Selank and Semax: Nootropic Peptides in Research

Selank and Semax are synthetic heptapeptides developed at the Institute of Molecular Genetics of the Russian Academy of Sciences. Semax is derived from a fragment of the hormone ACTH and has been studied mainly for cognitive and neuroprotective effects; Selank is derived from the immune peptide tuftsin and has been studied mainly as an anxiolytic. Both are registered medicines in Russia but have no MHRA, EMA or FDA authorisation, and in the UK they are sold as research chemicals for laboratory use only.

This guide explains where the two peptides come from, how they are thought to work, what the published animal and human research shows, and what UK researchers need to know before buying them.

What are nootropic peptides?

Nootropic is a loose term for compounds studied for effects on memory, attention, learning or mood. Nootropic peptides are short amino acid chains, often based on fragments of natural neuropeptides, that have been investigated for these effects. Unlike classical stimulants they tend to act on signalling molecules such as brain-derived neurotrophic factor (BDNF) and on neurotransmitter systems rather than directly raising arousal.

Both Selank and Semax share a structural trick. Each is a natural four-amino-acid fragment with the tripeptide Pro-Gly-Pro attached to the C-terminus. The PGP tail resists enzymatic breakdown and extends the peptide's activity in the brain from minutes to hours, which was the key innovation of the Russian research group led by Nikolai Myasoedov.

Interest in Selank and Semax outside Russia has grown mainly through the nootropics community, but the peptides are also used as tools by neuroscience laboratories investigating BDNF signalling, stress physiology and the pharmacology of the Pro-Gly-Pro motif itself. UK search interest tends to cluster around the comparison between the two, which this article addresses directly below.

Semax: the ACTH-derived cognitive peptide

Semax has the sequence Met-Glu-His-Phe-Pro-Gly-Pro. The first four residues are ACTH(4-7), a fragment of adrenocorticotropic hormone that retains effects on attention and memory in animal models but has no hormonal activity on the adrenal glands. Semax was developed in the 1980s and registered in Russia in the 1990s, where it is used as an intranasal preparation for ischaemic stroke and for cognitive complaints.

The most-cited mechanistic finding is from Dolotov and colleagues, published in the Journal of Neurochemistry in 2006. Intranasal Semax produced a rapid increase in BDNF protein and its receptor TrkB in the basal forebrain of rats within hours. Later work from the same institute reported that Semax altered the expression of hundreds of genes in the rat brain after experimental stroke, including those involved in immune response and vascular repair.

Human data comes almost entirely from Russian clinical studies, mostly small and often not placebo-controlled by Western standards. Reported outcomes include improved neurological recovery scores after stroke and improved performance on attention tasks in healthy volunteers under fatigue. These studies are informative but have not been replicated in large Western trials, and Semax has never been submitted for licensing in the UK, EU or US.

Selank: the tuftsin-derived anxiolytic peptide

Selank has the sequence Thr-Lys-Pro-Arg-Pro-Gly-Pro. The first four residues are tuftsin, a natural immunomodulatory tetrapeptide, again stabilised by a PGP tail. It was developed by the same institute in collaboration with the V.V. Zakusov Research Institute of Pharmacology and registered in Russia as an anxiolytic in the late 2000s.

The animal literature describes Selank as producing anxiolytic effects in standard rodent tests such as the elevated plus maze without the sedation or memory impairment associated with benzodiazepines. Proposed mechanisms include positive modulation of GABA-A receptors, changes in serotonin and enkephalin metabolism, and altered expression of genes involved in GABAergic signalling. Russian clinical studies, including work by Zozulya and colleagues published in 2008, compared Selank with medazepam in patients with generalised anxiety disorder and reported comparable reductions in anxiety scores.

As with Semax, the evidence base is largely Russian and small in scale. There are no large independent randomised trials, and Selank has no marketing authorisation outside Russia and some neighbouring countries.

Selank vs Semax: side-by-side comparison

Although the two peptides are often mentioned together, they were designed for different purposes and their research profiles reflect that. The table summarises the main differences.

How Selank and Semax are used in laboratory research

Outside Russia, both peptides are used mainly as research tools in neuroscience and pharmacology. Common study designs include:

• Rodent behavioural models of anxiety (elevated plus maze, open field) and cognition (Morris water maze, novel object recognition).
• Neurochemical assays measuring BDNF, TrkB, serotonin metabolites and enkephalin degradation in brain tissue.
• Gene expression studies in the hippocampus and frontal cortex after peptide exposure.
• Neuroprotection models such as middle cerebral artery occlusion, where Semax has been studied for effects on infarct size and recovery.
• Immunology work on Selank, which retains some of tuftsin's reported effects on cytokine balance and interferon expression.

Both peptides are relatively stable in lyophilised form but degrade in solution over weeks, and Semax in particular is sensitive to oxidation at its methionine residue. Pre-filled, precision-made pens can help laboratories avoid the variability that comes from repeated reconstitution.

Are Selank and Semax legal in the UK?

Yes. Selank and Semax are legal to buy, sell and possess in the UK as research chemicals. Neither is controlled under the Misuse of Drugs Act 1971. The Psychoactive Substances Act 2016 is sometimes raised in relation to nootropics, but it targets substances supplied for their psychoactive effect in humans; peptides sold and used strictly for laboratory research fall outside that purpose.

Neither peptide has an MHRA marketing authorisation, so supplying them for human medicinal use, or advertising them with claims about treating anxiety or improving memory, is unlawful under the Human Medicines Regulations 2012. Reputable UK suppliers describe them as research reagents and make no such claims.

Sourcing Selank and Semax in the UK

Both peptides are short and inexpensive to synthesise, so purity rather than cost is the main concern. Truncated or oxidised sequences are the most common problems, and both can be picked up by proper HPLC and mass spectrometry. Because the two peptides are close in size, a supplier that does not publish mass spectrometry data cannot show you which one is actually in the pen.

1. Ask for a batch-specific certificate of analysis. Calibre pens are tested by Janoshik Analytical and the COAs are published on the COA page.
2. Check the mass spec result matches the expected molecular weight (Semax is roughly 814 Da; Selank roughly 752 Da).
3. Confirm HPLC purity; Calibre targets above 99%.
4. Store lyophilised material cold and protected from light, and check the batch date on the COA.

Summary

Selank and Semax are the two best-known nootropic peptides, both Russian-designed heptapeptides stabilised by a Pro-Gly-Pro tail. Semax has been studied mainly for BDNF-linked cognitive and neuroprotective effects, Selank mainly as a non-sedating anxiolytic acting on GABA and serotonin systems. The evidence is largely preclinical and Russian clinical, with no Western licensing. In the UK both are legal research chemicals with no MHRA authorisation, and should be bought with an independent certificate of analysis.