Selank vs Semax: Two Russian Neuropeptides Compared

The table summarises what the published literature reports for each peptide. Read it as a map of what has been studied, not of what either peptide does in a person.

| Attribute | Selank | Semax | | --- | --- | --- | | Sequence | Thr-Lys-Pro-Arg-Pro-Gly-Pro | Met-Glu-His-Phe-Pro-Gly-Pro | | Built on | Tuftsin, a phagocytosis-stimulating immune peptide | ACTH(4-7), a fragment of adrenocorticotropic hormone | | Class in Russian sources | Anxiolytic | Nootropic | | Main research threads | GABA binding, anxiety models, immune genes | BDNF and TrkB, experimental stroke, cognition | | Largest human studies | Anxiety-disorder studies of 60–70 patients | Stroke studies of 30 treated patients (80 controls) and of 110 patients | | Healthy-volunteer data | One fMRI study, shared with semax | Two fMRI studies | | Work from outside Russia | None found | A few cell, chemistry and mouse studies | | ClinicalTrials.gov | No registered trial | No registered trial | | Status in Russia | Registered medicine | Registered medicine; on the vital and essential drugs list | | Status in EU / US | No EU-wide authorisation; not in Drugs@FDA | No EU-wide authorisation; not in Drugs@FDA |^{[1][2][3][5][11][15][17][16][23][25][30][31][26][27][28]}

Because they share a birthplace. Semax was synthesised at the Institute of Molecular Genetics of the Russian Academy of Sciences in Moscow under the academicians I. P. Ashmarin and N. F. Myasoedov, and selank was developed at the same institute together with the Zakusov Institute of Pharmacology.^[5][9]

They also share a design. Their developers describe both as hybrid peptides: a natural regulatory sequence joined to Pro-Gly-Pro, a tripeptide from the glyproline family that they report to be unusually stable for a regulatory peptide.^[10]

The same names recur in both literatures — Myasoedov co-authored the 1997 semax stroke study and the 2008 selank anxiety study — and the two circulate together outside the clinic too: Belgium's medicines-control laboratory identified selank and semax in two suspicious preparations encountered in 2017 and 2018.^[14][11][24]

That is roughly how Russian sources frame them: selank is listed as an anxiolytic and semax as a nootropic, and a joint brain-imaging study described them the same way.^[5][17]

The split is not clean, though. In a 1995 rat study, TP-7 — selank's early name — showed psychostimulant as well as anxiolytic activity, both more pronounced than tuftsin's. The 2008 anxiety study reported anti-asthenic and psychostimulant effects of selank alongside the anxiolytic one, and a 2014 study reported a mild nootropic effect.^[18][11][12]

Mechanisms overlap as well. Both peptides inhibit the enzymes that break down enkephalins, the body's own opioid peptides — a mechanism the developers proposed for selank's anxiolytic activity.^[1][19]

Only a few times, and only within the developers' network. In human serum in vitro, both inhibited enkephalin-degrading enzymes more potently than the peptidase inhibitor puromycin; semax reached half-maximal inhibition at 10 µM and selank at 20 µM.^[1]

In rats with 6-OHDA lesions that model Parkinson's disease, neither peptide changed motor activity or passive defensive behaviour, while selank lowered anxiety measures in the elevated plus maze.^[20]

In 52 healthy volunteers, resting-state fMRI after selank, semax or placebo showed shared and peptide-specific changes in connectivity between the right amygdala, a key region for anxiety, and the right temporal cortex. The abstract reports no measure of anxiety, memory or attention.^[17]

None of these shows which peptide is stronger in people, and ClinicalTrials.gov lists no trial of either.^[30][31]

BDNF, a growth factor for nerve cells, is central to the semax literature. In rats, a single application raised hippocampal BDNF protein at most 1.4-fold and phosphorylation of its TrkB receptor 1.6-fold; in a Russian study of 110 stroke patients, plasma BDNF rose in the semax subgroups.^[4][15]

For selank, the BDNF record is thin and points elsewhere. A 2008 rat paper reported that selank regulates hippocampal BDNF expression but has no abstract showing in which direction, and in rats given alcohol for 30 weeks, selank prevented the ethanol-induced rise in BDNF rather than raising it.^[21][22]

So 'both boost BDNF' overstates the case: the semax effect is modest and comes from rats, and the selank data we could check show no rise.^[4][22]

Thin for both. Selank's main human data are three small Russian-language studies in anxiety disorders — 62, 60 and 70 patients, compared with or added to the benzodiazepines medazepam and phenazepam — whose English abstracts do not describe blinding.^[11][12][13]

Semax's main human data are Russian stroke studies — 30 treated patients against 80 conventionally treated controls in 1997, and 110 patients in rehabilitation in 2018 — plus two resting-state fMRI studies in healthy volunteers that measured brain networks rather than cognition.^{[14][15][16][17]}

The clearer difference is who else has looked. Every selank experiment we found on PubMed comes from Russian institutions; the few records by authors elsewhere are reviews or a forensic analysis. Semax has drawn a handful of outside laboratories: an Italian group studied its copper binding and protection of cultured cells, and a Chinese group reported better functional recovery after spinal cord injury in female mice.^{[23][24][3][25]}

In Russia, yes. A 2022 review counts 14 peptide products registered in the Russian Federation, including semax as a nootropic drug and selank as an anxiolytic, and a 2025 paper notes that semax is on the Russian government's list of vital and essential drugs.^[5][26]

Outside Russia, no. Neither appears in the European Commission's Union Register of centrally authorised medicines for human use or in Drugs@FDA, the US database of approved drugs (both checked September 2026).^[27][28]

The FDA's page on bulk substances that may present significant safety risks in compounding lists selank acetate and semax among substances once in category 2 whose nominations were withdrawn. The entries note a possible immunogenicity risk from aggregation and peptide-related impurities, and missing information on safety in humans.^[29]

The literature, not the reputation, is the guide. Selank's published models concern anxiety-related behaviour, GABA-receptor binding and immune-gene expression; semax's concern BDNF/TrkB signalling and ischaemic brain injury. A project outside those areas starts with little prior data for either.^[6][7][4][8]

Peptyds supplies both as lyophilised research peptides in sealed vials, each with a batch-traceable certificate of analysis, for laboratory research only — not for human or veterinary use. We do not present either as a treatment for anxiety, cognition or stroke.