Both Semax and Selank are sold for research purposes only. They are not approved for therapeutic use outside of limited research contexts in their country of origin.
This guide compares them clearly so researchers can determine which compound is appropriate for their specific study design.
What Is Semax?
Semax is a synthetic heptapeptide (7 amino acids: Met-Glu-His-Phe-Pro-Gly-Pro) derived from the N-terminal fragment of ACTH (adrenocorticotropic hormone). It was developed by the Institute of Molecular Genetics of the Russian Academy of Sciences and has been studied since the 1980s.
Importantly, the fragment used in Semax does not retain the adrenal-stimulating activity of full ACTH. Researchers were specifically interested in the neurotrophic and cognitive-enhancing properties of this particular sequence, separated from ACTH's endocrine effects.
How Semax Is Studied to Work
- BDNF and NGF upregulation: Semax has been shown in preclinical studies to increase expression of brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF) — proteins critical for neuronal survival, growth, and plasticity.
- Dopaminergic and serotonergic modulation: rodent studies have shown effects on dopamine and serotonin system activity in cortical and hippocampal regions.
- Neuroprotective effects: studied in models of ischaemia, oxidative stress, and traumatic brain injury, where it appeared to reduce neuronal damage.
- Cognitive performance: memory and learning task performance improvements observed in animal models, proposed to relate to its neurotrophic and monoaminergic effects.
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What Is Selank?
Selank is a synthetic heptapeptide (Thr-Lys-Pro-Arg-Pro-Gly-Pro) developed as a stable analogue of the immunomodulatory peptide tuftsin (Thr-Lys-Pro-Arg). Like Semax, it was developed by the Institute of Molecular Genetics of the Russian Academy of Sciences. Selank has been investigated primarily for anxiolytic (anti-anxiety) and immunomodulatory properties in preclinical and early clinical research.
How Selank Is Studied to Work
- GABA-A receptor modulation: Selank appears to interact with the GABA-A receptor system — the same system targeted by benzodiazepine drugs — without the sedative or dependence-inducing properties observed with benzodiazepines in animal models.
- BDNF upregulation: like Semax, Selank has been shown to increase BDNF expression, suggesting a degree of overlap in neurotrophic mechanisms.
- Enkephalin regulation: studies have shown Selank modulates enkephalin degradation, influencing endogenous opioid tone and potentially mood-related pathways.
- Immune modulation: derived from tuftsin (an immune peptide), Selank has been studied for effects on cytokine balance and T-cell activity.
- Anxiolytic effects: rodent models consistently show reduced anxiety-like behaviour without the sedation, motor impairment, or withdrawal effects seen with standard anxiolytic drugs.
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Direct Comparison
| Property | Semax | Selank |
|---|---|---|
| Origin | ACTH fragment analogue | Tuftsin analogue |
| Length | 7 amino acids | 7 amino acids |
| Primary Research Focus | Cognition, neuroprotection, BDNF upregulation | Anxiety reduction, mood, immune modulation |
| Key Receptor Interactions | Neurotrophic pathways, monoamine systems | GABA-A modulation, enkephalin pathways |
| BDNF Effects | Yes — primary mechanism | Yes — secondary mechanism |
| Anxiolytic Properties | Mild / indirect | Primary focus in research |
| Cognitive Enhancement | Primary focus in research | Secondary / indirect |
| Immune Effects | Less studied | Yes — derived from immune peptide tuftsin |
Which Is Appropriate for Your Research?
The choice between Semax and Selank depends entirely on the neurological pathways and outcomes you're investigating:
- For cognitive function, memory, neuroplasticity, and neurotrophic pathway research: Semax is the more established tool. Its BDNF-upregulating effects and cognitive performance improvements in animal models make it the primary choice for cognition-focused studies.
- For anxiety, stress response, GABA system modulation, and mood-related research: Selank is the appropriate compound. Its anxiolytic profile without sedation makes it a valuable comparator to standard benzodiazepines in experimental models.
- For research exploring combined neurotrophic and anxiolytic effects: both compounds share BDNF upregulation as a mechanism, making parallel or combination studies scientifically justifiable. Some research protocols use both together to study the sum of their neurotrophic effects.
Epithalon: Another Nootropic Peptide Worth Knowing
Researchers interested in the cognitive and neurological peptide space may also be interested in Epithalon, a tetrapeptide studied in the context of anti-ageing biology, telomerase activation, and circadian rhythm regulation.
Browse all nootropic peptides: View Nootropic Peptides Collection →
Research Use Disclaimer: All peptides sold by Apex Sequence are intended strictly for in vitro research and laboratory use only. They are not intended for human or veterinary use, consumption, or therapeutic application of any kind. These products have not been evaluated by Health Canada or the FDA for safety or efficacy in humans. By purchasing, you confirm you are a qualified researcher using products in accordance with all applicable laws.
Reviewed by the Apex Sequence editorial team • Last updated: March 2026 • Sources: PubMed / NCBI