Key takeaways
- Semax is derived from the hormone ACTH and is studied mainly for neurotrophic and cognitive effects, especially BDNF.
- Selank is derived from the immune peptide tuftsin and is studied mainly in stress and anxiety research.
- Both share a Pro-Gly-Pro tail that protects them from rapid breakdown, and both come from the Institute of Molecular Genetics in Moscow.
In this guide
Browse cognitive research →At a glance
| Semax | Selank | |
|---|---|---|
| Sequence | Met-Glu-His-Phe-Pro-Gly-Pro | Thr-Lys-Pro-Arg-Pro-Gly-Pro |
| Length | 7 amino acids | 7 amino acids |
| Parent molecule | ACTH(4-10), from adrenocorticotropic hormone | Tuftsin, an immunoglobulin G fragment |
| Main research focus | BDNF, neuroplasticity, cognition, brain ischaemia models | Stress response, anxiety-related behaviour, monoamines, immune signalling |
| Shared feature | Pro-Gly-Pro tail for stability; both inhibit enkephalin-degrading enzymes in vitro | |
| Regulatory status | Prescription medicine in Russia; not approved in Canada or the US | Not approved in Canada or the US |
Shared origins
Both peptides were developed at the Institute of Molecular Genetics of the Russian Academy of Sciences. The researchers used the same design strategy for each: take a short, biologically active fragment of a natural peptide and attach a Pro-Gly-Pro tripeptide to the end. That tail makes the molecule more resistant to the enzymes that would otherwise break it down within minutes.
Semax: from a hormone fragment
Semax is a synthetic analogue of ACTH(4-10), a fragment of adrenocorticotropic hormone. It joins the ACTH(4-7) sequence (Met-Glu-His-Phe) to the Pro-Gly-Pro tail. This keeps the neuroactive properties associated with ACTH fragments without the full hormone's effect on the adrenal glands. Semax was first described in the scientific literature in 1991.
Much of the research centres on neurotrophic signalling. In rats, Semax was reported to increase levels of brain-derived neurotrophic factor (BDNF) and its receptor TrkB in the hippocampus, a region central to memory (Dolotov et al., Brain Research, 2006). BDNF supports neuron survival and synaptic plasticity, which is why Semax is studied in learning, memory and brain ischaemia models.
Selank: from an immune peptide
Selank is a synthetic analogue of tuftsin, a four-amino-acid peptide (Thr-Lys-Pro-Arg) that occurs naturally as a fragment of immunoglobulin G and plays a role in immune function. Adding the Pro-Gly-Pro tail gives Selank its stability.
Research on Selank spans the nervous and immune systems. Animal studies have reported changes in brain monoamine neurotransmitters such as serotonin and dopamine, changes in the expression of genes involved in GABAergic signalling (Volkova et al., Frontiers in Pharmacology, 2016), and regulation of BDNF expression in the hippocampus. Because of its tuftsin origin, it's also studied for effects on cytokines and immune-cell responses.
Where they overlap
Despite their different parents, the two peptides share at least one well-documented property: both were found to inhibit enkephalin-degrading enzymes in human serum (Kost et al., Russian Journal of Bioorganic Chemistry, 2001). Enkephalins are the body's own opioid peptides, and slowing their breakdown is one proposed contributor to the effects seen in stress models. Both have also been linked to BDNF in animal research.
The key differences, in short
- Origin: Semax comes from a hormone (ACTH); Selank from an immune peptide (tuftsin).
- Research emphasis: Semax leans towards cognition and neuroprotection; Selank towards stress, anxiety-related behaviour and immunomodulation.
- Regulatory history: Semax is used as a prescription medicine in Russia. Neither is approved in Canada or the United States.
Related compound: Adamax is a modified Semax analogue, also studied in neurotrophic and cognitive signalling research.
Frequently asked questions
What is the difference between Semax and Selank?
Semax is derived from the hormone ACTH and is studied mainly for neurotrophic and cognitive effects. Selank is derived from the immune peptide tuftsin and is studied mainly in stress and anxiety research. Both share a stabilizing Pro-Gly-Pro tail.
Who developed Semax and Selank?
Both were developed at the Institute of Molecular Genetics of the Russian Academy of Sciences.
Are Semax and Selank approved in Canada?
No. Neither is approved in Canada or the United States. Semax is used as a prescription medicine in Russia.
What does the Pro-Gly-Pro tail do?
It protects the peptide from rapid enzymatic breakdown, extending how long it remains intact compared with the natural fragment it's based on.
References
- Dolotov OV, 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.
- Kost NV, et al. Semax and Selank inhibit the enkephalin-degrading enzymes from human serum. Russ J Bioorg Chem. 2001;27(3):180–183.
- Volkova A, et al. Selank administration affects the expression of some genes involved in GABAergic neurotransmission. Front Pharmacol. 2016;7:31.
