Semax and Selank are two synthetic heptapeptides: short chains of seven amino acids. Semax is derived from a fragment of the pituitary hormone ACTH, Selank from tuftsin, a small peptide that forms part of an antibody. Both come from Russian research and end in the same three building blocks: Pro-Gly-Pro [1][2]. In Russia they are registered as medicines [3]. In the European Union they have no marketing authorisation [4]. Below we explain how they are built, how their status differs between Russia and the EU, and what to look out for in analysis and storage.
Two heptapeptides with the same tail
Semax has the sequence Met-Glu-His-Phe-Pro-Gly-Pro. The first four amino acids match positions 4 to 7 of ACTH (adrenocorticotropic hormone). They are followed by the tripeptide Pro-Gly-Pro [1]. In the literature, Semax is therefore often called ACTH(4-7)PGP, or an analogue of the fragment ACTH(4-10). That longer fragment has the sequence Met-Glu-His-Phe-Arg-Trp-Gly. In Semax, the last three building blocks have been replaced by Pro-Gly-Pro. According to the researchers, this tail makes the peptide more resistant to breakdown by peptidases, the enzymes that cut protein chains [1].
Selank has the sequence Thr-Lys-Pro-Arg-Pro-Gly-Pro. The first four building blocks form tuftsin, a short fragment of the heavy chain of human immunoglobulin G, one of the antibodies in the blood. Here too, Pro-Gly-Pro has been added to the end of the chain [2]. Selank was designed at the Institute of Molecular Genetics of the Russian Academy of Sciences, together with the Zakusov Institute of Pharmacology in Moscow [2].
Structure at a glance
| Feature | Semax | Selank |
|---|---|---|
| Sequence | Met-Glu-His-Phe-Pro-Gly-Pro | Thr-Lys-Pro-Arg-Pro-Gly-Pro |
| Derived from | ACTH(4-7), part of ACTH(4-10) | tuftsin (Thr-Lys-Pro-Arg) |
| Molecular formula | C37H51N9O10S (PubChem CID 9811102) | C33H57N11O9 (PubChem CID 11765600) |
| Molar mass | 813.9 g/mol | 751.9 g/mol |
| Notable feature | contains methionine (sulphur atom) | contains lysine and arginine (positively charged) |
The sulphur atom in the formula of Semax belongs to the methionine at the start of the chain. In Russian laboratory research, Selank was used as the diacetate salt [2].
Status in Russia and in the EU
Russia. Semax and Selank are authorised as medicines in Russia [3]. Semax is also included in the Russian government’s list of ‘vital and essential medicines’ (annex to order No. 2406-r of 12 October 2019) [1]. Most of the published research on both peptides comes from Russian research groups.
European Union. An authorisation in Russia does not apply in the EU. That requires a separate marketing authorisation, either centrally through the European Medicines Agency (EMA) or nationally in each member state. Semax and Selank do not appear in the EMA’s medicines overview, which also includes withdrawn applications [4]. We are not aware of any EU authorisation for these substances. The US FDA has not approved them either.
Sport. WADA’s 2026 Prohibited List does not name Semax or Selank [5]. The list does, however, use open groups (‘including but not limited to’). Whether a substance falls under one of them is for the anti-doping organisations to decide.
Semax and Selank from Clean Peptides are research materials (research use only). They are not the same as the Russian medicines and are not intended for use in humans or animals.
What research exists
- Animal research. A large part of the literature concerns experiments in rats and mice. Researchers looked, for example, at gene expression in brain tissue after exposure to the peptide [2], or at behaviour and tissue changes in mouse models [1].
- Clinical research. Clinical studies have also been published, mostly from Russia [1]. We are not aware of international registration studies that meet EU requirements.
- Derivatives. There is also research on variants of Semax in which two amino acids in the middle of the chain have been replaced [1].
We deliberately do not discuss outcomes here. The fact that a substance is authorised as a medicine in one country says nothing about products that were not made under pharmaceutical rules.
Analysis and storage
- Identity. Mass spectrometry (MS) lets you check whether the measured mass matches the sequence: 813.9 g/mol for Semax and 751.9 g/mol for Selank. Because both end in Pro-Gly-Pro, some fragments in MS/MS can be identical. The start of the chain makes the difference.
- Oxidation. The methionine in Semax can oxidise. This produces a separate peak and a mass that is 16 daltons higher.
- Purity and content. Short, highly polar peptides such as Selank elute relatively early in reversed-phase HPLC. The salt (for example acetate) counts towards the weighed powder, but not towards the peptide content. See Purity, endotoxins and heavy metals in peptides and How to read a certificate of analysis (COA).
- Storage. As freeze-dried powder: dry, cool and dark. See Storing peptides.
Every Clean Peptides vial has a batch number on the label. Record it with every experiment.
Products and further reading
Products
The range includes Semax 5 mg, Semax 10 mg, Selank 5 mg and Selank 10 mg, each as freeze-dried powder in a vial. Solvent for the lab: bacteriostatic water 3 ml or 10 ml.
Further reading
- What are peptides? Key terms explained
- Storing peptides
- Research use only (RUO)
- Knowledge base: peptides and research materials explained
Sources
- Radchenko AI, Kuzubova EV, Apostol AA, et al. The potential of the peptide drug Semax and its derivative for correcting pathological impairments in the animal model of Alzheimer’s disease. Acta Naturae 2025;17(4):110–120. doi:10.32607/actanaturae.27808
- 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. doi:10.3389/fphar.2016.00031
- Renke G, Chinellato L. Therapeutic peptides in aesthetic, metabolic and endocrine conditions: effects, safety, clinical applications, and future perspectives. International Journal of Molecular Sciences 2026;27(9):3890. doi:10.3390/ijms27093890
- European Medicines Agency. Download medicine data, medicines overview including withdrawn applications (accessed 6 October 2026)
- World Anti-Doping Agency. Prohibited List 2026 (accessed 6 October 2026)
For laboratory research only. Clean Peptides products are not intended for use in humans or animals. This article provides general information and is not medical advice.
