Semax and Selank — peptides registered in one country and unstudied in most others
Both came out of the same Moscow institute, both are registered medicines in Russia, and neither holds a marketing authorisation in the European Union, the United Kingdom or the United States. What that evidential split does and does not let a reader conclude — and why no effect figure appears anywhere on this page.
Semax and Selank are the two compounds in this catalogue with the strangest paperwork. Both were developed at the Institute of Molecular Genetics of the Russian Academy of Sciences in Moscow, both end in the same three amino acids, both are registered medicines in the Russian Federation, and neither holds a marketing authorisation in the European Union, the United Kingdom or the United States.
Neither of those last two facts cancels the other, and the temptation is to let one of them do all the work. Treat the Russian registration as an approval and a reader ends up citing a regulator that never examined the compound. Dismiss the Russian literature and a reader throws away several decades of published work, some of it careful and most of it simply hard to reach.
The honest reading sits between those two positions, and getting to it means being concrete about what a reader outside Russia can actually check. That question turns out to shape everything that can responsibly be said about either peptide, so this post answers it first and describes the molecules second.
What can be counted from outside Russia
207
Records in PubMed for Semax
quoted search term · 87 of them in Russian (1)
68
Records in PubMed for Selank
quoted search term · 29 of them in Russian (1)
1 and 2
Of those, records indexed as randomised controlled trials
Semax and Selank respectively (1)
0
Registered studies naming either compound as an intervention
ClinicalTrials.gov · both searched (2)
One tail, two parents
Semax is a synthetic heptapeptide, Met-Glu-His-Phe-Pro-Gly-Pro (4). Dolotov and colleagues describe it as an analogue of the N-terminal 4-10 fragment of adrenocorticotropic hormone; Radchenko and colleagues, writing nearly two decades later, describe the same molecule as a hybrid carrying the ACTH(4-7) fragment together with the tripeptide Pro-Gly-Pro (3, 4). Those are two ways of counting one compound, and both appear below with the paper each came from.
The parent fragment ends in Arg-Trp-Gly. Semax carries Pro-Gly-Pro in its place, and Radchenko and colleagues state that the resulting peptide exhibits no hormonal activity and that the added tripeptide affords increased resistance to peptidase activity (3). A piece of a hormone that has been made to stop behaving as one is the whole design idea, and it is the best-sourced claim in this post.
Selank is a synthetic heptapeptide, Thr-Lys-Pro-Arg-Pro-Gly-Pro (5). Its first four residues are tuftsin, a short natural immunopeptide; Filatova and colleagues describe Selank as a synthetic analogue of it and credit the same C-terminal Pro-Gly-Pro with metabolic stability and duration of action (7). The rat work cited here for Selank comes from the same Moscow institute — Volkova, Shadrina, Kolomin, Andreeva, Limborska, Slominsky and Myasoedov all give the Institute of Molecular Genetics as their affiliation (6).
So the two share a design trick and a laboratory, and share very little else. Different parent fragment, different proposed pathway, different registered indication in the one country that registered them. Whatever binds these two peptides together, it is not a pharmacology.
The two designs
ACTH(4-10)
What Semax was built from
Met-Glu-His-Phe, a stretch of adrenocorticotropic hormone. The 2006 binding paper calls Semax an analogue of the hormone's 4-10 fragment; the 2025 paper calls it a hybrid of ACTH(4-7) and Pro-Gly-Pro. The same molecule is meant in both cases, and the later paper is the one that states the peptide exhibits no hormonal activity (3, 4).
Tuftsin
What Selank was built from
Thr-Lys-Pro-Arg, a short natural immunopeptide. Selank is described in the published work as a synthetic analogue of it, with the tripeptide Pro-Gly-Pro at the end of the molecule providing metabolic stability and duration (5, 7).
Pro-Gly-Pro
The tail both of them carry
The same three residues, at the same end, added to two unrelated fragments. It is credited with resistance to peptidase activity in the Semax literature and with metabolic stability in the Selank literature (3, 7). Both of those claims come from the groups that designed the molecules, which is worth holding in mind, and neither is a claim about anything measured in a person.
What the human literature reports
Three clinical reports were located for this post, and all three are in the same journal, Zhurnal Nevrologii i Psikhiatrii imeni S. S. Korsakova, in Russian. They are also precisely the three records that PubMed's publication-type filter returns as randomised controlled trials for these compounds — one for Semax and two for Selank (1).
Zozulia and colleagues studied 62 patients with generalised anxiety disorder and neurasthenia, 30 given selank and 32 given the benzodiazepine medazepam, and reported that the anxiolytic effects of both drugs were similar while selank additionally had antiasthenic and psychostimulant effects (9). Medvedev and colleagues set 30 patients on phenazepam monotherapy against 40 on phenazepam and selank combined, and reported that the combination decreased the level of undesirable side effects of phenazepam (10). Serdiuk and colleagues gave semax to 27 patients with motor neuron disease and reported that it influenced neither the course of chronic partial denervation nor the dynamics of the clinical estimates, while significantly improving the total quality-of-life estimate, maximally around day 10 (11).
The fourth human study located is not a clinical trial at all. Panikratova and colleagues scanned 52 healthy participants by resting-state fMRI before and at 5 and 20 minutes after injection of selank, semax or placebo (12). It is the only located human study that administered both compounds, and it measured connectivity in people who were not ill rather than benefit in people who were. If a head-to-head comparison of these two peptides exists, that study is not it, and neither is this post.
That is what the trial filter returns: three small reports without a placebo arm between them, one imaging study, and no registered study of either compound in ClinicalTrials.gov (2). Other human reports exist in this literature — the Semax product page in this store cites one on ischaemic stroke rehabilitation — and they are subject to the same limitation described below, which is that they name their instruments without publishing values from them.
The four human reports located for this post
- Selank in anxiety disorders — Zozulia 2008
- 62 patients with generalised anxiety disorder and neurasthenia; 30 given selank, 32 given the benzodiazepine medazepam. Reported result: the anxiolytic effects of both drugs were similar, and selank had also antiasthenic and psychostimulant effects. Published in Russian; MEDLINE indexes both intranasal and oral administration without the abstract stating which arm used which (9).
- Selank added to phenazepam — Medvedev 2015
- 30 patients on phenazepam monotherapy against 40 on combined selank and phenazepam, with SF-36 used for quality of life. Reported result: the combination decreased the level of undesirable side effects of phenazepam. Published in Russian; no SF-36 value appears in the abstract (10).
- Semax in motor neuron disease — Serdiuk 2007
- 27 patients, assessed with the Norris ALS scale, the ALS Functioning Rating Scale, ALSAQ-40 and electromyography. Reported result: no influence on chronic partial denervation or on the clinical estimates, with a significant improvement in the total quality-of-life estimate, maximal around day 10. Published in Russian (11).
- Both peptides in healthy volunteers — Panikratova 2020
- 52 participants, resting-state fMRI before and at 5 and 20 minutes following injection of selank, semax or placebo. An imaging study in healthy people, and the only located human study that gave both compounds. The route here is injection, not the intranasal route used in the rodent work below (12).
- Registered trials
- A search of ClinicalTrials.gov returns no study naming either compound as an intervention (2).
- What none of the three clinical reports publishes
- A scale score, a between-group difference, a confidence interval, a measure of dispersion or a p-value — in the material reachable from outside Russia (9, 10, 11).
Why this post publishes no effect figure
Every figure in the row at the top of this page counts records. None of them measures an effect, and that is deliberate. Each of the three clinical reports names its instruments — the Hamilton, Zung and CGI scales in one, SF-36 in another, the Norris ALS scale, the ALS Functioning Rating Scale and ALSAQ-40 in the third — and none of them publishes a value from any of those instruments in the material a reader outside Russia can reach. There is no group mean, no between-group difference, no confidence interval, no measure of dispersion and no p-value to quote. Nor is there a placebo arm anywhere among them: two used an active comparator and one an add-on design, so even with numbers in hand the effect of the peptide could not be separated from the effect of time and attention. A chart built on that would be a shape with an apology underneath it. The preclinical literature, notably, is not like this at all — it reports a dissociation constant of 2.4 ± 1.0 nM and gene counts to the unit (4, 6). The gap is specific to the clinical reports as they reach a reader from here, and it is worth naming precisely rather than blaming on a language.
What a reader outside Russia actually runs into
- Language. 87 of the 207 PubMed records for Semax and 29 of the 68 for Selank are Russian-language (1). For most of those, an English abstract is the whole of what is indexed, and an abstract is written to summarise a result rather than to report one.
- Indexing. All three clinical reports are in one journal, and two of the three carry no DOI in their PubMed record — leaving a title, a page range and no route to the text (9, 11).
- Reported detail. Naming a scale is not reporting a score. All three name their scales; none publishes a number from one.
- Search terms. An unquoted search for Selank in PubMed is expanded through a supplementary concept indexed as tp 7, and returns 135 records instead of 68 and three randomised controlled trials instead of two. The extra trial is a resistance-training study with no connection to the peptide; its abstract contains the string TP: 7.7% (1, 17). Quoting the term drops it again.
- Who wrote it. Myasoedov is an author on 97 of the 207 Semax records and on 32 of the 68 Selank records (1). That concentration is ordinary for a compound's home literature, and it is still worth knowing when weighing what has been shown against who showed it.
- The register itself. The Russian State Register of Medicines runs its search as a session-based web form and could not be queried programmatically for this post. The Russian registration facts here therefore rest on a peer-reviewed paper naming the government decree, for Semax, and on a national medicines reference, for Selank (3, 16).
- Reading an empty result. A search of the openFDA drug label and Drugs@FDA endpoints returns no record for either compound, while identical queries for semaglutide return records (15). The control is what makes the empty result readable as absence rather than as a broken query — and a search that fails or is blocked, as several attempted here were, has told a reader nothing at all.
Semax and Selank side by side
No trial has compared these two compounds for any outcome. The one located human study that administered both is an imaging study in 52 healthy volunteers, and it measured connectivity rather than benefit (12). Every row below therefore describes what each peptide is, how far its published evidence has reached and how it is regulated — never how one performed against the other. There are no effect figures in this table because there is no pair of published effect figures to put in it.
| Parameter | Semax | Selank |
|---|---|---|
| Sequence | Met-Glu-His-Phe-Pro-Gly-Pro (4) | Thr-Lys-Pro-Arg-Pro-Gly-Pro (5) |
| Parent fragment | ACTH(4-10) of adrenocorticotropic hormone; described in the later literature as ACTH(4-7) with Pro-Gly-Pro added (3, 4) | Tuftsin, Thr-Lys-Pro-Arg, a natural immunopeptide (5, 7) |
| What the shared Pro-Gly-Pro is credited with | Increased resistance to peptidase activity, and the loss of the parent fragment's hormonal activity (3) | Metabolic stability and duration of action (7) |
| Pathways examined in the cited work | Specific binding in rat basal forebrain and BDNF protein levels after intranasal application (4) | GABAergic gene expression, GABA-specific binding sites and hippocampal BDNF (6, 7, 13) |
| Route in the cited rodent work | Intranasal, at 50 and 250 µg/kg (4) | Intranasal in the hippocampal BDNF work; 300 µg/kg in the frontal-cortex gene-expression work (6, 13) |
| A figure the preclinical work does publish | Dissociation constant 2.4 ± 1.0 nM for labelled Semax in rat basal forebrain (4) | 84 genes assayed in rat frontal cortex, 45 changed at 1 hour and 22 at 3 hours (6) |
| Registered as a medicine in Russia | Yes, and included in the Russian List of Vital and Essential Drugs for Medical Application by government decree (3) | Yes, as nasal drops 0.15%; marketing authorisation holder Peptogen, certificate ЛП-№(010951)-(РГ-RU) (16) |
| Marketing authorisation in the EU, the UK or the US | None (15) | None (15) |
| Records in PubMed | 207, of which 87 are Russian-language and 1 is indexed as a randomised controlled trial (1) | 68, of which 29 are Russian-language and 2 are indexed as randomised controlled trials (1) |
| Registered studies on ClinicalTrials.gov | None (2) | None (2) |
| Effect figures published on this page | None — see the note above | None — see the note above |
Sources. (1) PubMed record counts, US National Library of Medicine, retrieved through the NCBI E-utilities esearch endpoint on 10 August 2026; quoted search terms, with language and publication-type filters as stated. (2) ClinicalTrials.gov registry, US National Library of Medicine, API v2, queried 10 August 2026 for Semax and for Selank as interventions. (3) Radchenko AI, Kuzubova EV, Apostol AA, et al. The Potential of the Peptide Drug Semax and Its Derivative for Correcting Pathological Impairments in the Animal Model of Alzheimer's Disease. Acta Naturae. 2025;17(4):110–120. (4) Dolotov OV, Karpenko EA, Seredenina TS, et al. Semax, an analogue of adrenocorticotropin (4-10), binds specifically and increases levels of brain-derived neurotrophic factor protein in rat basal forebrain. J Neurochem. 2006;97 Suppl 1:82–86. (5) Vyunova TV, Andreeva L, Shevchenko K, Myasoedov N. Peptide-based Anxiolytics: The Molecular Aspects of Heptapeptide Selank Biological Activity. Protein Pept Lett. 2018;25(10):914–923. (6) 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. (7) Filatova E, Kasian A, Kolomin T, et al. GABA, Selank, and Olanzapine Affect the Expression of Genes Involved in GABAergic Neurotransmission in IMR-32 Cells. Front Pharmacol. 2017;8:89. (8) Kolomin TA, Agapova TIu, Agniullin IaV, et al. Transcriptome alteration in hippocampus under the treatment of tuftsin analog Selank. Zh Vyssh Nerv Deiat Im I P Pavlova. 2013;63(3):365–374. Published in Russian. (9) 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. Published in Russian. (10) Medvedev VE, Tereshchenko ON, Kost NV, et al. Optimization of the treatment of anxiety disorders with selank. Zh Nevrol Psikhiatr Im S S Korsakova. 2015;115(6):33–40. Published in Russian. (11) Serdiuk AV, Levitskii GN, Miasoedov NF, Skvortsova VI. The study of chronic partial denervation and quality of life in patients with motor neuron disease treated with semax. Zh Nevrol Psikhiatr Im S S Korsakova. 2007;107(4):29–39. Published in Russian. (12) 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. (13) Inozemtseva LS, Karpenko EA, Dolotov OV, et al. Intranasal administration of the peptide Selank regulates BDNF expression in the rat hippocampus in vivo. Dokl Biol Sci. 2008;421:241–243. (14) Stavchansky VV, Yuzhakov VV, Botsina AY, et al. The effect of Semax and its C-end peptide PGP on the morphology and proliferative activity of rat brain cells during experimental ischemia: a pilot study. J Mol Neurosci. 2011;45(2):177–185. (15) openFDA drug label and Drugs@FDA endpoints, US Food and Drug Administration, queried 10 August 2026: no record for Semax or Selank, while identical queries for semaglutide return records. (16) Selank, nasal drops 0.15% — registration entry, Vidal medicines reference, Russian Federation; marketing authorisation holder Peptogen, certificate ЛП-№(010951)-(РГ-RU). (17) De Souza EO, et al. Different Patterns in Muscular Strength and Hypertrophy Adaptations in Untrained Individuals Undergoing Nonperiodized and Periodized Strength Regimens. J Strength Cond Res. 2018;32(5):1238–1244 — the unrelated record returned by an unquoted Selank search. Both compounds are registered medicines in the Russian Federation and neither holds a marketing authorisation in the European Union, the United Kingdom or the United States.
Reading a literature you cannot fully reach
| Correct | Common mistake |
|---|---|
| Quote a search term exactly as it was run, in quotation marks, with the date. A record count is a measurement of a database on a day, and it should be reported as one. | Quote a count from an unquoted term. For Selank that silently adds a resistance-training trial to the tally of randomised controlled trials (1, 17). |
| Read the finding that the anxiolytic effects of both drugs were similar as what it says — a comparison against an active drug, reported without a single number (9). | Read it as equivalence to a benzodiazepine. Equivalence is a statistical claim with a margin attached, and no margin was published. |
| Name the jurisdiction every time you name a registration. Both peptides are registered in Russia, and Semax is on that country's list of vital and essential drugs by government decree (3, 16). | Write approved with no country attached. It reads as an EMA or FDA authorisation, and neither of those exists for either compound (15). |
| Treat an absent database result as absence only when an identical query for a known drug returns records (15). | Treat a failed, blocked or session-gated search as a negative finding. A page that will not load has told you nothing either way. |
| Keep the imaging study in its own category: 52 healthy volunteers, connectivity measured at 5 and 20 minutes after injection, both peptides scanned (12). | Present it as the head-to-head trial. It is the only study that gave both compounds, and it compared neither of them for benefit. |
Registration is not the same instrument as authorisation
It is worth being exact about what the Russian registration is. It is a decision by a national regulator that a product may be marketed in that country, and for Semax it goes further: the peptide is included in the Russian List of Vital and Essential Drugs for Medical Application by government decree (3). For Selank the register entry is specific down to the dosage form and the certificate number (16). These are real administrative facts, not vendor copy, and they mean something inside their jurisdiction.
What they do not carry is the thing a reader outside usually wants from the word approved: a dossier that a second regulator has examined and published its reasoning about. The European Medicines Agency and the Food and Drug Administration publish their assessments, which is why an authorisation from either doubles as a readable evidence summary. A registration whose dossier is not published hands a reader the conclusion without the working — and in this case the working is exactly what is missing from the clinical reports too.
The opposite error is just as easy to make. A literature is not worthless because it is in Russian, or because it is concentrated in one institute, or because its clinical reports are thin. Stavchansky and colleagues, Myasoedov among them, write that Semax has been employed successfully in clinical practice for treating patients with severe brain blood circulation disorders (14). That sentence is good evidence of what the originating group states, and this post records it as precisely that: a claim in the literature, made by the people who developed the compound, that no independent trial reachable from here has tested.
The useful position is the narrow one. Two peptides, one laboratory, decades of preclinical work that reports its numbers to the decimal place, three small clinical reports that report none, and a registration in one country whose reasoning no other regulator has reviewed. That is what the evidence supports, stated in full. None of it is a reason to take either of them.
Research use only
Peptio supplies Semax and Selank in 10 mg and 30 mg vials, for research use only — not for human or veterinary consumption, and not as medicines. Both are registered medicines in the Russian Federation and neither holds a marketing authorisation in the European Union, the United Kingdom or the United States; the material shipped here is a research compound and is not the registered Russian product. Peptio is not a pharmacy. Everything reported above comes from published studies and describes their animals, their cultures or their participants, and none of it is guidance for use in people.