Selank vs Semax: How Russia’s Two Nootropic Peptides Differ

Selank and Semax are short synthetic peptides developed in Russia and sold elsewhere as nasal-spray nootropics, but they are built on different natural molecules. Semax is based on a fragment of ACTH, a stress hormone, and has been studied mainly in stroke and cognition. Selank is based on tuftsin, an immune peptide, and has been studied mainly for anxiety. Human evidence for both is small.

They are often discussed as a pair, with Semax cast as the focusing one and Selank as the calming one. That split is a simplification. It rests largely on animal work and a handful of Russian clinical studies, many published only in Russian and several co-authored by the peptides’ developers.

Below we compare what each is, what the research shows, safety and anti-doping questions, legal status as of September 2026, and how to judge a product’s paperwork. We give no dosing or usage guidance.

At a glance

Property	Selank	Semax
Parent molecule	Tuftsin, an immune-system peptide	ACTH(4-10), a fragment of a stress hormone
Sequence	Thr-Lys-Pro-Arg-Pro-Gly-Pro	Met-Glu-His-Phe-Pro-Gly-Pro
Main research focus	Anxiety and asthenia	Stroke recovery and cognition
Proposed mechanism	Enkephalin-enzyme inhibition; GABA-related gene effects in rats	BDNF and trkB signalling in rats
Human evidence	One small trial against medazepam (62 patients)	Small Russian stroke studies, e.g. 110 patients
FDA approval	Not approved	Not approved
FDA compounding review	Nomination withdrawn; no pending review	Panel voted 8-5 in favour (July 2026), non-binding
WADA 2026	Not named; status unclear	Not named; status unclear
Typical product form	Nasal spray or vial	Nasal spray or vial

Two peptides, two different parent molecules

Semax is the heptapeptide Met-Glu-His-Phe-Pro-Gly-Pro. It is described as an analogue of the ACTH(4-10) fragment, and after application into the nose in rats it has effects on learning and markers of nerve protection.¹ Selank is the heptapeptide Thr-Lys-Pro-Arg-Pro-Gly-Pro.³ Its first four amino acids are tuftsin, a naturally occurring immune peptide.

The parent molecules explain the different research directions. ACTH is a pituitary hormone best known for signalling the adrenal glands during stress, and short ACTH fragments have long interested researchers for their effects on attention and learning. Tuftsin is a small fragment of an antibody protein that acts on immune cells, which is why Selank research spans both mood and immune markers.

Both end in the same three amino acids, Pro-Gly-Pro, and both came out of work linked to the Institute of Molecular Genetics of the Russian Academy of Sciences.¹⁵ Beyond that shared tail, they are different molecules with different starting points, and research on one says nothing direct about the other.

Our glossary entries on Semax and Selank cover the naming and history in more detail.

Mechanisms and reported effects: not as neat as focus versus calm

The best-known Semax finding is from rats. A single application raised brain-derived neurotrophic factor (BDNF) protein in the hippocampus by up to 1.4-fold and increased activation of its receptor, trkB, and treated animals performed more conditioned avoidance responses.¹ That is the basis for most cognitive claims, and it is animal data.

For Selank, a 2001 laboratory study found it inhibited the enzymes that break down enkephalins, the body’s own opioid-like peptides, and the authors proposed this as a mechanism for its anti-anxiety effect.³ A later rat study found changes in the expression of genes involved in GABA signalling, and the authors suggested it may act partly through the GABA system.⁵ Both are hypotheses built on lab and animal work.

In practice, online users tend to describe Semax as alerting and Selank as settling. Yet the main Selank clinical study itself reported anti-asthenic and psychostimulant effects alongside reduced anxiety.⁴ The tidy stimulant-versus-calmer framing is mostly a product of marketing and anecdote.

Evidence quality: small studies, mostly in Russian

The Semax human data come largely from Russian clinical studies in stroke. In one 2018 study, 110 patients recovering from ischaemic stroke were split by rehabilitation timing and by whether they received Semax. Those given Semax had higher blood BDNF levels and improved faster on the Barthel index of daily functioning.² The abstract does not describe randomisation, blinding or a placebo, and the paper is in Russian.

The main Selank clinical study compared it with medazepam, a benzodiazepine, in 62 patients with generalised anxiety disorder or neurasthenia (30 on Selank, 32 on medazepam). Anti-anxiety effects were similar between groups.⁴ There was no placebo arm, the sample was small, and the developers were among the authors.

Question	Selank	Semax
Placebo-controlled trials in English-language journals	None found	None found
Studies in healthy people seeking cognitive gains	None found	None found
Main human setting	Anxiety and neurasthenia	Stroke and cerebrovascular disease
Head-to-head comparison	None	None

There is a wider problem of access. Much of this literature sits in Russian journals, often with only a short English abstract, which makes it hard for outside researchers to check methods, dropouts or how outcomes were chosen. Positive findings are also more likely to be published than null ones, and the developers’ institutes have an obvious interest in the results.

None of this shows the peptides do nothing. It shows that the evidence is too thin, too narrow and too dependent on one research tradition to support the confident claims made for either, least of all in healthy people using them as nootropics.

Safety, side effects and drug testing

The small Russian studies describe both peptides as well tolerated, but they were not designed or large enough to find uncommon harms. FDA’s own review is blunter. For Selank acetate it cited immunogenicity risk and said it lacks important information on safety issues in humans; for Semax it cited immunogenicity and said it has no, or limited, safety-related information.⁶

Interactions with anxiety medicines, antidepressants, stimulants or alcohol have not been properly studied. Nasal sprays are sometimes assumed to be low risk because they are not injected, but a contaminated or non-sterile spray still delivers whatever it contains to the nasal lining.

Selank’s comparison with a benzodiazepine sometimes gets read as a sign it can stand in for prescribed anxiety treatment. The study does not support that reading.⁴ Anyone taking prescribed medicine for anxiety, depression or attention problems should discuss any additional product with their prescriber.

Neither peptide is named on WADA’s list. The S0 category bans substances with no current approval by any governmental health authority for human use, and a 2025 review of brain doping substances placed both Selank and Semax in an unclear-status group.⁹ Athletes should seek a ruling from their anti-doping organisation rather than assume either is permitted. Routine workplace drug panels do not look for these peptides.

Legal status in September 2026

United States. Neither is an FDA-approved drug, and their regulatory paths have now split. Semax was one of 12 peptides FDA moved out of Category 2 in April 2026.⁶⁸ On 24 July 2026 the Pharmacy Compounding Advisory Committee voted 8-5, with one abstention, to recommend adding Semax to the 503A bulks list; its nominated uses were cerebral ischaemia, migraine and trigeminal neuralgia.⁷⁸ The vote is advisory, and FDA must complete rulemaking before pharmacies can rely on it.¹²

Selank acetate’s nomination was withdrawn earlier and it sits on FDA’s list of withdrawn substances, with FDA noting it lacks human safety information.⁶ It was not on the July 2026 agenda, so no compounding pathway is pending. The same two-day meeting also covered BPC-157, discussed in our report on the BPC-157 advisory vote, and our 503A bulks list explainer sets out the steps that remain.

UK. Neither is a licensed medicine. Canada. Health Canada’s April 2026 advisory says peptides are generally regulated as prescription drugs and that research use only labelling does not make products legal.¹⁰

Research use only labels and what a COA should show

Outside Russia, almost all Selank and Semax is sold online as research use only, often as ready-made nasal sprays. A ready-to-use spray is hard to square with a research-only claim. In a March 2026 warning letter, FDA said that despite research use only labels, evidence from a seller’s website showed the products were intended for human use.¹¹ Our guide to what research use only means covers the loophole.

A credible COA should show:

• HPLC purity, with the chromatogram attached.
• Mass spectrometry identity confirming the correct sequence. Modified versions sold under names such as N-acetyl Semax are different molecules, and the studies above do not describe them.
• Endotoxin and sterility results, including for nasal sprays and multi-use bottles.
• The amount of peptide per bottle or spray, measured by assay rather than stated from the recipe. Without it, the concentration on the label is an assertion.
• Any preservative used in a spray, the lot number matching the product, the laboratory’s name and a recent date.

It is worth contacting the laboratory named on a certificate to confirm it issued that report for that lot.

Frequently asked questions

Has Selank or Semax been studied for anxiety?

Selank has. A small Russian study of 62 patients with generalised anxiety disorder or neurasthenia found anti-anxiety effects similar to the benzodiazepine medazepam, without a placebo group.⁴ Semax has been studied mainly in stroke and cognition rather than anxiety.² Neither is approved for any condition in the US, UK or Canada, and this is not a recommendation to use either.

Can you take Selank and Semax together?

Combination sprays and pairings are widely promoted, but we found no published controlled study testing the two together in humans. Each has only small, mostly Russian-language human studies on its own, and interactions have not been properly studied. We do not provide usage or combination guidance.

Is Semax legal in the US?

Semax is not FDA-approved. In July 2026 an FDA advisory committee voted 8-5 to recommend adding it to the list of substances compounding pharmacies may use, but that vote is not binding and FDA must still complete rulemaking.⁸¹² Online research use only sales are not a lawful route for human use.

Do Selank and Semax need a prescription?

In the US there is no FDA-approved Selank or Semax product to prescribe, and neither is currently on the list compounding pharmacies may use, although Semax could be added if FDA acts on the July 2026 vote.¹² In Canada, peptides are generally regulated as prescription drugs.¹⁰ In the UK, neither is a licensed medicine.

Are Selank and Semax banned by WADA?

Neither is named on WADA’s Prohibited List. However, the S0 section covers substances without current government approval for human use, and a 2025 review classed both as having unclear status.⁹ Athletes subject to testing should get a formal answer from their national anti-doping organisation before assuming either is allowed.

Is Semax a stimulant?

Not in the pharmacological sense that caffeine or amphetamine are. The mechanism most studied is an increase in BDNF and its receptor activity in the rat brain.¹ Users often describe it as alerting, but that is anecdotal. The labels are loose in both directions: the main Selank trial also reported psychostimulant effects.⁴

Sources

1. Dolotov OV, Karpenko EA, Inozemtseva LS, Seredenina TS, Levitskaya NG, Rozyczka J, et al. Semax, an analog of ACTH(4-10) with cognitive effects, regulates BDNF and trkB expression in the rat hippocampus. Brain Res. 2006;1117(1):54-60. DOI: 10.1016/j.brainres.2006.07.108. PMID: 16996037. pubmed.ncbi.nlm.nih.gov
2. Gusev EI, Martynov MY, Kostenko EV, Petrova LV, Bobyreva SN. [The efficacy of semax in the treatment of patients at different stages of ischemic stroke]. (Article in Russian.) Zh Nevrol Psikhiatr Im S S Korsakova. 2018;118(3 Vyp 2):61-68. DOI: 10.17116/jnevro20181183261-68. PMID: 29798983. pubmed.ncbi.nlm.nih.gov
3. Zozulya AA, Kost NV, Sokolov OY, Gabaeva MV, Grivennikov IA, Andreeva LN, et al. The inhibitory effect of Selank on enkephalin-degrading enzymes as a possible mechanism of its anxiolytic activity. Bull Exp Biol Med. 2001;131(4):315-317. DOI: 10.1023/a:1017979514274. PMID: 11550013. pubmed.ncbi.nlm.nih.gov
4. Zozulia AA, Neznamov GG, Siuniakov TS, Kost NV, Gabaeva MV, Sokolov OIu, et al. [Efficacy and possible mechanisms of action of a new peptide anxiolytic selank in the therapy of generalized anxiety disorders and neurasthenia]. (Article in Russian.) Zh Nevrol Psikhiatr Im S S Korsakova. 2008;108(4):38-48. PMID: 18454096. pubmed.ncbi.nlm.nih.gov
5. Volkova A, Shadrina M, Kolomin T, Andreeva L, Limborska S, Myasoedov N, Slominsky P. Selank Administration Affects the Expression of Some Genes Involved in GABAergic Neurotransmission. Front Pharmacol. 2016;7:31. DOI: 10.3389/fphar.2016.00031. PMID: 26924987. pubmed.ncbi.nlm.nih.gov
6. U.S. Food and Drug Administration. Certain Bulk Drug Substances for Use in Compounding that May Present Significant Safety Risks. Page updated 22 April 2026. fda.gov
7. U.S. Food and Drug Administration. July 23-24, 2026: Meeting of the Pharmacy Compounding Advisory Committee (agenda and materials). fda.gov
8. McDermott. Bulk-list bound? PCAC backs majority of peptides in two-day public meeting. 27 July 2026. mcdermottlaw.com
9. Pokrywka A, Surała O, Grabowska K, et al. “Brain doping” substances: prohibited or not in sports? Biol Sport. 2025;42(4):189-202. DOI: 10.5114/biolsport.2025.150047. termedia.pl
10. Health Canada. Think twice before injecting peptides bought online: unauthorized products can seriously harm you. Public advisory, 9 April 2026. recalls-rappels.canada.ca
11. U.S. Food and Drug Administration, CDER. Warning Letter: Gram Peptides (MARCS-CMS 721806). 31 March 2026. fda.gov
12. Buchanan Ingersoll & Rooney. FDA Advisory Committee Voted Yes on Six Peptides. Now What? The Regulatory Road Ahead. 18 August 2026. bipc.com

Editorial note: This article is for general information only and is not medical or legal advice. Selank and Semax have not been evaluated by the FDA to diagnose, treat, cure or prevent any disease. Laws vary by location and change often, so verify the rules that apply where you are. Always talk to a licensed healthcare provider before use, especially if you are under 21, pregnant or nursing, taking medication, or managing a health condition.