12
Change from Baseline for heart rate (bpm)
Long-term safety and tolerability of NNZ-2591 as assessed by changes from Baseline assessments of vital sign parameters events across participants.
Time frame: Baseline through Month 12
Change from Baseline for respiration rate (breaths per minute)
Long-term safety and tolerability of NNZ-2591 as assessed by changes from Baseline assessments of vital sign parameters events across participants.
Time frame: Baseline through Month 12
Change from Baseline for Temperature (Celsius)
Long-term safety and tolerability of NNZ-2591 as assessed by changes from Baseline assessments of vital sign parameters events across participants.
Time frame: Baseline through Month 12
Change from Baseline for Diastolic Blood Pressure (mm Hg)
Long-term safety and tolerability of NNZ-2591 as assessed by changes from Baseline assessments of vital sign parameters events across participants.
Time frame: Baseline through Month 12
Change from Baseline for Systolic Blood Pressure (mm Hg)
Long-term safety and tolerability of NNZ-2591 as incidence of abnormal, clinically significant clinical laboratory parameters events across participants.
Time frame: Baseline through Month 12
Incidence of abnormal and clinically significant laboratory parameters
Long-term safety and tolerability of NNZ-2591 as incidence of abnormal, clinically significant physical examination findings across participants.
Time frame: Baseline through Month 12
Incidence of abnormal, clinically significant physical examination findings
7 secondary outcomes
Efficacy of NNZ-2591 as measured by the Phelan-McDermid Syndrome Assessment of Change (PMSA-C) overall score
Time frame: 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.
Time frame: Months 3 and 12
Efficacy of NNZ-2591 as measured by the Phelan-McDermid Syndrome Assessment of Change (PMSA-C) domain scores.
Time frame: Months 3 and 12
Efficacy of NNZ-2591 as measured by the Caregiver Impression of Change (CIC) domain scores.
Time frame: 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.
Time frame: Months 3 and 12
Efficacy of NNZ-2591 as measured by the change from baseline in Phelan-McDermid Syndrome Assessment of Severity (PMSA-S) overall score.
Time frame: Months 3 and 12
Efficacy of NNZ-2591 as measured by the change from baseline in PMS Clinician Domain Specific Rating Scale (PMS-DSRS) scores.
Time frame: Months 3 and 12
Results and safety
This study is still under way. Results are not available in the source record yet.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 19 Oct 2026.
- Individual participant dataSharing planned: No
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part.
11 sites in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A Phase 3 study testing NNZ-2591 in people with Phelan-McDermid Syndrome, run by Neuren Pharmaceuticals Limited at 11 sites in United States.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 5 inclusion and 6 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: looking for participants now, as of the sponsor's last update on 19 Oct 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 11 sites in United States. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
What does this phase mean?
Phase 3 studies compare the treatment with the current standard treatment or a placebo in a large group, to confirm how well it works and watch for side effects.
Not every study follows the same path, and some studies (observational studies, device studies) have no phase.
Are results available for this study?
This study is still under way. Results are not available in the source record yet.
How can a doctor refer a patient or contact the research team?
Contact Medical Information Lead (231-203-8050, medicalinformation@neurenpharma.com), or a site near the patient. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Long-term safety and tolerability of NNZ-2591 as assessed by the incidence of adverse events across participants (time frame: Baseline through Safety Follow-Up (Month 12)). The study lists 14 primary outcomes in all. It is what the study was designed to measure, not a finding.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 19 Oct 2026.