Semax vs Selank: Research Comparison
The direct evidence does not establish an overall winner. Three studies compare the peptides directly: a serum-enzyme assay, a rat behaviour study and a short-term brain-imaging study. The rest of the literature uses different models and populations.
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Semax and Selank are distinct seven-residue peptides, but published comparisons do not show that one is broadly better. Three studies tested both: an in-vitro enzyme assay in human serum, where Semax had the lower IC50; a 2017 rat study, whose abstract reports lower anxiety-like behaviour with Selank; and a 2020 brain-imaging study in 52 healthy participants. None is a head-to-head clinical efficacy test, and none supports a general ranking across outcomes.[1][7][2]
Semax vs Selank at a glance
| Research feature | Semax | Selank | What can be concluded |
|---|---|---|---|
| Published sequence | Met-Glu-His-Phe-Pro-Gly-Pro | Thr-Lys-Pro-Arg-Pro-Gly-Pro | Both are heptapeptides ending in Pro-Gly-Pro. Semax is an analog of the ACTH(4-10) fragment; Selank is an analog of tuftsin.[1][3][7] |
| Shared biochemical comparison | IC50 10 µM in the reported assay | IC50 20 µM in the reported assay | These are assay-specific values for inhibition of enkephalin-degrading enzymes in human serum, not a general potency scale.[1] |
| Direct human imaging comparison | One resting-state fMRI study included Semax, Selank and placebo conditions in 52 healthy participants. | The endpoint was functional connectivity measured within 20 minutes of administration. The abstract reports no symptom or treatment outcome.[2] | |
| Direct animal behaviour comparison | No reported change in motor activity or passive defensive behaviour in rats with 6-OHDA lesions | No change in those measures; lower anxiety-like behaviour reported | One small rodent study in a Parkinson-like lesion model; a behavioural measure, not a clinical outcome.[7] |
| Separate mechanistic examples | Rat hippocampal BDNF and TrkB measures | Rat frontal-cortex neurotransmission gene-expression panel | Different brain regions and endpoints do not establish comparative efficacy.[3][4] |
| Clinical-study contexts in indexed records | A 1997 report concerning acute ischemic stroke | A 2008 study concerning generalized anxiety disorder and neurasthenia | Different populations, comparator groups and outcomes; not a direct comparison of the compounds.[5][6] |
The sequence and assay values above come from one paper indexed as an article in Russian with an English-language abstract. The numerical difference belongs to that assay alone and says nothing about concentrations in a living system or about any other outcome.[1]
Same length, different sequence
The published heptapeptide sequences are Met-Glu-His-Phe-Pro-Gly-Pro for Semax and Thr-Lys-Pro-Arg-Pro-Gly-Pro for Selank. Each has seven amino-acid residues, and each ends in Pro-Gly-Pro. The first four residues come from different parent peptides. Semax starts with Met-Glu-His-Phe, residues 4–7 of adrenocorticotropic hormone (ACTH), and is described as an ACTH(4-10) analog. Selank starts with Thr-Lys-Pro-Arg, the sequence of tuftsin, a short immunomodulatory peptide.[1][3][7]
What the direct comparison studies measured
1. A shared enzyme-inhibition assay
Kost and colleagues tested Semax and Selank against enkephalin-degrading enzymes in human serum. The abstract reports IC50 values of 10 µM for Semax and 20 µM for Selank and describes a dose-dependent effect. Both peptides were measured on the same endpoint in the same experiment, and the result is about enzymes in serum.[1]
So Semax had the lower IC50 in this assay. That does not make it “twice as strong” in any wider sense.
2. A short-term resting-state fMRI study
Panikratova and colleagues assessed resting-state functional connectivity in 52 healthy participants. The study used predefined regions of interest that included the amygdala and dorsolateral prefrontal cortex, with scans before and at 5 and 20 minutes after administration of Semax, Selank or placebo. The abstract reports between-condition differences in connectivity between the right amygdala and a right temporal-cortex region, with post-hoc analyses describing both shared and distinct patterns.[2]
The endpoint was a connectivity signal measured within 20 minutes. The abstract reports no anxiety, memory or symptom scores, so a connectivity difference here does not establish a benefit.
3. A 2017 rat behaviour study
Slominsky and colleagues gave Semax or Selank to rats with 6-hydroxydopamine (6-OHDA) lesions, a model of Parkinson-like damage to dopamine neurons. Neither peptide changed motor activity in the elevated plus maze or passive defensive behaviour. The abstract reports lower anxiety-like behaviour in the maze with Selank, in line with earlier Selank results in stressed rodents, and does not report the same effect for Semax. It is one small rodent experiment.[7]
Why separate studies cannot identify a winner
The rest of the literature is not organized around one common test. For example, a 2006 Semax study measured BDNF and TrkB expression and phosphorylation in rat hippocampus. A 2016 Selank study measured expression across 84 neurotransmission-related genes in rat frontal cortex at two time points. These experiments use different tissues, endpoints and protocols; a BDNF result in one cannot be numerically ranked against a gene-expression panel in another.[3][4]
The indexed clinical reports are also from different research settings. A 1997 Semax report describes patients in the acute period of hemispheric ischemic stroke and a conventional-therapy comparison group. A 2008 Selank report describes patients with generalized anxiety disorder and neurasthenia, comparing Selank with medazepam. The diagnoses, comparison groups, study years and outcomes differ; neither paper directly randomizes participants between Semax and Selank.[5][6]
Both records are indexed by PubMed as Russian-language articles, and the abstracts provide only a limited view of study methods. Assessing design details such as allocation, masking, prespecified outcomes and analysis requires the full papers.
A careful way to read “Semax vs Selank”
Start with the question a study actually asks. If the question is enzyme inhibition in human serum, the 2001 assay gives a direct numerical comparison on that defined endpoint. If the question is behaviour in a rodent model, the 2017 rat study tested both. If the question is short-term resting-state connectivity, the 2020 fMRI study includes both peptides and placebo. If the question is a clinical outcome, separate studies in different populations do not create a head-to-head answer.
The direct comparisons are narrow, and the other studies differ in model and endpoint. Semax and Selank have distinct sequences and partly overlapping research literatures. The papers that test both do not show that either one is better overall. For background, see the individual Semax research overview, Selank research overview, and the primer on what peptides are.
Our Research Standards
Sequences, assay values and study details on this page were checked against the cited PubMed records and abstracts on October 20, 2026. In-vitro, animal and human imaging findings are kept separate, and none of the cited studies is a clinical comparison. No therapeutic, human-use or veterinary-use claim is made here.
Frequently asked questions
What is the main difference between Semax and Selank?
Semax is an analog of the ACTH(4-10) fragment and Selank an analog of tuftsin; both are seven residues long and end in Pro-Gly-Pro. The 2020 brain-imaging paper describes Semax as nootropic and Selank as anxiolytic, which matches where each research literature concentrates.
Does the lower Semax IC50 mean Semax is stronger than Selank?
Only for the specific enzyme-inhibition assay reported in the 2001 paper: its abstract lists IC50 values of 10 micromolar for Semax and 20 micromolar for Selank. An assay-specific concentration does not establish comparative clinical efficacy or general potency across other endpoints.
Was Semax directly compared with Selank in people?
A 2020 study measured resting-state brain connectivity in 52 healthy participants before and 5 and 20 minutes after administration of Semax, Selank or placebo. It compared a brain-imaging signal and did not test treatment benefit.
Do the separate Semax and Selank studies show which is better?
No. The single-compound studies measured different things: hippocampal BDNF in rats for Semax, a frontal-cortex gene panel in rats for Selank, stroke recovery against conventional therapy for Semax, and anxiety against medazepam for Selank. None tests both peptides under one protocol.
Does this comparison provide human-use or treatment guidance?
No. This page reports what published studies measured. It gives no dosing, administration or treatment guidance.
For catalog details, see the Genovare Semax 25mg AQ pen, the Genovare Selank 25mg AQ pen and the Selank + Semax blend pen. For compliance context, see the Dubai legality brief and the research standards page.
Sources
- Kost NV, Sokolov OIu, Gabaeva MV, et al. [Semax and selank inhibit the enkephalin-degrading enzymes from human serum]. Bioorg Khim. 2001;27(3):180-183. Article in Russian; English PubMed abstract. English translation: Russ J Bioorg Chem. 2001;27:156-159, doi: 10.1023/A:1011373002885. PMID 11443939.
- Panikratova YR, Lebedeva IS, Sokolov OY, et al. Functional Connectomic Approach to Studying Selank and Semax Effects. Dokl Biol Sci. 2020;490(1):9-11. doi: 10.1134/S001249662001007X. PMID 32342318.
- Dolotov OV, Karpenko EA, Inozemtseva LS, 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. doi: 10.1016/j.brainres.2006.07.108. PMID 16996037.
- Volkova A, Shadrina M, Kolomin T, et al. Selank Administration Affects the Expression of Some Genes Involved in GABAergic Neurotransmission. Front Pharmacol. 2016;7:31. doi: 10.3389/fphar.2016.00031. PMID 26924987.
- Gusev EI, Skvortsova VI, Miasoedov NF, et al. [Effectiveness of semax in acute period of hemispheric ischemic stroke (a clinical and electrophysiological study)]. Zh Nevrol Psikhiatr Im S S Korsakova. 1997;97(6):26-34. Article in Russian; PubMed abstract. PMID 11517472.
- Zozulia AA, Neznamov GG, Siuniakov TS, 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. Article in Russian; PubMed abstract. PMID 18454096.
- Slominsky PA, Shadrina MI, Kolomin TA, et al. Peptides semax and selank affect the behavior of rats with 6-OHDA induced PD-like parkinsonism. Dokl Biol Sci. 2017;474(1):106-109. doi: 10.1134/S0012496617030048. PMID 28702721.