Selank vs Semax: structure, research and legal status compared
Selank and Semax are short synthetic peptides developed at the Institute of Molecular Genetics of the Russian Academy of Sciences. Both end in the same Pro-Gly-Pro tail, which was added to slow breakdown, but they are built on different natural peptides and have been studied for different effects. This page compares them for laboratory and educational purposes.
- Selank is a tuftsin analogue (TKPR + PGP) studied mainly in anxiety and stress models.
- Semax is an ACTH(4-7) analogue (MEHF + PGP) studied mainly for cognition and neuroprotection.
- Both are registered medicines in Russia but are not approved in the US, UK or EU.
- Semax was recommended by an FDA advisory committee in July 2026; Selank was not part of that review.
Side-by-side comparison
| Selank | Semax | |
|---|---|---|
| Parent peptide | Tuftsin (Thr-Lys-Pro-Arg), an immune peptide | ACTH(4-7) (Met-Glu-His-Phe), a fragment of adrenocorticotropic hormone |
| Sequence | TKPRPGP | MEHFPGP |
| Length | 7 amino acids | 7 amino acids |
| Molecular weight | 751.88 g/mol | 813.93 g/mol |
| Formula | C₃₃H₅₇N₁₁O₉ | C₃₇H₅₁N₉O₁₀S |
| Main research areas | Anxiety and stress models; immune modulation | Cognition, memory and neuroprotection models |
| Where approved | Registered in Russia | Registered in Russia |
| US status | Not FDA-approved; not part of the July 2026 vote | Not FDA-approved; recommended by an FDA advisory committee in July 2026 |
| UK / EU status | Unlicensed; research use only | Unlicensed; research use only |
| WADA | S0 non-approved substance | S0 non-approved substance |
Why both end in Pro-Gly-Pro
Natural tuftsin and ACTH fragments are broken down within minutes. Adding the Pro-Gly-Pro tripeptide to the C-terminus was intended to make both analogues more resistant to peptidases. That shared design is why the two are often grouped together, even though their parent peptides act on different systems.
How strong is the evidence?
Most published work on both peptides comes from Russian research groups, and much of it is in Russian-language journals. Large, independent randomised trials in English-language literature are lacking, which is one reason neither is approved outside Russia. Treat claims of proven effects in people with caution.
Sourcing for a lab
Ask for a batch-specific certificate of analysis showing the full sequence, HPLC purity and mass-spectrometry identity. Some products sold as "N-acetyl" or "amidate" versions are different molecules with different molecular weights. See each profile: Selank and Semax.
Frequently asked questions
What is the difference between Selank and Semax?
Selank is a tuftsin analogue studied mainly in anxiety models. Semax is an ACTH(4-7) analogue studied mainly for cognition and neuroprotection. Both share a Pro-Gly-Pro tail.
Which is better, Selank or Semax?
They have been studied for different effects, and there is no reliable independent human evidence to rank them. Neither is approved in the US, UK or EU.
Are Selank and Semax legal in the US?
Neither is FDA-approved. Semax was recommended for the 503A bulks list by an FDA advisory committee in July 2026, but the vote is not binding. Selank was not part of that review.
Are Selank and Semax legal in the UK?
Neither is licensed by the MHRA. Supplied with medicinal claims they would be unlicensed medicines, and because they are studied for effects on the brain the Psychoactive Substances Act 2016 may also be relevant.
Are Selank and Semax banned by WADA?
They are not approved in WADA-recognised jurisdictions, so they fall under the S0 non-approved substances class, which is prohibited at all times.