Semax vs Selank: What the Research Literature Reports
Two heptapeptides from the same research lineage but different parent molecules — ACTH(4-10) and tuftsin — with different reported mechanisms.
Semax and Selank come from the same Russian research lineage and are often mentioned in the same breath. They are not variants of one another: they derive from different parent molecules and the published literature describes different mechanisms. This is what that literature reports.
Everything below describes published preclinical and in-vitro research. It is not a therapeutic claim, not medical advice, and not a statement about effects in humans.
Origins
Semax is a synthetic heptapeptide based on the ACTH(4-10) fragment, with a Pro-Gly-Pro tail added to slow enzymatic breakdown. ACTH(4-10) itself carries no corticotropic activity — the fragment was of interest for the effects on the nervous system that remained once the hormonal part was gone.
Selank is a synthetic heptapeptide based on tuftsin, a tetrapeptide fragment of the immunoglobulin G heavy chain, with the same Pro-Gly-Pro stabilising tail. Tuftsin’s known biology is immunological rather than neurological, which is where the two diverge at the root.
So one derives from a pituitary hormone fragment, the other from an antibody fragment. The shared tail is a stability modification, not a shared mechanism.
Reported mechanisms
Semax
- Neurotrophin expression — the most consistently reported theme, with published work describing changes in BDNF and NGF expression in the hippocampus and other regions.
- Dopaminergic and serotonergic systems — studies describe modulation of monoamine turnover.
- Neuroprotection models — a substantial part of the literature concerns ischaemia models, which is the context the compound was originally developed in.
- Attention and memory tasks — behavioural work in rodents examining acquisition and retention.
Selank
- GABAergic signalling — the dominant theme, with reported effects on GABA-A receptor expression and binding.
- Anxiolytic models — elevated plus maze and similar paradigms, where the literature frames it against benzodiazepine comparators.
- Serotonin metabolism — studies describing changes in serotonin turnover.
- Immune signalling — consistent with its tuftsin origin, some work examines interleukin expression, which has no counterpart in the Semax literature.
The practical differences
| Semax | Selank | |
|---|---|---|
| Parent molecule | ACTH(4-10) | Tuftsin (IgG fragment) |
| Length | 7 amino acids | 7 amino acids |
| Primary reported mechanism | BDNF/NGF expression | GABAergic modulation |
| Most-studied models | Ischaemia, cognition | Anxiety, immune signalling |
| Typical vial size | 5 mg | 5 mg |
Why they are often studied together
Because the reported mechanisms sit in different systems — one largely neurotrophic, the other largely GABAergic — some protocols examine them in combination. As with any combination work, the literature on the pair is considerably thinner than the literature on either alone, and the interaction is an open question rather than a settled one.
Reading this literature critically
- A large share of the published work on both compounds originates from a small number of research groups, much of it published in Russian-language journals. That is worth weighing when assessing reproducibility, and it is not a criticism unique to these two.
- Neither is an approved medicine in the European Union.
- Model systems differ substantially in route, dose and endpoint, which makes cross-study comparison difficult.
- The great majority of the work is in animal models or cell culture. Extrapolating beyond that is not supported by the data.
Handling and material quality
Both are supplied as lyophilised powder and both require reconstitution before use. Both are stable at room temperature as a powder and should be refrigerated once dissolved. Our reconstitution calculator covers the concentration arithmetic and the reconstitution guide covers the technique.
For comparative work, material quality is a real confounder: if two compounds are being evaluated against each other, a difference in purity or in actual peptide content is easily mistaken for a difference in activity. Every batch we supply is analysed by an independent laboratory for HPLC purity and mass-spectrometric identity, with batch-matched certificates available on request.
Product pages for Semax 5mg and Selank 5mg carry full molecular data, and the rest of the range is in cognitive and neuro research.
All products and information referenced are for in-vitro research and laboratory use only. Nothing here is medical advice, and no therapeutic claim is made or implied.