Brain & sleep IGF-1-related peptide
NNZ-2591
Regulatory status
Status at a glance
503A compounding status
Not nominated
We found no pending nomination for the 503A bulks list. Unless the substance has another legal pathway (for example, a USP monograph or use in an FDA-approved drug), 503A pharmacies generally may not compound with it.
- FDA approval
- Not FDA-approved for any use
- 503B outsourcing
- Not determined
- Anti-doping (WADA)
- Not on the WADA Prohibited List
- DEA schedule
- Not a controlled substance
About peptide status
Most peptides discussed here are not FDA-approved for any use, and products labeled “research use only” are not for human use. Removal from Category 2 does not authorize compounding. PCAC votes are non-binding recommendations; FDA and HHS make the final decisions.
This is not medical or legal advice, and we do not publish dosing, sourcing or reconstitution information. Talk with a licensed clinician before using any peptide.
If you think you are having a medical emergency, call 911.
Key takeaway
NNZ-2591 is an investigational oral peptide related to a natural fragment of IGF-1, developed by Neuren Pharmaceuticals for several rare genetic neurodevelopmental disorders including Phelan-McDermid, Rett, and Angelman syndromes. Its published human evidence is an open-label (uncontrolled) Phase 2 trial reporting broad improvement, and a placebo-controlled Phase 3 is under way. As of 2026 it is not approved.
At a glance
- FDA status
- Investigational peptide, not approved by the FDA
- What it is
- Oral analog of cyclic glycine-proline, related to the IGF-1 system
- Under study
- Several rare neurodevelopmental syndromes
- Research
- Published human data from an open-label Phase 2; a placebo-controlled Phase 3 is ongoing
- Evidence strength
- Low research
Summary
NNZ-2591 is an investigational oral peptide studied for rare neurodevelopmental disorders. Learn how it works and what its early trial data show.
What is NNZ-2591?
NNZ-2591 is an experimental drug based on cyclic glycine-proline, a naturally occurring breakdown product of insulin-like growth factor-1 (IGF-1). It is developed by Neuren Pharmaceuticals, taken by mouth, and studied across several genetic neurodevelopmental disorders, including Phelan-McDermid, Rett, Angelman, and Pitt-Hopkins syndromes. It is investigational and not approved.
How does it work?
As an analog of cyclic glycine-proline, NNZ-2591 is proposed to modulate the IGF-1 signaling system, including helping to normalize the availability of IGF-1, which supports the formation and function of connections between nerve cells. The rationale is that correcting IGF-1-related signaling could help the brain circuits affected in these developmental disorders. This describes the proposed mechanism; the human efficacy data so far are uncontrolled.
Is it FDA-approved?
Safety note
Status: Investigational peptide, not approved by the FDA
Category: In clinical trials · Primary body area: Brain & sleep
No. NNZ-2591 is investigational and not approved. Phase 2 trials have been completed in several indications, and a placebo-controlled Phase 3 trial in Phelan-McDermid syndrome is enrolling.
What does the research show?
Editor’s note
Evidence strength: Low research
The only peer-reviewed human efficacy data come from a small, open-label, uncontrolled Phase 2 with no placebo arm, so a benefit is not yet established; a controlled Phase 3 is ongoing.
The published human evidence is open-label. According to PubMed, a single-group, open-label Phase 2 trial in children and adolescents with Phelan-McDermid syndrome reported that the drug was generally well tolerated and that most efficacy measures improved from baseline over 13 weeks. Because this study had no placebo group, improvement cannot be separated from natural variation or expectation effects.
Results in Rett, Angelman, and Pitt-Hopkins syndromes have been reported mainly through company announcements. A placebo-controlled Phase 3 is intended to test efficacy properly; until then, the benefit is promising but unproven.
Sources: the open-label Phase 2 trial in Phelan-McDermid syndrome (Neumeyer et al., Neurology Genetics, 2025, DOI: 10.1212/NXG.0000000000200338; erratum DOI: 10.1212/NXG.0000000000200405), indexed on PubMed; and Neuren Pharmaceuticals development updates. This document is educational, is not medical advice or a health claim, and is not an offer to sell any product.
Registered human trials
0 registered human trials on ClinicalTrials.gov that we reviewed
Sources
- [1]
- [2]
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