Two Peptides, Shared Origin
Selank and Semax both emerged from the Russian regulatory peptide research programme at the Institute of Molecular Genetics (IMG) of the Russian Academy of Sciences. Unlike most western research peptides — which are typically receptor ligands designed to mimic or block a specific endogenous signal — the Russian regulatory peptide approach takes short functional sequences from larger endogenous proteins, then extends the C-terminus with a stabilising Pro-Gly-Pro (PGP) tripeptide to resist enzymatic degradation.
This design philosophy produces peptides that retain a fragment of the parent molecule's biological activity but with extended plasma stability and, crucially, intranasal bioavailability — the route used in most published Russian clinical and preclinical work.
Selank (TP-7) is derived from tuftsin, an immunomodulatory tetrapeptide that fragments naturally from the IgG Fc region. Semax is derived from ACTH(4-10), the heptapeptide fragment of adrenocorticotropic hormone that carries the central neurotropic activity of the parent molecule but lacks its corticotropic effect. Both share the same Pro-Gly-Pro C-terminal modification.
Selank: Structure and Mechanism
Selank (Thr-Lys-Pro-Arg-Pro-Gly-Pro) is a seven amino acid synthetic analogue of tuftsin (Thr-Lys-Pro-Arg) with a C-terminal PGP extension. The N-terminal tuftsin sequence retains tuftsin's immunomodulatory and anxiolytic properties; the PGP extension blocks aminopeptidase degradation and extends plasma half-life from minutes to a research-useful window.
The primary mechanism characterised in Russian preclinical research is modulation of the GABAergic system — Selank appears to enhance GABA-A receptor signalling and increase brain enkephalin levels. Published research has also documented effects on serotonin turnover, dopamine release in specific limbic regions, and modulation of pro- and anti-inflammatory cytokine expression. Clinical research conducted in Russia investigated Selank for generalised anxiety, with reported anxiolytic effects comparable to benzodiazepines but without sedation, dependence, or cognitive blunting.
Standard research applications include anxiolytic models, immunomodulation studies, and exploration of GABA-system-derived nootropic mechanisms. Selank does not appear to exert direct effects on BDNF or NGF expression — that is Semax's territory.
Semax: Structure and Mechanism
Semax (Met-Glu-His-Phe-Pro-Gly-Pro) is a seven amino acid analogue of ACTH(4-10), the central fragment of adrenocorticotropic hormone responsible for the parent molecule's neurotropic activity. The same Pro-Gly-Pro C-terminal extension stabilises the peptide against enzymatic degradation. Critically, Semax lacks the N-terminal sequence of full ACTH that drives cortisol release — so the compound provides ACTH(4-10)'s CNS effects without activating the HPA axis.
The most robust mechanistic finding for Semax is dose-dependent upregulation of brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF) expression, particularly in hippocampal tissue. Additional documented mechanisms include modulation of the brain melanocortin (MC4R) pathway, enhancement of cholinergic neurotransmission, and antioxidant effects via increased Cu/Zn-SOD activity.
Russian clinical research has investigated Semax in ischaemic stroke recovery, optic neuropathy, cognitive impairment, and ADHD models. The peptide is on the Russian List of Vital and Essential Medicines as a registered treatment for cerebrovascular conditions — research-grade Semax remains a distinct compound from any pharmaceutical preparation.
Head-to-Head Comparison
| Property | Selank | Semax |
|---|---|---|
| Parent molecule | Tuftsin (immunomodulator from IgG Fc) | ACTH(4-10) (neurotropic fragment) |
| Sequence | Thr-Lys-Pro-Arg-Pro-Gly-Pro | Met-Glu-His-Phe-Pro-Gly-Pro |
| Length | 7 amino acids | 7 amino acids |
| Primary mechanism | GABA-system modulation; cytokine balance; enkephalin upregulation | BDNF/NGF upregulation; melanocortin pathway; cholinergic enhancement |
| Primary research focus | Anxiolytic models; immunomodulation; stress response | Cognitive enhancement; neuroprotection; cerebrovascular research |
| HPA axis activation | No | No (despite ACTH origin) |
| Sedation profile | Anxiolytic without sedation | Mildly stimulating in cognitive models |
| Russian regulatory status | Registered for anxiety (Russia only) | On Russian Vital & Essential Medicines List for cerebrovascular indications |
Combined Use in Research Protocols
The two peptides are frequently studied together because their mechanisms are complementary rather than overlapping. Semax provides the cognitive/neurotrophic stimulation arm — pushing BDNF and NGF expression upward — while Selank provides the anxiolytic/GABA-modulation arm. The combination allows researchers to model nootropic effects without the over-stimulation that BDNF upregulation alone can produce in stress-sensitive cognitive tasks.
This combination is most commonly reported in Russian-language preclinical work and in researcher-led protocols outside Russia. There is no published clinical trial of the combination at this time, so the rationale remains mechanistic rather than evidence-based at clinical scale.
For researchers studying either compound individually, see the standalone Selank research guide and Semax research guide.
Research-Grade Sourcing in Australia
RetaLABS supplies both compounds as 10mg lyophilised vials, with manufacturer Certificates of Analysis available on request. Both peptides are stable at -20°C as lyophilised powder for long-term storage. Once reconstituted with bacteriostatic water, refrigerate at 2–8°C and use within 28 days.
Reconstitution and aliquoting follow the standard low-volume protocol used for other research peptides — see the reconstitution and storage guide for technique notes. Selank and Semax are research compounds; they are not TGA-approved therapeutic goods and are not for human or animal consumption.
Available products: Selank 10mg · Semax 10mg