NA Semax Amidate Research Guide: Enhanced Nootropic Peptide

By NorthPeptide Research Team · April 4, 2026

What NA Semax Amidate Is

Semax is a synthetic heptapeptide — Met-Glu-His-Phe-Pro-Gly-Pro — developed at the Institute of Molecular Genetics of the Russian Academy of Sciences from the ACTH(4-10) fragment: it keeps the ACTH(4-7) core, Met-Glu-His-Phe, and replaces residues 8-10 (Arg-Trp-Gly) with a Pro-Gly-Pro tail.

NA Semax Amidate is that same seven-residue core capped at both ends: an acetyl group (CH₃CO-) on the N-terminal nitrogen, and an amide (-CONH₂) in place of the free carboxyl at the C-terminus. The sequence is unchanged. Only the two termini differ.

Why It Was Built That Way

The case for capping is specific rather than decorative. Exopeptidases chew inward from the ends of a peptide chain, and they need a handle to grip: aminopeptidases take the free amino group at the amino end, carboxypeptidases the free carboxyl at the other. Acetylation removes the first handle; amidation removes the second.

That those handles are the ones that matter for this peptide is measured. A tritium-labelling study of Semax degradation in rat basal forebrain cultures and plasma membranes found the dominant events to be the splitting away of the N-terminal Met-Glu and the C-terminal Gly-Pro (Zolotarev et al., 2006). Capping both ends targets exactly those two cleavages.

C-terminal amidation carries a second, independent argument. It is a genuine motif in endogenous signalling peptides — α-MSH, the closest natural relative here, is both N-acetylated and C-amidated — and amidation is a recurring feature of receptor-active endogenous peptides, adopted on the rationale that it tightens receptor binding. That rationale is design logic, not a measurement made on this molecule.

The closest neighbour anyone has actually measured is not the amidate but N-acetyl Semax, capped at the N-terminus only. Its resistance to proteolysis across several biological media was measured directly (Shevchenko et al., 2013). The same single modification also carries a documented cost: acetylation removes the free N-terminal amino group that coordinates Cu(II), and acetylated Semax — unlike Semax itself — did not protect SH-SY5Y neuroblastoma cells from copper-induced toxicity (Magrì et al., 2016). Capping is not cost-free, and neither of those studies used the double-capped molecule sold here.

What Has Been Measured On This Compound

Nothing. There is no published pharmacokinetic study of N-acetyl Semax amidate, no receptor-binding study, no behavioral study, no metabolic-stability measurement, and no head-to-head comparison against Semax. A PubMed search returns no primary research on the double-modified molecule at all.

Whether the capping delivers what the chemistry predicts — longer survival in tissue, higher brain concentrations, stronger neurotrophic induction, a lower effective dose — is untested. Each is a hypothesis, and this guide treats it as one.

What Is Known About Semax, the Parent Compound

Our Semax research guide surveys this literature, though it predates this review and repeats several of the claims disclaimed below; what follows is orientation only.

• Neurotrophins. A single 50 μg/kg intranasal dose in rats raised hippocampal BDNF protein 1.4-fold, exon III BDNF mRNA roughly 3-fold and TrkB phosphorylation 1.6-fold, alongside an increase in conditioned avoidance responses (Dolotov et al., 2006a). The response is regional and not one-directional: Ngf and Bdnf rose in hippocampus while Ngf fell in frontal cortex (Agapova et al., 2007).
• Monoamines. Striatal 5-HIAA rose after Semax, but the peptide alone did not change dopamine or its metabolites — it amplified amphetamine-evoked dopamine release rather than driving release itself (Eremin et al., 2005).
• Binding. A specific, reversible, calcium-dependent binding site was characterized in rat basal forebrain membranes, K_D ≈ 2.4 nM. It has not been identified as a melanocortin receptor (Dolotov et al., 2006b).
• Transcription. RNA-Seq of healthy rat frontal cortex found 258 differentially expressed genes, with immune-system genes predominantly decreased (Filippenkov et al., 2024).
• Ischemia. Six days of intranasal Semax after photochemically induced focal cortical ischemia decreased infarct volume and improved passive-avoidance retention (Romanova et al., 2006). A non-randomized, unblinded clinical series of 110 post-stroke patients reported a rise in plasma BDNF (Gusev et al., 2018).

Four Claims This Guide Does Not Make

• Melanocortin agonism. No published binding or functional study shows that Semax or the amidate is an agonist at MC4R or MC3R. The properties usually routed through MC4R — LTP enhancement, appetite and energy balance, anti-inflammatory signalling in microglia — are melanocortin pharmacology in general, not demonstrated mechanisms of this peptide. Note that the ACTH(4-10) residues Semax discards, Arg-Trp, are part of the melanocortin message sequence.
• GDNF upregulation. No published Semax study reports it. It appears in secondary write-ups and is not repeated here.
• The "30–50% reduction in MCAO models." This figure circulates widely and has no source behind it. No published Semax study reports a percentage reduction in infarct volume; middle cerebral artery occlusion work reports molecular and histological endpoints instead.
• Half-life and brain concentration. No published study reports a half-life or a brain-tissue concentration for NA Semax Amidate. "Most stable Semax variant" and "longer active window in neural tissue" are extrapolations from the chemistry, not findings.

References

This article is for informational and research purposes only. It does not constitute medical advice. All peptides sold by NorthPeptide are intended exclusively for laboratory and research use. Not for human consumption.