Selank vs Semax: What’s the Difference?
Selank and Semax are both synthetic seven-residue peptides from the Institute of Molecular Genetics of the Russian Academy of Sciences, and both end in the same Pro-Gly-Pro tail, added to slow their breakdown. They differ in where they start.
Selank (TKPRPGP) is the immunopeptide tuftsin, Thr-Lys-Pro-Arg, extended by Pro-Gly-Pro. It is classed as an anxiolytic in Russian sources.
Semax (MEHFPGP) is the ACTH(4-7) fragment, Met-Glu-His-Phe, extended by Pro-Gly-Pro. It is classed as a nootropic in Russian sources.
In short: same stabilising tail, different regulatory fragment in front of it. Both come as vials and as ready-made nasal sprays.
Selank vs Semax at a Glance
Both are linear heptapeptides with free termini and the same C-terminal Pro-Gly-Pro. Selank (C33H57N11O9, 751.9 g/mol) starts with tuftsin; Semax (C37H51N9O10S, 813.9 g/mol) starts with ACTH(4-7). Neither is FDA-approved; a 2022 review lists both as registered in Russia.
| Comparison | Selank | Semax |
|---|---|---|
| Peptide length | 7 amino acids | 7 amino acids |
| Molecular weight | 751.9 g/mol | 813.9 g/mol |
| Sequence | TKPRPGP | MEHFPGP |
| Molecular relationship | Tuftsin + Pro-Gly-Pro | ACTH(4-7) + Pro-Gly-Pro |
| Main research focus | GABAergic and enkephalinase research | BDNF, trkB and neuroprotection research |
| Research evidence | Russian clinical and animal literature | Russian clinical and animal literature |
| FDA-approved drug component | No | No |
What are Selank and Semax
7 AA
Selank
Tuftsin (Thr-Lys-Pro-Arg) with a C-terminal Pro-Gly-Pro, designed for metabolic stability.
Research areas
GABAergic gene expression • Enkephalin-degrading enzymes • BDNF • Anxiolytic models
No single receptor has been identified. Proposed mechanisms include inhibition of enkephalin-degrading enzymes in human plasma and allosteric modulation of GABA signalling, from gene-expression and radioligand studies.
Explore Selank7 AA
Semax
The ACTH(4-7) fragment Met-Glu-His-Phe with a C-terminal Pro-Gly-Pro, usually described as an ACTH(4-10) analogue.
Research areas
BDNF / trkB • Monoamine systems • Focal ischaemia models • Nootropic models
Tritium-labelled Semax binds specific, calcium-dependent sites in rat basal-forebrain membranes (KD 2.4 nM), though no receptor has been named. Intranasal Semax raised BDNF protein in the rat basal forebrain within three hours.
Explore SemaxSelank: TKPR + PGPShared C-terminal Pro-Gly-ProSemax: MEHF + PGP
Same glyproline tail; tuftsin vs ACTH(4-7) in front
Key Differences Between Selank and Semax
| Key differences | Selank | Semax |
|---|---|---|
| Starting fragment | Tuftsin (Thr-Lys-Pro-Arg), a fragment of the immunoglobulin G heavy chain. |
ACTH(4-7) (Met-Glu-His-Phe), from adrenocorticotropic hormone. |
| Russian classification | Anxiolytic. |
Nootropic. |
| Proposed mechanisms | Inhibits enkephalin-degrading enzymes in human plasma (IC50 15 µM); changes GABAergic gene expression in rat frontal cortex. |
Specific binding sites in rat basal forebrain; raises BDNF and trkB phosphorylation in rat hippocampus; modulates serotonin and dopamine in rodent striatum. |
| Clinical literature | Russian comparative studies against benzodiazepines in anxiety disorders, mostly in Russian. |
Russian studies in stroke rehabilitation, mostly in Russian. |
| Molecular formula | C33H57N11O9, 751.9 g/mol, CAS 129954-34-3. |
C37H51N9O10S, 813.9 g/mol, CAS 80714-61-0. |
| Forms we stock | 10 mg vial (ILS Laboratories certificate) and a 20 mg / 20 mL spray. |
10 mg vial (ILS Laboratories certificate) and a 20 mg / 20 mL spray. |
How their research profiles differ
- Selank
- Tuftsin + Pro-Gly-Pro
- Enkephalinase and GABAergic findings
- Anxiolytic-model research
- Semax
- ACTH(4-7) + Pro-Gly-Pro
- BDNF / trkB findings
- Nootropic and ischaemia-model research
Selank vs Semax: Which Is Better?
Neither is better in general. They are built on different regulatory peptides and have been studied for different things: Selank mostly in anxiety-related and GABAergic models, Semax mostly in BDNF, cognition and ischaemia models.
Their evidence is similar in kind: animal pharmacology plus Russian clinical studies, largely published in Russian. Neither has a registered trial on ClinicalTrials.gov, and no head-to-head clinical comparison has been published.
One human imaging study did look at both: in 52 healthy participants, resting-state fMRI showed some effects shared by Selank and Semax and some specific to each.
Is the research question about the tuftsin-derived (Selank) or the ACTH-derived (Semax) glyproline?
Can Selank and Semax Be Studied Together?
They have been: the 2020 fMRI study by Panikratova et al. compared Selank, Semax and placebo in the same design, as separate groups, and separated shared from peptide-specific effects.
Studying them as separate arms keeps each peptide's contribution attributable. Combining them in one condition would make that impossible, because both carry the same Pro-Gly-Pro unit and overlapping reported effects.
There Isn’t One Universal “Winner”
Selank
Tuftsin glyproline
TKPRPGP • GABAergic • enkephalinase
Semax
ACTH(4-7) glyproline
MEHFPGP • BDNF • trkB
Compare the Research. Verify the Material.
Our Selank and Semax vials are each analysed by ILS Laboratories in San Diego: HPLC purity, net peptide content and identity by HPLC retention time, with sterility, endotoxin, heavy metals and a fentanyl screen on the same certificate.
The 20 mg / 20 mL sprays are filled from their own lots, with certificates on their product pages.
Research use only
Identity
verified
Purity
verified
Endotoxin
verified
Tested
in USA
Research use only- Identity
verified - Purity
verified - Endotoxin
verified - Tested
in USA
Question
Frequently Asked
What is the difference between Selank and Semax?
Both are heptapeptides ending in Pro-Gly-Pro. Selank starts with tuftsin (Thr-Lys-Pro-Arg); Semax starts with the ACTH(4-7) fragment (Met-Glu-His-Phe).
Are Selank and Semax from the same lab?
Yes. Both were developed at the Institute of Molecular Genetics of the Russian Academy of Sciences; Selank with the V.V. Zakusov Research Institute of Pharmacology.
What are the Selank and Semax sequences?
Selank is TKPRPGP (H-Thr-Lys-Pro-Arg-Pro-Gly-Pro-OH). Semax is MEHFPGP (H-Met-Glu-His-Phe-Pro-Gly-Pro-OH).
Were Selank and Semax studied as nasal sprays?
Intranasal administration appears in the published animal studies of both, for example Volkova et al. 2016 for Selank and Dolotov et al. 2006 for Semax.
What is the difference between the vial and the spray?
Same peptide, different form. The vials are 10 mg of lyophilised powder; the sprays are 20 mg already in a 20 mL solution.
Are Selank and Semax FDA-approved?
No. A 2022 review lists both as registered in Russia. FDA lists both among bulk substances nominated, then withdrawn, from its compounding safety-risk category.
Is N-acetyl Semax the same as Semax?
No. N-acetyl Semax amidate (Ac-MEHFPGP-NH2) is a modified molecule with no peer-reviewed literature of its own that we found. Our Semax is unmodified.
Research Peptides. Documented by Batch.
Every size in the catalogue ships against the certificate issued for its own lot.
For laboratory research use only. Not for human or veterinary use.
References
Identity data come from PubChem. Findings are paraphrased from the PubMed abstracts; Russian-language papers are summarised from their English abstracts.
- Volkova A, et al. Selank Administration Affects the Expression of Some Genes Involved in GABAergic Neurotransmission Frontiers in Pharmacology, 2016. Origin of Selank and intranasal gene-expression study in rats.
- Zozulya AA, 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.
- Dolotov OV, et al. Semax, an analogue of adrenocorticotropin (4-10), binds specifically and increases levels of brain-derived neurotrophic factor protein in rat basal forebrain Journal of Neurochemistry, 2006.
- 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.
- Panikratova YR, et al. Functional Connectomic Approach to Studying Selank and Semax Effects Doklady Biological Sciences, 2020. fMRI in 52 healthy participants.
- Deigin VI, et al. Development of Peptide Biopharmaceuticals in Russia Pharmaceutics, 2022. Lists Selank and Semax among registered Russian peptide products.
- PubChem Selank, CID 11765600 Formula, molecular weight and CAS.
- PubChem Semax, CID 9811102 Formula, molecular weight and CAS.
