Semax, Selank, and Dihexa are three synthetic peptides studied for effects on the brain, but they differ in origin, mechanism, and primary use. Here is a clear, neutral comparison.
Quick answer
Semax is a peptide derived from a fragment of ACTH, studied for cognitive enhancement and neuroprotection and associated with increased BDNF. Selank comes from tuftsin and is studied mainly as an anxiolytic (anti-anxiety) peptide with secondary nootropic and immune-modulating effects. Dihexa is derived from angiotensin IV and is studied preclinically for promoting synaptogenesis (forming new neural connections) through the HGF/c-Met pathway. In short: Semax for cognition, Selank for anxiety, Dihexa for structural neuroplasticity. All three are research peptides, not mainstream FDA-approved drugs, with limited human data.
What is Semax?
Semax is a synthetic peptide based on a fragment of adrenocorticotropic hormone (ACTH), with a sequence modified to resist breakdown. Developed in Russia, it has been studied for cognitive enhancement, neuroprotection, and recovery contexts, and it is associated with increased expression of BDNF (brain-derived neurotrophic factor), a protein important for neuron health and plasticity. It is primarily a nootropic with secondary neuroprotective interest.
What is Selank?
Selank is a synthetic heptapeptide derived from tuftsin, a naturally occurring immune peptide. Also developed in Russia, Selank is studied mainly for its anxiolytic (anti-anxiety) effects, with research pointing to modulation of GABA and serotonin systems, plus some immune-modulating activity. It has milder nootropic effects as a secondary property. So while Semax leans cognitive, Selank leans calming.
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Semax
Nootropic peptide for focus, memory, and neuroprotection · From $44/mo · compounded by a licensed 503A pharmacy, dispensed only after provider review.
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Dihexa is a synthetic peptide derived from angiotensin IV, developed at Washington State University. Its proposed mechanism is distinct: rather than modulating existing neurotransmission, it is studied for promoting synaptogenesis, the physical formation of new connections between neurons, via the HGF/c-Met pathway. This focus on structural brain change sets it apart from the other two. Its evidence base is largely preclinical (animal studies).
Semax vs Selank vs Dihexa: the core differences
The three differ in origin, mechanism, and what they are primarily studied for.
- Semax: ACTH-fragment derived; cognitive enhancement and neuroprotection; linked to BDNF.
- Selank: Tuftsin derived; primarily anxiolytic with secondary nootropic and immune effects.
- Dihexa: Angiotensin IV derived; preclinical focus on synaptogenesis and structural plasticity.
Comparison table
| Feature | Semax | Selank | Dihexa |
|---|---|---|---|
| Derived from | ACTH fragment | Tuftsin | Angiotensin IV |
| Primary focus | Cognition, neuroprotection | Anxiety reduction | Synaptogenesis (structural) |
| Mechanism note | Linked to BDNF | GABA/serotonin modulation | HGF/c-Met pathway |
| Evidence | Used clinically in Russia | Used clinically in Russia | Largely preclinical |
| Status | Research peptide | Research peptide | Research peptide |
A note on evidence and status
None of these is a mainstream FDA-approved drug in the United States. Semax and Selank have been used clinically in Russia, but rigorous large-scale human trials are limited, and Dihexa's evidence is largely from animal studies. Research peptides also carry sourcing and quality concerns because they are not regulated like approved medicines. Anyone considering them should work with a qualified provider who can explain the limited evidence, monitoring, and risks.
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Frequently asked questions
What is the difference between Semax, Selank, and Dihexa? Semax targets cognition and neuroprotection, Selank targets anxiety, and Dihexa is studied for forming new neural connections. They come from different parent molecules.
Which is best for focus or cognition? Semax is the most cognition-focused of the three, associated with increased BDNF.
Which is best for anxiety? Selank is primarily anxiolytic, with research pointing to GABA and serotonin modulation.
What makes Dihexa different? Its proposed mechanism is structural: promoting synaptogenesis via the HGF/c-Met pathway, rather than modulating existing brain activity.
Are these FDA-approved? No. They are research peptides. Semax and Selank have been used clinically in Russia, but they are not mainstream FDA-approved drugs.
Can they be combined? Some discussions pair Semax and Selank for complementary cognitive and calming effects, but human evidence is limited, so any use should be medically supervised.
Is Dihexa proven in humans? Its evidence is largely preclinical (animal studies). Human data is very limited.
Are research peptides safe? Human safety data is limited and sourcing varies, so caution and medical guidance are advised.
Sources
- National Library of Medicine, Semax and cognitive/neuroprotective research: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7551997/
- National Library of Medicine, Selank anxiolytic peptide research: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4392922/
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Semax
Nootropic peptide for focus, memory, and neuroprotection · From $44/mo · compounded by a licensed 503A pharmacy, dispensed only after provider review.
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