Scientifically reviewed by Dr Stephan Hansberg
Selank and Semax: structure, research and legal status (2026)
Selank and Semax are synthetic heptapeptides developed in Russia, both ending in Pro-Gly-Pro. Their identity data side by side, origins, research by model, the July 2026 FDA review of Semax and their status with the MHRA, TGA and WADA.
Key takeaways
- •Selank (Thr-Lys-Pro-Arg-Pro-Gly-Pro) is the immunopeptide tuftsin extended with Pro-Gly-Pro; Semax (Met-Glu-His-Phe-Pro-Gly-Pro) is the ACTH(4-7) fragment extended the same way.
- •Both were developed at the Institute of Molecular Genetics of the Russian Academy of Sciences; the Pro-Gly-Pro tail was added for metabolic stability.
- •Published work is mostly rodent studies of gene expression and behaviour, plus Russian-language clinical reports for Semax; neither has a study registered on ClinicalTrials.gov.
- •Semax is a registered drug in Russia. In July 2026 FDA staff proposed not adding it to the 503A bulks list; the advisory committee recommended it, and rulemaking was pending. Selank was not reviewed.
- •Neither is approved in the US, UK or Australia, and neither is named on the WADA 2026 List. Celyfe sells neither.
What are Selank and Semax?
Selank and Semax are two synthetic seven-amino-acid peptides developed in Russia, each built by taking a short fragment of a natural peptide and adding the tripeptide Pro-Gly-Pro to its end. Selank is based on tuftsin, a fragment of immunoglobulin G, and Semax is based on a fragment of adrenocorticotropic hormone (ACTH).
They are often discussed together because they share an origin, a design principle and the same research institute, but they are different molecules with different parent peptides. Most published research is in rodents; Semax is registered as a medicine in Russia, while neither is approved in the US, UK or Australia.
Identity side by side
Identifiers checked against PubChem and, for Semax, the FDA's July 2026 briefing document.
| Property | Selank | Semax |
|---|---|---|
| Sequence (7 aa) | Thr-Lys-Pro-Arg-Pro-Gly-Pro (TKPRPGP) | Met-Glu-His-Phe-Pro-Gly-Pro (MEHFPGP) |
| Parent peptide | Tuftsin (Thr-Lys-Pro-Arg), a fragment of the IgG heavy chain | ACTH(4-7) (Met-Glu-His-Phe); usually described as an ACTH(4-10) analogue |
| Molecular formula | C33H57N11O9 | C37H51N9O10S |
| Molar mass | 751.9 g/mol | 813.9 g/mol (free base) |
| CAS number | 129954-34-3 | 80714-61-0 (free base); 2828433-33-4 cited by FDA for the acetate |
| PubChem CID | 11765600 | 9811102 |
| FDA UNII | TS9JR8EP1G | I5FAL2585H |
| Contains methionine | No | Yes (position 1) |
Origins
Selank was developed at the Institute of Molecular Genetics of the Russian Academy of Sciences in cooperation with the Zakusov Research Institute of Pharmacology. As Volkova and colleagues describe it, the tuftsin sequence Thr-Lys-Pro-Arg was elongated at the C-terminus with Pro-Gly-Pro to improve its metabolic stability.
Semax comes from the same institute's work on regulatory peptides. The FDA's 2026 briefing describes it as a heptapeptide and synthetic analogue of the ACTH(4-10) fragment; structurally, its first four residues are ACTH(4-7), followed by the same Pro-Gly-Pro tail. The FDA briefing also notes that Semax is a registered drug in Russia, supplied as nasal drops.
What has been studied, by model
Representative published studies are below. Rodent findings describe experimental observations, and the Semax clinical reports are Russian-language studies that do not meet the standard of registered randomised trials.
| Peptide | Research area | Model | Example study (year, PMID) |
|---|---|---|---|
| Both | Inhibition of enkephalin-degrading enzymes | Human serum in vitro | Kost et al., Bioorg Khim (2001), PMID 11443939 |
| Selank | Depression-like behaviour in genetic and stress models | Animal (rat, mouse) | Sarkisova et al., Zh Vyssh Nerv Deiat (2008), PMID 18661785 |
| Selank | GABAergic neurotransmission gene expression, frontal cortex | Animal (rat) | Volkova et al., Front Pharmacol (2016), PMID 26924987 |
| Selank | GABAergic gene expression | Human neuroblastoma cell line (IMR-32) | Filatova et al., Front Pharmacol (2017), PMID 28293190 |
| Semax | BDNF and TrkB expression, hippocampus | Animal (rat) | Dolotov et al., Brain Res (2006), PMID 16996037 |
| Semax | Neurotrophin gene expression in brain | Animal (rat) | Agapova et al., Neurosci Lett (2007), PMID 17353092 |
| Semax | Ischaemic stroke, clinical report | Human (Russian-language) | Gusev et al., Zh Nevrol Psikhiatr (2018), PMID 29798983 |
| Semax | Brain gene expression after experimental stroke | Animal (rat) | Filippenkov et al., Biomedicines (2024), PMID 39767736 |
How the two compare
The table summarises the practical differences researchers usually ask about.
| Question | Selank | Semax |
|---|---|---|
| Parent system | Immune (tuftsin, from IgG) | Endocrine (ACTH fragment) |
| Main research themes | Anxiety-related behaviour, GABAergic gene expression, inflammation-related genes (rodent and cell models) | Neurotrophin (BDNF) expression, experimental ischaemia (rodent models); Russian clinical reports |
| Registered on ClinicalTrials.gov | No studies found (Oct 2026) | No studies found (Oct 2026) |
| Russian registration | Not confirmed from an official source by us | Registered drug (nasal drops), per FDA briefing |
| FDA July 2026 compounding review | Not reviewed | Reviewed; FDA staff proposed not adding; committee recommended; rulemaking pending |
| Oxidation-prone residue | None of the usual (no Met, Cys or Trp) | Methionine at position 1 |
Human trial status
A search of ClinicalTrials.gov in October 2026 found no registered interventional studies of either Selank or Semax. The Semax human literature consists mainly of Russian clinical reports, for example in ischaemic stroke, and the FDA briefing summarised several such reports in its review.
Regulatory status in 2026
Semax was reviewed at the FDA's Pharmacy Compounding Advisory Committee on 24 July 2026. FDA staff proposed that neither Semax free base nor Semax acetate be added to the 503A bulks list, citing gaps in characterisation data and concern about immunogenicity for injectable and intranasal products. The committee recommended adding it; rulemaking had not concluded as of October 2026. Selank was not on the agenda.
| Authority | Selank | Semax |
|---|---|---|
| US FDA | Not an approved drug; not reviewed in 2026 | Not an approved drug; PCAC recommended 503A listing (Jul 2026) against FDA staff proposal; rulemaking pending |
| UK MHRA | No UK marketing authorisation | No UK marketing authorisation |
| AU TGA | Not named in the Poisons Standard (Oct 2026 instrument) | Not named in the Poisons Standard (Oct 2026 instrument) |
| WADA 2026 | Not named; check with your anti-doping organisation | Not named; check with your anti-doping organisation |
Stability and handling notes
The shared Pro-Gly-Pro tail was chosen to slow enzymatic breakdown, and proline-rich sequences are generally resistant to many common peptidases. Semax's N-terminal methionine is prone to oxidation, so methionine sulfoxide is a realistic impurity for Semax and not for Selank. Selank is strongly basic (lysine and arginine), while Semax carries a glutamate and a histidine, so the two behave differently in chromatography.
The FDA briefing listed both free base and acetate forms of Semax as commercially available and noted it is often unclear which form a source describes. As with any peptide, the certificate should state the form tested.
Open questions
For both peptides, the mechanisms proposed in rodent work have not been tied to a defined receptor, independent replication outside the originating Russian groups is limited, and there are no registered, controlled trials outside Russia. For Semax, the FDA also flagged a lack of characterisation and immunogenicity data for the product forms proposed for compounding.
Where Celyfe fits
Celyfe does not sell Selank or Semax, and no Celyfe pen contains either. For any source of these peptides, the batch certificate is the document to check: it should name the peptide and form, the identity method and the HPLC purity. The COA library at /coa shows Celyfe's own published certificates, NAD+ batch A26085 and WOLVERINE batch C26071 from Analiza Bialek, as reference examples.
Sources
Primary and official sources checked October 2026:
- PubChem: Selank, CID 11765600; Semax, CID 9811102 (pubchem.ncbi.nlm.nih.gov)
- FDA: Briefing document for Semax-related bulk drug substances, Pharmacy Compounding Advisory Committee, 23-24 July 2026 (fda.gov)
- Kost NV et al. Semax and selank inhibit the enkephalin-degrading enzymes from human serum. Bioorg Khim, 2001. PMID 11443939
- Sarkisova KIu et al. Effects of heptapeptide selank on depression-like behaviour in WAG/Rij and Wistar rats and BALB/c mice. Zh Vyssh Nerv Deiat Im I P Pavlova, 2008. PMID 18661785
- Volkova A et al. Selank administration affects the expression of some genes involved in GABAergic neurotransmission. Front Pharmacol, 2016. PMID 26924987
- Filatova E et al. GABA, Selank, and olanzapine affect the expression of genes involved in GABAergic neurotransmission in IMR-32 cells. Front Pharmacol, 2017. PMID 28293190
- 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. PMID 16996037
- Agapova TY et al. Neurotrophin gene expression in rat brain under the action of Semax, an analogue of ACTH 4-10. Neurosci Lett, 2007. PMID 17353092
- Gusev EI et al. Semax at different stages of ischemic stroke (in Russian). Zh Nevrol Psikhiatr Im S S Korsakova, 2018. PMID 29798983
- Filippenkov IB et al. ACTH-like peptides and rat brain gene expression after experimental stroke. Biomedicines, 2024. PMID 39767736
- ClinicalTrials.gov searches for Selank and Semax, October 2026 (no registered interventional studies)
- AJMC: FDA panel backs 6 peptides for compounding, 31 July 2026
- Therapeutic Goods (Poisons Standard, October 2026) Instrument 2026, F2026L01327 (legislation.gov.au)
- WADA: Prohibited List 2026, in force 1 January 2026 (wada-ama.org)
Research use only
Celyfe supplies research peptides for laboratory and research use only. Nothing on this page is guidance on use in humans or animals.
Research updates
Peptide research and testing, in your inbox
New batch certificates, regulation changes and a monthly digest of new published research on the compounds we cover. No spam, unsubscribe at any time.