NNZ-2591 vs Davunetide
Comprehensive side-by-side comparison of mechanisms, dosing, side effects, and research
Also: Cyclo-L-glycyl-L-2-allylproline, Cyclic glycine-proline analog
NNZ-2591 is Neuren Pharmaceuticals' second drug, a synthetic analog of cyclic glycine-proline (cGP), a small ring-shaped molecule the body makes when it breaks down IGF-1. It is taken by mouth and is being developed for rare childhood neurodevelopmental disorders: Phelan-McDermid syndrome is furthest along, with the first-ever phase 3 trial in that disease started in late 2025, and Angelman and Pitt Hopkins syndromes behind it. Phase 2 results looked encouraging, but they were small open-label studies, so nobody knows yet whether it truly works.
Also: NAP, AL-108
Davunetide (NAP) is an eight-amino-acid fragment (NAPVSIPQ) of activity-dependent neuroprotective protein (ADNP), discovered at Tel Aviv University and given as a nasal spray. It was meant to protect brain cells by stabilizing microtubules, the scaffolding that tau normally supports. Its big test, a phase 2/3 trial in progressive supranuclear palsy (PSP), failed cleanly in 2012, and development stalled. It has since been revived by its inventors, who argue it works in women and are pursuing ADNP syndrome, but those claims rest on reanalyses of old data, not a new successful trial.
Key Comparison Insights
- Both peptides belong to the Cognitive category, suggesting similar primary applications.
Detailed Comparison
| Attribute | NNZ-2591 | Davunetide |
|---|---|---|
| Category | Cognitive | Cognitive |
| FDA Status | Not FDA Approved | Not FDA Approved |
| Clinical Status | Pre I II III IV FDA | Pre I II III IV FDA |
| Mechanism of Action | Cyclic glycine-proline is thought to fine-tune IGF-1 activity in the brain by changing how IGF-1 binds to its carrier protein IGFBP-3. A 2014 Scientific Reports study proposed that cGP nudges IGF-1 activity up when it is low and down when it is high, a normalizing effect rather than a simple boost. NNZ-2591 adds an allyl group to the proline ring, making it resistant to enzymes and able to reach the brain after oral dosing. Trial protocols also describe reduced neuroinflammation and support for synapse function in animal models. It is a close cousin of trofinetide in spirit (both are small IGF-1-derived molecules from the same company), but the exact way it helps in these genetic syndromes has not been pinned down in humans. | NAP comes from ADNP, a protein essential for brain development. In cell and animal studies it interacts with microtubule end-binding proteins (EB1 and EB3), promoting microtubule stability and reducing tau phosphorylation, which is why it was aimed at tauopathies like PSP and Alzheimer's disease. Mutations in the ADNP gene itself cause ADNP syndrome (Helsmoortel-Van der Aa syndrome), and in ADNP-deficient mice NAP improved some behavioral and neural measures, the rationale for that newer program. The PSP trial did not include target-engagement measures, so it never showed the drug was actually doing this in human brains. |
| Common Dosing | 12 mg/kg twice daily (phase 2 target trial dose) Twice daily | 30 mg intranasal twice daily (PSP trial dose) Once or twice daily |
| Administration | Oral liquid | Intranasal spray (an IV form, AL-208, was tested in cardiac surgery) |
| Typical Duration | 13 weeks in phase 2 and phase 3 trials, with 12-month open-label extensions | 12 weeks to 52 weeks in trials |
| Best Time to Take | Twice daily (trial schedule) | Twice daily (trial schedule) |
Possible Side Effects May vary by individual |
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| Research Summary | The human data so far come from three small, open-label phase 2 trials of 13 weeks each, all with twice-daily oral dosing titrated up to a target of 12 mg/kg. In Phelan-McDermid syndrome (18 children, published in Neurology Genetics in 2026), 10 of 14 efficacy measures improved significantly from baseline, including clinician and caregiver global ratings, behavior, sleep and communication, and the drug was well tolerated with mostly mild to moderate side effects. Angelman syndrome (reported August 2024) showed a mean CGI-I of 3.0, with 11 of 13 children rated improved by clinicians. Pitt Hopkins syndrome (reported May 2024) showed improvement in 6 of 11 children on clinician-rated severity. The big caveat: none of these had a placebo group, and rare-disease trials with caregiver-rated outcomes are especially prone to placebo effects. A planned Prader-Willi trial was withdrawn before enrolling anyone. The real test is Koala, a randomized, double-blind, placebo-controlled phase 3 trial in about 160 children aged 3 to 12 with Phelan-McDermid syndrome (first patient dosed February 2026; estimated primary completion late 2027), with an open-label extension started in 2026. The FDA has given the program Fast Track, Rare Pediatric Disease and Orphan Drug designations. Neuren has also started work in neonatal hypoxic-ischemic encephalopathy, which is still preclinical. | The headline result is negative. In the phase 2/3 PSP trial (Boxer and colleagues, Lancet Neurology 2014), 313 patients got 30 mg intranasal davunetide twice daily or placebo for 52 weeks. Disease progression was identical in both groups on both primary measures (PSP Rating Scale and Schwab and England daily living scale), and the authors concluded davunetide is not an effective treatment for PSP. Earlier phase 2 work was mixed: a 12-week trial in 144 people with amnestic mild cognitive impairment hinted at working-memory benefits, and a schizophrenia trial missed one co-primary endpoint while hitting another. The original developer, Allon Therapeutics, stopped investing and was later absorbed by Paladin Labs. The revival comes from the inventor's group: post hoc reanalyses of the PSP data (Translational Psychiatry 2023, Molecular Psychiatry 2026) report that women declined faster than men and that davunetide slowed decline in women only. A similar sex-split reanalysis of the MCI trial was published in 2024. These findings are interesting but are subgroup analyses of trials that failed overall, done by researchers tied to the company now developing the drug (ExoNavis Therapeutics), so they need a new prospective trial to mean much. ExoNavis has said a phase 3 in children with ADNP syndrome began in 2024, but Alzforum could not find it in trial registries. Davunetide holds FDA orphan and rare pediatric disease designations and EMA orphan status for ADNP syndrome. |
Frequently Asked Questions: NNZ-2591 vs Davunetide
What is the difference between NNZ-2591 and Davunetide?
NNZ-2591 is a cognitive peptide that nnz-2591 is neuren pharmaceuticals' second drug, a synthetic analog of cyclic glycine-proline (cgp), a small ring-shaped molecule the body makes when it breaks down igf-1. it is taken by mouth and is being developed for rare childhood neurodevelopmental disorders: phelan-mcdermid syndrome is furthest along, with the first-ever phase 3 trial in that disease started in late 2025, and angelman and pitt hopkins syndromes behind it. phase 2 results looked encouraging, but they were small open-label studies, so nobody knows yet whether it truly works. Davunetide is a cognitive peptide that davunetide (nap) is an eight-amino-acid fragment (napvsipq) of activity-dependent neuroprotective protein (adnp), discovered at tel aviv university and given as a nasal spray. it was meant to protect brain cells by stabilizing microtubules, the scaffolding that tau normally supports. its big test, a phase 2/3 trial in progressive supranuclear palsy (psp), failed cleanly in 2012, and development stalled. it has since been revived by its inventors, who argue it works in women and are pursuing adnp syndrome, but those claims rest on reanalyses of old data, not a new successful trial. The main differences lie in their mechanisms of action and clinical applications.
Which is better, NNZ-2591 or Davunetide?
Neither is universally "better" - the choice depends on your specific goals. NNZ-2591 is typically used for cognitive purposes, while Davunetide is used for cognitive. Always consult with a healthcare provider to determine which may be appropriate for your situation.
Can NNZ-2591 and Davunetide be used together?
Some peptide protocols combine multiple compounds for synergistic effects. However, using NNZ-2591 and Davunetide together should only be considered under medical supervision, as both compounds have their own side effect profiles and potential interactions. Research on their combined use may be limited.