Neuro & cognitive

N-Acetyl Semax Amidate

Also called NA-Semax-Amidate, N-acetyl Semax, Ac-Semax-NH2, Ac-MEHFPGP-NH2

N-Acetyl Semax Amidate is a chemically capped version of Semax, a short peptide registered as a nasal drug in Russia. It is sold online as a 'stronger' or 'longer-lasting' Semax, but we found no published study that tested this exact form in animals or people. Almost everything said about it is borrowed from research on plain Semax.

Preclinical onlyStudied in cells or animals only. Effects in people are unknown.

New · under editorial review. Added October 30, 2026 by our automated research, with every claim sourced. A person has not checked this page yet; treat it with extra care. How we research

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Drawn from its published sequence: 7 residues, one bead each.

Overview

How it works

Unknown for this form. Semax itself is thought, from mostly animal and cell work, to have several brain effects ². FDA's review notes that Semax is broken down quickly in rat blood and brain tissue, with breakdown products formed by removing amino acids one by one from the N-terminal end; in rat serum the main enzymes are aminopeptidases and angiotensin-converting enzyme ². Capping that end is the apparent reason for the modified version, but we found no published data showing it actually lasts longer or works better in a living animal. One cell study found that acetylating Semax's N-terminus changed how it binds copper and removed its ability to protect neuroblastoma (nerve-like) cells from copper toxicity, showing that the change can alter biology, not just stability ³. A 2005 rat study published in Russian found that changing or replacing the first amino acid of Semax could keep, weaken or abolish its effect on learning, depending on the change; acetylation and amidation were not among the changes tested ⁵.

What research shows

No peer-reviewed study of the N-acetyl + amidated form was found in PubMed or Europe PMC (searched 2026-10-30). No registered human trials ⁹.
Cell and chemistry study of N-acetyl Semax (not amidated), 2016: acetylation changed copper(II) binding; unlike Semax, acetylated Semax did not protect SH-SY5Y neuroblastoma cells from copper-induced toxicity. Zinc entry into cells was unaffected ³.
Short 2013 Russian Academy report titled 'Stability of Semax acetyl to proteolysis in various biological media' ⁴; no abstract is available and we could not read the full text, so its findings are not reported here.
For context, FDA's 2026 review of plain Semax found the clinical evidence insufficient for cerebral ischemia, migraine or trigeminal neuralgia, and noted many supporting studies are in Russian ².

Doses studied in people

No published human (or animal) dosing data exist for N-acetyl Semax amidate; doses circulating online are not based on any study of this compound.

Read this first: these are the amounts given to participants in published studies or written on official prescribing labels, reported for reference. They are not recommendations. Trial doses were chosen for specific patients under medical supervision, and a dose that is safe in one person can be harmful in another.

Vial math

Many research vials hold 5 or 10 mg of powder. This table shows how much ends up in each mark on a U-100 insulin syringe for common amounts of added liquid. It is arithmetic only, not a dose.

Vial	Liquid added	Concentration	Per unit (0.01 mL)
5 mg	1 mL	5 mg/mL	50 mcg	Open in calculator
5 mg	2 mL	2.5 mg/mL	25 mcg	Open in calculator
5 mg	3 mL	1.67 mg/mL	16.7 mcg	Open in calculator
10 mg	1 mL	10 mg/mL	100 mcg	Open in calculator
10 mg	2 mL	5 mg/mL	50 mcg	Open in calculator
10 mg	3 mL	3.33 mg/mL	33.3 mcg	Open in calculator

More sizes: all vial sizes · How this works: Syringes and units · Reconstitution guide.

Safety

Unknown: no human or animal safety data on this form have been published.
FDA found insufficient clinical information to describe even plain Semax's safety, could not find any human pharmacokinetic studies, and raised concern about immune reactions from impurities or aggregates in injected or nasal peptide products ².
FDA has noted that different salts and derivatives with different active ingredients are sold under the same 'Semax' name, which can put patients at risk ⁷.
Products sold online are unregulated; identity, purity and dose are not verified by any regulator.

Report side effects of any drug or product to the FDA through MedWatch. For a possible poisoning in the US, call Poison Control at 1-800-222-1222.

Legal status

FDA: Not FDA-approved. No registered human trials found on ClinicalTrials.gov ⁹.
Compounding: N-acetyl Semax amidate is not named on FDA's compounding safety-risk page ⁶. FDA's July 2026 advisory-committee review covered only Semax free base and Semax acetate, and FDA's briefing document concluded the evidence weighs against adding those to the 503A bulks list ²⁸. The modified form was not evaluated. HHS's October 28, 2026 interim enforcement-discretion policy for 503A compounding applies only to the peptide forms listed in its appendix, which for Semax is Semax free base for nasal use; N-acetyl Semax amidate, a different molecule, is not among the listed substances ¹¹¹²¹³.
Sports (WADA): Not named on the WADA 2026 list. Semax has a Russian registration, but this modified form has no approval anywhere, so it appears to fall under S0 (non-approved substances), banned at all times ¹⁰². This is our reading; check with your anti-doping body.
Other: Not approved in any country that we found, including Russia, where only plain Semax is registered ².

Rules change often. See Legal status of peptides for how these categories work.

History

Semax was developed in Russia and is registered there as 0.1% and 1% nasal drops ². Russian chemists published a short 2013 report on the stability of acetylated Semax in biological fluids ⁴, and an Italian group studied N-acetyl Semax's metal-binding in 2016 ³. The doubly modified N-acetyl/amidated form appears in PubChem as a catalog chemical ¹, but we found no peer-reviewed study of it.

Common questions

Is N-Acetyl Semax Amidate the same as Semax?

No. It has the same seven amino acids but with chemical caps on both ends, so it is a different molecule (C39H54N10O10S vs C37H51N9O10S) ¹². It is also different from 'Semax acetate', which is just a salt of Semax ².

Is there research on N-Acetyl Semax Amidate?

We found no peer-reviewed study of this exact form. The closest work is a 2016 cell study of acetylated (not amidated) Semax and a short 2013 Russian report on its stability ³⁴.

Is it stronger or longer-lasting than Semax?

That has not been shown in published studies. Semax is broken down from its N-terminal end, which is the apparent reason for the cap ², but in one cell study acetylation actually removed a protective effect seen with plain Semax ³.

Is it approved anywhere?

No. Only plain Semax is registered, in Russia ². It is not FDA-approved, was not part of FDA's 2026 compounding review of Semax ²⁸, and is not among the peptide forms listed in HHS's October 2026 interim compounding policy ¹²¹³.

Is it banned in sport?

It is not named on WADA's 2026 list, but as an unapproved substance it appears to fall under the S0 class, banned at all times ¹⁰.

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Sources

Wondering how to judge the claims made about compounds like this one? The Academy track Thinking clearly about peptide claims walks through it. You can try the Academy free first.

Last reviewed 2026-10-30 · How we research · Found an error? See our corrections policy.