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Research / Semax vs Selank
Reference comparison

Semax vs Selank: key differences in structure and research

Null Bio Lab Research Desk · Last reviewed October 18, 2026 · Research use only

Scope. This article summarises published laboratory literature for readers working with Semax and Selank as a research reagent. It gives no dosing, administration or usage guidance, and nothing here is a statement about any use in humans or animals. Neither compound is an authorised medicine in the EU or US.

Comparison table

SemaxSelank
Parent peptideACTH fragment (4–7 / 4–10)Tuftsin (Thr-Lys-Pro-Arg)
SequenceMEHFPGPTKPRPGP
Stabilising tailPro-Gly-ProPro-Gly-Pro
Monoisotopic mass813.35 Da ([M+H]+ 814.36)751.43 Da ([M+H]+ 752.44)
Charge characterAcidic/aromatic residues (Glu, His, Phe)Basic residues (Lys, Arg)
Main research areasNeurotrophin expression, ischaemia-model transcriptomics, monoamine systemsEnkephalin degradation, GABAergic gene expression, immune-related genes
Typical model systemsRat brain, glial culturesRat, mouse, IMR-32 cells
Established receptor targetNot establishedNot established
Status in EU/USNot an authorised medicineNot an authorised medicine

Masses were calculated from the sequences; confirm against the mass reported on any batch COA.

What they share

Both carry the PGP tail,12 both originate in the same Russian research tradition, and both were examined at the transcript level in rodent models. Both are susceptible to enzymatic degradation in biological fluids, which is why the stabilising motif exists at all.3

Where they differ

Semax is built from a neuroendocrine fragment and its published mechanism work leans toward neurotrophins and brain transcriptomics.45 Selank is built from an immune-system peptide, and its mechanism work leans toward enkephalin metabolism, GABA-pathway genes and immune-related expression.678 Their sequences also differ in charge: Selank carries two basic residues (Lys, Arg) while Semax carries acidic and aromatic ones, which affects how each behaves in chromatography.

The studies that cover both

Two biochemical reports tested both compounds directly. One found that both inhibit enkephalin-degrading enzymes from human serum.9 Another compared the anticoagulant-related effects of glyprolines, Semax and Selank, discussing the specificity of each.10 For most other questions, head-to-head data are lacking, so conclusions comparing the two are inferences across separate studies.

Read next: Semax explained · Selank explained · COA guide for short peptides.

Frequently asked questions

What is the main structural difference between Semax and Selank?

Semax is built from an ACTH fragment (MEHFPGP); Selank from the tuftsin tetrapeptide (TKPRPGP). Both end in Pro-Gly-Pro.

Do Semax and Selank act on the same target?

Neither has an established single receptor target. Published work points Semax toward neurotrophin gene expression and Selank toward enkephalin-degrading enzymes and GABAergic gene expression, mostly in rodent and cell models.

Which has more published research?

Both have a body of mostly Russian-group literature; head-to-head studies are rare, so comparisons are inferences across separate studies.

How do I tell them apart on a COA?

By measured mass: Semax [M+H]+ ≈ 814.36, Selank ≈ 752.44. See the COA guide.

References

  1. Dmitrieva VG, Povarova OV, Skvortsova VI, Limborska SA, Myasoedov NF, Dergunova LV. Semax and Pro-Gly-Pro activate the transcription of neurotrophins and their receptor genes after cerebral ischemia. Cellular and Molecular Neurobiology. 2010;30(1):71–79. doi:10.1007/s10571-009-9432-0. PMID 19633950.
  2. Vyunova TV, Andreeva L, Shevchenko K, Myasoedov N. Peptide-based anxiolytics: the molecular aspects of heptapeptide Selank biological activity. Protein and Peptide Letters. 2018. doi:10.2174/0929866525666180925144642. PMID 30255741.
  3. Potaman VN, et al. Degradation of ACTH/MSH(4–10) and its synthetic analog semax by rat serum enzymes: an inhibitor study. Peptides. 1993. doi:10.1016/0196-9781(93)90137-6.
  4. Dolotov OV, et al. Semax, an analog of ACTH(4–10) with cognitive effects, regulates BDNF and trkB expression in the rat hippocampus. Brain Research. 2006. doi:10.1016/j.brainres.2006.07.108.
  5. Medvedeva EV, 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. doi:10.1186/1471-2164-15-228.
  6. Zozulya AA, Kost NV, Sokolov OY, et al. The inhibitory effect of Selank on enkephalin-degrading enzymes as a possible mechanism of its anxiolytic activity. Bulletin of Experimental Biology and Medicine. 2001. doi:10.1023/a:1017979514274. PMID 11550013.
  7. 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. PMID 26924987.
  8. Kolomin T, Shadrina M, Andreeva L, et al. Expression of inflammation-related genes in mouse spleen under tuftsin analog Selank. Regulatory Peptides. 2011. doi:10.1016/j.regpep.2011.05.001. PMID 21609736.
  9. Kost NV, Sokolov OIu, Gabaeva MV, et al. Semax and selank inhibit the enkephalin-degrading enzymes from human serum. Bioorganicheskaia Khimiia. 2001. doi:10.1023/a:1011373002885. PMID 11443939.
  10. Liapina LA, Pastorova VE, Obergan TIu, et al. Comparison of anticoagulant effects of regulatory proline-containing oligopeptides: specificity of glyprolines, semax, and selank. Izvestiia Akademii Nauk. Seriia Biologicheskaia. 2006. doi:10.1134/s1062359006020099. PMID 16634437.

Related reading

For newly published papers on this and other peptides, see the live feed on the Research Desk.