Neuren’s Phase 3 NNZ-2591 Trial for Phelan-McDermid Syndrome is Now Active!

by: Lauren Schmitt, PhD

Date: December 15, 2025

The Phelan-McDermid Syndrome Foundation is sharing an important update with our community: Neuren’s Phase 3 clinical trial of NNZ-2951, known as the “Koala” study, is now active and listed on clinicaltrials.gov.  

This study is a Phase 3 randomized, double-blind, placebo-controlled clinical trial evaluating NNZ-2591 in children aged 3 to 12 years with Phelan-McDermid syndrome. This marks the first Phase 3 clinical trial conducted specifically in Phelan-McDermid syndrome, representing a significant milestone in the clinical trial pipeline for the community. 

What is a Phase 3 clinical trial?

Phase 3 clinical trials are conducted across multiple study sites and include a large number of participants.These trials take place after earlier-phase studies have shown promising findings related to safety and potential benefit. 

The Koala study follows Neuren’s Phase 2 clinical trial of NNZ-2591, which informed the design of this Phase 3 study.

Phase 3 clinical trials are designed to be rigorous and objective and typically include: 

  • Randomized – Participants are randomly assigned  (like flipping a coin) to receive either the study drug OR a placebo (pill that looks real with no active medical effect). 
  • Double-blinded – Neither participants nor the study clinicians know who is receiving the study drug or placebo during the trial.
  • Placebo-controlled – Outcomes from participants receiving the study drug are compared to those receiving the placebo to determine whether the treatment has a measurable effect.

Interested in participating in the Phase 3 NNZ-2591 trial?

Families who would like to learn more about recruitment or enrollment may contact Neuren’s medical team directly at: medicalinformation@neurenpharma.com. 

The study drug, study-related procedures, and travel associated with clinic visits will be provided at no cost.

Additional resources

 

At PMSF, our mission is to remain objective in providing information to the Phelan-McDermid syndrome community; we do not endorse any particular treatment, therapy, clinical trial, or product.

Participation in a clinical trial is a personal decision, and families are encouraged to discuss potential participation with their loved one’s healthcare team.