Selank vs Semax: Two Heptapeptides from the Same Moscow Lab
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Selank and Semax are usually mentioned in the same breath, and for once the pairing is justified by history rather than marketing: both are seven-amino-acid peptides developed at the Institute of Molecular Genetics in Moscow, both end in the same stabilising Pro-Gly-Pro tail, and both became registered medicines in Russia while remaining research compounds everywhere else. This page compares their origins, mechanisms and published evidence from a laboratory research perspective. Nothing here is medical advice.
What are Selank and Semax?
Selank is a synthetic analogue of tuftsin, a natural immunomodulatory tetrapeptide fragment of immunoglobulin G, extended with the Pro-Gly-Pro sequence for metabolic stability. The published literature examines it mainly in anxiety-related behaviour and immune signalling.
Semax is a synthetic analogue of the ACTH(4-10) fragment of adrenocorticotropic hormone, with the same Pro-Gly-Pro stabiliser and, critically, without the hormonal activity of full-length ACTH. Its literature centres on neurotrophin biology, where it has been reported to raise BDNF and NGF expression in preclinical models.
How do their mechanisms differ?
The two peptides took the same structural trick, a protease-resistant tail on a natural fragment, in two different biological directions. Selank’s reported activity runs through GABAergic modulation and immune-related gene expression: a 2018 review of its molecular pharmacology describes allosteric effects on GABA-A signalling and enkephalinase inhibition, and gene-expression studies in animal models have reported shifts in inflammation-related transcripts in spleen tissue. Semax’s reported activity runs through the neurotrophin axis: increased BDNF and NGF expression, with downstream effects studied in models of ischaemia and cognitive load. In short, the published mechanisms place Selank on the anxiety-immunity side and Semax on the neuroplasticity side of the same peptide family.
What does the published evidence show?
Both compounds carry a body of Russian-language clinical literature connected to their registration there, and a smaller international preclinical literature. A 2024 comparative study reported antidepressant-like and antistress effects for both peptides in rodent models, one of the few papers to test them side by side. The reading caution for both is the same one our evidence ranking applies across the catalog: much of the mechanistic work comes from laboratories connected to the originating institute, and independent replication outside that circle remains the scarcest resource. Neither compound has EU or US clinical trial programmes.
| Selank | Semax | |
|---|---|---|
| Parent structure | Tuftsin (IgG fragment) + PGP | ACTH(4-10) fragment + PGP |
| Reported mechanism focus | GABAergic modulation, immune gene expression | BDNF and NGF expression |
| Research literature | Anxiety models, immune signalling | Neuroprotection, cognitive models |
| Registered medicine | In Russia; not EU or US | In Russia; not EU or US |
Which research applications does each suit?
For laboratory models, the split follows the mechanisms. Selank is the tool for anxiety-behaviour paradigms, GABA-adjacent pharmacology and peptide immunomodulation questions. Semax is the tool for neurotrophin induction studies, ischaemia models and work on activity-dependent plasticity. Because the two share the Pro-Gly-Pro stabilisation strategy, they also serve as mutual controls in studies asking whether an effect belongs to the stabilising tail or to the active fragment, a design that appears repeatedly in the originating institute’s publications.
What is the regulatory status?
Both peptides are registered medicines in Russia, typically as nasal formulations. Neither has marketing authorisation in the EU or the US, and research material supplied under a research use only framework is not those medicinal products, is not a medicine, and is not for human or veterinary use. Neither compound is currently named on the WADA Prohibited List; the live list is the binding reference for athletes.
Research sourcing and quality checks
Both compounds are available in our catalog as research reagents: Selank and Semax. Where a batch has been tested, its report is published in the lab reports archive and linked from the product page. Because both peptides share the same C-terminal tail, identity confirmation by mass spectrometry is the meaningful check between them; what to look for on the certificate is covered in our guide on reading a certificate of analysis.
Conclusion
Same institute, same stabilising tail, two different branches of biology: Selank toward anxiety and immune signalling, Semax toward neurotrophins. Their shared limitation is the shape of their evidence, deep in origin-country literature and thin in independent replication, which is exactly the property a research buyer should weigh. As laboratory tools they are complementary rather than interchangeable, and the published literature of each should drive the choice.
References
- Peptide-based Anxiolytics: The Molecular Aspects of Heptapeptide Selank Biological Activity. 2018. PubMed
- Antidepressant-like and antistress effects of the ACTH(4-10) synthetic analogs Semax and Melanotan II. 2024. PubMed
- Expression of inflammation-related genes in mouse spleen under tuftsin analog Selank. 2011. PubMed