The short version: Selank and Semax share a design, a developer and a research base, but not a parent molecule. Selank starts from tuftsin, an immune peptide; Semax starts from residues 4 to 7 of ACTH. Semax is a prescription drug in Russia; Selank is used there too but its registration is harder to verify. Neither is licensed in the UK, the EU or the US, and neither is named by WADA.
Side by side
| Point | Selank | Semax |
|---|---|---|
| Parent | Tuftsin, a four-residue immune peptide | ACTH (4–7), a fragment of the pituitary stress hormone |
| Shared tail | Pro-Gly-Pro | Pro-Gly-Pro |
| Length | 7 residues | 7 residues |
| Avg mass | 751.9 g/mol | 813.9 g/mol |
| Formula | C33H57N11O9 | C37H51N9O10S |
| CAS | 129954-34-3 | 80714-61-0 |
| Developer | Institute of Molecular Genetics, Russian Academy of Sciences | Same institute |
| First described | 1990s1 | 19915 |
| Human studies | Small Russian clinical studies in anxiety2 | Older Russian clinical studies; registration as a medicine6 |
| Status in Russia | Used clinically; registration to be checked1 | Prescription medicine; on the vital and essential drugs list6 |
| UK, EU, US | Not licensed | Not licensed |
| WADA | Not named | Not named |
One design, two parents
Both peptides follow the same idea: take a short natural fragment with reported effects on the brain, and add Pro-Gly-Pro to the end so blood enzymes cut it more slowly. The tail is the same; the fragments are not. Tuftsin comes from an antibody and acts on immune cells. ACTH (4–7) is the core of a hormone that, in full, drives cortisol release, although the four-residue piece does not include the part that does so.1,5
Both have been reported to inhibit the enzymes that break down enkephalins in human serum, in the same 2001 paper, and both have been reported to raise BDNF in the rat hippocampus.3,4,7
What was measured for each
| Area | Selank | Semax |
|---|---|---|
| Clinical | Anxiety scores against a benzodiazepine in Russian patients with anxiety disorders2 | Registered in Russia; the clinical claims rest on older Russian studies6 |
| Brain chemistry | BDNF in rat hippocampus4 | BDNF and its receptor TrkB in rat hippocampus7 |
| Enzymes | Enkephalin-degrading enzymes in human serum, inhibited3 | Same study, same finding3 |
| Receptors | Not characterised | Proposed to act at melanocortin receptors8 |
| Neurotransmitters | Not a main line of work | Dopamine and serotonin systems in rodents9 |
| Immune | Immune markers in patients with anxiety-asthenic disorders10 | Not a main line of work |
What this means for a readerTreat both evidence bases as regional. Almost every study comes from the developing institute or its partners and many are in Russian-language journals, so the designs and sizes are hard to check from outside. Semax has the stronger regulatory footing, as a registered medicine in Russia; Selank has the more specific clinical question, anxiety, but in small studies.
Status and sport
Neither is licensed in the UK, the EU or the US, and neither is a controlled drug in the UK. Semax is a prescription medicine in Russia and has been on the government's list of vital and essential medicines since 2011. Selank is used clinically in Russia; we have not verified its current registration.1,6
Neither is named on the 2026 WADA list. Class S0 covers substances with no approval anywhere; Semax's Russian approval may take it outside S0, and Selank's position depends on its registration. Athletes should check with their anti-doping body.11
Common questions
What is the difference between Selank and Semax?
The parent fragment. Selank is built on tuftsin, an immune peptide; Semax is built on residues 4 to 7 of ACTH. Both carry the same Pro-Gly-Pro tail and come from the same Russian institute.
Are Selank and Semax approved anywhere?
Semax is a prescription medicine in Russia. Selank is used clinically in Russia; its registration should be checked against the Russian register. Neither is approved in the UK, the EU or the US.
Which has more evidence?
Both rest mostly on Russian studies. Semax has the longer literature and a drug registration; Selank has small clinical studies in anxiety. Neither has an independent Western trial.
Do they act the same way?
Partly. Both inhibit enkephalin-degrading enzymes and raise BDNF in rats. Semax has also been linked to melanocortin receptors and to dopamine and serotonin systems.
Are Selank and Semax banned in sport?
Neither is named on the 2026 WADA list. Whether class S0 applies depends on their approval status, so athletes should check with their anti-doping body.
References
- Wikipedia. Selank, for identifiers and origin, checked 2 Nov 2026.
- Zozulia AA, et al. Efficacy and possible mechanisms of action of a new peptide anxiolytic selank in the therapy of generalized anxiety disorders and neurasthenia. Zh Nevrol Psikhiatr Im S S Korsakova. 2008;108(4):38–48. PMID 18454096
- Kost NV, et al. Semax and selank inhibit the enkephalin-degrading enzymes from human serum. Bioorg Khim. 2001;27(3):180–183. PMID 11443939
- Inozemtseva LS, et al. Intranasal administration of the peptide Selank regulates BDNF expression in the rat hippocampus in vivo. Dokl Biol Sci. 2008;421:241–243. PMID 18841804
- Potaman VN, et al. [First description of Semax and its degradation by rat blood enzymes]. Biochem Biophys Res Commun. 1991;176(2):741–746. PMID 1851003
- Wikipedia. Semax, citing the Russian List of Vital and Essential Drugs (7 December 2011), checked 2 Nov 2026.
- Dolotov OV, 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. PMID 16996037
- Bertolini A, et al. [Semax as a melanocortin receptor antagonist]. Eur J Pharmacol. 2012;679(1–3):1–8. PMID 22293371
- Eremin KO, et al. Semax, an ACTH(4-10) analogue with nootropic properties, activates dopaminergic and serotoninergic brain systems in rodents. Neurochem Res. 2005;30(12):1493–1500. PMID 16362768
- Uchakina ON, et al. Immunomodulatory effects of selank in patients with anxiety-asthenic disorders. Zh Nevrol Psikhiatr Im S S Korsakova. 2008;108(5):71–75. PMID 18577961
- World Anti-Doping Agency. The 2026 Prohibited List. wada-ama.org
Peptidarium Library. Selank vs Semax (comparison 04), 2 November 2026. peptidarium.com/compare/selank-vs-semax