Study
What is the purpose of the Phelan-McDermid syndrome study?
The purpose of the study is to look at the safety, tolerability, and efficacy of NNZ-2591 in the treatment of children with Phelan-McDermid syndrome.
This study investigates an oral medication called “NNZ-2591”, which aims to improve the impaired connections and signalling between brain cells that are involved in Phelan-McDermid syndrome. The study medication is experimental.

What does the study involve?
Participation in the study will be required for approximately 19 weeks, with a combination of in-clinic, remote, and telehealth consultations. An in-home nurse will also visit your house to check on the participant and administer a number of assessments.
Participants in the Phelan-McDermid study will need to:
- Attend clinic appointments
- Take study medication
- Have blood, urine, and stool samples collected for laboratory testing
- Have Phelan-McDermid syndrome symptoms monitored
- Have heart activity monitored
- Caregivers will also need to complete a number of assessments capturing their view of the participant’s progress.
To ease the burden of travel on families, an in-home nurse will be available to assist with telehealth/remote visits. At a time convenient to yourselves, the in-home nurse will visit your home and conduct a number of the required study assessments. This has been included in the study design to make it easier for your family to participate in the study and promote inclusion, without compromising on the data that needs to be collected at each visit.
Is there a cost?
There is no cost to participate in this clinical trial.
Reimbursement is available for reasonable travel and incidental costs incurred attending your clinic visits. More details can be found here.
Who is eligible for this study?
Potential participants must:
- Have a diagnosis of Phelan-McDermid syndrome.
- Be aged between 3-12 years old.
- Be able to swallow a liquid medication.
Specific details on the eligibility criteria can be found at ClinicalTrials.gov.
Recruitment for the PMS Study closed in June 2023.
Topline results from the trial are expected to be available in December 2023.