NA-Selank Amidate vs NNZ-2591
Comprehensive side-by-side comparison of mechanisms, dosing, side effects, and research
Also: N-Acetyl Selank Amidate, NA-Selank
NA-Selank Amidate is a chemically stabilized version of Selank, a Russian anxiolytic peptide derived from the immune fragment tuftsin. The acetyl group on one end and the amide on the other are there to slow enzymatic breakdown, which is a real and sensible modification. What has not been established is whether that translates into a meaningfully better result than plain Selank in humans.
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.
Key Comparison Insights
- Both peptides belong to the Cognitive category, suggesting similar primary applications.
Detailed Comparison
| Attribute | NA-Selank Amidate | NNZ-2591 |
|---|---|---|
| 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 | Selank is a synthetic analog of tuftsin, a naturally occurring immunomodulatory peptide fragment. Its reported mechanism has two strands. The first is modulation of GABAergic signalling, which is the basis of its anxiolytic reputation, achieved without the sedation, tolerance or dependence associated with benzodiazepines. The second is an effect on the balance of monoamines and on BDNF expression, which is where the cognitive and mood claims come from. It also retains some of tuftsin's immunomodulatory activity, including effects on interleukin expression. The N-acetylation and C-terminal amidation in this version block the exopeptidases that would otherwise clip the peptide quickly, extending how long it survives after administration. That is a pharmacokinetic change, not a new mechanism. | 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. |
| Common Dosing | 250-500 mcg daily Once or twice daily | 12 mg/kg twice daily (phase 2 target trial dose) Twice daily |
| Administration | Intranasal is the standard route. Subcutaneous is reported but less common. | Oral liquid |
| Typical Duration | Community protocols commonly report 2-4 weeks, though Selank's clinical use does not indicate a dependence risk requiring cycling | 13 weeks in phase 2 and phase 3 trials, with 12-month open-label extensions |
| Best Time to Take | Morning or split across the day | Twice daily (trial schedule) |
Possible Side Effects May vary by individual |
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| Research Summary | Selank itself has a real research base, almost all of it Russian, including clinical work in generalised anxiety disorder where it performed comparably to benzodiazepines without the sedation and withdrawal profile, plus animal work supporting the BDNF and monoamine effects. That literature is genuine but it is largely published in Russian journals, has not been replicated in large Western trials, and has not been through FDA or EMA assessment. The amidate variant specifically has essentially no independent published pharmacology. The stability argument is chemically sound and is the same modification used across many research peptides, but nobody has published a human comparison showing it outperforms standard Selank at equivalent doses. Treat the parent compound's evidence as real but geographically narrow, and the variant's advantage as plausible rather than demonstrated. | 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. |
Frequently Asked Questions: NA-Selank Amidate vs NNZ-2591
What is the difference between NA-Selank Amidate and NNZ-2591?
NA-Selank Amidate is a cognitive peptide that na-selank amidate is a chemically stabilized version of selank, a russian anxiolytic peptide derived from the immune fragment tuftsin. the acetyl group on one end and the amide on the other are there to slow enzymatic breakdown, which is a real and sensible modification. what has not been established is whether that translates into a meaningfully better result than plain selank in humans. 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. The main differences lie in their mechanisms of action and clinical applications.
Which is better, NA-Selank Amidate or NNZ-2591?
Neither is universally "better" - the choice depends on your specific goals. NA-Selank Amidate is typically used for cognitive purposes, while NNZ-2591 is used for cognitive. Always consult with a healthcare provider to determine which may be appropriate for your situation.
Can NA-Selank Amidate and NNZ-2591 be used together?
Some peptide protocols combine multiple compounds for synergistic effects. However, using NA-Selank Amidate and NNZ-2591 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.