Semax vs Selank: why the research is not a league table

Research-use notice: this article is for legitimate laboratory and educational research only. It does not provide guidance for human use, administration, dosing or treatment.

Semax is a synthetic analogue of the adrenocorticotropic hormone (ACTH) 4–10 fragment with a Pro-Gly-Pro (PGP) extension, and Selank is a synthetic analogue of tuftsin, a four-amino-acid fragment of immunoglobulin G. Both were developed in Russia, both are seven amino acids long, and both end in the same PGP tripeptide. Most published research on them uses rats, and the human studies are small and mostly published in Russian-language journals. A Russian medicines reference lists both as registered medicines in Russia. Neither is a licensed medicine in the UK, and the evidence cannot rank one above the other.

What are Semax and Selank?

Semax is the heptapeptide Met-Glu-His-Phe-Pro-Gly-Pro. A 2014 paper from its developers describes it as the ACTH(4–7) fragment joined to a C-terminal PGP tripeptide. A 2018 review by the same group, and the Russian medicines reference Vidal, call it an analogue of the ACTH(4–10) fragment; other papers use “ACTH(4–7)PGP”. These names all refer to the same molecule.

Selank is Thr-Lys-Pro-Arg-Pro-Gly-Pro. Its first four residues are tuftsin, a fragment of the immunoglobulin G heavy chain that Najjar and Nishioka described in Nature in 1970 as a natural phagocytosis-stimulating peptide. A 2016 paper by Selank’s developers states that tuftsin was extended at the C-terminus with PGP to increase its metabolic stability and give it a longer duration of action.

The shared PGP tail is one reason the two are discussed together. It does not make them interchangeable: the parent peptides are unrelated, and the studies on each asked different questions.

Where were Semax and Selank developed?

Both are associated with the Institute of Molecular Genetics (IMG) of the Russian Academy of Sciences in Moscow. Selank’s developers state that it was designed and produced at IMG in cooperation with the V.V. Zakusov Research Institute of Pharmacology. A 2016 overview in the Herald of the Russian Academy of Sciences by Nikolay Myasoedov of IMG sets out the design concept behind both peptides. It reports that drugs based on them have been developed and that their production and introduction into clinical practice have been organised.

Vidal, a Russian medicines reference, lists Semax and Selank as registered medicines in Russia, with registration certificates dated 2025, both held by Peptogen, a Russian research and production company. It lists Semax as a prescription medicine and Selank as available without a prescription. We have not checked these entries against the official Russian state register. Either way, Russian registration has no bearing on UK status.

What the published research covers

The studies below are a sample chosen to show the main study types. This is not a systematic review.

Semax: animal studies

A 2006 study in Brain Research measured brain-derived neurotrophic factor (BDNF) and its receptor, trkB, in the rat hippocampus after a single administration of Semax. The authors reported higher BDNF protein levels, more trkB phosphorylation (a marker of receptor activation) and higher messenger RNA (mRNA) levels for both. A 2014 genome-wide study in BMC Genomics compared gene expression in rats 3 and 24 hours after permanent middle cerebral artery occlusion, a model of focal ischaemic stroke, with and without Semax. It reported changes mainly in immune-related and vascular genes. A 2020 study in Genes used a transient occlusion (ischaemia–reperfusion) model and reported lower expression of inflammation-related genes, and higher expression of neurotransmission-related genes, in the Semax group than in the saline group at 24 hours.

All three are rat studies. They measured proteins and gene expression in brain tissue, which are not measures of memory, mood or behaviour in people.

Selank: animal studies

A 2016 study in Frontiers in Pharmacology measured the expression of 84 genes involved in neurotransmission in rat frontal cortex, 1 and 3 hours after Selank or gamma-aminobutyric acid (GABA). The authors reported significant changes in 45 of these genes at 1 hour, and a positive correlation between the patterns seen after the two compounds. They proposed allosteric modulation of the GABA system as one possible mechanism. The study measured gene expression, not anxiety or behaviour.

Semax and Selank in the same assay

One 2001 study tested both peptides in the same experiment. Working with human serum in vitro, it reported that both inhibited enzymes that break down enkephalins, with Semax the more potent of the two in that assay. Five-residue fragments of each also showed inhibition, while three-, four- and six-residue fragments did not. This is a test-tube enzyme assay. It compares the two on one narrow measure; it does not rank their effects in animals or people.

Human studies

The human literature is small, and most of it appears in Russian-language journals. Two examples, both in the Zhurnal Nevrologii i Psikhiatrii imeni S.S. Korsakova:

• Semax (2018): a study of 110 people in the early or late period after ischaemic stroke. Each group was divided into subgroups that did or did not receive Semax alongside rehabilitation, and the authors measured blood BDNF, motor function and a daily-living scale, the Barthel Index.
• Selank (2015): an open-label study of 70 patients with anxiety disorders, comparing phenazepam, a benzodiazepine, alone (30 patients) with phenazepam plus Selank (40 patients). It used anxiety rating scales, cognitive tests, a tolerability scale and a quality-of-life questionnaire. Its authors include Nikolay Myasoedov of IMG.

Both reports concluded in favour of the peptide. Neither describes a placebo control or blinding, and both were small, so neither can attribute its findings to the peptide with confidence. These are early human studies, not confirmatory trials. As far as we know, neither has been followed by an independent, randomised, blinded, placebo-controlled trial.

Reviews

A 2018 review by Koroleva and Myasoedov in Biology Bulletin summarises experimental and clinical data on Semax published between 1980 and 2016. It is a narrative review from the developing group, not a systematic review.

Semax vs Selank: why the evidence is not a league table

A “versus” search suggests a ranking. The evidence cannot support one, for four reasons.

• No head-to-head study in animals or people. The only experiment we found that tested both is the 2001 enzyme assay, and we know of no animal or human comparison. Placing two separate papers side by side does not create one.
• Different questions. The Semax studies above mostly examined stroke models and BDNF. The Selank studies examined GABA-related genes and anxiety rating scales. The outcomes do not share a scale.
• Different evidence levels. An enzyme assay, rat gene-expression data and small unblinded human studies answer different questions and carry different risks of bias.
• Limited independent replication. All but one of the Semax and Selank studies cited here list Nikolay Myasoedov of IMG as an author, and most of the human work appears in Russian-language journals. That makes independent scrutiny harder.

The CONSORT (Consolidated Standards of Reporting Trials) 2025 guideline for randomised trials puts the general point simply: “To interpret a trial accurately, readers need complete and transparent information on its methods and findings.” A fair comparison of Semax and Selank would need a randomised, blinded study of both against a control, with prespecified outcomes and full reporting. Until one exists, the useful comparison is of evidence type, model, outcome and limitations, as in the table above. Our overview of nootropic peptides and what counts as evidence sets out that hierarchy in more detail.

How to check a Semax or Selank batch

The two peptides are the same length and share their last three residues, so a name on a label is not enough. When you read a batch laboratory report, check:

• The batch number matches the vial label.
• Identity is confirmed by mass spectrometry. Their first four residues differ, so their masses differ. Calculated from the sequences, the monoisotopic masses of the free peptides are about 813.3 Da for Semax and 751.4 Da for Selank (average molecular weights about 813.9 and 751.9). Check which value a report quotes. A name without a mass result does not distinguish them.
• Purity is read correctly. A high-performance liquid chromatography (HPLC) area percentage describes a separation. It is not a statement of identity or sterility.
• The method, date and laboratory reference are stated.

For a two-peptide set, each vial needs its own identity confirmation. Our guides on how to read a peptide COA and HPLC vs mass spectrometry explain the methods, and our storage guide covers keeping short peptides stable. You can look up any Thistle batch on our batch report lookup.

Thistle supplies Semax — 10mg Research Peptide at £24.99 and Selank — 10mg Research Peptide at £24.99, each with a batch laboratory report.

Are Semax and Selank legal in the UK?

Neither Semax nor Selank is a licensed medicine in the UK. Searches of the electronic medicines compendium (eMC), which publishes information on UK licensed medicines, returned no matches for either name, and we are not aware of any UK marketing authorisation for either.

How a product is presented matters. Under the Human Medicines Regulations 2012, a substance presented as having properties of preventing or treating disease in people is a medicinal product, as is one that may be used by or administered to people with a view to restoring, correcting or modifying a physiological function. In April 2026 the Medicines and Healthcare products Regulatory Agency (MHRA) said that if clinics make medicinal claims for peptide treatments, the products will be considered medicines under those Regulations. That is why this article describes research and makes no claims about memory, anxiety or any other effect in people.

Sport has its own rules. We did not find Semax or Selank named on the World Anti-Doping Agency (WADA) 2026 Prohibited List. The list also has open categories, such as S0, which covers pharmacological substances not addressed elsewhere on the list and with no current approval by any governmental regulatory health authority for human therapeutic use. How these apply to a particular substance is for anti-doping organisations to decide, so athletes should check with theirs rather than rely on a name being absent.

This section is general information, not legal advice.

Semax vs Selank FAQs

Which is better, Semax or Selank?

The evidence cannot say. We are not aware of any animal or human study that compared them directly, and the published work on each used different models and measurements.

What is the difference between Semax and Selank?

Semax is an analogue of an ACTH fragment, and Selank is an analogue of tuftsin. They share only the Pro-Gly-Pro ending, and the research on each asked different questions.

Can Semax and Selank be used together?

We are not aware of any published animal or human study of the two given together. Neither is licensed for human use in the UK, there are no human safety data for research material, and we cannot advise on personal use.

Are Semax and Selank banned in sport?

We did not find either named on the WADA 2026 Prohibited List, but the list includes open categories. Anyone subject to anti-doping rules should check with their anti-doping organisation.

How much does Selank cost in the UK?

Prices vary by supplier. At the time of writing, Thistle sells Selank 10mg at £24.99. Price says nothing about content or purity, so check the batch report.

Sources

• Dolotov OV, Karpenko EA, Inozemtseva LS, et al. Semax, an analog of ACTH(4-10) with cognitive effects, regulates BDNF and trkB expression in the rat hippocampus. Brain Research. 2006;1117(1):54–60. Rats.
• Medvedeva EV, Dmitrieva VG, Povarova OV, et al. The peptide semax affects the expression of genes related to the immune and vascular systems in rat brain focal ischemia: genome-wide transcriptional analysis. BMC Genomics. 2014;15:228. Rat stroke model.
• Filippenkov IB, Stavchansky VV, Denisova AE, et al. Novel Insights into the Protective Properties of ACTH(4-7)PGP (Semax) Peptide at the Transcriptome Level Following Cerebral Ischaemia–Reperfusion in Rats. Genes. 2020;11(6):681. Rat stroke model.
• Volkova A, Shadrina M, Kolomin T, et al. Selank Administration Affects the Expression of Some Genes Involved in GABAergic Neurotransmission. Frontiers in Pharmacology. 2016;7:31. Rats.
• Kost NV, Sokolov OYu, Gabaeva MV, et al. Semax and Selank Inhibit the Enkephalin-Degrading Enzymes of Human Serum. Russian Journal of Bioorganic Chemistry. 2001;27(3):156–159. In vitro.
• Gusev EI, Martynov MYu, Kostenko EV, et al. The efficacy of semax in the treatment of patients at different stages of ischemic stroke. Zhurnal Nevrologii i Psikhiatrii imeni S.S. Korsakova. 2018;118(3-2):61–68. Human study; Russian-language journal.
• Medvedev VE, Tereshchenko ON, Kost NV, et al. Optimization of therapy for anxiety disorders with the peptide drug Selank. Zhurnal Nevrologii i Psikhiatrii imeni S.S. Korsakova. 2015;115(6):33–40. Open-label human study; Russian-language journal.
• Koroleva SV, Myasoedov NF. Semax as a Universal Drug for Therapy and Research. Biology Bulletin. 2018;45(6):589–600. Narrative review.
• Najjar VA, Nishioka K. ‘Tuftsin’: a Natural Phagocytosis Stimulating Peptide. Nature. 1970;228:672–673.
• Myasoedov NF. Innovative drugs: From basic research to production. Herald of the Russian Academy of Sciences. 2016;86(3):151–157. Developer’s overview.
• Hopewell S, Chan AW, Collins GS, et al. CONSORT 2025 statement: updated guideline for reporting randomised trials. BMJ. 2025;389:e081123. Reporting guideline.
• Vidal, Russian medicines reference. Semax and Selank entries. Registration certificates dated 26 March 2025 and 15 July 2025; accessed 3 October 2026.
• The Human Medicines Regulations 2012, regulation 2. legislation.gov.uk. Definition of a medicinal product.
• Electronic medicines compendium (eMC). Product search. Searches for “semax” and “selank” returned no matches, 3 October 2026.
• World Anti-Doping Agency. Prohibited List 2026. S0 non-approved substances.
• Aesthetics Journal. MHRA investigates clinics following peptide claims. 15 April 2026.

Published by Thistle BioLabs, a UK supplier of research materials. This article summarises external research, not studies conducted by Thistle. Educational information only; no medical advice or recommendation for personal use.